ir thermometer

[cglochau]

I just purchased a new ir thermometer and its about 4 deg different than my old one. What would be the best way to determine accuracy?

[Scott Patterson]

I just purchased a new ir thermometer and its about 4 deg different than my old one. What would be the best way to determine accuracy?

Well first I would use an electronic digital thermometer in a glass of cold water with ice in it. Get your reading and then shoot the water with the IR thermometer. Be sure that you shoot the water and not the glass! Remember that IR's read the surface temp and not the air temp.

[Bruce Breedlove]

I agree with Scott but I would go one step further. Place electrical tape or blue masking tape on the glass where you take the temperature reading. Glass has very low emissivity but electrical tape and blue masking tape both have an e of about 0.95 which is probably what your IR thermometer is set at. (If you try to read the temperature of a material with a very low e your measurement can be way off.)

Also allow the ice to cool the water as low as it will go and allow the glass and tape to cool down.

[Matt Fellman]

Just to be sure... would it still work with Wild Turkey in the glass? :)

When I worked in kitchens years ago we'd always calibrate thermometers using a glass of ice water..... very heavy on the ice.

Then we'd dump out the water, fill with whiskey, drink and go to work :)

[Bruce Breedlove]

Matt,

If I remember my college chemistry correctly the ice will melt at a lower temperature in the antifreeze - I mean alcohol.

[cglochau]

The ice water and tape worked perfect Thanks

[Ross Neag]

Does your thermometer have emissivity settings? Really good ones do, like the Fluke 561. I've had it for 3+ years and its awesome. Don't forget to check the 'throw' or spot size sensor of your new thermometer--it may have a larger temp surface area at 5', 12' etc than your old one.

[jamie wilks]

Just a couple of thoughts.
Has either of the thermometers been recently calibrated? One or both could not be accurately displaying the temperature.
I use an IR thermometer as well. In my opinion a thermomter is used to measure temperature differentials. If the thermometers measure the differences properly, but do not match or correlate to each other, does it really matter?
I guess I'm talking about accuracy, precision and how they relate to temperature differences or differentials.

[Bruce Breedlove]

Jamie,

The reason to shoot the tape on a glass of ice water is to measure a known temperature, in this case 32 degrees F. That is a simple check to see if the IR thermometer is calibrated properly. Similarly you could shoot tape on the side of a pot of boiling water (212 degrees F at sea level).