This UV monitor is a true 254nm ultraviolet sensor incorporating individual calibration boards which allows for field replacement of sensor only, if necessary. Audible and visual indicators are included as integral components.The Viqua 254NM-C1 is the UV assembly for the Cobalt™ "Plus" series. This sensor reads 254nm from a low pressure high output UV lamp. The 254NM-C1 comes complete with an integral calibration board and 3' of sensor cable with a water-tight connection. Note: The 254NM-C1 can only be used on the Cobalt™ "Plus" series.