# How do you calibrate a thermometer?



## daddyzaring

I am going to be investing in some thermometers soon and I have no idea how to calibrate a thermometer?


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## ddave

Get a pot of water boiling and stick the thermo probe in.  The thermometer should read close whatever the boiling point of water is at your altitude.

Some dial thermos have a screw that can be used to adjust the pointer to correct the error if there is any.  Most digital thermos can't be adjusted. 

Here is a web site that will calculate the boiling point at different altitudes.

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

Some people also make an ice slurry (crushed ice in water) and check to see how close it reads to 32°.  Most inexpensive thermos have a "sweet spot range" that they are designed for so they are more accurate in the range that they are meant for like cooking.  And their accuracy or inaccuracy is not linear.  For this reason, I don't bother with calibrating at 32°.

Hope this helps.

Dave


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## chefrob

i've always calibrated my therms (even cheap ones) in ice water and have never had any issues........


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## graybeard

My opinion is this. If you are selecting dial thermometers and they are not adjustable keep looking. I went all digital because I demand accuracy.

beard


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## daddyzaring

How do I find out what my altitude is?


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## ddave

Go to Google and type in your city, state elevation and press enter.

Worked for me.  It will probably give you the elevation according to Wikipedia.

Dave


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## hannibal

Great topic. Can the ET73 be calibrated?


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## daddyzaring

Cool got it.  I found it earlier too, but wasn't 100% sure.  Now I just have to figure out how to use this thermometer. lol
Thank you


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## caveman

It can be checked.  I don't know about calibration.  I think calibrating a digital thermo is just checking the accuracy.  I use boiling water, & if I don't hit that 212° mark, then I know mine is off.  I haven't had a problem with any of my wireless thermo's yet & I checked (calibrated?) them all.  For one of those other "Taylor" like types, where you just stick in the meat, that can be adjusted or calibrated.  Of course, if my information is wrong or off a degree° or so, someone will chime in.


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## daddyzaring

Well I knew I probably can't calibrate my digital, but I just got it today, and wasn't able to figure out how to check it.  Was too tire to mess with it too much. lol


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## bbally

Just calibrate with ice water.  The freezing point does not change with altitude or barometric pressure.


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## south jersey bbq tim

yes..ice water i have aways used..even ones at work for the health inspectors


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## got14u

You can only use ice water if your thermometer goes down that far, some don't. If not boiling water for the win


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## daddyzaring

It's not the temp, I just need to figure out how this thermometer works, so I can check it. lol


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## ozark rt

Wow. Thanks DDave. I've always thought my probes were a couple of degrees off but after checking that website it appears 210° is the boiling point of where I live.


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## chefrob

i guess it takes a trusted authority..............


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## missouri hog wild

BWAAAAA BUY ANOTHER , LOLZ !!!!!!! I RUN 2 DIGITAL THERM ON MY UDS AND MINE BOTH HAVE A RESET BUTTON ON THEM ,


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## dick foster

As the others have said check it at two known points for water freezing or 32F or 0C with an ice bath and boiling 212F or 100C. 

If there is an adjustment set it at boiling water as that is closer to the temp you will be cooking at.

Most thermometers will be withing a couple of degrees and even digital is no guarantee of being spot on accurate but then again for what we're doing it's not that important anyway. 

Digital is just a means of making something easier to read, it doesn't necessarily make it any more accurate. If anything there is more to go wrong and need adjustment in all the circuitry involved with an electronic thermometer. Remember one of the best lab standard thermometers is still a simple mercurial type.

If you have a digital type then the sensor used determines the accuracy more than anything else. For good accuracy you want a platinum type like a PT100 over a thermocouple or PN junction type sensor.

Platinum changes it's resistance with temperature and platinum based sensors are typically more linear in response than the other types.  They also usually cost no more than the other sensor types. 

The PT100 sensor I use in my smoker along with a PID controller, I got for 5 bucks and it has a stainless steel housing. Perfect for the task. I tweaked it at the boiling point a couple of degrees but that was probably due to an offset in the ciricuit instead of the sensor itself.


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## george merrill

great info thx


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