GB1384019A - Sensing apparatus - Google Patents

Abstract

1384019 Proximity detector systems ENGINEERING DESIGNS (IPSWICH) Ltd 14 June 1973 [15 June 1972] 27938/72 Heading G1N A capacitative detector is used with an e.g. pneumatic conveyer system for detecting the passage of articles such as transistors to control a machine or a counter. As shown Fig. 2, a tube 8 passes through a housing 2a, 2b. Foil detector electrodes 10, 11, and guard rings 12 surround the tube, and are connected to an electronic circuit block 16. The tube 8 may be adapted for insertion as part of the conveyer system, or may slide over the conveyer tube. In the circuit unit Fig. 3, (not shown), the senser is connected in a capacitance bridge energized by a square wave oscillator (19). The bridge output is amplified and rectified to extract the modulation pulse, due to the passage of an article, which is applied to a trigger circuit to provide a substantially constant size output pulse. Modifications:- It is suggested (i) that the measuring circuit might be D.C. and a galvanometer or A.C. and an ammeter, (ii) one side of the bridge circuit may be removed leaving a simple capacitance divider in Fig. 3.