Using an encoder to initiate and time discreet sampling

[walter-donovan]

I can't really get a grasp on what DAQmx subs to use and how to configure them. It should be a simple task, but not for a beginner like myself. Disclaimer: I have spent hours reading help files, knowledge base articles and forum searches and there's nothing in them that makes sense to me. Op details are in the block diag. Please take a look and see if you can steer me. Thx.

BTW... Using MAX test panels I have verified operation, wiring, and configuration of my sensors. With the attached vi, pgm does not wait for the start signal but initiates whenever the first 'A' pulse arrives. This verified because the encoder can measure data without ever passing the 'Z' pulse.

Message Edited by walter-donovan on 01-22-2009 09:31 AM

[MikeS81]

Hi walter-do...,

Did you see the example finder? There should be an example about what you need.

Mike

Message Edited by MikeS81 on 01-22-2009 04:32 PM

[walter-donovan]

With all due respect Mike, I intentionally wrote a disclaimer in my thread to avoid questions like this. Yes I opened, ran and studied  every example that seemed relevant. In fact the code I attached is a modification of one of these examples.

[MikeS81]

Hi walter-do...,

i read the disclaimer, but you didn't say something about the example finder. If i wrote my first answer, you haven't attached your vi.

Sorry for the question.

Please see the "Acq&Graph Voltage-Int Clk-Dig Start&Ref.vi" from the example finder, i think it shows what you need.

Hope it helps. 

Mike

[walter-donovan · Accepted solution]

Thanks Mike. I retrieved that example and it's one I already had downloaded. It doesn't work. After receiving the Start pulse, it reads all samples at the clock sampling rate, not at the edges of the reference trigger pulses. The example is wrong. So I did what I normally resort to in these cases.... wandering around banging my head against the wall until something gives.

Solution. Fix the example by wiring the  reference trigger source control into the clock source input as well as into the reference trigger sub vi (this wire already exists). Now it works like it's supposed to. Hard learning from examples when the examples are wrong. Here's the fix in case any one els tries to learn from this example.