| 摘要 |
A linearly slidable sensing member having a tungsten carbide tip is operatively connected to a linear variable differential transformer (LVDT), and mounted on an adjustable bracket so that it is in continuous contact with an edge of a web. A d.c. electrical signal of a given voltage is generated by the LVDT depending upon the position of the sensing member with respect to a point that is stationary relative to the machine. The signal is compared to a reference d.c. voltage by a pair of differential voltage comparators, and depending upon the voltage of the signal relative to predetermined adjusted reference voltage levels one of three indicating lights is energized. Apparatus for energizing the lights may include switching amplifiers connected to each output of the differential voltage comparators, a triple exclusive OR gate, and a transistor connected to the output of each gate of the triple exclusive OR gate.
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