Message Board Thread - "Calibration of FLIR Thermacam SC3000"

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Calibration of FLIR Thermacam SC3000 fraffan 10/12/2007
I am having issues calibrating the camera's readings. I am using the camera to visualize a heated plate, with temperatures ranging along the plate from about room temperature to about 70+ Celsius. Because of this, I cannot accurately use the emissivity calculation around the near room temperature points. From a literature search I made, the temperature and the intensity registered by the sensor are proportional, and related by a function involving 3 constants and an exponential, analogous to Plank's law. Does anyone know what these constants are for the FLIR systems? I am trying to use them as starting guesses to alter them and refit my data, in which case the new constants should account for emissivity variations, transmissivity, and other effects.
 
Re:Calibration of FLIR Thermacam SC3000 Gary Orlove 11/1/2007
The Planck model function that you refer to is a transfer function between radiation that leaves an object and its Black body temperature. It takes into account the spectral response of the camera. The relation between the radiation that hits the detector and what leaves the object, is expressed by the "measurement formula", which is:
Rcam = t*(e*Robj + (1-e)Rrefl) + (1-t)*Ratm

Rrefl = radiation that comes from surrounding and is reflected by the object into the camera.
Ratm = radiation by the atmosphere.
t = transmissivity of the atmosphere. Indirectly set by Rel humidity, Tatm and Distance.
e = emissivity of the object

You resolve Robj from this equation and apply Robj = R/(exp(B/T) +F) to find the Black body temperature T of the object. R is a conversion factor of the detector, B is related to the spectral response of the camera, F is a corrective factor that is individual to each camera. R, B, and F are determined by the factory when calibration the camera in the black body laboratory. The bottom line is that it is not possible to use the RBF function to correct for object parameters like e, t or distance.

There are laboratory methods to find the emissivity of an object, this includes heating the object at least 30degC above reflecting surroundings.
See also chapter 7 in the Operator's Manual of SC3000.
 


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