The AP121 is a highly process-resistant 12 mm combination pH / redox (ORP) electrode. It is equipped with a rugged solid electrolyte providing an effective shield to process poisons and fluctuating pressures. The electrode has all 3 measuring elements located closely together and a very fast temperature response. This ensures high integrity calibration and tighter control. Already a number of years in service, the proven multi-pole VP connector enables easy connection / disconnection of multi-parameter sensor signals.