Ultraviolet intensity sensor for the Trojan UVMax F, in the version supplied for the black-housing build of that system. A UV intensity sensor reads the germicidal output actually reaching the water at 254 nm, which is the only direct evidence that the reactor is still delivering its validated dose. Lamp output falls with age and quartz sleeves foul, and both show up here before they show up anywhere else, so the controller alarms on this reading rather than on lamp hours alone. The UVMax F was produced in more than one hardware generation and the sensor is not common across them, which is why the housing colour is quoted: check the colour of the controller housing on the system being worked on before ordering. Contact us if you are unsure whether this part fits your UV system.