The Rosemount 490A optical dissolved oxygen sensor is a digital Modbus-enabled measurement device designed to provide accurate readings within 90 seconds of transition from dry to wet conditions. It can be used in process media in both liquid and gas phases without requiring separate calibrations. The Rosemount 490A employs EPA-approved luminescence-quenching technology, eliminating the need for electrolyte refills and significantly reducing maintenance requirements. It is IP68-rated and boasts a small form factor coupled with forward and rear facing 1-in NPT threaded connections. The 490A uses an optical sensor, which does not consume oxygen or require water flow for accurate measurements. Guard cap options provide weighted orientation, anti-fouling protection and air blast cleaning. The sensor is accurate to ±0.1 milligram per liter (0 to 20 mg/L) and ±2% (20 to 60 mg/L).