niDMM PXIe-4081 PXI-Trigger

[refi1]

Hello,

I have a PXIe-4081 which is configured for voltage waveform measurement. The trigger source is configured for PXI-TTL0, Trigger delay is 0 and settling time is also set to 0.

I generate the trigger pulse for PXI-TTL0 with a vxinstruments digitizer. The PXIe-4081 receives that trigger pulse and acquires a measurement but it seems that the first samples are before the actual trigger. The acquired waveform start 2-3µs before the trigger event.

Is this behavior normal? Are there any other settings I could try?

Thanks in advance.

[sherlockholm · Accepted solution]

Hi,

Looking at the spec sheet under timing for the 4081, it shows the latency is <0µs. Looking at note 48 of the 4071 spec sheet is says, "The latency specification value actually reflects negative latency due to sampling before the trigger. Can be reduced to near zero (with the jitter specification) or made positive in software by adding a trigger delay."

So, it appears this is to be expected.

[refi1]

Ok, with the note 48 of the 4071 spec it is a bit clearer.

My problem is that the latency varies with each measurement so setting the trigger delay will just reduce the problem. But I think I will have to live with that.

Thank you!