Logging the heat load of an heater via LabView

[heinasirkka]

Dear all,

This is probably a simple question for the people here. There is an inline electrical heater for refrigerant, which reaches a set temperature through temperature controlled PID. I actually need to know the heat power input, to be able to know the conditions after the heater. But the PID of this heater of course automatized and goes on and off until it reaches the set temperature. I turned off the PID once, to be able to control the power input on the heater. But it got overheated and caused a lot of problems (not very strategic heater choice, but cannot be replaced since it is very expensive). Now I leave the PID as it is, and I want to log the heat input on a time scale, by means of a power meter.

I'm looking for a way to start counting time when there is power, and stop when it is not (the on and off can happen in seconds scale), then multiply the power with time to find the heat. Then I'd like to display the added heat regularly, say, every 10 seconds. The same thing will be done for logging the heat went out of the system (condenser, heat losses, etc.). By those means I'm willing to control the steady state of the system. I'm trying to use case structures and while loops, but I'm a bit lost.

I'd be happy if you could give me an idea. If you have a comment on my method, I'd be happy to hear it as well.

Regards,

Kaya

[mikeporter]

So you want to monitor the operation of the PID controller, without taking over the responsibility for controlling the temperature yourself. 

So first, make a list of what parameters you want to be able to measure and how they can be measured. (It strike me you might be able to tell a lot by monitoring the process variable that the PID is using.)

Second it sounds like you would benefit from some training in LabVIEW. 

Finally, those things resolved we can start talking about code.

Mike...