WATTMETER
A wattmeter is a device that measures the electrical active power of a circuit in watts.
Electromagnetic wattmeters are used to measure utility frequency and audio frequency
power; radio frequency measurements require other types.
TYPES OF WATTMETER
Electrodynamometer wattmeter - for measuring
both DC and AC power.
Induction wattmeter - only for measuring alternating current power.
Working Principle of Electrodynamometer Wattmeter
The electrodynamometer wattmeter operates on the dynamometer principle, which
states that a mechanical force acts between two current carrying conductors or coils.
It consists of a fixed that is divided into two parallel halves and is connected in series
with the load, while the moving is connected across the load via a series multiplier
resistance. The fixed coil is known as the current coil, while the moving coil is known as
the potential coil.
When a wattmeter is used to measure power in a circuit. The load current is carried by
the current coil, and the load voltage is carried by the potential coil. A mechanical force
acts between the coils due to the currents in them. This mechanical force deflects the
moving coil and pointer across the scale. When the deflecting and controlling torques
are equal, the pointer comes to rest. The reversal of the circuit current reverses the
currents in both the current coil and the potential coil, so the deflecting torque direction
A wattmeter is a device that measures the electrical active power of a circuit in watts.
Electromagnetic wattmeters are used to measure utility frequency and audio frequency
power; radio frequency measurements require other types.
TYPES OF WATTMETER
Electrodynamometer wattmeter - for measuring
both DC and AC power.
Induction wattmeter - only for measuring alternating current power.
Working Principle of Electrodynamometer Wattmeter
The electrodynamometer wattmeter operates on the dynamometer principle, which
states that a mechanical force acts between two current carrying conductors or coils.
It consists of a fixed that is divided into two parallel halves and is connected in series
with the load, while the moving is connected across the load via a series multiplier
resistance. The fixed coil is known as the current coil, while the moving coil is known as
the potential coil.
When a wattmeter is used to measure power in a circuit. The load current is carried by
the current coil, and the load voltage is carried by the potential coil. A mechanical force
acts between the coils due to the currents in them. This mechanical force deflects the
moving coil and pointer across the scale. When the deflecting and controlling torques
are equal, the pointer comes to rest. The reversal of the circuit current reverses the
currents in both the current coil and the potential coil, so the deflecting torque direction
