Differential pressure transducer utilizing a variable ferrofluid keeper as an active magnetic circuit element
First Claim
1. A differential pressure transducer for measuring external pressures comprising:
- a. first and second containment means for containing a ferrofluid, said first and second containment means responsive to changes in pressure applied to said first and second containment means;
b. a ferrofluid distributed within each of said first and second containment means;
c. interconnection means between said first and second containment means for allowing flow of said ferrofluid in response to changes in pressure applied to said first and second containment means;
d. magnet means in magnetic contact with said ferrofluid for producing a magnetic field;
e. sensing means for determining changes in the flux density of said magnetic field in response to changes in ferrofluid distribution caused by pressure applied to said first and second containment means.
3 Assignments
0 Petitions
Accused Products
Abstract
A differential pressure transducer for measuring external pressures is disclosed. The pressure transducer uses a ferrofluid contained in two interconnecting chambers, enclosed by two non-magnetic spring diaphragms. In this embodiment, two independent inductance series circuits, each comprising a bar magnet, Hall effect sensor and an iron pole piece, measure variations in the volume of ferrofluid in each of the interconnecting chambers. Changes in pressure displace the non-magnetic spring diaphragms causing the volume in each interconnecting chamber to change in a differential manner. The flux path in the series magnetic circuit is distorted by changes in the volume of the ferrofluid, causing changes in the flux density at the sensing area of the Hall effect sensor, this sensor producing an electrical signal proportional to the flux change. The differential output of the two Hall Effect sensors contained in the two series magnetic circuits produce an electrical signal proportional to the applied differential pressure.
97 Citations
18 Claims
-
1. A differential pressure transducer for measuring external pressures comprising:
-
a. first and second containment means for containing a ferrofluid, said first and second containment means responsive to changes in pressure applied to said first and second containment means; b. a ferrofluid distributed within each of said first and second containment means; c. interconnection means between said first and second containment means for allowing flow of said ferrofluid in response to changes in pressure applied to said first and second containment means; d. magnet means in magnetic contact with said ferrofluid for producing a magnetic field; e. sensing means for determining changes in the flux density of said magnetic field in response to changes in ferrofluid distribution caused by pressure applied to said first and second containment means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
-
-
18. A differential pressure transducer comprising:
-
a. a body member having at least a first and a second outside wall; b. first and second magnetic assemblies located within said body member, each of said magnetic assemblies comprised of a permanent magnet, magnetic keeper and magnetic fill tubes, said permanent magnets producing a magnetic field having a flux density; c. first and second nonmagnetic, spring diaphragms, each capable of displacement by an external pressure; d. first and second reservoirs formed by said first and second spring diaphragms and said first and second outside walls, respectively; e. a ferrofluid contained within said first and second reservoirs and in magnetic contact with said magnetic assemblies; f. a passage connecting said first and second reservoirs allowing said ferrofluid to flow between said first and second reservoirs in relation to said displacement of said first and second diaphragms by an external pressure; and g. first and second Hall Effect sensors located within said body member and enclosed by said magnetic assemblies, said Hall Effect sensors adapted to produce electrical signals corresponding to changes in said flux density resulting from the flow of ferrofluid when said first and second diaphragms are displaced by an external pressure.
-
Specification