pH Sensor
The operation of the pH sensor is based on a zirconia membrane and an Ni/NiO or Cu/Cu2 O electrode that measures the oxygen partial pressure of the testing solution. The pH is calculated using the Ag/AgCl reference electrode signal and temperature as additional input signals. The pH sensor can also be used as a reference electrode in an environment with a known pH. The operating temperature of the pH sensor is from about 180 °C to 360 °C, but the maximum operating temperature of the Ag/AgCl reference electrode limits the pH measurement to a temperature of 300 °C.
The zirconia pH sensor does not need calibration as it is "real" reference electrode and as the internal parts are never in direct contact with the operation environment. However, we have noticed that the E0Ni/NiO is not exactly the same in all the electrodes. Therefore, we prefer to calibrate the nickel oxide equilibrium potential in the factory before the shipment.
See more information of the zirconia electrode and its utilisation as a reference electrode!