Thermometer Calibration

[YeastFace]

I have that same thermometer. I think the steam must have got into the display or something as it has faded. I thought it was a dead battery, but changed this and it was the same. I've kept it dry for a few weeks so hopefully the screen had dried out ok. I'm not confident in my Tiger meat thermometer.

 

[Tony1951]

the .8 discrepancy is both at ice and boiling water temp so it seems the thermom is pretty reliable.

Used it today for the first time. The figures are a bit small on it and the buttons are teeny but overall very pleased with it. Much better than my argos meat thermom.

I find that the apparent discrepancy goes away if you only dip the tip of the probe into the fluid you are working with. Mine works best with about 1 - 2 cm in the fluid. If I plunge mine right into the wort - say four inches in, I get a different reading. Maybe they are a bit like most glass thermometers - designed for partial immersion. That's a guess, but you can try different immersion depths and see how it affects the measurement.

 

[MyQul]

I find that the apparent discrepancy goes away if you only dip the tip of the probe into the fluid you are working with. Mine works best with about 1 - 2 cm in the fluid. If I plunge mine right into the wort - say four inches in, I get a different reading. Maybe they are a bit like most glass thermometers - designed for partial immersion. That's a guess, but you can try different immersion depths and see how it affects the measurement.

After your write up on glass thermometer and different immersion depths, I tried different depths too. When calibrating in ice and boiling water like yours 1-2cm seems to be the sweet spot but the best I could get it was 0.8 off 0C and 100C

 

[Tony1951]

After your write up on glass thermometer and different immersion depths, I tried different depths too. When calibrating in ice and boiling water like yours 1-2cm seems to be the sweet spot but the best I could get it was 0.8 off 0C and 100C

Right. It's a few weeks since I was messing about with mine from a calibration point of view and I had the impression I'd got the measure of it. Maybe I should check again, though to be honest, if the thing is 0.8 of a degree off at 100c, that kind of error might be down to the elevation of the site you are working at, or even weather conditions (low/high pressure). I note also the remarks made earlier about water hardness and other factors that may affect the actual boiling and freezing points.

In practice, if my mash is at 68 rather tha 69 degrees when I want a bit of body in my beer, I doubt I will notice. :) - I know you aren't nit-picking and are making interested enquiry into the thermometer so that isn't meant to be dismissive. I'm the same - I like to experiment and test things.

 

[MyQul]

Right. It's a few weeks since I was messing about with mine from a calibration point of view and I had the impression I'd got the measure of it. Maybe I should check again, though to be honest, if the thing is 0.8 of a degree off at 100c, that kind of error might be down to the elevation of the site you are working at, or even weather conditions (low/high pressure). I note also the remarks made earlier about water hardness and other factors that may affect the actual boiling and freezing points.

In practice, if my mash is at 68 rather tha 69 degrees when I want a bit of body in my beer, I doubt I will notice. :) - I know you aren't nit-picking and are making interested enquiry into the thermometer so that isn't meant to be dismissive. I'm the same - I like to experiment and test things.

It's clear your not being dismissive :thumb:. Didn't know water hardness can effect boiling/freezing point btw

 

[Tony1951]

It's clear your not being dismissive :thumb:. Didn't know water hardness can effect boiling/freezing point btw

I hope I am right about that - my understanding is that dissolved materials can affect both. I need to look this up. Perhaps I am mistaken. Not that unusual a situation.

EDIT:

Yes it does. http://chemistry.about.com/od/waterchemistry/f/Does-Hard-Water-Boil-At-A-Higher-Temperature.htm

 

[MyQul]

I hope I am right about that - my understanding is that dissolved materials can affect both. I need to look this up. Perhaps I am mistaken. Not that unusual a situation.

EDIT:

Yes it does. http://chemistry.about.com/od/waterchemistry/f/Does-Hard-Water-Boil-At-A-Higher-Temperature.htm

Thanks for that Tony. May be I should just bite the bullet and buy a thermapen?

 

[Tony1951]

Thanks for that Tony. May be I should just bite the bullet and buy a thermapen?

I reckon the one we both have will do very well. When I mentioned the above matters, I was suggesting that 0.8 of one degree C is probably within the errors introduced by everyday variables like dissolved salts and location altitude that we can't change. I live 70 meters above sea level.... What difference will that make? Just looked it up. At my house water boils at 99.7C :???:
Add onto that my magnesium and calcium levels of 47mg/l and I don't know what will happen....

I doubt a fraction of a degree c deviation on the thermometer will have any impact at all for practical purposes.

 

[MyQul]

I reckon the one we both have will do very well. When I mentioned the above matters, I was suggesting that 0.8 of one degree C is probably within the errors introduced by everyday variables like dissolved salts and location altitude that we can't change. I live 70 meters above sea level.... What difference will that make? Just looked it up. At my house water boils at 99.7C :???:
Add onto that my magnesium and calcium levels of 47mg/l and I don't know what will happen....

I doubt a fraction of a degree c deviation on the thermometer will have any impact at all for practical purposes.

I agree. I was just adjusting for the 0.8 discrepancy any way, seeing as it was the same at both the top end and bottom

 

[McMullan]

After your write up on glass thermometer and different immersion depths, I tried different depths too. When calibrating in ice and boiling water like yours 1-2cm seems to be the sweet spot but the best I could get it was 0.8 off 0C and 100C

Mine has a marker for immersion depth. It's 76mm from the tip.

 

[baggybill]

Was it mispriced originally? It's £12.89 now on the link... or are they pulling a fast one? :wha:

Edit: There's a bunch of similar ones on eBay for ~£3 so, they're at it...

 

[F00b4r]

If you buy a thermapen buy one from ETI's eBay refurbished store as they are £30 from there and mine looked brand new (I actually got it for £24 with a 20% off voucher from eBay).

 

[MyQul]

Was it mispriced originally? It's £12.89 now on the link... or are they pulling a fast one? :wha:

Edit: There's a bunch of similar ones on eBay for ~£3 so, they're at it...

Maybe lots of forumites bought one after Tony51 linked their page and they thought they'd try and pull a fast one when they suddenly got loads of orders.