US 4,026,156 AGranted

Vertical displacement measuring apparatus

AssigneeThe Charles Stark Draper Laboratory, Inc.

InventorsPhilip N. Bowditch, William E. Toth, Arthur Grossman

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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.

Claims9

Dependent claims

Apparatus for measuring the vertical displacement between a remote point and a reference point, comprising:

A. a differential transducer having a two input port sensor and including means for generating a signal representative of the difference in pressure applied to the input ports of said sensor,
B. a reference reservoir means and a remote reservoir means, each reservoir means having a liquid working fluid disposed therein, said working fluids each having a gas-liquid interface in its reservoir means and being disposed at points at and below said interface,
C. a reference reservoir hydraulic coupling means for coupling one of said input ports with the interior region of said reference reservoir means at a point below its working fluid interface,
D. a remote reservoir hydraulic coupling means for coupling the other of said input ports with the interior of said remote reservoir means at a point below its working fluid interface,
E. vapor pressure equalization means including a pneumatic coupling means interconnecting the portion of the interior region of each of said reservoir means at a point above its respective working fluid interface to maintain substantially equal pressure in each of said portions, and
F. volumetric temperature compensation means for offsetting temperature dependent changes in volume of said working fluids in said hydraulic coupling means.

3 more elements

Dependencies are inferred from the claim text.