MicroSet ORP Indicating Controller Transmitter Model MS OP 91 is used for various industrial applications. MS OP 91 is a convenient and cost effective solution for monitoring and maintaining ORP value. It can accept input from any ORP sensor. MS OP 91 output is in the form of Analogue 4-20 mA DC and Optionally MODBUS RS 485 RTU. Online ORP indication provided through LED is easily readable. 2 Nos Relay Outputs are provided to operate Alarm, Solenoid Valve, Pump etc. 4 Nos Setpoints for Relays can be programmed using Frontal Keypad.