timing info of start trigger

[LCHEN5154]

Hello all,

 I am using a high speed digitizer NI5154 to capture waveforms form a detector. When NI5154 received the start trigger it will start capture pulses in the input channel. One thing we want to know is the time gap between the first captured pulse and the start trigger. I tried but havn't figure out a way to do this.

 The pulses were captured according to preset parameters- trigger level, waveform length ...

 One way I think might work is to change the triger condition so that the digitizer will capture a "pulse" right after it received the start trigger and then reconfigure the digitier for normal pulse capture. But I am worried it may take too long to refonfigure the digitizer since we expect a pulse burst ( a few k/s) shortly after the start trigger.

 please advise. I appreciate your help.

[Matt_L]

Hi Lixin,

The short answer on the time gap, is that it depends; i.e. small things like path length depending on trigger and acquisition channel can cause this to vary.  You can find out how long the gap was for a given acquisition by reading the relativeInitialX property, as detailed here , but it sounds like your main concern is that you don't want to miss the sample right next to the start trigger.  If that's the case, I would recommend acquiring a small amount of pretrigger samples, which you can setup in the Horizontal Timing configuration as demonstrated here: http://digital.ni.com/public.nsf/allkb/082C5FA24EFA18AD862572AB0063FCC5.  Even if the first pulse comes in before the triggered acquisition actually starts, you should still recover it as a pretrigger sample.  Hope this is helpful!