The MED-NO electrochemical nitric oxide sensor is a potentiometric electrolytic sensor. Nitric oxide and oxygen undergo corresponding redox reactions at the working and counter electrodes, releasing corresponding charges and forming a current. The magnitude of the current is proportional to the gas concentration and follows Faraday's law. The concentration of nitric oxide can be determined by measuring the magnitude of the current. The fourth electrode of the sensor, the auxiliary electrode, is the same as the working electrode but is not exposed to the target gas; it is used for zero-point compensation.