Inventors:
Philip N. Bowditch - Cohasset MA
William E. Toth - Bolton MA
Arthur Grossman - Framingham MA
Assignee:
The Charles Stark Draper Laboratory, Inc. - Cambridge MA
International Classification:
G01C 504, G01C 920, G01L 718
Abstract:
Apparatus for measuring the vertical displacement between a remote point and a reference point. The apparatus comprises a pair of reservoirs, each having a liquid working fluid disposed therein, a differential pressure transducer and a hydraulic coupling means for each of the reservoirs. Each hydraulic coupling means couples a point in the reservoir below the top surface of the working fluid to an associated input port of the pressure transducer. A vapor pressure equalization means is provided for the reservoirs whereby the points above the top surface of the working fluid in each reservoir are maintained at substantially equal pressures. The apparatus further includes a volumetric temperature compensation means for offsetting temperature dependent changes in the volume of the working fluids which occur in the hydraulic coupling means. The pressure transducer provides an output signal representative of the difference in hydrostatic pressure applied to the input ports of the sensing element associated with the transducer.