Operating Instructions
S-Param
Creates a new trace that is the negative complex division of the currently selected trace
by the base trace. This function only applies to Fast Fourier Transform traces and can
be used to calculate the S11 parameter.
Phase
Creates a new trace that shows the phase angle of the currently selected trace. This
operation only applies to Fast Fourier Transform traces and S-Param traces.
Layer Peeling
Layer Peeling reduces multiple reflections in live or saved traces. These are reflections
of the step pulse off of more than one impedance change. A trace when layer peeled is
automatically set as a ZTrace.
The Layer Peeling system is highly dependent on where it starts. The user sets the start
of layer peeling with the active cursor. Good results are only obtained when the start of
layer peeling is set at 50 ohms.
Test preparations
Test preparations
Velocity of propagation
Velocity of propagation (Vp), also sometimes abbreviated VoP or VP, is the measure of the
velocity of an electrical signal within a cable expressed as a fraction of c, the speed of light in a
vacuum. With the CT100, Vp can be set in ranges between 0.25 and 1.0. See Appendix F for
cable types and their estimated Vp.
Change Vp
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 Fine Vp is enabled from the
Measurement menu, two “Vp” indicators will be separately available. Coarse Vp allows for the
modification of the first 3 significant digits and Fine Vp allows for the modification of the last 3
significant digits.
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.
An accurate Vp is necessary for accurate cable length and distance-to-fault measurements.
For cables of a known type, the Vp can be approximated by using the nominal Vp for that
cable type.
The CT100 has a built-in library of cable types and their Vp values. See Cable library section
below.
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 Find an unknown Vp section.
32 Mohr CT100 / CT100HF Operator's Manual
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