I've seen contactless thermometer guns for sale for ~£40-50, which can read temperatures up to 1000°C. However, the only electronics components I can find which can measure these temperatures without contact seem to be very specialist and very expensive (>£100). The only hobby electronics level IR sensors I can find seem to be rated to either 260°C or 380°C. So what technology are the commercial 1000°C guns using inside?
Electronic – What technology do IR temperature guns use
sensortemperature
Best Answer
Consider this picture of black body spectral radiation: -
On the picture above I've drawn two vertical bands coloured orange and light blue. These bands represent the parts of the infra red spectrum where two different photodiodes might have their most sensitive region. Photodiodes can be made to have a very tight spectral sensitivity if they are used with optical filters - this is important for contactless temperature measurements because you only want to pick-up part of the spectrum so that you can adequately differentiate one temperature from another.
The orange band (circa 7 um) is good for sensing ambient temperatures and maybe up to 1000 K but the curves of black-body radiation tend to merge above this making accurate temperature measurements prone to error.
The blue band (circa 1 um) is good for higher temperatures but pretty useless for measuring anything much below 1000 K due to lack of sensitivity (aka increase noise causing errors).
Given that most commercial applications (the biggest majority of sales and applications) will use sensors in the orange band area (with a pinch of salt) they will be the cheaper technology because of much higher volume.
Given that high temperature applications won't work at ambient or moderate temperatures and they represent a much smaller quantity of sales, they will naturally tend to be more expensive.
How they work
Black body radiation is light emitted from the surface of an object and not light reflected by that object - that's embedded in the term "black-body" - a black body cannot reflect, it can only emit. But real world objects are not perfect black bodies and real world objects vary in their amount of emissivity. So, life, as usual isn't perfect and we make the best job we can and use Plank's law to give us the best answers we can expect: -
Another name for a contactless device is an optical pyrometer in case you wanted to do some further reading.