A Photo-Electric Wool Staplemeter

Abstract

THE possibility of constructing a photo-electric apparatus capable of measuring the variations in fibre-length and diameter, and hence of 'tippiness' and 'break' in wool staples, has been exercising the mind of one of us (H. G.) for some time past, but only after reading a recent paper by Lord¹ were steps taken towards its realization. An experimental model, constructed by the other (R. E. B.), was ready in December 1947. In this model, the wool staple, after it has been prepared as described below, is laid lengthwise under a sheet of glass on an optically black tray (Fig. 1). The tray is capable of moving between two guides along the floor of a light-tight compartment of the apparatus. A 100-watt pearl lamp illuminates a narrow rectangular slit which is focused by means of a cylindrical lens to produce, on the tray top and at right-angles to its motion, a narrow rectangular light image approximately $\frac{1}{8}$ in. wide and 3 in. long. The scattered light from the wool is measured by means of a photo-cell which is located directly above the light image. This cell is connected to a direct-current amplifier² the output of which is noted on a 0–50 micro-ammeter.