Thermo Scientific AquaSensors
™
AnalogPlus
™
Contacting Conductivity Sensor User Guide
19
4.2.
Contacting Conductivity Sensor Troubleshooting
General Inspection
If the sensor is not providing reasonable signals to the analyzer, check the following:
1.
Inspect the integrity of the electrodes. If the electrode is broken, replace the sensor.
2.
Inspect the sensor cable for damage to the outer jacket. Any cuts or kinks may damage signal
connections.
3.
Inspect terminal block connections to be sure wires are not corroded or loose.
4.
Make sure all sensor wires are connected to the correct places on the analyzer terminal block. Depending
on the analyzer, some terminal block jumpers may be required and it is common to put those jumpers in the
wrong place.
5.
The sensor electrodes should be immersed in a solution of known conductivity solution.
6.
Establish that the analyzer electronics are working correctly by verifying operation with another sensor.
If the sensor passes the general inspection, there are four basic tests that can verify the Temperature
Measurement, the Conductivity Short Test, the Conductivity Span Test and the Sensor Power Test. If the
sensor passes these tests it should be ready for service.
Temperature Span
Disconnect the BLACK and YELLOW sensor wires from the analyzer. Use an ohmmeter to measure the
resistance between the BLACK and YELLOW wires. The meter should measure a resistance corresponding
to the sensor temperature as outlined in the following table.
Sensor
Temperature
5°C 15°C 25°C 35°C 45°C
Thermistor Resistance
1020
Ω
1058
Ω
1097
Ω
1136
Ω
1175
Ω
If the measured resistance is within 20 to 40 ohms of the expected value, the element should be satisfactory.
If not, please consult the factory.
If after cleaning and refurbishment sensors still have slow responses, low measurement
slopes or are seriously abraded or scratched, they must be replaced. Contact your local
distributor or call Thermo Fisher Scientific Customer Service.
