SUP-DO7016 Optical Dissolved Oxygen Sensor is based on luminescent optical technology. The Optical Dissolved Oxygen sensor is approved by the ASTM International Method D888-05 Features Range: 0.00 to 20.00 mg/LResolution:0.01Response time: 90% of the value in less than 60 secondsSignal interface: Modbus RS-485 (standard) and SDI-12 (option)Power supply:5 ~ 12 volts