Length measuring apparatus

924,603. Electric selective signalling systems. JOSEPH LUCAS (INDUSTRIES) Ltd. March 23, 1961 [March 31, 1960], No. 11441/60. Class 40 (1). In order to determine the height of mercury in a tube or to determine the length of an elongated object a diffraction grating is fixed adjacent to the length to...

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Hauptverfasser: MCCLEMENTS PETER JOHN, BRASH ROBERT ALEXANDER, ALEXANDER DONALD
Format: Patent
Sprache:eng
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Zusammenfassung:924,603. Electric selective signalling systems. JOSEPH LUCAS (INDUSTRIES) Ltd. March 23, 1961 [March 31, 1960], No. 11441/60. Class 40 (1). In order to determine the height of mercury in a tube or to determine the length of an elongated object a diffraction grating is fixed adjacent to the length to be measured and an optical system including a further diffraction grating is moved to sense the fixed scale and the object being measured to thereby produce electric pulses representing the desired length which are counted. In a first embodiment, Fig. 4, a fixed reflective scale 27 is scanned by a system 28, 29, 30, 31, and the object is scanned by a system 32, 33, 36. In the preferred form of this embodiment, the object is mercury in a tube 11 and pulses from the fixed scale 27 are counted as the carriage 20 is moved downwards from the top of the tube until the top of the mercury column is detected. In the Provisional Specification the fixed scale is transmissive and is positioned in front of the column of mercury so that as the carriage 20 moves downwards the light path is eventually blocked by the mercury column.