The Problem:
Measuring the pH value in seawater using glass electrodes requires a specialized sensor design to avoid errors caused by the high ionic strength of seawater. When using conventional reference electrodes with ceramic diaphragms, issues can also arise due to the high and variable junction potentials that occur under pressure. For this reason, pH electrodes have previously only been offered for depths of up to 1,500 m.

In addition, using two channels of the probe system for pH measurement—one for the glass electrode and one for the reference electrode—proved to be somewhat cumbersome.

The solution: Versatile combination electrode for underwater probe systems – also flexible for standalone operation
The pH combination sensor consists of a reference electrode and a pH-sensitive glass electrode in one housing to save a free channel of the probe system. To enable accurate measurements even in the deep sea, a double membrane was used for the reference electrode to avoid problems with signal stability during pressure changes.

The Interface
The pH combination sensor for in-situ pH determination is available as a deep-sea version (up to 600 bar) without an integrated temperature sensor.