Tektronix 2245A Operator's Manual page 85

d. To have similar responses for both channels, use the same Input
COUPLING for both CH 1 and CH 2.
The following procedure shows how to eliminate an unwanted ac input-
power frequency signal component from the displayed signal.
a. Perform the " Initial Setup" in "OPERATOR CHECKS AND ADJUST­
MENTS" Section 4, but do not apply any signals and center the baseline
trace vertically.
b. Apply the signal of Interest containing the unwanted line-frequency
component to the CH 1 input connector.
c. Apply a line-frequency signal to the CH 2 input connector. To maximize
cancellation, the signal applied to the CH 2 Input must be in phase with
the frequency component to be canceled from the CH 1 signal.
d. Select CH 1 and CH 2 Vertical MODE.
e. Set Trigger SOURCE switch to VERT.
f . Set both VOLTS/DIV switches to produce displays of about two or three
divisions in amplitude.
g. Adjust the CH 2 VOLTS/DIV switch and VAR control so that the CH 2
display is about the same amplitude as the component to be canceled in
the CH 1 waveform (see Figure 5-7A).
h. Select both ADD and CH 2 INVERT. Turn off the CH 1 and CH 2 dis­
plays and slightly readjust the CH 2 VOLTS/DIV VAR control for maxi­
mum cancellation of the line-frequency component (see Figure 5-7B).
I. The SEC/DIV setting may be set to a faster sweep speed to expand the
waveform and the display amplitude may be increased by advancing
both VOLTS/DIV switches and readjusting the VOLTS/DIV VAR con­
trols as necessary to maintain cancellation of the undesired signal
component.
2245A Operators
Basic Applications
5-15