How do I acquire signal few seconds before triggering

[Nolimit]

Hello guys,

I am working on impact test and I want to acquire signal few seconds before trigger starts. How do I configure my DAQ assistant to do that?

Thanks.

[Henrik_Volkers]

Well usually you configure your DAQ device (Which one do you use?) to continiously capture data into a ringbuffer and set the triggerposition to 20%-50% (related to the number of samples you want to read). After the trigger is set the start of your data will be set by the driver. 

All this is done by the DAQmx or scope driver. Just set the samplerate, number of samples, trigger and position of trigger.

[Nolimit]

Hello Henrik,

I am using NI PXIe-6124 data card and labview version 10.The Ni-scope seems not to work with my device.I want to acquire analog signals few seconds before trigger and after trigger.At the moment i am using the DAQ assistant VI to acquire the signal.

[AlanArmstead · Accepted solution]

If you have access to the Sound & Vibration Measurement Suite, it includes a LabVIEW impact test example that will help you to easily configure your hardware and software.  It gets installed here:  <vi.lib>\examples\Sound and Vibration\Vibration Test\SVXMPL_Advanced Impact Test (DAQmx).vi  

If not, you may want to look at the DAQmx example called:  Acq&Graph Voltage-Int Clk-Dig Ref.vi

That example and many others are here:

<vi.lib>\examples\DAQmx\Analog In\Measure Voltage.llb 

-Alan

[dsb@NI]

Use the DAQmx driver for the 6124. What kind of impact testing are you doing? If it is with an instrumented hammer and one or multiple vibration responses, use the Advanced Impact Test Example that Alan referred to. If you are doing other types of impact test, please share more of the test requiements, and we may be able to point you to more specific examples that implement a suitable circular (ring) buffer proposed by Henrik.

[Nolimit]

Hello Doug,

Thanks for the information.I used the DAQmx SW example trigger example designed by Henrik of Cummins and modified it to get what i want.Thanks