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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.
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. The coil arrangements and the methods of obtaining the non-uniform field depends on the manufacturer's design.
(Later versions of the instrument, with transistorised circuitry, used a moving-coil meter as the display for the null detector.) Taps at 1, 10, 100 and 1000 turns are shown on the T1 secondary and on T2 primary P2a. Four-way selector switches are shown, but the tap selections are actually combined on a single switch to give seven measuring ranges.
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 ...
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 ...
Top-left: Duddell moving-coil oscillograph with mirror in oil bath. Top-middle: Rotating shutter and moving mirror assembly used with Duddell oscillograph, for placing time-index marks next to the waveform pattern. Top-right: Moving-film camera for recording the waveform.
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Eddy currents are formed when a moving or changing magnetic field intersects a conductor or vice versa. Diagram of a coil inducing an eddy current in a conductive plate The relative motion causes a circulating flow of electrons, or currents, within the conductor.