any way to calibrate digital thermometer?

[Johnny Appleseed]

I have a digital thermometer like the one here:

http://www.walmart.com/ip/Acurite-Wireless-Thermometer/16888921

The temperature the outdoor sensor reads is at least 3 degrees off from what
it should be. Is there any way to adjust the temperature reading in these
units? The instructions don't say anything about this issue.

Thanks,
John

 

[William Sommerwerck]

Make a calibration chart.

 

[Jeff Liebermann]

On Tue, 29 May 2012 11:36:59 -0400, "Johnny Appleseed"
<none@nowhere.non> wrote:

I have a digital thermometer like the one here:

http://www.walmart.com/ip/Acurite-Wireless-Thermometer/16888921

The temperature the outdoor sensor reads is at least 3 degrees off from what
it should be.

Move the thermometer into the shade, away from sources of heat
(vents), and away from anything that will reflect or accumulate heat
(black meal objects). You want to measure the air temperature, not
the temperature of the reflected sun.

Also, how do you know what it "should be"? Your "reference"
thermometer might be just as far off. Incidentally, 3 degrees
variation isn't all that bad.

Such accuracy issues are constant source of entertainment among those
that weather stations that appear on the internet. Some really good
hints:
<http://www.wxqa.com/aprswxnetqc.html>
Here's one that I help maintain:
<http://weather.gladstonefamily.net/site/AR779>
Oops. I forgot to calibrate the barometer to altitude the last time
the power died and the backup battery lasted about 2 hours. Anyway,
this is my version of what it takes to get decent temperature
readings:
<http://802.11junk.com/jeffl/pics/wx/slides/radiation-shield-01.html>
It's called a "radiation shield" or "pagoda". The idea is to keep the
sensor out of direct (or indirect) sunlight, while still allowing for
air flow. However, there's still a problem. The building is a remote
radio site with lots of warm transmitters inside. The slit near the
roof allows hot air from inside the building to dribble out of the
slit. It was close enough to affect the sensor to have had an effect.

None of the cheapo wireless weather sensors have a proper radiation
shield including yours.

Is there any way to adjust the temperature reading in these
units? The instructions don't say anything about this issue.

Not on the cheap wireless sensors. The basic thermistor accuracy is
about +/-0.2% of full scale, which is less than 1 degree. Calibration
isn't really an issue. What is an issue is whether you're measuring
air temp, ground temp, wall temp, reflected sky temp, vent temp, etc.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[nesesu]

On Tuesday, May 29, 2012 8:36:59 AM UTC-7, Johnny Appleseed wrote:

I have a digital thermometer like the one here:

http://www.walmart.com/ip/Acurite-Wireless-Thermometer/16888921

The temperature the outdoor sensor reads is at least 3 degrees off from what
it should be. Is there any way to adjust the temperature reading in these
units? The instructions don't say anything about this issue.

Thanks,
John

John, if you can open the outdoor unit, look and see if there is any tiny potentiometer inside. It is likey that the calibration resides with the analog sensor before the signal is digitized for transmission. If there is a pot [not a trimmer cap for the RF] then note it's position and then adjust it and see if the temperature reading changes. If not, set it back to original and live with it.

Neil S.

 

[mike]

On 5/29/2012 9:04 AM, nesesu wrote:

On Tuesday, May 29, 2012 8:36:59 AM UTC-7, Johnny Appleseed wrote:
I have a digital thermometer like the one here:

http://www.walmart.com/ip/Acurite-Wireless-Thermometer/16888921

The temperature the outdoor sensor reads is at least 3 degrees off from what
it should be. Is there any way to adjust the temperature reading in these
units? The instructions don't say anything about this issue.

Thanks,
John

John, if you can open the outdoor unit, look and see if there is any tiny potentiometer inside. It is likey that the calibration resides with the analog sensor before the signal is digitized for transmission. If there is a pot [not a trimmer cap for the RF] then note it's position and then adjust it and see if the temperature reading changes. If not, set it back to original and live with it.

Neil S.
There's an old saying...

A man with one watch always knows what time it is. A man
with two watches, not so much.
Same goes for thermometers.

Publish what you find out. I've got the same problem.

For me, the only temp that really matters is the temp at which
the pipes freeze.

 

[John Robertson]

Jeff Liebermann wrote:

On Tue, 29 May 2012 11:36:59 -0400, "Johnny Appleseed"
none@nowhere.non> wrote:

I have a digital thermometer like the one here:

http://www.walmart.com/ip/Acurite-Wireless-Thermometer/16888921

The temperature the outdoor sensor reads is at least 3 degrees off from what
it should be.

....
http://802.11junk.com/jeffl/pics/wx/slides/radiation-shield-01.html
It's called a "radiation shield" or "pagoda". The idea is to keep the
sensor out of direct (or indirect) sunlight, while still allowing for
air flow. However, there's still a problem. The building is a remote
radio site with lots of warm transmitters inside. The slit near the
roof allows hot air from inside the building to dribble out of the
slit. It was close enough to affect the sensor to have had an effect.

And if you don't keep it clean, dust/dirt can affect the results...not
to mention wasps possibly finding the inside attractive for a nest (grin).

None of the cheapo wireless weather sensors have a proper radiation
shield including yours.

Is there any way to adjust the temperature reading in these
units? The instructions don't say anything about this issue.

Not on the cheap wireless sensors. The basic thermistor accuracy is
about +/-0.2% of full scale, which is less than 1 degree. Calibration
isn't really an issue. What is an issue is whether you're measuring
air temp, ground temp, wall temp, reflected sky temp, vent temp, etc.

Yup, it is difficult to have precision readings that are consistent over
time. Calibration, calibration, calibration...

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Charles]

http://www.harborfreight.com/non-contact-pocket-thermometer-93983.html

Just posted as an aside. I am amazed at how well the cheap ones work.

 

[Jeff Liebermann]

On Tue, 29 May 2012 15:45:59 -0700, John Robertson <spam@flippers.com>
wrote:

And if you don't keep it clean, dust/dirt can affect the results...not
to mention wasps possibly finding the inside attractive for a nest (grin).

On the other side of the building, the property owner has 5 bee hives.
I've become somewhat accustomed to having honey bees buzzing around my
head when working on the radios in the building. Dirt and dust are
not much of a problem. Corrosion damage to the cheap RJ14 connectors
and flat ribbon wire is more of a problem. Whatever inspired the wx
station manufacturers to use telephone connectors is beyond my limited
imagination. Extra credit to Peet Bros for using an RJ50 connector.
That's a 10 pin version of the common 8 pin RJ45 connector.

Yup, it is difficult to have precision readings that are consistent over
time. Calibration, calibration, calibration...

The theory is that if you design it randomly, build it randomly,
install it randomly, and poll data randomly, all the errors will
cancel each other out resulting in an accurate reading. Never mind
calibration. Just randomize everything.

I'll confess to having done the ice and boiling water calibration
ceremony to various thermometers while in college, but not to a
wireless sensor.
<http://www.in.gov/isdh/files/ThermometerCalibration__3_.pdf>



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

 

[Jeff Liebermann]

On Tue, 29 May 2012 19:11:25 -0400, "Charles"
<charlesschuler@comcast.net> wrote:

http://www.harborfreight.com/non-contact-pocket-thermometer-93983.html
Just posted as an aside. I am amazed at how well the cheap ones work.

My father one told me to beware of anything that is amazing, magical,
miraculous, etc. They rarely are.

I have one of those Centec pocket thermometers. It's great for
cooking. However, there's a problem or three. The beam width is
about 90 degrees making it very difficult to measure the temperature
of an object, without also including the temperature of the
surroundings. An upper limit of 110C means that won't work under the
hood of my car, or for measuring the temperature of my wood burner,
barbeque, or hibachi. There are better units for not much more and
that have a narrower beam width (none of which can seem to get the
laser to align with the measurement spot).

Using an IR thermometer for measuring air temperature is somewhat of a
problem. The air has a very low mass and therefore emits very little
IR light for the device to measure. A solid object that's in thermal
equalibrium with the air temperature will work, but only if it has the
preset 0.95 emissivity. Going outside and measuring the temperature
of various building walls, plants, planters, and dirt, I get wide
variations in readings. The wood planter seems to be the closest to
the air temperature.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

 

[Phil Allison]

"Johnny Appleseed"

I have a digital thermometer like the one here:

http://www.walmart.com/ip/Acurite-Wireless-Thermometer/16888921

The temperature the outdoor sensor reads is at least 3 degrees off from
what it should be.

** How do the two readings compare if the whole caboodle is indoors ?

Much depends of the siting of the outdoor sensor - it needs to be in a shady
spot and get a bit of breeze.

Is there any way to adjust the temperature reading in these units?

** Have look inside yours.

The non radio linked kind generally have no adjustments.


... Phil

 

[gregz]

Jeff Liebermann <jeffl@cruzio.com> wrote:

On Tue, 29 May 2012 19:11:25 -0400, "Charles"
charlesschuler@comcast.net> wrote:

http://www.harborfreight.com/non-contact-pocket-thermometer-93983.html
Just posted as an aside. I am amazed at how well the cheap ones work.

My father one told me to beware of anything that is amazing, magical,
miraculous, etc. They rarely are.

I have one of those Centec pocket thermometers. It's great for
cooking. However, there's a problem or three. The beam width is
about 90 degrees making it very difficult to measure the temperature
of an object, without also including the temperature of the
surroundings. An upper limit of 110C means that won't work under the
hood of my car, or for measuring the temperature of my wood burner,
barbeque, or hibachi. There are better units for not much more and
that have a narrower beam width (none of which can seem to get the
laser to align with the measurement spot).

Using an IR thermometer for measuring air temperature is somewhat of a
problem. The air has a very low mass and therefore emits very little
IR light for the device to measure. A solid object that's in thermal
equalibrium with the air temperature will work, but only if it has the
preset 0.95 emissivity. Going outside and measuring the temperature
of various building walls, plants, planters, and dirt, I get wide
variations in readings. The wood planter seems to be the closest to
the air temperature.

You can hold up a piece of paper in front and measure air temp. You can
even tape a piece of paper on the front. Just stay out of sunlight.

Greg

 

[gregz]

"Johnny Appleseed" <none@nowhere.non> wrote:

I have a digital thermometer like the one here:

http://www.walmart.com/ip/Acurite-Wireless-Thermometer/16888921

The temperature the outdoor sensor reads is at least 3 degrees off from
what it should be. Is there any way to adjust the temperature reading in
these units? The instructions don't say anything about this issue.

Thanks,
John

Outdoor remote sensors. Something I asked for a couple years before they
existed for home use.

Mine vary. I have two. 2-3 degrees. I have not tinkered with circuitry. I
also have a third I have not compared. One is under my porch roof. As the
patio heats up from the sun in the afternoon, it rises from true ambient.

It's very tricky to calibrate ordinary probe devices, something I did
frequently. Probes need to be on top of each other. Even in water, you must
circulate it very fast for accuracy.

Greg

 

[isw]

In article <jq2qes$hn$1@dont-email.me>,
"Johnny Appleseed" <none@nowhere.non> wrote:

I have a digital thermometer like the one here:

http://www.walmart.com/ip/Acurite-Wireless-Thermometer/16888921

The temperature the outdoor sensor reads is at least 3 degrees off from what
it should be. Is there any way to adjust the temperature reading in these
units? The instructions don't say anything about this issue.

If it's reading high, you might be able to hack a resistive divider to
improve things. If it's reading too low, there's probably not much you
can do.

Isaac

 

[John Robertson]

Jeff Liebermann wrote:

On Tue, 29 May 2012 15:45:59 -0700, John Robertson <spam@flippers.com
wrote:

And if you don't keep it clean, dust/dirt can affect the results...not
to mention wasps possibly finding the inside attractive for a nest (grin).

On the other side of the building, the property owner has 5 bee hives.
I've become somewhat accustomed to having honey bees buzzing around my
head when working on the radios in the building. Dirt and dust are
not much of a problem. Corrosion damage to the cheap RJ14 connectors
and flat ribbon wire is more of a problem. Whatever inspired the wx
station manufacturers to use telephone connectors is beyond my limited
imagination. Extra credit to Peet Bros for using an RJ50 connector.
That's a 10 pin version of the common 8 pin RJ45 connector.

Yup, it is difficult to have precision readings that are consistent over
time. Calibration, calibration, calibration...

The theory is that if you design it randomly, build it randomly,
install it randomly, and poll data randomly, all the errors will
cancel each other out resulting in an accurate reading. Never mind
calibration. Just randomize everything.

So is that how some researchers get accuracy to .001 using
hundreds/thousands of devices calibrated to 0.1?

I'll confess to having done the ice and boiling water calibration
ceremony to various thermometers while in college, but not to a
wireless sensor.
http://www.in.gov/isdh/files/ThermometerCalibration__3_.pdf

Put the sensor in a baggie and suck the air out then see how it measures
up...

John :-#)#


--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[William Sommerwerck]

I remain amazed. I gave a simple answer, which was implicitly endorsed by
another person, but which has been ignored.

"The Lady from Philadelphia" recommends the following...

Place the conventional thermometer you trust and the transmitter in the same
shaded spot. Make a chart with the transmitter's readings in the left
column, the thermometer's readings in the right column. Check the digital
thermometer's reading whenever you care to. When there's a change, walk out
of the house and read the conventional thermometer. (Such an exhausting
trek! Bring plenty of food and water, along with sunscreen and plenty of
books to read. Hire a sherpa to carry it all.) Add both values to the chart.

Is there something wrong with a simple solution? Tell me, I want to know.
Really.

We are talking about a (presumably) cheap digital/remote thermometer, which
likely has //no// calibration controls. (If it has any, it's probably just
one, for a temperature around 75F.) What is it with this hacker mentality
that demands wasting time on something that is just not that important?

 

[Gareth Magennis]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:jq503v$4om$1@dont-email.me...

I remain amazed. I gave a simple answer, which was implicitly endorsed by
another person, but which has been ignored.

"The Lady from Philadelphia" recommends the following...

Place the conventional thermometer you trust and the transmitter in the
same
shaded spot. Make a chart with the transmitter's readings in the left
column, the thermometer's readings in the right column. Check the digital
thermometer's reading whenever you care to. When there's a change, walk
out
of the house and read the conventional thermometer. (Such an exhausting
trek! Bring plenty of food and water, along with sunscreen and plenty of
books to read. Hire a sherpa to carry it all.) Add both values to the
chart.

Is there something wrong with a simple solution? Tell me, I want to know.
Really.

We are talking about a (presumably) cheap digital/remote thermometer,
which
likely has //no// calibration controls. (If it has any, it's probably just
one, for a temperature around 75F.) What is it with this hacker mentality
that demands wasting time on something that is just not that important?

Hacking the thermometer so it gives the correct reading is going to take a
few minutes once the solution is found here, if there is one.

Your method is likely to take a full year.

You are a bit of a knob sometimes, William, no wonder people ignore you.



Gareth.

 

[William Sommerwerck]

"Gareth Magennis" <sound.service@btconnect.com> wrote in message
news:I8udnVbWXfbwklvSnZ2dnUVZ8sCdnZ2d@bt.com...

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:jq503v$4om$1@dont-email.me...

Hacking the thermometer so it gives the correct reading is
going to take a few minutes once the solution is found here,
if there is one.

Which is exactly the point. How much time has been wasted on looking for
that solution -- with no results?

I have a wireless thermometer that's part of an atomic clock. Without even
opening it, I'd be willing to bet that the temperature sensing elements
comprise one resistor in series with one thermistor. You were, perhaps,
expecting multiple resistors and thermistors, with two or three pots to get
everything "just right"?

This "knob" is all-too-aware from many years of experience that virtually
all products are built to meet a price point, and that attempts to improve
or customize them //almost// always result in failure.

To give an example... I once owned the Pioneer RT-2000 system. It had
modular electronics and interchangeable half-track two-channel &
quarter-track four-channel head blocks. It was a clever and useful idea,
poorly executed.

When I started making live recordings, it occurred to me to position my dbx
II noise-reduction units between the Pioneer's external electronics
(containing the mic preamps and mixers) and the transport. To my surprise,
there was no improvement in the S/N ratio.

The 0dB sensitivity of the transport electronics was an unbelievably low
0.1V, way below what is commonly taken as line level. When I measured the
S/N ratio of the external electronics at 0.1V output, it was a miserable
50dB. No wonder noise reduction had no effect.

I was obliged to purchase external mic preamps. Re-engineering Pioneer's
crappy electronics might have been a worthwhile project if I were trying to
improve my skills in circuit design. But I wasn't, so what would be the
point? Life is too short.

Your method is likely to take a full year.
You are a bit of a knob sometimes, William,
no wonder people ignore you.

I BEG YOUR FORGIVENESS for trying to see through to the heart of an issue,
of trying to find simple solutions to "complicated" problems -- or of
recognizing that there really is NO PROBLEM at all.

You would do well to pay attention to this "knob". You might learn something
about problem solving. But, of course, you already know everything, right?

 

[Gareth Magennis]

You would do well to pay attention to this "knob". You might learn
something
about problem solving. But, of course, you already know everything, right?

No, I do not know everything.

I do know that you are a bit of a knob, though.



Gareth.

 

[William Sommerwerck]

You would do well to pay attention to this "knob".
You might learn something about problem solving.
But, of course, you already know everything, right?

No, I do not know everything.
I do know that you are a bit of a knob, though.

So I take it that, over the years, you have learned nothing new about
problem solving from me? That's a shame.

 

[Jeff Liebermann]

On Tue, 29 May 2012 22:00:36 -0700, John Robertson <spam@flippers.com>
wrote:

So is that how some researchers get accuracy to .001 using
hundreds/thousands of devices calibrated to 0.1?

They probably bribed the peer reviewers or made some manner of quid
pro quo deal. The lab assistant that ran the numbers probably didn't
care about signifigant figures or the difference between resolution
and accuracy. If it fits in the speadsheet box, it must be correct.

Incidentally, at 0.001C resolution, the heat emitted by the observer
becomes signifigant.

I'll confess to having done the ice and boiling water calibration
ceremony to various thermometers while in college, but not to a
wireless sensor.
http://www.in.gov/isdh/files/ThermometerCalibration__3_.pdf

Put the sensor in a baggie and suck the air out then see how it measures
up...

If you let everything equalize to ambient temperature, you'll
eventually get an accurate reading. Incidentally, many black plastic
shipping bags are somewhat transparent to IR.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558