| 摘要 |
1471685 Density indicating apparatus VDO ADOLF SCHINDLING AG 26 June 1974 [4 July 1973] 28428/74 Heading G1A [Also in Division H1] Apparatus for measuring the density of a liquid within given limits comprises a source of parallel light 7-12, a light conducting rod 1 with its lower end to be immersed in the liquid, a measuring surface 19 interface with the liquid and a reflecting surface 18 directing light refracted by the liquid to detector 16. The angle of incidenceαat the measuring surface 19 is less than or equal to the total internal reflection angle with liquid of the lower density and the angle of incidenceαB at the reflecting surface 18 is the Brewster angle with liquid of the higher density. As shown, light from GaAs source 7 is collimated and, after passing down the rod 1 is reflected from surface 17 on to measuring surface 19. The refracted light is reflected from surface 18, crosses interface 23, preferably normally, and strikes detector 16 which may be photovoltaic, a photodiode or a photo-resistor. The body 1 is preferably of poly(methylmethacrylate) and reflecting surface 17 has a mirror coating of gold 24 protected by coating 25 of e.g. bitumen. As the liquid density decreases, the light reaching detector 16 decreases. The apparatus may be used for measuring accumulator acid density and may be incorporated in or comprise a plug therefor. It may also comprise a thermistor for measuring the acid temperature. Reference has been directed by the Comptroller to Specification 1397170. |
