Table of Contents
Advertisement
The use of filters improves the sensitivity of this
process and choice of the correct optical filter (and,
therefore, the correct wavelength) of light is important.
It is interesting to note that the filter that gives the
most sensitive calibration for a test factor is the
complementary colour of the test sample. For example,
the chlorine test produces a pink colour proportional to
the chlorine concentration in the sample (the greater
the chlorine concentration, the darker the pink colour).
In this case, a green filter gives the greatest sensitivity
as a pinkish-red solution absorbs mostly green light.
Palintest photometers calculate and then display the test
results directly in milligrams per litre (mg/l) of the test
factor, by comparing the amount of absorbed light to
the calibration data programmed into the instrument.
I
ncident
Wavelengths of blue light
plus small quantities of red
light pass through the
solution.
Blue Solution
(450 - 500nm)
Red Filter
(625 – 635nm)
Red light only passes
through the filter. All
other light is absorbed.
Photodetector
7
Advertisement
Table of Contents
