CT100B TDR Cable Analyzer Operator'

Operator’s Manual:
CT100B Series
TDR Cable Analyzers
For Software Version(s) 2.6
Part No.: CT100B-M-OM-004
CAGE Code: 4JEE1
Revision Date: 04/25/2017
Copyright Notice
Copyright © 2008-2017 MOHR Test and Measurement LLC (MOHR). All rights reserved.
Reproduction of this manual in print and electronic form is authorized for U.S. Government purposes only. This
manual may not be reproduced, distributed, transmitted, displayed, published, or broadcast in any form or medium by
any other party without written permission from 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.
This manual contains trademarks and material copyrighted or patented by MOHR and other third parties. All marks,
copyrights, trade secrets, and patents should be considered to be the property of their respective owners and all rights
are reserved. Nothing contained herein shall be construed by implication, estoppels, or otherwise as granting to the
user a license under any copyright, trademark, patent, or other intellectual property right of MOHR or any third party.
Statutory notice contained herein represents trademark status in the United States.
MOHR Test and Measurement LLC, 2105 Henderson Loop, Richland, WA 99354 USA
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 DVD, or visit us online at
www.mohrtm.com. (Please click on Products, CT100, Downloads).
CT100B TDR Cable Analyzer Operator's Manual
i
Warranty
Purchase and/or use of this product signifies your agreement to the terms of this Warranty. MOHR Test and
Measurement LLC (MOHR) warrants that this product will be free from defects in materials and workmanship for a
period of one (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. MOHR’s liability and
Buyer’s remedies under this Warranty shall be limited solely to repair, replacement, or credit,
In order to obtain service under this Warranty, customers must notify MOHR of the defect before the expiration of the
warranty period and make suitable arrangements for the performance of service. Customers shall be responsible for
packaging and shipping the defective product to MOHR with shipping charges prepaid. Customers shall be
responsible for paying all return shipping charges, duties, taxes, and other charges for units returned to any location.
Customers shall be responsible for removing and reinstalling the equipment and for any decontamination procedures
that may be necessary in preparation for shipment.
THIS WARRANTY IS EXCLUSIVE AND IN LIEU OF ANY OTHER WARRANTIES, EXPRESSED OR IMPLIED,
INCLUDING BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. MOHR SHALL NOT BE LIABLE UNDER ANY CIRCUMSTANCES FOR
CONSEQUENTIAL OR INCIDENTAL DAMAGES, INCLUDING BUT NOT LIMITED TO LABOR COSTS OR LOSS
OF PROFITS, DAMAGE TO PERSONS OR PROPERTY ARISING IN CONNECTION WITH THE USE OF OR
INABILITY TO USED PRODUCTS PURCHASED FROM MOHR.
Specific limitations of this Warranty:
This Warranty only applies to normal and reasonable use of this product. Damage to this product resulting
from improper use, the determination of which is solely at the discretion of MOHR, is specifically excluded
from this Warranty.
Any electrical damage to this product resulting from connection of a cable or device carrying a static
electrical charge to the front panel BNC connector or SMA connector without first properly grounding the
conducting elements of the cable or device is specifically excluded from this Warranty.
Any Electrical damage to this product resulting from connection of a cable or device carrying an electrical
signal or other non-zero electrical potential relative to earth ground to the front panel BNC connector or SMA
connector is specifically excluded from this Warranty.
ii
CT100B TDR Cable Analyzer Operator's Manual
Contacting MOHR
Phone
+1-888-852-0408
Mail
MOHR Test and Measurement LLC
2105 Henderson Loop
Richland, WA 99354
USA
E-mail
info@mohrtm.com
Web
www.mohrtm.com
CT100B TDR Cable Analyzer Operator's Manual
iii
Table of Contents
Copyright Notice ........................................................... i
Manual Updates ............................................................ i
Warranty ...................................................................... ii
Contacting MOHR ........................................................iii
Phone ..........................................................................iii
Mail ..............................................................................iii
E-mail ...........................................................................iii
Web..............................................................................iii
Table of Contents ........................................................ v
List of Figures .............................................................vii
1 General Information ................................................ 1
1.1 Product Description ....................................... 1
1.2 Power Requirements .................................... 1
1.3 Options and Accessories .............................. 1
1.4 Unpacking and Initial Inspection ................... 1
1.5 Repacking for Shipment ................................ 2
2 Safety Summary ..................................................... 3
2.1 Terms in the Manual ..................................... 3
2.2 Terms on the Product ................................... 3
2.2.1
DANGER ............................................. 3
2.3 Symbols in the Manual .................................. 3
2.4 Symbols on the Product ................................ 4
2.5 Static Charge ................................................ 4
2.6 Fuses ............................................................ 4
2.7 AC Power Source ......................................... 5
2.8 Grounding the CT100B ................................. 5
2.9 Danger Arising From Loss of Ground ........... 6
2.10 Explosive Atmospheres ................................ 6
2.11 Do Not Remove Covers or Panels ................ 6
2.12 Connecting Cables to the Test Port .............. 6
2.13 Battery Replacement and Disposal .............. 7
3 Operating Instructions ............................................. 9
3.1 Overview ....................................................... 9
3.1.1
Handling .............................................. 9
3.1.2
Powering the CT100B ......................... 9
3.1.3
Caring for the Battery .......................... 9
3.1.4
Charging and Power Status .............. 10
3.1.5
Batteries and Long-Term Storage ..... 10
3.1.6
Low Battery ....................................... 10
3.2 License Codes ............................................ 10
3.3 Preparing to Use the CT100B ..................... 11
3.4 Front Panel Controls and Connectors ........ 11
3.5 Rear Panel Connectors and Switches ........ 13
3.6 Keyboard Alternate Controls ....................... 13
3.7 Setting up the CT100B ................................ 14
3.8 Display Features ......................................... 15
CT100B TDR Cable Analyzer Operator's Manual
3.9
Menu Selections and Function Buttons ...... 15
3.9.1
M-FUNC Button ................................. 15
3.9.2
SCAN Button and Menu .................... 16
3.9.3
SELECT Button ................................. 18
3.9.4
AUTOFIT / HELP Button ................... 18
3.9.5
CURSOR Button ............................... 18
3.9.6
FILE Button and Menu ...................... 19
3.9.7
MENU Button and Top-Level Menu .. 19
3.10 Test Preparations ........................................ 26
3.10.1 Connecting to the Cable or DeviceUnder-Test (DUT) ............................. 26
3.10.2 Change Velocity of Propagation (Vp)....
.......................................................... 27
3.10.3 Find an Unknown Velocity of
Propagation (Vp) ............................... 27
3.10.4 Smooth Settings ................................ 29
3.10.5 Sample Resolution ............................ 30
3.10.6 Temperature Correction .................... 31
3.11 Test Procedures .......................................... 31
3.11.1 Measure Distance-to-Fault (DTF) ..... 31
3.11.2 Relative Distance and DTF
Measurements .................................. 32
3.11.3 Multi-Segment Cable DTF
Measurements .................................. 33
3.11.4 Ohms-at-Cursor Measurements ....... 34
3.11.5 Scan a Cable ..................................... 34
3.11.6 Select a Trace ................................... 35
3.11.7 Store a Trace .................................... 36
3.11.8 Load a Trace (Cable Records) .......... 37
3.11.9 Storing, Transferring, and Deleting
Traces ............................................... 38
3.11.10 Transient / Intermittent Fault Detection .
.......................................................... 39
3.11.11 Difference (Subtraction) Traces ........ 41
3.11.12 First Derivative (Slope) Traces ......... 42
3.11.13 Second and Higher Order Derivative
Traces ............................................... 42
3.11.14 Vertical Reference (Vert. Ref.)
Calibration ......................................... 43
3.11.15 Cable Resistive Loss Correction ....... 43
3.11.16 Return Loss (S11) Traces .................. 45
3.11.17 Return Loss (S11)Options .................. 46
3.11.18 Improving S-Parameter Measurements
.......................................................... 49
3.11.19 Smith Charts ..................................... 50
3.11.20 Normalized TDR Traces.................... 52
3.11.21 Vertical Units ..................................... 52
v
Table of Contents
3.11.22 Layer Peeling (Dynamic
Deconvolution) Traces ...................... 53
3.11.23 Fast Fourier Transform (FFT) Traces ...
.......................................................... 54
3.11.24 Remote Control ................................. 54
3.11.25 Cable Type Library ........................... 54
3.11.26 Other Measurement Settings ............ 55
3.11.27 User Configurations .......................... 56
4 CT Viewer™ ......................................................... 57
4.1 Sending Saved Traces to a Computer ....... 57
4.1.1
Send Saved Traces with a Thumb
Drive.................................................. 57
4.1.2
Send Saved Traces over USB .......... 57
4.1.3
Send Saved Traces and Use Remote
Control with Ethernet ........................ 58
4.1.4
Use Remote Control ......................... 59
4.1.5
Record and Playback Real-Time TDR
Trace Movies .................................... 59
5 TDR Measurement Theory ................................... 61
5.1 Time-Domain Reflectometry (TDR) ............ 61
5.2 Reflection Coefficients ................................ 61
5.3 Common Types of TDR Cable Faults ........ 62
5.4 Velocity of Propagation (VoP, Vp) .............. 64
5.5 Distance-to-Fault (DTF) and Cable Length 65
5.6 Impedance .................................................. 65
5.7 Return Loss ................................................ 65
5.8 VSWR ......................................................... 67
5.9 Rise Time and Spatial Resolution .............. 67
5.10 Timebase / Cursor / Horizontal Resolution.....
.................................................................... 68
5.11 Frequency-Domain Measurements ............ 69
5.11.1 Scattering Parameters ...................... 69
5.11.2 Return Loss (S11) .............................. 70
5.11.3 Insertion Loss (S21) ........................... 70
5.11.4 Cable Loss (S21) ............................... 70
5.12 Smith Charts ............................................... 71
5.13 Normalized TDR Traces ............................. 71
5.14 Layer Peeling / Dynamic Deconvolution..... 72
vi
6 Options and Accessories ..................................... 73
6.1 Options ....................................................... 73
6.2 Accessories ................................................ 73
Appendix A Specifications ..................................... 75
A.1 Electrical Specifications .............................. 75
A.2 Environmental Specifications ..................... 77
A.3 Mechanical Specifications .......................... 77
A.4 Certifications and Compliances .................. 77
Appendix B Operator Performance Checks .......... 79
B.1 General Information .................................... 79
B.2 Required Equipment ................................... 79
B.3 Getting Ready............................................. 79
B.4 Operator Performance Checks................... 80
Appendix C Operator Troubleshooting .................. 85
C.1 General Information .................................... 85
C.2 Power On Test............................................ 85
C.3 Functional Block Diagram and
Troubleshooting Flowcharts ....................... 85
C.4 Parts List..................................................... 96
Appendix D Maintenance and Service Instructions ....
............................................................ 97
D.1 Cleaning and Lubrication ............................ 97
D.2 Cleaning and Lubrication Interval ............... 97
D.3 Battery Removal / Replacement................. 97
D.4 Calibration and Calibration Interval ............ 97
D.5 Install CT100B License .............................. 98
D.6 Clean Storage............................................. 98
Appendix E Vp of Common Cables ....................... 99
E.1 Cable Types ............................................... 99
E.2 Dielectric Material ....................................... 99
E.3 RG Standards ........................................... 100
E.4 MIL-C-17 Standards ................................. 101
E.5 Commercial Designations ........................ 101
E.6 Twisted Pair .............................................. 102
Glossary .................................................................. 104
Index
.................................................................. 111
CT100B TDR Cable Analyzer Operator's Manual
List of Figures
Figure 1: Diagram of the CT100B front panel. ........................................................................................... 11
Figure 2: Diagram of the rear panel of the CT100B / CT100HF. ............................................................... 13
Figure 3: Screenshot showing typical features of the CT100B. ................................................................. 15
Figure 4: Clip lead adapter vs controlled-impedance adapter.................................................................... 27
Figure 5: Screenshot showing AUTOFIT result. ........................................................................................ 28
Figure 6: Use of the HORIZONTAL SCALE knob to improve Vp accuracy................................................ 28
Figure 7: Final Vp of the cable. ................................................................................................................. 29
Figure 8: Smoothed vs. unsmoothed traces at very small vertical scales .................................................. 29
Figure 9: Small fault in a long cable.. ........................................................................................................ 30
Figure 10: AUTOFIT cable ........................................................................................................................ 31
Figure 11: Vertical scale used to emphasize cable fault. ........................................................................... 31
Figure 12: A zoomed-in view of the cable fault .......................................................................................... 32
Figure 13: Relative distance measurement between two SMA connectors. .............................................. 32
Figure 14: Multi-segment cable segment with Vp of 0.400. ....................................................................... 33
Figure 15: Multi-segment cable segment with Vp of 0.850. ....................................................................... 34
Figure 16: Scan of a portion of a cable, zoomed-in vertically .................................................................... 35
Figure 17: Working with traces. ................................................................................................................. 36
Figure 18: Using the on-screen keyboard. ................................................................................................ 37
Figure 19: Loading a trace. ....................................................................................................................... 38
Figure 20: Envelope Plot with Fill Mode .................................................................................................... 40
Figure 21: Envelope Plot with Probability Density display. ........................................................................ 40
Figure 22: Envelope Plot with Fill Mode, showing the range of impedance values at the cursor position .. 41
Figure 23: Difference trace........................................................................................................................ 42
Figure 24: First-derivative trace ................................................................................................................ 42
Figure 25: Resistive cable loss correction, before. Note that the trace slowly rises. .................................. 44
Figure 26: Resistive cable loss correction, after. Note that the trace is nearly horizontal. .......................... 44
Figure 27: S11 return loss plot and TDR trace of a 2.4 GHz WiFi antenna. ................................................ 45
Figure 28: S11 between cursors bracketing an SMA barrel adapter on the TDR trace. .............................. 47
Figure 29: S11 between cursors with tightened connector ......................................................................... 48
Figure 30: S11 between cursors with loosened connector. ......................................................................... 48
Figure 31: Using a phase stable cable to improve S21 insertion loss measurements ................................. 50
Figure 32: Smith chart representation of open fault ................................................................................... 50
Figure 33: Smith chart representation of short fault ................................................................................... 51
Figure 34: Smith chart representation of a 50 ohm resistive load .............................................................. 51
Figure 35: Smith chart of reactive 200 ohm load ....................................................................................... 51
Figure 36: Normalized trace showing short fault in a 50 ohm cable........................................................... 52
Figure 37: TDR trace with impedance vertical units demonstrating vertical scale in ohms ........................ 53
Figure 38: Example Layer Peeling trace ................................................................................................... 54
Figure 39: Connect to CT Viewer menus. ................................................................................................. 58
Figure 40: Connect to CT Viewer window. ................................................................................................ 59
Figure 41: An open cable fault shows an upward step edge at the location of the fault. ............................ 62
Figure 42: A short cable fault shows a downward step edge at the location of the fault. ........................... 62
Figure 43: An open cable fault at 815 ft. ................................................................................................... 63
Figure 44: Normal SMA female barrel interconnect measuring ~0.4 ohms. ............................................... 63
Figure 45: Comparison of typical SMA and BNC coaxial cable interconnects. .......................................... 64
Figure 46: Relationship of impedance (ohms) to reflection coefficient (rho) .............................................. 65
CT100B TDR Cable Analyzer Operator's Manual
vii
List of Figures
Figure 47:
Figure 48:
Figure 49:
Figure 50:
Figure 51:
Figure 52:
viii
Relationship of return loss (dB) to reflection coefficient (rho). .................................................. 66
Relationship of voltage standing wave ratio (VSWR) to reflection coefficient (rho). .................. 67
Simulated comparison of a 90 ps rise time TDR and an 800 ps TDR ....................................... 68
Comparison of S11 return loss of a 2.4 GHz WiFi patch antenna ............................................ 70
Impedance Smith chart relationships. ...................................................................................... 71
Layer peeling scattering diagram ............................................................................................. 72
CT100B TDR Cable Analyzer Operator's Manual
1
1.1
General Information
Product Description
The MOHR CT100B TDR Metallic Cable Analyzer uses a form of closed-circuit radar known as timedomain 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. The resultant TDR trace allows the operator to identify changes in impedance along the length of
the cable indicating the presence of faults such as opens, shorts, kinks, defects in the shield or conductor,
foreign substances such as water, thermal damage, among other. The CT100B provides sophisticated
signal processing software that lets users analyze the frequency-domain characteristics of the TDR trace,
replacing a handheld vector network analyzer (VNA) or frequency domain reflectometer (FDR) for many
applications. With the CT100B TDR Cable Analyzer a user can detect, localize, and characterize almost
any cable fault in both the time and frequency domains.
Please note that with the release of the CT100B, the CT100HF instrument has been updated with the
CT100B hardware, firmware, and software improvements. Any reference to the CT100B in this manual also
applies to the CT100HF unless specifically stated.
1.2
Power Requirements
The CT100B may be operated using either the supplied AC adapter or internal NiMH batteries (for a
minimum 6 hours operating time, typical use). The internal NiMH battery charges under AC during normal
operation.
The external AC power adapter is intended to be used with either a 120 VAC or 240 VAC RMS power
source. Use of a standard 3-prong AC socket with intact ground connection is essential for safe operation
of the CT100B with the included AC power adapter. Review the Safety Summary section before operating
the CT100B.
1.3
Options and Accessories
Options and accessories available for the CT100B are described in section 6 Options and Accessories.
1.4
Unpacking and Initial Inspection
Before opening the shipping package containing the CT100B, first inspect it for signs of damage. If there is
evidence of damage to the shipping package, notify both the shipping carrier and MOHR.
The shipping container should contain the CT100B and standard accessories, including this Operator’s
Manual, front panel cover, external AC adapter and power cord, soft transit case, and calibration fixture(s).
If the shipping container is intact but there are missing items or if the CT100B is damaged, defective, or
does not meet operational requirements, contact a MOHR-authorized sales representative.
CT100B TDR Cable Analyzer Operator's Manual
1
General Information
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, affix a label to the outside of the shipping container indicating the name,
address, phone, and email of the owner, the name of the MOHR service representative who was contacted
regarding the shipment, the serial number of the instrument, and a description of the problem with the
instrument and/or the desired service or maintenance.
Optimally, the original shipping carton and packing material should be used to repack the CT100B for
shipment. Otherwise, the following steps should be taken:
1) Place CT100B in ESD-safe (Electro Static Discharge) Bag.
2) Wrap with 3 in. of anti-static bubble wrap or non-movable foam cushioning. DO NOT USE
packaging peanuts.
3) Place in a sturdy cardboard box and fill any additional void with packaging material. DO NOT USE
packaging peanuts.
4) Include any Purchase Orders, Work Orders, or special instructions with shipment.
5) Write the Return Material Authorization (RMA) number on outside packaging.
2
CT100B TDR Cable Analyzer Operator's Manual
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.
2.1
Terms in the Manual
WARNING: Refers to conditions or practices that could result in personal
injury or loss of life.
CAUTION: Refers to conditions or practices that could result in damage to
this product or other products and in some cases could void the Warranty.
2.2
Terms on the Product
2.2.1
DANGER
Indicates an injury hazard immediately accessible.
2.2.2
WARNING
Indicates an injury hazard not immediately accessible.
2.2.3
CAUTION
Indicates a hazard to property including the product.
2.3
Symbols in the Manual
CT100B TDR Cable Analyzer Operator's Manual
3
Safety Summary
2.4
Symbols on the Product
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.
CT100B instruments supplied with a front panel BNC test port are equipped with a built-in internal selfgrounding connection that briefly shorts the conductors of the DUT to each other, dissipating stored
charge, before completing the connection to the CT100B’s sensitive internal sampling circuitry. For this
reason, the last cable connection should always be made to the CT100B test port. For example, if the DUT
is a cable assembly, all internal connections within the cable assembly should be made before connection
is made to the CT100B BNC test port. This ensures that all stored charge in the DUT is discharged during
the connection to the CT100B BNC test port.
Sometimes it is convenient to insert a patch cable between the CT100B BNC test port and the DUT. In this
case, it is recommended that all cable connections, including the connection of the patch cable to the DUT,
be made before connecting the patch cable to the CT100B BNC test port. Otherwise, the BNC test port
self-grounding safety feature is circumvented.
If for some reason the last connection cannot be made at the CT100B test port, then the conductors of the
DUT should be shorted manually using an industry-standard shorting cap termination or equivalent direct
electrical connection.
Note that CT100B instruments equipped with SMA or other front panel test ports do not have internal selfgrounding protection. Therefore, when using these instruments, the conductors of the cable under test /
DUT should always be shorted to each other or to earth ground prior to connection to the CT100B’s test
port.
CAUTION: Failure to properly ground the cable / device under test prior to
connecting it to the front panel connector, either directly or indirectly, could
result in damage to the sampling electronics and will void the Warranty.
2.6
Fuses
There are no external fuses or breakers accessible to the user. However, there are two internal automatic
thermal breakers that disconnect the power from the charger and battery to the rest of the system. These
thermal breakers make an audible click when they actuate. One of the circuit breakers automatically resets
after time. When this breaker cools, the CT100B can be restarted. There is also an internal breaker on the
4
CT100B TDR Cable Analyzer Operator's Manual
Safety Summary
power board. If tripped, this breaker must be reset manually and the instrument should be serviced by
qualified personnel.
CAUTION: If the thermal breakers trip, the instrument should be evaluated
by qualified service personnel for maintenance.
2.7
AC Power Source
The CT100B is intended to operate only from a 120 VAC or 240 VAC RMS power source using the CEand UL-approved 24 VDC external power supply / adapter provided with the instrument.
WARNING: Only use the power cord supplied with the instrument, and
then only if the cord is in good condition. Refer all maintenance regarding
the power supply or power cord to qualified service personnel.
CAUTION: Use of any power source other than the supplied external
power adapter(s) could damage the instrument and may void the
Warranty. 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.
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.
When disconnected from external power, the CT100B is floating relative to earth ground, unless one of the
USB ports is connected to a grounded device. In this case, the ground of the USB device is common with
the CT100B chassis, screen, and electronic controls. An isolated ground power supply is an optional
accessory available upon request.
At all times, the front panel BNC or SMA connector is floating and is isolated by at least 500 VDC from the
remainder of the CT100B. This eliminates measurement errors caused by common-mode noise and slight
ground-potential differences in the cable / device under test. However, care should be taken with respect to
electrical safety, as the front panel BNC or SMA shield is never safely grounded unless connected to a
safely-grounded cable or device and can be considered a second live conductor if connected to a cable or
CT100B TDR Cable Analyzer Operator's Manual
5
Safety Summary
device carrying a non-zero electrical potential relative to earth ground. This situation carries the risk of
electric shock.
WARNING: The BNC or SMA connector shield represents a floating
ground and is never safely grounded even with the use of a properly
grounded AC adapter. Never use the CT100B to test any cable or device
carrying a non-zero electrical potential relative to earth ground, as this
could render an electric shock.
2.9
Danger Arising From Loss of Ground
When disconnected from the AC power adapter, the CT100B is no longer grounded unless connected to a
grounded USB device at the front panel host USB port. Because the test port connector shield is floating
relative to the remainder of the instrument, the test port connector may be operating at an elevated voltage
even when the AC adapter is connected. Therefore, the test port connector should never be used to test
any cable or device with an electrical potential relative to earth.
WARNING: Upon loss of the protective-ground connection, all accessible
parts, including the screen, knobs, and connectors, can render an electric
shock.
2.10
Explosive Atmospheres
Do not operate the CT100B in an explosive atmosphere unless your unit has been specifically certified for
that condition. Explosive Atmospheres: MIL-STD 810G, Method 511.5, Procedure I (+55°C, sea level to
4600 m).
2.11
Do Not Remove Covers or Panels
To avoid personal injury and risk of electric shock, do not open the CT100B case and do not operate
unless the case is fully intact.
2.12
Connecting Cables to the Test Port
To avoid damage to the CT100B and the very sensitive sampling electronics associated with the front
panel BNC or SMA connector, do not connect it to any cable or device that can be driven by active circuitry
or is subject to transient voltage spikes.
WARNING and CAUTION: The instrument should never be used to test
any cable or device carrying live electrical signals, as this carries a risk of
electric shock. This could also damage the sampling electronics and will
void the Warranty.
6
CT100B TDR Cable Analyzer Operator's Manual
Safety Summary
CAUTION: Always properly ground the conductor(s) of any cable or wiring
to remove any static charge prior to connecting it, either directly or
indirectly through attachment to another cable, to the CT100B's front panel
test port connector. Failure to do so can damage the instrument's sensitive
sampling electronics and will void the Warranty.
2.13
Battery Replacement and Disposal
The CT100B contains an internal battery pack. The internal battery pack is 2700 mAh, NiMH, 12 AA cells,
14.40 volts, 38.88 Wh. There is also a 120 mAh lithium button cell of 2.8 volts and 0.336 Wh. Depending
on the state or local jurisdiction, these batteries may require special disposal and/or recycling. Contact your
local authorities for safe disposal in your area, or you may return them to MOHR for recycling.
CT100B TDR Cable Analyzer Operator's Manual
7
3
3.1
Operating Instructions
Overview
If you are new to TDR cable testing or would like a refresher of TDR measurement theory and applications
before using the CT100B, please read Section 5, TDR Measurement Theory, before continuing on.
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. Care should be taken to protect it from excessive mechanical shock, vibration, static electrical
charges, and water hazards.
The CT100B front panel is protected from impact by a snap-on front cover. The carrying handle rotates 360°
and can be used to support the instrument for bench-top use.
The CT100B is not watertight and must be protected against water spray. If the unit is subjected to water
spray, first turn off the unit with the battery-disconnect power switch on the rear panel and then drain all of
the excess water from the case and allow it to dry completely.
As noted in the Safety Summary and elsewhere, the CT100B is sensitive to damage introduced by
electrostatic discharge. Always properly ground the conductors of a cable to each other or to earth ground
before attaching it, either directly or indirectly, to the front panel BNC, SMA, or other test port. Failure to do
so could damage the sampling electronics and void the Warranty.
The CT100B can be stored in temperatures of between -20°C to +60°C with or without a battery installed
and can be operated from 0°C to +50°C.
3.1.2
Powering the CT100B
The CT100B can be powered through the included 120/240 VAC (RMS) to 24 VDC external power adapter.
This adapter has sufficient capacity to charge the internal battery from a dead battery state while the unit is
under operation. The internal battery will allow the unit to operate using power conservation techniques for
periods of at least 6 hours under typical use. Automatic power-down occurs after a variable amount of time
of inactivity, selectable in software by the user. The screen also can be set to turn off after a set amount of
inactivity. A heavily discharged battery will require 2.5 hours to reach full charge.
Fusing is internal and based on thermal reset switches and a manual-reset breaker. If one of these fuses
trips, it may indicate that a hardware malfunction has occurred and the instrument should be evaluated by
qualified personnel.
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.
CT100B TDR Cable Analyzer Operator's Manual
9
Operating Instructions
The battery should be charged between 0ºC and +45ºC. Battery operation should be limited to between 0ºC
and +50ºC. Batteries should be stored between -20ºC and +60ºC. If the battery pack is older, it may not
show a 100% charge capacity even when the maximum battery charge is obtained.
CAUTION: Do not attempt to charge the battery pack below 0ºC or above
+45ºC. Batteries should not be stored below -20ºC or above +60ºC.
3.1.4
Charging and Power Status
The CT100B operates from a 24 volt power adapter or the internal battery pack.
In the Power menu, a submenu of the Settings menu, the user can set power save and shutdown timers.
Different time-out values can be set for when the CT100B is using the AC/DC converter or batteries. In
power save mode, the screen goes blank and only enough power is used to monitor for user input. When
input is received, the CT100B wakes back up. When the shutdown timer expires, the CT100B will turn off.
A battery indicator can be toggled on or off with the Power Display menu option in the Power menu. The
indicator will show the level of charge in the battery. It will also show if the 24 volt adapter is attached and
providing power.
3.1.5
Batteries and Long-Term Storage
The CT100B has NiMH internal batteries. These batteries will drain if the CT100B is left in storage over long
periods. To preserve battery charge for as long as possible during storage, make sure the power switch on
the back of the CT100B is set to the OFF position. After several months of storage, the internal batteries
may be completely drained. Allow up to 24 hours for the first recharge of the CT100B after coming out of
long-term storage.
3.1.6
Low Battery
When a low battery condition is first encountered, the CT100B alerts the user. Internal Battery Low text
appears onscreen in red when the battery percentage left drops below 20 percent.
3.2
License Codes
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.
Depending on how it was purchased, the instrument may be supplied with either a 30-day demonstration
license or permanent license. Current license information can be found by navigating to Settings  Info 
License  License Info. A dialog showing license date and active features will appear. When the CT100B
has a permanent license installed, appropriate options will be active. When the instrument has a
demonstration license, the dialog will show a future license date and the instrument will provide appropriate
warnings to the user as the expiration date gets closer. If your CT100B has a license with pending
expiration and you are unsure how to upgrade to a permanent license, please contact MOHR.
10
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
3.3
Preparing to Use the CT100B
Before using the CT100B, make sure you have read and understand the Safety Summary section and
power requirements described in the previous sections. If you are new to TDR cable testing or would like a
refresher of TDR measurement theory and applications before using the CT100B to test cables, please read
Section 5, TDR Measurement Theory, before continuing on.
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 1) and described in the text below.
Figure 1: Diagram of the CT100B front panel.
1) POWER (red) button. Pressing this button turns the instrument on when the main power switch on
the rear panel is in the ON position. Pressing the POWER button when the unit is on will turn the unit
off after verification that you really wish to power down. If the POWER button is held in for several
seconds, the unit will turn off regardless.
2) H1 function button. Function depends on menu.
3) H2 function button. Function depends on menu.
4) H3 function button. Function depends on menu.
5) H4 function button. Function depends on menu.
6) MENU (blue) button. Push to display the top-level menu screen. If a menu is already on the screen,
this button will clear the menu. The previous menu will be displayed. This button also activates onscreen help when held down while pressing other buttons.
7) VERTICAL POSITION knob. Controls the vertical position of the currently selected trace. Trace
selection is controlled by the SELECT button (14).
CT100B TDR Cable Analyzer Operator's Manual
11
Operating Instructions
8) VERTICAL SCALE knob. Controls the vertical scale, which is displayed on the bottom of the
screen. This control modifies the appearance of the currently selected trace. The scale is expanded
about the vertical center of the screen.
9) HORIZONTAL POSITION knob. Controls the horizontal position of the active cursor. Displayed
trace positions are moved horizontally if the cursor is moved toward the edge of the screen to keep
the cursor onscreen.
10) HORIZONTAL SCALE knob. Controls the horizontal scale of displayed traces. The scale is
expanded about the active cursor.
11) BNC or SMA test port. This connects to the cable to be tested. Be sure to properly ground the cable
before connecting it to test port in order to prevent electrostatic damage to the CT100B's sensitive
sampling circuitry.
CAUTION: All static charge must be drained from the cable to be tested prior to
connecting to the test port (11). This is done by shorting the cable center
conductor to the cable sheath/ground return. If this procedure is not followed,
the sampling electronics can be damaged and will void the Warranty.
12) Host USB port. This USB (V1.1) connection can be used to interface to a client USB device such as
a barcode reader, keyboard, or flash drive.
13) FILE button. Opens the File menu, which contains a database of user configurations, saved cable
records (scans), and Vp database for known cable types.
14) SELECT button. Used to select between traces on the screen. It has no effect if there are no other
traces.
15) CURSOR button. This button is used to toggle between the two available cursors. Pressing and
holding the cursor button for one second and then releasing the button will bring both cursors onto
the screen.
16) SCAN button. Displays a specialized soft-menu that brings up the Scan menu.
17) AUTOFIT / HELP (orange) button. Opens the onscreen help library with Autofit soft menu options.
18) M-FUNC (multifunction) button. The function of the M-FUNCTION knob (19) is set by this button.
The current operation is displayed on the screen (top-center).
19) M-FUNCTION (multifunction) knob. This knob adopts the function selected through the use of the
M-FUNC button (18).
20) V1 function button. Function depends on menu.
21) V2 function button. Function depends on menu.
22) V3 function button. Function depends on menu.
23) V4 function button. Function depends on menu.
SELECT (14) + M-FUNC (18) buttons. When the SELECT buttons is held down, press the MFUNC button. The CT100B will generate a screenshot that can be saved to a USB drive.
12
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
3.5
Rear Panel Connectors and Switches
The following numbered items describe the connectors and switches identified in the rear panel diagram
(Figure 2) and described in the text below.
Figure 2: Diagram of the rear panel of the CT100B / CT100HF.
24) 24 VDC power adapter plug. The provided 24 VDC AC adapter plugs into this port. Only MOHRapproved 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.
26) RJ-45 Ethernet port. This is a 10/100 Mb Ethernet port that can be used for data transfer and remote
PC control.
27) Power switch. This is a manual ON/OFF power switch that turns the device off and disconnects the
power from the internal electronics so the unit can be stored and/or shipped safely.
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) F1-F4 map to H1-H4.
2) F5-F8 map to V1-V4.
3) F9 maps to the blue MENU button.
4) F10-F12 map to M-FUNC, SCAN, and SELECT.
5) SHIFT F10-F12 map to AUTOFIT / HELP, CURSOR, and FILE.
6) Vertical arrow keys adjust VERTICAL POSITION knob.
7) Horizontal arrow keys adjust the HORIZONTAL POSITION knob.
8) SHIFT vertical arrow keys adjust the VERTICAL SCALE knob.
9) SHIFT horizontal arrow keys adjust the HORIZONTAL SCALE knob.
10) SHIFT F7 rotates the M-FUNCTION knob counter-clockwise.
CT100B TDR Cable Analyzer Operator's Manual
13
Operating Instructions
11) SHIFT F8 rotates the M-FUNCTION knob clockwise.
3.7
Setting up the CT100B
3.7.1
Setting Date and Time
The date, time, and time zone must be accurately set for saved data in the CT100B to be correctly timestamped.
1)
2)
3)
4)
5)
6)
Change the date and time by pressing the MENU button. This calls up the Main menu.
Select the Settings soft menu option and then select the Info menu.
Select the Time menu option. The Time menu appears.
Select the Set Time Zone menu option. A dialog box listing all time zones appears on the screen.
Use the M-FUNCTION knob to scroll through the list of time zones. Highlight the correct time zone.
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. If the option reads Daylight Savings Off, then press the menu button to toggle it. The CT100B
may prompt you to restart. If so, restart the unit and return to the Time menu. The CT100B will
automatically adjust for daylight savings on the correct dates.
8) Select the Time/Date menu option. A dialog box used to set the date and time appears. See the next
section for methods of navigating and entering data into a dialog box.
9) Press the OK menu option when the correct time and date have been entered.
3.7.2
Navigating Dialog Boxes
For an example of a dialog box with multiple entries, press the MENU button, then Settings, then Info, then
Time, and then Time/Date. Scroll through the different entry boxes with the M-FUNCTION knob. With an
entry box selected, press the Keyboard menu option to call up an on-screen keyboard.
With the on-screen keyboard chosen, select the desired characters with the M-FUNCTION knob, pressing
the Select menu option for each one. Get more character options by selecting the Shift menu option. Delete
the character before the cursor with the Back menu option.
With the keyboard open, accept the current entry with the OK menu option or revert to the original entry with
the Cancel menu option.
With the keyboard off the screen, select the OK menu option to accept all changes to the current dialog box
and close the dialog box. Select the Cancel menu option to close the dialog box while canceling all
changes.
With a USB keyboard attached, entries can be changed directly. Use the tab key to scroll down through
entry boxes and hold down shift and press tab to scroll up through entry boxes. Use backspace to delete
the character before the cursor and use the arrow keys to move the cursor left or right. Press Enter for OK
or Escape for Cancel.
3.7.2.1
Scrolling Dialog Boxes
Some dialog boxes present a list of items to be selected. For an example of this type of dialog box, press
the FILE button, and then press Cable Scan Records (see 3.11.8 and Figure 19). Use the M-FUNCTION
14
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
knob to highlight individual items for selection, and then use the Select option to choose the highlighted
item. Where appropriate, multiple items can be marked for selection using the options on the right-side
menu: Toggle Selected, Clear All and Mark All. When an individual item is marked, it will appear in a
different color.
3.8
Display Features
The CT100B screen provides the operator with numerous features that may be useful in different cable
testing situations. Figure 3 shows some of the typical features you will 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: Screenshot showing typical features of the CT100B.
3.9
Menu Selections and Function Buttons
3.9.1
M-FUNC Button
The M-FUNC Button is used to switch between functions Shift (Trace), Smooth, and Change Vp (and
Fine/Coarse Vp) on the M-FUNCTION knob screen function indicator.
CT100B TDR Cable Analyzer Operator's Manual
15
Operating Instructions
3.9.2
SCAN Button and Menu
The SCAN button displays menu selections associated with saving and managing TDR traces and cable
scan records. SCAN button menu selections are shown in Table 1.
Table 1: SCAN Button and Menu.
st
1 Level Menu
Selection
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
Save
Saves selected trace to internal storage. Renames
previously saved traces.
Show Sel. Trace
Only
Turns all traces invisible except the currently selected
trace. Select again to set all traces visible.
Hide All Traces
Hides all traces except the live trace. (If traces were
previously saved, they can be recalled from the FILE
menu, see section 3.9.6)
Hide Selected
Trace
Hides the selected trace. (If trace was previously
saved, it can be recalled from the FILE menu, see
section 3.9.6)
Start Scan
Initiates cable scan.
Cursor / Snapshot
Switches between scan modes:
Cursor: Creates a new scan of the portion of trace
between cursors using the current resolution and
smooth settings.
Snapshot: Saves trace as currently displayed on
screen.
Math
See Table 2: Math Menu.
Table 2: Math Menu.
st
1 Level Menu
Selection
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
FFT Tools
FFT Settings
16
Window
Sets window type (Hann, Hamming, etc.).
size
FFT buffer size.
Frequency Cut-Off
Range
FFT display frequency cut-off.
Hide Selected
Trace
Hides the selected trace.
Apply FFT
Creates FFT trace from selected trace data.
View Live FFT
Creates live FFT trace from live TDR trace.
Apply VSWR
Creates VSWR (Voltage Standing Wave Ratio) trace
from a selected Complex Division or S11 trace.
Set Base
Sets base trace for complex FFT trace division.
Complex Division
Creates complex division FFT: Divides selected FFT
by base FTT. Equivalent to uncalibrated S11 trace
when base FFT is of a Shorted test port.
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
(Table 2 continued)
st
nd
1 Level Menu
Selection
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
Phase
Creates phase angle trace from currently selected
FFT trace.
Smith Chart
Toggle Smith Chart display for selected complex
division FFT or S11 trace.
S11 Calibration
Performs Open-Short-Load S11 calibration and
creates S11 trace.
Normalize Pulse
Rise Time
Set the rise time to apply to the selected normalized
trace.
SParam &
Normalize Tools
S11 Options
Pre-Filter Options
Changes the filter options that smooth the aberrations
of the base traces.
Post-Filter
Options
Changes the filter options that limit the noise of the
base traces.
Other S11 Options
OSL Bases Visible: When enabled, causes the
Open, Short, and Load traces to not appear
onscreen. Helps eliminate excess onscreen clutter.
Align Base Traces: When enable, the Open, Short,
Load, and DUT traces may be aligned to each other
based on the common part of the beginning of the
trace.
Calibration
Standards
Brings up a table of Calibration Standard Kits
Coefficients. There is the option to change and apply
the Standards.
S11 -> USB (.csv)
Creates a CSV (Comma Separated Value) file of the
selected S11 trace and outputs that file to a
connected USB drive.
Phase Corr. Off /
On
Toggles the Phase Correction On/Off.
Phase Corr. Start
Using the active time-domain cursor, sets a new start
point for the Phase Correction.
Between Cursor
Off / On / Hold
Toggle S11 Between Cursors mode:
Off: Between Cursors Off.
On: Between Cursors On – the active section will
adjust with time-domain cursor movement.
Hold: Between Cursors Hold – the active section will
remain regardless of cursor movement.
Hide Selected
Trace
Hides the selected trace.
Reapply S11
Adjusts the time-domain settings to match those used
for the selected Live S11 trace.
(Table 2 continued)
CT100B TDR Cable Analyzer Operator's Manual
17
Operating Instructions
st
1 Level Menu
Selection
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
Apply
Normalization
Create normalized TDR trace based on the selected
S11 trace.
Cable Loss
Changes selected S11 trace to Cable Loss (S21 /
insertion loss) trace. Terminate cable with precision
short adapter for meaningful results.
Smith Chart
Toggle Smith Chart display for selected complex
division FFT or S11 trace.
Layer Peeling
Create layer peeling trace from selected trace.
Assumes active cursor (layer peel start) is set at
50 ohms.
Hide Selected
Trace
Hides the selected trace.
Set Base
Sets selected trace as the base (denominator) trace
for math operations.
Difference
Creates subtraction trace from selected trace and
base trace (Difference = Selected – Base).
st
1 Derivative
Creates first derivative trace from selected trace.
Der. Smooth Off /
On
Toggles first derivative trace smoothing.
3.9.3
SELECT Button
The SELECT button switches which trace on-screen is the active trace. See Section 3.11.6 for more
information on selected traces.
3.9.4
AUTOFIT / HELP Button
The AUTOFIT/HELP button calls up the online help library and Autofit soft menu options. Use the MFUNCTION knob and Select menu option to scroll through and select the help library content. When you
select the Autofit menu option, the CT100B looks for the TDR signature of an open or short-terminated
cable and selects appropriate horizontal and vertical scale values to display the entire cable on the screen.
By default the cursors are positioned approximately to the beginning and end of the cable, or you can
choose to leave the cursors where they are currently positioned.
If Autofit Vert Only is selected then only vertical scale and position are affected.
Selecting the Reset Off-Screen Cursors menu option brings any off-screen cursors back onto the display.
3.9.5
CURSOR Button
Toggles between cursors, making the active cursor inactive and the inactive cursor active. Pressing and
holding the CURSOR button for one second then releasing will move any cursors not on the screen to the
screen. (This is the same behavior as the Reset Cursors in the Autofit menu.)
18
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
3.9.6
FILE Button and Menu
Use this menu to access the user library of configurations, cable types, and cable records. FILE button
menu selections are shown in Table 3.
Table 3: FILE Button and Menu.
st
1 Level Menu
Selection
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
Custom Cable
Types
Use to add, select, or delete an entry from the custom
cable type library:
Add New: Enter in new cable type information.
Delete: Delete selected cable type from the library.
Select: Select the highlighted custom cable type.
Instrument settings change to reflect the cable Vp
setting.
Reference Cable
Types
Use to select a built-in cable type from the standard
cable type library. Instrument settings change to
reflect the cable Vp setting.
Cable Scan
Records
Use to select, delete, or USB save a previously saved
TDR trace. (See section 3.11.8 for more.)
Config Entries
Use to add, select, or delete an entry from the user
configuration library.
Export  USB
Export selected TDR trace to USB drive.
Save Scan
Saves selected trace to internal storage.
Print Screen
Prints directly to a PCL3 compatible printer via USB.
3.9.7
“Blue” MENU Button and Top-Level Menu
If no menu is displayed, MENU loads the main top-level menu. If the top-level menu is displayed, it closes
the menu. If a submenu is displayed, it displays the parent menu. Top-level menu selections are listed
below in Table 4. Holding down the MENU button while pressing any button (or the M-FUNCTION knob) will
display a help dialog for that button's current menu selection.
Table 4: MENU Button and Menus
st
1 Level Menu
Selection
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Cable Len
Purpose / Action
Adjust the pulse timing for different length cables:
Short: For cables of up to approximately* 300 ft. (90
m) long.
Medium: For cables up to 1500 ft. (450 m) long.
Long: For cables up to 6,000 ft. (1,800 m) long.
[Note: Access Extra Long mode in the Measurement
submenu. Use Extra Long mode for cables over a mile
(2 km) in length.]
*The exact length will depend on the Vp setting.
CT100B TDR Cable Analyzer Operator's Manual
19
Operating Instructions
(Table 4 continued)
st
1 Level Menu
Selection
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
Resolution
Sets TDR trace horizontal sampling resolution:
Normal: A fixed setting suitable for connector level
detail for each of the cable length modes. Short is 5.34
ps (less than 1 mm), medium is 17.5 ps (~2 mm), long
is 99.2 ps (about ½ inch), and extra long is 381 ps
(about 2 inches). Stays fixed regardless of screen
horizontal scale.
Screen: Screen resolution (1 sample/pixel) varies
dynamically with the current horizontal scale.
Fixed: allows user to set a specific value no matter
the cable length setting.
File (Load/Save)
Calls up the FILE button menu. Use to add, select, or
delete an entry from the cable type, user configuration,
and/or cable record libraries:
Connect to CT
Viewer
Find CT Viewer
Search the local area network looking for running CT
Viewer 2 programs. If successful, it establishes a
connection.
Manual Connect
A dialog with a list of PCs that have previously been
added is displayed. The following options will appear.
Add PC: Enter in new server IP information.
Delete: Delete selected server from the library.
Select: Connect to the highlighted server.
Cancel: Cancel out of the connection menu.
See Section 4: CT Viewer™ for instructions on
connecting to the CT100B to CT Viewer.
Use USB
Closes this menu. Go to the PC you are running CT
Viewer 2 and use that program to connect to the
CT100B.
SParam Tools
Tools for creating S-parameter traces and normalized
traces. See SParam & Normalize Tools in Table 2:
Math Menu.
Measurement
Vert. Ref.
20
Vert. Ref Off / On
Toggles VR (Vertical Reference) mode on/off.
Set Vert. Ref.
Performs VR calibration using short/open terminators.
When setup is complete, a green vertical line indicates
start of VR measurements.
Vert. Ref. Center
Imp.
Adjusts VR calibration to use impedance matching
adapters and baluns.
Vert. Ref. Start
Sets start of VR at the position of the active cursor.
Vert. Ref. End
Sets end of VR at the position of the active cursor.
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
CT100B
(Table 4 continued)
st
1 Level Menu
Selection
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
Cable Segments
Add New
Segment
Create a new segment boundary at the active cursor.
The selected segment will be split in two, each with the
same initial Vp.
Delete Segment
Delete the currently selected segment. The segment
will be merged with the segment to the left.
Delete All
Segments
Delete all segments. The CT100B will return to normal
operation. A single Vp now applies to the entire trace.
Select Prev
Segment
Select the segment to the left of the currently selected
segment.
Select Next
Segment
Select the segment to the right of the currently selected
segment.
Reset All Vp
Reset the Vp of all segments to 1.000.
Restore All Vp
Restore Vp of all segments to the previous values.
Extra Long Mode
Extra Long Mode allows the CT100B to obtain traces
out to 40,000 ft. (12,000 m) (assumes Vp=0.66). Extra
Long Mode is slower than other cable lengths and
some instrument features are not available. When in
Extra Long Mode, the Cable Length menu option will
indicate Extra Long Mode On. Selecting the cable
length menu item will switch off Extra Long Mode.
Vert. Units
Select vertical units for a time-domain trace from
reflection coefficient (), impedance (Ω) or Voltage
Standing Wave Ratio (VSWR). A few features of the
CT100B only work with the reflection coefficient
setting.
Envelope Plot
Captures transient cable and connector faults.
Envelope Plot Off
/ On
Enable/disable envelope plot mode. When turned on
the CT100B begins capturing trace data and displaying
envelope plot information.
Reset
Deletes/restarts captured TDR trace envelope data.
Fill Mode Off / On
Toggles between fill and probability density plot mode.
Use fill mode to find magnitude of impedance change
and highlighting fault location. Use probability density
plot mode to find infrequent transient faults.
Hold Off / On
When Hold is on, trace controls are locked for an
CT100B TDR Cable Analyzer Operator's Manual
21
Operating Instructions
envelope plot. When Hold is off, trace controls work
normally.
Clear Historic
As trace controls are used to change an envelope plot,
the envelope plot preserves a record of the trace from
previous positions. Clear Historic erases this history,
leaving only the plot from the current position.
(Table 4 continued)
st
1 Level Menu
Selection
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
Vertical Correction
Adjust mρ Offset
Allows manual vertical measurement offset
adjustments. This allows advanced users to manually
calibrate impedance measurements at a particular
location to a known value.
When activated the M-FUNCTION knob adjusts the
vertical offset. The blue M-FUNC indicator shows the
offset in mρ (millirho).
Cancel mρ Offset
Use this option to cancel a manual mρ (millirho)
correction. Automatic temperature adjustment will
resume auto-correction of the vertical measurements
Adjust Ω/(unit)
Use the M-FUNCTION knob to change the ohms per
unit distance resistive loss setting until the cable
shows no upward or downward trend across its length.
Ω/(unit) Correct.
On / Off
Toggle resistive cable loss correction on/off, as
described above. If the end point of the correction has
not been set, then it will be set to the position of the
active cursor.
Set Ω/(unit) Pos.
Set the position of the ohms/(unit distance) position to
that of the active cursor.
Clear
Reset all Ω/(unit) settings.
Horiz. Units
Toggles through horizontal units (meters, feet,
centimeters, inches, yards)
RRC Classic /
1502C Mode
Classic: Referenced to amplitude at inactive cursor.
1502C: Referenced to amplitude at test port.
Vp 3 / 6 Sig Figs
Toggle Vp significant digits from 3 to 6 digits.
Meas. Settings
Math
See Table 2: Math Menu.
Settings
See Meas. Settings under Measurement menu above.
Meas. Settings
Network Settings
Static Network
Settings
22
Modify static network settings (if DHCP inactive):
IP Address: IP address (xxx.xxx.xxx.xxx)
Netmask: Subnet for CT100B
Gateway(optional): Gateway server setting
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
Nameserver 1&2(optional): Nameserver settings
DHCP on / off
Toggles DHCP On/Off.
Show IP Config.
Displays current Ethernet configuration.
CT100B TDR Cable Analyzer Operator's Manual
23
Operating Instructions
(Table 4 continued)
st
1 Level Menu
Selection
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
Web Export On /
Fast / Off
Activates and toggles function of web server:
Live trace data:
http://<<IP_addr>>/www/trace.csv -- live TDR trace as
comma-separated values (CSV).
Selected trace data:
http://<<IP_addr>>/www/selected.csv -- selected TDR
trace in CSV format.
Screenshot:
http://<IP_addr>/www/screenshot.bmp – bitmap image
of the current TDR screen.
The button toggles Web Export into three states:
On: Normal operation (~2 frames/sec).
Fast Mode: Fast refresh (~7 frames/sec).
Off. Web server not active.
[Note: See Section 4 for more information on using CT
Viewer to acquire TDR traces. See www.mohrtm.com
for information on the CT100B Python programming
library and binary programming protocol for Ethernet
CT100B interface.]
Set Listen Ports
This dialog box allows you to define a different RPC
port # and a different Remote Control Port # for use
with the CT Viewer application (default 12347)
SP232 Protocol
On / Off
Toggles SP232 emulation on / off. A USB to serial
adapter is required for SP232 emulation. Press this
button while emulation is on to switch the baud rate.
DC Power Save
Sets the inactivity timeout for power save mode while
the device is running on external DC supply.
DC Shutdown
Sets the inactivity timeout for shutdown while the
device is running on external DC supply.
Battery Power
Save
Sets the inactivity timeout for power save mode while
the device is running on batteries.
Battery Shutdown
Sets the inactivity timeout for shutdown while the
device is running on battery.
Power Display
Toggles on the on-screen power status display.
Battery Icon/
Power Units
Toggles between voltage or battery icon display.
Analog
Run automated diagnostics on the analog trace
acquisition circuit board. Results are displayed onscreen in a message box.
Database
Clean Database: CAUTION! Not for routine use. This
option defragments the database, freeing up unused
space, then turns off the CT100B. Use this option only
when the CT100B is plugged into an external power
supply. Do not shutdown the CT100B while the Clean
Database command is in progress.
Power
Diagnostics
24
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
(Table 4 continued)
st
1 Level Menu
Selection
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
Front Panel Check
This item opens the front panel button and knob check
screen. Hit each button once and turn every knob in
each direction. Press the red power button to exit
when finished.
Jitter
Jitter measures signal noise, jitter, rise time, and
sampling efficiency of the trace. These values are
used as part of the calibration checkout for the
CT100B, and results of interest are explained in
Appendix B: Operator Performance Checks.
Calibration
Performs Vertical and Horizontal Calibration.
License
License Info: This option gives information about the
license installed on the CT100B.
License from USB: Use this option to load a license
code from a USB flash drive.
Enter License: Manually load a license code. This is
useful for operators who are unable to connect to CT
Viewer or use a flash drive.
Web Update
When a CT100B is connected to the Internet, this item
will automatically update the CT100B if newer
software is available.
Update From USB
Drive
Will run an update from the connected USB drive.
Web Update
Address
View/set the web address to query for updated
software. Normally this setting should not be changed.
Processor
Displays CPU information.
Contact
Contact Information for MOHR.
Software Version
Display software and firmware version information.
This also serves to verify the communications links
between the micro-controllers.
Hardware Info
Display hardware information.
Usage
Display instrument usage in hours.
Time
Time and date settings:
Time/Date: Set the current date and time.
Set Time Zone: Change the time zone.
Daylight Savings On/Off: Sets adjustment for
daylight savings time on/off.
Change Screen
Profile
Toggles screen background (black, gray, white).
Ohms/Rho
Toggles display of impedance (ohms) and reflection
coefficient (millirho) at cursor and between cursors.
Time/Date
Toggles time/date display.
Info
Display
CT100B TDR Cable Analyzer Operator's Manual
25
Operating Instructions
(Table 4 continued)
st
1 Level Menu
Selection
3.10
nd
2
Level Menu
Selection
rd
3 Level Menu
Selection
Purpose / Action
Distance/ns
Toggles display of distance and time (ns) at cursor.
VSWR
Toggles display of VSWR (voltage standing wave
ratio) at cursor.
Temp Comp
Toggles display of Temp Comp autocalibration status.
Min/Max Display
Toggles display of min/max values for high resolution
sampling.
Horiz. Vert. Ruler
Toggles display of horizontal and vertical rulers.
Noise Value
Toggles display of noise value at cursor for diagnostic
purposes.
Vert. Shift
Correction
Toggles the Vertical Shift Correction option. When on,
corrects the vertical shift that can happen when
changing the DUT.
Scale
Toggles display of horizontal, vertical scales and Vp.
Time of Flight
Show Time of Flight time measurements. The
standard nanoseconds display shows electrical time
for a pulse to reach a point and then return to the
CT100.
Time of Flight is exactly half that value. It is the oneway transmission time.
Vert Centering
On/Off
When on, changes to vertical scale will center on the
point where the cursor intersects the selected trace.
When off, changes to vertical scale will center on the
center of the screen.
Intersection
Toggles display of cursor-trace intersection.
Decibels
Toggles display of decibel (dB) values at cursor.
Temperature
Toggles display of instrument internal temperatures.
Test Preparations
If you are new to TDR cable testing or would like a refresher of TDR measurement theory and applications
before using the CT100B to test cables, please read Section 5, TDR Measurement Theory, or go to
www.mohrtm.com before continuing on.
3.10.1
Connecting to the Cable or Device-Under-Test (DUT)
The first and most important decision to make when testing a cable or device-under-test (DUT) is how to
connect to the DUT. Because the connection to the DUT acts as a filter for the test signal into and out of the
DUT, it is very important that the connection have the highest bandwidth and least aberration possible.
Controlled impedance connections are recommended whenever possible. Controlled impedance
connections have conductors with uniform geometry and dielectric properties that do not change
significantly during a test session or between test sessions. Examples of controlled impedance connections
include coaxial-coaxial adapters, coaxial-twisted pair adapters, and fixed-pitch TDR probes.
26
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
Alligator clip and clip lead adapters with flexible wire test leads should be used only as a last resort.
Alligator clip and clip lead adapters are not made for high frequency operation, are severely bandwidth
limiting, and introduce severe aberration and measurement uncertainty into the TDR trace. Figure 4 shows
a comparison test of a coaxial cable using clip lead adapters (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 4: Clip lead adapter (red, top) and controlled-impedance adapter (black,
bottom) testing of 3 ft. coaxial cable with short termination. Active cursor is at the test
port. Clip lead adapters introduce severe TDR trace distortion.
3.10.2
Change Velocity of Propagation (Vp)
Vp is expressed as a fraction of the speed of light. The current setting for Vp appears on the lower center of
the screen. Press the M-FUNC button until the top-center information indicator reads “Vp”. If Vp 6 Sig. Figs
is enabled from the Settings  Meas. Settings menu, two “Vp” indicators will be separately available.
Coarse Adj. Vp allows for the modification of the first 3 significant digits and Fine Adj. Vp allows for the
modification of the last 3 significant digits. See section 5.4 Velocity of Propagation (VoP, Vp) for a detailed
description of Vp.
Turn the M-FUNCTION knob and the Vp value will change accordingly. Measurements and traces are
automatically updated on the display to reflect the new Vp.
All measurements done by the CT100B are based on time, and then converted to distance for display. An
accurate Vp is necessary for accurate cable length and Distance-to-Fault calculations. For cables of a
known type, the Vp can be approximated by using the nominal Vp for that cable type. The CT100B has a
built-in library of cable types and their Vp values (see section 3.11.25). You can also measure the Vp by
testing a known length of cable that is of the same type as the one you want to test. The method is
described in the following section.
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) Measure the physical length of the test cable. Make sure the test cable is of the same type for which
you need to find Vp. If there are any adapters used while connecting the cable, include their length
in the measurement, or set one of the cursors at the end of the adapter before attaching the cable.
CT100B TDR Cable Analyzer Operator's Manual
27
Operating Instructions
2) Attach the test cable to the CT100B. In this example, the test cable is three feet long.
3) Press the AUTOFIT / HELP button, then press the AUTOFIT menu item. The CT100B will now show
the beginning and the end of the test cable (Figure 5). The cable end, in this case an open
termination, has been found at 2.815 feet and the whole cable trace is displayed on the screen.
Figure 5: Screenshot showing AUTOFIT result.
4) Use the HORIZONTAL SCALE knob to zoom in on the end of the cable and get a more accurate
placement (Figure 6) of the active cursor at the beginning or “toe” of the open fault at the end of the
cable.
Figure 6: Use of the HORIZONTAL SCALE knob to improve
Vp accuracy.
5) Press the M-FUNC button to set the M-FUNCTION to Vp, and Adjust Vp using the M-FUNCTION
knob until the CT100B distance measurement to the active cursor equals the physical measurement.
The final Vp value is the true Vp value of the cable (Figure 7). Note that in the Measurement ->
Meas. Settings menu there is an option to set Vp to six significant digits.
28
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
Figure 7: Final Vp of the cable.
3.10.4
Smooth Settings
The CT100B smoothing feature performs temporal averaging to decrease visible noise on the live TDR
trace and improve signal-to-noise ratio (SNR) for first derivative, S11 return loss, and other mathematical
operations. When you acquire baseline TDR scans of cable assemblies meant for archiving and future
comparison use, it is recommended that at least a moderate level of smoothing be used so that the vertical
resolution of the instrument be used to the fullest extent possible. The effect of smoothing is most apparent
at very small vertical scale settings (that is, when the trace is zoomed-in vertically). To change TDR trace
smoothing:
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 0.7 millirho
per vertical division (~70 milliohms/div) is shown in Figure 8.
Figure 8: Smoothed vs. unsmoothed traces at very small vertical scales
(~70 milliohms per vertical division).
CT100B TDR Cable Analyzer Operator's Manual
29
Operating Instructions
3.10.5
Sample Resolution
The sample resolution setting establishes the number of sample points per unit time or distance in the live
TDR trace. In general, higher sample resolution sharpens traces at larger horizontal scales by increasing
the apparent sampling efficiency of the TDR trace (the ratio of sampled vs actual change in voltage from
sample to sample). For larger horizontal scales it also helps ensure that all cable faults are sampled
adequately enough to be detected and displayed on the instrument screen. Note that the sample resolution
of cable scans can be set separately (see 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. At large horizontal scales, the resolution is low and small faults may be undetectable, or at
least underestimated. This is because there may be too few samples in the region of the fault for the
fault to be reliably identified on the trace. For example, if a thousand foot cable is displayed on the
screen, there is only one measurement about every two feet.
2) Normal: Sample resolution setting is chosen to match the cable length setting for good compromise
of detail and speed. For SHORT length cable settings, the resolution is 5.32 ps (less than a
millimeter). For NORMAL length, the resolution is 17.5 ps (about 2 mm). For LONG length, the
resolution is about 100 ps (about 12 mm). The resolution stays fixed regardless of screen horizontal
scale, ensuring that detectable cable and connector faults are displayed at any horizontal scale.
3) Fixed (available under the Measurement->Meas. Settings menu): Set a sample resolution
manually using M-FUNCTION knob; it stays fixed regardless of screen horizontal scale. Useful for
enhancing frequency resolution of S11 return loss and cable loss traces which may require sampling
at resolutions higher than Normal mode.
For larger horizontal scales, the Normal or Fixed sample resolutions provide high resolution sampling. The
trace display at each pixel is a vertical bar that shows the maximum and minimum values sampled within
the pixel. This feature ensures that any detectable TDR cable fault is displayed at least 1 pixel wide
regardless of horizontal scale.
A Normal sample resolution trace of an 800 ft. (250 m) cable is shown in Figure 9. In this case the high
resolution sampling of the Normal setting ensures that the small fault from a 50 ohm BNC barrel connector
is displayed despite the large horizontal scale. The Screen sample resolution mode did not reliably show
this fault at this horizontal scale, but did depict the fault when zoomed in to a smaller section of cable that
displayed at a smaller horizontal scale.
Figure 9: A small fault (red circle) in an approximately 800 ft. (250 m) cable. This
8 ohm fault 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).
30
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
3.10.6
Temperature Correction
The CT100B automatically adjusts for changes in ambient temperature. When temperature is displayed on
the screen, a message is also shown giving the status of temperature correction. When the CT100B is fully
adjusted, the message reads “TC: OK” in green text.
3.11
Test Procedures
3.11.1
Measure Distance-to-Fault (DTF)
1) Attach the cable to the test port.
2) Set Vp to match the Vp of the attached cable or select an appropriate cable from the cable type
library. See section 3.11.25 Cable Type Library for instructions on using the cable type library.
3) Press the AUTOFIT / HELP  AUTOFIT menu option. The CT100B trace is now scaled to show the
entire cable from beginning to end. See Figure 10.
Figure 10: AUTOFIT cable. The cable termination is a short.
4) Note the “bump” in the middle of the cable. This is where two short test cables are connected with a
BNC barrel connector. Position the active cursor on the reflection caused by this cable fault.
Adjusting the vertical scale helps make cable faults more obvious, as in Figure 11 which is at the
same horizontal scale as Figure 10 but zoomed-in vertically. By positioning the inactive cursor just
before the connector, we can see the delta value of ~4 ohm impedance change in the connector vs.
the impedance of the cable.
Figure 11: Vertical scale used to emphasize cable fault.
CT100B TDR Cable Analyzer Operator's Manual
31
Operating Instructions
5) Use the HORIZONTAL SCALE and VERTICAL SCALE knobs to further zoom in on the fault to get a
more accurate measurement of Distance-to-Fault (DTF), typically measured from the “toe” or early
rising edge of the fault. The distance measurement to the active cursor is the Distance-to-Fault. See
Figure 12.
Figure 12: A 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).
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. Note that Vp must be set accurately for the section of cable between the cursors
for the CT100B to measure relative Distance-to-Fault accurately. The pulse velocity of any part of the cable
that is not between the cursors will not affect the relative distance measurement. To measure the relative
distance between two points in a cable, do the following:
1)
2)
3)
4)
Move the active cursor to the beginning of the section to be measured.
Press the CURSOR button to switch cursors.
Move the newly active cursor to the end of the section to be measured.
The CT100B displays the distance measured between the two cursors as a “Δ” value below the
absolute distance measurement. Figure 13 is a 3 ft. segment of 50 ohm cable marked by small
impedance “faults” caused by SMA connectors on both ends.
5)
Figure 13: Relative distance measurement between two soft
cable “faults” caused by SMA connectors.
32
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
In general for the most accurate relative distance or time measurements between two faults, place the
cursors on the “toe” region of the faults where the TDR trace is just beginning to rise above or fall below the
cable characteristic impedance.
3.11.3
Multi-Segment Cable DTF Measurements
Cable assemblies are sometimes made up from different types of cables in series, each of which may be
chosen for unique characteristics such as high-temperature operation or radiation resistance. Such cables
frequently have different velocities of propagation (Vp), making Distance-to-Fault (DTF) measurements
difficult. If the average Vp of the assembly or the Vp of any one cable assembly is used, it will result in
inaccurate distance measurements along the length of the compound cable.
The CT100B includes multi-segment cable measurement capability designed to improved 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.
The distance-to-fault calculated from the compound trace shows improved accuracy. The following
procedure can be used to perform multi-segment cable measurements:
1) Select MENU  Measurement menu.
2) Select Cable Segments submenu.
3) Place the cursor at the position of the cable segment, marked by a connector impedance signature
or other demarcation, such as physical distance as calculated using known Vp for a given cable
segment.
4) Select Add New Segment.
5) Repeat steps 3 and 4 for each cable segment.
6) Use the Prev Segment and Next Segment selections to select each cable segment and use the MFUNC Vp option to set the given segment’s velocity of propagation.
7) The Distance-to-Fault measured by the cursor reflects multi-segment Vp as shown in Figure 14 and
Figure 15.
Figure 14: Multi-segment cable segment with Vp of 0.400 (red circle).
CT100B TDR Cable Analyzer Operator's Manual
33
Operating Instructions
Figure 15: Multi-segment cable segment with Vp of 0.850 (red circle).
3.11.4
Ohms-at-Cursor Measurements
The CT100B also displays the impedance in ohms (Ω) at the cursor position. A reading before and after a
reflection from a fault shows the impedance mismatch that could cause such a reflection. Impedance
measurements at the first fault in a cable are more accurate than impedance measurements at more distant
faults.
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. Cable
scans can subsequently be reviewed at different levels of detail and compared to prior scans to identify
subtle changes in cable or connector performance. See Figure 16. Scans may also be referred to as traces
in this manual.
Saved scans can appear on the screen in addition to the live trace. Pressing the SELECT button switches
between traces. Vertical position and scale are adjusted for individual traces. Changing these values for one
trace won’t affect other traces.
To scan a cable or cable segment:
1) Press the SCAN button to bring up the Scan menu.
2) Choose the Start Scan option from the menu to begin a cable scan.
3) Select the cable scan (see section 3.11.6 below) and manipulate as needed.
There are two types of scans:
1) Screen scans - Capture the live trace as it appears on the screen. This can work well if using Normal
or Fixed resolution mode. If using Screen resolution, the result will be good only with a very short
cable.
2) Cursor scans - Captures the entire trace between the two cursors at the current sample resolution
(see Section 3.10.5). This works even if one or both cursors are off-screen while you are zoomed in
looking at a smaller section.
34
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
A scanned trace is created with the smoothing factor as set at the time of the scan. Cursor or Custom scans
that cover a long distance at a high resolution may take a long time. During a scan, a menu will appear with
a Cancel option. Select Cancel to abort the scan.
Figure 16: Scan of a portion of a cable (red), zoomed-in vertically to show
additional detail relative to the live trace (black).
3.11.6
Select a Trace
The CT100B always shows one trace on the screen in bold. This is the selected trace. VERTICAL
POSITION and VERTICAL SCALE knobs as well as the Save, Rename, and Hide Selected Trace options
on the Scan menu are all actions that operate on the selected trace, leaving other traces on the screen
unchanged. Vertical measurements such as reflection coefficient, return loss, and impedance are always
based off of the selected trace and may disappear if the cursor scrolls beyond a scanned boundary or is off
screen.
Press the SELECT button to change which trace is active. Figure 17 demonstrates this principle with three
different traces. Screenshots show selection of (A) a live trace (top), (B) a scanned trace that has been
translated vertically using the VERTICAL POSITION knob (middle), and (C) a trace representing the
difference between the two (bottom).
CT100B TDR Cable Analyzer Operator's Manual
35
Operating Instructions
Figure 17: Working with traces.
3.11.7
Store a Trace
A scanned trace can be stored for later recall:
1)
2)
3)
4)
5)
Press the SCAN button. The Scan menu appears.
Press the SELECT button until the scanned trace to be stored is selected.
Select the Save option from the menu.
The CT100B requires a name for storage and will prompt for one with a dialog box.
A dialog menu appears. Press the keyboard menu option to display the on-onscreen keyboard or
use a USB keyboard.
6) Use the M-FUNCTION knob and the Keyboard menu to select letters and numbers. See Figure 18.
Also see Navigating dialog boxes on page 14 for more information on using the Keyboard menu.
Press the Select option to enter the highlighted letter into the name.
36
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
Figure 18: Using the on-screen keyboard. Choose Hide Keyboard when finished.
Then choose OK to save the trace with the name you entered.
7) Press the OK option from the menu when finished.
The trace is now stored, and can be recalled later by name under FILE  Cable Scan Records.
Other trace types, such as Difference traces, Derivative traces, and frequency domain traces (such 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) Select the Cable Scan Records option. A Scrolling Dialog Box (see 3.7.2.1) appears for the selection
of a stored trace.
3) Use the M-FUNCTION knob to highlight the trace you wish to load.
4) Press the Select menu option to load the trace.
The stored trace now appears on the screen. It can be selected and manipulated the same as any
scanned trace. See Figure 19 in which the loaded trace (red, top) has been translated slightly upward
using the VERTICAL POSITION knob in order to improve visualization.
CT100B TDR Cable Analyzer Operator's Manual
37
Operating Instructions
Figure 19: Loading a trace.
Some stored traces, such as FFT traces, require some re-calculation to fully load. This calculation is done
automatically, but it may take several seconds.
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
Transferring Traces
The CT100B ships with an installation DVD for the CT Viewer™ (Version 2) software for Windows. Using
either a USB or an Ethernet connection, the CT100B can transfer stored scans to CT Viewer. These scans
are then stored in the Windows computer for later retrieval, review, e-mail, and analysis. See Section 4: CT
Viewer™ and/or the CT Viewer™ 2 Quick User Guide for details on transferring traces to a computer using
CT Viewer.
3.11.9.1.1 Export Trace to File
Traces can also be exported to a USB drive for storage, or to transfer to CT Viewer or to another CT100B.
To export one or more traces to USB:
1) Insert a USB drive into the front panel of the CT100B.
2) Press the FILE button, and then press the Cable Scan Records menu option.
38
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
3) Mark specific traces for transfer using the Toggle Selected option or select them all with the Mark
All option.
4) Press the Export  USB menu option. A message should appear after a short time confirming
that the traces were transferred.
3.11.9.1.2 Export Trace to CSV
The active trace can be exported to a .csv file on an attached thumb drive. To do this:
1) Select the desired trace to export using the SELECT button.
2) Press the FILE button to open the file menu.
3) Press the Export  CSV menu option. A dialog box will appear displaying the name of the file to
be used.
4) Change the file name to the desired name using a USB Keyboard or the on-screen keyboard by
pressing the Keyboard menu option.
5) Press the OK menu option. A message should appear after a short time that confirms the trace
was exported.
3.11.9.2
Deleting Traces
Once scans are backed up to a computer, they can be deleted from the CT100B either through the CT
Viewer software or directly as follows:
1) Press the FILE button to open the File menu.
2) Select Cable Scan Records. A scroll dialog appears, showing all saved trace scans.
3) Mark specific traces for deletion using the Toggle Selected option or select them all with the Mark All
option.
4) Select the Delete option. You will have to confirm the deletion.
3.11.10 Transient / Intermittent Fault Detection
Cable system troubleshooting frequently involves detecting and localizing transient or intermittent faults,
such as a twisted pair cable with frayed insulation that briefly shorts its conductors when mechanically
disturbed, or a coaxial connector that reflects an open when shaken. The CT100B’s Envelope Plot mode
simplifies characterization of these types of intermittent faults. To create an Envelope Plot, use the following
procedure:
1) Position the TDR trace such that the area of interest is located on the screen at a satisfactory
horizontal and vertical scale. Horizontal and vertical scale cannot be changed once in Envelope Plot
mode.
2) Select MENU  Measurement menu.
3) Select Envelope Plot submenu.
4) Select Envelope Plot Off to turn Envelope Plot mode on.
5) Toggle between Fill Mode and Probability Density display mode with the Fill Mode On / Off option.
6) The CT100B can monitor a trace for extended periods of time with appropriate power management
settings are enabled.
CT100B TDR Cable Analyzer Operator's Manual
39
Operating Instructions
7) Sometimes manipulation of the cable and/or connectors of interest during Envelope Plot monitoring
will provoke an intermittent TDR fault.
Fill Mode fills in an area plot between the maximum and minimum impedance values. This is useful to
highlight the location of the fault because the fault typically creates an “arrow” that points to the location of
the fault as shown in Figure 20. Probability Density mode shows the underlying TDR traces which can be
useful to determine the fault mechanism and likelihood of occurrence as shown in Figure 21. Both modes
provide the range of impedance values at cursor, as shown in Figure 22.
Figure 20: Envelope Plot with Fill Mode, active cursor at fault location. Note fault
forms an “arrow” (emphasized by the black lines) pointing to the location of a
loose connector with the impedance variation caused by mechanical bending.
Move the cursor to that location and read the position on the screen (red circle).
Figure 21: Envelope Plot with Probability Density display.
40
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
Figure 22: Envelope Plot with Fill Mode, showing the range of impedance values
at the cursor position (51.5–185.4 ohms, red circle).
Note that transient and intermittent faults can also be recorded using the CT Viewer Remote Control feature
as described in Section 4.1.4.
3.11.11 Difference (Subtraction) Traces
Difference traces are traces calculated from the subtraction of one trace from another trace. A difference
trace can allow the operator to identify subtle changes in cable or connector performance. It is
recommended that for any important cable and connector assembly, the as-manufactured or known-good
configuration of the assembly be scanned and archived on the CT100B and/or a host PC running CT
Viewer. Later, these archived traces can be used to create difference traces from current data to highlight
changes in cable assembly impedance. To create a difference trace, use the following procedure:
1) Press the SCAN button. The Scan menu appears.
2) Press the SELECT button until the first trace of interest is selected.
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.
4) Press the SELECT button again until the second trace is selected.
5) Select Difference from the Math menu. A new trace is created that displays the difference between
the base trace and the selected trace. See Figure 23 which shows 1.18 ohm excess impedance due
to a slightly loosened SMA barrel adapter. The bottom bold trace is created by subtracting the top
(live) trace from the middle (scanned) trace and adjusting the vertical scale to emphasize trace
detail.
CT100B TDR Cable Analyzer Operator's Manual
41
Operating Instructions
Figure 23: Difference trace. Live (base trace, purple, top), comparison scan (red,
middle), difference (blue, bottom) traces show 1.18 ohm excess impedance (red
circle) on the live trace due to a loosened SMA connector.
3.11.12 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. To create
a first derivative trace, use the following procedure.
1)
2)
3)
4)
5)
Press the SCAN button. The Scan menu appears.
Press the SELECT button until the trace of interest is selected.
Select the Math option from the Scan menu. The Math menu will appear.
Select 1st Derivative from the menu.
A new trace is created that displays the first derivative of the base trace. See Figure 24.
Figure 24: First-derivative trace (yellow, bottom).
3.11.13 Second and Higher Order Derivative Traces
The 1st Derivative function can be applied to First Derivative traces to create second (and higher) order
derivatives.
42
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
3.11.14 Vertical Reference (Vert. Ref.) Calibration
Use the vertical reference (Vert. Ref.) system to increase the accuracy of vertical measurements, including
impedance, reflection coefficient, and return loss. The Vert. Ref. feature can be used with normal DC
connection, through impedance matching adapters, and using baluns. To calibrate with the Vert. Ref.
feature, use the following procedure:
1) Go to the MENU  Measurement menu.
2) Select the option for Vert. Ref. to display the Vert. Ref. menu.
3) Position the active cursor at the left most position where the Vert. Ref. should apply. Typically, this
will be the position where you will apply the open and short attachments in step five. This position
can be changed after the setup.
4) Select the Set Vert. Ref option.
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-ACISMM, 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. ref. will appear underneath.
A green line will appear under at the position of the active cursor (see step 3 above). Vertical reference is
applied to all points to the right of the green line. Standard vertical measurements are used for all points to
the left of the green line. The position of this line can be changed with the Vert. Ref Start menu option.
By default, the impedance value at 0 millirho is taken to be 50 Ω. This value can be changed with the Vert.
Ref. Center Imp. menu option. If you are using an impedance matcher or balun adapter, the center
impedance should be changed to the value of impedance of the adapter. For instance if using a 100 ohm
differential pulse splitter balun to measure differential impedance of twisted pair cable, then the center
impedance should be changed to 100 ohms.
The CT100B is now configured for enhanced accuracy impedance measurements across a wide range of
impedances.
The Vert. Ref. On/Off menu option can be used to toggle the vertical reference on and off as needed for a
given cable length setting.
3.11.15 Cable Resistive Loss Correction
The CT100B has a system for correcting for resistive loss (“dribble up”) in cables. This allows the operator
to measure impedance more accurately through long and/or lossy cables.
Under the Measurement menu, there is an item to set ohms per unit length and another item to toggle the
correction on and off. The calculations of this feature assume a linear serial resistance to an attached cable
and no other loss. The procedure for performing resistive cable loss correction is as follows:
1) Select the MENU  Measurements menu.
2) Select Vertical Correction submenu.
3) Adjust the trace of interest so that it fits on the screen and position the active cursor to the right
of the trace you wish to correct.
4) Select Adjust Ω/ft. (NOTE: “ft” will be the Horizontal Units set in MENU  Settings  Meas.
Settings  Horiz. Units [see Section 3.11.26.1], e.g. if set to meters, menu option will read
“Adjust Ω/m” instead.)
CT100B TDR Cable Analyzer Operator's Manual
43
Operating Instructions
5) Select Ω/ft Correct. Off to turn on the correction then press Set Ω/ft Pos. to set the correction
endpoint. The endpoint will appear as a dotted orange vertical line.
6) Rotate the M-FUNCTION knob to change the ohms per unit distance correction setting. Use the
Ω/ft Correct On toggle menu option to turn the correction on or off.
Changing the Ohms/m setting will change the slope of the cable’s trace as the resistive loss is subtracted,
and consequently the impedance readings for all points on the cable’s trace and beyond. The effect and
accuracy of the ohms per unit length value is dependent on the value for pulse velocity. The effect of
resistive cable loss correction on a relatively lossy 72 ohm RG-59 cable is shown in Figure 25 and Figure
26.
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.
Figure 25: Resistive cable loss correction, before. Note that the trace slowly rises.
Figure 26: Resistive cable loss correction, after. Note that the trace is nearly
horizontal.
44
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
3.11.16 Return Loss (S11) Traces
This feature uses precision open, short, and 50 ohm load (OSL) calibration standard measurements to
correct for systematic errors in the pulsing and sampling electronics, producing a more accurate S11 result
on the Device Under Test (DUT). The procedure for creating an S11 return loss plot is as follows:
1) Prepare the CT100B by setting the trace resolution as desired. In general, a resolution of 1-2 ps is
adequate to take advantage of the full bandwidth and frequency resolution of the instrument.
Proportionally larger sample intervals can be used for lower desired bandwidth. Smaller sample
intervals have higher frequency resolution but increase sampling time.
2) Use the M-FUNCTION knob to set the smoothing factor to an acceptable level, usually in the range
of 64 to 256 depending on the application. Use higher smoothing factors for higher bandwidth, lower
noise measurements. Higher levels of smoothing improve the signal to noise ratio (SNR).
3) With the DUT detached, place the leftmost cursor just to the left of the test plane (the location
where the calibration standards will be applied). This is usually just to the left of the open at the test
port or alternatively at the end of the phase stable cable.
4) Attach the DUT to determine the region of interest and place the rightmost cursor just to the
right of the region of interest. This is usually where steady state TDR trace amplitude has been
restored. Detach the DUT to continue calibration.
5) Select the SCAN  Math menu option to open the Math menu.
6) Select SParam & Normalize Tools. This will open the SParam & Normalize Tools menu.
7) Select S11 Calibration. After going through an informational message box, the S11 Calibration menu
will appear and the CT100B will ask for the open terminator. Attach the open terminator and press
Scan Open, or alternatively press Use Selected to use the currently selected trace as the open
calibration standard. For the best results when using type SMA terminators, use a calibrated 3.5 inlbs (0.4 Nm) torque wrench (pn: CT100-TL-TORX7) to tighten the test standards as well as the DUT.
8) Follow the same process as instructed to scan or use the selected trace for the short and 50 ohm
load calibration standards.
9) The instrument will now ask for the Measured “Device Under Test” (DUT). Press Use Live to create
a live S11 trace, Use Selected to create a static S11 trace from the currently selected trace, or Scan
Measured to scan the current live TDR trace.
10) Select the S11 return loss trace. Use the cursors to measure return loss at cursor and average return
loss between cursors.
Figure 27 shows an S11 return loss plot and TDR trace for a 2.4 GHz WiFi antenna. The return loss at 2.4
GHz (2400 MHz) is 20.9 dB.
Figure 27: S11 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.
CT100B TDR Cable Analyzer Operator's Manual
45
Operating Instructions
3.11.17 Return Loss (S11)Options
There are several mathematical transforms to apply to the S11 trace and its input traces that can, in some
cases, help reduce irregularities in the final Return Loss plot. These options can be found under SCAN 
Math  SParam & Normalize Tools  S11 Options. If the options are changed when no S11 traces exist,
then they will be applied to the next S11 trace created. Otherwise, they are applied to the last S11 trace that
was selected using the SELECT button. The options can be combined as necessary, and will change the
last selected S11 trace in real time.
3.11.17.1
Return Loss (S11) Pre-Filter
The Pre-Filter can reduce aberrations in the S11 trace. This can be combined with a Common Mode
Subtraction (CMS) transform on the input traces. To enable or disable these settings, do the following:
1) Create an S11 return loss plot using the procedure as described on page 45.
2) Select the S11 Options menu, then Pre-Filter Options.
3) Toggle Use this filter to apply filter to the S11 trace.
4) Toggle Common Mode Subtraction (CMS) to apply this option to the S11 trace.
5) Filter/CMS Offset Ratio is the start of the Aberration Filter and/or Common Mode Subtraction relative
to the S11 trace test plane. The default value is 1.66, and is ideal in most cases.
6) Frequency (MHz) is the aberration filter frequency. The default value is 200, and is ideal in most
cases.
7) Press OK to change the settings to those set above. The S11 trace will update using the new
settings.
3.11.17.2
Return Loss (S11) Post-Filter
The Post-Filter can reduce excess noise in the S11 trace. To enable or disable the setting, do the following:
1) Create an S11 return loss plot using the procedure as described on page 45.
2) Select the S11 Options menu, then Post-Filter Options.
3) Toggle Use this filter to apply filter to the S11 trace.
4) Frequency (MHz) is the noise filter frequency. The default value is 20,000 (20 GHz), and is ideal in
most cases.
5) Toggle Apply Hanning to apply a Hanning Window to the filter.
6) Press OK to change the settings to those set above. The S11 trace will update, although it might not
look visually different, depending on the settings.
3.11.17.3
Return Loss (S11) Phase Correction
Phase Corrections reduces phase error oscillation in the S11 trace. To enable or disable the setting, do the
following:
1) Create an S11 return loss plot using the procedure as described on page 45.
2) Select the S11 Options menu, then Phase Corr. Off menu option to toggle to Phase Corr. On. The S11
trace will update, although it might not look visually different, depending on the settings.
Phase Correction typically works best when started at the S11 trace test plane. To choose a different
starting point:
46
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
3) Use the SELECT button to select a TDR trace, position the active cursor where desired, then press
Phase Corr. Start. The Phase Correction starting point will go to the active cursor position, and the
S11 trace will update, although it might not look visually different, depending on the settings.
3.11.17.4
Return Loss (S11) Between Cursors
The CT100B is able to use time windowing to de-embed features in the time-domain trace for analysis in
the frequency domain using the S11 Between Cursors feature. All other time-domain features are excluded
from the analysis so that only the feature of interest is analyzed. To perform Between Cursors return loss,
use the following procedure:
1) Create an S11 return loss plot using the procedure as described on page 45.
2) Use the SELECT button to select a TDR trace.
3) Position the cursors around the feature of interest (e.g. a fault or connector).
4) Select the S11 Options menu, then Between Cursors Off menu option to toggle the S11 Between
Cursors feature on. The S11 trace may change to reflect just the features in the highlighted timedomain cursor interval.
5) Pressing the Between Cursors On menu option again will change it to Between Cursors Hold, which
will keep the time-domain region fixed while moving the time-domain cursors. Otherwise, you may
select the S11 trace to make frequency-domain measurements using the cursors without changing
the time-domain windowing.
See Figure 28 through Figure 30 for an example of an S11 return loss plot between cursors. The cursors
bracket an SMA barrel adapter between two 3 ft. segments of coaxial cable. The S11 return loss plot shows
average 35 dB loss across the connector. A loosened connector shows average loss of 29 dB across the
connector, compatible with 6 dB excess return loss compared with the tightened connector.
Figure 28: S11 between cursors bracketing an SMA barrel adapter on the TDR trace.
CT100B TDR Cable Analyzer Operator's Manual
47
Operating Instructions
Figure 29: S11 between cursors with tightened connector showing average return loss
of -28.71 dB from 422 MHz to 2.9 GHz
Figure 30: S11 between cursors with loosened connector showing average return loss
of -22.78 dB from 422 MHz to 2.9 GHz (6 dB excess return loss compared with the
tightened connector in Figure 29).
48
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
3.11.17.5
Return Loss (S11) Calibration Standards
Many precision Open, Short, and Load standards have unique offset and coefficient values included with
them. By correcting the S11 trace with these values, the error introduced by these terminators can be
reduced. To apply or change these standards, do the following:
1) Create an S11 return loss plot using the procedure as described on page 45.
2) Select the S11 Options menu, then Calibration Standards.
3) Toggle Use Calibration Kit Standards to apply offsets and coefficients to the S11 trace.
4) Set the Characteristic Impedance in Ohms. This is defaulted to 50.
5) Enter the Offsets and coefficient values provided with the Open-Short-Load Calibration Standards. If
none are provided, or they are unknown, set these values to 0.
6) Toggle Restore Defaults to disregard the values set in the table, and to use those loaded from the
CT100B internal storage. If this is checked when OK is pressed, all former values will be overwritten.
7) Press OK to change the settings to those set above. The S11 trace will update, although it might not
look visually different, depending on the settings.
3.11.17.6
Return Loss (S11) Other S11 Options
Additional miscellaneous options can be found under SCAN  Math  SParam & Normalize Tools  S11
Options  Other S11 Options, and then toggle the options desired.

OSL Bases Visible: If not checked, the Open, Short, and Load traces will be hidden after the S11
trace is created. This is to help reduce the visual clutter of the display.

Align Base Traces: If checked, and if the input traces to the S11 trace all include the internal cabling,
the input traces are aligned to the common first rise of the internal cable.
3.11.18 Improving S-Parameter Measurements
Note that testing short microwave cables directly from the test port may cause unacceptable noise in the
Cable Loss (S21) trace, or return loss trace if there is a short or open termination, due to the presence of
secondary reflections in the TDR trace. In general, this shows up as excessive spectral noise. In this case,
time windowing can be used to restore measurement accuracy:
1) Attach a 2 ft. phase stable cable to the test port of the instrument.
2) Place the leftmost cursor just to the left of the end of the phase stable cable.
3) Identify the start of the multiple reflections on the cable under test and exclude this region with the
cursors (see Figure 31).
4) Perform SParam calibration as described previously.
The time-windowed trace will have substantially reduced noise due to exclusion of the secondary
reflections.
CT100B TDR Cable Analyzer Operator's Manual
49
Operating Instructions
Calibration
Region
Figure 31: Using a phase stable cable to improve S21 insertion loss measurements
on short microwave cables. Use the phase stable cable (green arrows) 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 arrows) so that they are
excluded.
3.11.19 Smith Charts
The Smith chart is a useful graphical tool for plotting reflection coefficients and complex impedance values
and can be used to simplify impedance matching. For a very brief introduction to smith charts see section
5.12. The CT100B allows the operator to display S11 return loss and cable loss traces on a Smith chart. To
create a Smith chart, use the following procedure:
1)
Create an S11 return loss plot using the procedure as described on page 45.
2) With the S11 trace selected, adjust the cursors to minimum and maximum frequency desired on the
Smith Chart.
3) Select Smith Chart option to toggle Smith chart display.
4) Use the HORIZONTAL POSITION knob to move the cursor along the complex impedance curve.
Figures Figure 32-Figure 35 show Smith chart representations of an open, short, resistive 50 ohm load, and
a reactive 200 ohm load.
Figure 32: Smith chart representation of open fault (red arrow).
50
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
Figure 33: Smith chart representation of short fault (red arrow).
Figure 34: Smith chart representation of a 50 ohm resistive load (red arrow).
Figure 35: 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).
CT100B TDR Cable Analyzer Operator's Manual
51
Operating Instructions
3.11.20 Normalized TDR Traces
This process creates a normalized TDR trace based on a calibrated S11 return loss trace. A normalized TDR
trace appears as another trace in the region of S11 calibration. The normalized trace should be cleaner than
the Measured DUT trace, with fewer aberrations. The normalized trace also has an adjustable rise time to
help the operator determine what effect a particular cable fault will have on signals with differing rise times.
The following procedure creates a normalized TDR trace:
1) Create an S11 return loss plot using the procedure as described on page 45.
2) From the SParam & Normalize Tools menu, select Apply Normalization.
3) Select Normalize Pulse Rise Time and use the M-FUNCTION knob to select a suitable rise time for
the cable system as applicable. Note that selecting a rise significantly shorter than the native rise
time of the TDR instrument will result in a degraded trace.
4) Note that the S11 Options, such as the Between Cursors On/Off setting is used by the TDR
normalization process. If Between Cursors mode is turned on, the normalized trace information will
be taken from the time-windowed S11 trace.
Figure 36 shows a normalized TDR trace (blue) with a short fault in a 50 ohm cable. The normalized trace
shows reduced aberrations and more accurate relative reflection coefficient and impedance after the fault
compared with the live TDR trace.
Figure 36: Normalized trace (blue, bottom) showing short fault in a 50 ohm cable.
3.11.21 Vertical Units
The CT100B is able to change vertical units of the live TDR trace so that it is displayed in units of reflection
coefficient (milli-rho), impedance (ohms) or Voltage Standing Wave Ratio (VSWR). To change vertical
units, use the following procedure:
1) Select MENU  Measurements menu.
2) Select Vert. Units to toggle through the different options.
Example trace with impedance (ohms) as the vertical unit is shown in Figure 37. 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.
52
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
Figure 37: TDR trace with impedance vertical units (red, top) demonstrating vertical
scale in ohms and emphasis of the open fault at the end of the cable. The black trace
uses reflection coefficient (millirho) as its vertical units.
3.11.22 Layer Peeling (Dynamic Deconvolution) Traces
The CT100B includes the capability to perform layer peeling / dynamic deconvolution. This is a useful
technique for improving impedance accuracy by removing the effects of multiple reflections caused by
impedance discontinuities along the length of the cable. In general, any impedance discontinuity creates
both forward (transmission) and backwards (reflection) waves. If reflected off other impedance
discontinuities, these reflected waves will constructively or destructively interfere along the length of the
TDR trace, leading to impedance measurement errors. The CT100B Layer Peeling feature iteratively
extracts the underlying reflection coefficients as described in Section 5.14. For a more detailed description
of layer peeling, see section 5.14. To create a Layer Peeling trace, use the following procedure:
1) Position the TDR trace on the screen so that the region of interest is visible with a portion of 50 ohm
cable visible at the left hand of the screen (use the CT100B’s internal 50 ohm cable if needed).
2) Use the HORIZONTAL POSITION knob to place the active cursor on the 50 ohm cable at the left
side of the screen.
3) Select SCAN  Math menu.
4) Select Layer Peeling menu option.
An example of a Layer Peeling trace is shown in Figure 38, which depicts a multi-segment cable of varying
impedance (50-125-75-63 ohms) with an open fault at the end. The corrected impedance of the final
segment is within 2-3 ohms of the actual value, which represents ~80% reduction in impedance error when
compared with the uncorrected live TDR trace.
CT100B TDR Cable Analyzer Operator's Manual
53
Operating Instructions
Figure 38: Example Layer Peeling trace (yellow, bottom) versus live TDR trace
(white, top). The layer peeled trace reduces impedance error in the final cable
segment (green arrows) by ~80%.
3.11.23 Fast Fourier Transform (FFT) Traces
The CT100B can calculate FFT frequency domain information from live and scanned TDR traces. FFT
traces can be used to show the frequency domain content of a trace or portion of a trace between cursors,
and comparisons of FFT traces can be used to demonstrate differences and/or changes in frequency
content, such as between different types of connectors or cable faults. To create an FFT trace, use the
following procedure:
1) Select the live trace with the SELECT button.
2) Use the CURSOR button and the HORIZONTAL POSITION knob to set the boundaries for the FFT
with a cursor at either end.
3) Press the SCAN button, and then select Math  FFT Tools.
4) Select Apply FFT. The CT100B will now take a high resolution scan of the live trace between the
cursors, and then convert the scan into an FFT plot.
FFT traces can be stored and loaded, just like normal scanned traces.
3.11.24 Remote Control
Using the accompanying CT Viewer™ 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.
Refer to section 4.1.3 Send Saved Traces and Use Remote Control with Ethernet and section 4.1.4 Use
Remote Control for instructions on connecting CT Viewer to the CT100B and enabling remote control.
Please consult the CT Viewer Quick User Guide for more information about using remote control and
manipulating a remote TDR trace.
3.11.25 Cable Type Library
The CT100B has a library of common cable types and associated velocities of propagation. Vp for these
cable types can be loaded from the library.
54
CT100B TDR Cable Analyzer Operator's Manual
Operating Instructions
3.11.25.1
Load a Cable Type's Vp
To load a cable type, follow this procedure:
1) Press the FILE button. The File menu appears.
2) Select Reference Cable Type from the menu. An interface appears that allows you to scroll through
the cable types with the M-FUNCTION knob.
3) Highlight the desired cable type and press Select. Vp is now set to the value for that cable type.
3.11.25.2
Custom Cable Types
The CT100B is also able to save and load custom cable types. Use the following procedure to save a
custom cable type:
1) Press the FILE button. The File menu appears.
2) Select the Custom Cable Types menu option to access user-editable cable types with menu options
Add New and Select.
3) When Add New is selected, a window appears for entering a cable type name, a Vp for velocity of
propagation, and an expected characteristic impedance for the cable. When the window first
appears, Vp will be set to the current system Vp, while impedance defaults to 50 ohms.
Use the M-FUNCTION knob and the Select menu option to load a particular cable type. When selected, the
operating Vp is changed to match the selected cable type.
The user-added cable types are stored and accessed separately from the standard cable types, which are
available through the Reference Cable Types menu item.
3.11.26 Other Measurement Settings
3.11.26.1
Change Horizontal Units
Horizontal distance measurements can be displayed in meters, centimeters, feet, inches, or yards.
1) Select the MENU  Settings  Meas. Settings menu.
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.
3.11.26.2
Fine Vp Control
By default, the CT100B displays three decimal places for Vp; however, the CT100B can display six decimal
places for Vp when very precise distance measurements are needed.
1) Select the MENU  Settings  Meas. Settings menu.
2) Select Vp 3 Sig Figs from the menu to toggle the option to Vp 6 Sig Figs. The CT100B will display 6
decimal places for the Vp readout on the screen when Vp 6 Sig Figs is shown on the menu.
3) When the CT100B is in Vp 6 Sig Figs mode, a new function, Fine Adj. Vp, is added to the
M-FUNCTION knob. When the M-FUNCTION knob is set to Fine Adj. Vp, turning the knob will
change the Vp value by the 6th significant digit. The Vp value can be changed by thousandths by
setting the M-FUNCTION knob to the Coarse Adj. Vp function.
CT100B TDR Cable Analyzer Operator's Manual
55
Operating Instructions
3.11.26.3
Relative Reflection Coefficient (RRC) Method
The CT100B measures the relative reflection coefficient between cursors. When the two cursors of the
CT100B are positioned on either side of a change in impedance, this measurement is the reflection
coefficient for that change. By default, the value is displayed in Classic mode, displaying the true reflection
coefficient relative to the signal at the input of the reflection. The CT100B can also measure in 1502C mode,
which displays a reflection coefficient relative to the signal at the input of the cable.
1) Select the MENU  Settings  Meas. Settings menu.
2) Select RRC Classic Mode from the menu. This will toggle the CT100B between the Classic RRC
calculation and the 1502C calculation as displayed on the screen.
3.11.27 User Configurations
The CT100B allows the user to save individually named instrument configurations. A saved configuration
stores the values of all instrument settings that can influence trace measurements. A configuration can be
called up by its name, restoring all settings to the values saved in that configuration.
User Configurations can reduce operator error when configuring the TDR to make important measurements.
For this reason it is recommended that User Configurations be used when setting up the CT100B for
important measurements, such as quality-control checks on a cable manufacturing line.
3.11.27.1
Save Configurations
1) Press the FILE button. The File menu appears.
2) Select the Load/Save Config 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. See Navigating dialog
boxes on page 14 for information on using the Keyboard menu.
3.11.27.2
Load Configurations
1) Press the FILE button. The File menu appears.
2) Select the Load/Save Config menu item. The User Configurations library is displayed.
3) Scroll through saved configurations with the M-FUNCTION knob.
4) Press Select to load the highlighted configuration. All settings saved in that configuration are
automatically restored. Measurements and traces are updated to reflect the new Vp, cursor position,
and other applicable settings.
56
CT100B TDR Cable Analyzer Operator's Manual
4
CT Viewer™
The CT Viewer™ 2.0 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 traces.
This software package will also allow the user to create reports and print plots that can be imported into
Microsoft® Word® or other word processing or report creation software to create files of traces suitable for
transfer to others and to load trace files created by others.
This section covers how to transfer saved TDR traces to CT Viewer. For more detailed information on
installing and using CT Viewer, please see the CT Viewer Quick User Guide.
4.1
Sending Saved Traces to a Computer
When a scanned trace is saved to the CT100B, it can be sent to a computer that has CT Viewer™
installed.
4.1.1
Send Saved Traces with a Thumb Drive
1) Insert a USB drive into a USB port on the front of the CT100B. Wait until the USB drive icon
appears on screen.
2) Press the FILE button to bring up the File menu.
3) Choose the Cable Scan Records menu option. A window listing all of the traces saved to the
CT100B appears.
4) Use the M-FUNCTION knob to select a trace to send to the USB drive. Alternatively use Toggle
Selected and Mark All to select multiple or all traces, respectively.
5) Choose Export  USB from the menu. The select trace(s) will now be written to the USB drive.
6) Remove the USB drive for the CT100B and insert the drive into a USB port on the computer.
7) Start CT Viewer, and from the File menu in CT Viewer, select Load from File.
8) Select the scan file name(s) of interest from the thumb drive. The trace will be loaded into CT
Viewer and shown on the screen.
4.1.2
4.1.2.1
Send Saved Traces over USB
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™. It is possible to skip this step during the installation. If the drivers
aren’t installed, Windows will inform the user when the CT100B is connected over USB.
4.1.2.2
Send the Traces
1) Start CT Viewer and connect the computer to the CT100B with a standard USB type A to USB type
B cable. Connect to the USB type B port on the back of the CT100B.
CT100B TDR Cable Analyzer Operator's Manual
57
CT Viewer™
2) Go to the File menu in CT Viewer and select Open Tester. A screen will appear that will show the
serial number of the connected CT100B and a list of all traces saved on the CT100B.
3) Select a trace to transfer by clicking with the mouse. Select multiple traces by holding down the
SHIFT or CTRL key while clicking with the mouse
4) Select the TRANSFER TO button to send the traces to CT Viewer™. The traces will also be shown
on the screen.
4.1.3
4.1.3.1
Send Saved Traces and Use Remote Control with Ethernet
Setup Ethernet
In order to send traces over Ethernet to a computer, both the computer and the CT100B need to be setup
for the network. Depending on the how your network is configured, the default settings for the CT100B may
work. If not, have your network administrator setup the network settings for the CT100B and the computer.
The CT100B network settings are located at MENU  Settings  Network Settings. The CT100B can get
a configuration through DHCP, or it can be setup with Static Network Settings (see Section 3.11.24).
4.1.3.2
Connect to CT Viewer – First Steps
1) Make sure both the computer and the CT100B are plugged into the network. The CT100B Ethernet
plug is found on the back of the CT100B. The light on the CT100B Ethernet port should illuminate.
2) Start CT Viewer on the computer.
3) On the CT100B, navigate to MENU  Connect to CT Viewer. See Figure 39: Connect to CT
Viewer menus.The Find CT Viewer menu button will scan the local network looking for a PC
running the CT Viewer 2 program.
4) Or you can use the Manual Connect option to reconnect to a server you have used in the past or
one that is not on your local network. See Figure 40: Connect to CT Viewer window.
Figure 39: Connect to CT Viewer menus.
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) Use the M-FUNCTION knob to move up and down in the window. Use the on screen keyboard or a
USB keyboard to enter values. In Server Name, enter a user friendly name for the computer.
3) In Server Address, enter either a network name, or an IP address for the computer.
4) Do not change the default port number.
58
CT100B TDR Cable Analyzer Operator's Manual
CT Viewer™
5) Press OK to save the server entry, then press Select to connect. If the connection is successful, a
message will appear in CT Viewer.
Figure 40: Connect to CT Viewer window.
4.1.3.4
Connecting After the First Time
1) Navigate to the MENU  Connect to CT Viewer menu. A window showing all the stored server
connections will appear.
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.
4.1.3.5
After Connecting
1) Go to the File menu in CT Viewer and select Open Tester. A screen will appear that will show the
serial number of the connected CT100B and a list of all traces saved on the CT100B.
2) Select a trace to transfer by clicking with the mouse. Select multiple traces by holding down the
Shift or Ctrl key while clicking with the mouse.
3) Select the TRANSFER TO button to send the traces to CT Viewer™. The traces will also be shown
on the screen.
4.1.4
Use Remote Control
After the CT100B has connected to a computer over Ethernet using the steps in section 4.1.3, go to CT
Viewer and select Remote Control  Connect.
Once Remote Control has been established, a new, live trace will appear in CT Viewer. This trace will be
identical to the trace on the CT100B screen. It can be moved around or scaled just like any other trace in
CT Viewer.
Normally the CT100B screen goes blank during remote control. To turn on the CT100B screen at the same
time as Remote Control, select Remote Control  Assist Mode in CT Viewer.
4.1.5
Record and Playback Real-Time TDR Trace Movies
CT Viewer can record a real-time movie of the TDR trace, useful for detecting and characterizing transient /
intermittent faults. To record a real-time movie of the CT100B trace, connect to the CT100B as described in
the previous section, and then select Remote Control  Record to File. You will be prompted to enter a
filename for the recording. Select Stop to stop the recording. To view the individual TDR traces saved in
CT100B TDR Cable Analyzer Operator's Manual
59
CT Viewer™
the movie, select the movie file and use the > and < keys to step forward and backward in the file. The time
stamp of the trace is shown as part of the trace label.
60
CT100B TDR Cable Analyzer Operator's Manual
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”. Assuming a transmission line such as a cable with uniform geometry, the test signal propagates
with a characteristic velocity such that the time can be related to distance. The changes in reflected voltage
in a TDR trace with respect to time correspond to distance from the test port to impedance changes.
Cable or connector faults are regions where the measured reflection coefficient and associated impedance
are outside of manufactured specification. Cable faults are almost always broadband with preferential
attenuation of higher frequencies, and indicate one or more of the following problems:
1) Change in the geometry of the conductors with respect to one another,
2) Change in the dielectric properties of the insulator, and/or
3) Partial or complete interruption in one or both of the signal conductors.
Cable faults are important because they degrade signal quality. Short or open faults completely disrupt
signal transmission. In many ways such “hard” faults are helpful because they are easy to diagnose.
However more subtle partial or “soft” faults cause portions of the signal energy to be reflected and/or
delayed, contributing to noise. This can show up as reduced bandwidth in microwave/RF cable systems
and increased bit error rates in digital cable systems.
Multiple small faults that are individually insignificant with respect to noise may contribute in an additive
fashion to exceed the overall “noise budget” of the cable assembly. Because TDR typically measures the
transmission line with sensitivity well below the bit error threshold of most communications systems, it is
useful to find these “insignificant” faults and deviations from manufactured specification that may contribute
to signal integrity problems.
5.2
Reflection Coefficients
The amplitude of reflected voltage at a particular location in a TDR waveform is determined by the
reflection coefficient at that location. The CT100B displays reflection coefficient in the upper right hand of
the screen with units of millirho (mρ) and relative reflection coefficient with prefix of “RRC”.
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, Γ) is related to the impedance
change () at a given point in a cable according to:
Γ=
CT100B TDR Cable Analyzer Operator's Manual
 − 
 + 
61
TDR Measurement Theory
Where ZL is the impedance of the load (e.g., the device under test [DUT]) and ZS is the source impedance
of the TDR, typically 50 ohms but potentially other values if an impedance matching adapter is being used.
The reflection coefficient uses units of rho (ρ) or millirho (mρ).
Note that the reflection coefficient (Γ) is a complex variable with unique amplitude and phase for each
frequency. However, when measuring reflection coefficient directly from a TDR trace the measured value is
the average reflection coefficient over all frequencies in the incident and reflected test signal.
The CT100B is also able to measure and display frequency-domain complex reflection coefficient values in
the context of S11 return loss and cable loss plots such as those produced with Vector Network Analyzer
(VNA) and Frequency Domain Reflectometer (FDR) equipment. This is discussed further on page 69.
5.3
Common Types of TDR Cable Faults
Open faults appear as a pulse upward in the TDR trace (Figure 41) because the fault reflects all of the
incident step energy in-phase with the test signal.
Figure 41: An open cable fault shows an upward step edge at the location of the
fault.
Short faults appear as a pulse downward in the TDR trace because the fault reflects all of the incident step
energy 180⁰ out-of-phase with the test signal (Figure 42):
Figure 42: A short cable fault shows a downward step edge at the location of the
fault.
62
CT100B TDR Cable Analyzer Operator's Manual
TDR Measurement Theory
Short or open faults measured through long lengths of cable (hundreds of feet) will show long, shallow
reflections on the TDR trace because the cable preferentially attenuates higher frequencies in the test
signal, degrading the rise or fall time of the reflected fault. Figure 43 demonstrates a TDR trace with an
open fault at the end of an 815 ft. RG-6 coaxial cable with long, shallow reflected rise caused by cable
attenuation of high frequency components of the step pulse.
Figure 43: An open cable fault at 815 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.
Normal connectors will show up as an impedance discontinuity simulating a small fault. Depending on the
type and quality of the connectors, the expected impedance variation will differ, as shown in Figure 44 and
Figure 45 for SMA and BNC type connections. Connector damage and corrosion can change the
impedance profile of a connector over time, typically increasing the excess impedance of the connector.
Periodic surveillance with TDR can be used to confirm connector performance.
Figure 44: Normal SMA female barrel interconnect measuring ~0.4 ohms.
CT100B TDR Cable Analyzer Operator's Manual
63
TDR Measurement Theory
Figure 45: Comparison of typical SMA (red trace, bottom and arrow) and BNC (black
trace, top and arrow) coaxial cable interconnects.
Soft / partial faults typically will not appear at the end of the trace after pressing the AUTOFIT button, but
instead can appear anywhere along its length.
Any fault has the potential to reduce the incident pulse strength for subsequent cable faults and may
change the apparent velocity of propagation. The accuracy of the Distance-to-Fault measurement of a fault
that appears beyond another fault is reduced.
5.4
Velocity of Propagation (VoP, Vp)
As mentioned in previous sections, a transmission line such has a cable has uniform geometry with a
characteristic signal propagation velocity. This velocity of propagation (Vp), also sometimes abbreviated
VoP or VP, and sometimes also called the velocity factor (VF) or wave propagation speed, is the measure
of the velocity of an electrical signal within a cable expressed as a fraction of the speed of light in a
vacuum. With the CT100B, Vp can be set between 0.250000 and 1.000000.
Nominal Vp values for most types of cable can be found in the manufacturer’s data sheet, and Appendix E
contains nominal values for a variety of commonly used cable types. These values can be a good start for
basic cable Distance-to-Fault measurements, however 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 manufacture. In addition, cable aging due to temperature, radiation, or other environmental
parameters may alter the original characteristic velocity of propagation for a given cable. For this reason, if
accuracy is particularly important for a particular cable Distance-to-Fault measurement, it is generally a
good idea to establish a known Vp for a sample of the specific cable under test.
The velocity of propagation (Vp) is related to the dielectric constant (relative permittivity,  ) of the dielectric
medium according to:
 ~
1
√
Velocity of propagation is also related to the distributed inductance () and shunt capacitance () of a
lossless transmission line according to:
 =
64
1
√
CT100B TDR Cable Analyzer Operator's Manual
TDR Measurement Theory
5.5
Distance-to-Fault (DTF) and Cable Length
Once the operator identifies an impedance discontinuity such as a cable fault or open or short cable
termination, the distance to the fault (D) is related to the velocity of propagation (Vp), the speed of light (c),
and the measured round-trip time (t) to the fault, according to:
=
 ∙  ∙ 
2
The product is divided by 2 because the CT100B measures the time for the pulse to travel to and from the
point of interest.
5.6
Impedance
As mentioned previously, TDR instruments measure reflection coefficient essentially but must calculate
impedance according to:
() = −
Γ() + 1
Γ() − 1
Where () is the impedance at time ,  is the source impedance, Γ() is the reflection coefficient at .
This is the basis for the CT100B ohms-at-cursor measurements and ZTrace impedance traces. It is
important to note that impedance is nonlinear with respect to reflection coefficient, as shown in Figure 46.
CT100B
Figure 46: Relationship of impedance (ohms) to reflection coefficient (rho) for 50 ohm
source impedance (marked by red circle).
Because TDRs measure reflection coefficient, noise and uncertainty on a TDR trace is in units of millirho,
not ohms. Given a fixed amount of uncertainty in reflection coefficient, the corresponding impedance
CT100B TDR Cable Analyzer Operator's Manual
65
TDR Measurement Theory
uncertainty will be low at impedances less than the TDR source impedance (typically 50 ohms) and
increasingly larger and nonlinear for impedance values greater than the TDR source impedance.
The CT100B factory calibration provides typical vertical accuracy of approximately 0.1 ohm near 50 ohms
and approximately 10-20 ohms near 1000 ohms for most cable testing applications. When impedance
measurements are very important, accuracy can be improved using Vert. Ref. (page 43) and normalized
TDR traces (page 52).
5.7
Return Loss
Return loss is another way of measuring impedance change in a cable. Return loss is given in decibels
(dB) and is always calculated using the relative reflection coefficient. Return loss is related to the reflection
coefficient Γ by the formula:
  = −20 ∙ 10 |Γ| dB
The larger the fraction of energy in the reflected signal, the lower the numerical return loss value, so that an
open or a short that returns 100% of the signal has a return loss of 0 dB. A very low loss cable will have a
large return loss in dB. Likewise a 50 ohm cable terminated with a perfect 50 ohm load will have very large
return loss in dB. This relationship is shown in Figure 47.
Return loss measured directly from a CT100B TDR trace represents the average return loss over all
frequencies in the step-rise test signal. The CT100B can measure TDR return loss at cursor and relative
return loss between cursors and optionally displays these values at the right hand of the screen in units of
dB, with prefix of “RRL” for the relative return loss measurement.
The CT100B is also able to measure complex frequency-specific S11 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 69.
Figure 47: Relationship of return loss (dB) to reflection coefficient (rho).
66
CT100B TDR Cable Analyzer Operator's Manual
TDR Measurement Theory
5.8
VSWR
Voltage standing wave ratio (VSWR) is a way of displaying reflection coefficient in a nonlinear way that
emphasizes changes in cable impedance. VSWR is the voltage standing wave ratio and is related to the
reflection coefficient Γ according to:
 =
1 + |Γ|
1 − |Γ|
VSWR measures the ratio of the maximum-over-time amplitude of the nodes and anti-nodes of the
standing wave off of a reflection. If there's no reflection (e.g. 50 ohm termination), VSWR will be 1. If all
energy is reflected (e.g. short or open fault), VSWR goes to infinity. This relationship is shown in Figure 48.
VSWR is a unitless, scalar value.
The CT100B displays two different VSWR values at cursor. The first, VSWR, is calculated from the total
reflection relative to the CT100B test port source impedance (50 ohms). The second, RVSWR, is
calculated from the reflection between the two cursors. In other words, VSWR is based on the millirho
reflection coefficient, while RVSWR is based on the RRC, relative reflection coefficient calculation. There
are menu options in the Display menu to toggle the display of VSWR and RVSWR.
Figure 48: Relationship of voltage standing wave ratio (VSWR) to reflection coefficient (rho).
VSWR for 50 ohm load is shown by the red circle.
5.9
Rise Time and Spatial Resolution
Spatial resolution is defined by the ability of the operator to distinguish the presence of two closely spaced
faults on a TDR waveform. An accepted rule of thumb is that the limiting spatial resolution of a TDR
instrument is approximately ½ of the system rise time (10-90%). This is the time required for the step signal
reflected from an open or short termination to transition from 10% to 90% of the final step amplitude. For a
TDR with 100 ps system rise time, the estimated spatial resolution R is approximately:
CT100B TDR Cable Analyzer Operator's Manual
67
TDR Measurement Theory
≅
1
∙  ∙  ∙  = 10 
2
where c is the speed of light,  is the system rise time, and velocity of propagation Vp is taken to be 0.66.
Faster system rise times allow a given TDR instrument to more faithfully represent partial cable faults such
as shield nicks or kinks, as shown in Figure 49. This figure depicts a simulation of 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. The 800 ps rise time TDR detects only
a single fault and grossly underestimates the severity of the fault.
Figure 49: Simulated comparison of a 90 ps rise time TDR (green) and an 800 ps TDR (red) with
respect to the ability to depict two 1 cm long, 75 ohm faults spaced 1 cm apart on a 50 ohm cable.
Notice how the faster TDR (90ps) resolves each fault individually. The blue lines represent a
theoretically perfect response.
5.10
Timebase / Cursor / Horizontal Resolution
Timebase, cursor, or horizontal resolution refers to the horizontal spacing of samples along the TDR trace.
In order to faithfully depict the TDR profile of a connector or cable fault, the cursor resolution should be at
least 5-10 times higher than the spatial resolution. For the example shown in Figure 49, it is unlikely that
the cursor resolution for the slower rise time instrument would be adequate to reliably depict the fault in the
first case.
Cursor resolution also comes into play when precise length or phase matching of cables is being carried
out, in which the cursor resolution must be sufficient to adequately depict the difference in length between
cables. Typically the cursor resolution should be 10 times higher than the intended length accuracy.
68
CT100B TDR Cable Analyzer Operator's Manual
TDR Measurement Theory
With respect to frequency domain measurements, very high cursor resolution ensures adequate frequency
bandwidth because the number of sampled data points in the time-domain translates into frequency
resolution in the frequency domain.
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.
According to convention, the scattering parameter Sxy represents the response of the network in terms of
reflected and/or transmitted voltages at port x in response to excitation of port y. S11 and S22 are the
complex reflection coefficient matrices of port 1 and 2, respectively. S21 and S12 are the forward and
reverse complex voltage gain matrices for port 1 and port 2, respectively.
Considering a 2-port network with incident voltage waves a1 = V1+ and a2 = V2+ and reflected waves being
b1 = V1- and b2 = V2-, the 2-port S-parameter matrix is described by:


( 1 ) = ( 11
21
2
12 1
)( )
22 2
Solving for S11 gives:
11 =
1 1−
=
1 1+
21 =
2 2−
=
1 1+
Solving for S21 gives:
Passive networks like cables, splitters, attenuators, and combiners can be considered reciprocal networks
such that S11 = S22 and S21 = S12. One-port measurements can be used to characterize the return loss
(S11/S22) and insertion loss (S21/S12) of a variety of 2-port passive networks such as cables as discussed
under the following Cable Loss section.
You can measure S-parameters directly in the frequency domain using a VNA instrument and indirectly in
the time-domain using a TDR instrument. The TDR instrument then performs a discrete Fourier transform
(DFT) operation to decompose a TDR trace into the frequency domain.
When calibration is performed at the test plane using open, short, and 50 ohm load (OSL) terminations, the
CT100B is able to mathematically subtract systematic errors in the pulser and sampler electronics from the
measured trace, improving S-parameter accuracy.
S-parameters measured with TDR instruments are accurate with sufficient dynamic range for most
applications. Figure 50 shows a comparison of return loss for a 2.4 GHz WiFi patch antenna measured
using a handheld VNA and CT100HF TDR. The TDR-derived return loss measurements show good
CT100B TDR Cable Analyzer Operator's Manual
69
TDR Measurement Theory
accuracy from DC to approximately 8.3 GHz. Both spectra clearly show the 2.4 GHz bandpass region
expected for a 2.4 GHz WiFi antenna.
Figure 50: Comparison of S11 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
Return Loss (S11)
The complex return loss S11 is expressed as:
   = −20 ∙ log10 |11 |
5.11.3
Insertion Loss (S21)
The complex insertion loss S21 is expressed as:
   = −20 ∙ log10|21 |
True 2-port insertion loss measurements require a 2-port instrument; however the Cable Loss
measurement described below uses the reciprocity feature of passive networks to determine insertion loss
from cables and other suitable 2-port networks using a 1-port test instrument.
5.11.4
Cable Loss (S21)
Cable insertion loss in dB is additive per unit length. Assuming that port 2 of a 2-port DUT (e.g. a coaxial
cable) is terminated with a short (or open) adapter such that all (or nearly all) of the incident voltage trace is
reflected back to the TDR instrument. Insertion loss (S21) is half of the corresponding S11 return loss
measurement in dB:
70
CT100B TDR Cable Analyzer Operator's Manual
TDR Measurement Theory
   =


2
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. However
for many applications it is more than adequate.
5.12
Smith Charts
The impedance Smith chart is a useful graphical tool for visualizing complex impedances and scattering
parameters according to Figure 51. The CT100B includes Smith chart functionality that can be used to
simplify transmission line troubleshooting and impedance matching as described in Section 3.11.19.
Figure 51: Impedance Smith chart relationships.
5.13
Normalized TDR Traces
The S-parameter OSL calibration process mathematically models the TDR pulser-sampler system as a
two-port error network and subtracts systematic pulser-sampler errors from the S11 matrix. Convolution of
the S11 matrix with an idealized Gaussian step or other idealized excitation signal allows the CT100B to
create and display a normalized TDR trace. The normalized TDR trace has lower aberration and improved
impedance accuracy compared with the original TDR trace.
Although cable fault detection is the most sensitive when using an excitation signal with the fastest rise
time possible, by changing the rise time of the Gaussian step, the importance of a given cable or connector
fault can be estimated at different signal rise times and bandwidths. For instance if the cable under test is
typically used with 1 ns rise time signals, the severity of a cable fault can be determined by using a 1 ns
rise time normalized TDR trace. Localized cable faults will always appear less severe when examined
using slower rise time excitation signals.
CT100B TDR Cable Analyzer Operator's Manual
71
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.
As implemented in the CT100B (see Section 3.11.22), the layer peeling method iteratively examines the
TDR trace at each time step and attempts to correct for forward and backward signal propagation to extract
impedance values at each time step. This is diagrammed in Figure 52 showing measured voltages v(t)
taken from the TDR trace and their relationship to actual reflection coefficients (Γ) at time (t) and
impedance values (Zx) at different physical distances. The diagram shows that for each time step forward
in the TDR trace, there are increasingly complex contributions from forward and backward reflections as
they interact with each new impedance boundary.
For instance, the test signal moving forward from the Z0/Z1 impedance boundary is reduced by the energy
reflected by the Z0/Z1 boundary. Likewise the Z1/Z2 impedance boundary is “tested” by the original TDR
test signal at time t1 but also interacts with reflected signals at every subsequent time point due to internal
reflections in the cable. The layer-peeled TDR trace partially corrects for the presence of these multiple
reflections and provides more accurate impedance values. This effect is most pronounced when there are
multiple large impedance transitions in a cable assembly and at short and open faults.
Figure 52: Layer peeling scattering diagram relating measured TDR trace (V[t]) to
actual impedance changes (Z[x]) and their associated actual reflection coefficients
(Γ[x,t]).
72
CT100B TDR Cable Analyzer Operator's Manual
6
6.1
Options and Accessories
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
Standard BNC Accessories -- CT100B (BNC)
BNC 50 ohm 36 in. Reference Cable
SMA 50 ohm Terminator
Connector, SMA female to BNC male
BNC Female to Female Adapter
BNC Male to Male Adapter
BNC Shorting Cap
24 VDC External Charger/Power Supply
Operator's Manual, Printed
CT Viewer™ 2 Quick User Guide, Printed
CT Viewer™ 2 Installation DVD, w/ Digital Operators
and CT Viewer™ 2 Manuals
Soft Carrying Case
NIST-Traceable Calibration with Certificate
6.2.2
CT100-AC-W536
CT100-AC-ER50-S
CT100-AC-ISFBM
CT100-AC-IBFF
CT100-AC-IBMM
CT100-AC-IBS
CT100-AC-PS
CT100B-M-OM-xxx*
CT100-M-CTVM-xxx*
CT100-S-CTV2-xxx*
CT100-AC-CS
CT100-AC-NISTCC
Standard SMA Accessories -- CT100B (SMA), CT100HF
SMA 50 ohm 36 in. Reference Cable
SMA 50 ohm Terminator
SMA Male to Male Adapter
Connector, SMA female to BNC male
Connector, SMA male to BNC female
Connector, SMA Female Short
SMA Shorting Cap
24 VDC External Power Supply
Operator's Manual, Printed
CT Viewer™ 2 Quick User Guide, Printed
CT Viewer™ 2 Installation DVD, w/ Digital Operators
and CT Viewer™ 2 Manuals
CT100B TDR Cable Analyzer Operator's Manual
CT100-AC-W536-S
CT100-AC-ER50-S
CT100-AC-ISMM
CT100-AC-ISFBM
CT100-AC-ISMBF
CT100-AC-ISSF
CT100-AC-ISS
CT100-AC-PS
CT100B-M-OM-xxx*
CT100-M-CTVM-xxx*
CT100-S-CTV2-xxx*
73
Options and Accessories
Soft Carrying Case
NIST-Traceable Calibration with Certificate
6.2.3
CT100-AC-CS
CT100-AC-NISTCC
Optional accessories
24 VDC Isolated External Power Supply
Hard Carrying Case (Pelican)
MIL‐STD‐1553B / TRB Adapter Kit
OSL S-Parameter Calibration Kit SMA
OSL S-Parameter Calibration Kit N
3.5 ft-lbs (0.4 Nm) Torque Wrench
Phase‐Stable Cable 2 ft. SMA(M‐M)
Phase‐Stable Cable 2 ft. SMA(M‐F)
Phase‐Stable Cable 2 ft. BNC(M‐M)
Phase‐Stable Cable 2 ft. BNC(M‐F)
Phase‐Stable Cable 2 ft. BNC(M)-SMA(F)
Small Form Factor CE Keyboard
Clear Screen Protector Pack
Anti-Glare Screen Protector Pack
BNC Adapter Kit
SMA Adapter Kit
Impedance Matching Kit 75,93,125 ohm (BNC)
Impedance Matching Adapter, 50 to 75 ohm (BNC)
Impedance Matching Adapter, 50 to 93 ohm (BNC)
Impedance Matching Adapter, 50 to 125 ohm (BNC)
Internal Battery (2700 mAh NIMH, 12 AA cells, 14.40 V, 38.88 Wh)
6.2.4
CT100-AC-PSI
CT100-AC-CH
CT100‐AK‐TRB
CT100‐AK‐CALSMA
CT100‐AK‐CALN
CT100-TL-TORX7
CT100‐AC‐PSCSMSM24
CT100‐AC‐PSCSMSF24
CT100‐AC‐PSCBMBM24
CT100‐AC‐PSCBMBF24
CT100‐AC‐PSCBMSF24
CT100-AC-KBD
CT100-AC-SPC
CT100-AC-SPAG
CT100-AK-BNC
CT100-AK-SMA
CT100-IK-BNC
CT100-AC-I5075-BNC
CT100-AC-I5093-BNC
CT100-AC-I50125-BNC
CT100-AC-B2700
Service accessories (CT100B / CT100HF)
Technical Manual, Printed
Technical Manual, Digital w/ CT Viewer™ Installation
CT100B-M-TSM-xxx*
CT100-S-CTVTSM-xxx*
* xxx applies to revision number. Accessory part number is incremented per revision.
74
CT100B TDR Cable Analyzer Operator's Manual
Appendix A
A.1
Specifications
Electrical Specifications
Characteristic
Specification
Notes
Reflected rise time, CT100B 10-90%
150 ps typ, 200 ps max
10 to 90%, into 50 ohms
Reflected rise time, CT100B 20-80%
100 ps typ, 150 ps max
20 to 80%, into 50 ohms
Reflected rise time, CT100HF 10-90%
100 ps typ, 130 ps max
10 to 90%, into 50 ohms
Reflected rise time, CT100HF 20-80%
60 ps typ, 90 ps max
20 to 80%, into 50 ohms
Jitter
15 ps max (peak-to-peak)
< 1 ps rms typ.
Output impedance
50 Ω ±2%
Pulse amplitude
300 ±10 mV
Averaged value into 50 ohms
Pulse width
Fixed: 1.000-2.000,5.000-6.000,20.0021.00 µs
Averaged values change for
short, medium, and long cable
length settings, respectively
Pulse repetition time
Fixed: 4.000±0.002, 20.00±0.02,
80.00±0.02 µs
Averaged values change for
short, medium, and long cable
length settings, respectively
Sequential sampling rate
Fixed: 250.0±0.2, 50.00±0.04,
12.50±0.02 kHz
Averaged values change for
short, medium, and long cable
length settings, respectively
Vertical scale
0.5 mρ/div
Vertical accuracy
±3% full scale
Vertical position
Any trace point is movable to the center
of the screen.
Sampling efficiency, CT100B
50 to 90%
into 50 ohms
Sampling efficiency, CT100HF
45 to 90%
into 50 ohms
Noise
±5 mρ peak-to-peak
Input susceptibility
±1 A max
Distance cursor resolution
1/45 of one major division
Cursor readout range
≤ -0.3m (-1 ft.) to > 10000 m (33000 ft.)
Cursor readout resolution
0.0002 m (0.0007 ft.)
Distance measurement accuracy
< 1 cm (0.3 in.) or ±0.5% of
measurement plus uncertainty in Vp,
whichever is greater
CT100B TDR Cable Analyzer Operator's Manual
< ± 1% of measurement typ.
Into diode clamps
< ± 0.05% of measurement typ.
75
Appendix A
76
Specifications
Characteristic
Specification
Notes
Impedance readout range
<1 Ω to >1.5 kΩ
Impedance resolution
3 significant digits
Impedance accuracy
±10%, relative measurement ±2%
Horizontal scale
0.01 m/div (0.03 ft/div) to ≥ 61 m/div
(200 ft/div) (variable with pulse width)
Horizontal range
< 0 m to > 1000 m (3300+ ft)
Horizontal position
Any distance to full scale can be moved
on the screen.
Vp range
0.250000 to 1.000000
Vp default resolution
0.001
Vp fine resolution
0.000001
Vp accuracy (coarse)
±0.1%
Vp accuracy (fine)
±0.0001%
USB host port
USB 1.1
Front USB host connector is
powered (500 mA limit) with
500 VDC isolation from test port.
USB client port
USB 1.1
500 VDC isolation from test port.
Ethernet port
The instrument includes a 10/100mbps
Ethernet port for network
communication.
500 VDC isolation from test port.
DC power supply
24 VDC, 2.5A, positive tip. Use only the
MOHR-approved power supply.
500 VDC isolation from test port.
Battery pack
12 NiMH AA cells, fused at 2.5 A
Pack may wear out over time.
Battery operation time
> 6 hours. Power save options may
extend operating time.
18V full charge down to 12 V
battery low, 35% duty cycle.
Battery charge time
2.5 hours from fully discharged state
Overcharge protection
Charging discontinues once full charge
is attained.
Discharge protection
Instrument turns off prior to battery
damage
Charge capacity
2.7 Amp-hours (nominal-new)
< ± 1% typ.(0 to 1k ohms)
Software shutdown when battery
is low.
CT100B TDR Cable Analyzer Operator's Manual
Appendix A
A.2
Environmental Specifications
A.2.1
Temperature
Operating temperature
0°C to +50°C
Non-operating temperature
-20°C to +60°C
A.3
Mechanical Specifications
A.3.1
Weight
Without cover
2150 g (4.740 lb.)
With cover
2323 g (5.121 lb.)
A.3.2
Specifications
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
EC
The CT100B and CT100HF comply with all applicable EU directives.
A.4.2
FCC Compliance
CT100B and CT100HF emissions comply with FCC Code of Federal Regulations 47, Part 15, Subpart B,
Class A Limits.
CT100B TDR Cable Analyzer Operator's Manual
77
Appendix B
B.1
Operator Performance Checks
General Information
The CT100B Operator Performance Check is a series of procedures used to verify the calibration of a
CT100B unit. The following series of checks should be performed after a unit has been newly calibrated to
verify compliance to published specifications, but may also be performed to determine if it requires
recalibration.
The following series of steps are designed to allow a CT100B operator to completely verify the properties
of an individual CT100B unit to each published specification.
NOTE: If a CT100B fails any Operator Performance Check, it should be
serviced by a qualified repair facility.
B.2
Required Equipment
Item
MOHR part number
SMA 50 ohm Terminator
CT100-AC-ER50-S
Connector, SMA female to BNC male
CT100-AC-ISFBM (for CT100B [BNC])
Connector, SMA male to BNC female
CT100-AC-ISMBF (for CT100B [SMA])
Shorting cap
CT100-AC-IBS (for CT100B [BNC])
CT100-AC-ISS (for CT100B [SMA])
50 ohm 36 in. Reference Cable
CT100-AC-W536 (for CT100B [BNC])
CT100-AC-W536-S (for CT100B [SMA])
BNC Male to Male Adapter
CT100-AC-IBMM (for CT100B [BNC])
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.
B.3
Getting Ready
Disconnect any cables from the front BNC or SMA connector. Connect the instrument to the external 24V
power supply connected to a standard 3-prong AC source.
Allow the unit to warm up until it displays a steady temperature.
CT100B TDR Cable Analyzer Operator's Manual
79
Appendix B
Operator Performance Checks
B.4
Operator Performance Checks
B.4.1
Jitter, Noise, Rise Time, and Sampling Efficiency Checks
1) Connect a 50 ohm terminator to the CT100B front panel cable connector.
2) Select the MENU  Settings  Diagnostics menu item to enter the Diagnostics submenu.
3) Select Jitter. After a moment, a results window appears with a list of measurements.
The value for Jitter used in the specification for a CT100B is Jitter P2P. The value for Noise is the Noise
P2P.
The value for the 20-80% and 10-90% Reflected Rise Times are both displayed as 20-80 Rise and
10-90 Rise, respectively.
B.4.2
Output Impedance Check
1) Disconnect any cables from the CT100B front panel cable connector.
2) Position a cursor before the falling edge of the trace.
3) Position the second cursor well beyond the falling edge.
4) Attach the 50 ohm terminator to the CT100B.
5) The difference in ohms between the two cursors is a measure of the deviation of output impedance
from 50 ohms.
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. reference cable to the CT100B front panel cable connector. A trace should
appear on the device display.
4) Switch the CT100B into the short pulse setting from the Main menu.
5) Measure the pulse amplitude coming off the front panel cable connector. The averaged pulse
amplitude into 50 ohms should be between 290 mV and 310 mV.
6) Repeat pulse amplitude comparison for medium and long settings.
B.4.4
Pulse Width Check
1) Pulse width 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. reference cable to the CT100B front panel cable connector. A trace should
appear on the device display.
4) Switch the CT100B into the short pulse setting from the Main menu Cable Len setting.
5) Measure the pulse width coming off the front panel cable connector. The average pulse width
should be between 1.000-2.000 µsec for short, 5.000-6.000 µsec for medium, and 20.00-21.00
µsec for long.
6) Repeat pulse width check for medium and long settings.
80
CT100B TDR Cable Analyzer Operator's Manual
Appendix B
B.4.5
Operator Performance Checks
Pulse Repetition Period Check
1) Pulse repetition rate 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. reference cable to the CT100B front panel cable connector. A trace should
appear on the device display.
4) Switch the CT100B into the short pulse setting from the Main menu.
5) Measure the pulse repetition rate coming off the front panel cable connector. The average pulse
repetition rate should be 4.000±0.002 µsec for short, 20.00±0.02 µsec for medium, and
80.00±0.02 µsec for long.
6) Repeat pulse width check for medium and long settings.
B.4.6
Pulse Frequency Check
1) Pulse frequency 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. reference cable to the CT100B front panel cable connector. A trace should
appear on the device display.
4) Switch the CT100B into the short pulse setting from the Main menu.
5) Measure the pulse frequency coming off the front panel cable connector. Repeat pulse frequency
measurements for short, medium, and long pulse settings. 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.
B.4.8
Vertical Scale Check
Twist the VERTICAL SCALE knob clockwise. Vertical scale should drop to 0.5 millirho/div and the trace
should expand accordingly.
B.4.9
Vertical Accuracy Check (millirho)
1) Attach an open to the CT100B.
2) Position a cursor on the trace so that it is well after the open.
3) The vertical measurement should be between 940 millirho and 1060 millirho.
B.4.10 Vertical Position Check
1) Increase vertical scale to 500mρ/div by turning the VERTICAL SCALE knob counter-clockwise.
2) Use the VERTICAL POSITION knob to move the live trace completely above the horizontal midline
of the screen.
CT100B TDR Cable Analyzer Operator's Manual
81
Appendix B
Operator Performance Checks
3) Use the VERTICAL POSITION knob to move the live trace completely below the horizontal midline
of the screen.
A CT100B must succeed at both operations to pass the Vertical Position Check.
B.4.11 Distance Cursor Resolution Check
Distance cursor resolution is a value determined by a constant. It can be measured by counting distinct
locations that a cursor may occupy between two division lines, including one of the division lines.
B.4.12 Cursor Readout Range Check
In the Measurement menu, set the cable length to “Extra Long Mode”.
Turn the HORIZONTAL SCALE knob counter-clockwise until horizontal scale is maximized.
Using the M-FUNC button and M-FUNCTION knob, set Vp to 1.000.
With the HORIZONTAL SCALE knob, position a cursor at the most far right position possible.
The absolute distance measurement for the cursor is the upper limit for cursor readout range. This number
should be larger than 10,000 m or 33,000 ft.
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) Use the HORIZONTAL SCALE knob to set the horizontal scale to 0.00330 ft./div or 0.001 m/div.
2) Position a cursor on the screen and note the absolute distance measurement for the cursor.
3) Move the cursor the smallest possible step using the HORIZONTAL POSITION knob. The
difference between the new distance measurement and the previous is the minimum cursor readout
resolution.
B.4.14 Distance Measurement Accuracy Check
Accuracy is determined by taking a cable of known length and velocity and comparing the known values
against measured values. Accuracy is reported as a percentage. When determining accuracy, ensure that
horizontal calibration has been performed accurately.
Accuracy should be checked for short, medium, and long settings.
B.4.15 Ohm Readout Range Check
1) Connect the 36 in. reference cable to the CT100B.
2) Position a cursor on the trace well beyond the end of the cable. The vertical impedance
measurement should read ≥ 1.5k ohm.
3) Position a cursor on the trace well before the leading edge of the pulse. The vertical impedance
measurement should read ≤ 1 ohm.
82
CT100B TDR Cable Analyzer Operator's Manual
Appendix B
Operator Performance Checks
B.4.16 Resolution Check
Position a cursor at a point of the trace where the vertical impedance measurement is greater than 1 ohm
and less than 1500 ohms. The CT100B should display 3 digits for this measurement.
B.4.17 Vertical Accuracy Check (ohms)
1) Vertical accuracy is checked by comparing CT100B impedance measurements against a load of
known impedance. The supplied 50 ohm terminator is required.
2) Within the Display submenu, select the Ohms Rho button until Ohms is marked with asterisks. An
ohms at cursor reading now appears on the right side of the screen.
3) Connect a 50 ohm terminator onto the front panel cable connector.
4) Move a cursor out to a length greater than 300 ns. Impedance may change a small amount from
point to point.
5) Average impedance amongst a number of points along the trace determines vertical accuracy.
Impedance at cursor should be between 45 and 55 ohms.
6) Vertical accuracy should be checked for short, medium, and long maximum cable lengths.
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.
4) Turn the HORIZONTAL SCALE knob clockwise. Horizontal scale should decrease below 0.01 m/div
or 0.03 ft./div.
B.4.19 Horizontal Range Check
See the cursor readout range instructions above. Horizontal range and cursor readout range are always
equal.
B.4.20 Horizontal Position Check
This test is passed implicitly when the Cursor Readout Range and Horizontal Range checks are passed.
CT100B TDR Cable Analyzer Operator's Manual
83
Appendix C
C.1
Operator Troubleshooting
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 the rear panel battery-disconnect switch immediately and have the instrument serviced as soon as
possible.
CAUTION: DO NOT continue using the CT100B if it exhibits signs of
thermal overload, such as emitting heat or smoke, or if it smells of burning
plastic.
C.2
Power On Test
Verify that the back switch is in the ON position. Press the red front button to turn the instrument on. If the
instrument does not show anything on the screen within 20 seconds, turn the back switch to the OFF
position, unplug all USB and Ethernet devices, and attempt to turn it on again.
C.3
Functional Block Diagram and Troubleshooting Flowcharts
Use the following functional block diagram and troubleshooting flowcharts for various parts of the CT100B
to determine if your CT100B requires service. See the following section, Section C.4: Parts List, for a
replaceable parts list.
CT100B TDR Cable Analyzer Operator's Manual
85
Appendix C
C.3.1
Operator Troubleshooting
Functional Block Diagram
24V DC Charging
from AC adapter
CT100-AC-PS
Internal 12 Cell
NiMH Battery Pack
CT-100-AC-B2700
Client USB,
Ethernet
DC Power,
Temperature
DC Power
Back Panel Assembly
CT209B
Ethernet,
Client USB
Analog Power
W1W5C1
Ethernet W2W6C1,
Client USB W2W6C3,
Serial Port
+5V Digital
Video Cable
W2W7C1
Front Panel
Assembly
CT290B
Serial Port
W2W3C1
Digicomp
A2A1
Data Interface
W2W1C1
Analog Board
A1
USB Host
W2W3C2
86
User Input
Analog Signal
Host USB,
Buttons, Knobs
Test Port
W1W9C1
CT100B TDR Cable Analyzer Operator's Manual
Appendix C
C.3.2
Operator Troubleshooting
Main Diagnostic Sequence
Start of Diagnostics
External DC
Diagnostics
(C.3.2)
Status/Decision/Observation
Action
Procedure Callout
Does the device
power on?
YES
Perform
Startup
Diagnostics
(C.3.3)
Start and End of procedure
PASS
FAIL
FAIL
Perform Front
Control Panel
Verification
(C.3.4)
PASS
FAIL
Perform
Analog
Diagnostics
(C.3.5)
NO
Does a trace
appear on the
device?
PASS
FAIL
Perform TDR
Trace
Verification
Procedure
(C.3.6)
YES
PASS
NO
FAIL
Perform USB
Client and
Ethernet
Verification
(C.3.7)
PASS
FAIL
Perform Real
Time Clock
Verification
(C.3.8)
PASS
FAIL
Perform File IO
Verification
(C.3.9)
PASS
Return to MOHR for
factory Diagnosis and
Repair
Return to MOHR for
factory Diagnosis and
Repair
CT100B TDR Cable Analyzer Operator's Manual
Device is in working
order
87
Appendix C
C.3.3
Operator Troubleshooting
External DC Diagnostics
Start DC Power
Supply Diagnostics
Plug 24 volt DC
power supply into a
wall socket
Replace power
supply
(CT100-AC-PS)
Yes
Change to a working
AC wall outlet
Does the green light on the
power supply come on?
NO
NO
Does the AC
outlet work?
Verify the power
supply is firmly
plugged in to the AC
cord and outlet
YES
Finished DC Power
supply Diagnostics
88
YES
Does the light on the
power supply come on?
NO
Test outlet with
working device or
outlet tester
CT100B TDR Cable Analyzer Operator's Manual
Appendix C
C.3.4
Operator Troubleshooting
Startup Diagnostics
Start
Is the screen
blank/white and
unchanging for
>1 minute?
YES
NO
Did the MOHR
splash screen
appear
NO
YES
Did a progress
bar appear?
NO
YES
is the progress
bar frozen or
reporting an
error?
YES
NO
Is the device
locking up after
the progress bar is
finished?
YES
NO
PASSED
CT100B TDR Cable Analyzer Operator's Manual
FAILED
89
Appendix C
C.3.5
Operator Troubleshooting
Front Control Verification
Start Front Control
Diagnostics
Press OK and then
the Blue
Menu Button
Does the main
menu appear?
YES
Choose Settings ->
Diagnostics menu
item.
Choose “Front Panel
Check” menu item
NO
NO
Does
The front panel
diagnosics screen
appear?
YES
Turn each knob left
and right and press
each button except
the red one.
NO
Do all
of the button and
knob icons turn
grey?
YES
Press the red
power button.
NO
Did the
front panel
Diagnostics Screen
Disappear?
YES
FAILED
90
Finished Front
Control Diagnostics
CT100B TDR Cable Analyzer Operator's Manual
Appendix C
C.3.6
Operator Troubleshooting
Analog Diagnostics
Start Trace
Diagnostics
Did a message appear
on the device stating
that the license was out
of date or invalid?
YES
Install a valid license
file by following the
instructions in
section 3.2 of the
tech manual and
restart the device
NO
Did a message appear
stating that a critical
license file is missing
from the device?
YES
NO
Press the Autofit/
Help Button to bring
up the Autofit/Help
menu and select
Autofit
Did the trace
appear on the
screen?
NO
YES
PASSED
CT100B TDR Cable Analyzer Operator's Manual
FAILED
91
Appendix C
C.3.7
Operator Troubleshooting
TDR Trace Verification
Start TDR Pulse
Diagnostics
Return to Main Menu and navigate
to SettingsDiagnostics and select
Analog. Attach a shorted
terminator and press OK.
Did all tests
displayed pass?
YES
Using an oscilloscope,
verify the TDR pulse
characteristics as
described in “Operator
Performance Checks”
NO
NO
Are the pulse
characteristics within
the device’s
specifications?
YES
Enable temperature
display. This can be
found under the
Main Menu
SettingsDisplay
NO
Do temperatures update
on screen, and within ± 15ᵒ of
ambient
FAIL
Verify the
Vertical
Accuracy as
described in
“Operator
Performance
Checks”
YES
PASS
Attach a 50 ohm test
cable of known
length and set Vp to
match the pulse
velocity of the cable
FAIL
Measure the length
of the cable for
Short, Medium, and
Long Cable Length
Settings
Do distance
measurement meet
specification?
PASS
FAILED
92
TDR Trace
Verification Passed
CT100B TDR Cable Analyzer Operator's Manual
Appendix C
C.3.8
Operator Troubleshooting
USB Client and Ethernet Verification
START
Connect back USB to
known working PC
with CT-Viewer
installed.
Does the
PC recognize the
device?
NO
YES
Connect known
working Ethernet
cable, that is
connected to a
network, to device.
Watch Ethernet
lights on back.
Do Ethernet
Lights Blink?
NO
YES
FINISH
CT100B TDR Cable Analyzer Operator's Manual
FAILED
93
Appendix C
C.3.9
Operator Troubleshooting
Real Time Clock Verification
Start
Navigate to
Main Menu
Settings
Info
Time
Change the date
and time and select
OK
Turn power off,
then restart the
device
Does the
device display the
new time?
YES
NO
Reset Correct Date
and Time
PASSED
94
FAILED
CT100B TDR Cable Analyzer Operator's Manual
Appendix 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 if
the live trace with the two cursors and
generate a cursor scan. See section “Scan
a Cable” for instructions on creating a
scan.
While in the SCAN
menu select SAVE.
In the Save Trace
dialog, use the
keyboard to enter a
name for the trace.
Attach a USB
Keyboard to the
front of the device
NO
NO
Does the
keyboard work?
Does cable scan
records list a
collection of
saved traces?
Navigate to File
Cable Scan Records
YES
YES
After entering a
name for the
scanned trace, press
OK
Export the traces
using a USB drive or
CTViewer and then
delete the traces on
the device
Did the trace fail
to save due to
insufficient space?
Attempt to save the
scanned trace again.
NO
Did the trace
successfully
save?
YES
Hide the saved trace and
attempt to reload the
saved trace. See the
section “Load a Trace” for
instructions on loading a
saved trace.
NO
NO
Did the trace
load correctly?
YES
FAILED
CT100B TDR Cable Analyzer Operator's Manual
PASSED
95
Appendix C
C.4
Operator Troubleshooting
Parts List
Subassembly
Item
Part No
Qty
Description
1
2
CT100B
CT291
CT292
1
1
CT100B TDR Cable Tester
Rear Housing
Front Cover
1
2
CT 290B
W2W7C1
W1W9C1
1
1
LCD display, front control board, switches, cables, and knobs
Digicomp-video PCB FFC 40 pin flat-flex 0.5mm space
Coaxial Cable Assembly
1
2
3
4
5
6
7
CT208B
A1
A2A1
A2A3
A2A4
W2W1C1
W2W3C1
W2W3C2
1
1
1
1
1
1
1
Analog Digicomp Assembly
Analog Board Assembly
Digicomp Board
microSD Card
Clock Battery
Digicomp to Analog Board FFC
Serial Port Cable Assembly, Front
USB Host Cable
1
2
3
4
5
CT209B
CT100-AC-B2700
W1W5C1
W2W6C1
W2W6C2
W2W6C3
1
1
1
1
1
Power board, back bezel, battery, cables, and fan
Battery set NiMH with thermistors (2700 mA·h)
Analog Power Cable
Ethernet cable
Ethernet LED Cable
USB client cable
CT100B
Front Panel Assembly
Analog-Digicomp Assembly
Back Panel Assembly
96
CT100B TDR Cable Analyzer Operator's Manual
Appendix D
D.1
Maintenance and Service Instructions
Cleaning and Lubrication
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. The CT100B does not require
lubrication.
D.2
Cleaning and Lubrication Interval
Clean once per week, or as necessary.
D.3
Battery Removal / Replacement
1) Ensure that the CT100B power is off.
2) Remove all external devices and power connections from the instrument.
3) Apply the front cover (part CT292) and lay the instrument face down on a smooth surface.
4) Remove the two cross-top screws from the rear of the instrument.
5) Swing the handle to the back of the instrument.
6) Using a long handled cross-top screwdriver, remove the two pairs of screws from both ends of the
instrument nearest the handle mounts.
7) Carefully remove the rear housing (CT291) from the front panel (CT290B), using the handle for
gripping. The housing may be tight and the rubber feet may momentarily catch while they slide past the
metal frame.
8) The battery pack should now be exposed at the lower-rear of the instrument.
9) Unclip the 3-pin battery connector by pressing on the release tab and pulling on the connector housing.
10) Remove the two cross-top screws mounting the battery clips (part CT112) to the chassis.
11) Lift the battery pack out.
To re-install or replace the battery, repeat the above steps in reverse order.
D.4
Calibration and Calibration Interval
The recommended calibration interval is 1 year. See Appendix B for instructions on how to determine if
your instrument should be calibrated between scheduled calibrations. Detailed calibration procedure is
found in 0.
CT100B TDR Cable Analyzer Operator's Manual
97
Appendix D
D.5
Maintenance and Service Instructions
Install CT100B License
The CT100B license can be installed on the device using either CT Viewer or a USB Flash drive.
D.5.1
Install License Using CT Viewer
1. On a computer with CT Viewer installed, start up CT Viewer by double clicking on the icon.
2. Power on the CT100B and let it boot completely.
3. Connect the CT100B to the computer using either USB or Ethernet from the back of the device.
See section 4 for instructions on connecting to a CT100B over Ethernet.
4. In CT Viewer, click on Help  Install License.
5. Select the license file sent by Mohr.
6. Click OK.
7. After receiving a message of a successful install, restart the device.
D.5.2
Install a License Using a USB Flash Drive
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. Power on the CT100B device and let it boot completely.
3. Attach the USB Flash Drive to a front USB port on the CT100B.
4. Push the blue button (Main Menu Button) to bring up the main menu.
5. Using the soft menu buttons, navigate to Settings  Info  License  License from USB.
6. After receiving a message of a successful install, restart the device.
D.6
Clean Storage
The CT100B has a large storage capacity, but if more space is needed, perform the following steps to
clean the internal storage of the CT100B.
1. Delete saved traces following the instructions in Section 3.11.9.2. If desired, first archive the traces
by transferring them to CT Viewer.
2. After removing the scans, perform clean the database with Settings  Diagnostics  Database 
Clean Database, then restart the CT100B.
98
CT100B TDR Cable Analyzer Operator's Manual
Appendix E
E.1
Vp of Common Cables
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. The most accurate way to test a cable is
to determine the Vp of the cable using the CT100B and a known length of the cable you wish to test. See
Section 3.10.3 for more information on determining the Vp of a cable.
E.2
Dielectric Material
Type
Probable Vp
Jelly-filled
0.64
Polyethylene
0.66
PTFE / TFE
0.70
Pulp
0.72
Foam / cellular PE
0.78
Semisolid PE
0.84
Air
0.98
CT100B TDR Cable Analyzer Operator's Manual
99
Appendix E
E.3
100
Vp of Common Cables
RG Standards
Designation
Z0 (ohms)
Vp
RG-6/U
75
0.66
RG-6/UQ
75
0.66
RG-8/U
50
0.66
RG-9/U
51
0.66
RG-11/U
75
0.66
RG-58/U
50
0.66
RG-59/U
75
0.66
RG-62/U
92
0.84
RG-62A
93
0.84
RG-174/U
50
0.84
RG-178/U
50
0.69
RG-179/U
75
0.67
RG-213/U
50
0.66
RG-214
50
0.66
RG-218
50
0.66
RG-223
50
0.66
RG-316/U
50
0.66
RG-393
50
0.66
CT100B TDR Cable Analyzer Operator's Manual
Appendix E
E.4
MIL-C-17 Standards
Designation
Z0 (ohms)
Vp
M17/2-RG6 (RG-6/U)
75
0.66
M17/163-00001 (RG-8/U)
50
0.66
M17/6-RG11 (RG-11/U)
75
0.66
M17/155-00001 (RG-58/U)
50
0.66
M17/29-59 (RG-59/U)
75
0.66
M17/173-00001 (RG-174/U)
50
0.84
M17/169-00001 (RG-178/U)
50
0.69
M17/094-RG179 (RG-179/U)
75
0.67
M17/172-00001 (RG-316/U)
50
0.66
M17/127-RG393 (RG-393/U)
50
0.66
Designation
Z0(ohms)
Vp
H155
50
0.79
H500
50
0.82
LMR-200
50
0.83
HDF-200
50
0.83
CFD-200
50
0.83
LMR-400
50
0.85
HDF-400
50
0.85
CFD-400
50
0.85
LMR-600
50
0.87
LMR-900
50
0.87
LMR-1200
50
0.88
LMR-1700
50
0.89
E.5
Vp of Common Cables
Commercial Designations
CT100B TDR Cable Analyzer Operator's Manual
101
Appendix E
E.6
102
Vp of Common Cables
Twisted Pair
Designation
Z0 (ohms)
Vp
CAT5
100
0.71
CAT6
100
0.71
CT100B TDR Cable Analyzer Operator's Manual
CT100B TDR Cable Analyzer Operator's Manual
103
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.
Accuracy
The difference between a measured or estimated value of a quantity and its true value. Accuracy and
precision are both important factors to consider when assessing the reliability of a measurement.
Analog
Refers to a signal that is continuous with respect to both time and value. Analog circuitry produces and/or
measures analog signals. This is in contradistinction to digital signals, which are discontinuous in both time
and value. The sampling circuitry of a TDR converts the analog voltage signal detected on a cable to a
digital value for representation on the display and in the instrument's memory.
Cable
Conductors of electricity that are usually shielded and insulated. Cables typically contain at least two
conductors, one to deliver the electrical signal and one to act as the return path. The conductor acting as
the return path may be referred to as the “shield,” “ground,” or “ground wire”. A cable with such a ground
return path is known as an unbalanced cable, an example of which is typical coaxial cable. Another general
type of cable is called balanced cable, an example of which is twisted pair Ethernet cable. In balanced
cable, two signal wires carrying differential signals of opposite polarity are both separated from ground by
an equal impedance.
104
CT100B TDR Cable Analyzer Operator's Manual
Glossary
Cable Attenuation
A quantity describing the energy in a signal that is absorbed, reflected, or otherwise lost during propagation
through a cable. Higher frequencies are typically the most susceptible to attenuation. Cable attenuation can
distort some TDR measurements. Attenuation is often expressed in decibels (dB) at one or more
frequencies. See also dB and Return Loss.
Cable Fault
A defect in a cable or other condition that makes a cable less able to deliver electrical energy than was
designed. Damage to the shield, conductor, or insulation, bad splices, and poorly mated connectors are
frequently encountered cable faults.
Capacitance
See Reactance.
Characteristic Impedance
The ratio of the amplitude of voltage and current in an electrical signal propagating in a cable. In a coaxial
cable, this value (usually written Z0) is, in large part, related to the geometrical relationship of conductor to
return path conductor. Cables are usually designed to match the impedance of the source and load to
which they are attached in order to maximize power transfer.
Conductor
A substance that allows electricity to flow through it with minimal resistance. Most conductors are metals.
However, there are many non-metallic conductors, including salt solutions, graphite, and any element in its
plasma state.
dB
dB is the abbreviation for decibel. Decibels are a method of expressing power or voltage ratios as
logarithms. When used for voltage ratios, as in TDR, the formula for decibels is dB = 20∙log10(Vi/Vr) where
Vi is the voltage of the incident pulse and Vr is the voltage 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:
vertical scale = 20∙log10(100) = 40 dB.
DC
Direct current is unidirectional flow of electrical current. The term DC is also synonymous with constant; for
example, a perfect DC voltage source does not vary from a set value. Batteries are an example of a DC
voltage source.
DHCP
Dynamic Host Configuration Protocol. Used in computer networks to automatically assign network settings
to computers.
Dielectric
A nonconducting substance or insulator. May also refer to the dielectric strength or relative permittivity of a
medium, which is a measure of the electrical energy stored by a medium when an electrical potential of a
given frequency is applied across it. Also see Insulation.
CT100B TDR Cable Analyzer Operator's Manual
105
Glossary
Digital
Refers to signals in which information is represented by variables that are discrete or discontinuous both in
time and in value. This is in contradiction to an analog signal, which is continuous both in time and value.
Domain
A mathematical term that refers to the set of values for which a function is defined. A time-domain
instrument such as a TDR performs its function by recording measurements as a function of time.
DUT
Device Under Test. The DUT is the electrical cable, device, or network that is attached to the port of the
CT100B. It is the object to be measured.
FFT
The Fast Fourier Transform algorithm is a fast method of performing a discrete Fourier transform on a time
history. A Fourier transform converts time-domain data into the frequency domain. Since the CT100B
always uses the FFT algorithm, the term is used in this manual to describe both the algorithm and its
outputs. An “FFT Trace” is a frequency domain trace created by running the FFT algorithm on a TDR trace.
Impedance
The ratio of voltage to electrical current in a cable or circuit. Impedance is a frequency-dependent value
that is influenced both by resistive and reactive components. Impedance is expressed in terms of ohms but
should not be confused with resistance, which is a frequency independent quantity. Most cables have
impedances that vary little over the range of frequencies with which they are used. Impedance is described
by Z = R+j∙X where R is resistance, j is the imaginary unit, and X is the reactance at a given frequency. Also
see Reactance and Resistance.
Impedance Mismatch
A point in a cable or device under test in which the characteristic impedance changes, causing a partial
reflection of the energy in a test signal. See Reflection Coefficient.
Incident Pulse
The excitation pulse produced by a TDR and injected into the cable under test. The trace produced by the
TDR is the temporally-resolved reflections produced by the cable in response to the incident pulse. The
incident pulse in the CT100B is a step rise signal with a finite rise time. See Rise time.
Inductance
See Reactance.
Insulation
A coating on an electrical conductor that inhibits the flow of electricity. Insulation serves as both a means of
providing electrical safety and ensuring signal integrity.
IP
Internet Protocol. The universal protocol used to send data through the internet. Also used in many other
computer networks. Each computer on a network must have a unique IP address.
106
CT100B TDR Cable Analyzer Operator's Manual
Glossary
Jitter
The uncertainty in measurement of time in a TDR. The main effect of jitter is to cause apparent vertical
noise in areas of changing impedance. Areas of constant impedance, such as a flat segment of 50 Ω cable,
will show no abnormality.
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.
LCD
Liquid crystal display. The display used by this instrument is an active-matrix thin-film transistor LCD,
abbreviated TFT-LCD.
Millirho
See Reflection Coefficient.
Noise
Any undesirable electrical energy that impairs the ability of an electronic system to transmit or receive a
signal or make an accurate measurement. In TDR, noise is typically related to thermal and/or electrical
noise that interferes with the time base or sampling circuitry and is usually random, although a nearby
strong electromagnetic radiator can cause non-random synchronous noise to be measured on unshielded
cable. In the case of random noise, averaging is an effective means of noise suppression.
Open Circuit
Describes a non-terminated cable or cable with a broken conductor that reflects all energy within the
incident pulse.
OSL (Open Short Load)
A method of calibrating one port analyzers using precision open, short and load terminations, where the
load matches the output impedance of the analyzer. Each termination contributes to reducing error in an
S11 measurement.
Phase
A horizontal shift in a sinusoid. Phase is given as an angle. A sinusoid with phase of π radians (180
degrees) is precisely inverted compared to the same sinusoid with 0 phase. A sinusoid with phase of 2π
radians (360 degrees) is precisely equal to an the same sinusoid with 0 phase, i.e. it has no phase shift.
Precision
The variation in the value of a variable measured multiple times. Precision and accuracy are both important
factors in determining the reliability of a given measurement. Precision may also be used to describe the
number of digits or the unit of the least significant digit with which a particular quantity is expressed.
CT100B TDR Cable Analyzer Operator's Manual
107
Glossary
Reactance
The imaginary component of electrical impedance. Reactance describes the opposition of a conductor to
the flow of alternating current. Impedance is described by Z = R+j∙X where R is resistance, j is the
imaginary unit, and X is the reactance at a given frequency. If X>0, the impedance is inductive, if X =0 then
the impedance is purely resistive, and if X <0 the impedance is capacitive.
Reflection Coefficient
In TDR, a coefficient describing the amplitude of a reflected signal produced by an impedance mismatch in
 −
relation to the incident pulse. The reflection coefficient Gamma (Γ) is defined by the relation  =  +0

0
where Zt is the impedance at time t and Z0 is the characteristic impedance of the cable, and is usually
described in parts per thousand with units of rho (ρ) or millirho (mρ). The coefficient ρ ranges from -1 (short
circuit) to +1 (open circuit). A reflection coefficient of zero indicates that there is no impedance mismatch
and no reflection of electrical energy.
Reflectometer
An instrument that measures reflections to determine the state of a system. The CT100B measures the
reflections of electrical energy.
Resistance
A conductor's opposition to electrical current. The reciprocal of resistance is conductance. Electrical
resistance can often be considered a constant that does not vary with respect to the voltage or current
applied to an object. When considering the impedance of a circuit element, resistance is also frequency
invariant. Most materials, including conductors, have some degree of electrical resistance. A special class
of materials called superconductors demonstrate zero electrical resistance.
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.
Return Loss
A measure of the power reflected by impedance changes in a cable. Return loss is typically expressed as a
logarithm of the reflection coefficient, ρ: RL(dB) = -20∙log10|ρ| where RL is return loss. Cable faults such as
shorts and opens, which return all of the incident energy in the TDR signal, have return losses of 0 dB.
Rho (ρ)
See Reflection Coefficient.
Rise time
With respect to the incident pulse, the time required for the signal to change from 10% to 90%, or
alternatively 20% to 80%, of its final value. With respect to the sampling electronics, the time required for
the sampled value to change from 10% to 90% of the final value when a perfect step signal is applied. The
rise time of a pulser-sampler system is approximately equal to the root sum of squares of the pulse and
sampler rise times.
108
CT100B TDR Cable Analyzer Operator's Manual
Glossary
RMS
An acronym for Root Mean Square, also abbreviated rms and known as the quadratic mean. This is a
useful statistical technique when considering time varying electrical quantities for which simple DC
definitions are not accurate, such as when determining the power dissipated by an AC source. The formula
for calculating an rms value of a given time-varying signal is:
12 + 22 + 32 + ⋯ + 2
 = √

where xi represent discrete samples and n is the total number of samples.
S11
A scattering parameter that measures complex return loss on port 1 of a linear electronic device. See
Scattering Parameters.
S21
A scattering parameter that measures complex transmission loss from port 1 to port 2 on a linear electronic
device. See Scattering Parameters.
Sampling Efficiency
The CT100B makes measurements through a process known as sequential sampling. In sequential
sampling, a succession of incident pulses followed by discrete samples progressively builds up a given
TDR trace. Sampling efficiency describes the ability of the sampling circuitry to adjust to rapid changes in
impedance within a TDR trace. Low sampling efficiency leads to a trace that appears too smooth.
Scan
A scanned or saved trace. See Trace.
Scattering Parameters
Scattering parameters are the complex ratios of output signal to input signal for a linear electronic device.
For a device with two ports, four scattering parameters may be generated: S11, S21, S12 and S22. A one port
device has only one parameter, S11, while a four port device has 16. S11 is the complex ratio of output at
port 1 to an input at port 1. S21 is the complex ratio of an output on port 2 to an input on port 1, and so on.
The assignment of port 1 and port 2 is arbitrary. A full set of scattering parameters are considered a
complete characterization of a linear device for the frequency range of the scattering parameters.
Short Circuit
The condition in which the conductor in a cable or circuit comes into direct contact with the return path
conductor or earth ground. The electrical length of the cable measured by TDR is shortened to the point of
the short circuit.
Smith Chart
A method for displaying complex valued electrical measurements, such as an S11, on a polar plot,
graphically showing both magnitude and phase angle.
CT100B TDR Cable Analyzer Operator's Manual
109
Glossary
Smoothing
Any technique for reducing noise in a signal. The CT100B uses time averaging to smooth traces.
SP232
A serial protocol used by the Tektronix 1502B and 1502C. This protocol allowed transmission of TDR trace
data across a serial port. Using a USB to serial port adapter, a 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. TDR instruments use a form of closed-circuit
radar to detect cable faults. A series of pulses are sent into a cable and reflected voltage is measured as a
function of time. If the velocity of propagation (Vp) is known, the length of a cable and the distance to cable
faults can be determined. TDR traces produced by step-rise TDRs like the CT100B describe the
impedance of a cable along its length and can accurately detect a wide range of cable faults that can
impair high-frequency analog/RF and digital communications systems.
Trace
A displayed or stored signal. When displayed, a trace appears as a line across the screen. A trace may be
a direct TDR measurement, as with the live trace, or derived trace, such as a difference trace or an S11
trace. A trace is sometimes referred to as a “waveform”. A scanned or saved trace may be called a “scan”.
A trace is a visual representation of the waveform generated by a TDR. Traces on the CT100B may be in
either time or frequency domain depending upon their purpose.
Trace Averaging
See Noise.
USB
Universal Serial Bus. A common system for connecting a peripheral, such as a printer, phone, or CT100B
to a computer.
Velocity of Propagation (Vp)
Velocity of propagation of an electrical signal within a cable as a fraction of c, the speed of light in a
vacuum. Coaxial cable usually has a Vp of between 0.6 and 0.9.
Vertical Reference (Vert Ref)
A feature of the CT100B that improves vertical measurements by referencing them to scans from short and
open calibration terminations.
110
CT100B TDR Cable Analyzer Operator's Manual
Index
adapter plugs
voltage ...........................................................9
Add Server........................................................ 58
balun, using ........................ See Vert. Ref feature
battery
battery packs ..................................................1
Charge Capacity .......................................... 76
charging circuit ...............................................9
charging test .......................................... 85, 96
Charging Time.............................................. 76
disposal ..........................................................7
low battery.................................................... 10
Operation time.............................................. 76
proper care of the battery ...............................9
Removal/Replacement ................................. 97
temperature restrictions................................ 10
trickle charge ..................................................9
breaker
manual ...........................................................4
thermal ...........................................................4
button
AUTOFIT/HELP ........................................... 12
CURSOR ............................................... 12, 18
FILE ....................................................... 12, 19
H1 ................................................................ 11
H2 ................................................................ 11
H3 ................................................................ 11
H4 ................................................................ 11
MENU .................................................... 11, 19
M-FUNC ................................................. 12, 15
POWER ....................................................... 11
SCAN ............................................... 12, 16, 36
SELECT ................................................. 12, 18
V1 ................................................................ 12
V2 ................................................................ 12
V3 ................................................................ 12
V4 ................................................................ 12
cable fault
common types .............................................. 62
distance to fault ............................................ 31
short faults ................................................... 62
Cable Loss (S21) .............................................. 70
cable resistance correction ............................... 43
CT100B TDR Cable Analyzer Operator's Manual
cable scans ...................................................... 34
cable type ......................................................... 54
Calibration ........................................................ 97
Interval ......................................................... 97
CAT5 .............................................................. 102
CAT6 .............................................................. 102
change units ..................................................... 55
charging the battery.......................................... 10
cleaning ............................................................ 97
commercial cable ........................................... 101
compound cables ............................................. 33
configurations ................................................... 56
load.............................................................. 56
save ............................................................. 56
connectors
24 VDC power adapter plug ......................... 13
BNC connector ............................................ 12
client USB .................................................... 13
Ethernet ....................................................... 13
rear panel .................................................... 13
RJ-45 Ethernet port ..................................... 13
USB port ...................................................... 12
controls
front panel.................................................... 11
keyboard ...................................................... 13
soft keyboard ............................................... 14
usb keyboard ............................................... 13
covers ................................................................ 6
CT Viewer ............................................ 20, 38, 57
Connecting over Ethernet ............................ 58
movie ........................................................... 59
Remote Control...................................... 54, 59
damage
due to static charge ....................................... 4
during shipping .............................................. 1
improper grounding ........................................ 4
dielectric ........................................................... 99
difference trace ................................................ 41
display
features........................................................ 15
distance to fault ................................................ 31
theory .......................................................... 65
dynamic deconvolution
111
Index
create trace .................................................. 53
theory........................................................... 72
electric shock ...................................................... 6
electrostatic discharge
damage resulting from ................................... 9
Envelope Plot ................ See trace: Envelope Plot
Environmental Specifications ............................ 77
explosive atmosphere ......................................... 6
Fast Fourier Transform (FFT) ........................... 54
FFT........................... See Fast Fourier Transform
fine Vp control .................................................. 55
first derivative ................................................... 42
floating................................................................ 5
floating ground.................................................... 5
functional block diagram ............................. 85, 96
fuses................................................................... 4
grounding
grounding the BNC connector ........................ 5
Help Menu ........................................................ 18
Impedance................................................ 65, 106
at cursor ....................................................... 34
Resistive loss correction .............................. 43
Testing ......................................................... 80
Toggle On/Off .............................................. 25
impedance change ........................................... 61
impedance matching adapters .........See Vert. Ref
feature
Insertion Loss
frequency domain (S21) ................................ 70
inspection ........................................................... 1
Intermittent Fault Detection ............................... 39
jitter .................................................................. 75
Menu Option ................................................ 25
Specification ................................................ 75
Test and verification ..................................... 80
Theory ....................................................... 107
keyboard .......................................................... 13
Keyboard .......................................................... 14
keyboard shortcuts ........................................... 13
knob
HORIZONTAL POSITION ............................ 12
HORIZONTAL SCALE ................................. 12
M-FUNC....................................................... 12
VERTICAL POSITION ................................. 11
VERTICAL SCALE ....................................... 12
layer peeling
create trace .................................................. 53
theory........................................................... 72
license code ..................................................... 10
Installing a license using usb or CT Viewer .. 98
loading a trace .................................................. 37
loss of ground ..................................................... 6
112
low battery........................................................ 10
M17/163-00001 (RG-8/U)............................... 101
M17/29-59 (RG-59/U) .................................... 101
M17/2-RG6 (RG-6/U) ..................................... 101
M17/6-RG11 (RG-11/U) ................................. 101
manual breaker .................................................. 4
mechanical shock............................................... 9
menu
AUTOFIT/HELP ........................................... 18
FILE............................................................. 19
Info .............................................................. 10
Power .......................................................... 10
Scan ............................................................ 16
top-level menu ............................................. 19
MIL-C-17 ........................................................ 101
multisegment cable .......................................... 33
navigating dialog boxes .................................... 14
Network Settings .............................................. 58
Noise.............................................................. 107
Specification ................................................ 75
Testing ........................................................ 80
normalized TDR trace ...................................... 52
Theory ......................................................... 71
Ohms-at-cursor ................................................ 34
Operator Performance Checks ......................... 79
options and accessories ................................... 73
panels ................................................................ 6
Performance Check ................................... 25, 79
phase stable cable ........................................... 49
POWER button ........................ See button:Power
Power menu .............................. See menu:Power
power requirements
AC power....................................................... 1
external AC power adapter ............................ 1
internal battery ............................................... 1
reflected rise time ............................................. 75
Reflection Coefficients ............................. 61, 108
theory .......................................................... 61
Toggle On/Off .............................................. 25
relative distance ............................................... 32
relative reflection coefficient ............................. 56
Remote Control .....................................54, 58, 59
repacking ........................................................... 2
resistive loss correction .................................... 43
resolution .......................... See sample resolution
Return Loss
frequency domain (S11) ................................ 70
lumped parameter ....................................... 66
Return Loss (S11)Options ................................. 46
Aberration Filter ........................................... 46
Align Base Traces ....................................... 49
Between Cursors ......................................... 47
CT100B TDR Cable Analyzer Operator's Manual
Index
Calibration Standards ................................... 49
Hide calibration traces .................................. 49
Noise Filter ................................................... 46
Phase Correction ......................................... 46
Return Loss waveforms (S11) ............................ 45
RG standards ................................................. 100
RG-11/U ......................................................... 100
RG-58/U ......................................................... 100
RG-59/U ......................................................... 100
RG-6/U ........................................................... 100
RG-8/U ........................................................... 100
Rise Time ................................................... 52, 67
Specifications ............................................... 75
Testing ......................................................... 80
Theory .......................................................... 67
safety ..................................................................3
terms and symbols
CAUTION ..................................................3
DANGER ...................................................3
symbols in the manual ...............................3
symbols on the product ..............................4
WARNING .................................................3
sample resolution.............................................. 30
Sampling Efficiency ........................................ 109
Specification ................................................. 75
Testing ......................................................... 80
scans ................................................................ 34
Scattering Parameters ...................................... 69
second derivative .............................................. 42
secondary reflections ........................................ 49
selecting a trace................................................ 35
set up................................................................ 14
date and time ............................................... 14
short faults ........................................................ 62
Smith Chart
create Smith Chart ....................................... 50
theory ........................................................... 71
Soft Keyboard ................................ See Keyboard
Spatial Resolution ......................... See Rise Time
specifications .................................................... 75
static charge
damage to BNC connector ........................... 12
grounding the BNC connector ........................5
storing a trace ................................................... 36
switches
power ........................................................... 13
TDR .............................................................. 1, 61
temperature correction ...................................... 31
thermal breakers .................................................4
CT100B TDR Cable Analyzer Operator's Manual
thermal overload............................................... 85
Time-Domain Reflectometry ......................... 1, 61
trace
create a cable scans .............................. 34–35
delete ........................................................... 39
difference ..................................................... 41
distance to fault (DTF) ................................. 31
Envelope Plot .............................................. 39
FFT .............................................................. 54
first derivative............................................... 42
Hide selected trace ...................................... 16
Layer Peeling ............................................... 53
loading ......................................................... 37
multisegment velocity of propagation ........... 33
normalized TDR trace .................................. 52
S11 return loss between cursors ............. 47, 49
scan mode ................................................... 34
selection ...................................................... 35
smoothing .................................................... 29
storing .......................................................... 36
transfer .................................................. 38, 57
trace scans ....................................................... 34
Troubleshooting................................................ 85
troubleshooting flowchart.................................. 85
units ................................................................. 55
unpacking ........................................................... 1
USB
Send Traces ................................................ 57
USB drive
save waveform............................................. 57
velocity of propagation
AUTOFIT/HELP button ................................ 28
changing the value of ................................... 27
Common Cables .......................................... 99
finding an unknown ...................................... 27
Load a Cable Type's Vp ............................... 55
Load and Save Custom Cable Types........... 55
multisegment cable ...................................... 33
theory .......................................................... 64
Vert. Ref. calibration ......................................... 43
vertical reference .............................................. 43
vibration ............................................................. 9
Voltage Standing Wave Ratio (VSWR) ............. 67
Create VSWR trace ..................................... 16
Toggle VSWR at cursor ............................... 26
Vp ............................. See velocity of propagation
water hazards ..................................................... 9
water spray......................................................... 9
watertight............................................................ 9
113
Download PDF

advertising