An ultraviolet sensor that may include a group of serially connected photovoltaic diodes of alternating polarities; a selective blocking portion that is configured to prevent ultraviolet radiation from reaching photovoltaic diodes that belong to the group and are of a first polarity, while allowing the ultraviolet radiation to reach photovoltaic diodes that belong to the group and are of a second polarity; and an interface for providing an output signal of the group, the output signal is indicative of ultraviolet radiation sensed by the photovoltaic diodes that belong to the group and are of the second polarity.