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?

[Dennis_Knutson]

If I understand correctly, it sounds like you want to display a triggered waveform and also display the pre-trigger data. If I'm right, you might want to look at the example at http://zone.ni.com/devzone/explprog.nsf/webmain/819BCD38C73C5105862568660060F464?opendocument&node=DZ52308_US. In the example, the daq card does a continuous buffered acquisition with LabVIEW retrieving the data when the data in the buffer meets the trigger specifications. It's been a long time since I've done it, but I believe it was fairly simple to specify how much pre- and post- trigger data to retrieve. Good luck.