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Thermometers Driving Me Insane!!
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Ben 2 World
(ben2world) - MLife

Locale: So Cal
Thermometers Driving Me Insane!! on 06/19/2010 14:06:32 MDT Print View

I recently bought a HighGear Alterra watch and I just compared its temp reading against 5 other thermometers around the house. I placed all of them close together on a table top inside the house and took a reading after 15 minutes:

HighGear Adventure - 66.7F

No name "spring mechanism" thermometer - 68F

Coleman mercury - 68F

No name whistle compass mercury thermometer - 70F

Seiko digital thermometer - 71.6F

HighGear Alterra watch - 72.9F

Sigh... The two HighGear digital thermometers recorded both the highest and the lowest temps. Maybe they should rename their brand "HighLowGear"?

Edited by ben2world on 06/19/2010 14:12:48 MDT.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Thermometers Driving Me Insane!! on 06/19/2010 14:23:15 MDT Print View

It sounds like a simple calibration problem. Too bad the user is not allowed to calibrate most of them. I don't think that mechanical spring thermometers are very accurate.

Watches are particularly odd. They expect to be mounted on your wrist, so they expect a warm body surface on the backside. One would hope that the thermistor/transducer is on the top.

---B.G.---

Ben 2 World
(ben2world) - MLife

Locale: So Cal
Re: Re: Thermometers Driving Me Insane!! on 06/19/2010 14:26:19 MDT Print View

Hi Bob:

Yeah, too bad one can calibrate altimeters and compasses but not thermometers.

Not 100% correct, but part of me would feel somewhat more confident if the Alterra read somewhere in the middle rather than at the extreme.

Also, there's a part of me that thinks the el cheapo mercury ones might actually be more accurate than the fancier and more expensive digitals. Digitals also require a lot more time to "settle down" on a reading -- 10-15 minutes per HighGear instructions.

James Lantz
(jameslantz) - F

Locale: North Georgia
thermometer insanity on 06/19/2010 14:28:25 MDT Print View

Benjamin,
I have a Highgear watch but can't remember the model. My thermostat in my home is at 76F. The Highgear reads 74.8, my new Timex Expedition WS4 reads 76.3. I chose the carabiner style on the Timex to keep it on my pack away from my body, because I found if I wore the device on my wrist, my sweat would interfere with the sensor port & give wacky altitude, barometer, & temp readings.

Edited by jameslantz on 06/19/2010 14:30:05 MDT.

Ben 2 World
(ben2world) - MLife

Locale: So Cal
Re: thermometer insanity on 06/19/2010 14:37:09 MDT Print View

Methinks ±1 or 2° is pretty acceptable for gadgets. But 6° is a bit much. Sigh...

Mary D
(hikinggranny) - MLife

Locale: Gateway to Columbia River Gorge
Thermometers Driving Me Insane! on 06/19/2010 14:58:30 MDT Print View

If there's a truly accurate thermometer outside of a physics/chemistry lab, I haven't found it yet! That's why I haven't bothered to look for one of those fancy watches--I wouldn't want to test its accuracy by putting it in boiling water!

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Thermometers Driving Me Insane! on 06/19/2010 15:08:47 MDT Print View

Well, there are some fairly accurate thermometers outside of a physics/chemistry lab, but that doesn't make them cheap or UL.

Most of the modern temperature sensors on modern consumer products are purely solid-state, and most rely on circulating air around the chip. If they are small, then they tend to react quicker. If they are large and mounted on a heat sink, they will be very slow to react.

You can start to calibrate some sensors by dipping them into a 50-50 mixture of water and ice chips at sea level, and then dipping them into boiling water at sea level. That is not totally accurate, but it will get you into the ballpark. Most semiconductor sensors are non-linear, meaning that they might be accurate for the first two points mentioned, but they might be way off in the middle. That is why most such sensors have linearity correction built in with a software "look-up" table. Then they can be amazingly accurate.

--B.G.--

Ben 2 World
(ben2world) - MLife

Locale: So Cal
Re: Thermometers Driving Me Insane!! on 06/19/2010 17:40:03 MDT Print View

HighGear Alterra watch going back to Campsavers on Monday. Not a bad watch at all and quite intuitive actually, but just too many features that I don't need.

I'll stick with the simple. Mercury never lies, right? :)

John Nausieda
(Meander) - MLife

Locale: PNW
Pretty true on 06/19/2010 17:43:57 MDT Print View

Good for you. I don't trust most digital watches. I use a little compass and thermometer -plastic that fit over a watchband . Bought both in Beijing. They work. I think Brunton? makes a compass thermometer combo which is very small and light.

Edited by Meander on 06/19/2010 18:17:25 MDT.

Ben Crowell
(bcrowell) - F

Locale: Southern California
Re: Re: Thermometers Driving Me Insane! on 06/19/2010 17:52:58 MDT Print View

B.G. wrote: "You can start to calibrate some sensors by dipping them into a 50-50 mixture of water and ice chips at sea level, and then dipping them into boiling water at sea level."
It doesn't have to be a 50-50 mixture of water and ice, it has to be a water-ice mixture that's in equilibrium. What matters is the equilibrium, not the proportions. Likewise with the boiling water: a pot of boiling water will not actually be at 100 C unless it's in equilibrium with its own vapor. If he just does this casually in the kitchen, he'll have no way of ensuring equilibrium, and he won't be likely to get any better accuracy than the accuracy he's already achieving.

Benjamin...for backpacking purposes, does this matter?

Franco Darioli
(Franco) - M

Locale: Melbourne
Thermometers Driving Me Insane!! on 06/19/2010 19:24:27 MDT Print View

A man with one watch always knows the time
A man that has two , he is not so sure.
temperature

My Casio and my cheapo kitchen spirit thermometer agree most of the time.
Note that according to the barometric pressure, if I stay inside I will be dry.
Franco
The first pi was not that clear...
neither is this , but the spirit is on 20c.

Edited by Franco on 06/19/2010 19:29:35 MDT.

Dale Wambaugh
(dwambaugh) - MLife

Locale: Pacific Northwest
Re: Thermometers Driving Me Insane!! on 06/19/2010 21:44:16 MDT Print View

I bought one like the one shown in the link:

http://www.novatech-usa.com/Products/Min-Max-Thermometers/4050

Note the accuracy listed for a given range of temps. This type of thermometer is sold for food service, refrigeration, etc. They are small and light and have a high/low feature that hikers may like for determining lowest nighttime temps.

Many years ago, when I was doing photographic work, I had a Kodak Process thermometer that used mercury, was about a foot long and was accurate to about 1/8 degree Fahrenheit. IIRC, it cost about $100 in the mid-1970's.

In photography school we had 25 people in the program and were able to compare a couple dozen thermometers at the same time. Conclusion: cheap thermometers vary a lot.

All said and done, thermometers tell you what you already know and are probably most helpful when it is REALLY cold. Other than that, it is more a matter of curiosity and personal record-keeping. If you are doing gear testing, I think humidity should be accurately recorded too.

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
humidor thermometers on 06/19/2010 22:01:04 MDT Print View

To record hi/lo temp and humidity, an inexpensive electronic humidor thermometer works well:
link to amazon

Edited by erdferkel on 06/19/2010 22:03:15 MDT.

Heath Pitts
(heathpitts)

Locale: Nashville
Humidor on 06/20/2010 09:11:29 MDT Print View

Tohru, how much does that thermometer weigh?

Edited by heathpitts on 06/20/2010 09:13:37 MDT.

Tohru Ohnuki
(erdferkel) - F

Locale: S. California
Re: Humidor on 06/20/2010 14:10:10 MDT Print View

I don't have that exact model, but one that is very similar. Mine weighs less than an ounce..

Heath Pitts
(heathpitts)

Locale: Nashville
Weight on 06/20/2010 15:22:12 MDT Print View

Great This may find a place in my pack. I guess the only downside is the temp range stopping at 32f

Edited by heathpitts on 06/20/2010 15:54:54 MDT.

James D Buch
(rocketman) - F

Locale: Midwest
Aristotelian/Pseudoscientist and Temperature on 06/20/2010 19:24:59 MDT Print View

I had a friend with an ABD PhD -- meaning "All but Dissertation" - the classes but not the independent research and writing.

I called him Aristotelian because he was one who preferred to believe that the only way to really learn things was by thinking - no dirty little experimentation need be tolerated.

Pseudoscientific was added because in nearly 10 years of education, the only science class taken was meteorology which was taught with only high school algebra as a needed mathematical background. So, his lab experience was pretty much zero as well.

The fact that two banks a few blocks apart could report temperatures 10*F different was difficult for him to accept. His major experience with temperature was the furnace controller on the wall and the outdoor temperature sensor in his Subaru. His attempts to learn to cook were all dismal failures.

One day he bought a thermometer, probably electronic. I never saw it. It was a hot summer day. The temperature outside the car was consistent with the temperature on the radio.

He left the car sitting in the sun and came back an hour later. He started measuring the temperature at different places in the car and was astonished that the temperature varied widely all over the place. Up to 130*F in places and down to only 90*F in other places.

He had no idea that temperature was so hard to "measure".

He could never understand why I would gather the indoor and outdoor electronic sensors together in one spot in the house and let them all come to stable temperatures and record the results on each of the units.

As a rule, all of the temperatures of the 3 outdoor sensors and the 5 indoor sensor units were within +/-1*F, with most of the differences being only a few tenths of a degree. Everything was a LaCrosse branded product.

It was too hard to read the cheap glass thermometers to that accuracy, so I simply ignored them and still do. There is always a digital around to glance at.

I have a HighTech "wonder watch/altimeter/barometer/compass/stopwatch.... and usually never remember to even glance at the temperature indicated upon it because it is such a pain to get it to reach a stable off the wrist temperature. If I ever did pay attention to it, it would be treated as a not very reliable instrument.

However, when I have worn it in the hot tub at the YMCA, it does appear to indicate the water temperature pretty accurately - when there is someone around to measure the hot tub temperature, that is.

The beginning post of this thread tells me that somebody suddenly got an experimental exposure that was shocking to inner beliefs about temperature measurement being easy.

Mixing up different thermometer types and brands. Almost as bad as old style sleeping bag temperature ratings.

Ben 2 World
(ben2world) - MLife

Locale: So Cal
Re: Aristotelian/Pseudoscientist and Temperature on 06/20/2010 20:08:51 MDT Print View

Actually, Rocketman...

I placed all six thermometers close together -- in a room away from any sunlight and with the windows closed -- and waited 15 minutes before taking the readings.

Edited by ben2world on 06/22/2010 12:27:17 MDT.

Ben Crowell
(bcrowell) - F

Locale: Southern California
Re: Aristotelian/Pseudoscientist and Temperature on 06/20/2010 20:20:13 MDT Print View

"Mixing up different thermometer types and brands. Almost as bad as old style sleeping bag temperature ratings."
There's nothing wrong with expecting different types and brands of thermometers to read the same when they're exposed to the same air, sitting on the top of the same table. The differences among them do indicate systematic and/or random errors. Not sure what the point of the long story was supposed to be.

Franco Darioli
(Franco) - M

Locale: Melbourne
Thermometers Driving Me Insane!! on 06/20/2010 20:31:18 MDT Print View

"Not sure what the point of the long story was supposed to be."

Same here...
Franco