BNC 725 - Manual (Page 50)

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Channel C: Dynamic Delay Compensation: Delay: 2.000 ms; Duration: 10.000 µs
Averaging: None (1 trigger)
Trigger Input Logic: inC = outA | out B;
Connect a cable from Channel A to one oscilloscope input and a cable from Channel B to another
oscilloscope input. If you have more channels, you can also connect Channel C to the
oscilloscope.
The delay between channel A (Trigger) and B (Indicator) will be exactly 2 ms, even though you
never specified to Channel C the delay required to trigger Channel B at the right time. The mode
determines the delay by observing the indicator pulse.
Next, increase or decrease the delay of Channel B between 20 µs and 2 ms. For the first cycle
after the adjustment, the delay between A and B will be something other than 2 ms, then every
following cycle the delay will be precisely 2 ms.
To account for sensor noise and device-timing jitter, you can use the Average Delays option on
Channel C’s Averaging tab. Set the value to 256 triggers and again adjust the delay on Channel B
between 20 µs and 2 ms. The timing error will not resolve itself in a single cycle as before;
instead, the timing relaxes to the correct value over a large number of cycles.
Now, suppose you need to do a dynamic timing adjustment but the indicator trigger occurs very
quickly, perhaps even during the Dynamic Delay Compensation output pulse. Starting with the
setup described above, make the following changes:
1. On Channel B set the input logic to “inB = outD;”, the Delay to 10 µs and the Duration to 10
µs.
2. On Channel C set the Desired Delay to 20 µs and the Duration to 8 µs. Leave the Averaging at
256 for now.
3. Set Channel D to Delayed Pulse After Trigger. Set the input logic “inD = outC;”, the Delay to
1 µs and the Duration to 10 µs.
4. Click Program > Program All Channels.
5. Disconnect the cable from OutB and connect it to OutD instead.
Channel D’s output now represents a fast-arriving indicator pulse. It arrives 1µs after Channel C
starts its 20 µs-long pulse—before Channel C starts looking for the indicator pulse. Because it
arrives so soon, the pulse cannot be logically routed directly to Channel C; instead, it is routed to