I have two thermometers - a hambleton bard floating one, and one of those long brewing thermometers with a piece of string attached.
I've always use the floating one, but I was suspicious about it's accuracy - when I've mixed grain to the mash liquor at 72 C, it has come considerably below the desired 66 C - I know a number of factors affect this, but the degree of difference was not negligable.
The thermometer-with-string was given to me with some secondhand stuff. I've just tried both thermometers in a pint glass of hot water, and there is about a 3-4 degree difference between the readings, a difference that could make an important difference to a mash.
Anybody got any good tips for measuring the accuracy of thermometers?
Testing thermometers
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bitter_dave
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moorsd
Not exactly scientific, but I had the same trouble before, albeit not for brewing...but for getting the temp right in aquariums believe it or not!!
Since then I have always measured body temperature (not exact I know..but it does give an indication!) to see how accurate they are, as your body temp should be fairly constant if you are fit and well!?
Don't recommend sticking it up ones rear end mind you (might impart some off flavours in the finished beer
) I either put it under my tongue or under my arm???...brings back memories of trying to pull sickies at school 
Sounds a bit wierd I know....but it was the only way I could think off to test the accuracy of a thermometer and knowing what reading it should actually end up reading :huh:
Hope that helps????
Since then I have always measured body temperature (not exact I know..but it does give an indication!) to see how accurate they are, as your body temp should be fairly constant if you are fit and well!?
Don't recommend sticking it up ones rear end mind you (might impart some off flavours in the finished beer
) I either put it under my tongue or under my arm???...brings back memories of trying to pull sickies at school Sounds a bit wierd I know....but it was the only way I could think off to test the accuracy of a thermometer and knowing what reading it should actually end up reading :huh:
Hope that helps????
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bitter_dave
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moorsd
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bitter_dave
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Cheers guys 
I'm at home, so no one saw me
That explains why I've been having problems getting a high mash temp. Lucky I gave up trying to get 67 C - I could have messed up the mash if I was out by 4 points!
I noticed my hydrometer was out quite a bit the other day as well - I got a free hydrometer as well with the secondhand stuff. When I had a very high persistent final gravity the other day I was suspicious, so tried the secondhand one, and it was spot on the expected 1010 (checked it in water later to make sure it was right).
I think I have been making stonger beers than i thought :stun , and my efficiency must be better than expected as well!
I'm at home, so no one saw me That explains why I've been having problems getting a high mash temp. Lucky I gave up trying to get 67 C - I could have messed up the mash if I was out by 4 points!
I noticed my hydrometer was out quite a bit the other day as well - I got a free hydrometer as well with the secondhand stuff. When I had a very high persistent final gravity the other day I was suspicious, so tried the secondhand one, and it was spot on the expected 1010 (checked it in water later to make sure it was right).
I think I have been making stonger beers than i thought :stun , and my efficiency must be better than expected as well!
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IanRMartin
Don't know if anyone is still interested in this but, wouldn't it be easier to calibarate your thermometers in boiling water!
As long as you arn't to high (Altitude wise) you water is going to boil at 100C every time. Your body might fluctuate by 0.5 to 1.0 depending on your health and some people just run hot or cold!
Using a temperature closer to the temps you are actualy going to measure should make it as acurate as possible givern the equipment.
Ian
As long as you arn't to high (Altitude wise) you water is going to boil at 100C every time. Your body might fluctuate by 0.5 to 1.0 depending on your health and some people just run hot or cold!
Using a temperature closer to the temps you are actualy going to measure should make it as acurate as possible givern the equipment.
Ian
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IanRMartin
QUOTE (jim @ Jun 28 2006, 01:51 PM) As well as calibrating the 100C point a thermometer with boiling water, you can calibrate the 0C point by using a jug of ice water. B)
Good point!
This would be a better calibraton temp for a thermometer monitoring a fermenting bin because again it is closer to the temps it will be measuring.
Ian
Good point!
This would be a better calibraton temp for a thermometer monitoring a fermenting bin because again it is closer to the temps it will be measuring.
Ian
Well, I remember doing the thing with boiling water and ice water and a thermometer in physics at school, though I can't remember if they mentioned anything about air pressure having a significant effect on boiling point. I would have thought that as long as it wasn't extreme you'd be OK.
I do remember reading that you can't make a decent cup of tea on mount Everest, though, because the water boils at too low a temperature!
I do remember reading that you can't make a decent cup of tea on mount Everest, though, because the water boils at too low a temperature!
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Road Runner
QUOTE (andy @ Jun 28 2006, 08:06 PM) QUOTE (jim @ Jun 28 2006, 07:55 PM) I do remember reading that you can't make a decent cup of tea on mount Everest, though, because the water boils at too low a temperature!ÂÂ
Well that's put me right off a summit attempt....
Last time I made a summit attempt on Everest, I took a Thermos with me for the Tea.
Well that's put me right off a summit attempt....
Last time I made a summit attempt on Everest, I took a Thermos with me for the Tea.
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IanRMartin
QUOTE (Daft as a Brush @ Jun 28 2006, 04:50 PM)The ice water is a great idea but boiling point will vary with ambient pressure and how do you determine when the water is actualy boiling, heating it in a pan doesnt ensure uniform temperature so the water near the flame boils first. To the best of my knowlage the body will regulate temperature more acurately even if it's not quite spot on
I see your points Daab,
I did mention in my original post
QUOTE As long as you aren’t too high (Altitude wise)
It would be easy enough to allow for altitude as long as you know your height above sea level (That would be the hardest part to find out). The change for every 1000ft above sea level is a one degree drop in the boiling point. You could even allow for atmospheric changes as long as you have an acurate barometer and the right tables or calculator but these changes would be very small points of a degree!. http://www.biggreenegg.com/boilingPoint.htm
As for the unevenness of a pan of boiling water for calibrating a thermometer you could use a much smaller vessel you could even use a kettle with the switch forced on (Only advisable for a short while) as the kettle boils so vigorously I would have thought it would be uniform temperature.
I just don't like the idea of putting a thermometer somewhere about my person
This is a bit heavy for a Wednesday night Eh
Time for a bottle of Marston's Pedigree to chill out :beer
(Untill i get my first brew underway )
Ian
I see your points Daab,
I did mention in my original post
QUOTE As long as you aren’t too high (Altitude wise)
It would be easy enough to allow for altitude as long as you know your height above sea level (That would be the hardest part to find out). The change for every 1000ft above sea level is a one degree drop in the boiling point. You could even allow for atmospheric changes as long as you have an acurate barometer and the right tables or calculator but these changes would be very small points of a degree!. http://www.biggreenegg.com/boilingPoint.htm
As for the unevenness of a pan of boiling water for calibrating a thermometer you could use a much smaller vessel you could even use a kettle with the switch forced on (Only advisable for a short while) as the kettle boils so vigorously I would have thought it would be uniform temperature.
I just don't like the idea of putting a thermometer somewhere about my person
This is a bit heavy for a Wednesday night Eh
Time for a bottle of Marston's Pedigree to chill out :beer
(Untill i get my first brew underway
)Ian
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IanRMartin
QUOTE (Road Runner @ Jun 28 2006, 08:00 PM)QUOTE (andy @ Jun 28 2006, 08:06 PM) QUOTE (jim @ Jun 28 2006, 07:55 PM) I do remember reading that you can't make a decent cup of tea on mount Everest, though, because the water boils at too low a temperature!ÂÂ
Well that's put me right off a summit attempt....
Last time I made a summit attempt on Everest, I took a Thermos with me for the Tea.
You could keep a vessel of water (or tea if you like) hotter than the boiling point for the altitude as long as it was under sufficient pressure, however as soon as you open it and the pressure drops it would boil away until the temperature dropped below the boiling point for the altitude.
Ian
Well that's put me right off a summit attempt....
Last time I made a summit attempt on Everest, I took a Thermos with me for the Tea.
You could keep a vessel of water (or tea if you like) hotter than the boiling point for the altitude as long as it was under sufficient pressure, however as soon as you open it and the pressure drops it would boil away until the temperature dropped below the boiling point for the altitude.
Ian
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Road Runner