Energy Meter
Metering
Measures real energy (kWh) by multiplying voltage and current over time. Utility revenue meters, DIN-rail submeters, and hobby modules (PZEM style) all do the same maths at different accuracy classes.
What it looks like
Energy Meter
A typical metering — exact shape, colour and markings vary between manufacturers.
Types & variants
Key specs
Accuracy class
Class 1 (±1%) typical for billing; class 0.5S for CT metering.
Basic/max current
Ae.g. 5(30) A — calibrated at 5 A, safe to 30 A.
Meter constant
imp/kWhLED pulses per kWh — handy for verification.
Interface
Pulse output, Modbus RTU, or RF for smart meters.
Markings
Class, current rating, meter constant and wiring diagram on the faceplate.
Standard values
Single-phase 5(30) A and 10(60) A DIN meters; PZEM-004T 100 A module for hobby monitoring.
How to choose
For submetering pick a class 1 DIN meter with pulse or Modbus output for logging; for projects, a PZEM module gives V/A/W/kWh over serial. CT-operated types for >100 A feeders.
Pinout & package
DIN meters: line in / load out terminals per the printed diagram. PZEM: mains sense + CT + isolated TTL serial.
Example circuits
- DIN submeter on an EV-charger circuit
- PZEM-004T + ESP32 home energy dashboard
- Pulse-counting a meter LED with a photodiode
Common failures
Burnt terminals from loose connections at high load, dead displays with the metering still alive, tampered/aged electromechanical discs reading slow.
How to test
Run a known load (e.g. 2 kW heater) and time the impulse LED: pulses/hour ÷ meter constant should equal kW. Big disagreement = wiring error or a failing meter.
Substitutes
Any meter of the same class and current rating; for insight (not billing) a smart-plug power monitor does the job for plug-in loads.