# Types Of Electric Meter

In modern days, the types of electric meter continuously operate to measure the instantaneous voltage and current and calculating the product of these to give out the instantaneous electrical power. The electric power is then integrated against time to give energy used. There are basically two kinds of electric meter categories, the electromechanical and solid state meters.

Electromechanical Technology: The most common electric meter type is the Thomson electric meter which falls under the electromechanical category. This was invented by Elihu Thomson in 1888. The working pf this electromechanical induction electric meter is very simple to understand. These kinds of electric meter are operated by counting the number of revolutions of an aluminum disc which keeps on rotating at a speed proportional to the power supplied. The number of revolutions is thus proportional to the energy usage. It consumes a small amount of power, typically around two watts. There is a disc made up of a metal which is acted upon by two coils. The one of the two coils is attached in a way that it produces a magnetic flux proportional to the voltage and the other produces a magnetic flux in proportion to the current. The field of the voltage coil is delayed by ninety degrees using a lag coil. The eddy currents are produced in the disc and the effect is such that a force is exerted on the disc in proportion to the product of the instantaneous current and voltage. A permanent magnet exerts an opposing force proportional to the speed of rotation of the disc. The equilibrium between these two opposing forces results in the disc rotating at a speed proportional to the power being used.

Solid state meters: The types of electric meter in modern times has changed and now we have solid state electric meters which display the power used on an LCD screen whereas there are some latest electrical meters which can be made to read automatically. Apart from the amount of electricity used, the solid state electric meter type can also record other parameters of the load and supply such as maximum demand, power factor and reactive power used etc. some of the advanced kinds of electric meters also include electronic clock mechanisms to compute a value, rather than an amount of electricity consumed, with the pricing varying by the time of day, day of week, and seasonally. The technology used in most of the solid state electric meter type is the use of a current transformer to measure the current. The main current-carrying conductors need to pass through the meter itself and so the meter can be located remotely from the main current-carrying conductors, which is a particular advantage in large-power installations. It is also possible to use remote current transformers with electromechanical meters though this is less common.

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