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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 ...
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.
A resistance wire is laid along the length of a metre rule and contact with the wire is made through a galvanometer by a slider. When the galvanometer reads zero, the ratio between the lengths of wire to the left and right of the slider is equal to the ratio between the values of a known and an unknown resistor in a parallel circuit. [5]
A bridge circuit is a topology of electrical circuitry in which two circuit branches (usually in parallel with each other) are "bridged" by a third branch connected between the first two branches at some intermediate point along them. The bridge was originally developed for laboratory measurement purposes and one of the intermediate bridging ...
Ideally the measuring device should not affect the circuit parameters i.e., the internal impedance of the ammeter should be zero (no voltage drop over the ammeter) and the internal impedance of the voltmeter should be infinite (no current through the voltmeter). However, in actual case, ammeters have a low but non zero impedance and voltmeters ...
In this case, a separate shunt, a resistor of very low but accurately known resistance, is placed in parallel with a voltmeter, so that virtually all of the current to be measured will flow through the shunt (provided that the very high internal resistance of the voltmeter takes such a low portion of the current that it can be considered ...
Thermistors principle: relation between temperature and electrical resistance of ceramics or polymers, range: from about 0.01 to 2,000 kelvins (−273.14 to 1,700 °C) Thermocouples principle: relation between temperature and voltage of metal junctions (Seebeck effect), range: from about −200 °C to +1350 °C; Thermometer
A "Universal" version having additional alternating current and alternating voltage ranges was offered from 1933 and in 1936 the dual-sensitivity Avometer Model 7 offered 500 and 100 Ω/V. [12] Between the mid-1930s until the 1950s, 1,000 Ω/V became a de facto standard of sensitivity for radio work and this figure was often quoted on service ...