Are contactless thermometers accurate?
 

We have a digital thermometer that works great but takes forever. I trust it. I see the new contactless ones for less than $17-20 out the door. Use 2 AA batteries so no worries about low battery that isn't in the house. Are they any good?

I use one that I bought on Amazon for $22. It works great.
I have a mercury thermometer in my turtle pond and when I use the 'contactless' one...they are always within a degree or two of being the same.
I like it.

accurate is a relative term.

IR thermometers.. The medical versions seem to have an offset built in (the surface of your forehead is likely lower than what it displays.) The surface type can make a difference.

There is a wikipedia page on the subject. https://en.wikipedia.org/wiki/Infrared_thermometer#Accuracy

I'm happy with this one, seems to jive with my Ryobi IR, plus it will measure forehead:

https://smile.amazon.com/gp/product/B087FZ6R3C/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Accurate enough for most applications.

I have two infrared thermometers. One I use for cooking--mostly to determine if oil is up the the correct temperature. The other I use on kid's foreheads when they're sick. It's great because I don't have to wake them up. It's accurate enough to be able to distinguish between no fever, a mild fever, and needing to head to the ER ASAP (fortunately haven't had to do this).

OK so, I'm looking at one to measure temperature to indicate a fever. I guess I can test it when there is no fever and get a +/- baseline for accuracy. As long as the variance is always the same, I don't care if it is high or low. This way if someone doesn't feel well in the middle of the night we can get a quick and "relatively accurate" reading. I just don't want to take 4 readings and get 4 results that are 5 degrees off of the high and low.
Thanks for the responses.

The one I linked above reads body temp within a few tenths repeatedly, with 3 modes, body temp, room temp, and surface temps.

One note: if the kid is burying their head in the pillow and you take a measurement right away, it will probably be very high. I've found that you have to give it a minute or two first.

We usually switch to an oral thermometer when we get a high reading (102+) and generally find the high temperature is due to the above effect.

so much for that heating pad trick ;)

Also good for find brake drag, or non-operation, if the cat converter is working, if the return coolant hoses are circulating, low exhaust and block temps which can indicate a dead cylinder, drive line components needing lube, insulation and window leaks in houses, etc.

Yep, "relatively" accurate. I picked up a dual-mode one (forehead vs. surface/liquid) that is FDA registered as a medical device. Probably doesn't mean much WRT accuracy, but at least it cost more, lol...

Haha. I didn’t use a heating pad. I used the light bulb clipped to my bed. Most times it would make the thermometer way too high and I’d have to shake it down to a reasonable “fever” that would keep me from going to school.

Yes, sort of...

They the Stefan-Boltzmann law of radiation: Qt=σeAT4 Q t = σ e A T^4
σ = 5.67 × 10−8 J/s · m2
K4 is the Stefan-Boltzmann constant
A is the surface area of the object
T is its absolute temperature in Kelvin

the surface also has an emissivity, which is about 0.94 for everything that is non-metallic (white people have black skin in the IR)

Sources of error are mainly due to the operator, such as using the wrong angle, not compensating for a polished metal (or metallic painted) surface, or pointing the beam at the edge.

For use on humans they will measure the T forehead or whatever, which is not T core and can vary if the person recently exercised (as the forehead is a "thermal window" used for cooling - you can see this effect clearly by backcountry skiing with attractive Scandihoovean women, which makes a xlnt research project)...

Be happy 'cuzin the 1950s USAF had to use 2 semi-trucks to cart the equipment around... Col. James H. Veghte used it to measure surface T of birds, jack rabbit ears, etc.

Just be careful of buying a regular thermometer from Amazon.
I bought one earlier this year and upon opening it....could clearly see that it had been re-packaged because of a return. It wasn't even taped in.

I haven't used it yet. Everytime I see the box that says 'Oral/Rectal Thermometer' I put it back.

Geezer voice:

Way back when I was a kid I had horrible allergies, and I could not breath through my nose any better than breathing through my ears. When I got a temperature and had to go see the doctor they would stick a thermometer in my mouth and then get mad when they saw me breathing with my mouth. I can't hold my breath that long! I often ended up on my belly with a rectal thermometer because my nose was stopped up.

I just dreamed of the day when the thermometers of today would arrive.

End Geezer voice.