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FUNCTIONAL DESCRIPTION
1) Primary LCD:
When the meter is switched on, the LCD
shows all segments for a few seconds.
It then displays four dashes to indicate
“ready to measure”.
In “Read” and “Zero” mode, “SIP” is shown
to indicate “Sample In Progress”.
The upper level also indicates the concen-
tration or turbidity value of the sample, as
well as different diagnostic modes, such
as “-BA-” for low battery.
A substance absorbs a color complimentary
to the color it emits. For example, a
substance appears yellow because it absorbs
blue light. As a result, the Hanna meters use
LED’s with specific wavelengths to measure
samples.
The optical distance (d) is measured by the
internal diameter of the cuvet containing the
sample.
The photoelectric cell collects the radiation
I
that is not absorbed by the sample and
converts it into an electric current.
The microprocessor converts the value into
the desired measuring unit and displays it on
the LCD.
The measurement process is done in two
phases: setting the meter to zero and actual
measurement.
The cuvet is an optical element and hence
has an important role in the measurement
process. Both the measurement and the
calibration cuvets must be optically identical
to provide the same measurement conditions.
It is also important that the surface of the
cuvet is clean and free from scratches or
dents, in order to avoid measurement
interference due to unwanted reflection and
absorption of light.
It is recommended that wherever possible the
cuvet walls are not touched by the operator.
Furthermore, in order to maintain the same
conditions during the zeroing and the
measuring phases, it is necessary to close
the cuvets to prevent any contamination.