Trigger from DAQ data

[Haggis2013]

I've recently purchased a NI DAQ (NI USB-6356) and wouild like some help with Labview code.

I have low level signals (+noise) coming into the A/D continuously. What I'd like to do is create a trigger from the input signal itself, so that when the signal rises above a certain level, I want to store and process my samples. Ideally I'd like to store say 10,000 samples before the trigger, and 40,000 after the trigger, so that I can process the data before the Trigger as well. THis is because very low level signals may already be contained in the signal before the larger signal triggered, and with further analysis (FFT) I want to extract this data.

Can you please point me in the right direction on how to proceeed. I'm fairly new to Labview, although I have plenty of hardware experience.

Thanks a lot!

[Marand]

Hi,

What you need is to use an analog Triggering with Hysteresis. Hysteresis adds a window above or below the trigger level and often is used to reduce false triggering due to noise or jitter in the signal, so you need to add a DAQmx Trigger,vi at your VI and select Reference >> Analog Edge. You can see more information about Tips and Techniques in Data Acquisition Triggering - NI-DAQmx at the following link:

http://www.ni.com/white-paper/4329/en

Regards,