Omron NJ and proportional gas valve

Hello, I have built a few temperature control loops in the past using the PIDAT instruction in Sysmac Studio, and control of electric heating. This project is my first gas control project with it. I am not sure if I just scale my output signal to the proportional valve so that......say 0-90 degrees (range of valve) is scaled to match the 0-100% duty cycle or what. I can't see any other way to control this. I am using the PIDAT instruction which I have used successfully in the past, for electric heating and duty cycle, but not opening and closing the valve. I thank you for whatever info you could provide.

I do not know what PIDAT decodes as, it means something (?).

The proportional valve has to have some sort of actuator that drives the valve stem, whether its rotary or linear.

The controller's output, 0-100% is what either the actuator expects as demand signal input, or that a 'positioner' expects as a demand signal input. The valve rotation or linear action, whether 0-90 Deg or 0-160 deg or 0-12mm or 0-25mm is accounted for in the actuator. The valve movement itself is considered 0-100%.

Typically a modulating valve is driven with a 0-10Vdc or 4-20mA signal.

danw said:

Typically a modulating valve is driven with a 0-10Vdc or 4-20mA signal.

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Yes, it does use a 0-10V signal. At 0 volts the valve is obviously closed, at 10 volts it is open 90 degrees (its max). The output card has a resolution of 8000 counts for -10V to +10V, so I use only a 4000 count to represent open all the way. I am able to manually open it to the degree of rotation I want. My question is probably applicable to all controllers, opening and closing a valve to increase, decrease, or maintain a temperature. As mentioned before, I have controlled temp with electric heating elements in the past but it uses a duty cycle, and an SSR, controlling its on-off time. I am not sure how this works when controlling using an analog signal to a valve instead of the duty cycle. Thank you for the reply.

PIDAT is PID auto tune.

BobB said:

PIDAT is PID auto tune.

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It was the only PID control function I could find. There is one for just PID and then another for PID Heat and Cool? It allows me to manually enter parameters for each control (P, I, &D). After reading about it it appeared to me as though I connect my 0-10V output to the "MV_Heat" and that drives it. Am I wrong about that?

Okay, I found the problem, hopefully this might help someone else. I was getting "PID_ERROR 0400". First, it was a data type issue at the T/C module. I had it set to INT and it must be REAL to use the PID function. I changed that. Then, I had to change the "_sINIT_SET_PARAMS" for low point. It assigned all these values because I used an example I found online. Once my PV went over that low value, "MV_Heat" started yielding an analog output. I then created a "TimeProportionalOut" function, pointed it towards my analog output card and there it is.