Message Board Thread - "background temperature conversion formula "

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background temperature conversion formula robbie 11/21/2006
Using the trusted PM-390 camera, we are often called on to shoot hydrogen reformer furnace tubes.
The procedure of course involves input of background temperatures to obtain accurate tubeskin temperatures.
Now I know that the camera and/or software does the calculation for me.
Could someone give me this conversion formula?
There may be times when operators will be checking these tubes with a short wave Cyclops gun.
If I could instruct them to get a background temp.,and a tube temp. then hopefully with a SIMPLE formula I could figure actual tube temperatures.
Thank You in Advance,
Re:background temperature conversion formula Bob Berry 11/22/2006
Calculation or estimation of background temperature is done by the operator, not the camera or software. This is a very difficult application and you should not consider it a simple procedure to measure the temperature of the tubes. I personally do not see how this could be done with a spot radiometer, regardless of what formula used. Also the spot radiometer you are using may not be filtered to allow you to measure through the flames.
Re:background temperature conversion formula robbie 11/22/2006
This particular hydrogen reformer furnace does not involve shooting through flames at the upper level that we are checking.
The gun that we will be using is a Minolta(Land Instruments) Cyclops unit that is designed for this application and used widely for this purpose throughout the industry.
The conversion would be done by myself to obtain accurate actual tube temperatures.
The thermal camera would still be used in conjunction with the thermal gun, but on occasion the operators could shoot a background(refractory)temp., and a tube temp. which I could convert to actual tube temp. using the proper formula.

Re:background temperature conversion formula Gary Orlove 11/22/2006
The basic measurement formula for non contact thermometry is shown below. Basically you convert temperatures you do know into "radiation" units through the calibration curve of the IR instrument. You then calculate your unknown parameter in "radiation" units, then go back to the calibration curve to convert back to temperature. DO NOT USE TEMPERATURES DIRECTLY IN THE FORMULA, YOU WILL GET INCORRECT RESULTS. IR cameras sense IR radiation, not temperature, remember Planck and Stefan Boltzmann from your IR training?

Gary Orlove
Infrared Training Center
Re:background temperature conversion formula robbie 11/22/2006
Thanks Gary

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