Fulfilling requests, this post’s subject is multifunction meter, an instrument that makes many electrical measurements, to help in energy management.
What does the multifunction meter do?
This instrument is installed in electrical panels and measures voltage, current, active and reactive powers, power factor, and frequency. Some more complete models also measure power consumption, phase angle, total harmonic distortions and by order. They will be subject to another post. The multifunction meter is used in energy consumption monitoring and can measure the three phases at once.
How does it work?
Sensors
To measure voltage and electric current, are used potential and current transformers respectively. The current transformer (CT) has a primary winding with few turns and a ferromagnetic core. The measured current produces a magnetic field which is detected by primary winding due to Faraday’s induction law.
With CT, there isn’t the necessity to open the circuit to measure current. Some potential transformers work like the well-known transformers, they have been explained in the post whose link is below.
However, exist constructive features and many types of measurement transformers that will be to another post. Sensors are coupled in bars to transmit the measures for data manager.
Data manager
Collects sensors’ information through RS-485 interface, converts quantities in digital signals through analog-digital converters and sends them to LEDs or LCD displays. The calculations to get other quantities are made by microprocessors.
Some data managers can read until 96 sensors, with 96 single-phase circuit breakers, 48 biphasic, or 32 three-phase.
Communication
Multifunction meters can transmit information about the circuit remotely and communicate with other devices. It’s possible due to electric standard RS-485 and communication protocols like MODBUS-RTU. In addition to transmitting information to servers on the cloud.
Other information
The multimeter is portable while the multifunction meter is fixed. Multimeters can only measure basic quantities: voltage, current, resistance and capacitance. Monitoring electric quantities, multifunction meters help in the energy economy because the measures help in management and decision making to reduce consumption.
I was asked what happens if a multifunction meter for 50 Hz is used at 60 Hz and vice versa. It’s unlikely that some problem will happen because there isn’t a critical component that operates in only one frequency. Almost all multifunction meters operate in both frequencies.
