Should I re-calibrate my Thermapen?

[CindyJ]

When I stick it into a pot of boiling water it reads 211.2 - 211.3. How precise should I expect it to be?

[jljohn]

I just got a thermapen, and the literature that came with it recommended against relying a boiling water test for calibration purposes. It is too variable. They recommend using an ice bath test at 32 degrees to check the calibration on your thermometer. I'd do that before deciding anything, and if a proper ice bath yields a reading within a few tenths of 32.0, I'd leave it alone.

[jaybls]

Hi Cindy -

SBP is right when they say that there are several factors that affect the boiling point of water (barometer, air pressure, altitude, etc.). ThermoWorks has a link that allows you to find out the boiling point of water in your area. You'll find it here: http://thermoworks.com/software/bpcal....

I would also recommend checking the temp in an ice bath. When done correctly, it will also be a great indication of calibration.

Jaybls

[CindyJ]

Amazing!!!! According to the ThermoWorks Boiling Point Calculator, in my city, water currently boils at 211.2 degrees. I'm in awe!!!

[kaleokahu]

Hi, Cidy:

That's pretty nifty, isn't it. What altitude are you?

Aloha,
Kaleo

[CindyJ]

I don't recall precisely, but not all that high -- somewhere around 350 feet. I also plugged in the barometric pressure at the time.

[kaleokahu]

Hi, Cindy:

A little difference in altitude and/or barometer can make a significant difference. When I run seal level versus 350 feet altitude at 30 inches of mercury, I just got 212.15 (sea level) and 211.73F at 350', or a 0.42F difference. Reduce the barometer by half an inch of mercury, and you get 211.32 at sea level and 210.91 at 350'.

I think your Thermapen is close enough.

Aloha,
Kaleo

[kaleokahu]

Hi, Cindy:

I would leave it alone, unless you bought the thing just to measure your own tap water reaching a boil. Chances are, it's more accurate than you think--tap water usually has enough salts and metals to slightly affect a boil.

212F is for pure water. Try testing your 'pen on a pot of boiling *distilled* water.

Aloha,
Kaleo

[scubadoo97]

Mine reads 212 and we are at sea level

[kaleokahu]

Hi, scubadoo:

That's great. You drawing your water from the same tap as the OP?

Aloha,
Kaleo

[scubadoo97]

No but it was filtered tap

[sbp]

It's probably 100% accurate. The boiling point of water depends on air pressure, too. Different at sea level than at the top of Mt. Everest.