How to get the position of the stem in control valve using slider control in the front panel

[vinodboss]

I have created a calibration program for a control valve. Signal (4-20mA) is generated from labview using slider contorl which is given to the valve via DAQ(module 9265) and again the feedback signal from the valve is acquired using DAQ(module 9203).. . There is an input ISO/ISC(Increasing signal to open/ Increasing signal to close) in the front panel.

ISO would set the output to increase from (4-20)mA further opening the valve

ISC would set the output to increase from (4-20)mA further closing the valve

I have doubt, how can i get the position of a stem

[RavensFan]

What do you mean you have a "doubt"? Do you mean you have a question?

I don't understand what your question is?   If the position of the stem is being sent to the PC through a 4-20 mA signal into your DAQ 9203 module, then you just need to do an analog input read in order to get the signal.

Or are you having issues with a feedback control loop such as a PID loop?

Can you post your VI so we can see what you've done so far so we can have a better understanding of your question?

[Ray.R]

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@Ravens Fan wrote:

If the position of the stem is being sent to the PC through a 4-20 mA signal into your DAQ 9203 module, then you just need to do an analog input read in order to get the signal.

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When reading this post, that is what came to mind...  So let's see if both RavensFan & I are trying to understand the same thing...  Are you saying that the position of the stem is linear (or scaled) to the amount of current sent to it?  Meaning a 4mA signal would move it a certain distance, and 10mA would move another given / known distance?  Or are you saying that it is calibrated so that a 20mA signal for a certain duration (ms) would move it a given distance? So the scale would be time and not current unless a lookup table is used to adjust the time duration based on the current being drawn...

It's just that I am not familiar with solenoid / drive devices that related to current..  To voltage, yes.  To time, yes..  To current, I'm simply saying that I am not familiar with that.  Can you tell us more about this stem (mfg / model designation)?