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It typically consists of an arrangement of a mobile permanent magnet and fixed coil, arranged so that currents in the coil generate a pair of equal and opposite forces between the coil and magnet. A voice coil actuator, also called a voice coil motor (VCM), is an electromagnetic linear actuator where the magnet is fixed and the coil is mobile ...
A moving coil meter has a different and equally distinctive structure. A horseshoe magnet with a keeper in use. A magnet keeper is a specialised pole piece used to temporarily connect the poles of a permanent magnet, to help to preserve the magnetism, and for safety in the case of large and powerful magnets.
Moving magnet ammeters operate on essentially the same principle as moving coil, except that the coil is mounted in the meter case, and a permanent magnet moves the needle. Moving magnet Ammeters are able to carry larger currents than moving coil instruments, often several tens of amperes, because the coil can be made of thicker wire and the ...
The meter movement in a moving pointer analog multimeter is practically always a moving-coil galvanometer of the d'Arsonval type, using either jeweled pivots or taut bands to support the moving coil. In a basic analog multimeter the current to deflect the coil and pointer is drawn from the circuit being measured; it is usually an advantage to ...
Close-up view (rear) of a permanent magnet type moving coil meter. When a direct current (DC) flows through the coil, the coil generates a magnetic field. This field acts against the permanent magnet. The coil twists, pushing against the spring, and moves the pointer. The hand points at a scale indicating the electric current.
Diagram of moving coil cartridge, showing essential parts. The MC design is again a tiny electromagnetic generator, but (unlike an MM design) with the magnet and coils reversed: the coils are attached to the cantilever, and move within the field of a permanent magnet. The coils are tiny and made from very fine wire.
These fields interact with the magnetic field of a large permanent magnet, resulting in an indication of temperature. [1] A Ratiometer type temperature indicating system consists of a sensing element and a moving-coil indicator, which unlike the conventional type has two coils moving together in a permanent-magnet field of non-uniform strength ...
An example is a nickel rod that tends to deform when it is placed in an external magnetic field. Another example is wrapping a series of electromagnetic induction coils around a metal tube in which a Terfenol-D material is placed. The coils generate a moving magnetic field that courses wavelike down the successive windings along the stator tube.