# Infrared thermometer readings



## JohnyBGood (May 27, 2011)

After ordering an infrared thermometer, I saw a video proving that readings are taken off of the external glass, not internal water temp. The YouTuber showed how even a fire on the inside of an empty aquarium would not register when the thermometer was directly aimed at it from the outside of the aquarium.

My question is, *how accurate are readings off of external glass*? Are external infrared thermometer readings simply as accurate as adhesive thermometers? Thanks for any insight anyone can shed on this.


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## infolific (Apr 10, 2016)

I like the infrared thermometers, but as you've read they don't work through glass. It's easy to test. Just take a reading of your hand with and without glass in front and you'll see the difference. 

In practice I get a slightly lower reading (a degree or two or three) off of the side glass than if I check through the top without glass. However, my aquariums are in my living space so the room temp isn't anywhere near as cold as a basement fishroom might be.

I haven't used the adhesive thermometers so I can't compare.


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