Flux gate magnetometer including backing plate

Claim 2

A flux sensing head portion for a magnetometer which comprises a magnetic shield having a compartment therein and an aperture therethrough communicating with said compartment, a backing plate constructed of a low reluctance material mounted adjacent to said aperture outside of said compartment and positioned to permit passage of material to be examined between said aperture and said backing plate, a magnetic conductor mounted inside of said compartment in said shield and having a flux receiving end positioned adjacent to said aperture to receive magnetic flux extending through said aperture from said backing plate, said conductor also having a flux returning end positioned to return to said backing plate flux flowing through said conductor, and magnetic flux measuring means mounted adjacent to said magnetic conductor between the ends thereof for measuring magnetic flux passing through said conductor.

Claim 3

The apparatus of claim 1 in which said flux returning end of said magnetic conductor is connected to said magnetic shield.

Claim 4

The apparatus of claim 1 in which said magnetic conductor is generally U-shaped having a base portion remote from said aperture and a pair of leg portions extending therefrom toward said aperture and terminating in said ends thereof adjacent to said aperture, and a pair of said measuring means are provided, one mounted adjacent to each of said leg portions for measuring the magnetic flux flowing in said leg portions, said pair of measuring means being connected together to measure the sum of the magnetic flux flowing in both of said leg portions.

Claim 5

The apparatus of claim 1 in which said magnetic shield has portions thereof adjacent to said aperture which are generally parallel to said backing plate and terminate in edge of said aperture which are sloped away from said magnetic conductor as they extend into said compartment.

Claim 6

The apparatus of claim 1 in which said magnetic conductor contains an intermediate portion thereof made of a pair of separate magnetic conductor strips which are generally parallel and connected together at their adjacent ends; said magnetic flux measuring means comprises a pair of coils, one encircling each of said strips, oppositely polar drive leads connected to said coils to establish a closed magnet circuit through said strips and said connected ends thereof responsive to electric current in said drive leads, and oppositely polar detection leads connected to said coils to receive current from said coils responsive to the establishment of similarly directed streams of magnetic flux in said strips.

Claim 7

In a magnetometer having a head portion and a power means portion connected to said head portion with said head portion having a pair of output leads adapted to carry a direct current signal component responsive to magnetic flux sensed by said head portion and said power means portion having input leads connected to said head output leads and output leads for conducting a direct current signal which is a parameter of said direct current signal component and normally open switch means adapted when closed to operate equipment when it is closed for a predetermined time interval responsive to said direct current signal the improvement comprising a normally closed switch connected to said normally open switch to be opened responsive to closing of said normally open switch, an electron tube having a plate, a cathode and a low current leakage grid for controlling current flow between said plate and cathode, means for connectIng said plate to a source of electrical potential, means for connecting said grid to one of said output leads of said power means portion of said magnetometer through said normally closed switch to conduct said direct current signal to said grid to cause current flow through said tube, a capacitor connected to said grid in parallel with said cathode for maintaining electrical potential on each grid with respect to said cathode for a substantial period of time after said normally closed switch is opened, and means for connecting said cathode to one of said output leads of said head portion of said magnetometer for conducting current from said cathode to said head in opposition to said direct current signal component.

Claim 8

In a magnetometer having a head portion and a power means portion connected to said head portion with said head portion having a pair of output leads adapted to carry a direct current signal component responsive to magnetic flux sensed by said head portion and said power means portion having input leads connected to said head output leads and output leads for conducting a direct current signal which is a parameter of said direct current signal component and normally open switch means adapted when closed to operate equipment when it is closed for a predetermined time interval responsive to said direct current signal the improvement comprising a normally closed switch connected to said normally open switch to be opened responsive to closing of said normally open switch, an electron tube having a plate, a cathode and a low current leakage grid for controlling current flow between said plate and cathode, means for connectIng said plate to a source of electrical potential, means for connecting said grid to one of said output leads of said power means portion of said magnetometer through said normally closed switch to conduct said direct current signal to said grid to cause current flow through said tube, a capacitor connected to said grid in parallel with said cathode for maintaining electrical potential on each grid with respect to said cathode for a substantial period of time after said normally closed switch is opened, and means for connecting said cathode to one of said output leads of said head portion of said magnetometer for conducting current from said cathode to said head in opposition to said direct current signal component.