Fluke PM3370B user manual Alt/Chop

FUNCTION REFERENCE 5 - 7

ALT/CHOP

Description:

In the analog mode, when two or more channels are selected, the oscilloscope displays multiple channels in a ‘time shared’ mode. This implies that a fast electronic switch connects each input signal to the output amplifier in turn. This can be done at the end of every sweep, or at a high frequency. The display modes are referred to as Alternate or Chop modes.

Alternate mode: After each sweep of the time base has been completed, the channel switch selects the next channel to be displayed during the next sweep. The result is that each channel is displayed one after the other. At fast timebase speeds this mode assures maximum intensity, while slow timebase speeds in alternate mode result in a flickering display.

Chopped mode: In this mode, the channel selector switch operates at a high frequency, and is no coupled to the time base sweep. This mode is recommended for slow timebase speeds. The display switches very fast (1 MHz) between the channels, which results in what appears to be a simultaneous display of all channels.

ALT/CHOP is not available with single trace display.

In the digital mode channel 1 and channel 2 each have their own digitizer for simultaneous sampling on both channels. In this two-channel mode ALT/CHOP is not active.

If a combination of channel 1 or 2, and channel 3 or 4 is selected, the ALT/CHOP is active and functions in the following way:

ALT results in a complete memory acquisition of channel 1 or 2 simultaneously sampled, followed by a complete memory acquisition of channel 3 or 4, also simultaneously sampled.

CHOP results in a single sample being made on channel 1 or 2 followed by a single sample on channel 3 or 4. This continues until the acquisition memory for each channel is filled. This ALT/CHOP function is valid only for the real-time sampling timebase speeds.

NOTE: For further details on three or four channel operation, also refer to the ACQUISITION LENGTH and PEAK DETECTION functions.