ignore multiple triggers

[marc lawrence]

Dear all

I am sampling a signal which is generated on an external device : which is also capable of sending triggers at the start of each waveform (Keithley Instruments 6221 Current source). Currently we trigger our DAQ as soon as a pulse arrives (from the 6221) - and ignore any other pulses. However I would like to configure the system to ignore the first n pulses, then trigger.

the ideal way would be to configure the AI Trigger to ignore n pulses, but I could not see how to do this. Another way would be to configure the trigger to a counter, count n pulses, and then cause this counter to trigger the DAQ... but this seems a lot of hassle for something relatively simple. The final way would be to use a delay such that we initiate the current source, wait x seconds, then set up the AI Trigger and AI Start, then capture on the next pulse.

Is there an easier way - what would other people recommend?

many thanks

Marc

[thayles]

Using a counter as you describe is probably the best approach. You would configure a counter output task, set the source if ticks to your 6221 trigger signal and set the high and low ticks according to the number of triggers you want to ignore. You would configure the counter's internalOutput terminal as the source for your DAQ board's digital edge trigger.

There is also a property called Delay from Start you could try. In LabVIEW it is in the trigger property node. You can configure a timed delay that begins when your digital edge trigger arrives and begins the acquisition once it expires.