Dial thermometer issues

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tedandlea

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I had been using my dial thermometer for some time, and noticed that the boiling wort was always at 206F. So I got a couple new ones. The first gave a boiling point reading of 210F, somewhat better than my original, but when I checked the melting point, it came at 37F. The second new one gave a boiling point of 222F! But its melting point was right at 32F. Since I live only a few hundred feet above sea level, I would expect the true boiling point should be 212F and the melting point 32F.

Now, since I do all grain mashing, the rest temperature is very important (I want it to be 150 to 152F). My question is - Can I trust any of the thermometers at this in-between temperature? Or is there some way to calibrate them?
 

Ichthy

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Go buy a lab thermometer. I don't trust the dial thermos when a couple degree difference matters.
 

BendBrewer

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I just bought one of those Blichmann weldless thermometers and it was dead on nuts.

Compared it to my long stemmed dial therm and it was off by 5 degrees. Tested my cheapo digital thermometer and it was within a degree of the Blichmann.
 

Catt22

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This is completely normal for the bi-metal dial type thermometers. Seriously, I've had nothing but problems with them including a relatively expensive one. I gave up on them entirely and went the digital thermocouple route.
 

Hugh_Jass

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I had been using my dial thermometer for some time, and noticed that the boiling wort was always at 206F. So I got a couple new ones. The first gave a boiling point reading of 210F, somewhat better than my original, but when I checked the melting point, it came at 37F. The second new one gave a boiling point of 222F! But its melting point was right at 32F. Since I live only a few hundred feet above sea level, I would expect the true boiling point should be 212F and the melting point 32F.

Now, since I do all grain mashing, the rest temperature is very important (I want it to be 150 to 152F). My question is - Can I trust any of the thermometers at this in-between temperature? Or is there some way to calibrate them?
There should be a nut on the back side of the dial. Turn the nut, take reading, repeat until it reads 212:mug:
 

Catt22

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There should be a nut on the back side of the dial. Turn the nut, take reading, repeat until it reads 212:mug:
Yes, then do the same at 32F, then go back and do it at 212F, then go back and do it again at 32F...rinse and repeat ad infinitum.
 

zymurgy101

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Yes, then do the same at 32F, then go back and do it at 212F, then go back and do it again at 32F...rinse and repeat ad infinitum.
Doubtful many boil kettle thermometers go to 32F. ;)
 

Mischief_Brewing

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I had nothing but problems with thermometers. Out of 5 thermometers I used during various brews, none of them passed both the freeze and the boil test. I was lucky enough to get a thermapen for my birthday last October and have been nailing mash temps ever since.
 

Bobby_M

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I view installed dial thermometers as a ballparking tool and nothing more. They are generally slow to respond and only measure a small pocket of space in the vessel. I always spot check with an instant read digital before I do anything.
 

redalert

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Don't get me started on thermometers. I have at least 4 of them and all of them give different readings. I've been brewing for 2 years and still have yet to find a reliable one. Even though Thermapens are supposed to be the shiznitz it's hard to justify spending $100 on a thermometer. I just ordered a thermocuple from Ebay for a Craftsman multimiter which gives decent temps.
 

azscoob

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I have one I calibrated to 32° that I use for chilling/pitching and one that is calibrated at 212° that is used for mashing/sparge water. I also spot check with my cheapie digital one.
 

samc

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Thermos can drive you insane. The more you have the crazier it gets. You can be dead on perfect 212/32F and still not be correct @ 152F.

Ultimately I rely on the final product to tell me if I've made the right beer. If so I can assume my thermoprobes are close enough. Trying to calibrate those thermos took years off my life. Spending too much time with this http://www.capgo.com/Resources/Temperature/Thermistor/ThermistorCalc.html is a mind numbing experience.
 

Catt22

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Doubtful many boil kettle thermometers go to 32F. ;)
Actually, the one I have goes down to 0 deg F, but it tops out at only 200 deg F. I use a glass lab thermometer for calibration. The dial thermometer was off as much as 10 deg at times and was not consistent throughout the range. Our home brew club is planning a demonstration where members will bring their thermometers for testing. It will be interesting to see what the variances are. I have a side bet going on the maximum spread between the over and under errors. I think it will be much more than anyone expects. I'll report back with the results, but it may be awhile before we get it together.
 

Catt22

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After experiencing a sudden ~8F difference between my Blichmann dial thermo and my Pyrex MLT thermo yesterday, I decided to get a lab thermometer to make sure everyone was behaving:

http://www.carolina.com/product/equipment+and+supplies/measuring+equipment/thermometers/easy-read+enviro-safe+partial+immersion+thermometer+%28-20+to+110+c%29.do?keyword=745416&sortby=bestMatches&page=1
I'm going to order one of those. I like the easy to read yellow background and the price is very reasonable. I have a cheaper lab thermometer, but it's not a traceable model as is the one you linked.
 

zymurgy101

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Catt,

It will be interesting to see your club's results. Moreover, it will be cool to see which versions of thermos report the most accurate readings at different points.
 

Catt22

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Catt,

It will be interesting to see your club's results. Moreover, it will be cool to see which versions of thermos report the most accurate readings at different points.
Ya know, I'm thinking that there will probably be significant variations even between identical thermometers. My side bet says that the max difference between the over and under errors will exceed 17.5 degrees F. IOW, the difference between the worst case under and the worst case over will exceed 17.5 deg F. I know that's a lot and I just pulled the number out of my ###, but I'm thinking that there will be a few people bringing in really crummy thermometers. Curiously, I also have a cheap $2 glass thermometer that is dead on throughout it's range. I guess even the Chinese get lucky sometimes. :drunk:
 
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