5. Measure the horizontal difference (in divisions) be
tween corresponding points on the waveforms.
Operating Instructions—455/A2/B 2
6. Multiply the horizontal difference by the magnified
sweep rate (4.5°/division).
Example:
The horizontal distance measured is 6 divisions (see
Fig. 2-8). The magnified sweep rate is 4.5°/division.
Substituting the given values:
Phase Difference = 6 divisions x 4.5°/division.
Phase Difference = 27°
Common-Mode Rejection
Some signals may contain undesirable components.
Common-mode rejection can eliminate or reduce these
components from the measurement.
Example:
The displayed signal contains an undesired line-frequency
component (see Fig. 2-9A).
CH 1 SIGNAL
WITH UNWANTED
V
V ■
s
"S.
>
\
CH 2 SIGNAL l(
\
>
iTrp
in f "
\
\
N
N
FROM LINE f
SOURCE
{INVERTED)
(A) CH 1 AND CH 2 SIGNALS.
SIGNAL WITH
LINE FREQUENCY
COMPONENT
CANCELED
OUT
i<
• ^ m
“ j
IB) RESULTANT SIGNAL.
Use the following procedure to reduce or eliminate the
line-frequency component:
1. Apply the signal to the CH 1 input connector.
2. Apply the line-frequency signal to the CH 2 input
connector.
3. Set the VERT MODE switch to ALT.
4. Set the INVERT button so that the Channel 2 display
is opposite in polarity.
5. Adjust the channel 2 VAR control to make the Channel
2 display amplitude about equal to the undesired com
ponent of the channel 1 display.
6. Set the VERT MODE switch to ADD and slightly re
adjust the Channel 2 VAR control for maximum rejec
tion of the undesired signal component (see Fig. 2-9B).
Cascaded Operation
Maximum vertical sensitivity can be increased to approxi
mately 1 mV/div by cascading the CH 1 and CH 2 ampli
fiers as follows:
1. Connect the CH 2 OUT signal (rear of main module)
to the CH 1 input via a 50 Cl cable and a 50 £2 termination.
2. Set the VERT MODE switch to CH 1.
3. Apply the input signal to the CH 2 input connector.
NOTE
In this mode, bandwidth is lim ited to about
20 MHz.
Time-Duration and Frequency Measurements
To find the time duration between 2 points on a wave
form, m ultiply the horizontal distance (in divisions) be
tween the 2 points by the TIM E/DIV switch setting.
Frequency is the reciprocal of the time duration of one
cycle.
Fig. 2-9. Common-mode rejection.
2-10
REV. A, OCT 1975
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