How does a digital wattmeter work

Here, an electronic circuit measures the current and voltage, multiplies the two in another circuit, and delivers the result as a proportional current or voltage to a standard meter movement. Digital wattmeters measure current and voltage electronically thousands of times a second, multiplying the results in a computer chip to determine watts. The computer can also perform statistics such as peak, average, low watts and kilowatt-hours consumed.

They can monitor the power line for voltage surges and outages. In , a variety of inexpensive digital wattmeters are available to consumers. With the falling price and improved capabilities of digital electronics, they have become popular for conveniently measuring power consumption in household appliances with an eye toward saving energy and money.

Chicago native John Papiewski has a physics degree and has been writing since He has contributed to "Foresight Update," a nanotechnology newsletter from the Foresight Institute. How Does a Wattmeter Work? How it Works: Voltage Relay. Types of Electrical Loads. As shown in the above figure, the wattmeter has two sets of coils.

One coil is fixed and is made in two identical parts. It is made upon heavy gauge copper wire. So it has low resistance. This is named as current coil. The other coil which is known as voltage coil, is wound from fine gauge wire.

So it has relatively high resistance. The voltage coil is mounted on a circular manner. It is placed between the two parts of the current coil. The manner of connecting the wattmeter into a circuit is given in the 2 nd figure.

As shown, The current coil is connected in series with the load so that the circuit current flows through it. Similar to the voltmeter circuit, the voltage coil is connected in parallel with the load. Both voltage and current coils will produce magnetic fields. These fields interact to each other and produce a deflecting torque on the voltage coil. The interacting fields are proportional to the circuit voltage V and current I respectively.

So the produced deflecting torque is proportional to the product of circuit voltage and current. Restoring torque is provided by contrawound spiral springs, as in the moving coil meter.

The voltage coil may be connected either on the supply side or the load side of the current coil. Due to the currents in the coils, a mechanical force acts between them. The result of this mechanical force deflects the moving coil and the pointer over the scale. The pointer comes to the rest when the deflecting torque and controlling torque become equal. As the reversal of the circuit current reverses the currents in both the current coil and potential coil so that the direction of deflecting torque remains unchanged.

Therefore, electrodynamometer wattmeter can measure power in both the AC as well DC circuits. The working of induction type wattmeter is based on the principle of electromagnetic induction. The induction wattmeter consists of two laminated electromagnets viz. Shunt Magnet and Series Magnet. The shunt magnet is connected across the supply and carries a current proportional to the supply voltage.