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Difference between Wattmeter and Energy Meter
In every electrical system, we need to measure various electrical quantities such as current, voltage, power, energy, etc. For this purpose various types of measuring instruments have been developed to measure the respective quantity.
Go through this article to find out more about wattmeter and energy meter. We also learn about the significant differences between a wattmeter and energy meter. One major difference between wattmeter and energy meter is that the wattmeter measures electrical power in the circuit, whereas the energy meter measures total amount of energy consumed by the load.
What is a Wattmeter?
A wattmeter is an electrical measuring device used for measuring the active power in an electric circuit. The wattmeter is a type of indicating instrument that means it measure the electrical power in the circuit, only when the current flowing in the circuit.
A typical wattmeter consists of two coils namely current coil and pressure coil. The current coil of the wattmeter is connected in series with the electrical load, while the pressure coil is connected in parallel with the load. Therefore, the load current flows through the current coil and the load voltage appears across the pressure coil. The load current through the current coil produces a magnetic field which is directly proportional to the current through the coil. This magnetic field can produce a torque in the pressure coil. A pointer is attached to the pressure coil can move over a scale to the show the power reading.
What is an Energy Meter?
A type of electrical measuring instrument which measures the total amount of energy consumed by an electrical load over a certain period of time is known as energy meter. The energy meter is a type of integrating instrument as it maintains the record of measurement over a period. In practice, the energy meters are generally calibrated to measure the electrical energy in kWh (kilo Watt hours).
An electromechanical induction type energy meter consists of a disc made of aluminium mounted on a spindle and is placed between two electromagnets. The speed of rotation of the disc is directly proportional to the power consumed and this power is integrated over a certain period of time by using a counter and gear train mechanism.
Difference between Wattmeter and Energy Meter
The following table highlights all the major differences between a wattmeter and an energy meter −
| Basis of Difference | Wattmeter | Energy Meter |
|---|---|---|
| Definition | An electric measuring device which shows reading of the power consumed by a load in the circuit is called wattmeter. | An electrical measuring device that shows the value of electrical energy consumed by a load in a certain period is called energy meter. |
| Circuit symbol |
|
|
| Quantity measured | A wattmeter measures active (or real) power in an electric circuit. | Energy meters measures the total average power consumed over a period, called energy. |
| Types | There are two types of wattmeter namely ‘electrodynamometer type wattmeter’ and ‘induction type wattmeter’. | Types of energy meters are: ‘electromechanical induction type energy meter’, ‘electronic energy meter’ and ‘smart energy meter’. |
| Measuring unit | A typical wattmeter shows the reading of electrical power in watts. | A typical energy meter shows the energy reading in kWh (kilo Watt hours). |
| Major parts | The major parts of a wattmeter are: current coil, pressure coil, damping system, control mechanism, scale and pointer. | The major parts of an energy meter are: current coil, voltage coil, rotating aluminium disc, breaking system, counting mechanism. |
| Instrument type | A wattmeter is an indicating type instrument. | An energy meter is an integrating type instrument. |
| Applications | Wattmeter is used with electrical devices to measure their power ratings and consumption, and also used in labs to perform experiments. | Energy meters are extensively to measure electrical energy consumed for billing and monitoring purposes. |
Conclusion
The most important difference that you should keep in mind here is that a Wattmeter is a type of indicating instrument, while an Energy Meter is a type of integrating instrument.
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