Capacitive thread surface flaw detector - with electrodes flanking sample and coupled to HF generator and measuring circuit

摘要

Device detecting surface defects on thread-like articles, e.g. boron or silicon carbide threads, synthetic fibres or microwires, includes a capacitive pick-up. A housing (1) encloses a cylindrical screen (2), made of conductive material, with two electrodes (3,4) inside flanking the test thread (10). The electrode (3) is connected to a high-frequency generator (5) and is at a high potential. The electrode (4) is coupled to the measuring circuit (6) and is at a low potential. The measuring circuit has a common neutral junction (0) with the high-frequency generator which is also the potential for the screen (2). The measuring circuit consists of a high- frequency amplifier (7), a threshold element (8) and a pulse counter (9). This reveals microdefects of less than 100 microns and simplifies design.