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Whenever I've encountered measuring magnetic fields with magnetometers, they've typically been very large magnetic fields (up to a few T). Magnetic fields fall off rapidly with distance and so I generally figured that measuring weak fields at distances on the order of cm (let alone m) was very difficult.
But archeologists seem to use magnetic Gradiometers to find magnetic material buried in the Earth. What I want to know is how do gradiometers acquire this signal gain from multiple magnetometers.
Just as an example, here:
https://www.sparkfun.com/products/12670
is a cheap magnetometer with a sensitivity of ~0.1 muT. With a bit more digging (and a much larger budget), there are magnetometers which can reach the order of a few nT sensitivity. But for weak magnetic fields 10s of centimetres away, this still may not be sensitive enough.
So I'm assuming the gradiometer is comprised of two or more magnetometers, and the difference in field is calculated. But what is the statistics which governs this signal gain? Are there any sources I could read on this sort of measurement? How do variables such as separation distance affect the sensitivity. What if more magnetometers are used? What about an array of magnetometers (or even, a matrix)?
Hopefully I've explained my question okay. Apologies since this isn't strictly a Condensed Matter question.
Thank you
But archeologists seem to use magnetic Gradiometers to find magnetic material buried in the Earth. What I want to know is how do gradiometers acquire this signal gain from multiple magnetometers.
Just as an example, here:
https://www.sparkfun.com/products/12670
is a cheap magnetometer with a sensitivity of ~0.1 muT. With a bit more digging (and a much larger budget), there are magnetometers which can reach the order of a few nT sensitivity. But for weak magnetic fields 10s of centimetres away, this still may not be sensitive enough.
So I'm assuming the gradiometer is comprised of two or more magnetometers, and the difference in field is calculated. But what is the statistics which governs this signal gain? Are there any sources I could read on this sort of measurement? How do variables such as separation distance affect the sensitivity. What if more magnetometers are used? What about an array of magnetometers (or even, a matrix)?
Hopefully I've explained my question okay. Apologies since this isn't strictly a Condensed Matter question.
Thank you