An energy meter is an instrument used to measure electrical energy, also known as an electric meter, fire meter, kilowatt-hour meter, referring to the measurement of various electrical quantities. When using an energy meter, it is important to note that at low voltages (up to 500 volts) and small currents (a few tens of amps), the meter can be directly connected to the circuit for measurement. In the case of high voltages or high currents, the energy meter cannot be directly connected to the line and needs to be used in conjunction with a voltage transformer or current transformer.