Appendix D: Calibration Procedures
“rollover.” When the capacitive calibration is correct, the timing of the trace is synchronized
across the pulse so that the trace before 50ns lines up with the trace after 50ns.
5) Magnify the 50 nanosecond rollover by adjusting vertical and horizontal scale while keeping
the live trace on-screen using the VERTICAL and HORIZONTAL SCALE and POSITION
knobs. Scale values of 0.1 ft/div (0.03m/div) and 5 mρ/div are acceptable, but a break at a
larger scale may be visible.
At this point, the CT100 should display the live trace diagonally across the screen.
If calibration needs additional manual adjustment the live trace will appear to show a break at
the 50ns point. Figure 26 displays the appropriate scale. The 50ns rollover is surrounded by a
red circle. However, in Figure 26, the capacitive calibration needs to be adjusted. Figure 27
displays a trace that does not need manual capacitive calibration.
If adjustment is necessary, adjust the Sampler Comp value until the live trace shows no breaks
as per Figure 27. If the trace appears linear across the 50ns rollover, steps 6 through 9 may
be skipped.
6) Enter the Calibration submenu
7) Enter the Manual Calibration submenu
8) Select Timebase DAC by pressing Button 21.
Mohr CT100 / CT100HF Operator's Manual 83
Figure 26: Example of an incomplete capacitive calibration. The
circled area is the 50ns point. The separation between traces is
indicative of a CT100 that needs Sampler Comp adjustment.
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