MAGNETIC FIELD MEASUREMENT SYSTEMS AND METHODS OF MAKING AND USING
A magnetic field measurement system includes an array of magnetometers; at least one magnetic field generator with each of the at least one magnetic field generator configured to generate a first magnetic field at one or more of the magnetometers, wherein the generated first magnetic field combines with the ambient magnetic field to produce a directional magnetic field at the one or more of the magnetometers, where a magnitude and direction of the directional magnetic field is selectable using the at least one magnetic field generator; and a controller coupled to the magnetometers and the at least one magnetic field generator, the controller including a processor configured for receiving signals from the magnetometers, observing or measuring a magnetic field from the received signals, and controlling the at least one magnetic field generator to generate the first magnetic field and select the direction of the directional magnetic field.
1 . A magnetic field measurement system, comprising:
an array of magnetometers, wherein the magnetometers i) are unshielded or ii) comprise shielding so that an ambient magnetic field at the magnetometers is reduced no more than 90% by the shielding;
at least one magnetic field generator with each of the at least one magnetic field generator configured to generate a first magnetic field at one or more of the magnetometers, wherein the generated first magnetic field combines with the ambient magnetic field to produce a directional magnetic field at the one or more of the magnetometers, wherein a direction of the directional magnetic field is selectable using the at least one magnetic field generator; and
a controller coupled to the magnetometers and the at least one magnetic field generator, the controller comprising a processor configured for receiving signals from the magnetometers, observing or measuring a magnetic field from the received signals, and controlling the at least one magnetic field generator to generate the first magnetic field and select the direction of the directional magnetic field.
2 . The magnetic field measurement system of claim 1 , wherein the at least one magnetic field generator is a single magnetic field generator configured to generate the first magnetic field at each of the magnetometers.
3 . The magnetic field measurement system of claim 1 , wherein the at least one magnetic field generator comprises a plurality of magnetic field generators.
4 . The magnetic field measurement system of claim 1 , wherein the at least one magnetic field generator comprises a plurality of magnetic field generators with each magnetic field generator, disposed around, and generating the first magnetic field for, a different one of the magnetometers.
5 . The magnetic field measurement system of claim 1 , wherein each of one or more pairs of the magnetometers are arranged as a gradiometer.
6 . The magnetic field measurement system of claim 5 , wherein the at least one magnetic field generator comprises a plurality of magnetic field generators with each magnetic field generator, disposed around, and generating the first magnetic field for, a different one of the magnetometers or gradiometers.
7 . The magnetic field measurement system of claim 1 , further comprising at least one magnetic field sensor configured for observing the ambient magnetic field, wherein the processor of the controller is coupled to the at least one magnetic field sensor and configured to alter the first magnetic field generated by the at least one magnetic field generator in response to a change in the measured ambient magnetic field.
8 . The magnetic field measurement system of claim 1 , further comprising at least one position or orientation sensor associated with the magnetometers for sensing changes in position or orientation of the magnetometers, wherein the processor of the controller is coupled to the at least one position or orientation sensor and to alter the first magnetic field generated by the at least one magnetic field generator in response to a change in the position or orientation of the magnetometers.
9 . A method of measuring or observing a signal source using the magnetic field measurement system of claim 1 , the method comprising:
positioning the array of magnetometers in relation to the signal source;
generating, using the at least one magnetic field generator, the first magnetic field at the magnetometers; and
observing or measuring a magnetic field produced by the signal source using the magnetometers.
10 . The method of claim 9 , further comprising obtaining an estimate of a direction of the magnetic field produced by the signal source and selecting the first magnetic field to produce the directional magnetic field at the magnetometers in a direction that is within 20 degrees of parallel or antiparallel to the direction of the magnetic field produced by the signal source.
11 . The method of claim 9 , wherein the magnetic field measurement system comprises a sensor selected from a magnetic field sensor, a position sensor, or an orientation sensor, the method further comprising adjusting the first magnetic field is response to the sensor.
12 . A method of targeted observation or measurement of a source of electromagnetic signals, the method comprising:
obtaining an estimate of a direction of a source magnetic field generated by a signal source, wherein the signal source is disposed at a site;
positioning an array of magnetometers in relation to the site of the signal source;
generating a directional magnetic field in a direction that is within 20 degrees of parallel or antiparallel to the direction of the source magnetic field at each of a plurality of the magnetometers in the array; and
analyzing signals generated at the plurality of the magnetometers to observe or measure the source magnetic field generated by the signal source.
13 . The method of claim 12 , wherein the plurality of magnetometers comprises at least one pair of the magnetometers arranged as a gradiometer.
14 . The method of claim 12 , wherein generating the directional field comprises using at least one magnetic field generator to generate at least one first magnetic field, wherein the at least one first magnetic field combines with an ambient magnetic field to produce the directional magnetic field at each of the magnetometers, wherein a direction of the directional magnetic field is selectable using the at least one magnetic field generator.
15 . The method of claim 14 , further comprising receiving signals from a magnetic field sensor observing the ambient magnetic field and adjusting the at least one first magnetic field in response to the signals from the magnetic field sensor.
16 . The method of claim 12 , further comprising receiving signals from a position or orientation sensor observing a position or orientation of the magnetometers and adjusting the at least one first magnetic field in response to the signals from the position or orientation sensor.
17 . A magnetic field measurement system, comprising:
an array of magnetometers; and
a controller coupled to the magnetometers, the controller comprising a processor configured to:
obtain an estimate of a direction of a source magnetic field generated by a signal source, wherein the signal source is disposed at a site;
generate a directional magnetic field in a direction that is within 20 degrees of parallel or antiparallel to the direction of the source magnetic field at each of a plurality of the magnetometers arranged in the array and positioned in relation to the site of the signal source; and
analyze signals generated at each of the magnetometers to observe or measure the source magnetic field generated by the signal source.
18 . The magnetic field measurement system of claim 17 , further comprising at least one magnetic field generator coupled to the controller, wherein the processor is further configured to, for each of the at least one magnetic field generator, generate a first magnetic field at one or more of the magnetometers, wherein the first magnetic field combines with an ambient magnetic field to produce the directional magnetic field at the one or more of the magnetometers, wherein the direction of the directional magnetic field is selectable using the at least one magnetic field generator.
19 . The magnetic field measurement system of claim 18 , further comprising a sensor selected from a magnetic field sensor, a position sensor, or an orientation sensor, wherein the processor is further configured to adjust the first magnetic field in response to the sensor.
20 . The magnetic field measurement system of claim 17 , wherein the magnetometers i) are unshielded or ii) comprise shielding so that an ambient magnetic field at the magnetometers is reduced no more than 90% by the shielding.