Abstract: The invention relates to measuring the ultra-violet radiation received from tubular ultra-violet source mounted within a quartz sleeve, the radiation passing through water within a tubular circuit coaxial with the source and sleeve. A sensor probe fits within a socket formed in the wall of the conduit. The probe comprises a plane quartz window at one end and an ultra-violet sensor tube at the other end. Radiation from the window passes through an iris, whose size and position are chosen so that the source projects an image through the iris which is at least twice the size of the sensitive area on the sensor. In order to minimize inconsistencies due to faulty positioning of the sensor tube, the axis of the tube is preferably at right angles to the axis of the source. The output of the sensor is connected with a logic circuit which has means for providing a multi-state indication of radiation within the conduit.

Abstract: The invention relates to apparatus 1 for monitoring the intensity of a UV source, for example a water sterilizer, in which there is an optical detection unit (2) which detects UV radiation and converts that radiation into an electrical signal which is comparable to the intensity of the UV radiation detected, the optical detection unit (2) being operatively connected with a device including a converter (8) and adapted to indicate the intensity of UV radiation from the source dependent on the electrical signal from the optical detection unit.