A pre-set ultraviolet dose meter

The design, construction and performance of an ultraviolet radiation (UVR) pre-set dose meter is described. The meter simultaneously displays irradiance, dose, and elapsed time, and incorporates a calibrated variable gain control to permit use with detectors of varying sensitivity. The meter has been developed to permit the automatic administration of UVR dose in photosensitivity testing. The UVR is generated by a Xenon lamp and delivered to the patient via a monochromator and liquid filled light guide. A beam-splitter in the light guide applicator diverts a small fraction (9%) of the UVR onto a photo-diode detector connected to the meter. When the dose recorded by the meter reaches the pre-set value the meter activates a solenoid which closes the monochromator exit slit shutter. This on-line control of the dose ensures that any fluctuations in irradiance are compensated so that the pre-set test dose is always administered to within the 1% accuracy of the instrument.