SRX-MA100-4 PPM Oxygen Sensor is a replacement to Analytical Industries GPR-12-100-4 PPM oxygen sensor. Its innovative design with electro-etched sensing cathode provides with extremely smooth sensing surface for excellent signal stability, very low noise and drift. This sensor, with its proprietary electrolyte formulation, enhances sensor performance at extreme ends of recommended operating temperature range. Sensor is designed, developed and manufactured in the USA.