What types of anti-fouling systems can I use for my ISFET-based pH sensor?

A vented copper cover over the sensor can provide some protection against biofouling. There is a copper antifoul guard available for standalone SeaFETs that covers the sensing surfaces.

If you use a SeapHOx system, the conductivity cell on the SBE 37-SMP comes equipped with TBTO antifoul devices at the sample intake and exhaust. These devices provide a further degree of fouling protection for the ISFET sensor in the pumped flow path. For best results, we recommend replacing the TBTO antifoul devices before each deployment.

There are some antifouling systems that are not recommended.

Electro-chlorination systems
We recommend against electro-chlorination systems. Stray currents in the water could damage the ISFET. In addition, applying electrical potential can disrupt the feedback loop between the ISFET and the counter electrode, causing unreliable pH measurements. Electro-chlorination systems also generate multiple ionic species in seawater, not just chlorine, which can alter the pH of the sample and result in inaccurate measurements. In general, we do not recommend installing an ISFET pH sensor inline with or downstream from a seawater electrolysis system.

UV antifouling systems
We also recommend against UV antifouling systems when using a SeaFET. There is a risk of exposing the ISFET chip to UV radiation, which can cause damage.