Hach-Lange 3400 sc - Manual (Page 30)

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Troubleshooting
6.3 General Troubleshooting
6.4 Checking Sensor Operation
6.4.1 Sensors without the Integral Junction Box
Use the following troubleshooting steps for sensors without the integrated integral junction
box (Model: D3422, D3433, D3444, and D3455).
1. Disconnect the sensor from the analyzer or junction box.
2. Clean the sensor using the procedure in 5.2 "Cleaning the Sensor" on page 23 .
3. Using an ohmmeter, check all of the measurement point resistance readings shown in
Table 9: " Sensor Operations (Resistance) Checks for Models 3422 and 3455" ,
Table 10: " Sensor Operations (Resistance) Checks for Models 3433" , and
Table 11: " Sensor Operations (Resistance) Checks for Models 3422 and 3455" .
Make sure that the ohmmeter is set to its highest range for all infinite (open circuit)
resistance readings.
4. If you cannot get the required readings for one or more of the resistance check or if
the sensor still does not operate when the resistance checks are okay, contact
Technical Support for more troubleshooting options.
Problem Resolution
Reading is unstable Clean and calibrate sensor
Table 9: Sensor Operations (Resistance) Checks for Models 3422 and 3455
Measurement Points Correct Resistance Readings
Between blue and white wires 1089–1106 ohms at 23–27 °C
Between red wire and sensor body Less than 5 ohms
Between black wire and inner electrode Less than 5 ohms
Between black and red wires Infinite (open circuit)
Between black and white wires Infinite (open circuit)
Between red and white wires Infinite (open circuit)
Between red and inner shield wires Infinite (open circuit)
Between black and inner shield wires Infinite (open circuit)
Between white and inner shield wires Infinite (open circuit)
Between outer and inner shield wires Infinite (open circuit)