4. Operating Instructions
Figure 4.15. After choosing Set New Position, the cursor position is now at 0.000 m.
This setting only affects the on-screen display and measurements of the trace. This will not change
a saved trace, and the zero offset cannot be saved.
To clear the zero offset, go to MENU → Settings → Display → Set/Clear Zero Offset and press
Clear Setting. The zero point will go back to its normal position.
4.7.3. 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 improve cable
measurement accuracy in the setting of compound, multi-segment cables with differing Vp values.
The CT100B allows the operator to break a TDR trace into cable segments, each of which can
have its own Vp. 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 the MENU → Measurement menu.
2. Select the Cable Segments submenu.
3. Place the cursor at the start 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 choose each cable segment and use the
M-FUNC Vp option to set the given segment’s velocity of propagation.
CT100B TDR Cable Analyzers Operator’s Manual 51
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