An electricity meter or energy meter is a device that measures the amount of electric energy transferred.
In the simplest case, the electrical power is calculated by multiplying the voltage with the current. Energy is calculated by monitoring power over time.
In an AC circuit the situation is a bit more complex, as the voltage and current alternates and may be out of phase depending on the load. This is why a dedicated meter is required that continuously monitors both voltage and current and calculates the power hundreds or thousands times per second.
To accurately monitor power and energy, both current and voltage has to be monitored at the same time.
The simplest form of energy meter has a pulse output. Each pulse will mean a certain amount of energy has flowed through the meter. For example, the meter may be marked “500 p/kWh”, which simply means that when we count 500 pulses, that’s 1kWh. So each pulse is 1kWh/500 = 2Wh. Common types of pulse outputs are “S0” and “KYZ”. These types of outputs can be directly connected to the ezeio input terminals. Up to four (4) pulse meters can be connected to the ezeio.
Some meters have a digital output. The ezeio supports Modbus directly, and through the Modbus communication the meter can communicate more information than the pulse output can convey. A Modbus meter may provide information about both power and energy for each phase, voltage, current, power factor and many other parameters. The ezeio supports up to 20 Modbus meters at the same time.
For small installations, an in-line meter with built-in sensors can be used. Typically in-line meters are rated for loads smaller than 100A. For larger loads, external Current Transformers are typically required.