The ME4-O3-E4 sensor is a constant-potential electrolytic-type ozone (O3) sensor. Ozone and oxygen undergo corresponding redox reactions at the working and counter electrodes, releasing electrical charges to generate a current. The magnitude of this current is directly proportional to the O3 concentration, allowing for the determination of O3 levels by measuring the current. The sensor features a fourth electrode—an auxiliary electrode—used to compensate for the zero-point current, resulting in a device characterized by a strong signal output and a low zero-point current.