Tektronix 2225, Operator'S Manual

Page: 49 / 79

Applications
Phase Difference
In a similar manner to the preceding measurement, you can make
a phase comparison between two signals of the same frequency
using the dual-trace feature of the 2225. This method of phase-
difference measurement can be used for signals with frequencies
up to the limit of the vertical deflection system. To make a phase
comparison, perform the following procedure:
1. Set the TRIGGER SOURCE switch to CH 1.
2
. Set both input coupling switches to the same position,
depending on the type of input coupling desired.
3. Using either probes or cables with equal time delays, apply a
known reference signal to the CH 1 input connector and
apply the unknown signal to the CH 2 input.
4. Set VERTICAL MODE to BOTH; then select either ALT or
CHOP, depending on the frequency of the input signals. The
reference signal should precede the comparison signal in
time.
5. If the two signals are opposite in polarity, set the middle VER­
TICAL MODE switch to CH 2 INVERT to invert the Channel 2
display.
6
. Set both VOLTS/DIV switches and adjust both variable (CAL)
controls to display equal-amplitude waveforms.
7. Adjust the TRIGGER LEVEL control for a stable display and
center the display vertically.
8
. Set the SEC/DIV switch to a sweep speed that displays about
one full cycle of the waveforms.
9. Position the displays and adjust the SEC/DIV variable (CAL)
control so that one cycle of the reference signal occupies
exactly eight horizontal graticule divisions at the 50% rise­
time points (see Figure 3-8). Each horizontal division of the
graticule now represents 45° of the cycle (360° divided by
8
divisions), and the horizontal graticule calibration can be
stated as 45° per division.
3-12 2225 Operators