Abstract: A portable leak detector includes a housing having an inlet and an outlet each in fluid communication between an interior and an exterior of the housing. A gas sensor, having a property that changes in response to exposure of the gas sensor to one or more gases, is positioned in fluid communication with the interior of the housing via the inlet thereof. The leak detector includes a probe lamp, a plurality of first indicator lamps supported by the housing and a speaker supported by the housing. A controller supported by the housing is connected to detect the property of the gas sensor. The controller causes the probe lamp to flash at a first frequency, causes a first group of the plurality of first indicator lamps to illuminate, and/or causes the loudspeaker to chirp at a second frequency all as a function of a detected property of the gas sensor.

Abstract: Photo plotter aperture members each have a beam forming trasnsparent ring and a central transparent cross in communication with the ring. The rings of the different members are of different diameters but of the same thickness as the lines of the respective crosses to provide uniform exposure during half diameter strokes of the aperture members.