Determining Alumina temperature with the Optris when emissivity is set to 1
As an attachment to this post a small Windows executable is included which calculates
the {approximate} temperature of an Alumina object from the temperature shown by the Optris
when the in band emissivity of the Optris is set to 1.
The input of the program is thus the temperature shown by the Optris for an emissivity setting of 1.
As a first step, from this temperature a new initial temperature to be used by an iterative
procedure is calculated and this temperature is shown by the program.
The program then uses both this initial temperature and the ambient temperature to do an
iterative procedure in order to calculate the temperature.
Note that the iterative procedure used by the software program to solve for the temperature
converges less fast to the final temperature then the one the Lugano testers used.
(The iterative procedure used by the Lugano testers was not published)
As an example we use a measured temperature by the Optris of 450.3 degree C, the same as
the temperature used during the dummy run example iteration in the Lugano report.
For this temperature the in band emissivty setting used is 0.902
Ambient temperature is set to 20.8 degree C.
Setting back the emissivity to 1 then yields a temperature of 420.9 degree C.
(When an other emissivity setting was used on the Optris, the value for an in band emissivity
setting of 1 will still be 420.9 degree C if the temperature of the Alumina object measured was
450.3 degree C.)
The temperature of 420.9 degree C is then input in the program together with the ambient
temperature.
When pressing the calculate button the program will calculate the initial temperature to be
used by the iteration procedure as 366.6 degree C.
Using this temperature and the given ambient temperature of 20.8 degree C the program
then calculates using the iterative procedure the temperature.
The outcome of this iterative procedure is the original temperature of 450.3 degree C.
A screen dump of the above example is shown in the following picture.
The iteration procedure is intended for use at temperatures above 250 degree C
Between 250 degree C and 1000 degree C the expected error is less then 1 % (degree C)
with an average error of about 0 (zero) percent.
For temperatures between 1000 and 1350 degree C the expected error is less then 2 %.
Below 250 degree C the calculated temperatures become inaccurate.
This means that if the same (or nearly same) procedure was used during the Lugano
dummy run, then the iteration could have been used for determining the temperatures
on the ECAT while for the lower temperature rods an other method (such as using an
Optris with correct in band emissivity settings) should have been used.
The program uses for it's iterative procedure only information from the broadband emissivity
curve of Alumina !
Note :
I tested the program om three different computers where it was running without problems.
That is no guarantee that it will work on your computer
If it is not working try to install the .net framework version 2 and see if that resolves the problem.
OptrisTemp.zip