Philips PM3350A - Page 39

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4 APPLICATIONS
- Selection of ALTERNATED or CHOPPED display
by pressing the ALT/CHOP key
This selection is used If two signals are displayed.
In alternate mode, the CRT beam alternately traces one signal sweep and then
the other. At low repetition rates this can be seen, so ALT is mainly used for high
speed time-base settings (from around 0,1 ms/div and above).
in chop mode, the beam chops from one signal to the other at a fast switching
frequency and is therefore suitable for low speed signals.
At high frequencies interference can occur between the switching signal and the
measured signal, so take care when using the chop mode with high frequency
signals.
. Selection of ADD, NORMAL or INVERTED display
by pressing the ADD/INVERT key.
"INVERT" is active on channel B.
In the ADD mode, channel B is added to channel A (A + B).
in the ADD INVERT mode, channel B is subtracted from channel A (A-B).
The differential mode (A-B) is useful for rejecting common-mode signals. By
measuring in differential mode, the common-mode signal on one channel cancels
out the common-mode signal on the other channel, leaving the actual signal
visible on the display.
A practical application of the differential mode is to eliminate hum from a signal.
4.1 USE AS AN ANALOG OSCILLOSCOPE