Just I want turn on the heater if the temperature is below 0. Attached is the just part of the huge program. In this case the heater is just turn on for while and turn it off even the temperature is below 0C. How can I keep it on, while waiting on this case for 4 hrs. Without waiting period is just working fine. Please let me know you gus need more info. I am using labview 8.2 Thanks for your time

Your loop will run every 100 milliseconds. When the elapsed time is 4 hours, the loop will stop. But while running, the subvi to measure temperature will execute. If the actual temperature goes below 0, the DAQ vi will run, causing your digital outputs to turn on. Is this what you intended? This vi will run for 4 hours then stop. What if your temperature goes below 0 in two hours? Do you want your vi to keep running for another 2 hours? Please give more detail on what you want to do. If this suits your purpose, then the vi is fine like it is. Only one suggestion. If the temperature reading subvi gives an error, you may want to stop your loop. Use unbundle function to get the status from the error out. Wire the status into another OR function and combine it with the other OR to stop the loop.

LabVIEW

TURN ON DIGITAL OUT

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If te temperature goes below for two hrs the digital out should be on, and next two hours wait there for the next cycle.

I am running switch and need to activated every 4 hrs. the chamber is running seperately and the heater needs to be turned on if the temperature is below zero.

Thanks for advise, I will take your suggestion and modify the vi.

Thanks again.

Jey