Data Acquisition (DAQ) and Control from Microstar Laboratories

Knowledge Base: Processing

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Q10060 Selecting data blocks with delay

Tags: Help, DAP, data selection, software triggering, delayed capture

Applies to: All DAP and xDAP products, all DAPL versions

The signal I want to measure is irregular and low-level, hence not good for software triggering. I have another signal that is much better for reliable triggering, but there is a known delay between this signal and the one I want to measure. Is there a way to trigger at one point, but then retain data later?

Maybe there are too many ways! You can use the method that seems easiest to you.

  1. Use a shifted data stream for your triggering analysis.

    Define a pipe and use a FILL command to put artificial values such as zero into the pipe, something that your triggering analysis will not respond to. Now use a DAPL expression task or a COPY task to place the actual triggering signal data into this pipe. The extra padding data will shift the location of your trigger event.

  2. Modify the positions of the trigger events.

    Define a second trigger, and use a TRIGSCALE task to add a positive number of shift positions to each trigger event you get from normal triggering analysis. Use the modified events to retain you measurement data.

  3. Capture extra data, and eliminate the parts you don't want.

    Define an extra data pipe. Configure your WAIT command to retain all samples from the triggering event to the last sample you want to retain. Then, use a SKIP task to drop the samples you don't want from the beginning of each block, placing the samples you want to keep into the extra data pipe.

  4. Use new DAPL 3000 features of the WAIT command to specify the delay you want.

    A typical, positive pre-trigger count parameter in a WAIT command tells it to start by retaining a positive number of samples prior to the event. By extension, a negative number is interpreted as avoiding samples – for example, a pre-trigger count of -200 would tell the WAIT command to bypass 200 samples from the trigger event onward before retaining data.


There is an online tutorial about software triggering with several application examples.