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WattmeterHome Electrical Safety Electrical Theory Electrician Practice Exams 2005 NEC Search Term Index
WATTMETERSWattmeters are used to determine DC power or real AC power delivered to the load.Here is a great article about wattmeters. SOURCEWattmeter designPower in an electric circuit is the product (multiplication) of voltage and current, so any meter designed to measure power must account for both of these variables.A special meter movement designed especially for power measurement is called the dynamometer movement, and is similar to a D'Arsonval or Weston movement in that a lightweight coil of wire is attached to the pointer mechanism. However, unlike the D'Arsonval or Weston movement, another (stationary) coil is used instead of a permanent magnet to provide the magnetic field for the moving coil to react against. The moving coil is generally energized by the voltage in the circuit, while the stationary coil is generally energized by the current in the circuit. A dynamometer movement connected in a circuit looks something like this: |
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REVIEW:
| Wattmeters are often designed around dynamometer meter movements, which employ both voltage and current coils to move a needle. |
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