Related Manuals for Tektronix SD-24
Summary of Contents for Tektronix SD-24
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- Page 2 User Manual SD-24 TDR/Sampling Head 070–7052–02 This document applies for firmware version X.XX and above. Warning The servicing instructions are for use by qualified personnel only. To avoid personal injury, do not perform any servicing unless you are qualified to do so.
- Page 3 Instrument Serial Numbers Each instrument manufactured by Tektronix has a serial number on a panel insert or tag, or stamped on the chassis. The first letter in the serial number designates the country of manufacture. The last five digits of the serial number are assigned sequentially and are unique to each instrument.
- Page 4 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.
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Page 6: Table Of Contents
Table of Contents List of Figures ..........List of Tables . - Page 7 Table of Contents Contents...
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Page 8: List Of Figures
List of Figures Figure 1: SD 24 Sampling Head Block Diagram ....Figure 2: Sampling Head Compartments in an 11801B and a CSA 803A . - Page 9 List of Figures Contents...
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Page 10: List Of Tables
List of Tables Table 1: Acquisition Electrical Specifications ....Table 2: Step Generator Electrical Specifications ....Table 3: TDR Electrical Specifications . - Page 11 List of Tables Contents...
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Page 12: Introduction
Introduction The SD 24 TDR/Sampling Head is a high performance sampling head that can be installed in the 11800 Series Digital Sampling Oscilloscopes, the SM 11 Multi Channel Unit, and the CSA 803 Series Communications Signal Analyzers. The SD 24 TDR/Sampling Head provides the following features: Two independent channels with signal acquisition and step generator capabilities. -
Page 13: Figure 1: Sd 24 Sampling Head Block Diagram
Introduction Step Generator 50 W Acquisition System TDR Drive Strobe Drive To/from Strobe Mainframe Strobe Sense Generator Acquisition Step Variable System Generator Delay 50 W Figure 1: SD 24 Sampling Head Block Diagram The strobe sense signal is a part of the strobe signal returned to the main frame. -
Page 14: Safety
Safety Terms in Manuals CAUTION statements identify conditions or practices that could result in damage to the equipment or other property. WARNING statements identify conditions or practices that could result in personal injury or loss of life. Terms on Equipment CAUTION indicates a personal injury hazard not immediately accessible as one reads the marking, or a hazard to property including the equipment itself. - Page 15 Safety Do Not Operate in Explosive Atmospheres The sampling head provides no explosion protection from static discharges or arcing components. Do not operate the instrument in an atmosphere of explosive gases. SD 24 User Manual...
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Page 16: Electrostatic Discharge
Electrostatic Discharge To prevent electrostatic damage to the instrument and sampling heads, follow the precautions described in this manual and other manuals accom panying your sampling head and instrument. Acquisition circuitry in the sampling heads is very susceptible to damage from electrostatic discharge and from overdrive signals and DC voltages. - Page 17 Electrostatic Discharge SD 24 User Manual...
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Page 18: Connector Care
Connector Care The front of the sampling head has two precision 3.5 mm connectors, one for each channel. They are for attaching the signal cable or the device under test. These are high precision connectors with a closer mechanical tolerance than standard SMA cables. - Page 19 Connector Care SD 24 User Manual...
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Page 20: Installing The Sampling Head
Installing the Sampling Head The SD 24 TDR/Sampling Head fits into the front panel of a compatible instrument, such as the 11801 Series Digital Sampling Oscilloscopes or CSA 803 Series Communications Signal Analyzers. Figure 2 shows the front panel of an 11801B Digital Sampling Oscilloscope and a CSA 803A Commu nications Signal Analyzer and the locations of the sampling head compart ments. -
Page 21: Figure 3: Installing A Sampling Head In An Instrument
Installing the Sampling Head With the ON/STANDBY switch set to STANDBY, place the sampling head in a compartment and slowly push it in with firm pressure. Once the sampling head is seated, turn the lock down screw to tighten the sampling head into place. -
Page 22: Using The Sampling Head
Using the Sampling Head Front Panel Figure 4 shows the front panel of the SD 24 TDR/Sampling Head and identi fies the buttons, lights, and connectors. Lock Down Screw SELECT CHANNEL Button Channel Indicator Light (Yellow) Top Channel Signal Connector TDR ON Light (Red) Bottom Channel Figure 4: Sampling Head Front Panel... -
Page 23: Connecting Signals
Using the Sampling Head Connecting Signals The signal connector for each channel is used to connect signals for sam pling and to output TDR steps. These are precision 3.5 mm connectors, which are mechanically compatible with the SMA standard. Input impedance is 50 W. -
Page 24: Instrument/Sampling Head Interaction
Using the Sampling Head Instrument/Sampling The SD 24 TDR/Sampling Head is a part of a larger instrument system. Most of the SD 24 functions are controlled automatically by the mainframe instru Head Interaction ment. These include such things as vertical scaling and horizontal sampling rate. -
Page 25: Commands From The Mainframe Front Panel
Using the Sampling Head Commands From the Mainframe Front Panel The Waveform major menu lets you access the Sampling Head Fnc's pop up menu. Both of these are shown in Figure 5. You first select the channel you want to set in the Selected Channel section of the pop up menu. -
Page 26: Programmer Interface Commands
Using the Sampling Head Programmer Interface Commands Commands from a remote computer to the 11800 Series or CSA 803 Series instrument (via an IEEE-488 or RS 232 C interface) can control the sam pling head functions. These commands are described below. For these commands, <alpha>... - Page 27 Using the Sampling Head SD 24 User Manual...
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Page 28: Adjusting Parameters
Adjusting Parameters To get the best performance from your SD 24 TDR/Sampling Head, you may need to adjust sampling head parameters. These parameters affect how the sampling head acquires signals and affect the accuracy of the resulting trace. Typically, you may want to adjust sampling head parameters whenever you have moved the sampling head to another slot or if the ambient temperature has changed more than "5_ C since the parameters were last adjusted. -
Page 29: Stored Parameters
Adjusting Parameters Stored Parameters The SD 24 contains nonvolatile memory that stores two values, the factory default value and the user constant, for each of the above parameters. These values are always remembered in the sampling head, even if you remove the sampling head from the instrument. -
Page 30: Loop Gain
Adjusting Parameters Loop Gain Loop gain determines the sampling head's ability to accurately follow an input voltage change that occurs between two adjacent samples. How accurately the sampling head output follows the input signal is termed the dot transient response. When loop gain is unity (1), the value of the first sample acquired after an input voltage change accurately reflects the voltage change, indicating a good dot transient response. -
Page 31: Adjusting Loop Gain
Adjusting Parameters Adjusting Loop Gain For the 11800 Series and CSA 803 Series, you can adjust loop gain auto matically or manually from the Enhanced Accuracy menu. If you prefer to adjust loop gain manually, the 11800 Series and CSA 803 Series also pro vide a divide by two feature. -
Page 32: Offset Null
Adjusting Parameters Offset Null The offset null adjustment removes unwanted DC offset that may be present in the sampling head. This adjustment effectively zeroes" the sampling head so that a 0 V amplitude input signal delivers a 0 V output. If offset null is not adjusted correctly, measurements taken at the mainframe will be incorrect. -
Page 33: Tdr Amplitude
Adjusting Parameters TDR Amplitude The SD 24 has an internal step generator that is used with the acquisition channel to let you perform TDR measurements. You can adjust the ampli tude of the TDR step. The TDR step amplitude setting is highly stable and insensitive to tempera ture variations. -
Page 34: Taking Tdr Measurements
Taking TDR Measurements This section describes how to use the SD 24 to perform time domain reflectometry (TDR) measurements. TDR Step Generation Both channels in the SD 24 TDR/Sampling Head have a step generator which gives both channels TDR measurement capabilities. You can use the outputs of both generators to perform differential and common mode TDR measurements. -
Page 35: Operation Into A Short Circuit
Taking TDR Measurements 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 36: Operation Into An Open Circuit
Taking TDR Measurements Operation Into an Open Circuit Initially, the diode switch is conducting. Since the step generator output is open, the resistance to ground at the acquisition point is 50 W (because of the internal 50 W impedance). The -10 mA current source places -500 mV at the acquisition point as a starting condition. -
Page 37: Example: Taking Tdr Measurements
Taking TDR Measurements Example: This example demonstrates the TDR feature of the SD 24 sampling heads. TDR is a method of examining and measuring a network or transmission line Taking TDR by sending a step into the network and monitoring the reflections. Measurements For this example you will need a instrument mainframe with at least one SD 24 installed. -
Page 38: Figure 12: Tdr Step And Reflection
Taking TDR Measurements Step 7: Adjust the display sizes and positions to show a trace similar to that shown in Figure 12. The vertical ( ) and horizontal ( ) icons will let you make fine adjustments. NOTE Leave at least one division of baseline trace to the left of the first rise. -
Page 39: Changing Graticule Units For Tdr
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 at which signals pass through your network or transmission line. -
Page 40: Example: Differential And Common Mode Tdr
Taking TDR Measurements Example: The SD 24 TDR/Sampling Head is able to perform differential and common mode TDR measurements. As described earlier, the sampling head has two Differential and sampling input channels and two independent step generators. Common Mode TDR The step generator output for each channel is selectable for positive or negative polarity and amplitude. -
Page 41: Tdt Measurements
Taking TDR Measurements When the TDR steps on the two channels are opposite (one positive and one negative), you can now define a trace that represents the true differen tial signal by touching the DefTra icon and touching Mainframe (11801 Series only), 1, -, Mainframe (11801 Series only), 2, Enter TDT Measurements You can make forward and reverse Time Domain Transmission (TDT) meas... -
Page 42: More About Tdr Measurements
Taking 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 the device under test at the point where the cables connect to the device. - Page 43 Taking TDR Measurements SD 24 User Manual...
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Page 44: Specifications
Specifications Table 1: Acquisition Electrical Specifications Characteristics Specifications Bandwidth 20 GHz typical Sampling Repetition Rate Maximum 200 kHz Minimum 100 Hz Rise Time 17.5 ps or less, 10% to 90% Aberrations 10 ns to 20 ps before step "3% or less, typical t300 ps after step +10%, -5% or less, typical 300 ps to 5 ns after step... -
Page 45: Table 2: Step Generator Electrical Specifications
Specifications Table 1: Acquisition Electrical Specifications (Cont.) Characteristics Specifications Isolation Between Channels v1% p p voltage transmission from channel driven with 067-1338-00 to quiescent channel Time Coincidence Between Channels Accuracy 10 ps Stability <0.2 ps/_ C Table 2: Step Generator Electrical Specifications Characteristics Specifications Maximum Repetition Rate... -
Page 46: Table 4: Environmental And Mechanical Specifications
Specifications Table 4: Environmental and Mechanical Specifications Characteristics Specifications Weight 314 grams (11 oz) Height 71.05 mm (2.9 in) Width 23.28 mm (0.95 in) Depth 91.39 mm (3.8 in) Ambient Temperature Operating 0_ C to 50_ C (32_ F to 122_ F) Non operating -40_ C to 75_ C (-40_ F to 167_ F) Altitude... - Page 47 Specifications SD 24 User Manual...
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Page 48: Glossary
Glossary Autoset A means of letting the instrument mainframe set itself to provide a stable and meaningful display of a given trace. Baseline Correction The process of maintaining the displayed vertical placement of a trace, correcting for changes in the signal levels that would ordinarily move the trace up or down. - Page 49 Glossary Setting The state of the front panel and system at a given time. Smoothing Processing applied by the sampling head prior to the digitization of a trace, to reduce apparent noise. With smoothing, the sampling head samples the signal eight times instead of once, and the average of the samples is then used by hardware measurements and the digitizing circuitry.
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Page 50: Index
Index Acquisition Factory defaults, 18 Sampling head parameters, 17, 18, 19, 20, 21, 22 circuitry, 1, 2 Front panel loop gain, 19, 20 rise time, 1, 2 buttons, 11, 12 offset null, 21 ASCII interface commands, 15 connectors, 11, 12 TDR amplitude, 22 lights, 11, 12 SELECT CHANNEL button, 11, 12,... - Page 51 Index Index...