Hach 3700 Série Manuel D'utilisation De Base page 23

Personal injury hazard. Removal of a sensor from a pressurized vessel can be dangerous. Installation and
removal of these sensors should be done by individuals trained in proper high pressure and temperature
installation. Always use industry approved hardware and safety procedures when dealing with high pressure
and/or temperature fluid transport systems.
Pre-requisite: Prepare a mild soap solution with warm water and dishwashing detergent, Borax
hand soap or a similar soap.
Examine the sensor periodically for debris and deposits. Clean the sensor when there is a buildup of
deposits or when performance has degraded.
1. Use a clean, soft cloth to remove loose debris from the end of the sensor. Rinse the sensor with
clean, warm water.
2. Soak the sensor for 2 to 3 minutes in the soap solution.
3. Use a soft bristle brush to scrub the entire measuring end of the sensor. Scrub the inside of the
toroid.
4. If debris remains, soak the measuring end of the sensor in a dilute acid solution such as < 5%
HCl for a maximum of 5 minutes.
5. Rinse the sensor with water and then return to the soap solution for 2 to 3 minutes.
6. Rinse the sensor with clean water.
Always calibrate the sensor after maintenance procedures are done.
Section 8 Troubleshooting
8.1 Intermittent data
During calibration, data is not sent to the datalog. Thus, the datalog can have areas where the data is
intermittent.
8.2 Test the conductivity sensor
If a calibration fails, first complete the maintenance procedures in
1. Disconnect the sensor wires.
2. Use an ohmmeter to test the resistance between the sensor wires as shown in
Note: Be sure that the ohmmeter is set to its highest range for all infinite (open circuit) resistance readings.
Measurement points
Between red and yellow wires
Between blue and white wires
Between green and yellow wires
Between white and shield wires
If one or more of the measurements is incorrect, call technical support. Supply technical support with
the serial number of the sensor and the resistance values measured.
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An infinite value (open circuit) or 0 ohms (short circuit) identifies a failure.
W A R N I N G
Table 5 Conductivity resistance measurements
Maintenance
Resistance
1090–1105 ohms at 23–27 °C
Less than 5 ohms
Less than 5 ohms
Infinite (open circuit)
on page 22.
Table 5.
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