APPARATUS FOR DETECTING SLOWLY CHANGING CHARACTERISTICS OF MOVING YARN

摘要

1,116,213. Determining a quality of a material photo-electrically. C. GUNN-RUSSELL. June 21, 1965 [June 16, 1964], No.24992/64. Heading G1A. An apparatus wherein a quality is determined by optical scanning and which results in the production of a signal having frequency components between f and F modulated on a carrier, comprises an amplifier for the modulated carrier signal, a demodulator, a quality fault response device, and a circuit substantially non-responsive to frequency components greater than f connected as a reference signal so as to minimize the response of the device to long term changes at the output of the transducer. A yarn 16, Fig. 4 (not shown) runs through a head past the radiation from a light source such as a gallium arsenide emitter driven by an oscillator at the carrier frequency, and the electrical signal developed on a photo-diode 17 is applied to operate a relay and thus a cutting device through an amplifier and a differential circuit such as Fig. 1 in which the positive going part of the waveform is applied to capacitors 1, 2 the former of which is small compared to the latter and thus responds to rapid changes such as those caused by a slub. The resistor network is such that R6 XR8 = R7 XR4 and resistors 6 and 7 are small in comparison with resistors 4 and 8. The voltage across capacitor 2 follows that across capacitor 1 for slow changes. The radiation source need not be modulated, a D. C. lamp may be used and the detected radiation applied to modulate a carrier in a conventional circuit. An alternative push-pull circuit is described with reference to Fig. 3 (not shown).