How Does a Wattmeter Work?
A wattmeter does a complex job, measuring the power flowing through an electrical circuit. It simultaneously measures the voltage and current values and multiplies them to give power in watts. The three main types are electrodynamic, electronic and digital. Electrodynamic Electrodynamic wattmeters are a design that goes back to the early 20th century. They work by using three coils: two fixed in series with the electrical load, and a moving coil in parallel with it. The series coils measure current flowing through the circuit, the parallel coil measures voltage. A series resistor limits the current through the moving coil. It’s situated between the two fixed coils and is attached to an indicator needle. The magnetic fields in all three coils influence the needle movement. A spring returns the needle to zero when no voltage or current is present. This design is simple, reliable and rugged, though the coils can overheat. Electronic People using radio and microwave equipment need to measu
