Hello All,

Briefly, I want to control a proportional valve which is used on a steam pipe. Thermal sensor is PT100. If I want to use "PI" block for controlling, how would I use the feedback signal (e.g. potentiometer) of valve status?

I cannot open the valve completely because of safety reason, pressure and steam flow. I should control the valve by increasing or decreasing the gate of valve (for example) 5% at each step.

Any other solution if I don't use "PI" block?

My deeply appreciating in advance.

Best regards

Hello Betel,

Thank you very much in advance for your help and guide lines.

All of your posts and links are wonderful.

I think I've found some ideas and good techniques from forum, to prepare the best solution. Now, it’s time to move. I will attach the solution here as an applicable work. These coming days I would be very busy at work. I should just focus on my project.

Thank you Betel again for all of your efforts and kindness.

Truly yours,

Reza

Hello Betel,

Thank you very much in advance for your reply.

Due all respects, here are my answers to your questions:

a) My LOGO! device will be a 12/24 OBA6 with LOGO! TD.

b) Yes, I do. It is clear to me that I must use AM2 RTD module.

c) I want to use a valve which has a small dc motor for open/close the valve’s gate. if we disconnect the motor electricity, valve will remain at its position.

d) :

1. All electrical connections for PT100 are all right. I use three-wire method. Cable has grounded shield.

2. I didn’t understand what you mean. If you mean noise existence, there isn’t any significant noise there.

3. I didn’t calculate the parameters of PI (I was lazy to use of Ziegler–Nichols method or something like that). I was using trial & error and best result was in P=0.7 & I=5 sec.

4. We can control the speed of valve’s gate reaction by control the rate of switching on/off the motor.

5. No, I didn’t calculate the PI parameters as above I said.

6. Referring to your recommendation to cascade two amplifiers resolution would be x0.25. But in analogue blocks at software, if we choose PT100/PT1000 as sensor, there are two options for resolution x1 & x0.1. Software itself offers these two possibilities to select proper resolution. Do you confirm this resolution?

Resolution is not very important as stability is.I mean, I need a stable control.

7. I agree with your idea to use an extra temperature controller to achieve maximum safety. A professional technique.

As an experience I would like to test your wonderful program “DEMO_HeatController_V01.lsc” but in Chilling mode. Would you please modify it for me?

Best regards,

Reza

Hello Betel,

Thank you for your help and modified program.

I will check it out and put the answer here.

Best regards,

Reza