This Shallow SeaFET was deployed with a DuraFET that was already near the end of its 1-year lifespan. The failure occurred as the sensor naturally degraded towards the end of the deployment, most likely from depletion of the internal electrode’s electrolyte. The pH External values, originating from the solid-state external reference electrode, held true for the rest of the deployment. Previous datasets have shown error introduced from a defective DuraFET, but this particular failure is an expected result for an instrument that has not received the proper periodic maintenance.
Just as a car requires periodic oil changes, the SeaFET V2 and Shallow SeapHOx V2 require annual service, where the instruments receive a brand new DuraFET and recalibration. To work around the expected 1-year lifespan on the DuraFET, the Deep SeapHOx V2 is a viable option for both deep and shallow deployments — while it uses the same ISFET pH sensing technology, the Deep SeapHOx V2 does not use the DuraFET and therefore does not share the same 1-year lifespan.