Magnetometer having coil formed by two spiral shaped conductors

DETAILED DESCRIPTION A simple design for a fluxgate magnetometer is shown in FIGS.
1A and 1B.
A thin layer of magnetic material 1 is sandwiched between two substrates 2 and 3.
Two drive coils 4A and 4B are formed on the substrates 2 and 3 respectively.
The coils 4A and 4B are formed on the substrates 2 and 3 by screen printing with an ink containing metallic particles and then firing to form a metallic track defining the coil, but other methods such as photo-lithographic etching could be used.
Each drive coil 4A and 4B consists of a spiral track of conductive material laid down on one substrate.
The two drive coils 4A and 4B are connected by a conductive link 5.
The two drive coils 4A and 4B are connected in opposition by the conductive link 5 so that current will be contrarotating in the two drive coils 4A and 4B.
The two drive coils 4A and 4B are supplied with alternating current by an A.
C.
source 6.
Two reading coils 7A and 7B are also formed on the substrates 2 and 3 respectively.
Each reading coil 7A and 7B consists of a spiral conductive track of conductive material laid down on one substrate.
The two reading coils 7A and 7B are connected in opposition by a conductive link 8.
The reading coils 7A and 7B are connected to a bandpass filter 9 and the output of this filter is supplied to a processor 10.
The processor 10 controls a display 11.
In operation, the A.
C.
source 6 produces contrarotating alternating currents in the drive coils 4A and 4B.
These currents produce an oscillating magnetic field which drives the magnetic material 1 into saturation.
The changing magnetic flux in the magnetic material 1 will produce an output voltage in the reading coils 7A and 7B.
This output voltage will include alternating components at the drive frequency, at odd harmonics of the drive frequency due to the non-linearity of the magnetic material and at even harmonics of the drive frequency due to the effects of external magnetic fields acting on the magnetic material 1.
The amplitudes of the components of the output voltage at even harmonics of the drive frequency will be proportional to the strength of any components of external magnetic fields in the direction X