GB1465514A - Apparatus for inspecting fluids - Google Patents

Abstract

1465514 Inspecting fluids with suspended solid particles L PRAHM O PRAHM E A FERNSTEN B M FERNSTEN S T HIMES R H HIMES J PRAHM G W MACKENZIE W H McINERNEY [trading as Prototron Associates] 4 July 1974 [5 July 1973] 29772/74 Heading G1A An apparatus for inspecting a solid particle bearing fluid in a container comprises means for scanning with a well defined light beam a transverse area of the fluid, a detector for producing from the light scattered sequentially from the particles a sequence of electrical signals, said beam being stopped by means between the container and the detector, and indicating means providing a measure of particulate material. Helium-neon laser 10 generates a beam 2mm in diameter reduced to 150Ám by lens 12. Cylinder 14 is rotated by synchronous motor 17 via gear train 16 and gear 15, and has an optical flat 18 at an angle of around 45 degrees to centre line 13, to which the beam is parallel causing the thus offset beam to make a circular scan. Opaque plate 20 blocks light doubly reflected by flat 18. Lens 24 focuses the beam within bottle 23, which contains the fluid and is restrained by stop 25. Target 27 stops the beam, but scattered light is focused on to silicon photodiode 34 by lens 32, situated midway between the median depth of focus in bottle 23 and photodiode 34. Neutral grey filter 35 could be used to reduce the light intensity. The arrangement of Fig. 2 may be used instead of lens 32. Lens 32 or lenses 37, 38 have an area greater than the scanned area. Amplifier 44 passes from 200 to 100,000 Hz. Amplifier 47 gives an output of say +14V when the voltage at A is less than at B, and -14V when it is greater. Source 50 provides a reference voltage. Adjustment of potentiometer 49 alters the threshold voltage above which a pulse at A gives a negative pulse from amplifier 47. In timer 51 the normally open gate 93 is closed for the duration of any pulse 98 applied at input 91, which causes multi-vibrator 90 with differentiating circuit 92 to give spike pulses 100, 101. If pulse 98 is less than 20Ás, gate 93 is open for pulse 101 to cause pulse 102 from multivibrator 94; otherwise it is closed. 15 second one shot multi-vibrator 55 opens gate 52 and resets counter 70. In divide by 10 counter 54, at every 10th pulse AND gate 64 is supplied with the 10 count pulse and a pulse from input 61. Device 72 may indicate the amount of particulate material in the sample volume. The beam may be passed through a second cylinder with an optical flat, in addition to cylinder 14. These cylinders may be rotated at unequal velocities causing a scan of successive expanding and contracting spirals or if the rotation of the second cylinder is substantially faster than the first a cycloidal scan results. Ultraviolet light may also be employed.