Redox combination electrode for immersion sensors
• Only one housing for platinum and reference electrode
• Special double membrane for high signal stability
• For depths up to 6,000 m

The problem:

Redox potential measurement systems, consisting of a noble metal electrode and a reference electrode, are useful for the numerical determination of the reduction or oxidation potential of water samples. However, when measuring ORP in seawater, problems can occur if conventional reference electrodes with ceramic membranes are used, as high and variable junction potentials develop at high pressure. Therefore, redox potential measurement systems have previously only been offered for depths of up to 1,500 m. It was also somewhat cumbersome to use two free channels for redox measurements – one for the noble metal electrode and another for the reference electrode.

The solution:

A new combination electrode for submersible probe systemsThe redox combination sensor consists of a reference electrode and a noble metal electrode in one housing to save a free channel of the probe system. For accurate measurements in the deep sea, a special double membrane was used for the reference electrode to achieve better signal stability with pressure changes. The reference electrode/sample interface is implemented by means of a hole membrane. Inside the reference electrode there is a KCl-containing gel with a special built-in second membrane that contains the Ag/AgCl reference system in a KCl solution. The redox combination sensor for in-situ determination of redox potentials is available as a deep-sea version (up to 600 bar) without an integrated temperature sensor.