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If the monitor fails to produce results as expected, the most likely cause is the standards, either contaminated when handled or
(and most likely) made up with poor quality water, possibly containing background phosphate. Incorrectly prepared reagent may
give a poor calibration factor. If the solutions are purchased from a proprietary chemical supplier, take care in storing the
containers; they should be date stamped, used in strict rotation, and not used after their expiry date.
8.4.3 Effects of Loss of Power to the Monitor
The action taken by the monitor following an unforeseen loss of power is dependant on the length of time the power was off.
Table 8.2 shows the alternative actions performed by the monitor.
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8.5 Simple Checks
Note.
• All references to 'Programming Pages' are found in
Section 6 for single stream versions of the monitor.
Before carrying out tests on the multi-stream version, it
is essential that only one stream is selected – see
Section 4.3.
• On single stream versions always start any fault finding
investigations by disabling the color compensation in
Programming Page 3.3. On multi-stream versions
always put into single stream mode – see Programming
Page 3.3.
8.5.1 Unstable or Erratic Readings
a) Check the flow of sample into the cuvette.
b) Check the flow of the reagent through the pump.
c) Check that the pinch tube is fitted correctly into the pinch
valve.
d) Ensure that the drain/fill cycle is taking place normally.
Illumination can be seen via the plastic prism on the top of
the lamp housing – see Fig. 8.3.
e) Ensure that the cuvette overflows through the bottom left
hand outlet tube before the lamp lights during each drain/
fill cycle.
Important Note. It cannot be stressed strongly
enough that the five-weekly chemical rinse with the
ammonia/detergent solution is vitally important. It is also
very effective at reducing calibration problems, drift and
signal noise. Any evidence of white or blue precipitate in
the mixer or reaction coil must be removed with the rinse
solution.
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Table 8.2 Effects of Loss of Power to The Monitor
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Reference Photocell
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Lamp
Mounting
Plate
A – Card between Lamp Housing and
Thin Card
B – Card between Lamp Housing and Reference
Fig. 8.3 Simple Electronic Response Test
f) Rinse the pipework for 30 minutes with cleaning solution
(see Section 8.2.4) to remove any build-up of molybdate
precipitate.
g) Carry out a monitor response test – see Section 8.4.4.
8 MAINTENANCE...
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Plastic
Lamp
Measuring
Prism
Housing
Measuring Photocell
Thin Card
Measuring Cuvette
Photocell Housing
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Cuvette
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31
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