# Where have all the liquid crystal thermometers gone? **URL:** \ **Category:** Factual Questions\ **Created:** [January 16, 2013, 2:12am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346 "2013-01-16T02:12:39Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [January 16, 2013, 2:12am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/1 "2013-01-16T02:12:39Z")
Not LCD, I’m talking about those thermometers you stick on your forehead and a row of squares change colour, the last square that changes colour indicates the corresponding temperature. I can’t find the body temperature type anymore, even on eBay. They only have those for brewing beer and aquariums. Are they inaccurate? Toxic? ---
**Author:** ![Yorikke](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yorikke/32/4335_2.png) [@Yorikke](https://boards.straightdope.com/u/Yorikke)\ **Post date:** [January 16, 2013, 2:25am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/2 "2013-01-16T02:25:11Z")
The what now? I can imagine the product your describing, but have never heard of it before. Sounds like a good idea! ---
**Author:** ![Pork\_Rind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pork_rind/32/111_2.png) [@Pork\_Rind](https://boards.straightdope.com/u/Pork_Rind)\ **Post date:** [January 16, 2013, 2:45am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/3 "2013-01-16T02:45:07Z")
> [@AaronX](#): > > Not LCD, I’m talking about those thermometers you stick on your forehead and a row of squares change colour, the last square that changes colour indicates the corresponding temperature. I can’t find the body temperature type anymore, even on eBay. They only have those for brewing beer and aquariums. > > Are they inaccurate? Toxic? I think their inaccuracy combined with the arrival of inexpensive battery operated thermometers did them in. I remember having one and my mother determining that my temperature was in the range of 96 to 102. Not really helpful. ---
**Author:** ![Speak\_to\_me\_Maddie](https://avatars.discourse-cdn.com/v4/letter/s/58956e/32.png) [@Speak\_to\_me\_Maddie](https://boards.straightdope.com/u/Speak_to_me_Maddie)\ **Post date:** [January 16, 2013, 2:47am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/4 "2013-01-16T02:47:14Z")
They still use them at the blood donation center I go to. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [January 16, 2013, 2:58am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/5 "2013-01-16T02:58:46Z")
they weren’t accurate enough to be useful for medical use. infrared and thermoelectric because very inexpensive easy, safe and non-germ spreading. ---
**Author:** ![Claude\_Remains](https://avatars.discourse-cdn.com/v4/letter/c/898d66/32.png) [@Claude\_Remains](https://boards.straightdope.com/u/Claude_Remains)\ **Post date:** [January 16, 2013, 2:59am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/6 "2013-01-16T02:59:00Z")
Haven’t seen one in years… Maybe twenty. Used to have one on an Aquarium. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [January 16, 2013, 3:17am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/7 "2013-01-16T03:17:13Z")
They were at Walgreens two weeks ago. Or maybe it was CVS. They’re in “fun” shapes now. [http://www.walgreens.com/store/c/physio-logic-fever-bugz-stick-on-fever-indicator-with-continuous-temperature-monitoring/ID=prod6085552-product](http://www.walgreens.com/store/c/physio-logic-fever-bugz-stick-on-fever-indicator-with-continuous-temperature-monitoring/ID=prod6085552-product) Not this week, though. I blame the flu epidemic. (And they really do suck.) ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [January 16, 2013, 3:23am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/8 "2013-01-16T03:23:31Z")
I’m planning to use one to measure my shower water temperature. The range is the same as body temp range. ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [January 16, 2013, 3:25am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/9 "2013-01-16T03:25:26Z")
♪Long time passing♪ ---
**Author:** ![FuzzyOgre](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@FuzzyOgre](https://boards.straightdope.com/u/FuzzyOgre)\ **Post date:** [January 16, 2013, 3:43am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/10 "2013-01-16T03:43:20Z")
Get yourself one of those laser/infrared thermometers. I love mine to pieces. It is much more precise, measures in a range of hundreds of degrees, and since there is no contact, germs are not spread. I use it for cooking, checking for poorly insulated walls, measuring fevers. You can use it to check your engine temperature or the BBQ. It determined that my oven temperature was lower than the dial indicated. I’ve used it to compare the surface of my deck to the ambient winter temperature… a host of uses. It is also a handy cat toy. ---
**Author:** ![deltasigma](https://avatars.discourse-cdn.com/v4/letter/d/e5b9ba/32.png) [@deltasigma](https://boards.straightdope.com/u/deltasigma)\ **Post date:** [January 16, 2013, 5:13am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/11 "2013-01-16T05:13:08Z")
Your SO can use the back of his/her hand against your forehead to test your temperature. That’s usually pretty accurate and if you’re not too sick can lead to some fun role playing. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [January 16, 2013, 5:16am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/12 "2013-01-16T05:16:53Z")
> [@deltasigma](#): > > Your SO can use the back of his/her hand against your forehead to test your temperature. That’s usually pretty accurate and if you’re not too sick can lead to some fun role playing. Nope. [Even less accurate than these thermometers.](http://www.ncbi.nlm.nih.gov/pubmed/12753634) More fun though, I agree. 😉 ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [January 16, 2013, 7:39am UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/13 "2013-01-16T07:39:30Z")
> [@FuzzyOgre](#): > > Get yourself one of those laser/infrared thermometers. I love mine to pieces. It is much more precise, measures in a range of hundreds of degrees, and since there is no contact, germs are not spread. > > I use it for cooking, checking for poorly insulated walls, measuring fevers. You can use it to check your engine temperature or the BBQ. It determined that my oven temperature was lower than the dial indicated. I’ve used it to compare the surface of my deck to the ambient winter temperature… a host of uses. It is also a handy cat toy. I would, but they’re: [ol] [li]Not waterproof[/li][li]Need batteries[/li][li]At least 10x more expensive[/li][/ol] Speaking of fever, is it possible to sweat and have a fever? I always thought if you can sweat, you don’t have a fever. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [January 16, 2013, 1:36pm UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/14 "2013-01-16T13:36:29Z")
> [@AaronX](#): > > Speaking of fever, is it possible to sweat and have a fever? Yes, common, even. ---
**Author:** ![jacobsta811](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jacobsta811/32/2893_2.png) [@jacobsta811](https://boards.straightdope.com/u/jacobsta811)\ **Post date:** [January 16, 2013, 2:13pm UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/15 "2013-01-16T14:13:36Z")
They still sell them. I just bought one last month. [http://www.amazon.com/gp/product/B000P4YC0A/ref=wms\_ohs\_product](http://www.amazon.com/gp/product/B000P4YC0A/ref=wms_ohs_product) ---
**Author:** ![drewtwo99](https://avatars.discourse-cdn.com/v4/letter/d/d07c76/32.png) [@drewtwo99](https://boards.straightdope.com/u/drewtwo99)\ **Post date:** [January 16, 2013, 3:15pm UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/16 "2013-01-16T15:15:10Z")
Holy crap! I remember seeing one of these types of thermometers on the side of our fish aquarium when I was a wee lad! I haven’t thought about those old things in perhaps 20 years. Crazy. Thanks for asking this question! ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [January 16, 2013, 5:51pm UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/17 "2013-01-16T17:51:17Z")
> [@deltasigma](#): > > Your SO can use the back of his/her hand against your forehead to test your temperature. That’s usually pretty accurate and if you’re not too sick can lead to some fun role playing. That’s not accurate at all. Humans are good at sensing changes in temperature, but humans suck at measuring absolute temperature. The classic way to prove this is to stick one hand in hot water and the other hand in cold water and let them both get used to it. Then stick both hands in lukewarm water. The water will feel warm to one hand and cool to the other, even though both hands are in the exact same water. ---
**Author:** ![ski](https://avatars.discourse-cdn.com/v4/letter/s/bbe5ce/32.png) [@ski](https://boards.straightdope.com/u/ski)\ **Post date:** [January 16, 2013, 5:52pm UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/18 "2013-01-16T17:52:39Z")
I haven’t done this with the “medical” ones, but with the aquarium version, if you go and look at several hanging on the rack at the store, you will see they can vary by several degrees. When I’d buy one, I’d just try to get one that seemed to be in the “middle” of the range of those on the rack - but no idea if that was accurate either. A difference of a few degrees isn’t real critical in most aquariums (at least the type you’re going to buy this type of thermometer for), but when you’re trying to see if someone has a fever, there’s a big difference between 98 and 101, or 101 and 104. So I wouldn’t use one for medical use. ---
**Author:** ![deltasigma](https://avatars.discourse-cdn.com/v4/letter/d/e5b9ba/32.png) [@deltasigma](https://boards.straightdope.com/u/deltasigma)\ **Post date:** [January 16, 2013, 8:27pm UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/19 "2013-01-16T20:27:51Z")
> [@engineer\_comp\_geek](#): > > That’s not accurate at all. Humans are good at sensing changes in temperature, but humans suck at measuring absolute temperature. > > The classic way to prove this is to stick one hand in hot water and the other hand in cold water and let them both get used to it. Then stick both hands in lukewarm water. The water will feel warm to one hand and cool to the other, even though both hands are in the exact same water. This why you need to properly calibrate your SO. 🆒 edit: that’s half the fun. ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [January 16, 2013, 10:43pm UTC](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346/20 "2013-01-16T22:43:00Z")
They were always meant for things like fish tanks or snake aquariums etc. They were briefly marketed as a very cheap, seemingly ‘high-tech’ (because of its faux-digital readout) fever thermometer in places like the impulse-buy sections of drug stores. But as others have said they are useless for reading human body temp. They aren’t accurate to much more than five or ten degrees and a fever temp needs to be accurate to around half a degree to be of much use. [Here’s exactly what you need on Amazon,](http://www.amazon.com/Digital-Shower-Thermometer-Temperature-Display/dp/B004T34LW2) though it’s thirty dollars… [Next page](https://boards.straightdope.com/t/where-have-all-the-liquid-crystal-thermometers-gone/647346.md?page=2)