Troubleshooting - Hach pHD Sensor User Manual

Troubleshooting

Test the sensor
Pre-requisites: Two pH buffers (pH 7 and pH 4 or pH 10) and a multimeter.
Note: If a calibration fails, clean the sensor and replace the salt bridge and standard cell solution, and then repeat
the calibration. Only test the sensor if the problem is not corrected by maintenance.
1. Put the sensor in a pH 7 buffer solution and wait for the temperature of the sensor and buffer to
reach room temperature.
2. Disconnect the yellow and black sensor wires from the gateway.
3. Measure the resistance between the yellow and black wires to verify the operation of the
temperature element. The resistance should be between 250 and 350 ohms at approximately
25 ºC.
If the temperature element is good, reconnect the wires to the gateway.
4. Push the MENU key and select Sensor Setup, Diag/Test, Signals. The pH reading should be
between –50 and + 50 mV.
5. Rinse the sensor with water and put in a pH 4 or pH 10 buffer solution. Wait for the temperature
of the sensor and buffer to reach room temperature.
6. Compare the mV reading in the pH 4 or 10 buffer to the reading in the pH 7 buffer. The reading
should differ by approximately 160 mV.
If the difference is less than 160 mV, call technical support.
Diagnostic and test menu
The diagnostic and test menu shows current and historical information about the chlorine analyzer.
Refer to Table 2. To access the diagnostic and test menu, push the MENU key and select Sensor
Setup, Diag/Test.
Option
GATEWAY INFO
CAL DAYS
CAL HISTORY
RST CAL HISTORY
SIGNALS
SENSOR DAYS
RST SENSORS
CALIBRATION
16 English
Table 2 DIAG/TEST menu
Description
Shows the firmware version, driver version, serial number and boot version for the
controller and the types of sensors connected to the controller.
Shows the number of days since the sensor was last calibrated.
Shows a list of the times when the sensor was calibrated. Push ENTER to scroll
through the entries and view a summary of the calibration data.
Resets the sensor calibration history. Requires passcode.
Shows the sensor measurement signal value in mV.
Shows the number of days the sensor has been in operation.
Resets the sensor days and calibration days to default. Requires passcode.
Shows the slope and offset values for chlorine and pH. Shows the offset value for
the temperature.