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The moving iron ammeter symbol is in the lower-left corner of the meter face. Moving iron ammeters use a piece of iron which moves when acted upon by the electromagnetic force of a fixed coil of wire. The moving-iron meter was invented by Austrian engineer Friedrich Drexler in 1884. [5]
Normally the moving coil is suspended from a pivot above it, so the linear motion along the core causes the coil, and an attached pointer, to rotate over a dial. [ 5 ] The Weston frequency meter also uses tuned circuits, but in this case it is the relative inductance between two such circuits that creates the meter's movements.
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 ...
An early D'Arsonval galvanometer showing magnet and rotating coil. A galvanometer is an electromechanical measuring instrument for electric current.Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely.
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 ...
A moving coil galvanometer can be used as a voltmeter by inserting a resistor in series with the instrument. The galvanometer has a coil of fine wire suspended in a strong magnetic field. When an electric current is applied, the interaction of the magnetic field of the coil and of the stationary magnet creates a torque, tending to make the coil ...
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General purpose instrument measures voltage, current and resistance (and sometimes other quantities as well) Network analyzer: Measures network parameters Ohmmeter: Measures the resistance of a component Oscilloscope: Displays waveform of a signal, allows measurement of frequency, timing, peak excursion, offset, ... Psophometer