Buffering Analog Inputs In C#

[ere4iam]

Hi, I'm using the PCI 6229 to test a circuit board for Visual C#.  In part of the test, I am opening and then closing a FET to charge an inductor.  When it closes, I'm looking at the output to make sure that the clamping diode holds it to a peak value.  This happens really fast, though, and I can't seem to catch the event.  The event starts about 10uS after closing the FET, and lasts for about 30uS or so.  The DAQ card is fast enough to record this, but it seems like it takes too long after starting to read the input.

What I read sounded like I can buffer the measurements on the DAQ card, and then go back and read them.  This way I can start storing the measurements before I close the FET.  Starting with a trigger would also work.  I can't seem to get either of these working, however.  If anyone can help me, I would be very much appriciative as I've come into this project halfway through it, replacing another software-engineer, and I haven't done interfacing with the DAQ card before.

Thanks very much,

Timothy Burbridge

[John_P1]

Hi Timothy,

Welcome to the NI forums!  The 6229 is capable of acquisition up to 250 kHz, so this should be fast enough to sample several (7 or 😎 times during the 30 uS window.  Make sure that you are using hardware timing (as opposed to the On-Demand sample mode) to achieve this sample rate. 

From what you've described, I would recommend configuring your task to acquire a finite amount of data based off of an analog reference trigger.  This would enable you to begin your acquisition when your input reaches a specified threshold.  I would start with the shipping example AcqVoltageSamples_IntClkAnalogStart, which I've attached to this post.  If you need to, you can configure the task to acquire pretrigger samples using the ReferenceTrigger.PretriggerSamples property.

-John