Proper use of Temperature Probe

[Tidwellc]

I recently built an arduino temperature controller for my fermentation chamber, and am using a PT100 RTD as a temperature probe. It's responsive and it works well. But now I'm starting to question if I can improve it.

I currently have a stainless steel thermowell installed in my fermenter lid that drops down to about dead-center of 5 gallons of wort. I've just been dropping the RTD all the way in and running with that. I'm concerned that the cold air being circulated is just falling down into the thermowell, and the probe is just seeing the temperature of that air which may not accurately reflect the actual temperature of the wort.

I've thought about putting some mineral oil in the thermowell to submerse the probe and maybe better conduct the temperature of the surrounding liquid, and stuff a bit of paper towel or something in the opening so as to help insulate it. My concern there is that it would be too difficult to clean afterwards. Maybe just water?

Anyone have any thoughts or experience with this?

Thanks in advance!

 

[GilSwillBasementBrews]

Maybe try filling the hole with thermal grease??

 

[cfrazier77]

You could put a stopper in the top, or a little water added to the tube.

 

[Tidwellc]

Maybe try filling the hole with thermal grease??

Just like the mineral oil, I'm kinda scared that would be a nightmare to keep clean. The thermowell seats very well in the lid, but there's really no easy way to take it out without ruining the grommet.

You could put a stopper in the top, or a little water added to the tube.

That's what I was kinda thinking, maybe both.

 

[Golddiggie]

I just use small silicone stoppers in the tops of my thermowells. This closes them up about as much as possible. With the sensor at the bottom of the thermowell, and it surrounded by whatever is fermenting, I figure whatever little amount of other temperature air can get to it, would be minor. IF I really was concerned, I could do something else to seal it up. But it's not something I'm overly worried about.

I use an Inkbird sensor for the thermowell. It's not what controls the chamber for it's temperature. I'm more interested in maintaining the temperature of the air around the vessel than the beer inside it. Since I consider it 'normal' for the fermenting beer/other to be above chamber ambient temperature while active. Once it's done, it will drop to ambient (a sign things are ready). I set the chamber to no higher than the middle of the range for the yeast (for temperature). It's worked out well since I built the chamber. Now that it's no longer summer out, the basement room I ferment in has returned to the temperatures I expected. These also work for my batches as a good environment temperature. At most, I'll use the chamber to contain the fermenting vessel and allow it to get warmer. Once done, I'll probably open the lid to let cooler air enter.