Abstract: The positions of objects in a holder, such as a cassette containing semiconductor wafers, are determined by a system that projects a pair of coplanar light beams through the cassette from one side. A reflector on the opposite side reflects both light beams back though the cassette and onto separate photodetectors on the one side. A computer analyzes signals from the photodetectors as the cassette is moved through the light beams. As the cassette moves the light beams are interrupted by the wafers. The relative widths and timing of pulses in the signals indicate the location of wafers in the cassette and whether a wafer is misaligned.

Abstract: An electrically heated humidifying apparatus includes a humidifier element detachably secured to a humidifier heater with the base of the humidifier element in engagement with the electric heating plate of the humidifier heater. The humidifier element is secured to the humidifier heater by an intermediate adaptor having a ring portion with spaced lugs interfitting with correspondingly spaced lugs on the humidifier heater and a horse-shoe shaped portion adapted to slidably receive the humidifier element and engage with an annular shoulder on the humidifier element.

Abstract: An electronic device comprises a casing having a temperature sensor mounted therein with insulated sensor-connecting wires of considerable length being exposed to the environment on an external surface of the casing which is covered over the wires with a thin metallic coating.