3 extremely accurate thermometers and how they work

We’ve come a long way since mercury.
iHealth thermometer
It's not quite as accurate as a mouth reading, but it's a lot quicker and doesn't require contact. iHealth

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This story originally appeared in the Heat issue of Popular Science. Current subscribers can access the whole digital edition here, or click here to subscribe.

Mercury encapsulated in glass tubes has been reliably reading temperatures since the early 18th century. Modern instruments use various methods to make checkups simpler, more accurate, and a lot less likely to poison you when they break. Here’s how they work.  

Liquid Metal

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