Differential pressure sensor
First Claim
1. A pressure sensor for use with a sea mine for sensing variations in water pressure at ambient induced by hydrodynamic flow caused by a passing vessel to emit a responsive signal comprising:
- a casing entrapping a volume of gas for pressurization;
means allowing equalization of pressure (PA) within the casing to initially pressurize the trapped air at ambient;
said casing including means adapted for movement (Δ
L) against the pressurized gas in response to pressure variations (Δ
P) from the ambient according to the formula;
##EQU8## wherein PA =pressure at ambient;
means generating a first signal (Δ
eo) responsive to pressure variation from the ambient, the magnitude of which varies according to the formula ##EQU9## means generating a second signal (eA) responsive to ambient pressure;
means squaring the second signal to (eA2); and
means multiplying the first signal and squared second signal to emit the responsive signal (Δ
e'"'"'o) according to the formula;
##EQU10## whereby Δ
e'"'"'0 ˜
Δ
P thereby providing an emitted signal which is independent of the pressure at ambient (PA) resulting from various water depths at which the sea mine may be laid but responsive to pressure variations (Δ
P) from the ambient.
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Accused Products
Abstract
A pressure sensor for use with a sea mine for detecting the presence of a ssing vessel by sensing a change in ambient water pressure caused by the Bernoulli effect relating to hydrodynamic flow induced by the vessel'"'"'s motion. The sensor emits a responsive signal which can be used alone, or with signals from other influence sensors (acoustic and magnetic), to determine when the sea mine shoud be exploded. The sensor provides for equal sensitivity independent of the ambient pressure of the water at various depths at which sea mines may be planted, and employs electrical filters to eliminate noise.
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Citations
8 Claims
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1. A pressure sensor for use with a sea mine for sensing variations in water pressure at ambient induced by hydrodynamic flow caused by a passing vessel to emit a responsive signal comprising:
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a casing entrapping a volume of gas for pressurization; means allowing equalization of pressure (PA) within the casing to initially pressurize the trapped air at ambient; said casing including means adapted for movement (Δ
L) against the pressurized gas in response to pressure variations (Δ
P) from the ambient according to the formula;
##EQU8## wherein PA =pressure at ambient;
means generating a first signal (Δ
eo) responsive to pressure variation from the ambient, the magnitude of which varies according to the formula ##EQU9## means generating a second signal (eA) responsive to ambient pressure;
means squaring the second signal to (eA2); andmeans multiplying the first signal and squared second signal to emit the responsive signal (Δ
e'"'"'o) according to the formula;
##EQU10## whereby Δ
e'"'"'0 ˜
Δ
P thereby providing an emitted signal which is independent of the pressure at ambient (PA) resulting from various water depths at which the sea mine may be laid but responsive to pressure variations (Δ
P) from the ambient. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of sensing variation from ambient pressure at water depth at which a sea mine is laid, which variations are caused by hydrodynamic flow due to a passing vessel, and emitting a responsive signal comprising the steps of:
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generating a first signal (Δ
eo) which varies according to pressure variations (Δ
P) from the ambient pressure (PA) according to the formula;
##EQU11## generating a second signal (eA) responsive to the ambient pressure according to the formula eA =K'"'"'PA and lowpass filtering the second signal to remove noise;squaring the filtered second signal and multiplying it by the first signal to provide a responsive signal (Δ
e'"'"'o) according to the formula;
##EQU12## therefore, Δ
e'"'"'o ˜
Δ
P, whereby the responsive signal (Δ
e'"'"'o) is responsive to pressure variations (Δ
P) but is not effected by the pressure of the water (PA) in which the sea mine may be laid.
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Specification