Plc 5/04 PID loop

[Guest fcflores]

Hello, I have an application at work were I will be controlling a heater plate that is forty feet away from the Plc 5/04 controller. I have two questions; how far can thermocouple wires be ran and do any of you guys have a standard PID Loop example I could look at. Thanks

[ICTechs.com 0]

As far as the TC being 40 ft, you should not have any problems. Thermocouples are good, for quick response, but there accuracy is not as good as a RTD. Generally speaking, TC can have an accuracy of +/- 3 DegC. If your temperature control is critical I would go with a RTD. An RTD's response is not as quick, but can be very accurate. My .02 I'll look for a standard temp PID loop for you. Hope this helps

[hipoint2 0]

I have always had bad luck with thermocouples being linear. When I redid our boilers I switched them over to RTD's and never looked back. When you do your PID loops make sure you scale your input from 3277 to 16384 and 0 to 16383 and when you setup your PID set your Smin and Smax to your engineering units, then of course you have to scale your control variable coming back out. Hope that helps!

[AutomationWizard 0]

Are you sending an analog signal to your heater or digital? What kind of tollerance do you have on the temperature control?