Abstract: A method and an apparatus for detecting the internal cavities in a continuous casting bar in which two opposite surfaces of a casting bar delivered from a continuous casting machine are held between a pair of rollers each having a hollow portion and are pressurized at a predetermined pressure thereby, and an amount of transmission of an ultrasonic wave having a predetermined frequency passing through the casting bar is detected by means of an ultrasonic wave device for transmission and an ultrasonic wave device for reception which are provided respectively in the hollow portions of the rollers to allow the ultrasonic wave to pass through the casting bar running through the rollers, thereby to detect the internal cavities in the casting bar.

Abstract: The present invention relates to an apparatus for precise measurement of the length of long length materials which measures the length of a long length material such as electric wire, cable, etc. basically unit length by unit length in an inchworm manner by applying magnetic marks on said material and sensing them downstream while making correction for elongation of the material due to temperature and tension, and which measures only an odd length less than the unit length by means of, for example, a counter wheel.