Searching \ for '[OT] IR Temp measurement' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/io/irs.htm?key=ir
Search entire site for: 'IR Temp measurement'.

Exact match. Not showing close matches.
PICList Thread
'[OT] IR Temp measurement'
1999\01\06@140131 by Nigel Orr

flavicon
face
Sorry for the OT, it will have a PIC in it...

I posted a while back asking about high temp electronics, to build a temp
sensor for a gas oven (up to 300 deg C).  I didn't see any replies, so I
was wondering if it would be possible to measure the temp externally with
an IR sensor fixed to the outside of the door, looking in.  There are
various wavelength sensors available- most seem to be 1 - 15 micron- can
anyone tell me how feasible this is likely to be, and what wavelength is
useful for temperature measurements?  Accuracy needed isn't _very_ high-
just for domestic cooking- say within 1 'gas mark'- about 25 deg C.

Any pointers?

Nigel
--
Nigel Orr                  Research Associate   O   ______
       Underwater Acoustics Group,              o / o    \_/(
Dept of Electrical and Electronic Engineering     (_   <   _ (
    University of Newcastle Upon Tyne             \______/ \(

1999\01\07@164720 by Gerhard Fiedler

picon face
At 16:46 01/06/99 +0000, Nigel Orr wrote:
>I posted a while back asking about high temp electronics, to build a temp
>sensor for a gas oven (up to 300 deg C).  I didn't see any replies, so I
>was wondering if it would be possible to measure the temp externally with
>an IR sensor fixed to the outside of the door, looking in.  There are
>various wavelength sensors available- most seem to be 1 - 15 micron- can
>anyone tell me how feasible this is likely to be, and what wavelength is
>useful for temperature measurements?  Accuracy needed isn't _very_ high-
>just for domestic cooking- say within 1 'gas mark'- about 25 deg C.

what's the problem with the 300 deg? can't you just put a thermocouple in
there? the thing with the ir sensor "looking in" is that most of them are
pretty picky about what they're looking through, since that material tends
to change the ir spectrum of the radiation -- and they're a lot more
expensive than a thermocouple.

ge

1999\01\08@050302 by Nigel Orr

flavicon
face
At 13:46 07/01/99 -0800, you wrote:
>what's the problem with the 300 deg? can't you just put a thermocouple in

I haven't seen, from a browse of catalogues, thermocouples with a decent
lead length, and if I want to crimp extensions on, I can't find insulated
wires which can cope with 300 deg C- it's not impossible that I'm missing
something obvious... are there thermocouples with 1ft or so of cable (300mm
for the metricated) attached, where the cable is rated at >300 deg?

>there? the thing with the ir sensor "looking in" is that most of them are
>pretty picky about what they're looking through, since that material tends

It could be compensated for that, presumably?

>to change the ir spectrum of the radiation -- and they're a lot more
>expensive than a thermocouple.

A complete IR thermometer costs about UKP99 and upwards, but the IR devices
seem to be UKP5 and under.

Nigel

1999\01\08@122238 by Dwayne Reid

flavicon
face
>I haven't seen, from a browse of catalogues, thermocouples with a decent
>lead length, and if I want to crimp extensions on, I can't find insulated
>wires which can cope with 300 deg C- it's not impossible that I'm missing
>something obvious... are there thermocouples with 1ft or so of cable (300mm
>for the metricated) attached, where the cable is rated at >300 deg?

I normally have my thermocouples custom made by a local supplier and specify
the lead length I require.  This is both cheaper and more reliable than off
the shelf TCs if ambient temperature is high since I can specify the use of
high temperature fill counpund in the transition area.

Something that sounds more to your requirements would be a long skinny
thermocouple where the transition area is not in the high temperature zone.
For example, I use 24" and 36" long thermocouples with a diameter of only
1/16".  It is flexible (bend radius has to exceed 1/2") and senses
temperature only at the tip.  My cost for the 24" version is about $30
Canadian - this is with a 6 foot fiberglass wire.

You can splice thermocouple wire so long as you use the same type of wire
for the extension.  I generally tell people to make a pigtail splice (twist
the wires together so that they are in direct contact with each other), then
use a wire nut or crimp to keep the wires under pressure.  Because the wires
are in direct contact with each other, the use of a different metal around
the splice does not cause any significant error.

dwayne


Dwayne Reid   <spam_OUTdwaynerTakeThisOuTspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(403) 489-3199 voice     (403) 487-6397 fax

1999\01\08@134218 by Jim Sokoloff

picon face
Nigel Orr wrote:
>
> At 13:46 07/01/99 -0800, you wrote:
> >what's the problem with the 300 deg? can't you just put a thermocouple in
>
> I haven't seen, from a browse of catalogues, thermocouples with a decent
> lead length, and if I want to crimp extensions on, I can't find insulated
> wires which can cope with 300 deg C- it's not impossible that I'm missing
> something obvious... are there thermocouples with 1ft or so of cable (300mm
> for the metricated) attached, where the cable is rated at >300 deg?

Look at aircraft (or aircooled auto [VW Beetle]) cylinder head temp
probes. You could certainly get the "long time constant" behavior
correct this way.

For the short time constant behavior, you could consider EGT (exhuast
gas temp) probes, though I don't know how accurate they are at those
temps (though 300C is getting up there...)

---Jim

1999\01\08@150813 by Gerhard Fiedler

picon face
At 10:01 01/08/99 +0000, Nigel Orr wrote:
>I haven't seen, from a browse of catalogues, thermocouples with a decent
>lead length, and if I want to crimp extensions on, I can't find insulated
>wires which can cope with 300 deg C- it's not impossible that I'm missing
>something obvious... are there thermocouples with 1ft or so of cable (300mm
>for the metricated) attached, where the cable is rated at >300 deg?

i'm not sure i understand you here, but you get thermocouple probes in a
small, long steel tube with lengths of 1 to 3 feet easily. this should be
enough to get you out of the furnace with the connection point, and gives
your probe protection.


>>there? the thing with the ir sensor "looking in" is that most of them are
>>pretty picky about what they're looking through, since that material tends
>
>It could be compensated for that, presumably?

maybe; it may be non-linear, since there may be a somewhat complex
algorithm involved to achieve accuracy. and the window would have to be
always clean.

>>to change the ir spectrum of the radiation -- and they're a lot more
>>expensive than a thermocouple.
>
>A complete IR thermometer costs about UKP99 and upwards, but the IR devices
>seem to be UKP5 and under.

this might work in your application, if you have always the same physical
conditions like background material and color and the window is always
clean, and you can calibrate the sensor to linearize the output. if the
background or the window change in their optical characteristics, it gets
trickier. usually they compare different sensors with different spectrums
and calculate from there.

ge

More... (looser matching)
- Last day of these posts
- In 1999 , 2000 only
- Today
- New search...