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'[OT] Infrared temperature measurement'
2007\01\23@123215 by Tamas Rudnai

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Is anybody knows the accuracy of these devices? OK, each says around 1-2
Celsius, however, I am not sure if that is true for all type of surfaces?
Also how the accuracy affected by wind, humidity and vibration?

Thanks,
Tamas


--
unPIC -- The PIC Disassembler
http://unpic.sourceforge.net

2007\01\23@141424 by Herbert Graf

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On Tue, 2007-01-23 at 17:31 +0000, Tamas Rudnai wrote:
> Is anybody knows the accuracy of these devices? OK, each says around 1-2
> Celsius, however, I am not sure if that is true for all type of surfaces?
> Also how the accuracy affected by wind, humidity and vibration?

I can't give you hard numbers, but I can tell you that surface IS
important. They are calibrated for a "matte" type surface, so if you try
using them on say a tile surface they can be WAY off.

I regularly use one while cooking and while they work wonderfully for
most foods, they are horrible when dealing with say a pot of water.

TTYL

2007\01\23@203344 by Rich

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What is your measurement criteria?  What is it that you want to measure?
Did you create an error budget?  Accuracy depends on whether you use a
pyroelectric detector or a silicon lead sulfide or what you are using and
also on the design.  I believe that the "ear thermometers" use a
pyroelectric device.  Pyroelectric detectors are AC devices, not DC devices
so the design is a bit more complicated.
   Non contact temperature measurement is not as accurate as a thermocouple
or thermistor or RTD etc.  Usually NC is reserved for high temperature
measurememts.  But for very high temperature measurements usually x-ray or
streaking film is used.

{Original Message removed}

2007\01\23@235433 by Vasile Surducan

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On 1/23/07, Tamas Rudnai <spam_OUTtamas.rudnaiTakeThisOuTspamgmail.com> wrote:
> Is anybody knows the accuracy of these devices? OK, each says around 1-2

Usually I'll say "In your dreams". But because I know you a little
bit, you deserve a detailed answer.  If you'll measure a red iron
surface comming from a furnance, having say 1800C, how much will means
1-2C as a procentual error ?
Does the iron has exactly the same colour over it's surface ?
If you're measuring 200C of a hot plate  what does it means 1-2C ?
But if you're measuring a cold cup of water (having say 15C) when the
ambiant temperature is +30C, what does it mean 1-2C ?

I think you've got the essence.
greetings,
Vasile

P.S. Do not believe any infrared thermometer builder specifications
(without understanding how was specified) even if it's Raytek or other
great name.


> Celsius, however, I am not sure if that is true for all type of surfaces?
> Also how the accuracy affected by wind, humidity and vibration?
>
> Thanks,
> Tamas
>
>
> --
> unPIC -- The PIC Disassembler
> http://unpic.sourceforge.net
> -

2007\01\24@043512 by Tamas Rudnai

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Thanks for the input. Well, what I need is to measure an iron (200-250 C),
to measure the temperature of my battery, motor and other stuff just to make
sure they are operated at the right way or under the specifications or
whatever. I also was thinking of using such a device if I decide to try out
that home brew smd soldering stuff mentioned here in another topic.

Actually just bought a cheap one to play and make some experience with it.
It says it goes up to 280 C. It seems I could not measure shiny surfaces (as
mentioned by Herbert) and also I have a hot air blow tool but when it is
operated (so the air is moving out from it) this device measures only 42 C,
however, when I switch it off it measures the correct (or I believe the
correct) temperature.

Still in question what about my outrunner motor, where the surface I would
like to measure continuously rotating and obviously the air around moving?
And also in question if I'd like to measure the temp of my two stroke engine
which is vibrating a lot (and also the air screw makes a huge air movement)?
If this type of measurement does not work for those, what other type can I
use?

Thanks again answering to my stupid questions :-)
Tamas



On 1/24/07, Vasile Surducan <.....piclist9KILLspamspam@spam@gmail.com> wrote:
{Quote hidden}

2007\01\24@045749 by Alan B. Pearce

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>If this type of measurement does not work for those,
>what other type can I use?

I would have thought a PRT would work for all those, or a thermocouple
certainly would, although for both type you would have to make sure you had
high temperature insulation on the wires. Often Thermocouples come with
insulation that just doesn't quite make these temperatures, and to get
insulation that is suitable involves a quantum jump in cost.

2007\01\24@082913 by Xiaofan Chen

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On 1/24/07, Alan B. Pearce <.....A.B.PearceKILLspamspam.....rl.ac.uk> wrote:
> I would have thought a PRT would work for all those, or a thermocouple
> certainly would, although for both type you would have to make sure you had
> high temperature insulation on the wires. Often Thermocouples come with
> insulation that just doesn't quite make these temperatures, and to get
> insulation that is suitable involves a quantum jump in cost.
>

Today I attended a seminar hear that there are customers using
Thermocouples (RTD probably would not cut it) for Turbine generator
temperature monitoring and they need very high speed temperature
measurement. I assume that will be quite high temperature.
Just do not know how they do it for the insulation.

For UL related temperature test, typically we use do a temperature
profiling using Infrared temperature measurement to identify the
hot spots and then use Thermocuples to measure the temperature
using data loggers like Agilent 34970A/34980A.

2007\01\24@085221 by Alan B. Pearce

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>Today I attended a seminar hear that there are customers using
>Thermocouples (RTD probably would not cut it) for Turbine generator
>temperature monitoring and they need very high speed temperature
>measurement. I assume that will be quite high temperature.
>Just do not know how they do it for the insulation.

I suspect they use woven fibreglass type sleeving, such as used to be used
on electric stove elements, and toaster wiring.

2007\01\24@135621 by Vasile Surducan

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Tamas borat,

All measurement tools for radiant energy are based on two laws: Wien's
and Stefan-Bolzman law. No matter the pyrometer's basic principle or
the sensors used (two waves pyrometers, global radiation pyrometers,
with photodiodes, thermocouples or pyroelectric detectors) all
pirometers in this world are taking care about those two laws.
Unfortunately I don't have any document written in english (only in
romanian and printed) which could explain the corelation between the
surface area radiation, emisivity and temperature. You should guess it
(I think) searching for those two laws. A very short document
describig the laws  (at page 3) is here:
http://www.ucd.ie/geograph/GMills/course.pdf

Well known is that any pyrometer has an emisivity correction mechanism, which
shows the difference betwen the black body radiation and the real
world measured surfaces.
That's why any precise  pyrometer could have a big measurement error
if the emisivity of the probe under test is unknown. Also, if the
probe target is too small, the error could increase (some pyrometers
can't even measure very small targets).

greetings,
Vasile


On 1/24/07, Tamas Rudnai <EraseMEtamas.rudnaispam_OUTspamTakeThisOuTgmail.com> wrote:
{Quote hidden}

>

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