Patent ID: 7727370

Claim:
A system of measuring pH value in a solution, comprising a first pH sensor which is an extended gate field effect transistor structure, comprising: a first metal oxide semiconductor field effect transistor (MOSFET); a first extended gate as a first sensing unit, comprising a first substrate, and a first solid-state conductive layer thereon; and a first conductive wire connecting the first MOSFET and the first sensing unit. a second pH sensor as a reference pH sensor supplying stable voltage, comprising: a second metal oxide semiconductor field effect transistor (MOSFET); a second extended gate as a second sensing unit, comprising a second substrate, a second solid-state conductive layer thereon, and a polypyrrole layer on the second solid-state conductive layer; and a second conductive wire connecting the second MOSFET and the second sensing unit; a semiconductor characteristic instrument connecting the first pH sensor and the second pH sensor respectively; a temperature controller comprising a temperature control center, a thermocouple, and a heater, wherein the temperature control center connects the thermocouple and the heater, respectively; and a light-isolation container isolating the sensing unit of the second pH sensor from photosensitive effect; wherein measurement of pH value of a solution comprising: pouring a solution into the light-isolation container; immersing the sensing unit of the first and the second pH sensors, and the thermocouple in the solution; adjusting temperature of the solution by the heater controlled by the temperature control center after detecting temperature variation in the solution by the thermocouple; transmitting measurement data from the first and the second pH sensors to the semiconductor characteristic instrument; and reading out current-voltage (I-V) values of the solution by the semiconductor characteristic instrument to obtain pH value of the solution.