Appendix D: Calibration Procedures
7) The next step is to adjust
Hybrid Comp
to minimize the vertical shift that occurs when
changing between open and short conditions. The value of
Hybrid Comp
can be adjusted
by turning the
M-FUNCTION
knob on the front panel. For CT100 units with the self-
grounding BNC test port, a male–male BNC adapter is used to provide an open condition.
For CT100HF units with an SMA test port, leave the test port empty.
Figure 29 shows an open condition at the test port. The apparent reflection coefficient of
the trace has changed from 31 mρ to -53.6 mρ, indicating that an adjustment of Hybrid
Comp is required.
Mohr CT100 / CT100HF Operator's Manual
85
Figure 28: Typical trace from a CT100 with a shorting terminator
applied to the test port. The active cursor is set at the reflected rise.
The right hand side of the trace shows the effect of the shorting
terminator.
Figure 29: Hybrid Comp adjustment with open BNC and cursor at
the reflected rise. Note for most applications the horizontal gain
should be at 0.004 ft/div and the vertical scale should be set at 2
mρ/div. The male–male BNC adapter can be used to provide an
“open” condition.
