| 摘要 |
A positioning detector detects whether a workpiece has been positioned on a reference surface even when the pressure of a fluid supplied from a fluid pressure source and applied to the workpiece varies. A fluid is jetted from a nozzle toward a surface of the workpiece, and a back pressure of the fluid developed behind the nozzle is detected. A fluid pressure bridge is composed of the nozzle, a variable restriction, and a pair of fixed restrictions, and is connected to a semiconductor pressure sensor for detecting the difference between the back pressure and the pressure of a fluid vented through the variable restriction. The semiconductor pressure sensor has output terminals connected to a plurality of comparators for comparing the pressure difference detected by the semiconductor pressure sensor with respective different thresholds. Depending on the detected pressure difference, the comparators produce a different combination of output signals to selectively energize a plurality of light-emitting diodes for allowing the user to visually confirm the positioning of the workpiece with respect to the reference surface.
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