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A microprocessor controlled special tungsten lamp emits radiation
which is first optically conditioned and beamed to the sample contained
in the cuvet. The optical path is fixed by the diameter of the cuvet.
Then the light is spectrally filtered to a narrow spectral bandwidth, to
obtain a light beam of intensity
I
o
or
I.
The photoelectric cell collects the radiation
I
that is not absorbed by
the sample and converts it into an electric current, producing a
potential in the mV range.
The microprocessor uses this potential to convert the incoming value
into the desired measuring unit and to display it on the LCD.
The measurement process is carried out in two phases: first the meter
is zeroed and then the actual measurement is performed.
The cuvet has a very important role because it is an optical element
and thus requires particular attention. It is important that both the
measurement and the calibration (zeroing) cuvets are optically identical
to provide the same measurement conditions. Whenever possible use
the same cuvet for both.
It is necessary that the surface of the cuvet is clean and not scratched.
This is to avoid measurement interference due to unwanted reflection
and absorption of light. It is recommended not to touch the cuvet
walls with hands.
Furthermore, in order to maintain the same conditions during the
zeroing and the measuring phases, it is necessary to close the cuvet to
prevent any contamination.
