Fluxgate (& other) Patents
© Brooke Clarke,
2002 - 2022
14 Feb 2005 - Changed all patent links to a more stable URL.
Background
Historical
Two Terminal Coil
Brown
Frequency
Change Magnatometer
Core Material
Other Category (in addition to Fluxgates)
Patent Class
Magnetic Anomaly Detection
Patents
Honeywell MR Sensors
Philips MR Sensors
Active Impulse Magnetometer (AIM)
Related
Links
2022 May 7 - upgraded links
from USPTO to Google patents.
2022 March - new web page for Magnetic Locators. So far
all of them have been gradiometers based on a pair of
flux gate magnetometers. There's also
a great patent explaining magnetostrictive materials.
Background
The idea of a flux gate is that a "soft" magnetic core, like
Silicon (electrical) steel concentrates the earth's magnetic
filed. There's a coil(s) of wire wrapped around the
core. When there is no drive current the earth's field is
concentrated in the core, but when enough current is applied to
saturate the core it's as if the core turned into air and the
magnetic field goes way down. The changing magnetic field
generates a voltage waveform in the surrounding coil. If
the core is a straight bar then when it's pointing North-South
the voltage generated will be larger than when it's pointed
East-West, and so by using at least two bars a compass bearing
can be determined.
The needle type magnetic compass has a problem because the
Earth's magnetic field has a vertical component, where I live at
39 North latitude the vertical component is stronger than the
horizontal component. So the needle type compass is
manufactured with a weight on the south end of the needle to
keep the north end from pointing down and scraping on the
compass card. Thus most needle type magnetic compasses can
only be used in some range of latitudes so as to have the needle
balanced. The vertical component also causes a problem for
other types of magnetic compass in that if the compass is not
held very level it's reading will have big errors.
I think the first "flux gate" compass patent is:
1863415
Magnetometer, Rieber
Frank, Gen
Electric, Jun 14, 1932, 324/256, 340/870.33, 33/361, 33/362 - this is a single bar design that
is intended to general use, but I think may be the first using
the idea of gating the earth's field on and off.
2047609
Magnetic field direction and
intensity finder, Haig
Antranikian, Jul 14, 1936, 33/301,
33/362, 324/247, 340/870.33 -
uses 2 bars at right angles to each other as compass
Up to some point in time most of the Flux gate/valve
systems used a 'Y" core with the legs spaced 120 degrees to be
compatible with Selsyn (Wiki) type
indicators. This type of indicator provides a mechanical
pointer that can rotate a full 360 degrees and was the most
desirable type of compass indicator for many decades and is still
used in many systems. From very early on (1940s) the second
harmonic output was understood and the need to minimize the
fundamental feed through and other harmonics that would distort
the second harmonic. This was done using band Pass Filters
(BPF).
Variation is the difference between true North and magnetic
North and is a function of Longitude, Latitude, Elevation and
date. If you know these inputs the World
Magnetic
Model will calculate the variation. Also if you know
you are driving on a road that goes North then you could press a
button to tell the electronic compass to apply a variation
correction to bring the display to 0 degrees.
Compensation refers to correcting for error due to surrounding
ferrous metal and to surrounding magnets. This is also
referred to as soft and hard iron compensation. Also
called Remanence. If the fluxgate is rotated in a circle
while being kept level and the X and Y sense circuit outputs are
plotted the resulting figure should be a circle with it's center
at 0,0. If the center is not at 0,0 then there's a local
magnetic object present. If a number of points are
measured then gain and offset corrections can be applied to the
X and Y sensor circuit outputs to make the plot much closer to a
circle.
There are a number of applications for the Fluxgate (Wiki).
Some are used to sense the Earth's field in a non directional
way like are used in sea mines. For this application low
power consumption is very important. This is achieved by
turning off the drive coil current as soon as the core
saturates.
In compass applications the core saturation needs to continue
until the sense coil pulse has subsided.
The HP 428 Clip-on Milliammeter works
as a milliampere meter using a probe that's a Flux Gate
magnetometer. The electronics in the box includes a 20 kHz
Flux Gate drive, a 40 kHz synchronous detector and a feedback DC
current so that the probe is working as a null detector.
If the probe jaws are held open, say with a sheet of paper, the
probe can act as a compass.
Historical Flux gate designs
1047157 Device for determining direction, Donald
M Bliss, Dec 17, 1912, 33/362, 324/257
- a coil is motor driven and the Earth's magnetic field
generates a voltage that can be used as a compass.
2016977 Direction responsive system, Henry
P Thomas, Gen
Electric, Oct 8, 1935, 33/361,
340/870.32, 324/255 - a
big improvement on the earth
inductor compass (Wiki)
2406870
Apparatus for responding to
magnetic fields, Victor
V Vacquier, App: 1941-07-21, W.W.II, Pub: 1946-09-03,
- (See below) is the classic parallel flux gate
magnetometer.
2474693
Magnetic field responsive device, Robert
G Rowe, App: 1945-01-31, W.W.II, Pub: 1949-06-28, 324/244; 33/362; 33/361; 324/209 -
based on the idea of magnetostrictive materials changing length
2856581 Magnetometer, Alldredge
Leroy R, Oct 14, 1958, 324/253,
336/20, 336/221, 340/870.33 - the
first classic orthogonal type magnetometers.
2916696
Saturable
measuring device and magnetic core therefor, Schonstedt
Erick O, Dec 8, 1959, 324/254,
336/221, 336/192, 340/870.33, 336/175, 336/155 - also
see the Magnetic
Locators web page for more about these.
Two Terminal Coil (TTC)
There are a number of patents
covering what I'm calling a Two Terminal Coil (
TTC). This
is the simplest coil to wind. Many other patents require a
separate drive and sense coil and a few a third feedback
coil. These other coils (complexity) may be justified
by better specs for some performance parameter, but at what
price? So you can search (CTRL<F>) TTC on this page to
locate them.
The
TI DRV400 series
of ICs
work with two terminal coils with the
option of adding a compensation coil to null the filed using
feedback. Aimed at current sensing rather than
compass.
Note the IC has an internal magnetic sensor, the external coil,
with a gap for the IC, has a feedback coil, but no drive coils.
Brown
Brown invented a number of
naval
mine sensors for the U.S. Navy. These were designed to
both work and to have very low DC power drain. They are
typically very simple transistor oscillator circuits. search
(CTRL<F>) in this page for "Brown"
Frequency Change Magnetometer
Speake & Co Limited
used to make 3-termianl magnetometers (Ground, +5 and a
frequency output) there part numbers were like FGM-3.
The new company making them is FG Sensors.
I think these are all based on
the Hughes patent
4305034.
|
4305034
Magnetic field intensity measuring device with frequency
change indication, James
C. Long, Monroe
J. Willner, William
R. Good, Hughes,
1981-12-08, -
This patent pre dates PNI patent 4851775 and is called by
the PNI patent as prior art.
5000 Turns 40 to 44 AWG, over Metglas 2705M (0.6" x 0.020"
x 0.001") CD4007 circuit
|
|
4851775
the first PNI ML sensor patent, now expired
Another possible implementation would be to use PNI
magneto inductive sensors.
1200 Turns over Metglas 2705M strip 1.8cm x 0.5mm x 20 um)
LM339 circuit
|
Flux Gate Core Material
There are two states of the
"Gate".
"Open" = With no bias the core has a very high permeability and a
lot of the magnetic field is concentrated in the core.
"Closed" = When the drive coil saturates the core and the mu goes
to 1 the same as air.
The transition between Open and Closed causes a lot of flux lines
to cross the sense coil.
Properties of a good core are that
it has very high permeability (
Wiki).
This means that the core will concentrate a lot of the earth's
field. Air has a mu of 1 and
mu-metal (aka
Conectic
AA) may be on the order of 350,000. Also it's
good if the material is very "soft", i.e. has a low remanence (
Wiki).
That's to say that it does not take on a magnetic set or become a
magnet. You want it to become non magnetic of it's not in a
magnetic field. Note that "soft" and "hard" also go along
with the physical properties of iron. Magnets are made of
"Hard" iron. The iron used in flower ties is "soft" and easy
to bend.
Early cores were made of iron sheets like are used in
transformers. These typically were in a "Y" configuration
with a coil on each leg and were used in 3 phase synchro type
systems.
Later cores were wound using very thin strips of mu-metal inside
ceramic toroid cores. By using ceramic the finished core
could be heat treated (in a reducing Hydrogen atmosphere so that
the metal would not oxidize) at very high temperatures. The
heat treating relieved the stresses in the metal caused by the
winding and about doubled it's mu. These are very expensive
to make. Mu-metal only comes in thin sheets or foils.
Instead of using sheet metal to form the toroid core very fine
wire can be used. I have a 100' spool of extremely high mu
wire that's very small in diameter and if wound on a 1 or 2 inch
diameter form would not be stressed very much. It could also
be used as a straight core in a cylindrical coil wound on
something like a small coffee stirrer or drinking straw.
The latest materials are the
Metglas 2714
type that can have a mu of 1,000,000. This material is used
in some types of anti shop lifting strip type tags (about
45x11x1.5 mm). It only comes as sheet material and typically
is between 0.1 to 2 mils thick.
Also see:
Magnetics
Other Category
In July 2004 I have expanded this page to include other
magnetic sensors. My interest now is in what I call magnetic
signature as applied to a fixed magnetometer and a car driving
by. This is a much simpler case than that of an aircraft
flying a Magnetic Anomaly Detector (MAD), a sub or a buoy looking
for a sub. These moving platform systems typically use a
number of frequency bands and then process the amplitude signals
in each band to detect subs (see the movie "Hunt for Red
October").
The patents in boxes have some signal processing ideas that could
be applied to my interest.
The system I would like would be placed in the driveway and
announce that a UPS, Fedex, propane truck or a small, medium or
large car had entered the driveway. If it's sensitive enough
it should also announce the one or some number of people were
walking up the driveway.
Magnetic anomaly and MAD are key words for this type of sensor
when in a moving platform. So far I have not found the key
words for a fixed sensor looking for a moving object.
Threshold levels and time measurements may be all that is needed
for a micro controller to process in order to determine what is
causing the filed change.
Note that a total field magnetometer can not detect a change in
the direction of the field only it's magnitude and so is not as
useful as a vector field sensor for signature analysis. If a
single axis vector type magnetometer was aligned to the Earth's
field and there was a small perturbation in the field, it would be
difficult to detect (a small change on top of a large
reading). But if the magnetometer was installed so it's
sensitive axis was orthogonal to the Earth's field (say level and
on the E-W magnetic axis) then the sensor output would be zero on
average and it's gain could be increased to allow picking up small
changes in the field. A 2-axis sensor could be arranged so
that both sensors were orthogonal to the Earth's field and would
be even more sensitive to changes since it would pickup changes in
a direction where the orthogonal direction would have a small
change.
By using two of these sensors in a differential mode only
gradients in the field would be sensed and changes in the Earth's
field would be canceled. Note that magnetic
gradiometers only sense changes happening close to the two
sensors. Changes far away effect both sensors the same way
and cancel out. See: Magnetic Locators.
If you want to detect changes in the far magnetic field all that's
needed is a coil with an iron core. The core will
concentrate the earth's magnetic field and when the field changes
the coil will output a voltage. It works in a fashion
similar to the playback head on a tape recorder. A coil
sensor like this can be used to detect moving cars (but not
stationary cars).
Patents that contain the phrase "magnetic signature" usually are
referring to an equivalent of a bar magnet aligned along the long
axis of a ship. The difference between these relates to the
mass of the ship and it's speed and direction.
Patents that contain the phrase "magnetic dipole" may be talking
about a way to differentiate various classes of objects even to
the level of serial number.
Some of the Honeywell application notes show the X, Y and Z
magnetic field of a roadside sensor as various vehicles drive
by. The engine and axles clearly show up making it possible
to classify vehicles.
33
Geometrical
Instruments -
324
Electricity:
Measuring and Testing
327 Miscellaneous Active Electrical Nonlinear Devices, Circuits,
and Systems
331
Oscillators
340
Communications:
Electrical
428
Stock
Material or Miscellaneous Articles
Magnetic Anomaly Detection
This is used by Navy P-3 aircraft (Wiki)
to detect submerged subs. It's also used by remote
controlled mini subs to detect mines and other ferrous objects on
the ocean floor. I think the concepts would be applied to a
fixed sensor to allow magnetic signatures to be detected.
These patents have the words "magnetic anomaly" in the abstract.
(this was too restrictive, next search just for "magnetic" and
"anomaly".
The key patent for MAD is 2406870 (See Below). Dozens if not hundreds
of other patents cite this one.
6362625
Active magnetic anomaly sensing system having synchronized
transceiver and discriminator
6268725
Flux-gate magnetometer with drive signal for reducing effects of
Electromagnetic Interference, Scott D. Vernon, Larry E. Tyler
(Medtronic), Jul 31, 2001
uses a drive waveform that vairis
over time so that a fixed frequency interference will not cause
interference
6121772
Magnetic sensor
6080352
Method
of magnetizing a ring-shaped magnet
6043647
Magnetic
anomaly detector for detecting the movement of ferrous metals
6031377
Magnetic
anomaly detection buoy for detecting submarines
2404806
Submrine Detector July 30, 1946 340/850; 102/402;
324/247; 324/331 (airborne, picks upmotor or battery charger
fields)
2632884
Orienting Device for Magnetic Dector Devices March 24, 1953 324/253;
318/647; 324/246; 324/331 (airborne towed MAD)
2834000 Sound
Detecting DeviceMay 6, 1958 367/155; 367/173 (barrium
Titnate hydrophone)
3471777
Differential Magnetometer Having Parallel Rotating Fields &
Associated Sensing Circuitry Oct 7, 1669 324/247;
102/402 (used on a buoy to detect subs)
3737842
Feature Recognition Techniques June 5, 1973 340/850;
324/76.31; 324/331; 324/345
3757203
Magnetometer for Detecting & Identificatin of
Immersed Bodies Sep 4, 1973 324/331; 324/326
2426622
Magnetic Field Detector Sep 2, 1947 324/254;
324/253; 324/345; 341/15
2900595
Magnetic Field DetectorApr 18, 1959 324/335;
324/250; 342/394; 342/458; 455/137; 455/141
3257608
Optical Magnetometers June 21, 1966 324/304;
324/244; 324/244.1; 324/301; 331/3; 359/281 (similar
to a Rb freq std)
3398360
Magnetic Body Detector sensitive only to Magnetic
Field Variations within a Predetermined Range 324/226;
324/247; 324/254; 324/345 (airborne gradient system)
|
3808519
Method & Device for Determining the Depth of a Magnetic
Anomaly Apr 30, 1974 324/345; 324/326; 324/331
3263161
Method of determining depth and falloff rate of subterranean
magnetic disturbances utilizing a plurality of
magnetometers 324/331; 324/345 - geophysical
application
3441841
Methods and devices for compensation of parasitic magnetic
fields, in particular in an aircraft carrying a
magnetometer 324/244; 324/301
3490032
Method and Apparatus utilizing a pair of spaced magnetometers
for making magnetic surveys 324/345; 324/331
aircraft or sub based
3639828
Compensation of parasitic or stray magnetic fields abroad an
aircraft 324/301; 324/244 - uses differential phase
and frequency from two sensors
5189368
Magnetometer Feb 23, 1993 324/304; 102/417;
324/301 (Larmor precession frequency, low power)
3129410 Electron spin echo memory system 365/152;
324/304; 359/281; 365/121
3500176 Method and Apparatus for controlling a Magnetic Field
employing optically pumped nuclear resonance 324/304
- spacecraft
3526002 Magnebuoy 340/852 March 31, 1960 - atomic
precession sub detection
3750008 Optical Pumping Magentometer 324/301; 324/304
6208268
Vehicle presence, speed and length detecting system and roadway
installed Detector therefore,
John F Scarzello, Daniel S. Lenko,
Adam C. Feaga (Navy), Mar 27, 2001,
340/941 ; 324/174;
324/179; 324/207.26; 324/247; 340/933; 340/940; 701/118
Self Powered Vehicle Detection (SPVD) probably based on sonobuoy
although aimed at highway usage.
References:
| 3614729 |
Vehicle-detecting
apparatus using electromagnetic wave
|
Fujimoto |
October 1971 |
|
| 3626413 |
Traffic surveillance and
control system
|
Zachmann |
December 1971 |
|
| 3641569 |
Highway vehicle sensor
system
|
Bushnell et al. |
February 1972 |
|
| 3778761 |
Vehicle orientation
determination
|
Cribbins |
December 1973 |
|
| 3877666 |
Method for the continuous
detection of vehicle position
|
Itakura et al. |
April 1975 |
|
| 3983531 |
Vehicle-responsive signal
means
|
Corrigan |
September 1976 |
|
| 4234923 |
Vehicle detection systems
|
Eshraghian et al. |
November 1980 |
|
| 4302746 |
Self-powered vehicle
detection system
An improved self-powered vehicle detector (SPVD) uses a
two-axis magnetomr to sense a vehicle's magnetic
signature and then telemeter vehicle presence
information to a roadside receiver.
Fig 3 has the look and feel of a sonobuoy & uses
magnetic signatures. The cylindrical RF antenna
may be the same as used in sonobuoys.
Uses standard ICs.
|
John F. Scarzello, Daniel
S. Lenko, Albert D. Krall, Wayne R. Grine, Robert E.
Brown, George W. Usher, Milton K. Mills, Albert M.
Syeles (Navy)
|
November 1981 |
340/38L; 324/247; 340/38R; 343/700MS;
343/895 |
| 4356489 |
Vehicle speed sensing
apparatus with electromagnetic wave interference
detector
|
Hirota et al. |
October 1982 |
|
| 4368428 |
Method and arrangement
for determining the velocity of a vehicle
|
Dijkman |
January 1983 |
|
| 4767988 |
Precision magnetometer
orientation device
|
Wilson |
August 1988 |
|
| 4920340 |
Vehicle detecting
method and system which can communicate with vehicles
|
Mizuno |
April 1990 |
|
| 4943805 |
Conduit-enclosed
induction loop for a vehicle detector
|
Dennison |
July 1990 |
|
| 4968979 |
Vehicle detecting system
|
Mizuno et al. |
November 1990 |
|
| 5008666 |
Traffic measurement
equipment
|
Gebert et al. |
April 1991 |
|
| 5091697 |
Low power, high accuracy
magnetometer and magnetic field strength measurement
method
|
Roth et al. |
February 1992 |
|
| 5113136 |
Gradiometer apparatus
with compensation coils for measuring magnetic fields
|
Hayashi et al. |
May 1992 |
|
| 5206642 |
Device for detecting data
relating to the passage of vehicles on a road
|
Gregoire et al. |
April 1993 |
|
| 5331276 |
Apparatus for passively
measuring the velocity of a ferrous vehicle along a path
of travel
|
Polvani et al. |
July 1994 |
|
5614825
Magnetic
flux leakage inspection apparatus with surface-responsive sensor
mounting.
5598152
Mine
sweeping system for magnetic and non-magnetic mines
5115196
Girth
weld detection system for pipeline survey pig
4613816
Cryogenic
magnetic probe having new substrate
4437064
Apparatus
for detecting a magnetic anomaly contiguous to remote location by
squid gradiometer and magnetometer systems
4422075
Proximity
monitor
Vehicle Classification
6911829
Inductive signature measurement circuit June 28, 2005 324/654;
324/76.75; 324/546; 329/361
6867709
Vehicle detector and classifier March 15, 2005 340/941; 324/654;
340/933;
340/935;
343/728;
343/748
6670891
Magnetic detector of vehicle wheels Dec 30, 2003 340/933;
340/941
6590400
Inductive signature measurement circuit July 8, 2003 324/654;
324/118; 324/207.15; 331/65; 340/941
5751225
Vehicle detector system with presence mode counting May 12, 1998
340/941; 324/654; 331/65; 340/933; 340/938
5523753
Vehicle detector system with periodic source filtering June 4, 1996
340/933; 324/654; 340/939; 340/941; 377/28
5408179
Method and apparatus for analying traffic and a sensor
therefor April 18, 1995 324/253; 340/941 Sampey
Scientific - Outerlab.net - nu-metrics.com - Single coil
magnatometer
Patents
6917198
Hybrid hall vector magnetometer July 12, 2005 324/251;
435/4; 324/243
6867587
Excitation circuit for a fluxgate sensor March 15, 2005 324/253
6714008
Gradiometric measurement methodology for determining magnetic fields
of large objects March 30, 2004 324/261; 324/247;
324/260 (Magnetic Signature)
6546344
Magnetic anomaly sensor system April 8, 2003 702/65;
324/331 (computer state diagram and process)
6512370 Low
power, frequency-mode magnetometer, John James (Elf Engineering,
Ltd), Jan 28, 2003, 324/253; 33361; 331/65 - Two Terminal Coil (TTC) -
Frequency Mode Magnetometer
Check Citations
Publication
Priority Publication
Assignee
Title
4305034 1979-04-09
1981-12-08 Hughes Aircraft Company Magnetic field
intensity measuring device with frequency change indication
EP0045509 1980-08-04
1982-02-10 Siemens Aktiengesellschaft Means for
the determination of the intensity of magnetic fields, e.g.
earth fields
SU945835
1980-12-12 1982-07-23 Предприятие П/Я
Г-4956 Magnetometer
4733181 1983-12-17
1988-03-22 Robert Bosch Gmbh Single-winding
magnetometer with Schmitt trigger output circuit
4851775 1987-07-02
1989-07-25 Precision Navigation, Incorporated
Digital compass and magnetometer having a sensor coil wound on
a high permeability isotropic core
4859944 1987-08-25
1989-08-22 Analog Devices, Inc. Single-winding
magnetometer with oscillator duty cycle measurement
5015953 1986-07-31
1991-05-14 Security Tag Systems, Inc. Magnetometer
for detecting DC magnetic field variations
5039945 1990-03-27
1991-08-13 Webb Spencer L Single winding
magnetometer with automatic distortion compensation
5124648 1987-08-25
1992-06-23 Analog Devices, Inc. Single winding
saturable core magnetometer with field nulling
5239264 1991-11-14
1993-08-24 Precision Navigation, Inc. Zero-offset
magnetometer having coil and core sensor controlling period of
an oscillator circuit
5642046 1994-06-08
1997-06-24 Magknowledge Inc. Low power
magnetometer circuits requiring a single switching cycle
5818226 1995-09-29
1998-10-06 Sony Corporation Magnetic sensor having
a coil with varying turns along the length of a bobbin
6476610
Magnetic anomaly sensing system and methods for maneuverable sensing
platforms Nov 5, 2002 324/345; 324/225; 324/247;
324/326
6407547
Biaxial flux gate type magnetic sensor Class 33/361
- wafer level 2-axis fluxgate sensor
6380735
Orthogonal flux-gate type magnetic sensor -Cylindrical core with
primary rod along center axis, many claims
6301794
Vehicle compass system with continuous automatic calibration - uC
corrects for local mag field uses triangle to compute center of
circle Class 33/356
6282803
Self calibration circuit for determining an accurate zero
compensation for a fluxgate compass - uC zero during off time
6218831 Low
power fluxgate circuit with current balance, J. Thomas Fowler
(Arthur D. Little, Inc.), 324/253; 324/228; 324/258; 33361;
34087033; 361/156 -
Two Terminal Coil (TTC)
Check
Citations
6208884
Noninvasive room temperature instrument to measure magnetic
susceptibility variations in body tissue
6173501
Compensation system for electronic compass - MR set/reset
6100686
Magnetic field sensor with double wheatstone bridge having
magneto-resistive elements August 8, 2000 324/252;
324/207.12; 338/32R
uses 2 bridge outputs to cancel
offset so no flipping is needed.
6084406 Half-cycle
saturable-core magnetometer circuit,
PNI, 4 Jul 2000, - time delay linear
with mag field.
6075361
Device for detecting a magnetic field June 13, 2000 324/252;
324/225
6031377
Magnetic anomaly detection buoy for detecting submarines, James A.
Watkins, Feb 29, 2000, 324/345; 324/247; 324/226
advantages over sonobuoys and
airborne magnetic anomoly detectors.
References:
| 2404806 |
SUBMARINE
DETECTOR |
Jul 1946 |
| 2632884 |
ORIENTING
MECHANISM
For MAGNETIC (Magnetic ananomaly)
|
Mar 1953 |
| 2834000 |
SOUND
DETECTING DEVICE |
May 1958 |
| 3226670 |
APPARATUS
FOR
DETERMINING CHARACTERISTICS OP THE OCEAN BOTTOM (sonobuoy) |
Dec 1965 |
| 3263161 |
Method
of determining depth and falloff rate of subterranean
magnetic disturbances utilizing a plurality of
magnetometers 324/331; 324/345 - geophysical
application |
Jul 1966 |
| 3471777 |
DIFFERENTIAL
MAGNETOMETER
HAVING PARALLEL ROTATING FIELDS AND ASSOCIATED SENSING
CIRCUITRY |
Oct 1969 |
| 3720909 |
DIRECTIONAL
HYDROPHONE
BUOY SYSTEM (sonobuoy) |
Mar 1973 |
| 3737842 |
FILTER
CHANNELS |
Jun 1973 |
| 3757203 |
Magnetometer
for
Detecting & Identificatin of Immersed Bodies Sep 4,
1973 324/331; 324/326 |
Sep 1973 |
| 3808519 |
Method
&
Device for Determining the Depth of a Magnetic Anomaly Apr
30, 1974 324/345; 324/326; 324/331 |
Apr 1974 |
| 4208738 |
Deployable
sonar
array with interconnected transducers operated in the
bending mode |
Jun 17, 1980 |
| 4938136 |
Resonant
acousticmagnetic
minisweeper |
Jul 3, 1990 |
| 5189368 |
Magnetometer |
Feb 23, 1993 |
5939881
High dynamic range digital fluxgate magnetometer
5924212
Electronic compass, Stanley J. Domanski (Donnelly Corp), Jul 20,
1999, 33/355R ; 324/247; 324/260
uses a number of PNI type two
terminal coils (TTC)
5878370
Vehicle compass system with variable resolution - uses 2 diameters
of circle to correct forlocak mag field
5831873
Magnetic dipole target classifier and method, Kirk K. Kohnen, Harold
C. Gilbert, Wilbur W. Eaton, Nov 3, 1998, 364/559; 364/449.1
"Magnetic Dipole" may be key words
for an advanced "magnetic signature" that allows differentiating
classes or serial numbers of vehicles?
It changes depending on the direction of movement of the vehicle.
Also see
5684396
Localizing magnetic dipoles using
spatial and temporal processing of magnetometer data
Also see: 5239474 Dipole moment detection and localization
5742092
Semiconductor structures, methods for controlling their conductivity
and sensing elements based on these semiconductor structure 257/610;
257/611; 257/E29.109; 257/E29.324
5737226
Vehicle
compass system with automatic calibration - uses an ellipse not
circle for correction
5689445
Electronic compass and attitude sensing system
5652512
Advanced Digital Flux Gate Magnetometer - hi resolution
5642046 Low
power magnetometer circuits requiring a single switching, Timothy J.
Hawks, Jun 24, 1997, 324/253 -
Two Terminal Coil (TTC)
Check
Citations
5621319
Chopped hall sensor with synchronously chopped sample-and-hold
circuit April 15, 1997 324/251; 324/225; 327/384; 327/511;
327/551 Allegro Microsystems - Hall plate alternately driven + then
- and the output synchronously detected, but not done in rotation
for vector detection.
5600611
Wrist mountable compass Feb 4, 1997 368/10; 368/14; 368/281;
D10/31
5495929
Apparatus and method for validation of bank notes and other valuable
documents, Valeri V. Batalianets, Georgi O. Antonov, Mar 5, 1996,
194/207; 382/137
used optical and magnetic signature
of inks in currency validator
5351005
Resetting closed-loop magnetoresistive magnetic sensor Sep 27, 1994
324/252; 33/355R; 324/207.21; 324/225
5270648
Single core triaxial flux-gate magnetometer Dec 14, 1993 324/253;
324/247; 336/213
5254987
Output signal processing unit of a fluxgate sensor - LPF cutoff
variable depending on rate of car turning
5239474
Dipole Moment Detection and Localization - Schonstedt - improved s/n
way of making core
5239290
Magnetic cores for saturable core measuring devices and methods of
manufacturing such cores - tape wound rod
5239264
Zero-offset
magnetometer having coil and core sensor controlling period of an
oscillator circuit, 324/253 ; 331/65
5199178
Thin film compass and method for manufacturing the same - accurate
construction - IC method of realizing old fashioned designs
5170566
Means for reducing interference among magnetometer array elements
5168223
High sensitivity saturable core magnetic field sensor with
symmetrical structure - 1nT combined analog & digital
5151607
Currency verification device including ferrous oxide detection,
Timothy T. Crane, Richard A. Menelly, Robert J. Danek, Sep 29, 1992,
250/556; 356/71
measures the "magnetic signature" of
paper money, mainly the position and strength of the magnetic
thread
5124648
Single winding saturable core magnetometer with field nulling -
single coil for both drive and sense, Spencer
L. Webb, A. Paul
Brokaw (Analog
Devices),
Jun 23, 1992,
324/253 ;
324/225; 33/361; 331/65 (
TTC)
Metglas - 2009-06-23 Anticipated
expiration
References:
| 2991414 |
Electrical apparatus, TILLMAN |
Jul 1961 |
| 3040247 |
Magnetic field detector, VAN ALLEN - FCM
|
Jun 1962 |
| 3427534 |
DIRECTIONAL
MAGNETIC
FIELDS |
Feb 1969 |
| 3454879 |
SMITKA
DIRECT
CURRENT SUMMING CIRCUIT WITH COMPENSATING MEANS |
Jul 1969 |
| 3461382 |
PULSE
DEPENDENT FEEDBACK SYSTEM FOR MEASURING CHANGES IN A
PHYSICAL PHENOMENON |
Aug 1969 |
| 3768011 |
Means
for measuring magnitude and direction of a direct current
or permanent magnet, including clip-on direct current
sensing inductor |
Oct 1973 |
| 3899834 |
ELECTRONIC
COMPASS
SYSTEM |
Aug 1975 |
| 4059796 |
Second
harmonic
magnetic field detection circuit with means to rectify the
sensed signal |
Nov 22, 1977 |
| 4060761 |
Tubular
magnetic
field sensor with means to rectify the sensed signal |
Nov 29, 1977 |
| 4277751 |
Low-power
magnetometer
circuit with constant current drive, Kenneth
D. Lawson, Neil
L. Brown, EG&G,
|
Jul 7, 1981 |
| 4305034 |
Magnetic
field
intensity measuring device with frequency change
indication |
Dec 8, 1981 |
| 4305035 |
Magnetic
field
amplitude detection sensor apparatus |
Dec 8, 1981 |
| 4314200 |
Method
and apparatus for detection of magnetization |
Feb 2, 1982 |
| 4321536 |
Magnetic
field
detection by differential phase lag |
Mar 23, 1982 |
| 4402142 |
Electronic
compass
for automotive vehicles |
Sep 6, 1983 |
| 4447776 |
Pulse
driver for flux gate magnetometer, Robert
E. Brown, Navy,
1984-05-08
|
May 8, 1984 |
| 4539706 |
Mobile
vehicular
repeater system which provides up-link acknowledgement
signal to portable transceiver at end of transceiver
transmission |
Sep 3, 1985 |
| 4626782 |
Magnetometer
operated
at a self-resonant frequency by a sense winding |
Dec 2, 1986 |
| 4677381 |
Flux-gate
sensor
electrical drive method and circuit |
Jun 30, 1987 |
| 4728888 |
Magnetometer
with
time coded output of measured magnetic fields |
Mar 1, 1988 |
| 4733181 |
Single-winding
magnetometer
with Schmitt trigger output circuit |
Mar 22, 1988 |
5039945
Single winding magnetometer with automatic distortion compensation
324/253; 33/361 Metglas
5015953
Magnetometer for detecting DC magnetic field variations, Lucian G.
Ferguson, Lincoln H. Charlot, Jr. (Security Tag Systems, Inc),
324/244; 324/209 -
Two Terminal Coil (TTC) Metglas
Check Citations
4953305
Vehicle compass with automatic continuous calibration - removes
jumps from display. uC flow diagram
4940966
Article detection and/or recognition using magnetic devices July 10,
1990 340/551; 340/572.6; 428/900 - anti shoplifting
tags
4939459
High sensitivity magnetic sensor July 3, 1990 324/247;
324/249; 324/257; 324/258 (car compass)
4929899
Fluxgate magnetometer apparatus and adjustment method to maintain
accuracy over a wide temperature range - construction 7 overdriving
primary
4914381
Direct-coupled fluxgate current sensor - core construction method
4894615
Stress-relieved amorphous metal ribbon magnetometer having viscous
fluid interface - piezo vibration = linear response
4887033
Magnetometer having coil formed by two spiral shaped conductors - GM
core winding mathod
4859944
Single-winding magnetometer with oscillator duty cycle measurement,
Spencer L. Web (Analog Devices), Aug 22, 1989 324/253
(TTC)
Metglas
One way around the PNI patent
4851775
Digital Compass and Magnetometer Having a Sensor Coil Wound on a
High Permeability Isotropic Core. Metglas - Expired
This is the first PNI patent for an
MI type sensor, but note that Ripka says it's really a fluxgate.
Two Terminal Coil (TTC) Calls:
3416072
Thin Film Magnatometer Employing Phase Shift Discrimination
324/249 - Two Terminal Coil (TTC) Metglas
3936949
Static
non-swinging course determining device on a vehicle 324/247 - uses
op amp circuit & Two Terminal Coil (TTC) 0.1 x 50 mm
mumetal wire
4182987
Magnetometer
employing hard axis thin film inductor 324/249 - Two Terminal
Coil (TTC)
recording head Laminated core
4241317
Frequency
generator suitable for use as position-frequency transducer 331/65
- Two Terminal Coil (TTC) & op amp make oscillator
4305034
Magnetic
field intensity measuring device with frequency change indication
324/253 - Two Terminal Coil (TTC) simple oscillator Permalloy wire
4825166
Bobbin for a magnetic sensor, Douglas C. MacGugan (Sundstrand Data
Control), Apr 25, 1989, 324/346 ; 29/606; 324/253; 336/213;
336/221
copper bobbin matches thermal
coeficient of expansion of wire preventing strain over temperature
4769599
Magnetometer with magnetostrictive member of stress variable
magnetic permeability
4763072
Magnetic azimuth detector - improved drive winding and mechanical
construction
4739263
Magnetic Sensor Using The Earth's Magnetism.- TDK - core wires
threaded through coils
4733181
Single-winding magnetometer with Schmitt trigger output circuit,
Harald Bauer (Robert Bosch), Mar 22, 1988, 324/253; 33361 - Two
Terminal Coil (TTC)
4677381
Flux-gate sensor electrical drive method and circuit -
4646015
Flux gate sensor with improved sense winding gating - Etak - core in
saturation < 1% of the cycle
4641094
Magnetometer circuit for measuring the period of beat frequency
maxima Feb 3, 1987 324/302;
324/260;
324/328
4640016
Means for indicating direction and a method of determining a
direction Feb 3, 1987 33/356; 33/363Q; 324/252 similar to
Dinsmore
4626782
Magnetometer operated at a self-resonant frequency by a sense
winding, Richard W. Lewis (Boeing), Dec 2, 1986, 324/253 ;
33/361
By driving the F.G. at the self
reasonant frequency of the drive coil noise in the second harmonic
signal is reduced. By using feedback instead of adjusting
each serial number device this is accomblished automatically.
References:
| 2480265 |
Magnetometer
|
August 1949 |
Rubenstein |
| 2565799 |
Wave-train magnetometer
|
August 1951 |
Brattain |
| 2861242 |
Magnetometer
|
November 1958 |
Leavitt |
| 3001129 |
Electronic oscillator metering device
|
September 1961 |
Knowles |
| 3040247 |
Magnetic field detector
|
June 1962 |
Van Allen |
| 3286169 |
Combined magnetometer and gradiometer
|
November 1966 |
Slonczewski |
| 3427534 |
Device for measuring the magnitudes of
unidirectional magnetic fields
|
February 1969 |
Maxwell |
| 3626280 |
Frequency controlled flux detector
excitation
|
December 1971 |
Van Englehoven et al. |
| 4447776 |
Pulse driver for flux gate magnetometer |
May 1984 |
Brown |
4590679
Compass systems - measure 20 cycles of sensor coil pulses
4580497
Munition, David
P. Erdmann, Dennis
L. Kurschner, John
C. Timmerman, Honeywell,
1986-04-08, - dual magnetic mode land mine.
4546551
Electrical control system - schematic for uC system
4497034
Heading detecting apparatus - slope and offset correction of X &
Y outputs
4495467
Apparatus for simultaneous measurement of magnetic field components
in mutually perpendicular directions _X & Y outputs
4462165
Three axis orientation sensor for an aircraft or the like July 31,
1984 33/361; 33/355R; 33/363Q
4447776
Pulse driver for flux gate magnetometer - Navy low power sea mine
"Brown" 4 terminal coil and 3 transistors, but needs more coils for
the output.
4445279
Magnetic course detector - offset & slope correction on output
of sensor coils
4425717
Vehicle magnetic sensor - mounting on rear view mirror to isolate
from car metal
4424631
Electrical compass - uses digital BPF & synchronous phase
detector instead of bandpass filters to select second harmonic
4413424
Azimuth determinating apparatus - Nippondenso - hard or soft iron
correction
4399615
Direction indicator -
4384254
Oscillator/driver circuit for fluxgate magnetometer May 17, 1983 324/253;
327/190; 327/191; 331/112- "Brown"-Navy low power by letting core
saturation stop drive for sea mines Very simple one transistor two
winding drive circuit. But still needs balanced sense
coils.
It may be that if a cylindrical coil
is used then the sense coils are not needed and the output is just
the frequency of the oscillator?
Calls:
| 2957145 |
Transistor pulse generator
|
Oct., 1960 |
Bernalien |
331/112. |
| 3649908 |
Magnetic field gradiometer
utilizing a pair of cores driven by a blocking oscillator
|
Mar., 1972 |
Brown |
324/253. |
| 3681711 |
Blocking oscillator with
extended variable pulse |
Aug., 1972 |
Hanby |
307/275. |
4308501
Digital peak sensor, Thomas E. Tuccinardi, Michael Conner, (Army), 327/58
; 102/212; 102/417; 102/427; 324/260
looks first for above threshold then
for negative slope in "magnetic signature"
4305035
Magnetic field amplitude detection sensor apparatus Dec 8, 1981
324/255 Hughes -Peak voltage detection like the FLC-100
Sensor has 2 coils over a few 0.005" dia wires from Spang Industries
which is out of business but National
Electronic Alloys makes similar metals
4305034
Magnetic field intensity measuring device with frequency change
indication Dec 8, 1981 324/253; 102/427; 324/258; 331/65
Hughes uses CD4007 IC and a simple Two Terminal Coil (TTC)
type sensor Permalloy wire,
FCM, high directivity, rod shaped core, "...a sensor
which consists of only an inductive element having an elongated and
relatively thin magnetic core, generally made of permalloy, upon
which a coil of copper wire is wound.", "This sensor is connected to
both outputs of a pair of CMOS inverters of the electronic circuit
type as is commonly used in logic circuitry. ", CD 4007,
4300095
Self Excited Field Saturable Core Magnetic Field Detection Apparatus
- Rockwell MR sensor
4292590
Magnatometer Apparatus with Detector Immoblized in Wax, J.H. WIlson
(Westinghouse), Sep 29, 1981, 324/226 ; 174/559; 324/244; 324/260;
324/345; 33/305; 53/472
4290018
Magnetic Field Strength Measuring Apparatus With Triangular Waveform
Drive Means 324/255
4286261
Apparatus for discriminating between strain and magnetic stimuli in
magnetic stimuli in magnetic cored solenoid type transducer line
sensors,
Gilbert F. Wagner, J. Louis Berger
(Army), Aug 25, 1981,
340/565 ; 324/327; 340/551; 340/566;
367/136
Prior art systems just use a cable that was sensitive to strain
AND magnetic disturbances so an alarm did not tell you which
triggered it
This system adds an oscillator driving one end of the cable so
strain can be differentiated from magnetic signatures
outdoor intrusion detector
4262427
Flux Valve Compass System - Sperry Corp - sense windings around core
not over it
4260949
Magnetic field detection apparatus April 7, 1981 324/302
4241317
Frequency generator suitable for use as position-frequency
transducer Dec 23, 1980 331/65; 331/151; 331/167; 331/181 -
This Bosch patent seems to relate to a variable capactance, but also
shows a variable inductance and so is related to the PNI patents.
4194150
Method and apparatus for reducing magnetometer errors (torpedo or
mine)
4193029
Pulsed helium magnetometer 324/301;
331/3
4187779
Marine mine, Harry S. Jones, David B. Kirkpatrick, Robert G. Wilson
(Navy), Feb 12, 1980 [app: Apr 19, 1945] , 102/209 ; 102/417
- 35 year delay in pub
combines hydrostatic pressure and
"magnetic signature" to fire
4185552
Mine firing control system, Whitman D. Mounce, Ralph W. Mann (Navy),
Jan 29, 1980 [app: May 16, 1945], 102/212 ; 102/417 - 35
year delay in pub
uses induction coil to sense
"magnetic signature"
4182987
Magnetometer employing hard axis thin film inductor Jan 8, 1980 324/249;
360/111 -
This Kodak tape head patent is for a
MI sensor where DC and AC are applied to the Two Terminal Coil (TTC)
type sensor.
4183301
Induction ground mine and firing mechanism therefor, Richard J.
Burke, George Renholt, Jr. (Navy), Jan 15, 1980 [application: Aug 7,
1944] 36 year delay in pub
102/411
uses Sensitrol relay to detect "magnetic signature" of
ship. vertical induction coil senses magnetic field.
The Sensitrol is a meter that has relay contacts.
"magnetic signature" is part of the design.
4068164
Harmoic flux gate magnetometers and gradimeters and windings,
Malcolm M. Schwartz, James R. Jaquet ( Infinetics), Jan 10, 1978,
324/226 ; 102/212; 102/417;
102/427; 324/243; 324/253; 340/551; 367/93; 463/47.3
This is a Royer type oscillator in the form of a stick and two can
be combined - low cost
2783384
ELECTRICAL
INVERTER
CIRCUITS, R.L. Bright & G.H. Royer, Feb 26 1957,
331/113A
; 290/4R; 307/401; 331/181; 363/133 - magnetic saturation of the
transformer is a key parameter.
4059796
Second harmonic magnetic field detection circuit with means to
rectify the sensed signal - three wndings, one for feedback, in
newer patents the thrid winding was replaced with a cap and the
sense winding was driven with the feedback DC signal
4030204
Remote indicating solid state magnetic sensor - Hall sensors and
compensating magnets
3971981
Magnetism detecting system - external field rotated while looking
for under sea cable
3959889
Method and apparatus for determining a measured direction relative
to an external magnetic direction - ?
3942258 Earth reference
thin-film magnetometer compass exhibiting total tilt immunity,
Air Force, Mar 9, 1976, 33/361, 324/249, 324/247
3942257
Index Error Correction for Flux Valve Heading Repeater System -
Sperry Rand - "Y" core like servo
3936949
Static non-swinging course determining device on a vehicle Feb
10, 1976 33/352; 33/354; 33/361; 324/247; 324/255
This uses a simple Two Terminal Coil
(
TTC)
type sensor and uses the coil output voltage like in the FLC-100
sensor.
0.1 x 50 mm wire
Calls:
2204292
Directional Indicating Means Jun., 1940 Barth 33/204 -
TTC
hi L/D permalloy wire
2464057
Earth Inductor Compass Mar., 1949 Phair 33/356 -
rotating "Z" metal bar
2597125
Earth Induction System May., 1952 Noxon (Bendix) 33/361 - Flux
gate 2nd harmonic
metal
Laminated? core dual winding
2597135
Earth Induction System May., 1952 Stuart (Bendix) 33/361 - Flux
gate 2nd harmonic
metal
Laminated? core dual winding
2671275
Magentometer Mar., 1954 Burns (RCA) 33/361 - Flux gate 2nd
harmonic
ferrite core
3133244
Magnetic Field Detector and Resolver having a two Section Housing
for the Detector May., 1964 Wojtulewicz (General Precision) 33/356
-
long slender rod
saturable inductor
3135199
Magnatometer Jun., 1964 Brown 324/43 - reports total field using 3
orthogonal square law
rod
sensors
3584388
Heading Reference System Jun., 1971 Petrov et al. 33/349 -
3628254
Nonpendulous Flux Valve Compass System Dec.,
1971Burmeister(Sperry Rand) 33/225 - strapped-down syncro resolver
type
3678593
Compass System and Components Therefor Having Automatic Feild
Cancellation Jul., 1972 Baker (Sperry Rand) et al. -
"Y" core
3696518
Vehicle Direction Sensing and Steering Systems Using Magnetic Flux
Responsive Means Oct., 1972 Leat 33/357 - two
fine wire cores
Older Patents have Images only
3903610
Apparatus for Measuring Magnetic Field Direction - 288 kHz divided
to 400 Hz, triangle drive, the SIN adn COS coil utputs are "in
resolver format", 2nd harmonic is bandpass filtered, phase detector
as part of a PLL. PLL ooutput is phase compared to drive signal
using digital counter with 1 deg per count.
3889181
Magnetic System for Discriminating, Charles B. Greer (Army), Jun 10
1975, 340/943 ; 340/554; 340/941
Vehicle and people channel is 0.1 to
2 Hz and Vechicle only channel is 6 to 40 Hz on the "magnetic
signatore"
| 3343079 |
Apparatus and method for
electromagnetically distinguishing between outside and
inside flaws in magnetizable members utilizing a leakage
field detector |
September 1967 |
Crouch |
| 3508238 |
Intrusion detection system |
April 1970 |
Baker |
| 3609679 |
Earth field vehicle detector
|
September 1971 |
Updegraff et al. |
| 3723988 |
Anisotropic thin film plated wire line
sensor
|
March 1973 |
Kardashian |
| 3727206 |
Personnel-vehicle intrusion detection
system
|
April 1973 |
Geil et al. |
| 3745450 |
Metal detection system for indicating the
motion and direction of motion of a body having magnetic
properties
|
July 1973 |
Wilt |
| 3754223 |
Intruder detection system
|
August 1973 |
Shtrikman |
| 3812484 |
Perimeter intrusion detection system (GTE
Sylvaina, Mtn View
|
May 1974 |
Miller et al. |
Ceramic used as form for magnetic
material
References:
| 2219107 |
Electron discharge device
|
October 1940 |
Langmuir |
| 2722734 |
Reconstruction of chemical equipment
|
November 1955 |
Grant |
| 2981885 |
Saturable measuring device and magnetic
core therefor
|
April 1961 |
Schonstedt |
| 3076930 |
Adjustable magnetic core
|
February 1963 |
Schonstedt |
replaces relays and motors with
vacuum tubes. The prior art devices were both sensitive to
air drop shock and generated magnetic fields that caused problems.
Also the power used is reduced. Uses "magnetic signature".
3840726
Position Locator - combines 3-axis fluxgate and gravity and steps
3835784
Mine Fuse, Miller et al. (Army), Sep 17 1974, 102/218 ;
102/209; 102/402 - anti-tank uses "magnetic signature"
Moving tanks or other armored
vehicles have several phenomena, herein called signatures,
associated with them -- e.g., weight, vibration, and magnetic
field.
A reed senses vibration and a disk connected to a bar magnetic
rotates in response to changes in mag field.
3833901
Magnetic Compass Having Remote Digital Readout - compass card that
can be read digitally
3825823
Aparatus for Detecting the Direction of a Magnetic Field Relative to
a Marker Direction Sequentially Scanning Plural Stationary Sensors -
title says it all
3778703
Apparatus for Detecting Unlevelness of a Pendulously Supported Flux
Valve by Subjecting the Valve to a Vertical Magnetic Field - used
for calibrating flux valves so that their center of mass casues them
to hang true.
3775674
Flux Gate Gradiometer using a Pulse generator to Drive the
Energizing Windings as well as Actuate the Detector - USAF - Class 324/253
- 12 uS on 500 uS period
3722409
Mine Firing Control Appratus, Plumley, Mar 27 1973 [application: Aug
28 1943], 102/417 ; 102/209 - 30 year delay in
publishing
uses "magnetic signature"
3714523, 3714559, 3829883
Magnetic Field Sensor Jan 30, 1973 TI, 257/252; 257/426;
257/E29.323; 324/252; 327/510; 327/581 a dual
insulated gate FET
3705980
Controlled Magnitude Repeater for Synchro and Resolver Signals -
servo based output but sin/cos out of fluxgate
3681711
Blocking Oscillator with Extended Variable Pulse Aug 1, 1972 331/112;
327/191; 331/149
3678593
Compass System and Components Thereof Having Automatic Field
Compensation - Sperry Rand - "Y" core & nulling Earth's field
Filed 1968, issued 1972. Uses "Y" core.
3649908
Magnetic Field Gradiometer Utilizing a Pair of Cores Driven by a
Blocking Oscillator "Brown"
- Navy
- 2 cores, for sea mines
3605011
Control Apparatus - single coil with PWM output- non directional 500
uW
3601899
Single Core Solid State Compass - Navy -Goniometer as prior art
3548284
Synchro Data Transmission Apparatus ... - not Compass
3546579
Thin-Ferromagnetic-Film Magnetoresistive Magnetometer sensitive to
easy axis Field Components and Biased to be insensitive to Hard axis
Field Components, Dec 8, 1970 Sperry Rand, Minneapolis 324/252
- may be the Honeywell Patent
3541432
Magnatometer Capable of Operating with a Very Low Input Power - core
is spiral wound tape
3509424
Fluxgate magnetometer drive circuit, George
T Inouye, TRW,
1970-04-28, - minimizes second harmonic in drive signal.
3460029
Magnetometer Incorporating Probe in the form of a Saturable
Ferromagnetic Core Subjected to the Magnetic Field to be Measured
and to an Auxiliary Exciting Alternating Field - not 2nd harmonic,
but rather direct comparison of the currents for + and - saturation
of the core
3448376
Fundamental frequency ring core flux gate magnetometer, US
Navy, 3 Jun 1969, 324/253
-
3416072
Thin Film Magnetometer Employing Phase Shift Discrimination 324/249
Dec 10, 1968 - RF frequency change
3403329 Flux-gate magnetometer with magnetic
amplifier, Geyger
William A, US
Navy, Sep 24, 1968, 324/254 - Ring core
3344379
Magnetically Operated Electrical Switch, Warren P. Morrow (Army),
Sep 26, 1967, 335/206 ; 102/427 - "magnetic signature" tank
mine
3319161
Flux Gate magnetometer Utilizing a Thin Helical Strip of Magnetic
Material as its Core -
3260932
Magnet-Field Mesuring Device with Galvanomagnetic Probe July 12,
1966 324/252; 338/32R - adding AC mag field to
Hall device
3258687 Wide range linear fluxgate magnetometer,
NASA, 28 Jun 1966, 324/253 - (l
gamma: 10 gauss) - adds triangle wave drive around conventional FG
and time interval counter. *******
3252081
Optical Magnetometer and Gradiometer, May 17, 1966, K.A.
Ruddock 324/301; 324/304; 331/3
3233332
Earth's Magnetic Field Responsive Systems - Synchro "Y" type cores
3218547
Flux Sensing Device Using a Tubular Core with Toroidal Gating Coil
and Solenoidal Output Coil Would Theron - NASA -
for 0.1T(?) fields (like in
outer space) looks like a difficult to wind cylinder
3185947
Inductive Module for Electronic Devices - printed inductor - not
compass
3172032
Magneto-Resistive Device Mar 2, 1965 323/294; 324/252;
338/32H; 338/32R; 365/158; 708/841 - more on Hall effect + MR
3135199
Magnatometer T. B. "Brown" 102/417 ; 102/212; 324/247;
324/253 - three orthogonal sensors for sea mine total field (i.e.
position independent) -
Fluxgate with oscillator to driving
coil
3109985
Magnetoresistive Elements and Devices Nov 5, 1963 323/368;
310/27; 310/72; 324/252; 338/32R; 365/158 -
using Hall effect (when the output
of a Hall sensor is short circuited, the resulting current
increases the sensitivity of the device).
3077538
Aparatus for Measuring Radiant Flux Feb 12, 1963 250/352;
324/224; 324/248;
374/122; 505/849
3031766
Magnetic Compass Compensating System - similar to 2,924,865/6
3202912
Method of Utilizing Tunnel Diodes to Detect Changes in Magnetic
Fields Aug 24, 1965 - only usable at very high field levels, not
Earth
3136944
Total field magnetometer having
series connected inductance elements for substantial removal of
even harmonics, Filed:Aug 6, 1945, Pub:Jun 9, 1964, 324/247, 102/212
- depth charge
3052827
Magnetic Discriminator, D. E. Olsen, Sep 4, 1962, 361/180 ;
324/101; 324/117R; 324/258; 324/98; 361/204
a single transistor oscillator works
with feedback winding on sensing transformer to detect "magnetic
signature"
3040248 Self-balancing
flux-gate magnetometer, Geyger
William A, US
Navy, Jun 19, 1962, 324/253 - parallel rods
3040247
Magnetic field detector, Roland
L Van Allen, 1962-06-19, 324/253 -
2-transistor, dual coil, FCM
3020843
High gain
signal amplifying device adapted for use with a marine mine, Brown
Charles B, Macdonald
Wadlron S, (SECRET for 20 years) Jun 4,
1942, Feb 13, 1962,
102/417,
336/155,
324/258
Calls 2406870
3017833
Magnetic Firing Control Mechanism for a Mine, S.W> Booth, (not
assigned) Jan 23, 1962 [application: Jun 8, 1943],
102/417 ; 318/444; 318/450
cam and motor based timing mechanisim can survive air drops better
than stepping relay, uses "magnetic signature"
3015273
Magnetic Mine Firing Control Mechanism, R. H. Park et al (not
assigned), Jan 2, 1962 {application: Apr 6, 1942], 102/417
not sensitive to magnetic storms or
movement of the mine due to tides but will trigger when a large
metal object goes by
References:
Publication
Priority Publication Assignee Title
542732 1895-07-16
huskisson Submarine Mine
571739 1896-11-24
Electromagnetic sentinel
1310568 1919-07-22 Acoustically
Operated Electric Contact Actuating Mechanism and System
Employing the Same
GB130350 1917-12-27
1919-08-07 Robert BeattieImprovements in Electromagnetic
Methods of Detecting Submarines.
1364615 1919-12-29
1921-01-04 Cruz Julio Lopes Valente DaElectrical firing
of explosive mines
1382374 1917-08-30
1921-06-21 Maxim HudsonMethod and mechanism for
exploding submarine mines
1491004 1918-11-18
1924-04-22 Us GovernmentExplosive mine
1538316 1918-02-08
1925-05-19 GovernmentExplosive mine
FR803907 1936-03-31
1936-10-12 Anciens Ets Sautter HarleImprovements in
underwater mines
2238072
Method and means for Locating Concealed Bodies, Nelson et al.
(Western Union Telegraph), Apr 15 1941,
324/67 ; 102/406; 324/243;
324/326; 324/345; 405/173
a towed sled contains a ghradient detection system
2399523
Control System and Device therefore for submarine mines, Van Atta
et al., Apr 30 1946,
102/417 ; 29/455.1 - resistant to
sweeping
318/647; 33/361; 174/153R;
318/653; 323/362; 324/207.17; 324/207.25; 324/249;
324/253; 336/110; 336/188; 336/218; 340/870.33 - Fluxgate, freq
doubler
3011440
Mine Firing Mechanism, Hugh Bradner 9not assigned), Dec 5, 1961
[application: Sep 13, 1944], 102/417 - "magnetic signature"
3010395
Mine Firing Mechanism, W. R. Maltby (not assigned), Nov 28 1961
[applifcation: Oct 19, 1943], - 28 year delay in publication -
combines magnetic and accoustic
sensors "magnetic signature" uses stepping relays
2998727
Heading Reference System for Navigable Craft SEP5 1961 - parallel rod flux gates 400 Hz in
800 Hz out
2997648
Magnetic Field Detector Aug 22, 1961 324/252;
318/647; 338/32R; 340/870.43 uses square law change in resistance of
Permalloy
2993440
Congtrol Device (Mine Firing)
2991414
Electrical apparatus, Robert
M Tillman, Burroughs,
1961-07-04, - tape wound ring core, 2-transistor flip-flop
drive, the flux in all directions effects this oscillator.
2963658
Magnetic core multivibrator circuit, Robert
W Rochelle, 1960-12-06, 331/113A; 307/401; 327/190 - square B-H
curve, Not a magnetic sensor, just a F-F
2959896
Error Compensated Directional Systems - vry similar to 2,959,865 but
specific for deviation compensation electronically not with magnets
2959865
Electrical Error Compensation Arrangements - for improving Fluxgate
compass systems
2957145
Transistor Pulse Generator Oct 18, 1960 331/112; 331/109 -
becomes a magnetometer when the proper type of transformer is used
2924886
Transmitting Magnetic Compass Systems - Hall effect sensor tracks
the needle of a normal compass
2922227
Transmitting Magnetic Compass Systems - ring of mu metal senses
needle of normal compass
2920562
Mine Firing Mechanisim - "magnetic signature"
2892404
Pressure Responsive Device - combines pressure and "magnetic
signature"
2887782
Gyro Magnetic Compass System - adds synchro that is turned by a
geared motor to allow rapid alignment of the directional gyro
2881702
Mine Firing Mechanism, Glennon et al. (not assigned), Apr 14
1959 [appliation: Aug 9, 1941] 102/417 ; 102/212;
102/402
mentiones "magnetic signature" and
uses it in sea mine
2852859
Flux valve Compensating System - "Y" core combines directional gyro,
vertical gyro and Coriolis compensation
2828396
Magnetoresistive Device Mar 25, 1958 338/32R; 324/252;
327/510; 330/62; 338/234; 338/308
2755562
Compass System - Bendix - Flux Valve senses a compass needle
2744235
Magnetic Field Extrapolating Apparatus and Method, G. Breit, May 1
1956 [app: Feb 4, 1946], 324/200 ; 335/220
the variation of the ship's magnetic
field along some straight line parallel to the keel is called the
ship's magnetic signature.
2770774
Balanced magnetometer, Henry B
Riblet, Navy,
App: 1944-05-10, W.W.II, Pub: 1956-11-13, 324/253; 340/870.33 - balanced
transformer drive two coils balanced to the secondary center tap.
2671275
Magnetometer March 9, 1954 33/360; 33/361; 324/247; 331/40
Claims to be the first Magnetometer
where there are no moving parts. Simple Two Terminal Coil (TTC)
type sensor.
Inductance of coil is a function of mag field and is used to
control the frequency of an oscillator. This is mixed with a
frequency determined by a crystal oscillator to produce a new
frequency which has larger percentage changes with field strength.
The mixing scheme can be used with the FGM-3 sensors.
2652545
Deviation Compensor - uses multiple serews in a circle to compensate
compass systems
2611191
Telemetric or Repeatere system - Repeats a compass needle
2599550
Fluxmeter and Probe Therefore, Jun 10, 1952 324/252;
338/10; 338/32R; 338/229 MR bridge
2555209 Method and apparatus for measuring
the values of magnetic fields, Gary
Muffly, Vacquier
Victor V, Gulf
Research Development Co, Nov 1, 1943, May
29, 1951 -
Key use detecting submarines from aircraft (maybe why
the 8 year delay in publication).
Calls:
1895373
Apparatus for measuring magnetic fields, Brucke (Gen Electric),
Jan 24, 1933, 324/250, 33/360
deflection of cathode ray tube mounted on
transit
1919982
Compass Mayer, et al (Gen Electric), Jul 25, 1933, 33/360,
340/971, 324/250
deflection of cathode ray tube
1988521
Gyro earth inductor compass, Sperry, Jr.(Sperry Gyroscope Co Inc),
Jan 22, 1935,
3/317.00R, 324/246, 33/316, 324/345, 33/362,
33/321
combined Earth Inductor and gyro
2016977
Direction responsive system, Thomas (Gen Electric), Oct 8, 1935,
33/361, 340/870.32, 324/255
One of the early flux gate patents done to
eliminate the moving parts of the induction compass (Wiki)
2027393
Cathode ray device, McCreary, Jan 14, 1936,
33/360, 348/827, 361/191, 318/675, 324/250,
315/8, 33/363.00L, 33/355.00D, 318/293, 315/364
CRT on motorized Az/El mount
2047609
Magnetic field direction and intensity finder, Antranikian, Jul
14, 1936, 33/301, 33/362, 324/247, 340/870.33
Flux gate type - rotatable sensor and L - R
instrument to maintain aircraft course (not spinning induction
compass wear)
2124825
Process and apparatus for the indirect determination of earth and
air-electrical conditions, Machts et al, Jul 26, 1938
324/344, 324/345, 324/257, 324/334
CRT senses both magnetic and electrical fields
2213357
Direction indicating means, Barth (Siemens ), Sep 3, 1940, 3/361,
324/253
parallel rod flux gate
2246259
Apparatus for making geophysical or other measurements, Machts,
Jun 17, 1941, 324/345, 324/250
CRT with Left and Right targets to drive vacuum
tube and meter
2325365
Magnetic compass, Britten (Monroe Calculating Machine), Jul 27,
1943,
33/357, 324/259, 33/358, 33/360, 33/363.00K,
324/244
photo electric reading of a needle compass
2412612
Directive radio system, Godet (Gen Electric), Oct 8, 1941, Dec 17,
1946,
342/425, 244/3.19, 318/675, 89/41.7, 318/16,
343/765, 244/177, 327/519, 318/478, 342/78
SCR-584 (Wiki) fire control radar?
2468968
Magnetic field strength indicator, Felch et al (Bell Telephone
Labs), Apr 20, 1943, May 3, 1949
324/246, 340/870.33, 324/253, 324/345
3-axis flux gate
2542018
Compass Feb 20, 1951 33/360; 33/362; 33/363Q; 73/504.14 -
vibrating master compass to drive slaves
2535068
Submarine Detecting Device, F.A. Johnson (not assigned), Dec 26 1950
[application Sep 6, 1941], 89/1.61 ; 102/402; 102/417;
114/18; 324/257; 434/1
uses a gradient method to cancel the
Earth's mag field and mentions "magnetic signature"
2519058
Deviation Compensator - just correction of deviation for use with
gyros
2502786
Telemetering of compass Indication - Wurlitzer - 2 pots allow 360
degree operation
2491736
Magnetic Pickup Device and Method of Balancing the Device Dec 20,
1949 324/245;
324/253; 340/870.33; 340/870.43
2485931
Magnetic field strength indicator, Slonczewski
Thaddeus, Bell
Labs, App: 1943-04-20, W.W.II, Pub: 1949-10-25, - 3 orthogonal
rods
2476723 by
L. F. Beach, referenced in 3012177 but is a typo
2474693
Magnetic field responsive device, Robert
G Rowe, App: 1945-01-31, W.W.II, Pub: 1949-06-28, 324/244; 33/362; 33/361; 324/209 -
based on the idea of magnetostrictive materials changing length
2475593
Self Synchronous Flux Valve System - coil output frequency divided
by 2 (not doubled) to drive a Selsyn and to have less distortion
2454184
Telemetric Compass - continuous pot, 4 taps, wiper at ground
2436394 Magnetic detector, Maltby
Wilson R, Park
Robert H, Jun 6, 1941, Feb 24, 1948, 102/417, 324/258,
336/90, 340/850, 336/233
- End caps greatly increase mag field
2426470
Remote Indicating Magnetic Compass System - deviation compensation
2415985
Permanent Magnet Telemetric System Feb 18, 1947 318/693; 324/252;
338/32R; 340/870.34; 340/870.38 uses MR elements in a "Y"
configuration as the input and what amounts to a synchro as the
output, but driven by a DC battery.
I think this is the introduction of the
modern flux gate that's 10 to 100 times more sensitive than prior
art sensors. It enabled the use of MAD for sub hunting.
2406870 Apparatus for responding to
magnetic fields,
Vacquier
Victor V (Wiki),
Gulf
Research Development Co, Filed: Jul
21, 1941, (W.W.II) Pub: Sep 3,
1946
324/253, 102/417, 33/361,
318/647, 324/326, 324/345,
324/255, 340/870.33, 102/427
2407202 Apparatus for responding to
magnetic fields, Vacquier
Victor V, Gulf
Research Development Co, Jul 21, 1941, Sep
3, 1946,
324/253, 340/870.33, 324/255, 324/345
Matching priority date as above patent and uses the same
balanced flux gate approach.
This patent also mentions submarines.
A prior patent by Vacquier for logging oil wells:
2281960 Apparatus for logging bores, Vacquier
Victor V, Gulf
Research Development Co, Jul 26, 1939, 73/152.16, 367/25, 367/86
- but this is not the sensitive magnetic sensor
2390051 Means for measuring magnetic fields, Gustav
Barth, Filed: 15 Jul 1941, 324/253, 340/870.33,
318/513 - rod type flux gate (German)
2383461
Flux Valve - Sperry Gyro Filed: Jan 19, 1943 - 8 or 12 sided polygon
with a coil on a bar as each leg -
2383461
Flux Valve Compass System - Sperry Gyro - 120 deg "Y" core
2383460
Magnetic Field Responsive Device - "Y" core
Filed 1941, Issued Aug 1945. Adds both a second harmonic
filter and feedback to null the Earth's filed in each sense coil.
2357319
Flux Valve Magnetic Compass - Sperry Gyro - "Y" core outputs look
like a Selsyn, pendulum to keep horizontal
Filed 1940, Issued Sep 1944. This appears to be
the Start of what we now call the fluxgate compass (see 2047609
for prior art).
Uses a frequency doubler to drive the indicator although that's
not a part of the claims.
2342637
Means for reproducing Motion - electrical circuit to remotely read a
compass
2335117
Magnetic Surveying Aparatus, E.P. Harrison Nov 23, 1943 324/252;
106/DIG.7; 324/345 MR with A.C. drive & amplification
2321355 Surgical probe for locating foreign metal particles in body
tissue, Samuel
Berman, Waugh
Equipment Co, Jun 8, 1943,
600/11, 336/233,
336/90, 336/170, 340/686.1,
324/239, 324/260, 324/326,
324/67
Used at Pearl Harbor to detect shrapnel in
tissue. Works by balance so may or may not be a Flux
gate. also see Waugh MW3 & MW4
2308566
Magnetic Repeater or Compass - fluxgate senses compass needle
2269602
Means for reproducing motion - This is the heart of Synchro, Selsyn,
etc.
Filed 1939, issued 1942. Three wires connect two
devices. The signals are separated by 120 degrees.
There is a drive coil so each device has 5 terminals.
2260589
Magnetic Flux Meter, G.S. Smith Oct 28, 1941 324/252;
324/117H uses MR bridge using Bismuth wire (oldest MR sensor patent)
|
2252059
Method and a device for
determining the magnitudes of magnetic fields, Gustav
Barth, Priority: 24 Dec 1936, 324/253, 102/427, 102/417, 340/870.33, 33/361 |
2158500
Magnetic Filed Direction Finder - 33/361; 324/247; 324/254 -
iron nickel alloy with very high permeability rods
2053154
Direct Current Indicator - "Y" core driven with DC and AC that can
detect magnetic flux
Filed 1935, Issued 1936. The second harmonic has
been discovered. This patent is mainly aimed at a new way to
measure DC currents, but it states that the device can also be
used for measuring magnetic flux.
2047609
Magnetic Field Direction and Intensity Finder - Compass with
saturating magnetic cores rotated to null
Filed 1933, Issued 1936. This Flux Valve
(the first time this term was used according to patent 2357319) is an
improvement over the needle type compass and over the "inductor"
type compass that uses a coil that is rotated with a motor to
sense the Earth's magnetic field.
This patent uses two coils at right angles and rectifies the
sensor coils output and sums them in a galvanometer so that the
indicator needle shows "0" when on course. The whole sensor
is mechanically rotated to set the desired direction.
1988521
Gyro Earth Induction Compass, Jr
Elmer A Sperry, Bruno
A Wittkuhns, Sperry
Gyroscope, Jan 22, 1935 33/317R; 33/316; 33/321;
33/362; 324/246; 324/345 - combines an Earth Inductor
compass with gyroscope.
1886336
Induction Compass Nov. 1, 1932 33/362; 33/361;
324/253; 340/870.33 - Course indicator with R(ight) - 0 - L(eft)
indicator
1863415
Magnetometer June 14, 1942 F. Rieber (GE) 324/256;
33/361; 33/362; 340/870.33 - vibrating wire in gap with mag field -
to replace compass needles and rotating field induction meters.
1840911
Induction Compass, Minorsky
Nicolai,
Filed 1925, issued 1932. Class 33/301
This was part of the state of the are prior to the Flux Valve.
This patent removes the effect of the vertical component of the
Earth's magnetic field by using two counter rotating
coils. The coils are driven by Pelton wheels fed high
pressure air so as to not have any magnetic field disturbing the
sensors. Vacuum tubes are used for signal processing.
Re Issued
19038 - 1934
1778795
Electrical Measuring Instrument Oct 21, 1930 P. H. Craig 324/120;
310/26; 324/76.11; 324/101; 324/115; 324/251
- "Corvino effect" (Wiki)
or "Hall effect" (Wiki) device.
1525844
Vacuum Tube Apparatus Feb 10, 1925 313/157; 324/250
(plate current varies with mag field)
1454592
Wireless Direction Finding Means for and Method of Piloting
Aircraft, May 8, 1923 342/441; 324/247;
340/979; 342/448 - Radio Direction Finding
1448050
Compensation System for Compasses Mar 13, 1923 33/301;
33/356; 33/357; 324/244
711131 (711445: Tx)
Art of Transmitting Intelligence Oct 14, 1902 329/347; 324/252
(the resistance of Bismuth may vary with magnetic field) - Radio
receiver
661520
Automatic Steering Device for Torpedo, Nov 13, 1900, 114/21.1
; 114/20.1; 318/283; 324/243 -
supposed to home on the ferrous metal of target
RE23397 (2468968)
Magnetic Field Strength Indicator, Edwin P. Felch & Thaddeus
Slonczewaki, Bel Telephone, (April 1943) Aug 7, 1951 324/246;
318/34; 318/647; 324/253; 324/345
RE21970 (2206018)
Earth Inductor Compass Dec 9, 1941 33/362; 33/361; 324/247;
324/258 - Y core, 3-phase output & single phase drive to the
flux valve
| 6850057 |
Barber pole structure for magnetoresistive
sensors and method of forming same |
| 6831458 |
Magnetic differential field sensor using
hysteresis field in AMR films |
| 6750751 |
Integrated magnetic signal isolator with
feedback |
| 6717403 |
Method and system for improving the
efficiency of the set and offset straps on a magnetic
sensor |
| 6700371 |
Three dimensional conductive strap for a
magnetorestrictive sensor |
| 6529114 |
Magnetic field sensing device |
| 6376933 |
Magneto-resistive signal isolator |
| 6304082 |
Printed circuit boards multi-axis
magnetometer |
| 6297628 |
Magnetoresistive bridge array |
| 6232776 |
Magnetic field sensor for isotropically
sensing an incident magnetic field in a sensor plane |
| 5952825 |
Magnetic field sensing device having
integral coils for producing magnetic fields |
| 5667879 |
TaN/NiFe/TaN anisotropic magnetic sensor
element |
| 5644230 |
Miniature magnetometer and flexible
circuit |
| 5596272 |
Magnetic sensor with a beveled permanent
magnet |
| 5572058 |
Hall effect device formed in an epitaxial
layer of silicon for sensing magnetic fields parallel to
the epitaxial layer |
| 5500590 |
Apparatus for sensing magnetic fields
using a coupled film magnetoresistive transducer |
| 5477143 |
Sensor with magnetoresistors disposed on a
plane which is parallel to and displaced from the magnetic
axis of a permanent magnet |
| 5455510 |
Signal comparison circuit with temperature
compensation |
| 5435070 |
Simplified compass with multiple segment
display capability |
| 5351005 |
Resetting closed-loop magnetoresistive
magnetic sensor |
| 5247278 |
Magnetic field sensing device |
| 4847584 |
Magnetoresistive magnetic sensor |
| 4589038 |
Position sensor |
| 4533872 |
Magnetic field sensor element capable of
measuring magnetic field components in two directions |
| 4447781 |
Magnetoresistive transducer apparatus |
| 6946834 |
Method of orienting an axis of
magnetization of a first magnetic element with respect to
a second magnetic element, semimanufacture for obtaining a
sensor, sensor for measuring a magnetic field |
| 6756782 |
Magnetic field measuring sensor having a
shunt resistor and method of regulating the sensor |
| 6580270 |
Magnetoresistive sensor or memory elements
with decreased magnetic switch field |
| 6577124 |
Magnetic field sensor with perpendicular
axis sensitivity, comprising a giant magnetoresistance
material or a spin tunnel junction |
| 6501678 |
Magnetic systems with irreversible
characteristics and a method of manufacturing and
repairing and operating such systems |
| 6501271 |
Robust giant magnetoresistive effect type
multilayer sensor |
| 6501261 |
Evaluation circuit for a magnetoresistive
sensor |
| 6486662 |
Magnetic field sensor comprising a
spin-tunnel junction |
| 6384600 |
Magnetic field sensor comprising a spin
tunneling junction element |
| 6275033 |
Magnetic field sensor having nickel oxide
and cobalt containing ferromagnetic layers |
| 6225802 |
Apparatus for automatic measurement of
resistance of integrated MR device |
| 6215301 |
Magnetoresistive detector comprising a
layer structure and a current directing means |
| 6100686 |
Magnetic field sensor with double
wheatstone bridge having magneto-resistive elements |
| 6075361 |
Device for detecting a magnetic field |
| 5936402 |
Magneto-resistive magnetic field sensor
with a constricted region |
| 5904996 |
Method of manufacturing a magnetic field
sensor |
| 5689185 |
Compact device for measuring magnetic
fields having magnetoresistors and an auxiliary magnetic
field generator |
| 5686837 |
Magnetic field sensor and instrument
comprising such a sensor |
| 5602471 |
Angle sensor including angularly spaced
sensor units |
| 5583436 |
Miniature magnetic field sensor with
compact magnetization coil |
| 4694248 |
Magnetic field sensor compensated for
offset error |
| 4686472 |
Magnetic sensor having closely spaced and
electrically parallel magnetoresistive layers of different
widths |
| 4617600 |
Magnetic head having a thin strip of
magnetoresistive material as a reading element |
| 4568906 |
Sensor having a magnetic field-sensitive
element with accurately defined weight and thickness
dimensions in the nanometer range |
Active Impulse Magnetometer (AIM)
3105934
Method and apparatus for the remote detection of ore bodies
utilizing pulses of short duration to induce transient
polarization in the ore bodies (Selco
Exploration Company Ltd)
3852659
Geophysical prospecting method and apparatus utilizing correlation
of received waveforms with stored reference waveforms (Barringer
Research Ltd)
5025218
Pulsed field system for detecting the presence of a target in a
subsurface environment (US Navy)
5525907
Active impulse magnetometer with bipolar magnetic impulse
generator and fast fourier transform receiver to detect
sub-surface metallic materials (Hughes)
Related
CRT-1 the first U.S. Sonobuoy
used in conjunction with MAD.
Sonobuoys & Vietnam era outdoor
intrusion detectors based on them.
HP 428 Clip-on Milliammeter - is a Flux
Gate magnetometer
3 Axis Magnetometer
Aircraft Pilot's Standby Magnetic
Compass
DC Gaussmeter Model 1
AMY6 Magnetic
Polarity Tester
GE
Gauss Meter & Reference Magnet
DC Permanent Magnet Motors
Experiment Relating to the Vertical
Component of the Earth's Field using digital wrist compass
Electromagnet Toy Engine
Fluxgate (& other) Patents - This page
Helmholtz Coil
Sensitive Research Instrument Co. Fluxmeter
Annis
M25 Pocket Magnetometer
Cenco Scientific 79860 Dynamo Analysis
Apparatus - works with Fluxmeter
Home Built Magnetometers
HT20 2000 mT
Magnetic Flux Meter- DC but not sensitive to Earth's field
KVH C100 Flux Gate Compass module
Magnetics
Magnetic
Locators
Magnetic
Recording
Magnets Permanent magents &
electromagnets
MC1 MC-1 Magnetic Compass Calibration Set
similar to AN/ASM-344
Sensors - Magnetic
Weeden-El-Mtr Weeden DC
Electromagnetic Machine (Motor or Generator) & Carbide
(acetylene) Gas Cannon
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