APPARATUS AND METHOD FOR DETECTING CRACKS IN METAL ARTICLES

摘要

An apparatus suitable for use in detecting cracks or other discontinuities in metal articles includes a plurality of spaced-apart eddy current probes (4), each having a probe end (9) for contacting the article, supported by a common housing (6). Helical compression springs urge each probe (4) towards an extended position in which all the probe ends (9) lie outside the housing (6), and in which each probe end (9) is independently movable towards the housing (6) against the action of the springs (50). Each eddy current probe (4) forms at least part of an inductive load (84) of a respective, independent, self-oscillating circuit (80) which circuit (80) provides an output voltage (Vout) which varies with the oscillatory state of the self-oscillating circuit (80) being adjustable by an input voltage (Vin). This apparatus is particularly suitable for checking quickly and efficiently the large areas of metal that form large typical food processing vessels, such as milk holders and the like.