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Luca

Wed Nov 24 2010, 09:49AM

Registered Member #2481 Joined: Mon Nov 23 2009, 03:07PM
Location: ITALY
Posts: 134

Hi all,
I need to make a thermometer using IR detectors. I am looking for detectors like pyroelectric or thermopiles but I think that the latter are the most suitable...
I dont need anything really precise, something with an accuracy of +/-1Â°C would be enough. The important point is that it should be something as cheap as possible (it's not for an amatorial project, it is for industrial production...)
I have searched on internet but it seems quite difficult to find this kind of devices, I have found a component on RS but it's quite expensive, and I have seen that PerkinElmer makes thermopile detectrors but, agian, I am worried about the price...

Do you know manufacturers that produce this kind of decvices?

Dy you have any other suggestions? (other kind of detectors, etc...)

Regards,

Luca

Sulaiman

Wed Nov 24 2010, 06:37PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

What is the temperature range that you need to measure?

Luca

Wed Nov 24 2010, 09:24PM

Registered Member #2481 Joined: Mon Nov 23 2009, 03:07PM
Location: ITALY
Posts: 134

Sulaiman wrote ...

What is the temperature range that you need to measure?

The subject will be between ambient temp and +150Â°C, while the sensor will be between -25 and +75Â°C

Luca

lightlinked

Thu Nov 25 2010, 01:37AM

Registered Member #2087 Joined: Tue Apr 21 2009, 08:32AM
Location:
Posts: 115

this melexis sensor is available from a few manufacturers on breakout boards.

Bjørn

Thu Nov 25 2010, 08:34AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

I dont need anything really precise, something with an accuracy of +/-1Â°C would be enough.

For a cheap non contact sensor that is very accurate and in some cases impossible. The accuracy would depened a lot on the type of surface of the target and other variables.

You can get cheap PIR sensors for less than $2 but you need the type with a single element. The ones with two elements in antiparallel are only suitable for detecting changes in temperature. To get your required accuracy under all conditions the circuit required would be complex. There are ready made chips for the purpose but they may fail to reach your accuracy target.

Here is an article with some ideas:

There must be countless patents you can study.

Luca

Tue Nov 30 2010, 10:02AM

Registered Member #2481 Joined: Mon Nov 23 2009, 03:07PM
Location: ITALY
Posts: 134

BjÃ¸rn wrote ...

For a cheap non contact sensor that is very accurate and in some cases impossible. The accuracy would depened a lot on the type of surface of the target and other variables.

You can get cheap PIR sensors for less than $2 but you need the type with a single element. The ones with two elements in antiparallel are only suitable for detecting changes in temperature. To get your required accuracy under all conditions the circuit required would be complex. There are ready made chips for the purpose but they may fail to reach your accuracy target.

Here is an article with some ideas:

There must be countless patents you can study.

We have found thermopile sensors from Heimansensors with the precision of 0.1Â°C for less than 2 euros (price for very large volumes). There are also complete modules, with the co-packaged ASIC for signal conditioning and A/D conversion, but these are much more expensive (x10...)

If you think to some modern medical thermometers (ear-thermometer), they are based on the same technology (IR), they have at least 0.1Â°C precision and they are on the market for few tens of euros. So, it is obvious that the sensor itself must cost only few euros.

Regards,

Luca

Bored Chemist

Tue Nov 30 2010, 04:24PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Not many people's ears range from ambient to 150C.
0.1C is easier if you know that the material you are looking at is always the same stuff - i.e. skin and therefore always has the same emissivity and it is practically always 30C to 40 C.
Having the sensor maintained at room temp helps too.

klugesmith

Tue Nov 30 2010, 09:42PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Bored Chemist wrote ...
... easier if you know that the material you are looking at is always the same stuff - i.e. skin and therefore always has the same emissivity and it is practically always 30C to 40 C.

There's a lot of valid "green" media buzz lately, about painting dark roofs white to keep houses cooler in summer time. But it's a joke when a contractor escorts a reporter to a sunny work site, points his IR thermometer at some unpainted black roofing, then a freshly painted white section, and claims instant 30 degree reduction. No allowance for different emissivity in the long wave IR (or evaporative cooling of wet paint, for that matter).

Steve Conner

Wed Dec 01 2010, 11:05AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

What is the point of this? You can go to a store and buy a non-contact IR thermometer, so why does the original poster want to make one?

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