The ZMPT101B is a high-precision active voltage transformer module designed for safe and accurate AC voltage monitoring. It utilizes a micro-precision voltage transformer to isolate high-voltage AC mains (up to 250V) and converts it into a low-voltage analog signal that can be safely read by a microcontroller's ADC. Unlike passive dividers, this module features an onboard operational amplifier for signal conditioning, compensation, and amplitude adjustment.

Specifications

• Input Voltage Range: 0V – 250V AC
• Supply Voltage (VCC): 5V – 30V DC
• Output Signal: Analog Sine Wave (Centred at VCC/2)
• Operating Current: 2mA (Transformer nominal)
• Isolation Voltage: 4000V (High-voltage safety)
• Operating Temperature: -40°C to +70°C

Operating Principle

• Galvanic Isolation: The ZMPT101B transformer provides physical separation between the dangerous 230V AC line and your low-voltage DC electronics.
• Active Signal Conditioning: The onboard Op-Amp circuit shifts and amplifies the signal. Because microcontrollers cannot measure the negative cycle of an AC sine wave, the module offsets the waveform so the entire wave sits between 0V and VCC (typically centred at 2.5V for a 5V supply).
• Amplitude Adjustment: The multi-turn potentiometer allows you to scale the output waveform's peak-to-peak voltage to match your microcontroller's resolution.

Features

• High Precision Output: Equipped with a high-precision voltage transformer and a professional-grade op-amp for exact sampling and linear output.
• Adjustable Waveform: The output amplitude can be tuned using the potentiometer. If the waveform clips or distorts, increasing the supply voltage (VCC) provides more headroom.
• Safe AC Acquisition: Ideally suited for mains power signal acquisition without the risk of direct electrical contact with the high-voltage side.
• Median Voltage Control: The output signal is a sine wave with a DC component (median value). This ensures the signal is always positive, making it directly compatible with Arduino or ESP32 analog pins.

Pin Configuration

• Input Terminals (Screw Terminal):
  • L (Line): Connect to the AC Phase/Live wire.
  • N (Neutral): Connect to the AC Neutral wire.
• Output Header (4-Pin):
  • VCC: DC Power (5V–30V).
  • GND: Ground.
  • OUT: Analog Signal Output.
  • GND: Ground (often redundant).

Common Applications

• Mains Voltage Monitoring: Real-time tracking of household or industrial AC voltage stability.
• Smart Energy Meters: Measuring power consumption when paired with a current sensor.
• Power Quality Analysis: Detecting voltage sags, surges, or frequency variations.
• Protection Relays: Triggering an alert or shutdown if AC voltage goes outside safe limits.

Usage Tips

• Calibration: To measure the actual RMS voltage, you must take multiple samples over at least one full AC cycle (20ms for 50Hz) and calculate the Root Mean Square in your code.
• DC Filtering: If you only need the AC component (raw sine wave without the offset), you can connect a 1uF (105) capacitor in series with the OUT pin.
• Safety First: Although the module provides isolation, the input side carries lethal 230V AC. Always ensure the module is securely mounted and that the high-voltage terminals are insulated during operation.