Gradiometer

Scientist making a magnetic survey with an axial gradiometer.

A gradiometer measures the gradient (numerical rate of change) of a physical quantity, such as a magnetic field or gravity.[1]

Types of gradiometer

There are at least two types of gradiometer to measure magnetic fields:

  1. Axial gradiometer. Such a device consists of two magnetometers placed in series (i.e. one above the other). The result coming from the device is the difference in magnetic flux at that point in space (a.k.a. first spatial derivative).
  2. Planar gradiometer. Such a device consists of two magnetometers placed next to each other. The result coming from the device is the difference in flux between the two loops.

Each sensor type responds differently to certain spatial signals. This source says that axial gradiometers are good for measuring depth and planar ones can measure the signal even from a small exposure, ie they can measure signals that occupy small spaces.https://books.google.nl/books?id=tndqYGPHQdEC&pg=PA1168&lpg=PA1168&dq=axial+planar+gradiometer&source=bl&ots=GNal-394sz&sig=SdFE_RVkypvAZ7WvOX67coygqB8&hl=en&sa=X&ved=0ahUKEwinoY2I0LPKAhXCVxQKHavzAikQ6AEISTAI#v=onepage&q=axial%20planar%20gradiometer&f=false

The planar signal peaks exactly over the source and the axial peaks on one side of the source but bottoms at the other.

See also

References

  1. ↑ http://www.merriam-webster.com/dictionary/gradiometer



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