US3701007A — Magnetometer consisting of two sensors with means…

Claim 1

Independent Claim 220 words

A highly sensitive magnetometer for sensing and measuring a magnetic field, comprising first and second sensor elements, each sensor element including a saturable core carrying a primary winding and a secondary winding, and each said secondary winding producing an output corresponding to a component of the sensed magnetic field; a source of alternating current for driving said primary windings with a current of predetermined frequency and amplitude; null balance means for each said sensor element to compensate for undesired output signals and establish a null condition in said magnetometer; detector means including first and second diodes connected to said secondary windings on said first and second sensor elements, respectively, to receive the outputs from said secondary windings and produce direct current output signals corresponding to said components of said sensed magnetic field; unbalancing means for each sensor element including an unbalancing circuit for feeding into each secondary winding a signal proportional to and synchronous with the alternating drive current applied to the corresponding primary winding, the amplitude of the current fed to said secondary windings being sufficient to overcome the threshold of said diodes at said null condition whereby said detector means will respond to very low level outputs from said secondary windings due to very small sensed magnetic fields; and means for amplifying and indicating said detector output signals.

Claim 2

Dependent Claim 220 words

A highly sensitive magnetometer for sensing and measuring a magnetic field, comprising first and second sensor elements, each sensor element including a saturable core carrying a primary winding and a secondary winding, and each said secondary winding producing an output corresponding to a component of the sensed magnetic field; a source of alternating current for driving said primary windings with a current of predetermined frequency and amplitude; null balance means for each said sensor element to compensate for undesired output signals and establish a null condition in said magnetometer; detector means including first and second diodes connected to said secondary windings on said first and second sensor elements, respectively, to receive the outputs from said secondary windings and produce direct current output signals corresponding to said components of said sensed magnetic field; unbalancing means for each sensor element including an unbalancing circuit for feeding into each secondary winding a signal proportional to and synchronous with the alternating drive current applied to the corresponding primary winding, the amplitude of the current fed to said secondary windings being sufficient to overcome the threshold of said diodes at said null condition whereby said detector means will respond to very low level outputs from said secondary windings due to very small sensed magnetic fields; and means for amplifying and indicating said detector output signals.

Claim 3

Dependent Claim 44 words

The magnetometer of claim 1, wherein said unbalancing circuit includes means for connecting the primary winding of each sensor to its corresponding secondary winding to feed directly to each secondary winding a portion of the alternating drive current applied to the corresponding primary winding.

Claim 4

Dependent Claim 16 words

The magnetometer of claim 2, wherein said components of the sensed magnetic field are vector components.

Claim 5

Dependent Claim 15 words

The magnetometer of claim 3, wherein said first and second sensor elements are mutually perpendicular.

Claim 6

Dependent Claim 27 words

The magnetometer of claim 2, wherein said unbalancing circuit means comprises a resistor-capacitor loop connected between the primary and its corresponding secondary winding of each sensor element.

Claim 7

Dependent Claim 40 words

The magnetometer of claim 5, wherein said unbalancing means further comprises an unbalanced primary winding on each said sensor element whereby said primary winding induces a different flux in different portions of the sensor core on which it is wound.

Claim 8

Dependent Claim 13 words

The magnetometer of claim 1, wherein said means for indicating includes recorder means.

Claim 9

Dependent Claim 43 words

The magnetometer of claim 2, wherein said null balance means comprises a null balancing circuit having first and second independently variable direct current outputs, and means for applying said first and second null circuit outputs to said first and second sensor elements, respectively.

Claim 10

Dependent Claim 46 words

The magnetometer of claim 8, wherein said null balancing circuit comprises a regulated source of positive and negative direct current, and potentiometer means connected across said regulated source of direct current for selecting the polarity and amplitude of said first and second variable direct current outputs.

Claim 11

Dependent Claim 28 words

The magnetometer of claim 9, wherein said first and second variable direct current outputs are connected to the secondary windings of said first and second sensor elements, respectively.

Claim 12

Dependent Claim 44 words

The magnetometer of claim 10, further including selector switch means for connecting either one or the other of said variable direct current outputs to its corresponding secondary windings, whereby a null balance condition will be established in only one sensor element at a time.

Claim 13

Dependent Claim 47 words

The magnetometer of claim 11, wherein said selector switch means further includes means for connecting said means for amplifying and indicating to the detector means corresponding to the selected sensor element, whereby only one sensor element at a time is used to sense an external magnetic field.

Claim 14

Dependent Claim 33 words

The magnetometer of claim 10, further including isolating means between said null balance means and said detector means for preventing said first and second variable direct current outputs from affecting said detector outputs.

Claim 15

Dependent Claim 29 words

The magnetometer of claim 1, wherein said null balance means comprises first and second sources of variable direct current connectable directly to said first and second secondary windings, respectively.

Claim 16

Dependent Claim 23 words

The magnetometer of claim 1, further including equalizer means connected to each of said first and second diodes for equalizing said output signals.

Claim 17

Dependent Claim 53 words

The magnetometer of claim 1, wherein said null balance means includes selector switch means for establishing a null condition in only one or the other of said sensor elements thereby to activate the selected sensor element, said selector switch further including means for connecting the activated sensor element to said means for amplifying.

Claim 18

Dependent Claim 16 words

The magnetometer of claim 1, further including means for operating each said sensor element in resonance.

Claim 19

Dependent Claim 26 words

The magnetometer of claim 17, wherein said means for operating each sensor element in resonance comprises capacitor means connected in parallel with each said primary winding.

Claim 20

Dependent Claim 47 words

The magnetometer of claim 18, wherein said null balance means comprises a null balancing circuit having first and second independently variable direct current outputs, and means for applying said first and second null circuit outputs to the secondary windings of said first and second sensor elements, respectively.

Claim 21

Dependent Claim 42 words

The magnetometer of claim 19, further including selector switch means for connecting either one or the other of said variable direct current outputs to a corresponding secondary winding, whereby a null balance condition will be established in only the selected sensor element.

Claim 22

Dependent Claim 41 words

The magnetometer of claim 20, wherein said selector switch further includes means for connecting the selected sensor element through its corresponding detector means to said means for amplifying, whereby said sensor elements may be alternately connected to said means for amplifying.

Claim 23

Dependent Claim 35 words

The magnetometer of claim 21, wherein said unbalancing means for each sensor element comprises circuit means for feeding to each secondary winding a portion of the alternating drive current applied to the corresponding primary winding.

Claim 24

Dependent Claim 34 words

The magnetometer of claim 22, further including isolating means between said null balance means and said detector means for preventing said first and second independently variable direct current outputs from affecting said detector outputs.

Claim 25

Dependent Claim 118 words

The magnetometer of claim 1, wherein each said saturable magnetic core comprises a generally rectangular core element having two parallel legs, said primary winding including two coils wound additively on the two parallel legs of said core element and said secondary winding including two coils wound in opposition on the said two parallel legs of said core element, whereby in the absence of external magnetic fields an alternating current applied to said primary winding produces substantially no resultant output in said second ary winding, an external field producing an output on said secondary winding which is proportional in amplitude and polarity to the component of the said external field which is parallel to the said two parallel legs.

Claim 26

Dependent Claim 26 words

The magnetometer of claim 14, wherein each of said secondary windings is connected to a load resistor, said detector means being connected across said load resistors.

Claim 27

Dependent Claim 58 words

The magnetometer of claim 25, wherein said first and second sources of variable direct current in said null balance means are connected to corresponding ones of said load resistors, said magnetometer further including isolating capacitors between said null balance means and said detector means for isolating said detector means from said first and second variable direct current sources.

Claim 28

Dependent Claim 49 words

The magnetometer of claim 26, wherein said unbalancing circuit means comprises a resistor-capacitor loop connected between the corresponding primary and secondary windings of each sensor element, the capacitors in said loops serving to isolate said primary windings from said sources of variable direct current in said null balance means.

Claim 29

Dependent Claim 19 words

The magnetometer of claim 27, wherein said source of alternating drive current is capacitively coupled to said primary windings.

Claim 30

Dependent Claim 22 words

The magnetometer of claim 27, further including capacitor means connected across each said primary winding for operating said sensor elements in resonance.

Claim 31

Dependent Claim 37 words

The magnetometer of claim 29, further including selector switch means for connecting only one of said sensor means through its corresponding detector means to said means for amplifying, said means for amplifying being a direct current amplifier.

Claim 32

Dependent Claim 30 words

The magnetometer of claim 30, further including equalizer means connected to each of said first and second diodes for equalizing said output signals before they are amplified by said amplifier.

Claim 33

Dependent Claim 86 words

The magnetometer of claim 31, wherein said detector means further includes third and fourth diodes, said first and third diodes being connected in opposition across the load resistor for said first sensor to produce a first direct current output signal and said second and fourth diodes being connected in opposition across the load resistor for said second sensor to produce a second direct current output signal, said selector switch means serving to connect either said first or said second direct current output signal to said amplifier.

Claim 34

Dependent Claim 21 words

The magnetometer of claim 26, wherein said unbalancing means further includes an unbalanced primary winding on each said saturable magnetic core.

Claim 35

Independent Claim 282 words

The method of operating a highly sensitive magnetometer to permit measurement of the strength and direction of magnetic fields having a field strength of the order of 0.01 gammas, said magnetometer including first and second sensor elements, each said sensor element comprising a saturable core member carrying a primary winding and a secondary winding, comprising the steps of: generating an alternating current of determined frequency and amplitude; driving the primary winding of each said sensor element with said alternating current and in resonance; generating regulated positive and negative direct currents; applying to a selected one of said sensor elements a portion of said direct current, the said portion being selectively variable as to polarity and magnitude to establish in the selected sensor element a null condition, whereby a sensed magnetic field will produce a measurable change only in the secondary winding of said selected sensor element; connecting the secondary winding of each sensor to corresponding detector diodes to convert alternating current outputs from said sensors due to the effects of sensed magnetic fields into corresponding direct current outputs; feeding to each secondary winding by way of corresponding resistorcapacitor loops a portion of said alternating drive current driving the corresponding primary windings, whereby each secondary winding produces a predetermined alternating output signal in said null condition sufficient to overcome the threshold of conduction for said detector diodes, whereby the desired outputs from said sensors due to said sensed magnetic fields are not blocked by said diodes; feeding the direct current outputs from said detector diodes through corresponding channels to equalizers to balance said channels; and amplifying and measuring the selected output signal to detect the magnitude and direction of said sensed magnetic field.

Claim 36

Independent Claim 282 words

The method of operating a highly sensitive magnetometer to permit measurement of the strength and direction of magnetic fields having a field strength of the order of 0.01 gammas, said magnetometer including first and second sensor elements, each said sensor element comprising a saturable core member carrying a primary winding and a secondary winding, comprising the steps of: generating an alternating current of determined frequency and amplitude; driving the primary winding of each said sensor element with said alternating current and in resonance; generating regulated positive and negative direct currents; applying to a selected one of said sensor elements a portion of said direct current, the said portion being selectively variable as to polarity and magnitude to establish in the selected sensor element a null condition, whereby a sensed magnetic field will produce a measurable change only in the secondary winding of said selected sensor element; connecting the secondary winding of each sensor to corresponding detector diodes to convert alternating current outputs from said sensors due to the effects of sensed magnetic fields into corresponding direct current outputs; feeding to each secondary winding by way of corresponding resistorcapacitor loops a portion of said alternating drive current driving the corresponding primary windings, whereby each secondary winding produces a predetermined alternating output signal in said null condition sufficient to overcome the threshold of conduction for said detector diodes, whereby the desired outputs from said sensors due to said sensed magnetic fields are not blocked by said diodes; feeding the direct current outputs from said detector diodes through corresponding channels to equalizers to balance said channels; and amplifying and measuring the selected output signal to detect the magnitude and direction of said sensed magnetic field.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1975-10-24	1976-04-24	1976-10-24	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1979-10-24	1980-04-24	1980-10-24	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1983-10-24	1984-04-24	1984-10-24	$7700.00	Window Closed / Lapsed

Magnetometer consisting of two sensors with means for unbalancing each sensor at null condition

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