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The galvanometer is oriented so that the plane of the coil is vertical and aligned along parallel to the horizontal component B H of the Earth's magnetic field (i.e. parallel to the local "magnetic meridian"). When an electric current flows through the galvanometer coil, a second magnetic field B is created. At the center of the coil, where the ...
Diagram of D'Arsonval/Weston type galvanometer. As the current flows from + terminal of the coil to − terminal, a magnetic field is generated in the coil.This field is counteracted by the permanent magnet and forces the coil to twist, moving the pointer, in relation to the field's strength caused by the flow of current.
This moving coil galvanometer is mainly used to measure very feeble or low currents of order 10 −9 A. To linearise the magnetic field across the coil throughout the galvanometer's range of movement, the d'Arsonval design of a soft iron cylinder is placed inside the coil without touching it. This gives a consistent radial field, rather than a ...
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A vibration galvanometer is a type of mirror galvanometer, usually with a coil suspended in the gap of a magnet or with a permanent magnet suspended in the field of an electromagnet. The natural oscillation frequency of the moving parts is carefully tuned to a specific frequency; commonly 50 or 60 Hz. Higher frequencies up to 1 kHz are possible.
A ballistic galvanometer is a type of sensitive galvanometer; commonly a mirror galvanometer. Unlike a current-measuring galvanometer, the moving part has a large moment of inertia, thus giving it a long oscillation period. It is really an integrator measuring the quantity of charge discharged through it. It can be either of the moving coil or ...
A coil of wire attached to the pointer twists in a magnetic field against the resistance of a torsion spring. Hooke's law ensures that the angle of the pointer is proportional to the current. A DMD or digital micromirror device chip is at the heart of many video projectors. It uses hundreds of thousands of tiny mirrors on tiny torsion springs ...
The thermo-galvanometer designed by Mr W. Duddell can be used for the measurement of extremely small currents to a high degree of accuracy. It has practically no self-induction or capacity and can therefore be used on a circuit of any frequency (even up to 120,000~ per sec.) and currents as small as twenty micro-amperes can be readily measured ...