Aqua Metrix P/R65 Руководство по эксплуатации - Страница 11
Просмотреть онлайн или скачать pdf Руководство по эксплуатации для Измерительные приборы Aqua Metrix P/R65. Aqua Metrix P/R65 20 страниц. Differential 2-wire (4-20 ma) ph & orp probes
Печатать страницу5.2.
Troubleshooting
A pH or ORP probe is a simple instrument. As a potentiometric device it outputs a voltage in
response to a change in pH or ORP. The built-in transmitter converts the voltage to a current. A
probe that is not functioning properly will output a current that is out of range of the specifications
listed in Section 5.1.
The change in output with calibration standard constitutes the span.
For a pH probe: The span between pH 4 and pH 7 or between pH 7 and pH 10 should be between
2.85 and 3.99 mA.
The ORP sensor is unique in that the voltage is the ORP reading. There is no span between
readings of two calibration solutions. However mA readings should be within the ranges stated in
Section 5.1.
If the span of an pH probe or the absolute mA readings of an ORP probe do not satisfy these criteria
then the cause of the problem may be one of the following:
1. The process electrode (glass bulb) is coated with scaling or biofouling.
2. The process electrode is inoperable (likely broken).
3. The reference solution has been contaminated with the process to the point that it is no longer
pH 7.
4. The salt bridge has fouled to the point that reference solution cannot pass through that is
needed to complete the potentiometric circuit.
5. The printed circuit board (PCB) has shorted out by ingress or the op-amp on the board has
failed.
The manifestations of these different sources are as follows:
1. A coated electrode (1) will create a narrower span or reduced ORP readings. If the coating is
from scaling then soaking the probe in a weak acid (e.g. vinegar or 0.1 N HCl) will remove the
scale. If the coating is from fouling then soaking the probe in bleach will clear it.
2. Either problems 2 or 5 If the pH or ORP reading does not change when changing from one
calibration solution to another then either the cause is a failed PCB (5) or broken electrode (2).
3. A contaminate reference solution (3) will result in both a lower span and higher offset for pH
probes or an erroneous ORP reading.
4. A fouled salt bridge (4) will result in a slower response but not necessarily a narrower span or
inaccurate ORP readings. AquaMetrix sells replacement salt bridges at very modest pricing.
5.3.
Customer Service
If a problem has not been resolved with the above procedures, a telephone consultation with your
AquaMetrix representative, or directly with Water Analytics will provide the answer.
Water Analytics
100 School Street
Andover, MA 01810
978-749-9949
If you are returning a probe for inspection, enclose description of the problem. Pack the probe
adequately to avoid damage to the glass electrode and ensure that it will not be exposed to
temperatures below –5°C. Water Analytics cannot be responsible for shipping damage nor for
damage due to frozen electrodes. For safety reasons, Water Analytics cannot accept probes which
have not been thoroughly cleaned to remove all process material.
P/R65
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