Creating a virtual channel that increases a counter for every iteration of a cyclic load test

[JaRay200]

We will be performing a long period of cyclic fatigue testing, and I would like the ability to keep track of which iteration we are on for that block.  The current plan is to test for 10 hours at 15Hz then stop testing for 2 hours to perform an inspection of the structure.  Afterwards testing will start back up.  Each of these 10 hour blocks can start at a count of 0, but I would like to track the output of our loadcell so that when it sees a rising edge (with filtering to account for any noise) it will increase a counter by 1.  Every sample will then record this number as a separate column in the data file.  It doesn't have to be perfect as far as when on the rising edge it sees the new cycle, but it does need to be accurate in a way that it doesn't miss or count an extra cycle.  

Is somethign like this possible in Signal Express Full?

[DigDoug · Accepted solution]

Yes, what you are proposing is possible with SignalExpress Full. You can call LabVIEW code from signal express, so calling a VI from LabVIEW that contains your counter code is one way to do it. If would like to do this entirely in SignalExpress you can use DAQmx functions by navigating to Add Step > Acquire Signals > DAQmx Acquire and set up a Counter Input task to match your needs.

[JaRay200]

Due to funding reasons, this project will only be using signal express full.  In fact my copy came in yesterday about 3:30, so I plan to start using it now.  I have a separate copy of labview on my development machine that has Signal Express, but I am unable to connect to the SCXI-1600 I am using with 64-bit windows. 

Hopefully I can try this out today or tomorrow.  Thanks for the response.  

[JaRay200]

What I am running into is when I try to create a counter through DAQmx, I am getting the "No Supported Devices Found" error. I am planning to use only NI SCXI-1520's for this test in order to measure strain, but I will also be using them to measure load cells and voltage out.  How do I go about applying a counter in this situation?

[DigDoug]

It turns out that the SCXI-1520 card does not have an on-board counter. In order to use the counter functions I mentioned in my previous post, you must use a card with a counter. I do not believe that simulating a counter will work as it will not be directly tied to your input. If you are just worried about the total number of cycles you may be able to get that information by performing a limit test and statistical analysis on your signal so you can see the number of times the signal has crossed a certain threshold. These functions can be found under Add Step > Analysis > Time-Domain Measurements/Test and Compare.

[JaRay200]

I'll look into the limit test, from the looks of it I think that will work. Right now, since I can now save to ASCII I am trying to figure out how to save all the channels properly.