Measurement of the wall thickness of a tube in a mandrel mill by using laser ultrasound technique

摘要

Pipe (1) wall thickness measurement method wherein an ultrasonic pulse is excited in the pipe wall by an excitation laser. Its time of flight, and therefore the wall thickness, is determined using an interferometer (4). To maximize measurement accuracy the positions of the interferometer mirrors (6, 7) are regulated using a linear actuator in conjunction with a control signal derived from a photo-diode (9) and a regulator (10). The photo-diode signal is adjusted using an amplifier (15) to temperature compensate the mirror positions using the signal from a pyrometer. The invention also relates to a corresponding device for method implementation.