Post by thread:IR Temperature sensing

Hi everyone I want to make an infrared temperature sensor to read the temperature of a liquid. Does anyone know how temperature sensing is accomplished in commercial IR temperature sensors like Raytek and many others? Has anybody already used or made their own IR temperature sensor, using a pic or stamp (or any controller for that matter), that is willing to share or at least point me in the right direction? The technology appears to be pretty accurate, but I am curious as to the expense of construction. I suppose the IR method can only measure the temperature of a surface not a gas? Thanks in advance Jon

At 08:57 03/27/99 -0500, Jon Petty wrote: >Does anyone know how temperature sensing is accomplished in commercial IR >temperature sensors like Raytek and many others? you have basically two categories: one depends on the specific surface, and the other not. each surface has an emission spectrum (which changes with temperature), and each sensor has a detection spectrum, and what you measure is the overlay (multiplication) of one spectrum on the other. if you have to deal with only one type of surface, you can calibrate a single ir diode for that specific surface; that's the easy way. (there are different diodes with different spectrums, like Ge and Si and so on. you select one that's sensitive for the target temperature radiation.) if you have to deal with varying (unknown) surfaces, i think what they do is use sensors with different spectrums, compare the readings and calculate a largely surface-independent temperature. when the temperature changes, the radiated energy changes and the spectrum of it. i don't know exactly how they do the math, and i assume it is not trivial, but i'm pretty sure that it involves sensors with different spectrums. ge

In a message dated 3/27/99 1:44:53 PM US Mountain Standard Time, spam_OUTlistsTakeThisOuTHOME.COM writes: << each surface has an emission spectrum (which changes with temperature), and each sensor has a detection spectrum, and what you measure is the overlay (multiplication) of one spectrum on the other. if you have to deal with only one type of surface, you can calibrate a single ir diode for that specific surface; that's the easy way. (there are different diodes with different spectrums, like Ge and Si and so on. you select one that's sensitive for the target temperature radiation.) >> First, thanks for the reply Could you explain a little more about emission spectrum? How does emission spectrum relate to the wavelength of the IR diode? The IR sensors I have been using for simple distance measurement are at 940nm. What if there are slight changes in the composition of a surface and you calibrated the sensor for that surface? I guess I am not sure what effect the emission spectrum has on the measured value. Do you have any idea how to calibrate a diode for a surface? I have been using an IR diode and a TSL 245 IR-to-frequency-converter to measure small distances measuring the amount of IR signal reflected. Could the same setup be used for IR temp sensing? Thanks Jon

Hi ! Jon Petty wrote: > I want to make an infrared temperature sensor to read the temperature of a > liquid. > > Does anyone know how temperature sensing is accomplished in commercial IR > temperature sensors like Raytek and many others? A friend has build a device for IR temperature messurement. He used a ready made sensor. It was NOT cheap (iirc ca. 400 DM from RS Comp.). The output interface (the 2 wires comming out of the sensor) was exactly like a thermo couple. He used a special IC from Analog Devices for compensating the reference junction and the build in ADC ( the micro was a 80C537, not a PIC ;-( I don't have expiriance with IR diodes for temp. messurement. What's about the 'phyro sensors' used in PIR moution detectors ? If you are interesetd in i coul'd ask what sensor he uses. St.

Hi back Yes I am interested in the type of sensor, but I need to test temperatures from 180-600 deg F. Thanks Jon In a message dated 3/28/99 2:49:45 PM US Mountain Standard Time, .....rangueloKILLspam@spam@INFORMATIK.HU-BERLIN.DE writes: << I don't have expiriance with IR diodes for temp. messurement. What's about the 'phyro sensors' used in PIR moution detectors ? If you are interesetd in i coul'd ask what sensor he uses. St. >>

Hi ! Jon Petty wrote: > > Yes I am interested in the type of sensor, but I need to test temperatures > from 180-600 deg F. The Sensor was from Exergen : http://www.exergen.com They have some useful pdf files ! www.exergen.com/industrl/pdfs/irtcbook.pdf http://www.exergen.com/eductr/indusctr/index.htm St.