GB952074A - Improvements relating to measuring methods and apparatus - Google Patents

Abstract

952,074. Magnetic tests. DAVY & UNITED ENGINEERING CO. Ltd. July 26,1961 [July 26, 1960], No. 25946/60. Heading G1N. The elongation of magnetisable material as it passes through rolling means is determined by magnetising parts of the material at first points on the entry and exit sides of the rolling means, and generating electrical signals as the magnetised parts pass further points on the entry and exit sides, the magnetising taking place simultaneously with the generation of a signal at one of the further points, whereby the time separation of the signals is a measure of the elongation, and of the difference in speeds of the material at either side of the rolling means. Steel strip 5 passes between rollers 6 and passes close to transmitters 12, 12<SP>1</SP>, which magnetise the strip, and receivers 7, 7<SP>1</SP> which generate signals as magnetised parts of the strip pass them. Signals from receiver 7 pass through amplifier 8, pulse shaper 9, triggered pulse generator 10 and power amplifier driving circuit 11 to transmitter 12, so that pulses are generated continuously at a frequency depending on the speed of the strip and the separation of the transmitter and receiver. These pulses are fed through a D. C. restoring circuit 13 and a low-pass filter 14 to an indicator 15 measuring the ingoing strip speed. The system is triggered by a freerunning pulse generator 16 (e.g. at 1 pulse/sec.), below the minimum frequency (e.g. 3 pulses/sec.) of the speed measuring apparatus, generator 16 being biased off by bias amplifier 17 once the apparatus has been started. Generator 10 also operates transmitter 12<SP>1</SP>, and the separation of each transmitter from its corresponding receiver is made the same. The pulses generated by receiver 7<SP>1</SP> are fed through amplifier 8<SP>1</SP> and shaper 9<SP>1</SP> to pulse generator 10<SP>1</SP>, and the outputs from generators 10, 10<SP>1</SP> are fed to a pulse generator 18, which produces pulses whose width is proportional to the time separation of the input pulses. These pulses are applied through a D. C. restoring circuit 19 and filter 20 to an indicator 21 giving a signal proportional to the product of pulse width and pulse frequency, which is substantially proportional to the elongation of the strip, for small elongations. In a modification, suitable for measuring large elongations,transmitter 12 and receiver 7 are placed at the output side of rollers 6 and units 7<SP>1</SP>, 12<SP>1</SP> at the input side so that the frequency of the pulses applied to both transmitters is proportional to the outgoing strip speed, instead of the ingoing speed. A switch 22 is provided for zero-point calibration and checking purposes.