An ISFET chip pH sensor has three main components:
ISFET chip—The ISFET chip is made of durable plastic and contains three electrodes: the source, the drain, and the gate. The gate is the ISFET chip’s only electrode that comes in contact with the sample solution.
Reference electrode—Inside the reference electrode’s membrane, there is a silver wire element submersed in an electrolyte solution. The reference electrode, as a whole, is submersed in the sample solution.
Reference junction—The reference junction is located at the end of the reference electrode by the sample solution. It interacts with both the reference electrode’s electrolyte solution and the sample solution to complete the electrical circuit.