How can I set up a delayed analog trigger on PCI 6115 DAQ

[kab381]

I have an S-Series PCI 6115 DAQ which I’m running with Labview. I’m using it to measure signals from an acoustic emission sensor and two force transducers. I’d like to set up a delayed analog trigger which will start acquisition on all three channels a period of time after a selected channel’s voltage exceeds a threshold.

Currently I’m using the AI Config VI in line with the AI Start VI and AI Read VI to capture data after a analog hardware trigger occurs. A software trigger probably wouldn't work because I have to sample my data at 10MS/sec. My setup works fine for triggering without any delay or skip counts. However, if I set the delay or skip count in the additional trigger parameter field of the AI start VI, there is no effect, and the device still starts capturing data immediately after the trigger is received. What is the cause of this, and how can I get around it?

Also, is it possible to sample the channels of a PCI-6115 DAQ at different rates? Right now, I’m sampling all my channels at 10MS/sec and throwing away data on all channels except one. However, this seems relatively slow and eventually I would like to attempt pseudo-real time control using my data.

[rpursley8]

use the counter/timer to introduce the delay. Your trigger signal can trigger the counter/timer which will put out the signal to start the acquisition. This way you can have control over the length of the delay.

[Otis]

rpursley8 is right about needing to get the counters involved if you want a hardware timed delay in your application.

Concerning whether or not you can sample at different rate, check this document out.
Sampling Different Channels at Different Rates with NI-DAQmx

[kab381]

As I understand it. I can cause my analog trigger to set off a delayed pulse via a counter, which in turn would become the digital trigger for my data acquisition. However, I’m not sure exactly how to set this up in Labview. I know that an analog trigger creates an internal signal ATCOUT. How can this signal start a counter? Could the Counter set Attributes vi somehow be uses to select the ATCOUT to start a count or would I have to create a program that outputs to a PFI pin first and use that pin as the gate for the counter.

[rpursley8]

Take a look at the 'Gen Dig Pulse-Dig Start.vi' in the examples. This will show you what needs to be done to configure the counter.