Abstract: A pH sensing that is configured to be exposed to a process fluid is provided. The pH sensing probe includes a sensor body and a pH glass electrode mounted to the sensor body. A reference electrode has a junction mounted to the sensor body that is configured to be exposed to the process fluid. A backup pH electrode is mounted to the sensor body and configured to be exposed to the process fluid. A pH sensing system and a method of operating a pH sensing system are also provided. In one example, the backup pH electrode is an ISFET electrode that can be automatically switched to when the pH glass electrode is compromised.

Abstract: A pH sensing probe configured to be exposed to a process fluid is provided. The pH sensing probe includes a sensor body and a pH electrode mounted to the sensor body. A primary reference electrode is mounted to the sensor body and has a primary reference junction that is configured to be exposed to the process fluid. A secondary reference electrode is mounted to the sensor body and has a secondary reference junction configured to be exposed to the process fluid. A seal isolates the secondary reference junction from the process fluid until deterioration of the primary reference junction. A pH sensing system and a method of operating a pH sensing system are also provided.