PID in labview

[labviewer]

I plan to control the temperature of a pressure vessel
using electrical heater.

I intend to measure the temeprature using thermocouple
and read this voltage signal into computer
through data acquisiton board. Then comparing this
temperature value to set points temperature , and then
generate an corresponding analog out signal (using PID
control) to control the power of the electrical heater
to realize the set points temperature. I intend to use NI-6030E DAQ. Can I use labview vi (without PID toolset in my labview software) to achieve my purpose?

thanks

[Labviewguru]

I will give my canned answer to this:

LabVIEW is a programming language. Anything is possible.

I created, a long time ago, a simple PID loop to control a heater, also without the PID control toolkit. I don't see you having a problem doing this as well.

Good luck

[Enrique]

Of course you can!

You just need to keep in mind that designing your controller is just to come up with one or several equations. Let say you are going to design a proportional controller for your system: in its simplest form, at the end you just need to find out a constant number.

Make sure you understand which parts of your system that are going to be done by the computer. The best way to do that is to draw your block diagram, breaking each block as much as possible depending on the necesary parts: the knob to set the temperature, the D/A and D/A converters, etc. You should be able to draw a circle enclosing the computer side from the external side. Once you do that and understand how is your system, the rest is almost mechanical...

... until you get t
o the implementation. Keep in mind that the real thing will behave sligthly different than your mathematical models, and you need to "tweak" your system a little to obtain the best performance. For example, maybe you are heating a rod or something that you assumed for simplicity that is perfectly homogenous. Chances are it is not and the temperature gradient and distribution will not exactly follow your model.

This is a high-level answer and I am pretty you will get more answers and commentaries. Now, about how to do it...

Regards;
Enrique

[Hans-Joachim Schulpin]

Maybe you should have a look at http://www.ni.com/support/ and search
the examples for PID.

Best regards
Hans-Joachim

[markwysong]

Your best bet is to check the resource code here on NI's website. If you do a search on PID, you'll find several examples of PID code that you can use without the PID toolset. They should suit your purposes just fine.

Mark