A gaussmeter is also called as a magnetometer. A
magnetometer is a scientific instrument used to measure the strength and/or
direction of the magnetic field in the vicinity of the instrument.
A direct current flowing in an inductor creates a strong
magnetic field around a hydrogen-rich fluid, causing the protons to align
themselves with that field. The current is then interrupted, and as protons are
realigned with Earth's magnetic field they precess at a specific frequency.
This produces a weak alternating magnetic field that is picked up by a
(sometimes separate) inductor. The relationship between the frequency of the
induced current and the strength of Earth's magnetic field is called the proton
gyromagnetic ratio, and is equal to 0.042576 hertz per nanotesla (Hz/nT).
Inductive Pickup
Coils
Inductive pickup coils measure the magnetization by
detecting the current induced in a coil due to the changing magnetic moment of
the sample. The sample’s magnetization can be changed by applying a small ac
magnetic field (or a rapidly changing dc field), as occurs in capacitor-driven
pulsed magnets. These measurements require differentiating between the magnetic
field produced by the sample and that from the external applied field. Often a
special arrangement of cancellation coils is used. For example, half of the
pickup coil is wound in one direction, and the other half in the other
direction, and the sample is placed in only one half. The external uniform
magnetic field will be detected by both halves of the coil and since they are
counterwound the external magnetic field produces no net signal.
In 1833, Carl Friedrich Gauss , head of the Geomagnetic
Observatory in Göttingen, published a paper on measurement of the Earth's
magnetic field. It described a new instrument
that consisted of a permanent bar magnet suspended horizontally from a gold
fibre. The difference in the oscillations when the bar was magnetised and when
it was demagnetised allowed Gauss to calculate an absolute value for the
strength of the Earth's magnetic field.