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Need hwlp with writing a VI program for current, voltage and energy DAQ

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  1. You sent a picture hard to debug.
  2. You do not need the Write to Measurement File express VIs if you follow the previous advice I have given you.
  3. The broken wires are connected, impossible to tell which VI is breaking it, but me thinks it is the Write to Measurement File express VI. Hint try disconnecting it.
  4. This is your thesis project, as evident from the title. I will emphasize "your thesis project". Isn't part of you learning experience actually learning how to figure this out?


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Message 11 of 17

I have been trying to figure out various combinations and various possibilities to try and figure out what is going wrong and posting on the forum as a last resort. I have been using google and NI tutorials as much as possible before posting on here. The broken wires are caused by the measurement VI, but the issue being the error is not at the DAQ assistants. They are working fine. The problem is connecting the measurement file to the power and energy VIs.

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Message 12 of 17

You are trying to write an incompatible signal to the Write To Measurement File VI. The power and energy VIs cannot directly write to the express vi from their output. You need to figure out a way to do it in LabVIEW or do it post processing since you have the current and voltage.


I do not have the add-on to test, so good luck.



Message 13 of 17

Another potential problem to think about.


Power = V I cos(theta)


Right now your current and voltage measurements are not synchronized, you probably have a phase error between the measurements.





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Message 14 of 17

The power vi from the EPS suite has the calculations taken care of to calculate the power and energy from the measured current and voltage values.

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Message 15 of 17

Your problem appears to lie inside the two functions Energy and Power, which those of us without the special add-on Toolkit you are using will not have.  Look at the Help for those functions (or, better yet, do away with the Dreaded Dynamic Data Wires, use "real" LabVIEW constructs such as Arrays and Waveforms, and do the calculations yourself, using the required knowledge for your Thesis Project).


My earlier advice about using "local help" (someone there must know LabVIEW and be able to mentor you) to learn how to solve these kinds of Engineering Problems.  What good is a Degree in Engineering if you can't (by yourself) solve Engineering Problems?


Bob Schor

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Message 16 of 17
Accepted by jama223

The Write To Measurement File express vi is expecting the Dynamic Data type on the Signals input terminal, while the output of each EPS function is a 1D array of clusters.

Thesis Program.png

Message 17 of 17