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Thanks for the reply. I really appreciate the help sorting this out.
I understand all you are saying so I'll explain it the way I see it:
- My chamber will not maintain the temperature I set when using the Pill as the temperature source.
- When I set the temperature to 20degC I expect the chamber to adjust it's temperature (heat/cool as required) to keep the internal sensor of the Pill at 20degC. Nothing else should matter.
- My chamber mistakenly keeps the temperature 2 degC higher at 22degC. I have physically watched the chamber heat and cool at the wrong trigger points to maintain this error.
My Pill is accurate (measured).
My chamber runs accurately when run on the NTC sensor (measured and recalibrated)
This 2degC offset happens over an entire 2 week ferment profile. (currently cold crashed set to -2degC and maintaining 0degC).
All of the suggestions so far will only effect the rate at which the temperature achieves it's set equilibrium - not the final temperature which is where I have the problem.
I strongly believe there is a mismatch in the data value given by the Pill to what the chamber processes and acts upon.
Not sure what side the error is on and doesn't mater to me. I was hoping a simple offset option could fix it. (I'm sorry I referred to it as calibrating the Pill to the chamber)
At the end of the day I can create a profile that is 2 degC colder for all steps or run an external NTC in a thermowell but being an experienced design engineer and brewer myself I find work-arounds a bit annoying when things are close to being a great product.
Hello Michael. I think we may have found your device in the database so I am assuming I am looking at the correct data. I suspect that what you have is a sensor differential that is not set at a large enough figure.
The sensor differential is the figure that will limit the difference between the inbuilt wired probe and the pill temperature. This is an important setting as it gives you some redundancy in the system and enables you to use both probes. I believe that what is happening with your fermentation chamber is your sensor differential is too small and you should increase this to 5 or 10C. That way your fridge air temperature can vary to a larger degree and force the chamber to heat/cool like you want it to. At the moment the sensor differential is getting triggered and the cooling is turning off before you hit the set point. I assume this is what is happening but if you can check this and get back to us that would be great.
In addition to this I think you have set your hysteresis to 2C. This is a good setting when you are using the inbuilt temp probe as the air temperature has not much thermal mass so 2C is reasonable. With that said when you are using the large thermal mass of the fermenter and pill inside the fermenter this physical mass of liquid is enough to "buffer" the temperature quite a bit so you can really reduce the hysteresis to 0.1C or 0.2C. This is not really your issue but while I was looking at your data I would say this would help your performance substantially given what you are doing.