Placement Of Temp Probe = An Anal Nerd's Findings

[sinkas]

Anal Nerd?, wrong forum dude.....

 

[SpillsMostOfIt]

I've always wondered why people measure air temp in the fridge and try to compensate for the actual temp in the fermenter. You are measuring air temp, and air is a bad conductor of heat. The problem with this method is you don't add cold to a body, you take heat away. The atmosphere around the fermenter needs to be COLDER than the temp you want to get down to. Measuring the air temp next to the fermenter will give you a colder air temp, but how this relates to the actual temp of the wort is anyone's guess, considering that fermenting wort is exothermic. It could be warmer than the air temp inside the fridge and you would never know. Opening the fridge to check on your yeasties will only exacerbate this problem.

... etc. I've snipped to conserve your electrons...

I agree with this almost entirely. However, I have my probe measuring the temperature of the air inside the fridge - or a side panel of the cabinet.

You can happily and correctly assert that you want to know the temperature of the beer as it ferments. I won't argue with that.

I will argue that if you put your probe into a vessel of liquid, what you are effectively doing is going into the controller's setup and increasing the hysteresis.

My base position is that none of it matters, unless you want it to. (And there is nothing wrong with that!)

I've come around to the position where I want to know 'a number' at which good beer results for any given set of other numbers (yeast strain, OG, etc.). I tend to use a quite small number of yeast types and try to make my process the same across batches (ignoring the Shepherds Flat Brewery's Continual Improvement Policy). After *cough* 'enough' *cough* experimentation, I know that when I set the temperature controller so that it maintains a temperature of X+/-Y degrees Celsius, the beer turns out the way I think I want. And that is good enough for me.

Good work on the part of the OP. If it helps you get where you're going, even better.

 

[Brewindo]

Please correct me if I am wrong.

I put the temp probe of my digital controller "next to the fementer, within 2" in the air".

Why? Even with the probe in the air, I have noticed that when the fridge cyles "on" and reaches the set point temp (say 18deg), the fridge cuts out. However the temp continues to fall. This is like a sort of thermal acceleration, as the fridge was working to get to a low temp but the controller interviened at 18deg. So the residual cooling effect is continuing to cool the cabinet beyond where the temp is set. Gets down to arround 16.5deg then slowly starts climbing back up.
With this cycling effect, I guess that the resultant average temp of the fermenter would be somewhere between 17 - 17.5deg.

Alternativley, if I was to imerse the probe dirrectly in the fermenter, I would imagine that this would just increase the effect of what I described above. The ambient air temp inside the fridge would get much lower before the "core" of the fermenter was reduced to the desired temp.

Anyone done any testing with this in mind? I'm not a scientist but this is my thinking.

:icon_chickcheers:

 

[mika]

Have noticed this effect as well and it resulted in my fridge with newly included heating source 'bounce'.
I haven't got round to figuring it out yet, so I simply increased the differential temp to solve it for the moment.
Be interesting to know whether having the probe connected to the fermenter would solve this.

 

[Nick JD]

I'd say as long as you can hold temperature within a 3 degrees C range you won't be making beer that tastes any different to that held to within a 0.1C range.

 

[Banshee]

Yesturday after reading yet another where do you place your probe question I got my two digital thermometers out and put one in the wort and the other in placed on the fermenter lid exposed to the air. Both meters are reading 13C. Tempurature outside of the fridge is 40C.
So for me I don't bother placing it in my fermenter as long as it is in a constant surrounding tempurature I dont' give two hoots what the temp of my fermenting wort is as long as it is in a controled enviroment and it tastes good in the end.
Relax and have a homebrew.

 

[Brewindo]

Yesturday after reading yet another where do you place your probe question I got my two digital thermometers out and put one in the wort and the other in placed on the fermenter lid exposed to the air. Both meters are reading 13C. Tempurature outside of the fridge is 40C.
So for me I don't bother placing it in my fermenter as long as it is in a constant surrounding tempurature I dont' give two hoots what the temp of my fermenting wort is as long as it is in a controled enviroment and it tastes good in the end.
Relax and have a homebrew.

Thank you... I will worry no more. Your point is loud and clear. I will leave my probe outside my fermenter and poor a cool one. :kooi:

 

[wessmith]

Try Bluetack to hold the probe on to the fermenter wall. It works a treat.

Wes

 

[argon]

i shove my probe into a piece of retired stubbie holder and tape it to the fermenter, it's just one of the old adflo analogue controllers btw

Dave

Exactly what i do... beers turn out fine... i have found that the air temp it slightly below that of the fermenter. Not sure if this really matters though.

 

[Mutton Chops]

Please correct me if I am wrong.

I put the temp probe of my digital controller "next to the fementer, within 2" in the air".

Why? Even with the probe in the air, I have noticed that when the fridge cyles "on" and reaches the set point temp (say 18deg), the fridge cuts out. However the temp continues to fall. This is like a sort of thermal acceleration, as the fridge was working to get to a low temp but the controller interviened at 18deg. So the residual cooling effect is continuing to cool the cabinet beyond where the temp is set. Gets down to arround 16.5deg then slowly starts climbing back up.
With this cycling effect, I guess that the resultant average temp of the fermenter would be somewhere between 17 - 17.5deg.

Alternativley, if I was to imerse the probe dirrectly in the fermenter, I would imagine that this would just increase the effect of what I described above. The ambient air temp inside the fridge would get much lower before the "core" of the fermenter was reduced to the desired temp.

Anyone done any testing with this in mind? I'm not a scientist but this is my thinking.

:icon_chickcheers:

To control that bounce you would need to start looking at PID control (or if possible adjusting your deadband setting) but I would have thought that with a well insulated fridge On/Off control would be sufficient, or does the fermenation generate that much heat?

Being new to the process I will definitely have temp control down the track and would be interested to know (depending on ambient temps) how hard the old fridge cycles to maintain brewers desired set point using the On/Off control method and what kind of error across the various conditions.

Cheers