I'm putting the Optris calculations into a spreadsheet -- the following is documentation of the formulae used in readable form
From the Optris "IR Basics" documentation (Page 7) From the actual object temperature (To) and ambient (Ta) To Actual temperature e emmisivity Ta Actual ambient C a constant in the calorimeter Tp Temperature of pyrometer n exponent -- depends on wavelenght U = C *( e*To^n + (1- e)*Ta^n - Tp^n) Measured temperature reported by the calorimeter Tm Measured temperature Note : the optris equation uses the same symbol for Tm and To --- so it seems to be self-referential Tm = root(n,(U - C*Ta^n + C*e*Ta^n + C*Tp^n)/ C*e) Note that a lot of the "e" cancel out, leaving 1/e terms root(n,val) can be computed as power(val,1/n) -- some languages have problems with this Pm Total power calculated from Tm Pm = a * e * ( Tm^4 - Ta^4) I'll put these equations into the spreadsheet and see what happens for various "n" (wavelength) and "e" emmisivity