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Tektronix 11801C User Manual

Digital sampling oscilloscope
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Table of Contents

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User Manual
11801C
Digital Sampling Oscilloscope
070-9971-01
This document supports firmware version 4.05
and above.

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Summary of Contents for Tektronix 11801C

  • Page 1 User Manual 11801C Digital Sampling Oscilloscope 070-9971-01 This document supports firmware version 4.05 and above.
  • Page 2 Copyright E Tektronix, Inc. All rights reserved. Tektronix products are covered by U.S. and foreign patents, issued and pending. Information in this publication supercedes that in all previously published material. Specifications and price change privileges reserved. Printed in the U.S.A.
  • Page 3 Tektronix, with shipping charges prepaid. Tektronix shall pay for the return of the product to Customer if the shipment is to a location within the country in which the Tektronix service center is located. Customer shall be responsible for paying all shipping charges, duties, taxes, and any other charges for products returned to any other locations.
  • Page 5 Low Voltage Directive 73/23/EEC: EN 61010-1 Safety requirements for electrical equipment for measurement, control, and laboratory use Tektronix, Inc. claims compliance to the EMC Directive 89/336/EEC for the following products when they are used with the above named product: SD-20 SD-22...
  • Page 6 AS/NZS 2064.1/2 Industrial, Scientific, and Medical Equipment: 1992 Tektronix, Inc. claims conformity to the standards for the following products when they are used with the above named product:...

  • Page 7: About This Manual

    Documentation The CSA 803C and 11801C Programmer Reference describes using a computer to control the 11801C through GPIB or RS 232 C interfaces. The 11801C Service Manual provides module level repair and replace ment information about the 11801C. It also describes cleaning and preventative maintenance procedures.

  • Page 8: Contacting Tektronix

    For product support outside of North America, contact your local Tektronix distributor or sales office. Service Contact your local Tektronix distributor or sales office. Or, visit our web Support site for a listing of worldwide service locations. http://www.tek.com For other...

  • Page 9: Table Of Contents

    ........11801C User Manual...
  • Page 10 Table of Contents Pop Up Menus ......... . . Autoset .
  • Page 11 ..........3 41 11801C User Manual...
  • Page 12 Table of Contents Display Persistence ......... 3 43 Setting the Persistence Mode .
  • Page 13 ........3 180 Sequencing Through Stored Settings ..... . 3 181 11801C User Manual...
  • Page 14 Table of Contents Stored Traces ..........3 183 Storing Traces .
  • Page 15 ............11801C User Manual...
  • Page 16 Table of Contents Contents...
  • Page 17 2 51 Figure 2 33: The Measure Major Menu ......2 53 11801C User Manual...
  • Page 18 List of Figures Figure 2 34: The Measurements Pop Up Menu ....2 54 Figure 2 35: Measurements of a Trace ......2 55 Figure 2 36: The RMS Pop Up Menu and Annotation Lines .
  • Page 19 ..3 120 Figure 3 61: The Mask Testing Pop up Menu ....3 122 xiii 11801C User Manual...
  • Page 20 List of Figures Figure 3 62: Editing a Mask ........3 123 Figure 3 63: Creating a User Mask .
  • Page 21 ........3 231 Figure 3 114: The Horizontal Desc Pop up Menu ....3 232 11801C User Manual...
  • Page 22 List of Figures Contents...
  • Page 23 ....Table B 3: 11801C Input and Output Specifications ....
  • Page 24 List of Tables xviii Contents...

  • Page 25: Safety Summary

    Do Not Operate in Wet/Damp Conditions. Do Not Operate in an Explosive Atmosphere. Keep Product Surfaces Clean and Dry. Provide Proper Ventilation. Refer to the manual’s installation instructions for details on installing the product so it has proper ventilation. 11801C User Manual...
  • Page 26 Safety Summary Symbols and Terms Terms in this Manual. These terms may appear in this manual: WARNING. Warning statements identify conditions or practices that could result in injury or loss of life. CAUTION. Caution statements identify conditions or practices that could result in damage to this product or other property.
  • Page 27 Introduction This section describes the safety precautions, power and signal connec tions, and procedures you should follow when you install the 11801C. It then provides a high level view of the 11801C Digital Sampling Oscilloscope and its features. 11801C Description The 11801C Digital Sampling Oscilloscope provides unprecedented capabil ities in capturing and accurately measuring high speed electrical events.

  • Page 28: Getting Started

    11801C. It disables invalid selections and indicates to the operator which choices are logical at any time. Programmable control of the 11801C that allows it to be run from an attached computer or instrument controller via the RS 232 C or GPIB interfaces.

  • Page 29: Description Of Sampling

    Thus, as higher bandwidth sampling heads are introduced, you can increase the capability of the 11801C just by adding a new sampling head. The 11801C Digital Sampling Oscilloscope uses sequential sampling to sample one data point of the trace each time a trigger event occurs (up to 200K samples per second).
  • Page 30 Never apply a voltage outside the range printed on the front of the sampling head. Operate the 11801C only in a static controlled environment. Connect the wrist strap provided with the 11801C to the ANTISTATIC CON NECTION, as shown in Figure 1 1.

  • Page 31: Figure 1 1: Front Panel Connectors

    Figure 1 1: Front Panel Connectors Rear Panel The POWER plug provides AC power to the 11801C. The plug is an IEC style connector; the separate power cord supplied with the 11801C should match the physical configuration of electrical outlets in your country.

  • Page 32: Figure 1 2: Rear Panel Power Connectors And Switches

    Figure 1 2: Rear Panel Power Connectors and Switches The PRINTER connector provides a Centronics style interface, so you can connect a printer to the 11801C. This lets you make a paper copy of the display by pressing the HARDCOPY button on the front panel.

  • Page 33: Installation

    POWER connector compartments. to your power system. Step 8: Step 7: Set the front panel Set the PRINCIPAL ON/STANDBY POWER SWITCH to SWITCH to ON. Once the 11801C is installed, use the ON/STANDBY switch as a power switch. 11801C User Manual...

  • Page 34: Operating Environment

    Introduction Operating The following environmental requirements are provided so that you can ensure proper functioning and extend the operation of the instrument. Environment Operating Temperature The instrument can be operated where the ambient air temperature is be tween 0_ C and +50_ C and can be stored in ambient temperatures from -40_ C to +75_ C.

  • Page 35: At A Glance

    See page 3 19. The PRESCALE and DIRECT touch icons. Using the knobs inputs let you connect an external signal for is described on page 1 13. triggering traces. See page 3 215. 11801C User Manual...

  • Page 36: Rear Panel

    Centronics interface. See page 3 89. If your 11801C is equipped with Option 1M, the SM 11 connectors let you attach up to four SM 11 Multi Channel Units, which provide more sampling head compartments.

  • Page 37: Display And Touch Panel

    See page 1 14 for a the knob labels to see the Keypad Menu, which description of the various major menus. lets you enter a numeric value for any knob controlled parameter. See page 1 13. 1 11 11801C User Manual...

  • Page 38: Icons

    At a Glance Icons Touch the horizontal icon to assign the knobs to adjust the trace horizontal size and position. See page 3 105. Def Tra Touch the Define Trace icon to display a pop up menu that lets you define a new trace to be displayed.

  • Page 39: Knobs, Knob Menu, And Keypad Menu

    3 107. When the knobs are assigned to selector. A pop up menu will ask you to select vertical size and offset, this selector may change remove or clear. See page 3 212. to provide more vertical control. See page 3 221. 1 13 11801C User Manual...

  • Page 40: Major Menu Buttons

    At a Glance Major Menu Buttons The Waveform major menu controls trace definition, acquisition, and the sampling heads. See page 1 16. An alternate form of the Waveform major menu, the Trace Status menu, can be displayed using the More... selector in the Waveform major menu.
  • Page 41 See page 1 28. The Cursors major menu controls the cursors, markers that you position on your trace to make measurements. Use the Cursors icon to display the Cursors major menu. See page 3 29. 1 15 11801C User Manual...

  • Page 42: Waveform Major Menu

    At a Glance Waveform Major Menu This pop up menu lets you modify the trace expression of the selected trace. See page 3 211. The More... selector displays the alternate Trace Status major menu. This displays the status of all traces on the display. See page 3 210.
  • Page 43 Horizontal reference point controls. See page 3 109. XY trace controls. See page 3 231. Averaging and Acquisition control. enveloping. See page 3 3. See page 3 13. Graticule and axis unit controls. See page 3 83. 1 17 11801C User Manual...
  • Page 44 At a Glance Saved trace description controls. See page 3 173. 1 18 Getting Started...

  • Page 45: Trigger Major Menu

    Select Normal or Auto Touch this selector to Trigger with this selector. enable/disable enhanced See page 3 215. triggering. See page 3 215. Touch this selector to change the trigger slope. See page 3 215. 1 19 11801C User Manual...

  • Page 46: Measure Major Menu

    At a Glance Measure Major Menu Use this pop up menu to specify which measurements you want to take. As you select measurements, the readouts appear immediately in the unused selectors of the major menu. See page 3 139. Touch a measurement readout to display a pop up menu that lets you control the way the measurement is taken.

  • Page 47: Display Modes Major Menu

    See page 3 117. See page 3 43. This menu show the density values of the color graded display. See page 3 45. Use this menu to select predefined telecommunication masks for mask testing See page 3 117. 1 21 11801C User Manual...

  • Page 48: Store/Recall Major Menu

    At a Glance Store/Recall Major Menu These pop up menus let you store and recall displayed traces. See page 3 183. This selector activates or disables the SEQUENCE SETTINGS button on the front panel. You can use that button to change from one instrument setting to the next.
  • Page 49 Delete stored traces using this pop up menu. See page 3 186. Clear displayed traces using this pop up menu. See page 3 5. These pop up menus let you recall or delete settings. See page 3 179. 1 23 11801C User Manual...

  • Page 50: Utility1 Major Menu

    At a Glance Utility1 Major Menu This pop up menu shows instrument and sampling head identification and firmware version numbers. See page 3 189. Use this pop up menu to set GPIB and RS 232 C parameters. See page 3 80 for GPIB, and page 3 164 for RS 232 C. Use this selector to initialize the instrument to a known state.
  • Page 51 See page D 6. Touch this selector to turn Use these controls to on or off time and date set the instrument stamps for stored traces. clock. See page 3 203. See page 3 183. 1 25 11801C User Manual...

  • Page 52: Enhanced Accuracy Major Menu

    At a Glance Enhanced Accuracy Major Menu Calibrate blowby compensation of the sampling heads that use this calibration. See page 3 49. Calibrate gain of sampling heads. See page 3 49. This pop up menu controls the automatic self calibration system. This pop up menu provides assistance in making all See page 3 49.
  • Page 53 See page 3 49. Use this selector to access the Utility2 major menu. See page 1 28. Calibrate the TDR amplitude of those sampling heads that support TDR. See page 3 49. 1 27 11801C User Manual...

  • Page 54: Utility2 Major Menu

    At a Glance Utility2 Major Menu Use this selector to initiate a self test and verify that the Use this selector to enter the instrument is operating extended diagnostics system. properly. See page 3 38. See page 3 38. Use this selector to return to the Utility1 major menu.

  • Page 55: Overview

    Examples 8 through 11 discuss advanced features of your 11801C Digital Sampling Oscilloscope that are beyond the standard set of oscilloscope features. These examples cover using a stored trace as a reference, saving trace descriptions for later use, taking histograms of displayed trace data, and taking Time Domain Reflectometry (TDR) measurements.
  • Page 56 Overview Operating Basics...

  • Page 57: Example 1: Displaying A Trace

    This example shows how quickly you can display a meaningful trace on the display. You will also become familiar with the basic front panel controls. For this example you will need an 11801C with at least one sampling head installed, one SMA connecting cable, and a static protection wrist strap.

  • Page 58: Figure 2 1: Utility1 Major Menu

    Press the same button a second time to display the second page of the menu. Initialize the 11801C to default settings using the Initialize selector, which appears in the Utility1 major menu. Step 1: Press the major menu UTILITY button, located in the MENUS column.

  • Page 59: The Touch Panel

    The Touch Panel You make selections from menus by touching the appropriate area. Until you remove your finger from the display, the 11801C indicates your potential selection by outlining that selector. You can change your potential selection by dragging your finger to the desired selector before withdrawing it.

  • Page 60: Connecting Cables

    Example 1: Displaying a Trace Connecting Cables To view the calibrator signal, you must connect a cable from the CALIBRA TOR output to any sampling head input connector. Step 4: Connect an SMA cable from the CALIBRATOR output to either input connector of any installed sampling head (see Figures 2 3 and 2 4).

  • Page 61: Figure 2 4: Sampling Head Control Panel (Sd 24 Shown)

    ( ) at the left of the graticule shows !not! above it meaning the 11801C is not triggered. This icon always shows you the trigger status. The 11801C has an internal clock, which is synchronized with the calibrator output.

  • Page 62: Pop Up Menus

    Example 1: Displaying a Trace Pop Up Menus Touching the Source selector demonstrates a common operation of selec tors: they display pop up menus. These menus are a temporary dialog with you; they cover a portion of the graticule. Most pop up menus disappear automatically when you make a selection.

  • Page 63: Autoset

    AUTOSET Button Figure 2 6: AUTOSET Button Location Step 10: Press the AUTOSET button above the sampling heads. You will see rising edge of the calibrator signal on the display. 11801C User Manual...

  • Page 64: Autoset Options

    Example 1: Displaying a Trace Autoset Options You have used autoset to show the rising edge of the calibrator signal. The Instrument Options pop up menu of the Utility1 major menu controls auto set operation (see Figure 2 7). Figure 2 7: The Instrument Options Pop Up Menu Step 11: Press the UTILITY major menu button in the MENUS column and touch the Instrument Options selector in the major menu.

  • Page 65: Figure 2 8: The Calibrator Signal After Pressing Autoset In

    Standard mask autoset is discussed in the Mask Testing section, beginning on page 3 117. The Undo Last Autoset selector restores the 11801C to the settings that existed before you pressed the AUTOSET button. You want to display several cycles of the calibrator signal.

  • Page 66: The Knobs

    Always glance at the knob labels before using the knobs. When you turn the knobs, you will feel clicks instead of smooth motion. Each click represents a minimum change; the 11801C counts clicks" to measure knob motion. Depending on the value the knobs are assigned to, each click changes the value by some linear increment, a multiplicative factor, or the next number in a 1 2 5 sequence.

  • Page 67: Icons

    Knob menu labels. Turning the knobs shows that the vertical characteris tics of the trace are altered. Step 14: Touch the icon and turn each knob left and right. Observe the changes in the trace. 2 13 11801C User Manual...

  • Page 68: Figure 2 10: Icons

    Example 1: Displaying a Trace Magnitude Horizontal Cursors Window Define Trace Vertical Trigger Figure 2 10: Icons 2 14 Operating Basics...

  • Page 69: Keypad Pop Up Menu And Knob Resolution

    5 0 m. Notice the entry line being formed above the Numeric Entry label in the pop up menu. Use Back Space to remove incorrect entries. Touch Enter to complete entry. Vertical size is now set to 50 mV per division. 2 15 11801C User Manual...

  • Page 70: Figure 2 11: The Knob Menu And Keypad Pop Up Menu

    Example 1: Displaying a Trace Figure 2 11: The Knob Menu and Keypad Pop Up Menu 2 16 Operating Basics...

  • Page 71: Major Menu Knob Assignments

    Major menu buttons perform knob assignments. Step 19: Press the WAVEFORM major menu button in the MENUS column. The knob assignment changes to Main Size and Main Pos, because that was the last assignment made using the Waveform major menu. 2 17 11801C User Manual...
  • Page 72 Example 1: Displaying a Trace 2 18 Operating Basics...

  • Page 73: Figure 2 12: Connections For Example 2

    This example demonstrates multiple traces and graticules on the display. It also shows how to select and manage multiple traces. For this example you will need an 11801C with at least one sampling head installed, two SMA cables, and a static protection wrist strap.

  • Page 74: Example 2: Managing Multiple Traces

    Example 2: Managing Multiple Traces Step 8: Press the UTILITY button to display the Utility major menu. Touch the Instrument Options selector in the major menu area, and select Autoset Mode in the pop up menu to select Period as the auto set mode.

  • Page 75: Adding Another Trace

    The horizontal axis labels apply to both traces. This may not hold true for the vertical axis. While the 11801C can display up to 8 traces at once, there is always one selected trace. The selected appears brighter than other traces. Most menu selectors, the knobs, the status displays, and autoset all operate on the selected trace.

  • Page 76: Selecting Traces By Touch

    The number n in the Remove/Clr Trace n selector is the trace number assigned by the 11801C when the trace is created. It should not be con fused with the trace expression. Trace numbers range from 1 through 8. This selector always shows the number of the selected trace.

  • Page 77: Selecting Traces Using The Trace Status Menu

    Step 16: Return to the normal Waveform major menu, either by touch ing the Return to Single Trace selector in the major menu or by press ing the WAVEFORM major menu button in the MENUS column. 2 23 11801C User Manual...

  • Page 78: Labeling Traces

    Example 2: Managing Multiple Traces Labeling Traces You can label traces to help you keep track of them. You can specify a label of up to 10 characters for each trace, and you can have these labels dis played with the traces on the graticule. You can use letters of the alphabet (upper or lower case), Greek symbols, graphic symbols or numbers in your label.

  • Page 79: Figure 2 17: The Labeling Pop Up Menu

    Example 2: Managing Multiple Traces Figure 2 17: The Labeling Pop Up Menu 2 25 11801C User Manual...

  • Page 80: Displaying Dual Graticules

    Example 2: Managing Multiple Traces Displaying Dual The Graticules selector can create a dual graticule display (see Figure 2 19). You can place traces on either graticule. Graticules Step 26: Press the WAVEFORM button to display the Waveform major menu. Step 27: Touch the Graticules selector in the major menu, and touch Create Second Graticule in the pop up menu (see Figure 2 18).

  • Page 81: Figure 2 19: A Dual Graticule Display

    Example 2: Managing Multiple Traces Figure 2 19: A Dual Graticule Display 2 27 11801C User Manual...

  • Page 82: Removing Traces

    Example 2: Managing Multiple Traces Removing Traces Step 30: Below the knob labels, touch the Remove/Clr Trace n selec tor, and then Remove Trace n in the pop up menu. This will remove one of your traces, leaving one on the display. You could remove the remaining trace with Remove/Clr Trace n again.

  • Page 83: Figure 2 20: Connections For Example 3

    This example shows how you can create traces that combine signals from more than one channel. For this example you will need a 11801C with at least one dual channel sampling head installed. Also, a power divider and two SMA cables of different length will be used (2 ns and 5 ns cables are recommended).

  • Page 84: Example 3: Defining Complex Traces

    Example 3: Defining Complex Traces Step 7: Turn the top knob to the left until the horizontal scale is 5 ns/div. Don't use the AUTOSET button! You should see the calibrator trace on the display twice. Because of the different lengths of the cables you are using, the edges of these traces will be separated by 3 ns.

  • Page 85: Trace Expressions

    Step 9: Touch Mainframe, then 1 (under Mainframe in the numeric keypad area), - Mainframe, 2 (under Mainframe in the numeric key pad area), and Enter Desc, all in the pop up menu. 2 31 11801C User Manual...

  • Page 86: Figure 2 21: The Deftra Pop Up Menu

    Example 3: Defining Complex Traces The difference trace is created. Notice that on the sampling heads, both of the yellow lights for the source channels are blinking, indicating that both channels are represented in the selected trace. Figure 2 21: The DefTra Pop Up Menu 2 32 Operating Basics...

  • Page 87: Vertical Adjustment Of Complex Traces

    (High Precision traces don't have this limitation.) Step 15: Turn the top knob to the left to return the selected trace to its original size of 200 mV/div. 2 33 11801C User Manual...

  • Page 88: Figure 2 22: Complex Trace Aberration Caused By Off Graticule

    Example 3: Defining Complex Traces Aberration Figure 2 22: Complex Trace Aberration Caused by Off Graticule Component In the last few steps, you have moved the complex trace by selecting and moving one of the component traces. Since you have the component traces on the display this is easy to do.
  • Page 89 Step 19: Turn the top knob to the right to set the vertical size to 100 mV/div. You may need to turn the bottom knob to position the trace completely on the graticule. Now the input channel traces and the complex difference trace are double their original size. 2 35 11801C User Manual...

  • Page 90: High Precision Traces

    Example 3: Defining Complex Traces High Precision If your complex trace is a high precision trace, you can move it vertically using the knobs without changing the offset of any component channel. Traces High precision traces are calculated using floating point arithmetic. The complex trace you have created and moved in this example is not a high precision trace;...

  • Page 91: Windows

    Step 21: Touch the Window icon. Figure 2 24: A Window Trace Display The 11801C automatically added a second graticule with the window trace. The main trace was placed on the top graticule, and its highlighted portion shows what the window trace is displaying (see Figure 2 24).

  • Page 92: Figure 2 25: The Chan Sel Selector In The Knob Menu

    Example 3: Defining Complex Traces Step 22: Touch the WAVEFORM button and then touch the More... selector in the major menu. The original trace is on the Main time base, while the currently selected window trace is on a window time base. Step 23: Touch the horizontal icon ( ), and turn the bottom Window Pos knob left and right.

  • Page 93: Horizontal Reference Point

    Turn the top knob left one click at a time. Observe that the critical center part of the trace remains stationary. Note that the L next to the horizontal icon changes to C to remind you that the reference point is the center of the screen. 2 39 11801C User Manual...
  • Page 94 Example 3: Defining Complex Traces 2 40 Operating Basics...

  • Page 95: Figure 2 26: Connections For Example 4

    The amount of noise you see in this example will depend on the sampling head you have installed. For this example you will need an 11801C with at least one sampling head installed, one SMA cable, and one static protection wrist strap.

  • Page 96: Example 4: Using Signal Processing

    Example 4: Using Signal Processing Step 6: Turn the top knob to the right until the horizontal scale is 1 ps/ div. By turning off horizontal autoset, you can use the AUTOSET button to display a portion of the trace at this horizontal setting. Step 7: Press UTILITY and touch Instrument Options.

  • Page 97: Averaging And Enveloping

    Adjust the top knob to change the average count. Each time you click the knob, a new average begins. If you wish the 11801C to stop acquiring data after the required number of samples, you can use the Average Complete selector in the section Stop Acquisition On.

  • Page 98: Figure 2 28: The Acquire Desc Pop Up Menu

    Example 4: Using Signal Processing Figure 2 28: The Acquire Desc Pop Up Menu Figure 2 29: Averaged and Normal Traces 2 44 Operating Basics...
  • Page 99 Both averaging and enveloping can be done simultaneously. To do both, you must enter the trace expression from the DefTra or Vertical Desc pop up menus. No shortcut is available from the Acquire Desc pop up menu. 2 45 11801C User Manual...

  • Page 100: Variable Persistence

    Example 4: Using Signal Processing Variable Persistence Another method of observing trace noise is using variable persistence, available through the Display Modes major menu. This leaves earlier trace data on the display for a specified period of time as new data values are added, building a recent history of displayed trace points.
  • Page 101 Select Exit to remove the pop up menu. Step 17: Select Persist/Histograms again and select Normal to return to the normal trace display. Select Exit to remove the pop up menu. 2 47 11801C User Manual...

  • Page 102: Smoothing

    Example 4: Using Signal Processing Smoothing Some sampling heads, including the SD 24, provide another way to reduce apparent noise. To access it, you use the Sampling Head Fnc's selector in the Waveform major menu. Step 18: Press the WAVEFORM button in the MENUS column and touch Sampling Head Fnc's in the major menu.

  • Page 103: Record Length

    NOTE If the channel loop gain is not correctly calibrated, changing record lengths can also change the trace appearance. See Enhanced Accuracy in the Reference section of this manual. 2 49 11801C User Manual...
  • Page 104 Example 4: Using Signal Processing The bottom knob similarly controls the window record lengths. You should be aware of the following attributes of record lengths: All main time base traces share the same record length. All window traces share the same record length. Initialize sets both record lengths to 512.

  • Page 105: Figure 2 32: Connections For Example 5

    This example demonstrates how quickly you can display a dynamic mea surement from a displayed trace. For this example you will need a 11801C with at least one sampling head installed, one SMA cable, and a static protection wrist strap.

  • Page 106: Example 5: Taking Automated Measurements

    Example 5: Taking Automated Measurements Step 7: Press the AUTOSET button. You should have a stable display of the calibrator signal showing several cycles. It is important that all of the signal is on the display and that there are no places where the trace extends above or below the graticule area.

  • Page 107: Specifying Measurements

    Six of the selectors are reserved for your measure ment readouts. The Measurements selector brings up a pop up menu to let you choose which measurements you want (see Figure 2 34). 2 53 11801C User Manual...

  • Page 108: Figure 2 34: The Measurements Pop Up Menu

    Example 5: Taking Automated Measurements Figure 2 34: The Measurements Pop Up Menu Step 9: Touch the Measurements selector. The Amplitude, Timing, and AreaEnergy sections of this pop up menu show all the various measurements that you may specify. Touch the selec tors in these areas to turn each measurement on and off.

  • Page 109: Figure 2 35: Measurements Of A Trace

    Example 5: Taking Automated Measurements Figure 2 35: Measurements of a Trace 2 55 11801C User Manual...

  • Page 110: Measurement Parameters And Annotations

    Example 5: Taking Automated Measurements Measurement For each measurement, more information is available and more control is provided. Touching the measurement selector in the major menu area does Parameters and the following: Annotations Displays annotation lines on the graticule. These annotation lines graphi cally show the portions of the trace that the measurement readout value is based on.

  • Page 111: Figure 2 36: The Rms Pop Up Menu And Annotation Lines

    When you used the limit bar to exclude the portion of the trace where the measurement was being taken, the 11801C took the measurement at the next opportunity on the trace. This is shown by the highlighted portion of the trace moving to the right.

  • Page 112: Default Measurement Parameters

    Example 5: Taking Automated Measurements Default Measurement Left and right limits are examples of measurement parameters. Measure ment parameters are settings that you change to control the measurement Parameters system. Most parameters are shared by all the measurements being taken on any one trace.

  • Page 113: Figure 2 37: The Default Parameters Pop Up Menu

    The right limit of the measurement is now set to 80%. This change did not occur until you touched the Initialize All selector. Had you been displaying other traces, their parameters would have been unaffected by either the change to the defaults or by the Initialize All. 2 59 11801C User Manual...

  • Page 114: Measurement Modes

    In hardware mode, measurements are taken from the analog signal output from the sampling head before it is digitized and assembled into a trace record. The 11801C uses special timer circuits to take hardware measurements. The advantage of hardware mea surements is that they are performed faster than software measurements.

  • Page 115: Table 2 1: Measurement Mode Comparison

    Speed Slower Faster Updated when color graded data base is updated (selectable be tween 5 and 100 seconds) or when a measurement parameter changes, such as mesial level. 2 61 11801C User Manual...

  • Page 116: Figure 2 38: The Hardware Measurements Pop Up Menu

    Example 5: Taking Automated Measurements Figure 2 38: The Hardware Measurements Pop Up Menu You have now converted all your measurements on this trace to hardware measurements. Since hardware measurements cannot support amplitude or area energy measurements, these do not appear in the pop up menu, and the RMS measurement has been removed from the major menu area.

  • Page 117: Figure 2 39: A Jitter Measurement On The Calibrator Signal

    Color Grading is enabled. This capability enables you to make automatic pulse parametric measurements directly on random data such as eye diagrams. See Figure 2 39. Figure 2 39: A Jitter Measurement on the Calibrator Signal 2 63 11801C User Manual...
  • Page 118 Example 5: Taking Automated Measurements 2 64 Operating Basics...

  • Page 119: Figure 2 40: Connections For Example 6

    You will use the cursors to take two common measurements, trace ampli tude and delay between traces. The 11801C can do both of these as auto mated measurements, so you can compare the method of using automated measurements to using cursors.

  • Page 120: Example 6: Taking Delay Measurements Using Cursors

    Example 6: Taking Delay Measurements Using Cursors Step 7: Turn the top knob to the left to set the horizontal scale to 10 ns/ div. You should see the calibrator signal on the display. The Cursors Major First you will use the cursors to determine the amplitude of the calibrator signal.

  • Page 121: Figure 2 41: The Cursors Major Menu And Cursor Type Pop Up Menu

    Keypad pop up menu. Setting the resolution of one knob changes the resolution of both. The major menu area shows the voltage values of each cursor, and DV shows the distance between the cursors in volts. This is the amplitude of the calibrator signal. 2 67 11801C User Manual...

  • Page 122: Figure 2 42: Horizontal Bar Cursors Placed Over A Trace

    Example 6: Taking Delay Measurements Using Cursors Figure 2 42: Horizontal Bar Cursors Placed Over a Trace The same value can be determined using the automated measurement system. The sequence to do this is: press the MEASURE button, touch Measurements in the major menu area and then the Peak Peak selector in the pop up menu.

  • Page 123: Using Split Dot Cursors

    Step 15: Touch the Cursors icon and the Cursor Type selector. Touch the Split Dots selector. Figure 2 43: The Cursor Type Pop Up Menu in Split Dots Mode 2 69 11801C User Manual...
  • Page 124 Example 6: Taking Delay Measurements Using Cursors When you first select split dots cursors, both dots are on the selected trace. The Cursor Type pop up menu remains on the display until you select the trace you want to move the other cursor to. See Figure 2 43. Beneath the selectors that allow cursor choice, a second set of selectors lists all of the traces currently on the display.

  • Page 125: Cursor Accuracy Considerations

    Setting one cursor knob to fine will also set the other. When using cursors or software measurements, always make the area to be measured as large as possible, and cover as much of the graticule area as you can. This will give the finest resolution. 2 71 11801C User Manual...
  • Page 126 Example 6: Taking Delay Measurements Using Cursors 2 72 Operating Basics...

  • Page 127: Figure 2 44: Connections For Example 7

    For this example you will need a 11801C with at least one sampling head installed, two SMA cables of different length (2 ns and 5 ns cables are recommended), and a static protection wrist strap.

  • Page 128: Example 7: Taking Comparison Measurements Using A Reference Trace

    Example 7: Taking Comparison Measurements Using a Reference Trace You will measure the difference in propagation time down the two cables which are different lengths. The cross measurement, which shows the time delay from the trigger to the rising edge of a signal, will be the basis of your comparison.
  • Page 129 Propagation Velocity selector and adjust this parameter. If you don't know the velocity or are using Tektronix polyethylene dielectric SMA cables, accept the 0.7 default. Step 12: Press the MEASURE button to redisplay the Cross measure ment.

  • Page 130: Using The Reference Value

    Example 7: Taking Comparison Measurements Using a Reference Trace Using the Reference You will use this measurement value as a reference value. The Compare & References pop up menu allows you to save this value and cause all mea Value surements to be displayed as a difference from this value.
  • Page 131 Example 7: Taking Comparison Measurements Using a Reference Trace Once the 11801C has been set up with a comparison measurement, no further adjustment is necessary to make a series of deviation measure ments. To compare the longer cable to the reference you have established: Step 15: Remove the short cable from the calibrator and sampling head, and replace it with the longer cable connected in the same way.
  • Page 132 Example 7: Taking Comparison Measurements Using a Reference Trace 2 78 Operating Basics...
  • Page 133 For this example you will need an 11801C with at least one dual channel sampling head installed. Also, a power divider and two SMA cables of different length will be used (2 ns and 5 ns cables are recommended).

  • Page 134: Example 8: Using Saved Trace Descriptions

    Example 8: Using Saved Trace Descriptions Power Divider Short Cable Long Cable Figure 2 47: Connections for Example 8 Step 5: Press the TRIGGER button, touch Source and Internal Clock. Step 6: Press the SELECT CHANNEL button on the sampling head input channel to which you have connected the long cable.

  • Page 135: Figure 2 48: The Save Trace Desc Pop Up Menu

    When you save the trace description, you are not saving data points as when you store a trace. Instead the 11801C saves all the parameters to create that trace when needed. Just as with a visible trace on the display, the data of a saved trace description will change with the input signal.
  • Page 136 Example 8: Using Saved Trace Descriptions Saved trace descriptions do not save the size and position of traces on the main time base, or window size of traces on a window time base. When the saved trace description is recalled, these parameters are set to match the current time bases.
  • Page 137 This time, the entire trace will be saved as a reference. For this example you will need a 11801C with at least one sampling head installed and one SMA connecting cable. Step 1: Initialize the 11801C (press the UTILITY button in the MENUS column, touch Initialize in the major menu, and touch Initialize in the verification pop up menu).

  • Page 138: Example 9: Comparing Traces To Stored Traces

    Step 8: Press the STORE/RECALL button, then touch Store Trace and select Trace 1 in the Store Trace pop up menu. The 11801C has stored a trace in memory, named STO 1". Once the trace is stored, there is no reason to leave its source on the display.
  • Page 139 RMS measurement: Step 13: Press the MEASURE button and touch Measurements, RMS, and Exit. To tune a circuit, you could make adjustments to get the smallest RMS measurement instead of simply trying for the flattest" trace. 2 85 11801C User Manual...
  • Page 140 Example 9: Comparing Traces to Stored Traces 2 86 Operating Basics...
  • Page 141 (time per division) and vertical (volts per division) settings to simulate a noisy signal. For this example you will need a 11801C with at least one dual channel sampling head installed, one SMA cable, and a static protection wrist strap.

  • Page 142: Example 10: Creating A Histogram Display

    Example 10: Creating a Histrogram Display In Example 4, you used color grading to view the relative density of trace points in a display of this signal. A histogram will provide additional statisti cal information about the distribution of points in the trace. Step 9: Press the DISPLAY MODES button and select Persist/Histo grams in the major menu area.
  • Page 143 Figure 2 52: A Vertical Histogram Display You can adjust the histogram limits to restrict the range of trace record points that the 11801C will recognize as valid data points. Step 11: Touch Persist/Histograms to redisplay the pop up menu.
  • Page 144 Example 10: Creating a Histrogram Display You can also control the number of samples the 11801C uses to develop the histogram. Using the Persist/Histograms pop up menu, you can set a number of waveforms (traces) or a number of samples (individual trace record points, or hits") to acquire for the histogram before stopping acquisi...

  • Page 145: Example 11: Taking Tdr Measurements

    For this example you will need a 11801C with at least one SD 24 sampling head installed. You will also need one SMA cable, preferably of 5 ns length, and a static protection wrist strap.

  • Page 146: Figure 2 54: The Sampling Head Fnc's Pop Up Menu

    Example 11: Taking TDR Measurements Figure 2 54: The Sampling Head Fnc's Pop Up Menu Step 6: Adjust the display sizes and positions to show a trace similar to that shown in Figure 2 55. The vertical ( ) and horizontal ( ) icons will let you make fine adjustments.

  • Page 147: Figure 2 55: Tdr Step And Reflection

    Example 11: Taking TDR Measurements Figure 2 55: TDR Step and Reflection 2 93 11801C User Manual...

  • Page 148: Changing Graticule Units For Tdr

    Units for TDR measurement commonly used in TDR. When you selected TDR Preset, the 11801C automatically changed the units of the vertical axis to units of rho (r). You can change the measure ment units for both graticule axes by using the Graticules selector in the Waveform major menu.

  • Page 149: Measuring Distance With Tdr

    Example 11: Taking TDR Measurements Measuring Distance One of the common uses of TDR is measuring distance. The 11801C makes it easy to measure the length of a cable or circuit board run by using the with TDR Cursors major menu. Distance is determined by the measuring the time required for a pulse to travel down a transmission line (for example, a cable or circuit board run) and for its reflection to return.
  • Page 150 Example 11: Taking TDR Measurements 2 96 Operating Basics...

  • Page 151: Acquisition

    Acquired trigger signal is independent of the signal being acquired. See Figure 3 1. When the trigger event is detected, the 11801C waits a specified period of time before sampling and digitizing the first trace point. This time period is the horizontal position of the trace, which is set using the knobs.

  • Page 152: Determining The Sample Interval

    All traces on the main time base have the same record length and horizontal size. Similarly, all traces on window time bases share the same record length and horizontal size. This means that the 11801C uses one sample interval for main traces and a different sample interval for window traces.

  • Page 153: Controlling Acquisition

    Avg and Env. If you select One Record, all waveforms will be reacquired and acquisition will stop after a new, complete acquisition has been made for each waveform. When you wish to resume normal, continuous acquisition, touch the Contin uous selector under the heading Run Acquisition. 11801C User Manual...

  • Page 154: Figure 3 3: The Acquire Desc Pop Up Menu

    Acquisition Figure 3 3: The Acquire Desc Pop up Menu Reference...

  • Page 155: Clearing Traces

    You may notice that the trace blinks as it is cleared and replaced. The Remove/Clr pop up menu can also be used to clear the selected trace. Figure 3 4: The Clear Trace Pop up Menu 11801C User Manual...
  • Page 156 Acquisition Reference...

  • Page 157: Audio Feedback

    Utility1 major menu. Touch the Audio Feedback selector in this pop up menu to turn the beep off or on. See Figure 3 5. Audio Feedback Selector Figure 3 5: The Instrument Options Pop up Menu 11801C User Manual...
  • Page 158 Audio Feedback Reference...

  • Page 159: Autoset

    Autoset Adjusting an oscilloscope to display a stable trace of usable size and ampli tude can be a time consuming process. The Autoset feature of the 11801C can quickly give you a stable, meaningful trace display. The AUTOSET Button Figure 3 6: Front Panel Autoset Button...

  • Page 160: Undoing An Autoset

    If you don't like the results of an autoset, you can restore the status of the 11801C by touching the Undo Last Autoset selector in the Instrument Options pop up menu of the Utility1 major menu. See Figure 3 7.
  • Page 161 Manual. You can turn off the trigger parameter adjustments during standard mask autoset from the Instrument Options pop up menu. Setting Trigger Autoset to Off causes the 11801C to leave trigger parameters unchanged during a standard mask autoset.
  • Page 162 Autoset Setting the Stan Mask Offset Adj selector to On causes the instrument to adjust the vertical offset during a standard mask autoset to make the wave form match the selected standard mask more closely. Setting this selector to Off turns off vertical offset adjustments during a standard mask autoset. This feature only applies to 19 of the standard masks.

  • Page 163: Averaging And Enveloping

    Averaging reduces the apparent noise of a displayed trace and provides a cleaner display. The 11801C presents a trace that is an average of several accumulated trace records. Each sample in a record is numeri cally averaged with the same sample in all the other records. The result ing trace is displayed.

  • Page 164: Defining An Averaged Or Enveloped Trace

    Averaging and Enveloping Defining an Averaged There are two ways of establishing an averaged or enveloped trace. or Enveloped Trace 1. If you are establishing a new trace, you can use the AVG( or ENV( trace functions as you define your trace. These can be selected from the Def Tra menu.

  • Page 165: Terminating Averaging Or Enveloping

    Record Count Several complete trace records are combined to form an averaged or envel oped trace. You can set the number of records that the 11801C accumulates and combines. Use the Set Avg N and Set Env N selectors in the Acquire Desc pop up menu to assign the knobs to set the number of records.

  • Page 166: Limiting Acquisition

    Averaging and Enveloping Limiting Acquisition You can have the 11801C stop acquiring trace data when enough data is accumulated to determine a complete average or envelope. This has the effect of freezing the trace. The selectors in the Stop Acquisition On section of the Acquire Description pop up menu let you specify One Record, Aver age Complete, Envelope Complete, or Both Avg &...

  • Page 167: Baseline Correction

    Step 1: Turn baseline correction off. Step 2: Put on the wrist strap and ensure that it is connected to the antistatic connector on the front panel of the 11801C. Step 3: Using an SD 24 sampling head, establish a TDR display of a short, unterminated cable.
  • Page 168 Baseline Correction 3 18 Reference...

  • Page 169: Calibrator

    Step 4: Select the internal clock trigger source (press the TRIGGER button, touch the Source selector in the major menu, and touch the Internal Clock selector in the pop up menu). Step 5: Press the AUTOSET button. 3 19 11801C User Manual...
  • Page 170 Calibrator 3 20 Reference...

  • Page 171: Color Display

    To change the color of a display element, select the element in the Color pop up menu. The knobs are automatically assigned to control Lightness and Saturation; select Hue if you want to adjust the hue of the color. Adjust the color using the control knobs. 3 21 11801C User Manual...

  • Page 172: Restoring Colors

    Color Display Figure 3 10: The Color Pop up Menu Restoring Colors Two selectors in the Color pop up menu let you restore colors to their default settings or to the colors previously defined. Previous Colors restores all eight display elements to the colors they had when you displayed the Color pop up menu.

  • Page 173: Reassigning Trace Colors

    You can adjust the overall intensity, or brightness, of the display. Touch the Display Intensity selector in the Color pop up menu to assign the knobs to Intensity control the intensity of the display. Display intensity can be from 0% to 100%. 3 23 11801C User Manual...
  • Page 174 Color Display 3 24 Reference...

  • Page 175: Constellation Diagrams

    Initialize in the Verify Initialize pop up menu. Step 2: Put on the wrist strap and ensure that it is connected to the antistatic connector on the front panel of the 11801C. Step 3: Connect a cable from signal source 1 (often called the I"...

  • Page 176: Figure 3 11: Adjusting The Main Position

    Figure 3 11: Adjusting the Main Position Step 10: To set the 11801C for this condition, create a normal YT wave form on each of the two channels. Adjust the horizontal size and posi tion to expand a small section of the waveform horizontally and to fill most of the screen vertically.

  • Page 177: Figure 3 12: How The Expanded Waveforms Should Appear

    To select the correct channel, go back to the Horizontal Desc pop up menu and select the other (non highlighted) channel in the XY display mode section of the pop up menu. See Fig ure 3 13. 3 27 11801C User Manual...

  • Page 178: Figure 3 13: The Display After Selecting The Xy Display Mode

    Constellation Diagrams Figure 3 13: The Display After Selecting the XY Display Mode Step 16: The channel 2 trace should now appear as a constellation diagram and the channel 1 trace should remain unchanged. Now, delete the channel 1 trace (touch the other signal display and use the Remove/ Clr pop up menu) and adjust the constellation diagram to fill the screen.

  • Page 179: Cursors

    You can use cursors to take several measurements. However, the auto mated measurement system is easier, faster, and more accurate. You can take many common measurements using the Measure major menu. See Measurements on page 3 135 for more information. 3 29 11801C User Manual...

  • Page 180: Cursor Operation

    NOTE Establish all trace displays before turning on the cursors. When you touch the Cursors icon, the 11801C displays the cursors and their readouts. Whenever you touch the Cursors icon, the knobs are as signed to adjust cursor positions.

  • Page 181: Figure 3 15: The Set Zero Pop Up Menu

    At the top of the Cursor Type pop up menu, you can select from four cursor types. If you select Vertical Bars, Horizontal Bars, or Paired Dots, the 11801C removes the pop up menu and shows the selected cursors. The knobs control the cursor positions.
  • Page 182 Cursors Once you have positioned the cursors, select Proceed. The 11801C will calculate a constant (RHOZERO) to be saved with the selected trace. The RHOZERO constant is added to the rho position (RHOPOS) for the selected trace. Every time RHOPOS is recalculated for the selected trace (for exam ple, by baseline correction) RHOZERO will be added to RHOPOS again.

  • Page 183: Cursor Examples

    Step 5: The cursors are now placed, one on each trace. Use the knobs to move the cursors to the two locations from which you want to mea sure time difference. Then read the time difference (Dt) at the bottom of the display. 3 33 11801C User Manual...
  • Page 184 Cursors 3 34 Reference...

  • Page 185: Diagnostics

    The 11801C features a diagnostic system that performs comprehensive tests of the instrument. This ensures you that your instrument is operating correctly. A set of tests is automatically performed whenever the 11801C is powered on. You can execute additional diagnostic tests at any time.

  • Page 186: Power On Diagnostics

    Diagnostics Power On The 11801C executes the power on diagnostics whenever you turn the power on; this is the only time these tests are executed. The power on Diagnostics diagnostics test the most fundamental operations of the microprocessors and the communication paths between microprocessors.

  • Page 187: Self Test Diagnostics

    Diagnostics Self Test Diagnostics The 11801C automatically executes the self test diagnostics after the power on diagnostics are completed successfully. The self test diagnostics can also be initiated by touching the Self Test selector, located in the Utility2 major menu (press the UTILITY button until the Utility2 menu appears), and then touching Self Test in the verification pop up menu.

  • Page 188: Extended Diagnostics

    Diagnostics Extended You can enter the extended diagnostic system by touching the Extended Diagnostic selector, located in the Utility2 major menu (press the UTILITY Diagnostics button until the Utility2 menu appears), and then touching Extended Diag nostic in the verification pop up menu. When self test diagnostics fail, the extended diagnostic system is entered automatically.
  • Page 189 When the extended diagnostic tests are complete, the (r) Run selector is displayed again, and the test status appears in the INDEX and FAULT columns. When you are done with the extended diagnostic tests, touch the (e) Exit selector twice in succession. 3 39 11801C User Manual...
  • Page 190 Diagnostics 3 40 Reference...

  • Page 191: Display Intensity

    Display intensity can also be changed in the Color pop up menu, or in the Persist/Histograms pop up menu in the Display Modes major menu. The Display Intensity Selector Figure 3 19: The Instrument Options Pop up Menu 3 41 11801C User Manual...
  • Page 192 Display Intensity 3 42 Reference...

  • Page 193: Display Persistence

    The persistence mode is selected from the Persist/Histograms pop up menu. To display the Persist/Histograms menu, press the DISPLAY MODES button and then touch Persist/Histograms. See Figure 3 20. Figure 3 20: The Persist/Histograms Pop up Menu 3 43 11801C User Manual...

  • Page 194: Setting The Persistence Mode

    In normal mode, each record replaces its predecessor record by erasing it from the screen. Variable In variable persistence mode, the 11801C accumulates waveform data on the screen for a user specified period and then automatically removes them from the screen after the time has expired or aged.

  • Page 195: Table 3 1: A Sample Assignment Of Colors To Hit Density

    Grad Scale in the Display Modes major menu. The Color Grad Scale pop up menu shows the hit density for each of the five waveform colors. The hit density readouts are updated when the 11801C updates the color graded display.

  • Page 196: Figure 3 21: The Color Grad Scale Pop Up Menu

    Display Persistence Figure 3 21: The Color Grad Scale Pop up Menu Changing Colors There are five colors used in the color graded display. The colors can be changed, from the Color pop up menu in the Utility1 major menu. The colors are mapped to the four trace colors and the window trace color.
  • Page 197 Step 1: Set the number of overflows used to limit acquisition by touch ing Set N MaxContrast and using the knobs Step 2: Begin the acquisition by touching Stop N MaxContrast If you want to stop the acquisition while still acquiring data, press RUN/ STOP . 3 47 11801C User Manual...
  • Page 198 Display Persistence 3 48 Reference...

  • Page 199: Enhanced Accuracy

    Enhanced Accuracy The Enhanced Accuracy menu allows you to control the continuous self cal ibration features of the 11801C. It also allows you to perform some user as sisted calibration procedures on the sampling heads. You do not need tools to make these calibrations;...

  • Page 200: Control Of Automated Calibration

    This maintains the accuracy of the delay adjust ment calibrations you have performed earlier. You can specify whether or not you want the 11801C to perform this automatic compensation. Touch the Delay Compensate selector in the Delay Adjust pop up menu to set this parameter to either On or Off.

  • Page 201: Calibration Assistance

    Assistance channel at once. The 11801C prompts you to make the signal connections that are needed to calibrate automatically. See Figure 3 23. Figure 3 23: The Calibrate All Pop up Menu You should first decide which sampling head channel you want to use as the reference channel for delay adjust.
  • Page 202 2. Another message prompts you to connect a 50 W terminator to the selected channel and touch the Proceed selector. The 11801C automat ically calibrates offset. 3. If the sampling head supports TDR, a final message prompts you to connect a 50 W terminator to the selected channel and touch the Pro ceed selector.

  • Page 203: Sampling Head Calibrations

    TDR amplitude. The Reference Amplitude (in the Graticules pop up menu) is used in rho mode and should be set to match the voltage calibrated here (nominally 250 mV). Note that some sampling heads are not equipped to perform this calibration. 3 53 11801C User Manual...
  • Page 204 Enhanced Accuracy Delay Adjust lets you deskew different sampling heads to any one sampling head. The reference head you choose is measured, and the delay of the other sampling heads is adjusted to match that reference head. Calibrate delay adjust only when you need to measure delays between two sampling heads to close tolerance.

  • Page 205: Figure 3 24: A Typical Calibration Pop Up Menu

    Recall User Const selector in the pop up menu. When the 11801C is powered on, the sampling head calibration values are taken from the stored user constants. It is a good idea to store calibration values immediately after you finish each calibration.
  • Page 206 The Divide By Two Mode selector turns the trigger divide by two mode on or off. Normal operation of the 11801C internal clock requires that this selector be set to Off. Set it to On only when calibrating loop gain. This calibration does not apply to the SD 14 sampling head.

  • Page 207: Figure 3 25: Loop Gain Calibration (In Vectored Trace Mode)

    If possible, you should also set the trigger hold off to the same value that will be used in test. If you do not provide a trigger, the 11801C will automatically use the internal clock as a trigger.
  • Page 208 Enhanced Accuracy pop up menu, touch 0 and Enter. This sets the vertical offset to zero, posi tioning 0 V at the center height of the graticule. This calibration does not apply to the SD 14 sampling head. NOTE You should calibrate gain before calibrating offset. Adjust the calibration value to set the trace exactly on the centerline of the graticule.
  • Page 209 You can specify whether or not the 11801C should automatically maintain the results of delay adjust. Touch the Delay Compensate selector of the...

  • Page 210: Offset For Sampling Probes

    Enhanced Accuracy Offset for Sampling Sampling probes such as the SD 14 use an automated offset adjustment that sets both both offset null and offset gain. Probes The offset null adjustment removes unwanted DC offset that may be present in the sampling probe. This adjustment effectively zeroes the offset circuitry in the sampling probe so that a 0 V input signal delivers a 0 V output.

  • Page 211: Eye Diagrams

    Step 3: Put on the wrist strap and ensure that it is connected to the antistatic connector on the front panel of the 11801C. Step 4: Connect a cable from your data line to channel 1. Step 5: Connect a cable from your clock to the TRIGGER INPUT on the front panel.

  • Page 212: Figure 3 26: An Eye Diagram Display

    Eye Diagrams NOTE Correct gain calibration is critical to see an eye pattern properly. Eye Diagram Analysis can be reliably performed on signals up to 400 mV peak to peak in amplitude. Signals larger than 400 mV in amplitude should be attenuated to achieve reliable results in Eye Diagram Analysis.
  • Page 213 Eye Diagrams Step 11: One of the most powerful display modes in the 11801C is color grading. Color grading adds statistical information to the display by varying the color according to the number of hits" for a given pixel. Color grading adds a third dimension to the persistence display and allows accumulating data in a statistical database for later analysis with histograms or masks.
  • Page 214 Eye Diagrams 3 64 Reference...

  • Page 215: Fast Fourier Transforms

    Fast Fourier Transforms You can use the Fast Fourier Transform (FFT) capability of the 11801C to obtain a frequency domain display of a trace. You can display both the magnitude and the phase of the frequency components of the signal, using a linear or decibel vertical scale.

  • Page 216: Defining An Fft Trace

    Fast Fourier Transforms Defining an FFT You can define an FFT display of a trace using the DefTra pop up menu or you can use the FFTmag and FFTpha icons. Trace Defining an FFT Display Using the DefTra Pop up Menu You can define a trace that displays the FFT magnitude or FFT phase using the DefTra pop up men, which is displayed when you select the DefTra icon.

  • Page 217: Figure 3 28: Location Of The Fftmag Icon On The Display

    Icons You can display the magnitude of the frequency spectrum of a displayed trace by selecting the trace and touching the FFTmag icon. The 11801C creates a second graticule to display the FFT magnitude of the trace. If the display already shows two graticules, the FFT magnitude is displayed on the lower graticule.

  • Page 218: Amplitude Resolution

    Frequency Range The range and resolution of the frequency spectrum displayed by the 11801C are determined by the sample interval and record length of the time and Resolution domain trace. The sample interval is displayed in the Horizontal Desc pop up menu (in the Waveform major menu) and is determined by the time base and record length.

  • Page 219: Changing Horizontal And Vertical Size

    When you touch the vertical icon ( ), the knobs are assigned to control Vertical Mag: Tra and Vertical Pos: Tra, the vertical magnitude and position of the trace. As with other calculated traces, the vertical controls of the FFT trace affect only the appearance of the trace. 3 69 11801C User Manual...

  • Page 220: Fft Scaling

    Fast Fourier Transforms FFT Scaling The FFT magnitude display may be scaled in either a linear or decibel format. To set the vertical scaling of the FFT magnitude display, select the FFT Scaling selector in the Instrument Options pop up menu, in the Utility major menu.

  • Page 221: Aliasing

    1,)). Another way to decrease aliasing is to select an appropriate FFT windowing function. The 11801C provides six common FFT windowing functions, which are accessible from the Instrument Options pop up menu. Touch the FFT Window selector to sequence through the six functions.

  • Page 222: Using Cursors To Make Measurements

    Fast Fourier Transforms Using Cursors to You can use the cursors to make measurements of an FFT trace display. Select the FFT trace and touch the Cursors icon to display the Cursors Make Measurements major menu. See Cursors on page 3 29 for more information on using cursors.

  • Page 223: Figure 3 32: Using Split Dots Cursors To Measure Fft Phase

    FFT phase display. By adjusting the cursors horizontally so that the Df readout is 0.000 Hz, you can easily match the phase readout to the corre sponding peak in frequency magnitude. See Figure 3 32. Figure 3 32: Using Split Dots Cursors to Measure FFT Phase 3 73 11801C User Manual...

  • Page 224: Fft Windowing Functions

    Fast Fourier Transforms FFT Windowing The Fast Fourier Transform operates on the time domain trace record ac quired by the 11801C. The FFT algorithm assumes that the signal is com Functions posed of an infinite repetition of this trace record.

  • Page 225: Figure 3 33: Fft Magnitude Displayed Using Rectangular Window

    Set the FFT Window selector in the Instrument Options pop up menu to Triangle to select this windowing function. See Figure 3 34. Time Window 0 dB Frequency Filter Figure 3 34: FFT Magnitude Displayed Using Triangular Window 3 75 11801C User Manual...

  • Page 226: Figure 3 35: Fft Magnitude Displayed Using Blackman Window

    Fast Fourier Transforms The Blackman Window The Blackman window reduces leakage better than the Hamming window because of the lower side lobes in the frequency domain, but the resolution of nearby frequencies is diminished. Set the FFT Window selector in the Instrument Options pop up menu to Blackman to select this windowing function.

  • Page 227: Figure 3 36: Fft Magnitude Displayed Using Blackman Harris

    Set the FFT Window selector in the Instrument Options pop up menu to Hanning to select this windowing function. See Figure 3 37. Time Window 0 dB Frequency Filter Figure 3 37: FFT Magnitude Displayed Using Hanning Window 3 77 11801C User Manual...

  • Page 228: Figure 3 38: Fft Magnitude Displayed Using Hamming Window

    Fast Fourier Transforms The Hamming Window The Hamming window is similar to the Hanning window, but is optimized to lower the first side lobe, which is why the separation between the two spikes in the illustration below is greater than in the illustration on the previous page.

  • Page 229: Gpib Parameters

    GPIB Connection Connect the cable from your GPIB controller (computer) to the IEEE STD 488 PORT connector on the 11801C rear panel. See Figure 3 39. Three red lights show the internal GPIB status of the 11801C: SRQ (Service Request) is lighted whenever the 11801C activates the Service Request line.

  • Page 230: Setting Gpib Parameters

    Mode lets you set the mode to either Talk/Listen, Talk Only or Off Bus. Off bus effectively disconnects the 11801C from the bus. The 11801C must be in talk/listen mode to communicate with a controller using the GPIB. Talk only can be used to drive a printer or plotter over the GPIB.
  • Page 231 All message terminations assert the EOI (End Or Identify) signal in the interface. You can choose to have the 11801C recognize a Line Feed (LF) character as a message terminator in addition to EOI, by setting the Terminator selector to EOI/LF.
  • Page 232 GPIB Parameters 3 82 Reference...

  • Page 233: Graticules

    The other traces may or may not share the same axis labels. NOTE Traces extend outside the graticule area slightly. The axis labels represent the graticule edge, not the trace edge. 3 83 11801C User Manual...

  • Page 234: Figure 3 42: Dual Graticules With Multiple Traces

    Graticules You can display two different graticules, each being half the height of a single graticule display. In this case, each graticule shows one trace brighter than any others on that graticule. In addition, the graticule with the selected trace has the vertical ( ) and horizontal ( ) icons.

  • Page 235: Figure 3 43: The Graticules Pop Up Menu

    Graticules Figure 3 43: The Graticules Pop up Menu 3 85 11801C User Manual...

  • Page 236: Managing Graticules And Traces

    Graticules Managing Graticules When only one graticule is being displayed, you can create a dual graticule display using the Graticules pop up menu from the Waveform major menu. and Traces Touch the Create Second Graticule selector in this pop up menu. The selected trace and all traces from window time bases will be placed on the lower graticule.

  • Page 237: Changing Axis Units

    The vertical axis units most appropriate to TDR measurements are either units of rho (r) or of impedance (Z). The 11801C lets you specify units of rho for the vertical axis. Rho values can be converted to impedance values by...
  • Page 238 1. The Baseline Correction selector is discussed in Baseline Correction, page 3 17, in this manual. The baseline correction feature of the 11801C is used to hold the vertical position of a trace on the display when the TDR pulse level shifts due to a change in termination impedance.

  • Page 239: Hardcopy

    Use a standard cable fifteen meters or less in length. If you are not using a controller to initiate the hardcopy, set the GPIB Mode parameter of the 11801C to Talk Only and set the printer to Listen Only or Listen Always mode (address 31). Setting GPIB parameters is explained on page 3 80.

  • Page 240: Hardcopy Parameters

    Hardcopy Hardcopy Parameters Set the printing properties of the 11801C using the Hardcopy pop up menu in the Utility1 major menu. See Figure 3 45. This menu includes selectors for seven types of printers and for specific options available with some printers.
  • Page 241 The selections in the Color Map section of the menu become available whenever a color printer or plotter is selected. A color selector is available for selected elements of the display. To change a color, simply select the 3 91 11801C User Manual...
  • Page 242 Hardcopy element in the menu, then use the control knobs or keypad pop up menu to adjust the setting. To restore the color map to its factory default settings, touch the Default Color Map selector. The color selections are expressed in terms appropriate to the selected printer.

  • Page 243: Table 3 4: Repetition Encodings

    The first line contains the firmware version numbers, time and date, and the 11801C ID number. The second and third lines give the num ber of pixels per display line and the number of display lines, respectively. In Binary mode, the title block is terminated by a NULL character.

  • Page 244: Making A Hardcopy

    When the display becomes active again, you may oper ate the 11801C without affecting the hardcopy being printed. You can also initiate a new hardcopy at this point. The 11801C will automati cally queue multiple screen displays for hardcopy output. The number of hardcopies that can be queued is subject to the amount of available memory.

  • Page 245: Terminating A Hardcopy In Progress

    DeskJet Clr Screen Horizontal Centronics HPGL HiRes Centronics The default settings for the color map associated with a color printer setting may be recovered by selecting Default Color Map in the Hardcopy pop up menu. 3 95 11801C User Manual...
  • Page 246 Hardcopy 3 96 Reference...

  • Page 247: Histograms

    Histograms The 11801C can display histograms constructed from the selected trace's waveform data. You can display either a vertical (voltage) or horizontal (time) histogram. Only one type of histogram can be displayed at a time. See Figure 3 47. Figure 3 47: A Histogram Displayed on an Eye Diagram To create a histogram, use the Persist/Histograms pop up menu.

  • Page 248: Figure 3 48: The Persist/Histograms Pop Up Menu

    Histograms Figure 3 48: The Persist/Histograms Pop up Menu 3 98 Reference...

  • Page 249: Displaying A Histogram

    Display one trace on each graticule, and set up a histogram for each trace. Both histograms are acquired, but only the histo gram for the selected axis is displayed. Since the color graded database is used, the second histogram can be seen later. 3 99 11801C User Manual...

  • Page 250: Histogram Controls

    Histograms Histogram Controls The histogram display can be affected by several controls. You can specify which part of the selected trace is used to calculate the histogram. You can stop acquisition based on the number of waveforms acquired or the number of histogram samples acquired.
  • Page 251 If you want to stop the acquisition before the conditional acquisition com pletes, press RUN/STOP . The data that appears in the histogram readout is calculated as waveforms are acquired. The histogram display is updated based on the Refresh Rate. 3 101 11801C User Manual...

  • Page 252: Figure 3 49: Using Stop N Wfms

    Histograms Number of waveforms or samples left to acquire is shown here Figure 3 49: Using Stop N Wfms Changing the Display Update Rate The rate the histogram display is updated can be varied from zero seconds to three minutes (180 seconds). To change how often the histogram display is updated, touch Refresh Rate.
  • Page 253 Remove/Clr pop up menu Histograms cannot be displayed for stored traces. Histograms can be displayed for calculated traces if the calculated trace contains at least one active channel, even if the calculated trace contains a stored trace. 3 103 11801C User Manual...

  • Page 254: The Histogram Readout

    Histograms The Histogram In the major menu area of the display is a readout of histogram characteris tics. Included in the display are the values for the position of each of the Readout sides of the histogram box, statistical values and measurements. See Fig ure 3 50.

  • Page 255: Horizontal Controls

    The horizontal controls let you set the horizontal size and placement of your traces. Touch the horizontal icon ( ) to access these controls. Horizontal Icon Knob Labels Pan/Zoom Selector Figure 3 51: Horizontal Controls 3 105 11801C User Manual...

  • Page 256: Setting Horizontal Size And Position

    Horizontal Controls Setting Horizontal You can change the horizontal magnification, or size, of a trace. You can also move the trace left or right to see different portions of the trace. This is Size and Position called adjusting the horizontal position. To do either of these, touch the horizontal ( ) icon.

  • Page 257: Pan/Zoom

    Set horizontal magnification to the maximum and turn off trace vectoring. Trace Vectoring is discussed in the Vectored Traces section, page 3 219. The display will show each sampled data point of the trace. See Figure 3 52. 3 107 11801C User Manual...

  • Page 258: Figure 3 52: Horizontal Magnification With Pan/Zoom

    Horizontal Controls Figure 3 52: Horizontal Magnification with Pan/Zoom 3 108 Reference...

  • Page 259: Changing The Horizontal Reference Point

    If the user adjusts the main position, when the setting has been forced to change, the 11801C does not restore the old position when main size is decreased.

  • Page 260: Figure 3 53: The Horizontal Desc Pop Up Menu

    Horizontal Controls Figure 3 53: The Horizontal Desc Pop up Menu 3 110 Reference...

  • Page 261: Initialization

    Initialization Whenever you begin a new task using the 11801C, you should initialize the system so that all settings are at factory default." That way you do not get unexpected results because of settings remaining from the last use of the 11801C.

  • Page 262: Initializing And Erasing Nonvolatile Ram

    WAVEFORM and TRIGGER major menu buttons when you turn on Erasing Nonvolatile the 11801C. Release the buttons when the lights next to the major menu buttons stop flickering. When the power on sequence is complete, the message Teksecure Erase Memory Status: Erased, Instrument ID, on time, and number of power ups retained"...

  • Page 263: Labeling

    A label is a string of up to ten letters, numbers, or spaces that appears next to a displayed trace or as part of a trace or stored setting selector in menus. See Figure 3 55. Figure 3 55: Labels Displayed with Active Traces 3 113 11801C User Manual...

  • Page 264: Creating Labels

    Labeling Creating Labels You can create and edit labels by using the Labeling pop up menu, shown on the next page. Select Labeling in the Utility1 major menu to display the pop up menu. The uppermost section of this menu contains selectors for Displayed Traces, Stored Traces, and Stored Settings.

  • Page 265: Figure 3 56: The Labeling Pop Up Menu

    Labeling Figure 3 56: The Labeling Pop up Menu Changing the trace description of an active trace will not change the label of the trace. 3 115 11801C User Manual...

  • Page 266: Displaying Labels With Traces

    Labeling Displaying Labels Labels of displayed traces may be displayed on the screen with the traces. When Displayed Traces is selected, Display and Position selectors appear with Traces to the right of the trace selectors in the Labeling pop up menu. Turning on Display will cause the labels to appear with the traces.

  • Page 267: Mask Testing

    Mask Testing The 11801C enables you to perform mask testing (see Figure 3 57) using the Standard Masks and Mask Testing pop up menus. The Standard Masks pop up menu lets you select a mask from a collection of several predefined telecommunication masks.
  • Page 268 Mask Testing Masks are selected and created using the Mask Testing pop up menu. The Mask Testing menu lets you perform mask testing using the standard masks, or create a custom mask for testing. The Mask Testing pop up menu is accessed from the Display Modes major menu. You can create up to 10 custom masks, of up to 50 points each.

  • Page 269: Using Predefined Telecommunication Masks

    The ITU T G.703 electrical standards and the SONET/SDH opti cal standards masks are contained on multiple pages. Touch PAGE and PAGE to view the remaining masks available. Figure 3 58: The Standard Masks Pop up Menu 3 119 11801C User Manual...

  • Page 270: Figure 3 59: Page 2 Of The Sonet/Sdh Optical Standards

    The 11801C displays the mask you selected. The 11801C resets the time per division setting appropriate for the selected mask. Note however that you are free to change the time per division setting without altering the mask.
  • Page 271 AUTOSET button or configure for automatic autoset, the instrument auto matically turns on waveform averaging. See Averaging and Enveloping, page 3 13, and Autoset, page 3 9. To perform testing using standard masks, see Starting Mask Testing on page 3 128. 3 121 11801C User Manual...

  • Page 272: Creating Masks

    Mask Testing Creating Masks A user mask is created by moving a cross hair cursor on the display and adding or deleting points as required. You can edit or use the masks at any time by selecting the Mask Testing pop up menu from the Display Modes major menu.

  • Page 273: Figure 3 62: Editing A Mask

    Deleting User Masks To delete a mask, first display the Mask Testing menu. Select the mask to delete by touching the MaskN selector and then touch Delete Mask Defini tion. 3 123 11801C User Manual...

  • Page 274: Figure 3 63: Creating A User Mask

    Mask Testing Hints for Creating User Masks To ensure the best results when creating masks, remember the following and refer to Figures 3 63 and 3 64: Locate one point along the left edge or right edge of the mask further left or further right than any other.

  • Page 275: Figure 3 64: How Points Are Connected In A User Mask

    For the same reason, any defined masks displayed on the screen will be overwritten whenever you recall a stored setting or initialize the 11801C. NOTE For more details on Stored Settings, see page 3 177.
  • Page 276 Mask Testing Modifying a User Mask To modify an existing user mask, touch Mask Testing in the Display Modes major menu. Select the mask you want to edit by touching the appropriate MaskN Definition selector and then touch Edit Mask Definition. You can now add or delete points as described previously.
  • Page 277 Masks 1 and 3 must extend from the extreme left to the extreme right of the display. There cannot be more than 24 vertices in all three component masks. Each component mask must have at least three vertices. 3 127 11801C User Manual...

  • Page 278: Starting Mask Testing

    Mask Testing Starting Mask Testing After you have a user mask or standard mask selected, the mask remains on the display. However, mask testing does not begin automatically. To initiate mask testing, display the Mask Testing menu. Then select either Pass/Fail Test or Count Mask Hits.

  • Page 279: Figure 3 65: Mask Count Readout

    (approximately four billion). To begin conditional acquisi tion, touch Stop N Wfms. Acquisition will stop when N waveform records have been acquired. The number of waveforms left to acquire is shown in the lower left corner of the display. 3 129 11801C User Manual...

  • Page 280: Figure 3 66: Using Stop N Wfms

    Mask Testing Thus, without using Pass/Fail testing, there are two steps to stop acquisition based on the number of waveforms acquired: Step 1: Set the number of waveforms using Set N Wfms. Step 2: Begin the acquisition by selecting Stop N Wfms. If you want to stop the acquisition before the conditional acquisition com pletes, press RUN/STOP Number of...

  • Page 281: Standard Mask Definitions And Requirements

    Mask Testing Standard Mask The following tables define the standard telecommunication masks that are stored in the 11801C. Definitions and Requirements ITU T Electrical Standards Masks Signal Requirements: 75 W signals require a 75 to 50 W converter with signal attenuation entered.

  • Page 282: Table 3 7: Sonet/Sdh Optical Standards Masks

    Mask Testing SONET/SDH Optical Standards Masks Signal Requirements: O/E converter should comply with ANSI specifications. Data Type: NRZ, PRBS, SONET/SDH Frame or live data. Trigger Signal: Clock, recovered clock, or data signal. Table 3 7: SONET/SDH Optical Standards Masks Mask Name Data Rate 51.84 Mb/s OC3/STM1...

  • Page 283: Table 3 9: Ansi T1.102 Electrical Standard Masks

    Trigger Data Signal Signal GbEthernet 1.25 Gb/s Clock or data NRZ, PRBS or live data FDDI Halt 125 Mb/s Clock or data 11111000001111100000 1111100000... User Eye Programmable Clock or data NRZ, PRBS or live data 3 133 11801C User Manual...
  • Page 284 Mask Testing 3 134 Reference...

  • Page 285: Measurements

    The readouts of the measurements of the selected trace appear in the Measure major menu. The measurements are listed in the table below and on the next page. Refer to Appendix D for a detailed discussion of each of these measurements. 3 135 11801C User Manual...
  • Page 286 Measurements Table 3 11: Measurements Selector Measures Amplitude Measurements: Maximum amplitude, the most positive peak voltage/rho value. Minimum amplitude, the most negative peak voltage/ rho value. Middle amplitude, halfway between maximum ampli tude and minimum amplitude. Mean Arithmetic mean of all signal points. True Root Mean Square voltage.
  • Page 287 Frequency and user specific harmonic as well as spectral peak frequency measurements. Spectral This provides amplitude tracking for the fundamental Magnitude and user specific harmonic as well as spectral peak amplitude measurements. Total harmonic distortion. 3 137 11801C User Manual...

  • Page 288: Setting Up Measurements

    Measurements Setting Up Measurements are taken from displayed traces. The trace on which mea surements are based must be adjusted so that all areas that are needed to Measurements take the measurements are visible on the display. No part of the trace should extend above or below the graticule display area.

  • Page 289: Figure 3 68: Measurements Pop Up Menu With Frequency And Rms Selected

    Software Mode selector at the top of the menu. Measurements are part of the definition of a trace. When the Measure major menu is displayed, the measurements of the selected trace are also dis played. 3 139 11801C User Manual...

  • Page 290: Deleting Measurements

    Measurements Deleting To delete a measurement that is established on a trace, touch the Measure ments selector in the Measure major menu. In the pop up menu, touch the Measurements selectors for the measurements you want to remove. As you touch the measurement selectors, they will turn off highlighting and the measurement readouts will be removed from the major menu area.

  • Page 291: Measurement Mode

    In hardware mode, measurements are taken from the analog signal output from the sampling head before it is digitized and assembled into a trace record. The 11801C uses special timer circuits to take hardware measure ments. The advantage of hardware measurements is that they are per formed faster than software measurements.
  • Page 292 The 11801C may not be able to recognize an eye diagram if the the areas above and below the eye crossings are closed, or if the proximal and distal levels do not pass through the open areas.

  • Page 293: Table 3 12: Measurement Mode Comparison

    Limited to 512 point record length. Speed Slower Faster Updated when color graded data base is updated (selectable be tween 5 and 100 seconds) or when a measurement parameter changes, such as mesial level. 3 143 11801C User Manual...
  • Page 294 Measurements Use the Measurements pop up menu of the Measure major menu to select the measurement mode. At the top of this pop up menu are three selectors: Software Mode, Statistics Mode, and Hardware Mode. The selector for the current mode is always highlighted. Touch the selector for the mode you want.

  • Page 295: Comparing Measurements To References

    You can also use this feature to compare measurements on several different tests or parts. You can also tell the 11801C to save the current measurement readouts as the reference values for those measurements. If you then turn on the compare feature, you can observe how much the signal deviates from those references as you tune the circuit under test.

  • Page 296: Figure 3 69: Compare & References Pop Up Menu

    Measurements Figure 3 69: Compare & References Pop up Menu When compare mode is off, you can use the knobs or keypad menu to set the reference values. A selector appears in the Adjust References section of the Compare & References pop up menu for each measurement cur rently established on the selected trace.

  • Page 297: Changing Measurement Parameters

    In addition to the annotation lines, the portion of the trace that is used by the 11801C to determine the measurement value is highlighted when in Normal display mode, or marked by dashed vertical lines in other display modes.

  • Page 298: Figure 3 70: A Typical Individual Measurement Pop Up Menu

    36% of the way across the graticule, and the 11801C measures the frequency from the first complete cycle to the right of the left limit. The highlighted portion of the trace shows the area being measured.

  • Page 299: Table 3 13: Measurement Parameters

    When tracking mode is Off or Topline, you can set baseline or you can have the 11801C set it once by touching the Setup selector. Data Interval Determines whether the measurement will be taken from one cycle of the trace or the entire measurement zone.
  • Page 300 Jitter The location of the histogram for the Location Jitter measurement. May be Mesial or Eye Cross. If the 11801C does not rec ognize the signal as an eye diagram, only Mesial is available. Left Limit The beginning of the trace measure ment zone.
  • Page 301 For a 1 V peak to peak signal, S/N ratio of 20 creates a noise rejection band 0.05 V above and 0.05 V below the reference mesial level. 3 151 11801C User Manual...
  • Page 302 When reference tracking is set to Baseline or Off, you can set the top line or you can have the 11801C set it once by touching the Setup selector. Reference The track mode on the reference trace...
  • Page 303 When tracking mode is Off or Baseline, you can set topline or you can have the 11801C set it once by touching the Setup selector, and then adjust the values with the knobs.

  • Page 304: Measurement Statistics

    Measurements Measurement The 11801C collects measurement statistics automatically when in either software or hardware mode. (Statistics are not collected in statistics mode.) Statistics You can set the N parameter to determine the number of individual measure ments on which the statistics are based.

  • Page 305: Changing Default Parameters

    There Parameters is one set of default parameters for the 11801C. You can set the default parameters to the values you want. This does not change the measurement parameters of any existing traces, but will set the initialized state of all new traces that you define.

  • Page 306: Figure 3 72: Measurements Pop Up Menu With Software Defaults

    Measurements Figure 3 72: Measurements Pop up Menu with Software Defaults 3 156 Reference...

  • Page 307: Power On

    Power On Installation Before you first power on your 11801C, you should make certain it is cor rectly installed. The installation sequence involves the following controls, connectors and switches on the rear panel (see Figure 3 73): POWER Connector FUSE...
  • Page 308 STANDBY. Step 9: To operate the instrument, set the front panel ON/STANDBY switch to ON. Once the 11801C is installed, use the ON/STANDBY switch as the power switch. 3 158 Reference...

  • Page 309: Power On Sequence

    Warm Up Period It takes about 20 minutes for the 11801C to warm up after power on. You should perform any enhanced accuracy calibrations only when the instru ment has warmed up and achieved thermal stability. The enhanced accura cy calibrations are described on page 3 49.
  • Page 310 Power On 3 160 Reference...

  • Page 311: Record Length

    The 4096 point record length has the same sample interval (the time be tween successive trace samples) as 5120 point records. The 4096 point trace appears shorter on the display than 5120 point traces. Many Fast 3 161 11801C User Manual...

  • Page 312: Figure 3 76: The Horizontal Desc Pop Up Menu

    Record Length Fourier transform algorithms require record lengths that are a power of two. The 4096 point record length is provided as a convenience, and the visual truncation is a natural result. You control the record length by using the Horizontal Desc pop up menu in the Waveform major menu.

  • Page 313: Rs 232 C Parameters

    RS 232 C Parameters The 11801C can be controlled by a remote computer, through one of two interfaces. These interfaces are industry standards IEEE Std 488 (GPIB) and RS 232 C. This manual does not discuss the details of connecting a remote computer to the 11801C or the syntax and capabilities of remote commands.

  • Page 314: Setting Rs 232 C Parameters

    RS 232 C Parameters Setting RS 232 C Communication between the 11801C and the attached computer can occur only if the two are configured in a compatible manner. Parameters Use the GPIB/RS232C pop up menu in the Utility1 major menu to set the RS 232 C parameters directly, before you attempt to communicate with the attached computer.
  • Page 315 Hard flagging, Soft flagging, or None. Touch the selector repeatedly until the appropriate setting is displayed in the selector. Flagging is used by the 11801C or the comput er to signal that its input buffer is full, and that the other device should stop transmitting until further notice.
  • Page 316 RS 232 C Parameters 3 166 Reference...

  • Page 317: Sampling Heads

    A sampling head is a small plug in device that samples electrical signals and converts them to a much lower speed analog output signal. At least one sampling head must be installed in the 11801C or in an attached SM 11 Multi Channel Unit to acquire signals.

  • Page 318: Installing Sampling Heads

    Once the head is seated, turn the screw shaft on the sampling head to tighten the head into place. CAUTION Never install or remove a sampling head with the 11801C power Sampling Head Front The front panel of a typical sampling head is shown in Figure 3 80. The...
  • Page 319 Always wear an antistatic wrist strap connected to the ANTISTATIC CONNECTION on the 11801C when you are making connections to a sampling head or handling the device under test.

  • Page 320: Controlling Tdr And Smoothing Functions

    Sampling Heads Controlling TDR and The time domain reflectometry (TDR) and smoothing functions cannot be controlled from the sampling head front panel. These functions are con Smoothing Functions trolled using the Sampling Head Fnc's pop up menu in the Waveform major menu.

  • Page 321: Figure 3 81: The Sampling Head Fnc's Pop Up Menu

    Negative dB values or fractional attenuation factors indicate gain, rather than attenuation. External channel attenuation is a feature of the mainframe, not of the sam pling head. Thus, this feature applies to all sampling heads. 3 171 11801C User Manual...
  • Page 322 Sampling Heads Smoothing Smoothing is processing applied by the sampling head prior to the digitiza tion of a trace, to reduce noise. When smoothing is on, the sampling head samples each trace sample, or dot, eight times before going on to the next dot.

  • Page 323: Saved Trace Descriptions

    Saved Trace Descriptions The 11801C can display eight traces at any one time. However, the instru ment is capable of handling many more traces than it can display. A trace that is defined but not displayed is called a saved trace description.

  • Page 324: Figure 3 82: The Save Trace Desc Pop Up Menu

    Saved Trace Descriptions Figure 3 82: The Save Trace Desc Pop up Menu Saved trace descriptions must be of simple one channel traces and cannot be of traces that use any arithmetic operation such as subtraction or multi plication. Averaging is the only trace function that can be applied to a saved trace description.

  • Page 325: Saving A Trace Description

    8 are the displayed traces. The number of saved trace description cells that are available depends on the configuration of your 11801C system. If no SM 11 Multi Channel Units are connected, 32 cells are provided, numbered 9 through 40. If one or more SM 11 Multi Channel Units are connected, then more saved trace description cells are provided.

  • Page 326: Saving All Displayed Traces As Saved Trace Descriptions

    Saved Trace Descriptions Saving All Displayed You can quickly save all displayed traces as a group of saved trace descrip tions. The procedure is similar to saving a single trace description. Traces as Saved Trace Descriptions Step 1: Press the WAVEFORM button and touch the Save Trace Desc selector in the major menu area.

  • Page 327: Stored Settings

    Stored Settings When you initialize the 11801C, you recall a stored front panel setting that was established at the factory. You can save your own front panel settings for quick recall. If you establish a test setup, you might want to store the setting and go to another task.

  • Page 328: Storing Settings

    Stored Settings Storing Settings Use the Store Setting pop up menu in the Store/Recall major menu to store a setting. After you setup the instrument, touch the Store Setting selector to display the pop up menu. See Figure 3 83. Figure 3 83: The Store Setting Pop up Menu You can choose which major menu you want to be displayed when the stored setting is recalled.

  • Page 329: Recalling Stored Settings

    The Recall Setting pop up menu also provides a way to initialize the 11801C. The Initialize Setting selector operates the same as the Utility1 major menu Initialize selector. Initialization is described completely on page 3 111.

  • Page 330: Deleting Stored Settings

    Stored Settings Deleting Stored Use the Delete Setting pop up menu in the Store/Recall major menu to delete a stored setting. Select the setting or settings to delete by touching Settings the selectors in the top part of the pop up menu (see Figure 3 85). If more than 15 settings are stored, touch Page and Page to scroll through the menu.

  • Page 331: Sequencing Through Stored Settings

    SEQUENCE SETTING button to recall the next setting of the sequence. This button is located above the sampling head compartments, near the ON/STANDBY switch. The SEQUENCE SETTING Button Figure 3 86: Front Panel SEQUENCE SETTING Button 3 181 11801C User Manual...
  • Page 332 Stored Settings 3 182 Reference...

  • Page 333: Stored Traces

    M1-STO3. This trace acquires data from sampling head channel M1 and subtracts from each sample the data recorded in stored trace number 3. Stored traces are saved when you power off the instrument and are avail able when you power it on again. 3 183 11801C User Manual...

  • Page 334: Storing Traces

    Stored Traces Storing Traces When you store a trace, the instrument takes a copy of the trace record of the selected trace. The trace record is always copied into the stored trace location with the lowest available number, unless you select otherwise. Figure 3 87: The Store Trace Pop up Menu Use the following steps to store a trace: Step 1: Create a stable trace on the display.

  • Page 335: Recalling Stored Traces

    Trace selector to display the pop up menu. In the pop up menu, touch the selector for the stored trace you want to display. See Figure 3 88. Figure 3 88: The Recall Trace Pop up Menu 3 185 11801C User Manual...

  • Page 336: Deleting Stored Traces

    Stored Traces Deleting Stored You can delete stored traces by using the Delete Traces pop up menu in the Store/Recall major menu. This pop up menu may also be used to delete Traces displayed traces. See Figure 3 89. In the Delete Traces pop up menu, touch the selectors for the displayed and stored traces you want to delete.

  • Page 337: Displaying Time And Date With Stored Traces

    Recall Trace and Delete Trace pop up menus in the Store/Recall major menu, the Vertical Desc and Horizontal Desc pop up menus in the Waveform major menu, and the Labeling pop up menu in the Utility 1 major menu. 3 187 11801C User Manual...
  • Page 338 Stored Traces 3 188 Reference...

  • Page 339: System Identification

    Figure 3 90: The Identify Pop up Menu The top section of the Identify pop up menu shows the devices; you can see the status of the 11801C mainframe or any attached SM 11 Multi Chan nel Unit by touching its selector.
  • Page 340 System Identification The third section of the Identify pop up menu shows which channels have sampling heads installed (1X, 10X, etc.) and which channels are not avail able (0X). For those channels that have sampling heads, the sampling head type and serial number are shown. The bottom section of the Identify pop up menu shows instrument options and their respective states, such as whether or not the option is installed.

  • Page 341: Tdr

    Because of the architecture of the step generator, the output voltage of the step depends on the DC resistance to ground of the device under test. The following sections describe the operation with a short circuit, an open circuit, and a 50 W load. 3 191 11801C User Manual...

  • Page 342: Figure 3 92: Step Generator With A Shorted Output

    Operation Into a Short Circuit Initially, the diode switch is conducting -10 mA. Since the step generator output is initially shorted, the resistance to ground is 0 W and the output voltage is 0 V. When the diode switch opens (reverse biased), apparent resistance to ground at the acquisition point (and at the channel connector) is 25 W, because the internal termination resistance is 50 W and the connector impedance is 50 W.

  • Page 343: Figure 3 94: Step Generation With A 50 W Load

    See Figure 3 94. Baseline Correction Baseline correction is a feature of the 11801C instrument. This feature holds the displayed baseline of a trace in one location despite variations of the offset in the sampling head.

  • Page 344: Example: Taking Tdr Measurements

    For this example you will need an 11801C with at least one SD 24 installed. Also, you will need one SMA cable, preferably of 5 ns length.

  • Page 345: Figure 3 96: Tdr Step And Reflection

    The units of measure commonly used in TDR are units of rho (r), measured on the vertical axis, and time on the horizontal axis. You can change the measurements by using the Graticules selector on the Waveform major menu. 3 195 11801C User Manual...

  • Page 346: Figure 3 97: The Graticules Pop Up Menu

    Propagation Velocity selector and adjust this parameter. If you don't know the velocity or are using Tektronix SMA cables, accept the 0.7 default. This unitless number represents the fraction of the speed of light that signals pass through your network or transmission line.
  • Page 347 For the SD 20, the step amplitude depends on the external signal source used. Note that when using the TDR Preset function, the vertical axis scaling is automatically set to Rho. Step 8: Touch Exit to remove the pop up menu and view the trace and graticule. 3 197 11801C User Manual...

  • Page 348: Example: Differential And Common Mode Tdr

    For this example you need at least one SD 24 installed in the left most slot of the 11801C. You also need one SMA cable, preferably of 5 ns length. Step 1: Initialize the 11801C (press UTILITY, touch Initialize and touch Initialize again).

  • Page 349: Figure 3 98: Single Channel Tdr

    Figure 3 98: Single Channel TDR 3 199 11801C User Manual...

  • Page 350: Figure 3 99: Channels 1 And 2 Tdr

    Figure 3 99: Channels 1 and 2 TDR Notice that there are two rising edges on each trace. On the upper trace, the left most edge is the step transmitted by the step generator of the upper channel, M1. The second rising edge is the step transmitted by the step generator of lower channel, M2.
  • Page 351 You can then alternately enable the step generators on both channels and sample the transmitted signal on the other channel to perform forward and reverse TDT measurements. 3 201 11801C User Manual...

  • Page 352: More About Tdr Measurements

    More About TDR When making differential or common mode TDR measurements, it is impor tant that the two steps arrive at the same time at the reference plane (usually Measurements the connection point to the device under test). To check and adjust this condition, disconnect the transmission cables from device under test at the point where the cables connect to the device.

  • Page 353: Time And Date

    Time and Date The 11801C has an internal clock, with battery back up, that keeps track of the time and date. You can set the clock using the Instrument Options pop up menu in the Utility1 major menu. When you touch the Hours, Min utes, Seconds, Month, Day, or Year selector, one of the knobs is assigned to set that clock parameter.

  • Page 354: Displaying Time And Date With Stored Traces

    Time and Date Displaying Time and You can display the time and date that a trace was stored by selecting Stored Tra Time/Date, in the Instrument Options pop up menu of the Date with Stored Utility1 major menu. The time and date for each stored trace appears in the Traces stored trace selectors.

  • Page 355: Trace Definition And Management

    Trace Definition and Management Traces are the visible representation on the display of the electrical signal, or combination of signals, that the 11801C samples and digitizes. You can define and display up to eight traces simultaneously. You define a new trace on the main time base by entering a trace expres sion.

  • Page 356: Defining New Traces

    The selectors presented in the DefTra pop up menu are grouped into the following categories: Channel Selectors let you specify a sampling head channel. The 11801C presents only those channel numbers where a sampling head is installed. Numeric Keypad lets you enter a numeric value as part of your trace expression, or one of the four arithmetic operators +, +, *, and /.

  • Page 357: Figure 3 102: The Deftra Pop Up Menu

    Figure 3 102: The DefTra Pop up Menu Stored Traces list all the traces that have been stored in the 11801C. For a discussion of stored traces, see Stored Traces on page 3 183. This area of the menu is shared with the trace functions selectors described above.

  • Page 358: Table 3 14: Trace Functions

    Trace Definition and Management Using Trace Functions in Trace Expressions Trace functions operate on arguments which are usually channels or trace expressions. The function is applied to each individual sample of the trace. The trace that is displayed is built from the function being applied to each sample.

  • Page 359: Trace Numbers

    Trace Numbers When you define a new trace, the 11801C assigns it a trace number. Trace numbers range from 1 through 8. New traces are assigned the lowest avail able number. Once a number is assigned to a trace, the number does not change.

  • Page 360: Selecting Traces

    Trace Definition and Management Selecting Traces When you define a new trace, it is highlighted (bright intensity) on the dis play. This indicates that it is the selected trace. When multiple traces are displayed, there is always one selected trace. The graticule labels and axes match the color of the selected trace.

  • Page 361: Modifying Traces

    You can use the Back Space selector to alter the trace, or you can extend the trace expression. When you touch the Enter Desc selector, the new trace expression is applied to the selected trace. 3 211 11801C User Manual...

  • Page 362: Removing Traces

    Trace Definition and Management Removing Traces You can remove traces from the display in three different ways: using the Remove selector in the Remove/Clr pop up menu, using the Select Chan nel button on the sampling head, or using the Delete Trace selector in the Store/Recall menu.
  • Page 363 If you touch a trace selector by accident, touch it again to remove the highlighting. If you want to delete all the displayed and stored traces, touch the All Traces selector. 3 213 11801C User Manual...

  • Page 364: Trace Scaling

    Trace Definition and Management Trace Scaling When you define a new trace, it is defined as either a fast trace or a high precision trace. Fast traces are computed with integer arithmetic, and oper ate significantly faster than high precision traces. High precision traces use floating point arithmetic to provide highest precision.

  • Page 365: Triggering

    23 ns (45.5 ns for Option 1M). NOTE When you use an external trigger source, the 11801C may not be supplied with triggers. To restore operation, supply a trigger signal to the DIRECT or PRESCALE inputs, or select the Auto mode.
  • Page 366 Source displays a pop up menu that lets you select the signal that the 11801C monitors for the trigger event. The External Direct source is the DIRECT connector on the front panel. The Internal Clock source is synchronized with the CALIBRATOR output on the front panel. The External Prescaler source is the PRESCALE connector on the front panel.
  • Page 367 1 GHz. It can be used at all frequencies if there is sufficient trigger signal amplitude to reliably trigger the oscilloscope. Touching the High Fre quency icon toggles the setting between On and Off. 3 217 11801C User Manual...
  • Page 368 Triggering Trigger Holdoff displays a pop up menu that allows you to select auto or manual holdoff mode. See Figure 3 108. For Auto mode, the trigger holdoff is automatically programmed to the minimum possible holdoff value, shown under Actual Holdoff. This value is slightly beyond the rightmost point acquired in the Main record.

  • Page 369: Vectored Traces

    The 11801C normally extends the columns to touch" adjacent columns, so that no gaps are shown in the trace. You can turn off this trace vectoring so that no intermediate data is assumed for display purposes.
  • Page 370 Vectored Traces Trace vectoring makes the biggest difference in the appearance of a trace with 512 samples. As the record length of a trace increases, the visual enhancement of trace vectoring becomes less evident. When you display a 512 sample trace, with trace vectoring turned off, the individual samples of the trace show as dots.

  • Page 371: Vertical Controls

    The vertical controls let you set the vertical size and placement of your traces. Touch the vertical icon ( ) to access these controls. See Fig ure 3 111. Vertical Icon Knob Labels Chan Sel Selector Figure 3 111: Vertical Controls 3 221 11801C User Manual...

  • Page 372: Setting Vertical Size And Offset

    Vertical Controls Setting Vertical Size You can change the vertical magnification, or size, of a trace. You can also move the trace up or down on the display. This is called adjusting the verti and Offset cal offset. To do either, touch the vertical ( ) icon; this assigns the knobs to adjust the vertical size (top knob) and offset (bottom knob) of a channel of the selected trace.
  • Page 373 Trace Sep, or trace separation. This vertical offset control lets you move a window trace up or down, to visually separate it from other window traces or the main time base trace. 3 223 11801C User Manual...
  • Page 374 Vertical Controls 3 224 Reference...

  • Page 375: Windows

    Windows are created by touching the Window icon above the graticule. When you touch the Window icon, the 11801C creates a second graticule to show the window trace. The portion of the main trace that is windowed is highlighted.

  • Page 376: Changing Window Size And Position

    Windows You can create more than one window trace from a single main trace. You cannot create a window trace of a window trace. If you remove all windows, the display automatically returns to a single graticule display. Changing Window You can change the size and position of a window trace just as you do with any main trace.

  • Page 377: Positioning Window Traces Automatically

    Windows Positioning Window The 11801C can position your window traces automatically based on an electrical event that occurs on the main trace. This triggers the window trace Traces Automatically in a manner similar to triggering of the main trace. Automatic window posi tioning can only be used on traces that do not use arithmetic operators or trace functions.
  • Page 378 Position Mode can be set to Manual (you position the window with the knobs) or Automatic (the 11801C positions the window based on an electrical event on the main trace). Automatic window positioning has a resolution equal to one Main record sample interval.
  • Page 379 The Top/Base Method parameter affects all window traces. It also affects how automatic measurements are performed on all traces. You can also change this parameter from the Measurements pop up menu in the Measure major menu. 3 229 11801C User Manual...
  • Page 380 Windows 3 230 Reference...

  • Page 381: Xy Traces

    You can have only one XY trace. You cannot take measurements of XY traces. This XY trace is a constellation diagram. Constellation diagrams are discussed on page 3 25. When an XY trace is displayed, the axis units cannot be changed from volts on either axis. 3 231 11801C User Manual...
  • Page 382 XY Traces XY Trace Section Figure 3 115: The Horizontal Desc Pop up Menu You initiate and control XY traces using the Horizontal Desc pop up menu in the Waveform major menu. See Figure 3 115. Two sections of the menu are titled XY Display Mode, one for displayed traces and one for stored traces.
  • Page 383 To restore an XY trace to normal YT mode, select the XY trace and touch the Normal YT selector in the Horizontal Desc pop up menu. Constellation diagrams are a common application of XY traces. See Constel lation Diagrams, on page 3 25, for more details. 3 233 11801C User Manual...
  • Page 384 XY Traces 3 234 Reference...

  • Page 385: Appendix A: Accessories

    Optional Accessories The following optional accessories have been selected from our catalog specifically for the 11801C. For detailed information and prices, see a Tektro nix products catalog or contact your local Tektronix field representative. Option 1M, provides interface to SM 11 Multi Channel Units.

  • Page 386: Power Cord Options

    Calibration Head, Tektronix part number 067-1413-00. Power Cord Options The following power cords are available for the 11801C. Option A1 Universal European 220 V/6A, 50 Hz, Tektronix part number 161-0066-09. Option A2 United Kingdom 240 V/6A, 50 Hz, Tektronix part number 161-0066-10.

  • Page 387: Appendix B: Specifications

    Appendix B: Specifications The 11801C electrical characteristics apply to the following conditions: The instrument has had a 20 minute warm up period. The instrument is operating in an environment that meets the limits described in Environmental Specifications in this section.

  • Page 388: Table B 2: 11801C Time Base Specifications

    Appendix B: Specifications Table B 2: 11801C Time Base Specifications Characteristic Specification Internal reference clock Crystal controlled oscillator Sample rate 200 kHz maximum Record length User selectable, 512, 1024, 2048, 4096, or 5120 points Sweep rate resolution 1-2-5 steps or 1 ps/div increments...

  • Page 389: Table B 3: 11801C Input And Output Specifications

    Appendix B: Specifications Table B 3: 11801C Input and Output Specifications Characteristic Specification Touch panel Infrared beam touchable array, 22 rows of 11 columns Knobs 2 general purpose knobs, set by user to desired function Calibrator output step Voltage 500 mV open circuit or...

  • Page 390: Table B 4: 11801C Trigger Specifications

    Appendix B: Specifications Table B 4: 11801C Trigger Specifications Characteristic Specification Jitter 1.1 ps RMS + 4 ppm of position (typical) 2.0 ps RMS + 5 ppm of position max Freq = 2.5 GHz, DC/1, = 200 mV , HF = Off,...

  • Page 391: Table B 5: 11801C Display Specifications

    Appendix B: Specifications Table B 4: 11801C Trigger Specifications (Cont.) Characteristic Specification Direct AC coupled 1: 100 mV, 30 kHz to 3 GHz 50 mV, 30 Khz to 4 GHz (typical) 10: 1 V, 30 kHz to 3 GHz (Auto, Enhanced Off, Auto holdoff, HF Off)

  • Page 392: Table B 6: 11801C Ac Line Power Specifications

    Appendix B: Specifications Table B 6: 11801C AC Line Power Specifications Characteristic Specification Voltage ranges 90 to 132 V or 180 to 250 V Voltage ranges apply to trace distortion, which reduces peak line voltage 5% Installation Category II Frequency...

  • Page 393: Table B 8: 11801C Certifications And Compliances

    Appendix B: Specifications Table B 8: 11801C Certifications and Compliances Characteristic Specification Approvals UL3111 1 - Standard for electrical measur ing and test equipment CAN/CSA C22.2 No. 1010 1 - Safety require ments for electrical equipment for measure ment, control and laboratory use...
  • Page 394 Appendix B: Specifications Appendices...

  • Page 395: Appendix C: User Service

    Avoid the use of chemical cleaning agents which might damage the plastics used in this instrument. Use a nonresidue type of cleaner, preferably isopropyl alcohol or totally denatured ethyl alcohol. Before using any other type of cleaner, consult your local Tektronix service center or representative. Exterior Dust on the instrument can be removed with a soft cloth or small brush.

  • Page 396: Packaging For Shipment

    Appendix C: User Service Packaging for If you ship the 11801C, pack it in the original shipping carton and packing material. If the original packing material is unavailable, package the instru Shipment ment as follows: Step 1: Obtain a corrugated cardboard shipping carton with inside dimensions at least 15 cm (6 in) taller, wider, and deeper than the instru ment.
  • Page 397 Trace Functions Absolute Value Abs(n) + W(n) for W(n) w 0 Abs(n) + * W(n) for W(n) t 0 where: n = index into the record of data points W(n) = input sampled data point 11801C User Manual...
  • Page 398 Appendix D: Algorithms Average (n) + W(n) for p + 1 W(n) * Avg (n) + Avg (n) ) INT(log 2 (p log e 2)) for 1 t p t P W(n) * Avg (n) + Avg (n) ) for p w P where: n = index into record of data points W(n) = input sampled data point...
  • Page 399 X(k) , the complex sequence representing the Discrete Fourier Transform of the sequence x(n) , is computed as: R * 1 X(k) + x(n) n + 0 for k + [0@@@ R * 1] where R , the record length, is a power of 2 11801C User Manual...
  • Page 400 Appendix D: Algorithms The linear magnitude (FFT ) and the phase (FFT ) of the FFT are phase computed as: (k) + A(k) ) B(k) B(k) (k) + acrtan phase A(k) where A(k) = real part of X(k) B(k) = imaginary part of X(k) The magnitude and phase for negative frequencies are discarded and linear interpolation is used to expand the positive frequencies to fill the entire record length.

  • Page 401: Table D 1: Filter Characteristics Of Fft Windowing Functions

    (the width of an equivalent rectangular spectral response that would pass the same noise power as this windowing function. 3 dB bandwidth and 6 dB bandwidth apply to the major lobe. These affect the frequency resolution. 11801C User Manual...
  • Page 402 Appendix D: Algorithms scallop loss is the attenuation of the windowing function at the odd numbered (interpolated) points in the FFT waveform. worst loss is the worst case processing loss (the sum of the scallop loss and the equivalent noise bandwidth, in dB). Filter Filter(n) + Smooth(Smooth(n)) Centered Mode (Non Causal) Filter Algorithm...
  • Page 403 R = record length in points Logarithm Log(n) + log W(n) where: n = index into record of data points W(n) = input sampled data point This function is implemented by the 80287 math coprocessor and support ing routines. 11801C User Manual...
  • Page 404 Appendix D: Algorithms Natural Logarithm Ln(n) + log W(n) where: n = index into record of data points W(n) = input sampled data point This function is implemented by the 80287 math coprocessor and support ing routines. Rho is normally calculated to be between +1 and -1 by: For trace M1: volts rho +...
  • Page 405 (pol1)) ) AAA ) ABS(C (poln)) Trace functions Smooth, Filter, and Avg have no effect on the formulas used for rho. For trace C + ... + C " the rho values produced are the same as if C was 0. 11801C User Manual...
  • Page 406 Appendix D: Algorithms Signum Signum(n) + 1.0 for W(n) u 0 Signum(n) + 0 for W(n) + 0 Signum(n) + * 1 for W(n) t 0 where: n = index into record of data points W(n) = input sampled data point Square Root Sqrt(n) + W(n) where:...
  • Page 407 + n * s ) 1 for n The shifted mode trace only uses points that occur before the correspond ing point. Thus, the only points that are assumed occur before the trace, not after. D 11 11801C User Manual...
  • Page 408 Measurements some are to be determined automatically by the 11801C. It is common to have the 11801C dynamically measure topline and baseline. You specify automatic topline and baseline positioning by turning tracking on in the individual measurement pop up menus.
  • Page 409 = index of left most measurement zone sample n = index of right most measurement zone sample W(j) = input sampled data point R = reference level measurement parameter T = time interval between successive samples D 13 11801C User Manual...
  • Page 410 Appendix D: Algorithms Cross The cross measurement finds the left most crossing of the reference level of the proper slope that is within the measurement zone. The horizontal posi tion of the crossing point is displayed. Linear interpolation between vertical points and between time intervals is necessary to determine the crossing time, when the reference level value does not correspond to acquired data.
  • Page 411 5. Calculate the frequency: Frequency + Cross * Cross Linear interpolation between vertical points and between time intervals is necessary to determine the crossing time, when the mesial value does not correspond to acquired data. D 15 11801C User Manual...

  • Page 412: Table D 2: Values Of Icoeff For Fft Windowing Functions

    Appendix D: Algorithms Frequency Domain Measurements There are two modes of operation, harmonic and peak search. If Search Mode is set to harmonic, the instrument will determine the fundamental frequency, fo, by searching for the highest peak of the FFT magnitude in the measurement zone.
  • Page 413  ". If the trace is null, the measurement value will show error". Over Shoot Max * topline OverShoot + 100 topline * baseline If the values of topline and baseline are equal, the measurement value will show error". D 17 11801C User Manual...
  • Page 414 Appendix D: Algorithms Peak Peak PeakPeak + Max * Min An overrange value in the trace record will qualify the measurement with  ", and an underrange value in the trace record will qualify the measurement with  ". If the trace record has both underrange and overrange values, the measurement readout will be qualified with ?".
  • Page 415 4. Calculate the rise time: Rise + t Linear interpolation between vertical points and between time intervals is necessary to determine the crossing times, when the proximal and distal values do not correspond to acquired data. D 19 11801C User Manual...
  • Page 416 Appendix D: Algorithms [W(j ) 1) ) W(j) RMS + [2(n * m)] where: m = index of left most measurement zone sample n = index of right most measurement zone sample W(j) = sampled data point The summation extends over the interval of time corresponding to one period when Data Interval is set to one period, or the entire measurement zone when Data Interval is set to the entire zone.
  • Page 417 2. Apply the FFT interpolation algorithm described above to find the spec tral frequency. Spectral Magnitude The 11801C computes the magnitude of a har monic frequency by interpolating the FFT magnitude waveform and com pensating for the FFT windowing function effect.

  • Page 418: Table D 3: Values Of Wcoeff And M For Fft Windowing Functions

    Appendix D: Algorithms Table D 3: Values of wcoeff and m for FFT Windowing Functions FFT Window wcoeff(0) wcoeff(1) wcoeff(2) wcoeff(3) Blackman 0.42 -0.5 0.08 Blackman Harris 0.35875 -0.48829 0.14128 -0.01168 Hamming 0.54 -0.46 Hanning 10.5 -0.5 Rectangular Triangular 3. For the nth harmonic magnitude, compute the harmonic frequency and apply the previous algorithm.
  • Page 419 The proximal, mesial, distal, and reference values are then determined as percentages of the topline and baseline. In statistical measurement mode, the 11801C creates a voltage histogram in order to calculate Amplitude, Area+, Area-, or Energy. The 11801C uses timing (horizontal) histograms to determine the crossing values for timing measurements.
  • Page 420 Appendix D: Algorithms Jitter The Jitter measurement is available only in statistical measurement mode. 1. Find the leftmost mesial crossing, using timing histograms. This horizon tal value is Cross 2. Find the second mesial crossing, using the same method. If a second crossing is found, its horizontal value is Cross a.
  • Page 421 If Level mode is set to Relative, then the 11801C performs the following steps to determine the baseline and topline voltages: 1. If Tracking is off, the 11801C uses the baseline and topline values that were last set using the knobs or those left from the most recent use of tracking.
  • Page 422 4. The 11801C acquires a new trace record of the current record length. The measurement hardware determines the dot number(s) on the trace(s) where the signal crosses the level(s) required for the measure ment.
  • Page 423 Trace Color 1 [Max/4 + 1] to Max/2 Rose Trace Color 2 [Max/8 + 1] to Max/4 Purple Trace Color 4 [Max/16 + 1] to Max/8 Light Blue Window Trace 1 to Max/16 Green Trace Color 3 D 27 11801C User Manual...
  • Page 424 Appendix D: Algorithms For Max 6 and Max sf + Scale Factor + Hit Density Default Color Maps To [Max/sf +1] to Max Pale Yellow Trace Color 1 [Max/sf + 1] to Max/sf Rose Trace Color 2 [Max/sf + 1] to Max/sf Purple Trace Color 4 [Max/sf...
  • Page 425 Appendix E: Messages The 11801C displays a message at the top of the display whenever one of the following events occurs: Errors The 11801C cannot perform a requested operation. Warnings The instrument performs the requested operation, but warns you that the results may be corrupted or meaningless.
  • Page 426 Connect a 50 W terminator to the selected channel and press Proceed when ready. The 11801C is waiting for you to put a terminator on the signal connector of the sampling head channel you are calibrating, and touch the Proceed selector.
  • Page 427 Hardcopy absent or off line. Either no printer is connected to the 11801C, or the printer that is connected is not on line. Until the condition is remedied, hardcopies cannot be taken. Minor time base calibration problem: (channel #).
  • Page 428 Appendix E: Messages Rho scaling failed to find -1 r point. Cannot calibrate rho scales. If the trace is not triggered, or if the portion of the trace to the immediately to the left of the display (earlier in time) is not a flat trace, the voltage reference cannot be determined.
  • Page 429 Lines that show the current measurement parameter settings in a visual way. Autoset A means of letting the 11801C set itself to provide a stable and meaning ful display of a given trace. Averaging Displaying a trace that is the combined result of several acquisitions, thereby reducing apparent noise.

  • Page 430: Menu

    Whenever a trace is created, the mea surement parameters are copied from the default set. Distal The most distant point from a reference point. As used in the 11801C, the ending measurement point for timing measurements. Dragging The act of changing your touch panel selection by moving your finger without removing it from the screen.
  • Page 431 Mesial The middle point of a range of points. As used in the 11801C, the middle measurement point between proximal and distal points for timing mea surements, and the intermediate height between baseline and topline for amplitude measurements.
  • Page 432 11801C: Normal, Variable, Infinite and Color Grading. Pixel A visible point on the display. The 11801C display is 551 pixels wide and 704 pixels high. Each pixel may be set to any of the display colors. Pop up Menu A temporary menu that provides an interactive dialog for a specific purpose.
  • Page 433 The definition of what the trace displays. It can include one or more channels combined arithmetically and modified by functions. Trace Number A number assigned by the 11801C to identify a trace. Displayed traces are numbered 1 through 8. A new trace is always given the lowest available number.

  • Page 434: Window

    Glossary Window A trace that represents a horizontally expanded portion of another trace. XY Trace A trace where both horizontal and vertical position of the data points reflect signal data. YT Trace A trace where the vertical position of the trace data points reflects signal data, and the horizontal position of the trace data points reflects time.
  • Page 435 Enhanced accuracy, 3 49 3 60 AUTOSET, 2 9, 3 9 Constellation Diagrams, 3 25 3 28 automatic calibration, 3 51 3 52, HARDCOPY, 1 6, 3 95 3 96 3 54, 3 55 Contacting Tektronix, ii MENUS, 2 3 11801C User Manual...
  • Page 436 Index manual calibration, 3 56 3 60 Horizontal sampling heads, 3 49 3 60 controls, 3 105 3 110 icon ( ), 3 105, 3 226 Enveloping, 2 45, 3 13 3 16 Gain pop up menu, 3 53, 3 56 3 57 pan/zoom, 3 107 3 108 Error messages, E 1 E 4 reference point, 3 109 3 110...
  • Page 437 Identify, 3 189 3 190 Normal persistence, 3 44 Masks creating a user mask from a stan dard mask, 3 126 creating user, 3 122, 3 123, 3 124 deleting user, 3 123 editing user, 3 123, 3 124, 3 126 11801C User Manual...
  • Page 438 Index individual measurement, 3 147 Recall Trace pop up menu, 3 185 Set N Samples, 3 101 Instrument Options, 3 7, Record length, 2 51, 2 52, 3 99, Set N Wfms, 3 101, 3 129 3 10 3 12, 3 41, 3 203, 3 214, 3 161 3 162 3 220 Set Zero Rho selector, 3 31...
  • Page 439 Traces, 3 205 3 214 additional, 2 22 clearing, 3 5 3 6, 3 212 3 213 complex, 2 33, 2 84 creating, 2 7, 2 33 Upper Graticule pop up menu, defining, 3 205 3 209 3 84 3 88 11801C User Manual...
  • Page 440 Index Index...

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