Thickness measurement of cylindrical objects, wire etc. - by determining attenuation of parallel light beam passing through measurement vol. via rectangular aperture and lens

A device measuring the thickness or dia. of wires, threads, fibres and cylindrical objects of approx. circular cross-section uses a photodetector determining attenuation of a parallel beam. It achieves a measurement accuracy of 0.1 per cent. A parallel light beam passing through the measurement vol is limited by an approx. rectangular aperture from which it passes to the detector via a lens. The detector output is compared with that of a detector receiving a reference part of the beam in an amplifier used to regulate the light source power to give a defined reference intensity.