Tektronix 422 - Page 38

Operating I nstructions—Type 422 AC-DC
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(A) Channel 1 signal.
(B) Channel 2 signal.
(C) Resultant display.
Fig. 2-21. Using the ALG ADD feature for common-mode rejection: (A) Channel 2 signal contains desired information along with
line-frequency component, (B) Channel 2 signal contains line-frequency only, (C) resultant CRT display using common mode rejection.
8. The signal which remains should be only the desired
portion of the Channel 1 signal. The undesired signal is
cancelled out.
EXAMPLE. An example of this mode of operation is
shown in Fig. 2-21. The signal applied to Channel 1
contains unwanted line-frequency components (Fig.
2-21 A). A corresponding line-frequency signal is connected
to Channel 2 (Fig. 2-21B). Fig. 2-21C shows the desired
portion of the signal as displayed when common-mode
rejection is used.
5. Set the TRIGGERING Source switch to CH 1 & 2.
6. Set the vertical Mode switch to ALG ADD. Pull the
INVERT switch so the common-mode signals are of oppo
site polarity.
7. Adjust the Channel 2 VOLTS/DIV switch and VAR
IABLE VOLTS/DIV control for maximum cancellation of
the common-mode signal.
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i
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