AC Energy Meter Module: PZEM-004T

Working Principle

The PZEM-004T is an all-in-one AC electrical parameter measurement module that measures voltage, current, power, energy (kWh), frequency, and power factor simultaneously. It uses a current transformer (CT) clamp around the live wire for non-invasive current measurement and a built-in voltage divider for AC voltage sensing. An on-board MCU computes all parameters and outputs them via UART (Modbus-RTU protocol).

Key advantage: The PZEM-004T provides 6 electrical parameters from a single module with no analog signal conditioning required — just serial communication.

Electrical Characteristics

Parameter	Range	Resolution
Voltage	80–260 V AC	0.1 V
Current	0–100 A (with CT)	0.001 A
Active Power	0–23 kW	0.1 W
Energy	0–9999.99 kWh	1 Wh
Frequency	45–65 Hz	0.1 Hz
Power Factor	0.00–1.00	0.01
Interface	UART (9600 baud, Modbus-RTU)	—
Supply	Same mains connection	—

Interfacing with an MCU

Connect the PZEM-004T’s UART TX/RX to the MCU serial port (use SoftwareSerial on Arduino). The CT clamp clips around the live wire — no need to break the circuit. Mains voltage connects directly to the module’s AC terminals.

Calibration

• Factory calibrated: The PZEM-004T ships pre-calibrated; no user calibration needed for typical accuracy (±1%)
• CT ratio: Ensure the CT matches the module version (100A CT for v3.0)
• Energy reset: The kWh counter can be reset via a Modbus command
• Address configuration: Multiple modules can share one bus with unique Modbus addresses (1–247)

Code Example

/*
 * PZEM-004T AC Energy Meter — Arduino
 * Library: PZEM004Tv30 (install via Library Manager)
 * Wiring: TX → Pin 10 (SoftRX), RX → Pin 11 (SoftTX)
 *         AC: L & N to module terminals, CT around live wire
 */
#include <PZEM004Tv30.h>
#include <SoftwareSerial.h>

SoftwareSerial pzemSerial(10, 11);  /* RX, TX */
PZEM004Tv30 pzem(pzemSerial);

void setup() {
    Serial.begin(9600);
    Serial.println("PZEM-004T AC Energy Meter Ready");
}

void loop() {
    float voltage = pzem.voltage();
    float current = pzem.current();
    float power   = pzem.power();
    float energy  = pzem.energy();
    float freq    = pzem.frequency();
    float pf      = pzem.pf();

    if (!isnan(voltage)) {
        Serial.print(voltage, 1); Serial.print("V  ");
        Serial.print(current, 2); Serial.print("A  ");
        Serial.print(power, 1);   Serial.print("W  ");
        Serial.print(energy, 2);  Serial.print("kWh  ");
        Serial.print(freq, 1);    Serial.print("Hz  PF=");
        Serial.println(pf, 2);
    } else {
        Serial.println("Error reading PZEM (check wiring)");
    }
    delay(2000);
}

Real-World Applications

Limitations

• Mains voltage hazard: Direct connection to AC mains requires proper safety measures and enclosure.
• No isolation: UART side is not isolated; use optocouplers for safety.
• Single phase only: Cannot measure 3-phase systems (need 3 units).
• CT accuracy: The included CT limits accuracy at very low currents (<0.5 A).