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Old February 4th 18, 04:51 PM posted to alt.home.repair
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Default Thermometers: What's the Problem with Accuracy?

I've been trying to buy four refrigerator/freezer thermometers and it's
frustrating how inaccurate/inconsistent they are.

For Instance:

- 4 thermometers of same make/model, hanging on the same rack.

- Alcohol bulb/glass tube - you'd think basic physics...

- Each reads a different temp from 68 to 74 degrees.

Only thing I can think of is that the card behind the glass thingie is
misaligned, but looking at these things, there does not seem to be enough
physical room for those kinds of errors.

Also, at home I have a couple of digital indoor/outdoor thermometers.

Bring the outdoor sensor inside and put it right next to the master part, and
they're a couple degrees different.

Is there any hope at all of finding four thermometers which:

- All read the same temp when placed side-by-side
- Read the correct temp.

What am I missing?
--
Pete Cresswell

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Old February 4th 18, 05:11 PM posted to alt.home.repair
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Default Thermometers: What's the Problem with Accuracy?

On Sun, 04 Feb 2018 11:51:08 -0500, "(PeteCresswell)"
wrote:

I've been trying to buy four refrigerator/freezer thermometers and it's
frustrating how inaccurate/inconsistent they are.




http://www.leevalley.com/us/garden/P...=2,40733,40734


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Old February 4th 18, 05:46 PM posted to alt.home.repair
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Default Thermometers: What's the Problem with Accuracy?

On 2/4/2018 11:11 AM, wrote:
On Sun, 04 Feb 2018 11:51:08 -0500, "(PeteCresswell)"
wrote:

I've been trying to buy four refrigerator/freezer thermometers and it's
frustrating how inaccurate/inconsistent they are.




http://www.leevalley.com/us/garden/P...=2,40733,40734

Looks nice but no spec's on absolute accuracy so no way to know if are
any better than the run-of-the-mill cheap consumer thermometers Pete's
already tried.

Lee Valley probably can supply data and there's at least a decent chance
they may meet the need, but wouldn't bet too much on it without checking
first before laying out $50.

Of course, highly accurate thermometers/sensors are available from
suppliers for lab/scientific measurements, but one pays for the
precision/accuracy.

I don't know otomh what one could find from Omega these days in the
lower-end price range, but there's one place to look.

--


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Old February 4th 18, 05:54 PM posted to alt.home.repair
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Default Thermometers: What's the Problem with Accuracy?

On 04/02/2018 17:11, wrote:
On Sun, 04 Feb 2018 11:51:08 -0500, "(PeteCresswell)"
wrote:

I've been trying to buy four refrigerator/freezer thermometers and it's
frustrating how inaccurate/inconsistent they are.




http://www.leevalley.com/us/garden/P...=2,40733,40734


As an aside, I'm surprised that the US is still using Fahrenheit instead
of the universal Centigrade.
There's only about 8 countries that still use F.

Fahrenheit remains the official scale for the following countries:

The Bahamas, Belize, the Cayman Islands, Palau and the United States and
associated territories (Puerto Rico, Guam and the U.S. Virgin Islands).
Canada retains it as a supplementary scale that can be used alongside
Celsius.





--
Bod
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Old February 4th 18, 05:58 PM posted to alt.home.repair
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Default Thermometers: What's the Problem with Accuracy?

In article , lid
says...

I've been trying to buy four refrigerator/freezer thermometers and it's
frustrating how inaccurate/inconsistent they are.

For Instance:

- 4 thermometers of same make/model, hanging on the same rack.

- Alcohol bulb/glass tube - you'd think basic physics...

- Each reads a different temp from 68 to 74 degrees.

Only thing I can think of is that the card behind the glass thingie is
misaligned, but looking at these things, there does not seem to be enough
physical room for those kinds of errors.

Also, at home I have a couple of digital indoor/outdoor thermometers.

Bring the outdoor sensor inside and put it right next to the master part, and
they're a couple degrees different.

Is there any hope at all of finding four thermometers which:

- All read the same temp when placed side-by-side
- Read the correct temp.

What am I missing?



The best way to get a thermometer that should be correct is to look at
all of them in the store and see how many are showing the same
temperature.

If possiable you should take one and place it in a solution of ice and
water. It should show 32 deg F or 0 deg C. While this will only give a
one point calibration, it should hold close enough for normal ranges of
food or human comfort.



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Old February 4th 18, 06:01 PM posted to alt.home.repair
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Default Thermometers: What's the Problem with Accuracy?

On Sun, 04 Feb 2018 11:51:08 -0500, "(PeteCresswell)"
wrote:

I've been trying to buy four refrigerator/freezer thermometers and it's
frustrating how inaccurate/inconsistent they are.

For Instance:

- 4 thermometers of same make/model, hanging on the same rack.

- Alcohol bulb/glass tube - you'd think basic physics...

- Each reads a different temp from 68 to 74 degrees.

Only thing I can think of is that the card behind the glass thingie is
misaligned, but looking at these things, there does not seem to be enough
physical room for those kinds of errors.

Also, at home I have a couple of digital indoor/outdoor thermometers.

Bring the outdoor sensor inside and put it right next to the master part, and
they're a couple degrees different.

Is there any hope at all of finding four thermometers which:

- All read the same temp when placed side-by-side
- Read the correct temp.

What am I missing?


Spending enough money to get one that has a little quality control in
the manufacturing phase?
My Bacharach sling always shows to be the same as the lab grade
thermometer we use to calibrate the instruments we use for state water
samples but they cost $80+
Digital stuff itself is what I call the great lie. They give you a
very precise reading, that is usually wrong. I have an $8000 (MSRP)
digital water tester from the state that we have to calibrate before
and after every use and about 10-15% of the time, they do not pass the
verification calibration after the test on at least one parameter.
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Old February 4th 18, 06:01 PM posted to alt.home.repair
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Default Thermometers: What's the Problem with Accuracy?

On Sunday, February 4, 2018 at 12:54:53 PM UTC-5, Bod wrote:
On 04/02/2018 17:11, wrote:
On Sun, 04 Feb 2018 11:51:08 -0500, "(PeteCresswell)"
wrote:

I've been trying to buy four refrigerator/freezer thermometers and it's
frustrating how inaccurate/inconsistent they are.




http://www.leevalley.com/us/garden/P...=2,40733,40734


As an aside, I'm surprised that the US is still using Fahrenheit instead
of the universal Centigrade.
There's only about 8 countries that still use F.

Fahrenheit remains the official scale for the following countries:

The Bahamas, Belize, the Cayman Islands, Palau and the United States and
associated territories (Puerto Rico, Guam and the U.S. Virgin Islands).
Canada retains it as a supplementary scale that can be used alongside
Celsius.


I'm surprised you're surprised. Given the chauvinism rampant in the U.S.,
it's only to be expected.

Cindy Hamilton
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Old February 4th 18, 07:27 PM posted to alt.home.repair
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Posts: 7,279
Default Thermometers: What's the Problem with Accuracy?

In alt.home.repair, on Sun, 04 Feb 2018 11:51:08 -0500,
"(PeteCresswell)" wrote:

I've been trying to buy four refrigerator/freezer thermometers and it's
frustrating how inaccurate/inconsistent they are.

For Instance:

- 4 thermometers of same make/model, hanging on the same rack.

- Alcohol bulb/glass tube - you'd think basic physics...


That only works if the bulb is exactly the right size and the amount of
alcohol or mercury inside is exactly correct. I don't want to spend
too much just to get accuracy that won't really help me.

- Each reads a different temp from 68 to 74 degrees.


Last time I bought a thermometer, about 40 years ago (not counting a
digital one that claims to measure humidity), a glass one, there were
about 8 on the rack and I looked at each temp and bought one whose
reading was part of the cluster of readings very close to each other.

What more could I do.

Only thing I can think of is that the card behind the glass thingie is
misaligned, but looking at these things, there does not seem to be enough
physical room for those kinds of errors.


I don't think the card is the problem. Glass thermometers sometimes or
always have a scratch, a file mark, at 32 degrees, on one side of the
tube, I've read. I've never looked closely and I've never seen the
mark, but it makes sense (and it contradicts my first paragraph above,
come to think of it). They'd put all the thermometers in a mixture of
melting ice and water, maybe even in a refrigerated room. Pull them out
one at a time and file the scratch wherever the level happens to be.

Also, at home I have a couple of digital indoor/outdoor thermometers.

Bring the outdoor sensor inside and put it right next to the master part, and
they're a couple degrees different.

Is there any hope at all of finding four thermometers which:

- All read the same temp when placed side-by-side
- Read the correct temp.

What am I missing?


Cynicism. Hopelessness.
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Old February 4th 18, 07:45 PM posted to alt.home.repair
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Posts: 5,234
Default Thermometers: What's the Problem with Accuracy?

On 02/04/2018 11:01 AM, wrote:
Digital stuff itself is what I call the great lie. They give you a
very precise reading, that is usually wrong. I have an $8000 (MSRP)
digital water tester from the state that we have to calibrate before
and after every use and about 10-15% of the time, they do not pass the
verification calibration after the test on at least one parameter.


There are a lot of slips betwixt that cup and lip. I worked for a
company that made pH and ion concentration meters. First you start with
the sensor, which was a Ross electrode in this case. They aren't
identical out of the gate and their characteristics change over time.
The output is fed to an AD converter, which introduces sampling errors
depending on how good the converter is and the rate at which you read
the output. There is noise that has to be cleaned up and finally a
number is obtained. That is fed through the algorithm is question to get
a ion concentration or ph. Finally you wind up with the magic 5.376,
which is precisely displayed on the readout.

Thermistors, thermocouples, glass electrodes, LVDTs and so forth are a
pain in the butt to calibrate and keep in calibration.

Philosophically speaking the entire project to convert the real world to
mathematical equations has been a product of human hubris. It's been
handy at times but it isn't real.
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Old February 4th 18, 07:52 PM posted to alt.home.repair
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Posts: 7,823
Default Thermometers: What's the Problem with Accuracy?

On Sun, 4 Feb 2018 17:54:48 +0000, Bod wrote:

On 04/02/2018 17:11, wrote:
On Sun, 04 Feb 2018 11:51:08 -0500, "(PeteCresswell)"
wrote:

I've been trying to buy four refrigerator/freezer thermometers and it's
frustrating how inaccurate/inconsistent they are.




http://www.leevalley.com/us/garden/P...=2,40733,40734


As an aside, I'm surprised that the US is still using Fahrenheit instead
of the universal Centigrade.
There's only about 8 countries that still use F.

Fahrenheit remains the official scale for the following countries:

The Bahamas, Belize, the Cayman Islands, Palau and the United States and
associated territories (Puerto Rico, Guam and the U.S. Virgin Islands).
Canada retains it as a supplementary scale that can be used alongside
Celsius.


We use what we are used to. OTOH Fahrenheit gives you about twice the
precision without resorting to decimals. I am comfortable with both
since my science friends are all C


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