Tektronix 422, Instruction Manual

Page: 36 / 213

Operating Instructions—Type 422 AC-DC
Channel 1 (reference) Channel 2
5 0 %
Amplitude
level
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loscope trigger the signal source This can be done by con­
necting the signal at the GATE OUT connector to the input
o f the signal source. Set the LEVEL control fu lly clock­
wise, TRIGGERING Mode switch to AUTO and adjust the
T IM E /D IV switch fo r the desired display. Since the signal
source is triggered by a signal that has a fixed tim e relation­
ship to the sweep, the output o f the signal source can be
displayed on the CRT as though the Type 422 were trig ­
gered in the normal manner.
Multi-Trace Phase Difference Measurements
Phase comparison between tw o signals of the same fre­
quency can be made using the dual-trace feature o f the
Type 422. This method of phase difference measurement
can be used up to the frequency lim it o f the vertical sys­
tem. To make the comparison, use the follow ing procedure.
Fig. 2-18. Measuring time difference between two pulses.
measurement is being made) in relation to the center hori­
zontal line.
10. Adjust the horizontal POSITION control so the
Channel 1 (reference) waveform crosses the center hori­
zontal line at a vertical graticule line.
1. Set the Input Coupling switches to the same position,
depending on the type o f coupling desired.
2. Set the vertical Mode switch to either CHOPPED or
A LT . In general, CHOPPED is more suitable fo r low-
frequency signals and the A L T position is more suitable fo r
high-frequency signals. More inform ation on determining
the mode is given under Dual-Trace Operation in this sec­
tion.
11. Measure the horizontal distance between the
Channel 1 waveform and the Channel 2 waveform (see Fig.
2-18).
12. M ultiply the measured distance by the setting of the
T IM E /D IV switch. If sweep magnification is used, divide
this answer by 10.
EXAMPLE. Assume that the T IM E /D IV switch is set to
50 jus, the magnifier is on and the horizontal distance
between waveforms is 4.5 divisions (see Fig. 2-18).
Using the formula:
Time Delay
T IM E /D IV
setting
horizontal
distance
(divisions)
magnification
3. Set the TRIGGERING Coupling switch to CH 1.
4. Connect the reference signal to the INPUT 1 connec­
to r and the comparison signal to the INPUT 2 connector.
The reference signal should precede the comparison signal
in time. Use coaxial cables or probes which have similar
tim e delay characteristics to connect the signals to the IN­
PUT connectors.
5. If the signals are of opposite polarity, pull the IN­
VERT switch out to invert the Channel 2 display. (Signals
may be o f opposite polarity due to 180° phase difference;
if so, take this into account in the final calculation.)
6. Set the VO LTS/D IV switches and the V A R IA B LE
V O LTS/D IV controls so the displays are equal and about
five divisions in amplitude.
Substituting the given values:
Time Delay
50 ms X 4.5
10
The time delay is 22.5 microseconds.
Normal Trigger Generator
O rdinarily, the signal to be displayed also provides the
trigger signal fo r the oscilloscope. In some instances, it may
be desirable to reverse this situation and have the oscil-
7. Set the TRIGGERING controls to obtain a stable
display.
8. Set the T IM E /D IV switch to a sweep rate which dis­
plays about one cycle of the waveform.
9. Move the waveforms to the center of the graticule
w ith the vertical POSITION controls.
10. Turn the V A R IA B LE T IM E /D IV control until one
cycle o f the reference signal (Channel 1) occupies exactly
eight divisions between the second and tenth vertical lines
2-26