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The phase measurement is always the phase ofthe selected channel,
using another channel as a reference. Pressing the INPUT A button
will measure the phase ofinput channel A, using input channel B as a
reference. Pressing the INPUT B button will measure the phase of
input channel B, using input channel A as the reference.
Pressing GEN after selecting the channel for measurement will provide
the following measurements:
.
A-G or B-G – This option will measure the phase ofthe selected
input with the same channel gen-mon path as a reference. This
is used to measure phase shift through a device (input to
output).
.
GA or GB – This option will measure the phase ofthe selected
gen-mon channel with the other gen-mon channel as the
reference.
The lower left soft key controls the range over which the phase
measurement is displayed. The allowable ranges are +180 to –180
degrees, -270 to +90 degrees, and –90 to +270 degrees. The latter
two ranges should generally be used for polarity checks, where the
reading will either be very close to 0 or very close to 180 degrees. If
the +180 to -180 degree range is used for these measurements,
readings near zero could read on either end ofthe range.
The lower right soft key controls the averaging of the readings. If it is
set to ‘NOAVERAGE’, the phase readings are updated at a rate of
approximately three per second. Ifit is set to ‘AVERAGE’, the display
shows a running average ofthe last eight readings, to reduce the
effects of digit bobble. The ‘AVERAGE’ mode is particularly useful
when adjusting azimuth in analog tape machines.
In bargraph mode, the AMPLITUDE keys are used to set the endpoints
ofthe graph. After selecting the endpoint to change by pressing the
appropriate soft key, the
±
10 dB keys will change the endpoint in
increments of90 degrees. The INC and DEC buttons will change the
endpoint in increments of10 degrees.
To obtain the specified accuracy, analog inputs must have amplitude
greater than about 20 mV and must have signal-to-noise ratio greater
than about 40 dB. Ifeither input drops below about 8 mV (or below
4
Oper
ati
o
n
Controlling the Analyzer : Phase
Operation
Portable One Plus Access User's Manual
4-41
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