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