Aquaprobe
®
AP-700, AP-800 & AP-2000 Instruction Manual
10401-00870 Rev R
16. Optional Optical Electrodes Calibration and Maintenance
The Aquaprobe
®
is constructed with an aluminium sleeve surrounding the delicate sensing
electrodes. The Sleeve can be easily removed by unscrewing to allow cleaning of the
individual electrodes, however,
the Probe sleeve forms an integral, working part of the
Probe’s measurement system, and MUST be fitted for correct operation.
All Aquaread
®
Optical Electrodes are incredibly sensitive. For example, the Turbidity
electrode is capable of measuring between 0 and 3000NTU with an internal resolution of
greater than 0.1NTU. This means that the electrode is able to detect changes in turbidity
that are less than 0.003% of the full range! The other optical electrodes have a similar level
of sensitivity.
It follows, therefore, that in order to provide stable, repeatable readings, the environment in
which the measurements are made must be completely stable and repeatable.
For this reason, the Aquaprobe
®
is
constructed with a matt black
aluminium sleeve and end cap that
enclose the sensing electrodes and
provide a closed, constant condition,
non reflective measurement
chamber.
This is essential for the correct
calibration and operation of all
types of optical electrodes.
A diagram of the Aquaprobe’s
measurement chamber is shown
here.
In order to obtain consistent results, the measurement chamber created within the
Aquaprobe
®
must remain physically constant during both calibration and
measurement.
If the optical electrode is calibrated under one set of conditions then used to measure under
another set of conditions, the readings will naturally be erroneous, especially at low
concentrations.
A perfect example of this is calibrating with the end cap removed then measuring with the
end cap fitted (or vice-versa). By changing the physical characteristics of the measurement
chamber, you also change the calibration and response of the electrode.
Always zero the optical electrodes just prior to use in clean water (bottled still mineral water
is ideal) then deploy
without disturbing the measurement chamber
. This is especially
important when using the Turbidity electrode, which can display negative readings if the
zero point is not correctly calibrated.
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®
Ltd.
www.aquaread.com
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