Volt meter analog12/14/2023 Permanent Magnet Moving Coil Voltmeter – PMMC.The different types of voltmeters are determined by the construction principle and measurement types, which are: The deflection of the coil is thus proportional to the current, which in turn is proportional to the applied voltage, which is indicated by a pointer on a scale. The coil rotates, compressing a spring that opposes the rotation. The torque is proportional to the current through the coil. 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 rotate. The galvanometer has a coil of fine wire suspended in a strong magnetic field. A moving coil galvanometer can be used as a voltmeter by inserting a resistor in series with the instrument. Its operation is based on Ohm’s law idea: “Voltage across a resistance is directly proportional to the current traveling through it,”.įor example, the D’Arsonval meter or galvanometer works by deflecting a pointer in response to an electric current flowing through a coil in a constant magnetic field. The current sensed by the ammeter is then converted to reading in volts. An analog voltmeter usually contains a built-in, high-value fixed resistance, and an ammeter measuring the current passing through it. So that voltmeter is equivalent to pressure difference measurement.Ī common analog voltmeter, for example, is likely to use an electromechanical mechanism that converts current flowing through the wire into a voltage reading. This model assumes that the water is flowing horizontally so that the force of gravity can be ignored. Voltage is like the pressure difference that pushes water through the hose. Ohm’s Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems.Įlectricity (as well as heat) was originally understood to be a kind of fluid, and the names of certain electric quantities (such as current) are derived from hydraulic equivalents. The relationship between voltage and current is defined (in ohmic devices like resistors) by Ohm’s law. Since electric current is invisible and the processes in play in electronics are often difficult to demonstrate, the various electronic components are represented by hydraulic equivalents. it can also be applied to heat transfer problems. The hydraulic analogy, or the electric-fluid analogy, is a widely used analogy between hydraulics and electricity, which is a useful tool for teaching and for those who are struggling to understand how circuits work. In circuit diagrams, a voltmeter is represented by the letter V in a circle, with two emerging lines representing the two points of measurement. Specially calibrated test instruments have higher accuracies. Digital meters can be made with high accuracy, typically better than 1%. Voltmeters that can measure a potential difference of 1 μV are common, and sensitivities down to 10 -12 can be attained. Real voltmeters always have finite resistance, but a voltmeter should have large enough resistance that connecting it to a circuit does not change the other currents appreciably. Their functionality is usually built into modern multimeters.Īn ideal voltmeter would have infinite resistance, so connecting it between two points in a circuit would not alter any of the currents. by the battery), and others powered by the measured voltage source itself. They are made in a wide range of styles, some separately powered (e.g. To find the potential difference between any two points in the circuit, the voltmeter terminals are connected between those points without breaking or cutting the wire. Voltmeters are instruments used for measuring the electric potential difference between two points in an electric circuit.
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