Mohr CT100B Series Operator's Manual
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Mohr CT100B Series Operator's Manual

Tdr cable analyzers
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Operator's Manual:
CT100B Series
TDR Cable Analyzers
For Software Version 2.15
Part No.: CT100B-M-OM-008
CAGE Code: 4JEE1
Revision Date: 2018.12.10

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  • Page 1 Operator’s Manual: CT100B Series TDR Cable Analyzers For Software Version 2.15 Part No.: CT100B-M-OM-008 CAGE Code: 4JEE1 Revision Date: 2018.12.10...

  • Page 3: Copyright Notice

    MOHR. MOHR products are covered by U.S. and foreign patents, issued and pending. Information in this publication supersedes all previously published material. MOHR reserves the right to change product specifications or pricing at any time without notice.

  • Page 5: Manual Updates

    Manual Updates We at MOHR are always working to improve the written materials we offer to our valued customers. Since our last printing, there may have been minor updates to this manual. To view our most recent manual revision, open the accompanying CT Viewer 2 DVD, or visit us online at www.mohrtm.com.

  • Page 7: Warranty

    (1) year from the date of shipment unless otherwise stated in writing by MOHR. If any such product proves defective during this warranty period, MOHR, at its option, will either repair the defective product without charge for parts and labor, or will provide a replacement in exchange for the defective product.

  • Page 9: Contacting Mohr

    Contacting MOHR Phone +1-888-852-0408 Mail MOHR Test and Measurement LLC 2105 Henderson Loop Richland, WA 99354 E-mail Sales: sales@mohrtm.com Technical Support: techsupport@mohrtm.com www.mohrtm.com CT100B TDR Cable Analyzers Operator’s Manual...

  • Page 11: Table Of Contents

    3.1.6. Low Battery ..3.1.7. Nameplate ..Contacting MOHR 3.1.8. Discharge Warning Label 3.2. License Codes ...

  • Page 12: Table Of Contents

    Table of Contents 3.11.2. Relative Distance 4.1.2. Send Saved Traces over DTF Measurements . . . USB ... . 3.11.3. Multi-Segment Cable 4.1.3. Send Saved Traces Using DTF Measurements . . . Ethernet .
  • Page 13 Table of Contents B. Operating Performance Checks D.4. Calibration and Calibration In- B.1. General Information ..terval ....105 B.2. Required Equipment ..D.5.

  • Page 15: List Of Figures

    List of Figures 3.1. Example nameplate label found on back of a CT100B....11 3.2. Diagram of the CT100B front panel......12 3.3.
  • Page 16 List of Figures 3.43. TDR trace with impedance vertical units demonstrating vertical scale in ohms . . 58 3.44. Example layer peeling trace ....... 59 4.1.
  • Page 17 List of Tables 3.1. SCAN Button and Menu....... . . 16 3.2.

  • Page 19: General Information

    1. General Information 1.1. Product Description The MOHR CT100B TDR Metallic Cable Analyzer uses a form of closed-circuit radar known as time-domain reflectometry (TDR) to test cables for defects or “faults”. The instrument applies a fast rise time broadband step signal to the cable under test and then measures the reflected voltage at very short time intervals.

  • Page 20: Unpacking And Initial Inspection

    MOHR-authorized sales representative. 1.5. Repacking for Shipment In the event that the CT100B needs to be shipped to a MOHR-authorized service center for repair, calibration, or other service, contact MOHR for an RMA number. Affix a label to the outside of the shipping container indicating: •...

  • Page 21: Safety Summary

    2. Safety Summary The safety information presented in this brief summary is only intended for operators of the CT100B. Safety information relating to specific circumstances is present throughout this manual and is not necessarily present in this summary. Please read this manual in its entirety before using the CT100B and take note of safety information not included in this summary.

  • Page 22: Symbols In The Manual

    2. Safety Summary 2.3. Symbols in the Manual 2.4. Symbols on the CT100B 2.5. Static Charge Any cable or wire can carry a significant static electric charge that could damage the sensitive internal electronics of the CT100B. For this reason, it is essential to discharge the electrical conductors of any cable or device-under-test (DUT) by shorting them to each other or to earth ground before connection is made to the CT100B’s sampling circuitry.

  • Page 23: Fuses

    CAUTION: Use of any power source other than the supplied external power adapter(s) could damage the instrument and may void the War- ranty. Use only MOHR-approved accessories. WARNING: To reduce the risk of electric shock, disconnect all external cables before connecting the 24 VDC external power supply.

  • Page 24: Grounding The Ct100B

    2. Safety Summary 2.8. Grounding the CT100B When the CT100B is connected to the external AC adapter, the CT100B chassis, front panel USB, screen, and controls are grounded through the grounding conductor of the power cord. To avoid electrical shock, it is essential that the protective ground connection is present when operating the unit under AC power.

  • Page 25: Do Not Remove Covers Or Panels

    Contact your local authorities for safe disposal in your area, or you may return them to MOHR for recycling. WARNING: The battery pack must be replaced with MOHR pn: CT100- AC-B2700. Use of any other battery pack will damage the instrument and pose a danger of fire.

  • Page 27: Operating Instructions

    3. Operating Instructions 3.1. Overview If you would like a detailed explanation of TDR measurement theory and applications before using the CT100B, please read Section 5, TDR Measurement Theory. 3.1.1. Handling The CT100B is designed to meet the rigors associated with normal instrument use both in the field and on the benchtop.

  • Page 28: Caring For The Battery

    3. Operating Instructions 3.1.3. Caring for the Battery The CT100B has an intelligent battery-charging circuit that dynamically determines the optimum charge rate and reverts to low-level trickle charge when the battery is fully charged. Charging is automatic and there are no charge-length restrictions. The battery should be charged between 0 C and +45 C.

  • Page 29: Nameplate

    Each CT100B requires a unique license code to operate. Without the correct code, menus and buttons still function, but there will be no live trace displayed on the screen. The correct code for a particular device can be requested from MOHR. Installation instructions will be included with the license code.

  • Page 30: Front Panel Controls And Connectors

    3. Operating Instructions Otherwise, remove the front cover and turn on the power. You are ready to test cables using the most versatile and sophisticated portable TDR instrument on the market. 3.4. Front Panel Controls and Connectors The following numbered items describe the controls and connectors identified in the front panel diagram (Figure 3.2) and described in the text below.

  • Page 31: Rear Panel Connectors And Switches

    24. 24 VDC power adapter plug. The provided 24 VDC AC adapter plugs into this port. Only MOHR-approved positive center tip, 24V adapters may be used. 25. Client USB connection. Allows the CT100B to be connected to a host computer for data transfer and PC control.

  • Page 32: Keyboard Alternate Controls

    3. Operating Instructions Figure 3.3. Diagram of the rear panel of the CT100B/CT100HF. 3.6. Keyboard Alternate Controls If a keyboard is plugged into the front panel USB port, alternate hotkey controls are available for all front panel buttons and knobs. 1.

  • Page 33: Navigating Dialog Boxes

    3. Operating Instructions 6. Choose the Select menu option. The CT100B may prompt you to restart. If so, restart the unit and return to the Time menu. The CT100B is now set to the correct time zone. 7. Ensure the menu option for daylight savings reads Daylight Savings On, indicating that this setting is on.

  • Page 34: Menu Selections And Function Buttons

    3. Operating Instructions encounter during use. Many other features are available, however, and most of them are configurable by the user. These features are described in detail in the following sections. Figure 3.4. Screenshot showing typical features of the CT100B. 3.9.

  • Page 35: Math Menu

    3. Operating Instructions Table 3.1 (Continued) SCAN Button and Menu. Menu Selection Purpose/Action Hides the selected trace. (If trace was previously Hide Selected Trace saved, it can be recalled from the FILE menu; see Section 3.9.6) Initiates cable scan. Start Scan Switches between scan modes: Cursor/Snapshot Creates a new scan of the portion of trace between...
  • Page 36 3. Operating Instructions Table 3.2 (Continued) Math Menu Menu Selection Purpose/Action Changes the filter options that smooth the Pre-Filter Options aberrations of the base traces. Changes the filter options that limit the noise of the Post-Filter Options base traces. Other S Options When enabled, causes the Open, Short, and Load OSL Bases Visible...

  • Page 37: Select Button

    3. Operating Instructions Table 3.2 (Continued) Math Menu Menu Selection Purpose/Action Sets selected trace as the base (denominator) trace Set Base for math operations. Creates subtraction trace from selected trace and Difference base trace (Difference = Selected – Base). Creates first derivative trace from selected trace. 1st Derivative Toggles first derivative trace smoothing.

  • Page 38: Blue" Menu Button And Top-Level Menu

    3. Operating Instructions Table 3.3 (Continued) File Menu Menu Selection Purpose/Action Use to select a built-in cable type from the standard Reference Cable Types cable type library. Instrument settings change to reflect the cable Vp setting. Use to select, delete, or USB save a previously saved Cable Scan Records TDR trace.
  • Page 39 3. Operating Instructions Table 3.4 (Continued) MENU Button and Menus Menu Selection Purpose/Action Sets TDR trace horizontal sampling resolution (in Resolution picoseconds): A setting suitable for connector level detail for each Normal......of the cable length modes. Short is nominally 5.32 ps (<...
  • Page 40 3. Operating Instructions Table 3.4 (Continued) MENU Button and Menus Menu Selection Purpose/Action Toggles VR (Vertical Reference) mode on/off. Vert. Ref Off/On Performs VR calibration using short/open Set Vert. Ref. terminators. When setup is complete, a green vertical line indicates start of VR measurements. Adjusts VR calibration to use impedance matching Vert.
  • Page 41 3. Operating Instructions Table 3.4 (Continued) MENU Button and Menus Menu Selection Purpose/Action Deletes/restarts captured TDR trace envelope data. Reset Toggles between fill and probability density plot Fill Mode Off/On mode. Use fill mode to find magnitude of impedance change and highlighting fault location. Use probability density plot mode to find infrequent transient faults.
  • Page 42 3. Operating Instructions Table 3.4 (Continued) MENU Button and Menus Menu Selection Purpose/Action Set Ω/(unit) Pos. Set the position of the ohms/(unit distance) position to that of the active cursor. Reset all Ω/(unit) settings. Clear See Table 3.2: Math Menu. Math Settings See Meas.
  • Page 43 3. Operating Instructions Table 3.4 (Continued) MENU Button and Menus Menu Selection Purpose/Action Sets the inactivity timeout for power save mode Battery Power Save while the device is running on batteries. Sets the inactivity timeout for shutdown while the Battery Shutdown device is running on battery.
  • Page 44 Web Update Address software. Normally this setting should not be changed. Displays CPU information. Processor Contact information for MOHR. Contact Toggles Auto-Update on/off. With Auto-Update on, Auto Update On/Off the CT100B will automatically check to see if it is running the current software version and notify the user if a new version exists.

  • Page 45: Test Preparations

    3. Operating Instructions Table 3.4 (Continued) MENU Button and Menus Menu Selection Purpose/Action Show Time of Flight time measurements. The Time of Flight standard nanoseconds display shows electrical time for a pulse to reach a point and then return to the CT100B.

  • Page 46: Change Velocity Of Propagation (Vp)

    (red, top) and a controlled-impedance adapter (black, bottom). The clip lead adapter TDR trace is severely degraded. MOHR is able to supply controlled-impedance adapters for almost every type of cable and connector. Figure 3.5. Clip lead adapter (red, top) and controlled-impedance adapter (black, bottom) testing of 3 ft.

  • Page 47: Find An Unknown Velocity Of Propagation (Vp)

    3. Operating Instructions 3.10.3. Find an Unknown Velocity of Propagation (Vp) This method is used to find the Vp for cables under test where the Vp is unknown. It requires a sample cable that is of the same type that can be measured physically. 1.

  • Page 48: Sample Resolution

    3. Operating Instructions Figure 3.7. Use of the HORIZONTAL SCALE knob to improve Vp accuracy. Figure 3.8. Final Vp of the cable. 1. Press the M-FUNC button until “Smooth” shows up in the upper middle of the screen. 2. Rotate the M-FUNCTION knob until the desired level of trace smoothing is obtained. A comparison of a smoothed (1,024 trace average) TDR trace to an unsmoothed TDR trace at 0.7mρ...
  • Page 49 3. Operating Instructions Figure 3.9. Smoothed vs. unsmoothed traces at very small vertical scales (0.7mρ per vertical division). Section 3.11.5). The following TDR trace sample resolution settings are available in the MENU Resolution menu option: 1. Screen: Screen resolution (1 sample/pixel). Fastest trace, adequate for many routine cable testing tasks.

  • Page 50: Temperature Correction

    3. Operating Instructions Figure 3.10. A small fault in a long cable. This fault (red circle) in an approximately 800 ft (250 m) cable is from a 3 cm barrel connector (0.01% of cable length). The sampling of the Normal sample resolution setting ensures that the cable fault is displayed at this large horizontal scale (~50 cm/pixel).
  • Page 51 3. Operating Instructions Figure 3.11. AUTOFIT cable. The cable termination is a short. Figure 3.12. Vertical scale used to emphasize cable fault. 3.11.2. Relative Distance and DTF Measurements The CT100B displays the absolute distance from cable start and also the relative distance from the inactive cursor to the active cursor.

  • Page 52: Multi-Segment

    3. Operating Instructions Figure 3.13. A horizontally zoomed-in view of the cable fault with active (solid) cursor at the start of the fault (“toe” region) and inactive (dashed) cursor at the peak of the fault. The DTF measurement is highlighted (red circle). Figure 3.14.

  • Page 53: Ohms-At-Cursor

    3. Operating Instructions The CT100B includes multi-segment cable measurement capability designed to improve cable measurement accuracy in the setting of compound, multi-segment cables with differing Vp values. The CT100B allows the operator to break a TDR trace into cable segments, each of which can have its own Vp.

  • Page 54: Scan A Cable

    3. Operating Instructions Figure 3.16. Multi-segment cable segment with Vp of 0.850 (red circle). 3.11.5. Scan a Cable The CT100B can scan and save a trace into memory. CT100B scans differ from traditional TDR traces because they can be used to save detail at a much higher resolution than displayed on the screen.

  • Page 55: Select A Trace

    3. Operating Instructions Figure 3.18. Scan of a portion of a cable (red), zoomed-in vertically to show additional detail relative to the live trace (black). 3. Choose the Start Scan option from the menu to begin a cable scan. 4. Select the cable scan (see Section 3.11.6 below) and manipulate as needed. There are two types of scans: 1.

  • Page 56: Store A Trace

    3. Operating Instructions Figure 3.19. Selecting the live trace. Figure 3.20. Selecting a scanned trace. 3.11.7. Store a Trace A scanned trace can be stored for later recall: 1. Press the SCAN button. The Scan menu appears. 2. Press the SELECT button until the scanned trace to be stored is selected. 3.

  • Page 57: Load A Trace (Cable Records)

    3. Operating Instructions Figure 3.21. Selecting a difference trace. as FFTs) can also be stored with the same process. 3.11.8. Load a Trace (Cable Records) A stored trace can be loaded back to the screen: 1. Press the FILE button. The File menu appears. 2.

  • Page 58: Loading A Trace

    3. Operating Instructions Figure 3.22. Using the on-screen keyboard. Choose Hide Keyboard when finished. Then choose OK to save the trace with the name you entered. Figure 3.23. Loading a trace. CT100B TDR Cable Analyzers Operator’s Manual...

  • Page 59: Storing, And Deleting Traces

    3. Operating Instructions 3.11.9. Storing, Transferring, and Deleting Traces The CT100B has a large storage space, capable of holding thousands of trace scans. However, with continued use, CT100B storage will eventually fill up. Periodically, an effort should be made to clear stored traces from the device and free up storage space. 3.11.9.1.

  • Page 60: Mask Testing

    3. Operating Instructions 3.11.10. Mask Testing The CT100B is capable of performing mask testing on the currently displayed live TDR trace. The mask creates an area around the scanned trace that functions as a test limit for the live TDR trace. Any point of the trace that extends into the masked area will cause the background to turn red.
  • Page 61 3. Operating Instructions 5. Use Change Vertical Margin and Change Horizontal Margin to adjust the mask boundaries around the trace. 3.11.10.1. Storing a Mask The CT100B is capable of storing thousands of masks. To do this: 1. With a mask already displayed select File Masks menu.
  • Page 62 3. Operating Instructions 6. Use the M-FUNCTION knob to highlight the mask to be imported. 7. Press the Import Internal option. 8. The mask will be copied to internal storage of the CT100B. 3.11.10.4. Deleting a Mask Once masks are backed up to a computer, they can be deleted from the CT100B as follows: 1.

  • Page 63: Difference (Subtraction) Traces

    3. Operating Instructions Figure 3.26. Envelope Plot with Fill Mode, with the active cursor positioned at the fault location (red circle). Note that the black lines shown here to emphasize the “virtual arrow” do not actually appear on the instrument screen. Figure 3.27.

  • Page 64: Envelope Plot With Fill Mode, Showing The Range Of Impedance Values

    3. Operating Instructions Figure 3.28. Envelope Plot with Fill Mode, showing the range of impedance values at the cursor position (51.5–185.4 ohms, red circle) 3. Select the Math option from the Scan menu and choose Set Base. The selected trace will turn purple and is now a base trace for further Math functions.

  • Page 65: First Derivative (Slope) Traces

    3. Operating Instructions 3.11.13. First Derivative (Slope) Traces The first derivative trace can be used for two main purposes. First, the first derivative trace can be used to emulate the trace of a pulse-type TDR. Second, it may be used to remove the baseline deviation of long or lossy cables caused by resistive loss, so that vertical gain can be used to emphasize cable faults.

  • Page 66: Cable Resistive Loss Correction

    3. Operating Instructions 5. A set of terminators, both open and short, are included with the CT100B for calibration purposes. Attach these terminators to the CT100B when prompted to do so (pn: CT100-AC-ISS, CT100-AC-ISMM, CT100-AC-IBS, CT100-AC-IBMM). When the reference measurement is finished, cursor measurements will now appear in blue at the right hand of the screen, and the notification using vert.

  • Page 67: Return Loss

    3. Operating Instructions Use this correction to make more accurate impedance measurements on a length of cable. Since uniform cables tend to have a characteristic resistive loss per unit length or “dribble up”, one technique is to adjust the correction until the cable is as flat as possible. Another technique is to attach a known impedance reference, such as a resistive terminator, to the cable and adjust the ohms per unit length correction until the measured impedance reads the correct value.
  • Page 68 3. Operating Instructions 1. Prepare the CT100B by setting the trace resolution as desired by going to Resolution Fixed and using the M-FUNCTION knob. In general, a resolution of 1-2 ps is adequate to take advantage of the full bandwidth and frequency resolution of the instrument. Larger sample intervals can result in lower bandwidth resolution.
  • Page 69 3. Operating Instructions Figure 3.33. S return loss plot (orange) and TDR trace (red) of a 2.4 GHz WiFi antenna. The return loss is calculated on the portion of the TDR trace between the cursors 1. Create an S return loss plot using the procedure as described on page 49. 2.

  • Page 70: S 11 Return Loss Plot

    3. Operating Instructions 1. Create an S return loss plot using the procedure as described on page 49. 2. Select the S Options menu, then Phase Corr. Off menu option to toggle to Phase Corr. On. The S trace will update, although it might not look visually different, depending on the settings.

  • Page 71: Between Cursors Bracketing An Sma Barrel Adapter On The Tdr Trace

    3. Operating Instructions Figure 3.34. S between cursors bracketing an SMA barrel adapter on the TDR trace. Figure 3.35. S between cursors with tightened connector showing average return loss of -34.46 dB from 756 MHz to 3 GHz. 6. Toggle Restore Defaults to disregard the values set in the table, and to use those loaded from the CT100B internal storage.

  • Page 72: Smith Charts

    3. Operating Instructions Figure 3.36. S between cursors with loosened connector showing average return loss of -26.7 dB from 756 MHz to 3 GHz (7.7 dB excess return loss compared with the tightened connector in Figure 3.35). 3.11.19. Improving S-Parameter Measurements Note that testing short microwave cables directly from the test port may cause unacceptable noise due to the presence of secondary reflections in the TDR trace.

  • Page 73: Smith Chart Representation Of Open Fault

    3. Operating Instructions Figure 3.37. Using a phase stable cable to improve S-parameter measurements on short microwave cables. Use the phase stable cable (green arrow) and position the rightmost cursor to the left of the secondary reflections (red circle) occurring after the open or short at the end of cable under test (blue arrow) so that they are excluded.

  • Page 74: Normalized Tdr Traces

    3. Operating Instructions Figure 3.39. Smith chart representation of short fault (red arrow). Figure 3.40. Smith chart representation of a 50 ohm resistive load (red arrow). 3.11.21. Normalized TDR Traces This process creates a normalized TDR trace based on a calibrated S return loss trace.

  • Page 75: Vertical Units

    3. Operating Instructions Figure 3.41. Smith chart of reactive 200 ohm load showing effect of reactive impedance at higher frequencies. Cursor (red arrow) shows impedance value calculated at DC (0 MHz). information will be taken from the time-windowed S trace. Figure 3.42 shows a normalized TDR trace (blue) with a short fault in a 50 ohm cable.

  • Page 76: Layer Peeling (Dynamic Deconvolution) Traces

    3. Operating Instructions 2. Select Vert. Units to toggle through the different options. Example trace with impedance (ohms) as the vertical unit is shown in Figure 3.43. Note that the vertical scale is in ohms and the open fault at the end of the cable on the red (Impedance) trace shows nonlinear relationship between the reflection coefficient and the impedance described in Section 5.6.

  • Page 77: Fast Fourier Transform (Fft) Traces

    3. Operating Instructions Figure 3.44. Example layer peeling trace (yellow, bottom) versus live TDR trace (white, top). The layer peeled trace reduces the impedance error in the final cable segment (green arrows) by ~80%. 3.11.24. Fast Fourier Transform (FFT) Traces The CT100B can calculate FFT frequency domain information from live and scanned TDR traces.

  • Page 78: Remote Control

    3. Operating Instructions 3.11.26. Remote Control Using the accompanying CT Viewer™ 2 software, the CT100B can be operated by remote control. The remote control system allows the operator to manipulate traces and store movies of traces over time. Remote control only functions over Ethernet connections. It does not work when the CT100B is connected by USB only.

  • Page 79: User Configurations

    3. Operating Instructions 2. Select the Horiz. Units menu item to switch between the different unit options. All measurements and all traces are immediately updated to reflect the unit change. Time in nanoseconds (ns) is displayed separately. 3.11.28.2. Fine Vp Control By default, the CT100B displays three decimal places for Vp;...

  • Page 80: Take A Screenshot

    3. Operating Instructions 3.11.29.1. Save Configurations 1. Press the FILE button. The File menu appears. 2. Select the Config Entries menu item. The User Configurations library is displayed. 3. Select Add New to add a new User Configuration. The CT100B will prompt you for a configuration name and will save the current instrument configuration when you press OK.

  • Page 81: Ct Viewer

    4. CT Viewer The CT Viewer™ 2 host computer software allows users of the MOHR CT100B TDR Cable Analyzer to transfer, view, and manipulate cable scans that have been saved on their instruments. This software package allows the user to select scans from a stored database that can contain thousands of scans and compare, subtract, or find the first derivative of any of the...

  • Page 82: Send Saved Traces Using Ethernet

    4. CT Viewer 4.1.2. Send Saved Traces over USB 4.1.2.1. Setup USB Drivers on the Host Computer The USB drivers need to be set up only once for each computer. The USB drivers for the CT100B should have been installed with CT Viewer 2. It is possible to skip this step during the installation.
  • Page 83 4. CT Viewer Figure 4.1. Options under the Connect to CT Viewer menu. Figure 4.2. Selecting Manual Connect in the Connect to CT Viewer menu will bring up a server menu. 4.1.3.3. Manual Connection the First Time 1. From the server menu, Select Add PC . A window with various server settings appears. 2.

  • Page 84: Using Remote Control

    4. CT Viewer 2. Use the M-FUNCTION knob to highlight the connection for the computer. 3. Press Select. The CT100B will try to connect to the server. On success, a message appears in CT Viewer 2. 4.1.3.5. After Connecting 1. Go to the File menu in CT Viewer 2 and select Open Tester. A screen then appears that shows the serial number of the connected CT100B and a list of all traces saved on the CT100B.

  • Page 85: Tdr Measurement Theory

    5. TDR Measurement Theory The purpose of this section is to familiarize the operator with the basic theory of time-domain reflectometry measurement theory in preparation for using the CT100B instrument. 5.1. Time-Domain Reflectometry (TDR) TDR is a form of closed-circuit radar in which a transient test signal is injected into a device-under-test (DUT) such as a cable, and reflected voltages are measured over time to construct a TDR waveform or “trace”.

  • Page 86: Common Types Of Tdr Cable Faults

    5. TDR Measurement Theory The reflection coefficient is the ratio of the amplitude of the reflected portion of the test signal to the amplitude of the incident test signal. The reflection coefficient (Gamma, ) is related to the impedance change (Z) at a given point in a cable according to: Where Z is the impedance of the load (e.g., the device under test [DUT]) and Z is the source...
  • Page 87 5. TDR Measurement Theory Figure 5.2. A short cable fault shows a downward step edge at the location of the fault. long, shallow reflected rise caused by cable attenuation of high frequency components of the step pulse. Figure 5.3. An open cable fault at 824 ft. Faults with reactive components such as capacitance and inductance appear as either dips below or bumps above the characteristic impedance of the cable, depending on whether they are in series with the conductor or represent a fault to ground.

  • Page 88: Velocity Of Propagation (Vop, Vp)

    5. TDR Measurement Theory Figure 5.4. Normal SMA female barrel interconnect measuring 52.1 ohms. Figure 5.5. Comparison of typical SMA (red trace, bottom) and BNC (black trace, top) coaxial cable interconnects. velocity of propagation. The accuracy of the Distance-to-Fault measurement of a fault that appears beyond another fault is reduced.

  • Page 89: Distance-To-Fault (Dtf)

    5. TDR Measurement Theory it is important to be aware that Vp values for a given cable type may vary from manufacturer to manufacturer and from one manufacturing lot to the next even from the same manufacturer. In addition, cable aging due to temperature, radiation, or other environmental parameters may alter the original characteristic velocity of propagation for a given cable.

  • Page 90: Return Loss

    5. TDR Measurement Theory Figure 5.6. Relationship of impedance (ohms) to reflection coefficient (rho) for 50 ohm source impedance (marked by red circle). When impedance measurements are very important, accuracy can be improved using Vert. Ref. (page 47) and normalized TDR traces (page 56). 5.7.

  • Page 91: Vswr

    5. TDR Measurement Theory The CT100B is also able to measure complex frequency-specific S return loss and cable loss values such as those produced with Vector Network Analyzer (VNA) and Frequency Domain Reflectometer (FDR) equipment. This is discussed in further detail on page 76. Figure 5.7.

  • Page 92: Rise Time And Spatial Resolution

    5. TDR Measurement Theory Figure 5.8. Relationship of voltage standing wave ratio (VSWR) to reflection coefficient (rho). VSWR for 50 ohm load is shown by the red circle. relative reflection coefficient calculation. There are menu options in the Display menu to toggle the display of VSWR and ∆VSWR.

  • Page 93: Timebase/Cursor/Horizontal Resolution

    5. TDR Measurement Theory the difference between a 90 ps rise time TDR and an 800 ps rise time TDR (typical of low-cost TDR instruments) for characterizing two 1 cm long, 75 ohm faults spaced 1 cm apart on a 50 ohm cable.

  • Page 94: Frequency-Domain Measurements

    5. TDR Measurement Theory 5.11. Frequency-Domain Measurements 5.11.1. Scattering Parameters The scattering parameter or S-parameter approach to describing a device under test (DUT) assumes that a DUT is a black box network with N ports. The S-parameter matrix contains the complex reflection and transmission coefficients of the network, describing the amplitude and phase of reflected and transmitted values from each port in response to excitation of one or more of the ports.

  • Page 95: Return Loss (S )

    5. TDR Measurement Theory Figure 5.10. Comparison of S return loss of a 2.4 GHz WiFi patch antenna measured using a handheld VNA (Agilent® FieldFox N9927A, green) and TDR (CT100HF, blue), showing good agreement from DC to ~8.3 GHz. Note bandpass in the 2.4 GHz region. 5.11.2.

  • Page 96: Smith Charts

    5. TDR Measurement Theory Again, this relationship is valid if the cable is terminated with a short or open. One drawback to this technique is that the round-trip insertion loss reduces the length of cable that can be tested over a given bandwidth relative to a 2-port measurement because the attenuation of the test signal is doubled.

  • Page 97: Layer Peeling/Dynamic Deconvolution

    5. TDR Measurement Theory 5.14. Layer Peeling/Dynamic Deconvolution Layer peeling (or dynamic deconvolution) is a general method to solve the inverse scattering problem in partially reflective transmission lines such as cables. When applied to TDR traces, this method attempts to extract the underlying real reflection coefficients and impedance in the presence of multiple reflections caused by the presence of impedance discontinuities in the cable assembly under test.

  • Page 99: Options And Accessories

    6. Options and Accessories 6.1. Options Model CT100B (BNC) – self-grounding BNC test port Model CT100B (SMA) – stainless-steel SMA test port Model CT100HF – high-frequency sampler, stainless-steel SMA-type test port 6.2. Accessories 6.2.1. Service accessories (CT100B / CT100HF) Technical Manual, Printed CT100B-M-TSM-xxx* Technical Manual, Digital w/ CT Viewer™...

  • Page 100: Standard Sma Accessories - Ct100B (Sma), Ct100Hf

    6. Options and Accessories 6.2.3. Standard SMA Accessories – CT100B (SMA), CT100HF SMA 50 ohm 36 in. Reference Cable CT100-AC-W536-S SMA 50 ohm Terminator CT100-AC-ER50-S SMA Male to Male Adapter CT100-AC-ISMM Connector, SMA female to BNC male CT100-AC-ISFBM Connector, SMA male to BNC female CT100-AC-ISMBF Connector, SMA Female Short CT100-AC-ISSF...

  • Page 101: Electrical Specifications

    A. Specifications A.1. Electrical Specifications Characteristic Specifications Notes Reflected rise time, CT100B 10-90% 150 ps typ, 200 ps max 10 to 90%, into 50Ω Reflected rise time, CT100B 20-80% 100 ps typ, 150 ps max 20 to 80%, into 50Ω Reflected rise time, CT100HF 10-90% 100 ps typ, 130 ps max 10 to 90%, into 50Ω...

  • Page 102: Environmental Specifications

    DC power supply 24 VDC, 2.5 A, positive 500 VDC isolation from tip. Use only the test port. MOHR-approved power supply. Battery pack 12 NiMH AA cells, fused Pack may wear out over at 2.5 A time.

  • Page 103: Certifications And Compliances

    A. Specifications A.3.2 Dimensions Height 10.9 cm (4.28 in.) Width w/ handle 29.2 cm (11.50 in.) Width w/o handle 26.2 cm (10.30 in.) Depth w/ cover 17.5 cm (6.90 in.) Depth, handle extended 27.9 cm (11.00 in.) A.4. Certifications and Compliances A.4.1 The CT100B and CT100HF comply with all applicable EU directives.

  • Page 105: Operating Performance Checks

    NOTE: If a CT100B fails any Operator Performance Check, it should be serviced by a qualified repair facility. B.2. Required Equipment Table B.1. Required Performance Check Equipment for CT100B Item MOHR part number Precision 50 Ω terminator CT100-AC-ER50-S Connector, SMA female to BNC male CT100-AC-ISFBM 50 Ω...

  • Page 106: Getting Ready

    B. Operating Performance Checks Table 3.4 (Continued) Required Calibration Equipment Item MOHR part number Connector, SMA male to BNC female CT100-AC-ISMBF Shorting cap CT100-AC-ISS 50 Ω 36 in. reference cable CT100-AC-W536-S Additionally, a device capable of taking accurate pulse measurements with documented calibration will be required, and, if working with a CT100B [BNC], an open terminator will be needed.
  • Page 107 B. Operating Performance Checks B.4.3 Pulse Amplitude Check 1. Pulse amplitude measurement should be taken with a device that can accurately measure frequency, pulse width, period, and amplitude. 2. Set the device input impedance to 50 ohms. 3. Connect one end of the 36 in. reference cable to a capable pulse measurement device and the other end of the 36 in.
  • Page 108 B. Operating Performance Checks 5. Measure the pulse frequency coming off the front panel cable connector. The averaged pulse frequency should be 250.0 0.2 kHz for Short, 50.00 0.04 kHz for Medium, and 12.50 0.02 kHz for Long. 6. Repeat pulse width check for Medium and Long settings. B.4.7 Sequential Sampling Rate Check The sequential sampling rate is the reciprocal of the pulse repetition time.
  • Page 109 B. Operating Performance Checks Position a cursor at the most far left position. The absolute distance measurement for the cursor is the lower limit for cursor readout range. This number should be less than -1 ft. (-0.3 m). B.4.13 Cursor Readout Resolution Check 1.
  • Page 110 B. Operating Performance Checks B.4.18 Horizontal Scale Check 1. From the Main menu, set Cable Len to “Long”. 2. Using the M-FUNC button and M-FUNCTION knob, set Vp to 1.00. 3. Turn the HORIZONTAL SCALE knob counter clockwise. Horizontal scale should increase beyond 61 m/div or 200 ft./div.

  • Page 111: Operator Troubleshooting

    C. Operator Troubleshooting C.1. General Information Use this troubleshooting guide when there is a problem with a CT100B or to assist with problem identification. This will help you to determine if the instrument should be repaired or is acceptable to continue using. Any time one of the internal thermal fuses actuates with an audible click, indicating thermal overload, turn off...
  • Page 112 C. Operator Troubleshooting C.3.1 Functional Block Diagram 24V DC Charging Internal 12 Cell Client USB, from AC adapter NiMH Battery Pack Ethernet CT100-AC-PS CT-100-AC-B2700 DC Power, Temperature Ethernet, DC Power Back Panel Assembly Client USB CT209B Analog Power W1W5C1 Ethernet W2W6C1, Client USB W2W6C3, Serial Port +5V Digital...
  • Page 113 Time Clock FAIL Verification (C.3.9) PASS Perform File IO FAIL Verification (C.3.10) PASS Return to MOHR for Return to MOHR for factory Diagnosis and factory Diagnosis and Device is in working Repair Repair order CT100B TDR Cable Analyzers Operator’s Manual...
  • Page 114 C. Operator Troubleshooting C.3.3 External DC Diagnostics Start DC Power Supply Diagnostics Plug 24 volt DC Replace power power supply into a supply wall socket (CT100-AC-PS) Change to a working Does the AC AC wall outlet outlet work? Verify the power Does the green light on the supply is firmly power supply come on?
  • Page 115 C. Operator Troubleshooting C.3.4 Startup Diagnostics Start Is the screen blank/white and unchanging for >1 minute? Did the MOHR splash screen appear? Did a progress bar appear? Is the progress bar frozen or reporting an error? Is the device locking up after...
  • Page 116 C. Operator Troubleshooting C.3.5 Front Control Verification Start Front Control Diagnostics Press the Blue Menu Button Choose Settings -> Does the main Diagnostics menu menu appear? item. Choose “Front Panel Check” menu item Does The front panel diagnostics screen appear? Turn each knob left and right and press each button except...
  • Page 117 C. Operator Troubleshooting C.3.6 Analog Diagnostics Start Trace Diagnostics Install a valid license Did a message appear file by following the on the device stating instructions in that the license was out Appendix C of the of date or invalid? manual and restart the device Did a message appear...
  • Page 118 C. Operator Troubleshooting C.3.7 TDR Trace Verification Start TDR Pulse Diagnostics Return to Main Menu and navigate to SettingsàDiagnostics and select Analog. Attach a shorted terminator and press OK Using an oscilloscope, verify the TDR pulse Did all tests characteristics as displayed pass? described in “Operator Performance Checks”...
  • Page 119 C. Operator Troubleshooting C.3.8 USB Client and Ethernet Verification START Connect back USB to known working PC with CT Viewer 2 installed. Does the PC recognize the device? Connect known working Ethernet cable that is connected to a network to the device.
  • Page 120 C. Operator Troubleshooting C.3.9 Real Time Clock Verification Start Navigate to Main Menu Settings Info Time Change the date and time and select Turn power off, then restart the device Does the device display the new time? Reset Correct Date and Time FAILED PASSED...
  • Page 121 C. Operator Troubleshooting C.3.10 File IO Verification START Verify that only the live TDR trace is on the display. Enclose the leading edge of the live trace with the two cursors and generate a cursor scan. See section 3.11.5 for instructions on creating a scan. While in the SCAN menu select SAVE.

  • Page 122: Parts List

    C. Operator Troubleshooting C.4. Parts List Table C.1. Parts List Subassembly Item Part No. Qty. Description CT100B CT100B CT100B TDR Cable Tester CT291 Rear Housing CT292 Front Cover Front Panel Assembly CT290B LCD display, front control board, switches, cables, and knobs W2W7C1 Digicomp-video PCB FFC 40 pin flat-flex...

  • Page 123: Maintenance And Service Instructions

    D. Maintenance and Service Instructions D.1. Cleaning and Lubrication Ensure that the CT100B power is off before cleaning. Clean the CT100B with a damp cloth. Clean the LCD screen with LCD screen cleaner or optical lens cleaner. Do not use any powerful solvents when cleaning the CT100B.

  • Page 124: Install Ct100B License

    Note: If multiple license files are on a USB flash drive, the CT100B will reject the file. Make sure the intended license file is the only MOHR license file on the drive. 1. Copy the file to an empty USB flash drive. (Do not change the file name.) 2.

  • Page 125: P Of Common Cables

    E. V of Common Cables E.1. Cable Types Commonly encountered cable designations, along with their associated characteristic impedances and typical Vp values, are listed below. A more complete listing is stored in the CT100B’s internal memory. Note that the actual Vp of a given cable can vary by manufacturer, manufactured lot, cable age and condition, whether it is flat or coiled on a roll, and other variables.

  • Page 126: Rg Standards

    E. V of Common Cables E.3. RG Standards Table E.2. Vp of RG Standards Designation (ohms) RG-6/U 0.66 RG-6/UQ 0.66 RG-8/U 0.66 RG-9/U 0.66 RG-11/U 0.66 RG-58/U 0.66 RG-59/U 0.66 RG-62/U 0.84 RG-62A 0.84 RG-174/U 0.84 RG-178/U 0.69 RG-179/U 0.67 RG-213/U 0.66 RG-214...

  • Page 127: Commercial Designations

    E. V of Common Cables E.5. Commercial Designations Table E.4. Vp of Commercial Designations Designation (ohms) H155 0.79 H500 0.82 LMR-200 0.83 HDF-200 0.83 CFD-200 0.83 LMR-400 0.85 HDF-400 0.85 CFD-400 0.85 LMR-600 0.87 LMR-900 0.87 LMR-1200 0.88 LMR-1700 0.89 E.6.

  • Page 129: Glossary

    Glossary Aberrations Imperfections or undesired variations in a signal. For example, aberrations in a TDR’s excitation signal are the result of the finite switching speed of the instrument’s electronics and cause it to deviate from a perfect step signal. AC Alternating current, a method of delivering electrical energy by periodically changing the direction of the electric field in a conductor.
  • Page 130 Glossary reflected back by the load. The dB vertical scale on the CT100B refers to the amount of voltage gain the instrument applies to the signal before displaying it. For example, when the instrument is amplifying the voltage by a factor of 100, this indicator would read: verticalscale = 20 log (100) = 40dB.
  • Page 131 Glossary Layer Peeling A mathematical technique for reducing multiple reflections in a TDR trace. TDRs measure reflections from changes in impedance, but if there are multiple impedance changes, then the reflections from one will partially reflect back off of another. Reducing the effect of these extra reflections improves the measurement of the impedance changes.
  • Page 132 Glossary Resolution For a given parameter, the smallest increment that can be measured or displayed. In the setting of TDR, resolution may refer to time base resolution, which describes the smallest increment of time used by the pulser-sampler system to produce signals and measure reflections, or spatial resolution, which is dependent on the system rise time and determines the ability of the TDR to separate two closely spaced cable faults.
  • Page 133 Glossary CT100B can emulate this protocol. Stability The change in the accuracy of a measurement or piece of test equipment over a period of time such as the calibration interval. Stability may also refer to changes in accuracy related to a specific environmental influence such as vibration, temperature, or humidity. TDR Acronym for Time-Domain Reflectometer or Reflectometry.

  • Page 135: Index

    Index .csv, 41 V2, 13 V3, 13 AC power, 5 V4, 13 adapter plugs voltage, 9 cable fault add server, 65 common types, 68 assistant mode, 66 distance to fault, 32 auto-update, 26 cable loss (S ), 77 cable resistance correction, 48 balun cable scans, 36 see Vert.
  • Page 136 Index difference trace, 45 knob display HORIZONTAL POSITION, 12 features, 15 HORIZONTAL SCALE, 12 distance to fault, 32 M-FUNCTION, 13 VERTICAL POSITION, 12 connecting, 27 VERTICAL SCALE, 12 dynamic deconvolution layer peeling create trace, 58 create trace, 58 theory, 79 theory, 79 electric shock, 6 license code, 11, 106...
  • Page 137 Index power requirements Smith chart AC power, 1 creating, 54 external AC power adapter, 1 theory, 78 soft keyboard, see keyboard internal power, 1 print screen, 20 specifications, 83–85 static charge reflected rise time, 83 damage to BNC connector, 13 reflection coefficients, 67 grounding the BNC connector, 6 theory, 67...
  • Page 138 Index unpacking, 2 send traces, 64 USB drive save waveform, 63 velocity of propagation AUTOFIT/HELP button, 29 changing the value of, 28 finding an unknown, 29 for common cable types, 107 load a cable type’s Vp, 60 load and save custom cable types, 60 multisegment cable, 34 theory, 70 Vert.

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