| 摘要 |
1,204,419. Measuring acceleration of gravity. COMPAGNIE FRANCAISE THOMSON HOUSTON-HOTCHKISS BRANDT. 3 May, 1968 [5 May, 1967], No. 21168/68. Heading G4H. A device for measuring the value of the acceleration g of gravity includes a laser interferometric device for measuring the time an object thrown vertically upwards takes to get from a position A (Fig. 2) to a position B (predetermined as the position when N fringes from the interferometric device has been counted) and a device for measuring the time intervals T 1 , T 2 between the passages of the object at positions A, B on its upward path and on its downward path. In the embodiment described (Fig. 3) interference pulses S1 after shaping are fed via a gate 61, enabled by a signal S2 from a photo diode when the object, a trihedron mirror, passes through position A, to a counter 10, the first pulse passing through gate 61 also setting a bistable device 73 controlling a further gate 63. Clock pulses from a high frequency source 3 then pass through gate 63 to a first counter 81. When the counter 10 reaches a predetermined count N a circuit 91 sets a second bi-stable device 74 to enable a gate 64 to pass clock pulses to a second counter 82. Either a direction discriminator 13 or a threshold detector (17, Fig. 4, not shown) connected to the output of a sawtooth generator (15) receiving the shaped interference pulses transmits a signal to the counter 10 at the top of a trajectory of the mirror to reverse the count, bi-stables 74, 73 being reset when the count reaches N and zero respectively to stop the counts in counters 82, 81. The contents of the counter are fed to a computer which calculates where L is the height AB. A large number of measurements may be taken and the mean calculated. The result may be printed.
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