Tektronix 422, Instruction Manual

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Operating I nstructions—Type 422 AC-DC
Channel 1
(reference) Channel 2
Fig. 2-19. Measuring phase difference. Fig. 2-20. High resolution phase-difference measurement with
increased sweep rate.
o f the graticule (see Fig. 2-19). Each division of the
graticule represents 45° o f the cycle (360° ^ 8 divisions =
45°/division). The sweep rate can be stated in terms of
degrees as 45°/division. 45°/division -M O = 4.5°/division. Fig. 2-20 shows the same
signals as used in Fig. 2-19 but w ith the X10 MAG switch
pulled out. With a horizontal difference of six divisions, the
phase difference is:
11. Measure the horizontal difference between corres­
ponding points on the waveforms.
12. M ultiply the measured distance (in divisions) by
45°/division (sweep rate) to obtain the exact amount of
phase difference.
EXAMPLE. Assume a horizontal difference o f 0.6 divi­
sions w ith a sweep rate of 45°/division as shown in Fig.
2-19.
horizontal ... ,
nu r^-cx w magnified sweep rate
Phase Difference = difference X , . . ,
(division) (degrees/div)
Substituting the given values:
Phase Difference = 6 X 4.5°.
The phase difference is 27°.
Using the formula:
Phase Difference
horizontal
difference
(divisions)
sweep rate
A (degrees/div)
Substituting the given values:
Phase Difference = 0.6 X 45°
Common-Mode Rejection
The ALG ADD feature o f the Type 422 can be used to
display signals which contain undesirable components.
These undesirable components can be eliminated through
common-mode rejection. The precautions given under Alge­
braic A ddition should be observed.
1. Connect the signal containing both the desired and
undesired information to the INPUT 1 connector.
The phase difference is 27°.
High Resolution Phase Measurements
More accurate dual-trace phase measurements can be
made by increasing the sweep rate (without changing the
V A R IA B LE T IM E /D IV control setting). One of the easiest
ways to increase the sweep rate is w ith the X I 0 MAG
switch. The magnified sweep rate is determined by dividing
the sweep rate obtained previously by the amount o f sweep
magnification.
EXAMPLE. If the sweep rate were increased 10 times
with the magnifier, the magnified sweep rate would be
2. Connect a signal similar to the unwanted portion o f
the Channel 1 signal to the INPUT 2 connector. For exam­
ple, in Fig. 2-21 a line-frequency signal is connected to
Channel 2 to cancel out the line-frequency component of
the Channel 1 signal.
3. Set both Input Coupling switches to DC (AC if DC
component on input signal is too large).
4. Set the vertical Mode switch to A L T . Set the
VO LTS/DIV switches so the signals are about equal in
amplitude.
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