Could this be used to measure the fermentation temperature?

I'm looking for a cheap way of measuring the actual temperature inside the fermenter. On Ebay I found an aquarium thermometer:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7741431709&ssPageName=MERC_VIC_ReBay_Pr4_PcY_BIN_IT

I think I should be able to sanitize this with Idophor and use it to measure the temperature inside the fermenter. I only have to find a way of getting the cable out of the fermenter w/o having a leak. Otherwise I would not be able to monitor the escaping CO2.

Any thoughts?

Kai

Looks like it would work to me. Are you using buckets or carboys? If carboys, get one of "Walker's" orange carboy caps with the two tubes...stick an airlock in one, and run the probe through the other one, then cut a slot in the white cap and replace it over the "probe hole" (just had to type that).

BeeGee said:

Looks like it would work to me. Are you using buckets or carboys? If carboys, get one of "Walker's" orange carboy caps with the two tubes...stick an airlock in one, and run the probe through the other one, then cut a slot in the white cap and replace it over the "probe hole" (just had to type that).

Click to expand...

I'm using carboys. I think the proble is to big to fit through the probe hole. But I should be able to cut a shallow notch into a stopper and run the wire through there.

Kai

Yeah, hard to tell from the picture. I've got an indoor/outdoor thermometer with a probe that would fit, but it's more expensive than that one.

One of the things I cannot tell from the picture is, if there are any gaps where germs can escape the sanitizing.

Kai

Do yourself a big favor and don't stick unnecessary stuff into your extremely vulnerable wort. It's hard enough to be sanitary, you don't need to add another thing into the mix to worry about. The stick on thermometers are fine and they are harmless. Ranting.......sorry.

Prosit!

tnlandsailor said:

Do yourself a big favor and don't stick unnecessary stuff into your extremely vulnerable wort. It's hard enough to be sanitary, you don't need to add another thing into the mix to worry about. The stick on thermometers are fine and they are harmless. Ranting.......sorry.

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There is a concern that the stick-on thermometers are not acurate with a strong fermentation. Especially if the carboy is aircooled, due to the fact that glass it a poor conductor of heat. I read somewhere that the difference can be up to 6F which is pretty significant.

I'm not going to put anything into my brew unless I know that I will be save and that there is something to be gained from it.

Kai

i agree with tnlandsailor on this one, i wouldnt muck around with sticking anything, especially plastic, in my wort. stick on thermo's work fine for me, im sure there is some variation in temps but not enough for me to worry about, i would be more worried about introducing bacteria, than i would a couple of degrees, especially for ale yeast which are pretty tolerant.

cgravier said:

than i would a couple of degrees, especially for ale yeast which are pretty tolerant.

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This is the point here, I'm doing lots of lagers which are more sensitive to fermentation temperature. And I don't fully trust the stick on thermometers that much especially when heat is generated inside.

Kai

my theory is that the temp on the inside is the same as the outer edge because during fermentation everything is moving around so much that whats on the inside doesnt stay on the inside and vice versa for whats on the outer edge, or where the beer is acually contacting the thermometer. (i.e. its not a stagnant situation)

but the only lagers i do are ca common types which are not unlike ales as far as temp. goes, that being said my ca commons do come out pretty clean tasting...

cgravier said:

my theory is that the temp on the inside is the same as the outer edge because during fermentation everything is moving around so much that whats on the inside doesnt stay on the inside and vice versa for whats on the outer edge, or where the beer is acually contacting the thermometer. (i.e. its not a stagnant situation)

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Yes, but there is about 1/4" glass between the thermometer and the fermenting beer. The difference of the teperatures on both sides of the glass is dT = Rtherm + Q, Whith Q being the heat generated inside.

I will to a test tonight where I fill a carboy with warm water, place it in an cool environment and monitor the temperature of the inside and the outside.

Kai

Kai said:

Yes, but there is about 1/4" glass between the thermometer and the fermenting beer. The difference of the teperatures on both sides of the glass is dT = Rtherm + Q, Whith Q being the heat generated inside.

I will to a test tonight where I fill a carboy with warm water, place it in an cool environment and monitor the temperature of the inside and the outside.

Kai

Click to expand...

delta t = qrs?

im sure there is a formula to quantify heat being generated by yeast...you just answered that age old question...is it worth the trouble to make lagers...

p.s. good luck...

not trying to hi-jack this thread... but does the temperature on the outside (i rest my thermometer on top of the priming/secondary bucket) vary a lot from the beer fermenting on the inside? my thermometer always says between 65-68 degrees F, and i'm unsure after hearing all of this concern on temps that the beer is fermenting at the same temperature? could this difference in temp (that the meter isn't reading) be a cause for a lack of bubbing after the inital boom of fermentation?

I too have a question. I have a calibrated Atkins Thermocouple thermometer with a probe that can be attached. I was wondering if I could put the probe under the carboy (between the glass and the carpeted floor) and get a relatively acurate temp. Any thoughts? I was thinking that the carpeted floor would work as an insulator and you might be able to get closer to an actual temp reading.

Kai,
Go to Grainger.com and run a search for "capillary thermometer". There may be something there that fits the bill. Just a thought.
Jeff

I just tape the probe to the outside of the fermenter and put a sponge over it for insulation. There is enough circulation in the fermenter to prevent stratification. The R value for the sponge is about 5 times that of the glass.

I ran a test with ice water this evening and the probe was within 1F of the bulk temperature, even without the sponge.

The heat generation by the yeast at 55F isn't much. I've had a couple big ales that ended up in the garage because they were getting too hot, but they started at 75F and just kept going up!

cgravier said:

im sure there is a formula to quantify heat being generated by yeast

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Yes there is a formula that you can use to determine the heat that is generated by the yeast. You will have to measure the CO2 that is produced and can then calculate how much heat needs to be dissipated. Since you can get the Rthemp of the carboy, you can calculate the temperature drop through the glass

cgravier said:

...you just answered that age old question...is it worth the trouble to make lagers...

Click to expand...

It sure is.


The experiment I did last night came back negative though. I filled a carboy with water. After settling, the stick-on thermometer read 77F. The water temperature inside (close to the wall) was also at 77F. The ambient temperature was at 67F. This shows that the temperature drop between the inside and the outside of the carboy is negligible. This is the kind of data I was looking for since I read differently in the literature.

Kai

There's always someone who spoils a good debate by bringing in experimental data!

what about a floating aquarium thermometer? I'm just a newbie though.