VII. MAINTENANCE AND CLEANING
The quality of the water greatly eff ects the frequency of cleaning that is required. Cleaning requirements
will be diff erent at each installation. Visually checking the condition of the electrodes regularly is the best
way to determine the required frequency of cleaning.
1. Inlet Filter Screen
: Some installations may require an inlet fi lter screen to fi lter large particles out of
the sample water. If there is an inlet fi lter screen installed, regularly check the inlet fi lter screen and
condition. If it is found to be dirty, then clean it with clean water before reinstalling.
2. Flushing the Measurement Cell:
If water will not fl ow through the measurement cell and their is a
visable blockage then follow this procedure to fl ush it:
a. Turn off the power to the monitor.
b. Remove the fl ush plug in the fl ow cell and allow to drain.
c. Reinstall the fl ush plug.
d. Repeat as necessary before turning the power back on.
3. Thermistor:
If the thermistor fails, then it will give a very high or very low signal. To test the
thermistor, follow this procedure:
a. Turn off power to the monitor.
b. Open the monitors NEMA 4x enclosure and remove the two thermistor wires from the MB128
board (RS1 and AIC).
c. Use an ohm meter to check the resistance of the thermistor. If the ohm meter shows a stable
resistance reading around 10 kohms, then the thermistor is not defective. If the reading is zero or
infi nite, the thermistor is defective and must be replaced.
d. After replacement, thermistor recalibration may be required.
e. If the thermistor fails, the monitors temperature mode can be set to “Manual” to allow for proper
operation until a replacement thermistor is installed.
4. pH Electrode:
The pH electrode will periodically require replacement. The frequency of replacement
is dependent on the quality of the water. Also, all handling instructions must be followed carefully to
avoid damaging the pH probe. Failure of the pH probe can be indicated by an excessively high or low
reading. If the probe cannot be recalibrated, then it must be replaced. Instructions for replacement
will be included with the replacement pH probes available from Hydro Instruments.
Refer to sections I.1, II.4, VI, and Troubleshooting of this manual.
5. ORP Electrode:
The ORP electrode will periodically require replacement. The frequency of
replacement is dependent on the quality of the water. Also, all handling instructions must be followed
carefully to avoid damaging the ORP electrode. Failure of the ORP electrode can be indicated by
an excessively high or low reading. If the probe cannot be recalibrated, then it must be replaced.
Instructions for replacement will be included with the replacement ORP electrode available from
Hydro Instruments.
Refer to sections I.1, II.4, VI, and Troubleshooting of this manual.
6. Conductivity Electrode:
The conductivity electrode will periodically require replacement. The
frequency of replacement is dependent on the quality of the water. Also, all handling instructions
must be followed carefully to avoid damaging the conductivity electrode. Failure of the conductivity
electrode will be indicated by an excessively high or low reading. If the probe cannot be recalibrated,
then it must be replaced. Instructions for replacement will be included with the replacement
conductivity electrode available from Hydro Instruments.
Refer to sections I.1, II.4, VI, and Troubleshooting of this manual.
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