Why is the triggering of DAQ input signal not working like I'd expect?

[westerman111]

Using the DAQ-Assistant, I am inputting a signal at a rate of 100k Hz and sample count of 75k. I would like a light to turn on every time the amplitude of this signal goes below 1. As you can see from my attached graph, the amplitude goes below 1. However, the light is not turning on. Any suggestions on what I am doing wrong or misunderstandings I might have? This is my first project with the DAQ-Assistant, so maybe there is something simple that I'm missing.

[Rubikon · Accepted solution]

Hi

The problem in your VI is that you acquire 75k samples but you only check if the second sample is below 1V.

That's because of the Index Array node, it will only give you a single element from the array which means a single sample.  

You should either take just one sample at a time, or send the incoming array through a indexing tunnel. But that might slow things down when you have so many samples.