Why does amplitude come out as zero?

[heididebwil]

Hi,

I want to measure peak to peak of a square signal (0.1- 2Vac). I generate and aquire the signal using a USB-6008.

I have tried to do this in various ways as you can see in the attachments, but all I get is zero. The signal is being read perfectly.

Any idea what is wrong?

Heidi

[altenbach]

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heididebwil wrote:

I have tried to do this in various ways as you can see in the attachments,

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I only see one way, not various, in you attachment. Please explain.

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@heididebwil wrote:

..., but all I get is zero. The signal is being read perfectly.

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How can it be zero (what you don't want) and read perfectly (what you want) at the same time. Please explain.

(Sorry, I don't have DAQmx installed, so I cannot see your express configurations)

Are you sure the device name is set correctly? How are you running this? Why are none of you error out terminals wired, e.g. even to an indicator.

[heididebwil]

Hi, thank you for the quick reply!

When I acquire the signal and plot in the chart I get the signal I am generating as you can see below. But when I try to get the peak-to-peak it comes out as zero no matter what amplitude I choose to generate. I have tried to get values with the Amplitude and Level Measurement VI, and in two other ways that I have found in this forum.

Hope the picture clarifies? 

[altenbach · Accepted solution]

As I said, I cannot look at your DAQ express VIs, because I don''t have DAQmx installed.

From your description, maybe you are only reading a single point per iteration. Try to put a collector configured for a suitable history lenght before the analysis VIs. See if it makes a difference.

[heididebwil]

Fantastic, that did the trick!