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# Calibrating the digital thermometer, is 212*F an accurate measure of boiling water

So I've read a few threads here on calibrating digital Thermometers using the 212* boiling point of water as an accurate gauge. The boiling point of water is 100°C or 212° F at 1 atmosphere of pressure (sea level). So even at sea level there will be a corrected temp depending on the barometric pressure. I don't want to bore anyone with the formula and all the other mombo jombo that goes with it. There is an online calculator one can use. You need to know your altitude and the barometric pressure. I have a home weather station that gives me all the info. If you do not you can use a gps to get elevation, or if you have an airport nearby you should be able to get elevation and the barometric pressure from their website.

For example the altitude where I live is 3640 and today's barometric pressure is 26.79 inches HG. the boiling point for water today is 205.46

My digital therm read 199 today in boiling water. Six degrees off, which is where it's been since the day I've owned it. I periodically test it just to make sure.

Here's a link to the online calculator:

http://www.csgnetwork.com/h2oboilcalc.html

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That'll work, but, unfortunately, the accuracy of thermometers isn't always linear, especially digital thermometers.
So, a thermometer could be dead on at 212 degrees, but, off at, say,145.

It's best to get a high-quality calibrated NIST thermometer for comparison, and check at several temperatures.

~Martin
Quote:
Originally Posted by DiggingDogFarm

That'll work, but, unfortunately, the accuracy of thermometers isn't always linear, especially digital thermometers.
So, a thermometer could be dead on at 212 degrees, but, off at, say,145.
It's best to get a high-quality calibrated NIST thermometer for comparison, and check at several temperatures.
~Martin

Martin,

That is correct. I just wanted to post this to add to the information in the threads that say to calibrate to 212*. Which isn't accurate for all locations.

Along the lines of the NIST therms I have a Maverick PT-100 Por-temp NISt/NSF, that I have been very happy with.

Not to get into the scientifics here, but this might be of help to some:

http://whatscookingamerica.net/boilpoint.htm

As to the finer details, I don't do the kind of stuff that requires great precision.

Good luck and good smoking.

BUMP, great thread ! Deserves it IMHO ! Folks asking about temps, Temps being off on the boiling point ! Your temps may not be off as much as ya think !

Here ya go !

Thanks Justin! Now I want to see some TBS coming out of your new Mini-WSM!
Quote:
Originally Posted by dirtsailor2003

Thanks Justin! Now I want to see some TBS coming out of your new Mini-WSM!

Well deserved Case ! This will clear up a lot of confusion for folks & IMHO should be bumped often !

Now here ya go !

Was planning on ribs last nite, don't get me started on that ! Lol

http://www.smokingmeatforums.com/t/176809/first-mini-smoke
Quote:
Originally Posted by dirtsailor2003

So I've read a few threads here on calibrating digital Thermometers using the 212* boiling point of water as an accurate gauge. The boiling point of water is 100°C or 212° F at 1 atmosphere of pressure (sea level). So even at sea level there will be a corrected temp depending on the barometric pressure. I don't want to bore anyone with the formula and all the other mombo jombo that goes with it. There is an online calculator one can use. You need to know your altitude and the barometric pressure. I have a home weather station that gives me all the info. If you do not you can use a gps to get elevation, or if you have an airport nearby you should be able to get elevation and the barometric pressure from their website.

For example the altitude where I live is 3640 and today's barometric pressure is 26.79 inches HG. the boiling point for water today is 205.46
My digital therm read 199 today in boiling water. Six degrees off, which is where it's been since the day I've owned it. I periodically test it just to make sure.

Here's a link to the online calculator:

http://www.csgnetwork.com/h2oboilcalc.html

Really great thread, missed this in my research.
Although this only changed my initial findings by a degree and a half....... that's a degree and a half !!!!
Here's my math math-i-ticle figure eq-at-tion, Baro is 29.67 tonight..... yep it's raining
Altit is 4498
Edited by Miersc77 - 4/9/15 at 11:59am

I know this is from awhile ago but I just came across it and was checking out the calculator. When I run it based on pressure I get one result and when I run it based on elevation I get a different result. Which would be more accurate, elevation which doesn't change or pressure which does? Thanks

**edit** I should have read further  says right on the website that, "It should be noted that the only actual factor that is truly involved in the variance of boiling water is the pressure. Altitude is given as an alternative where and when pressure information is not available."

Just a bump, been lots of people posting about inaccurate therms lately.

There have been many discussions about how to calibrate using freezing and boiling water. While people usually post about the corrections needed when boiling water at elevations above sea level, there are other factors to consider as well. Here is a link to my old post about these other factors:

The science of the freezing and boiling point of water

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