5. Math Functions
The CT100B includes various math functions that can help highlight cable issues, measure
impedance change, or otherwise help with cable analysis. The following sections explain how to
perform those functions.
5.1. 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 2. 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 blue trace is created that displays the
difference between the base trace and the selected trace. See Figure 5.1, which shows
3.43 ohm excess impedance due to a slightly loosened BNC 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 Analyzers Operator’s Manual 77
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