BNC 725 - Manual (Page 51)

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Channel B, which will provide a precision “delayed indicator” pulse. The delay of Channel B will
be added to the “Desired Delay” of Channel C.
On the oscilloscope you will see that the delay between pulses on Channels A and D always settle
precisely to 10 µs (Desired Delay - Channel B delay), when the delay of Channel D is adjusted
anywhere between 35 ns to 3.5 µs, simulating drift. It may take several seconds before you
observe the settling of the delay because of the Averaging value of 256 triggers. Reduce the
Averaging on Channel C to decrease the settling time.
Note: A missed “indicator” pulse will cause the channel to conclude the correct delay is a large
negative time. When a channel detects that correct delay is negative, it produces a pulse at
6.4 µs after the trigger pulse, the shortest delay between trigger and output allowed. This
issue will resolve in one pulse if Averaging is not used. However, if Averaging is
employed, a large negative delay may take many successive delay measurements to
average away, during which time the channel will appear stuck at a 6.4 µs delay. This
condition can always be immediately cleared by pressing the “Reset” button for the
channel, which resets the average.
Three timing issues should be considered when using dynamic delay compensation mode:
1. Ensure that the trigger and indicator pulses never overlap in time.
2. Ensure that the properly compensated pulse occurs no less than 6.4 µs after the trigger pulse.
3. Ensure that the indicator pulse begins no less than 1.2 µs after the END of the output pulse of
the delay compensation channel.