Tektronix 475A - Phase Difference Measurements

divisions. Substituting these values in the horizontal
conversion factor formula:
Horizontal
l 2.19 ms
Conve rsion = PRO SE ASSNN pA DAMM dr zm 1.37
8 X 60.2 ms
Factor
Then with a TIME/DIV switch setting of 50 us, the time
duration of an unknown signal that completes one cycle in
seven horizontal divisions, can be determined by using the
time duration formula:
This answer can be converted to frequency by taking
the reciprocal of the time duration (see applications on
Determining Frequency).
PHASE DIFFERENCE
MEASUREMENTS
Use either the CHOP or ALT mode. Setthe A TRIGGER
SOURCE switch to CH 1. The reference signal should
precede the comparison signal in time. Use coaxial cables
or probes that have equal time delay to connect the signals
to the input connectors.
If the signals are of opposite polarity. set the INVERT
pushbutton to invert the Channel 2 display (signals may be
of opposite polarity due to 180° phase difference; if so,
take this into account in the final calculation}. Set the CH 1
and CH 2 VOLTS/DIV switches and the CH 1 and CH 2
VAR controls so the displays are equal in amplitude.
Set the TIME/DIV switch for about a one-cycle
waveform. Position the display and turn the A VAR
TIME/DIV control for 1 reference signal cycle in exactly
eight divisions (see Fig. 21). Each division of the graticule
represents 45° of the cycle (360° + 8 divisions =
45" /division). The sweep rate can be stated in terms of
degrees as 45°/division.
Measure the horizontal difference between correspon-
ding points on the waveforms and multiply the distance
measured (in divisions) by 45°/division (sweep rate) to
obtain the amount of phase difference.
EXAMPLE: The horizontal difference is 0.6 division
with a sweep rate of 45°/division as shown in Fig. 21.
42
475A/DM44
Operators
@