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PID control of flow rate

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Yeap, that should be the case but I contacted with the NI supplier and tomorrow they are going to give me separate cd with pid toolkit.

The first scaling is the calibration equation to convert the voltage to the pressure difference. The second one is the flow rate equation that is in the attachment as screenshot_1. Sorry, I am going to check all those things tomorrow because I am out of the lab right now. 😞


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Message 21 of 23
Accepted by topic author Aeros08

Ok, when you get back to the lab, I recommend you do the following:

1) Put down this VI for a second and make a simple one that delivers a user-specified voltage to the system:

  • Make an excel graph of input voltage to output flow rate (remember your units)
  • Check that V_out is what you expect
  • Check that [Flow rate symbol] returns as something that makes sense.
    • Bonus: While you're here, make a graph and get the trendline and R^2 value. (In the US professors like seeing this chart as proof of concept 😉 )

2) Go back to this Vi,

  • Check your units.
  • Make sure that whatever "output value" is, it matches what your chart shows "should be"
    • Bonus: While the multiple nodes here are good for debugging, you may want to reduce the number of computations with a Formula Node

Hopefully, that will give you a solution. 

Just checking: You're making sure that your "set point" and "numeric" are in the same unit? Both these inputs should be your flow rate while output should be voltage

Message 22 of 23

Thank you very much for the great help :).  I will do tomorrow as you suggested, I will check all of them. Yes you are right set point and numeric should be in the same unit but the output should be voltage.

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Message 23 of 23