GB932648A - Improvements in or relating to apparatus for testing fluid properties - Google Patents

Abstract

932,648. Testing fluid properties. MINNEAPOLIS-HONEYWELL REGULATOR CO. July 30, 1959 [Aug. 6, 1958], No. 26212/59. Class 40 (3). Apparatus for testing or determining the specific gravity, composition or colour of a fluid as a function of the refractive index and/or absorption characteristic of radiation in the visible and infra-red regions of the spectrum comprises a wave-energy guide receiving visible and infra-red wave-energy from a source of radiation and normally retaining the received energy by total internal reflection at the boundary longitudinal surface of the guide, means for maintaining the fluid to be tested in contact with at least a part of said boundary surface and a meter for indicating the emergence from the guide of wave-energy which is reduced by the energy loss taking place at the interface of the fluid and the guide in dependence on the variation of one or more physical properties of the fluid. Wave-energy from an electric lamp 12 is reflected by a hood 20 and passes in alternation to the ends 32, 36 of wave energy guides 34, 38 through an aperture 24 in a disc 22 rotated by a motor 30. A portion 58 of the guide 34 is surrounded by a sealed enclosure 40 through which the fluid to be tested is circulated by pipes 50, 52. The ends 60, 62 of the guides 34, 38 are opposite radiation-sensitive members 64, 66 having thermopiles 68, 70 connected by conductors 72, 74 and 78, 80 to a meter circuit 76 of the balanced type. The employment of the second guide 38 permits variation of the intensity of the lamp 12 without disturbing the normal balance of the meter indication. The guides 34, 38 are rods of a material which may be sapphire, quartz, an acrylic resin or a methyl methacrylate plastic and which is chosen to have a refractive index somewhat greater than that of the fluid or liquid to be tested, and normally provides total internal reflection of the wave-energy beam entering at the ends 32, 36. With the test fluid present in the enclosure 40, some of the wave-energy will be refracted at the interface portion 58, and result in a reduction of the wave-energy incident on the device 64. The unbalanced outputs of the elements 68, 70 are fed over the conductors 72, 74 and 78, 80 to an amplifier 84, Fig. 2, controlling a motor 94 which rotates a pointer 100 over a scale 102 and also moves an arm 108 over a potentiometer 110 until the inputs which are fed to the amplifier 84 are equal. In a similar manner, by using wave-energy of appropriate wavelength from the source 12, the absorption coefficients of various liquids may be determined or compared with a reference standard. A modification, Fig. 3 (not shown), employs a single wave-energy guide, similar to the rod 34 of Fig. 1, with the enclosure for the fluid to be tested, and a radiation source, assumed to be of unvarying intensity, disposed adjacent the end 32 of the guide 34. The meter employed is of the null balanced type as included in Fig. 1, or may be of the type described in Specification 568,204.