Hello,
I am currently a student majoring in Mechanical Engineering and i am using Spectrometer to measure transmittance.
While utilizing the scope mode in the software, I have been able to obtain information on wavelength and counts.
However, I am seeking clarification on what exactly counts represent and how to interpret them in terms of light intensity or transmittance.
1. What is the counts?
2. How to calculate counts to intensity?
3. How to convert counts to intensity?
Dear Park Jun Jae ,
for calculating the transmittance of a sample you fortunately do not have to know the absolute values of the intensity I impinging onto the detector or the entrance slit of your monochromator.
The count-scale (CS) presented at your spectrum is proportional to the intensity (I) at a particular wavelength for the light measured by the spectrometer:
CS ~ I.
For gathering the transmittance your have to acquire two spectra,
a) the primary spectrum CS0 without any sample and
b) the transmitted spectrum CStr with the sample being passed by the light, and afterwards you have to
c) divide them to get the transmittance T
T(lambda) = CStr(lambda)/CS0(lambda) = Itr(lambda)/ I0(lambda).
The evaluation of the intensity is more complex.
You have to know, how the 'counts' are related to the photon flux acquired by the detector. This may be found in the manual of the spectrometer.
Then you have to know proportionality factors involving the detector area or the net area of the input slit of the monochromator and the spectral resolution of the monochromator, which may be wavelength dependent. If you do not have these factors at hand, please take your hands off such calculations. You do not need them for the transmission. They will cancel each other anyway when performing the ratio T = I/Io.
Good luck and
best regards
G.M.
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