Tektronix 305 DMM

...... ............... rnvuu MVjwviiwii
Some signals may contain undesirable frequency com
ponents, as shown in Figure 19. Common mode rejection
can eliminate or reduce these components from the meas
urement. Use the following procedure to reduce or elimi
nate an undesirable line frequency component:
1. Apply signal to CHI INPUT connector.
2. Apply line frequency signal to CH2 INPUT connector.
3. Set the Vertical Mode to ALTernate position.
4. Pull the PULL: INVERT knob to invert the channel
2 display.
5. Adjust the CH2 CAL (Variable) control so that the
amplitude of the channel 2 signal compares or is equal to
the undesired signal component of channel 1 display.
6. Set the Vertical Mode to ADD and readjust CH2
Variable control for maximum rejection ol the undesired
signal component.
CH 1 tklUNAL
WITH
UNWANTED
LINE
FREQUENCY
COMPONENT
CH 2 SIGNAL
FROM LINE
FREQUENCY
SOURCE
(INVERTED!
A. CH 1 AND CH 2 SIGNALS
SIGNAL WITH
LINE
FREQUENCY
COMPONENT
CANCELED
OUT
(2237-17)
2424-21 B. RESULTANT SIGNAL.
Figure 19. Common mod* r*|*ction of an undesired line-frequency.
32
305 Operators
REV A SEP 1979