How does the ISFET probe obtain a pH reading?
IQ Scientific Instruments ISFETs, referred to as “FET” sensors, are silicon chips that have several proprietary layers selectively deposited on a silicon substrate. The final layer has an affinity only for hydrogen ions. Hydrogen ions determine pH. The quantity of hydrogen ions at or near the sensor surface causes an electrical effect that can be detected and measured by the appropriate instrumentation, thus pH is then very precisely derived.
