Avometer Model 7 Mk2 Alnico Magnet

In approximately 1948, at the time of introduction of the AVO Model 7 Mk2, the Alnico alloy produced the most powerful type of magnet. It was a mixture of aluminium, nickel, and cobalt.

A sensitive meter movement is highly desirable, which is when a small current in the magnitude of microamperes is capable of producing a full-scale deflection of the needle. To achieve this level of sensitivity it is important to have powerful magnets that produce a high density of magnetic field lines. In addition, the design is such that the magnetic field focuses within a narrow gap inside which the coil moves.

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