Quote:
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Originally Posted by unregistered
I have an environmental chamber which has an RTD thermostat which will maintain the temp at 22°C
- with a toggle switch I can select 'manual control', and then by means of a pot set the temp manually
- I substituted a 10 turn pot and relocated it, works fine
the problem:
I would like to be able to manually change the set point to something other than 22°, and then have the thermostat maintain that temp
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I don't quite understand the problem. When you use your pot, you ARE changing the set point. Does the thermostat not hold the chamber at that temp? Or is it a matter reproducibly setting various chamber temperatures?
More info on the chamber would be good. What kind of cooling does it have? Pelt? Phase-change? If phase, is the compresser variable speed or does it cycle on/off? What are the connections to the terminals on your schematic?
Anyway, if you really want to control it from LabView, I'd bypass their entire temperature comparator section and feed a logic signal from your virtual PID into optoisolator U4. Maybe even scrap their board entirely.