How to start data acquisition when a sine wave starts or finishes

[Portugues]

I am using a DAQ-1200 to analyse three waveforms, I need to start acquisition when any of the sinewave changes from zero to start and when it stops. However, I also need to some 600 samples before the triggering occurs and I do not know how to do this without causing a delay, can anyone help me please?

[bman]

The DAQCard-1200 does not support analog triggering, so one solution would be to continually acquire data and constantly check it with software, save the previous 600 points before the sine wave starts and continue checking the signal until it stops.

You may want to consider upgrading to an E-Series board that supports analog triggering. There, you could use one of the shipping examples that come with LabVIEW for your application. All you would need to do is enter in the threshold voltage to trigger on and how many pretrigger scans you would want, 600.

Brian

[Portugues]

Thank you Brian, I have tried the first but I always seem to be loosing somepoints, between the bufferring and the acquisition of the trigger. What I do is I acquire one point at a time and store it in a buffer. When the trigger level has reached, I do a continuous acquisition for a certain period of time, but I miss some points, which are crucial in the steps between both. Do you have any views on that? Thank you.