GB806606A - Automatic control system for the scanning of workpieces by ultrasonic or like probes - Google Patents

Abstract

806,606. Automatic position control systems. HIRSCHMANN, F. Nov. 2, 1956 [Nov. 3, 1955], No. 31452/55. Class 38 (4). Automatic control means for the non- destructive testing of a workpiece by a probe such as an ultrasonic transmitter-receiver comprises at least one electrode on the probe, the electrical conditions between the electrode and the workpiece, which are separated by a liquid, being used to maintain a fixed spatial relationship between probe and workpiece. As shown, an electrically conductive liquid such as a weak salt or acid is used, and the alternating currents from secondaries of transformer 17 passing between the workpiece 3 and electrodes 9 and 10 mounted on the ultrasonic probe 1 are rectified at 90 and 100 respectively and passed through control windings 91 and 101 of magnetic amplifiers 11 and 12 in such a way that the sum of the two currents is balanced against a pre-set current in winding 18 in amplifier 11 and the out-of-balance direct current from the bridge rectifier supplied to a split filed motor 6 which moves the probe to maintain a constant distance from the workpiece. Similarly the difference of the currents through electrodes 9 and 10 controls the motor 8 which rotates the probe to keep it at right-angles to the workpiece surface. A second pair of electrodes at rightangles to those shown may also be used, in cases where the workpiece cross-section varies in a direction perpendicular to the plane of the Figure. It is stated that an optical, radioactive or other probe may be used instead of an ultrasonic probe, and that the probe may be controlled by the voltage between electrode and workpiece instead of by the current.