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Guest Onion Yang

Temperature Control

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Guest Onion Yang

I would like to control different 3 temperature on same screen.

So, I try to make a file using PIDsample.ctl file (download at http://www.daqfactory.com/faq.php?do=artic...e&articleid=92).

But, This new file did not run correctly.

Help me Please !!!

If you have some sample for multi-temperature control.

Please send to me by email or attache at this topic.

Onion Yang / Manager/ Service Dept.

ezDAQ / South Korea

E-mail : alphavir@paran.com

Support@ezDAQ.com

Tel : 82-31-274-8434

Fax: 82-31-274-8435

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The post is over 3 years old and we have removed the knowledgebase. Some old links in the forum still exist. I've attached a PID sample. It is not the best sample because a realistic simulation that PID could act on is somewhat hard to simulate. Really the best way to try PID is to actually create a real system. You can do it with a beaker full of water, a thermometer and an electric heating element connected to a relay.

This sample will require DAQFactory 5.77 or newer.

pidsample.ctl

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Hello,

quick question. I am trying to use a PID to control a 0-10V actuator. So when the reference input drops the PID output goes up. That's good. However, when the input is back to setpoint I need the output to stay at the new adjusted value rather than going back to it's initial state. The same has to work the other way round. When the input goes up I need the output to start to decline and stop at the new output value as soon as the input meets the setpoint.

Can you point me in the right direction?

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First, typically you'll want the output of the PID to go to a variable and then use that variable to set the actual output. This is because the PID calculation returns a +/- number, centered around 0, so if you constrain it to 0-10V, half the PID calc won't work. If properly tuned, the PID should hold whatever value gets you to your setpoint. Note, however, that the combination of I and D parameters control the performance of the loop. If you need to get to the setpoint fast, you want more of an affect from I. If you want to make sure you don't overshoot, you need more of an affect from D.

That all said, you may not want PID at all. Presumably your actuator moves at a fixed speed, so you can simply adjust the output by some interval, say 0.1V, then wait however long it takes to move that distance, then do it again until you hit your setpoint. PID is more suited for situations where you have PV loss due to, for example, heat loss to the environment, or variable lag. You most likely have direct command / response.

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