Proportional Temperature Controller

[Mike7]

I am currently doing some LabVIEW programing for a project, and I am
interested in creating a VI that will control the temperature in a
solution (using an offboard device).

It is important that this VI would regulate the temperature
proportionately, that is, that the amount of energy expended by the
device is a funtion of the ratio of the current temperature to the
desired temperature.

A professor noted that he has seen VIs that control temperature by
using a sensor that measures if the difference between the current
temp and desired temp is positive or negative. The VI then sends a
signal to a temperature controlling device that then responds with a
fixed amount of heat or cooling. This method is highly inaccurate and
tends to re
sult in overkill, one way or the other.

If anyone has some insights or examples of some proportional
temperature controlling VIs, I would truly like to see them and hear
from you.

Any help will be much appreciated.

Thanks!
- Mike

[MattBradley]

Mike,

Without getting into too much control theory, the professor is right. You will see a lot of overshoot and oscillation with a proportional controller. To avoid this problem, you would need either a very slow heater or a PID controller (although you might be able to get by with a PI controller).

So I guess the question is if you can use a PID controller.

[Helmut Hullen]

Hallo, Mike7,

Du (kleinm) meintest am 29.05.02:

> I am currently doing some LabVIEW programing for a project, and I
> am interested in creating a VI that will control the temperature in
> a solution (using an offboard device).

> It is important that this VI would regulate the temperature
> proportionately,

What about a kind of
if abs(dt) > maxdt then let P = pmax * sign(dt)
else
if abs(dt) < mindt then donothing
else let P = factor * dt

May be that you have to implement some time loops too.

Greetings!
Helmut

Please excuse my gerlish!

[Randy_H]

Mike,

I would suggest looking into the PID Toolset.
I would also suggest searching the following results:
Keyword Search: temperature control.

Randy Hoskin
Applications Engineer
National Instruments
http://www.ni.com/ask

Message Edited by Molly K on 02-18-2005 11:30 PM

[lvnoob]

hey hows your project so far?
i am doing the same thing as you are and i really have no idea on how to start it.
if you can help me on some basic things, i would be very gratefull 🙂

thnx

kleinm@bethelks.edu (Mike7) wrote in message news:<4b5c650a.0205291147.405bc418@posting.google.com>...
> I am currently doing some LabVIEW programing for a project, and I am
> interested in creating a VI that will control the temperature in a
> solution (using an offboard device).
>
> It is important that this VI would regulate the temperature
> proportionately, that is, that the amount of energy expended by the
> device is a funtion of the ratio of the current temperature to the
> desired temperature.
>
> A professor noted that he has seen VIs that control temperature by
> using
a sensor that measures if the difference between the current
> temp and desired temp is positive or negative. The VI then sends a
> signal to a temperature controlling device that then responds with a
> fixed amount of heat or cooling. This method is highly inaccurate and
> tends to result in overkill, one way or the other.
>
> If anyone has some insights or examples of some proportional
> temperature controlling VIs, I would truly like to see them and hear
> from you.
>
> Any help will be much appreciated.
>
> Thanks!
> - Mike