The ozone meter / transmitter AQ-FM S900 is used to measure and control gas concentrations, and can communicate with a variety of hardware systems. The transmitter can also be used as switching relays with user-set values, as 4- 20 mA gas transmitter and it can communicatewith a networkvia the RS485 interface. Changing sensor heads is quick and easy, no configuration changes required. Calibration certificate included.