The ZMCT103C is a high-precision, micro-current transformer module designed for safe and non-invasive AC current monitoring. Using a 1000:1 transformation ratio, it converts a high-current AC signal (up to 5A) into a small milliampere signal. This module is ideal for measuring power consumption and monitoring motor loads, providing 3000V of insulation for electrical safety.

Specifications

• Rated Input Current: 5A AC
• Rated Output Current: 5mA at 5A input (1000:1 ratio)
• Linear Range: 0A to 10A (typically with a 100 Ohm sampling resistor)
• Linearity & Precision: 0.2%
• Insulation Voltage: 3000V
• Operating Temperature: -40C to +70C
• Sealing: Epoxy resin for durability and moisture resistance

Working Principle

This is a passive Current Transformer (CT). The AC wire to be measured is passed through the hole in the centre of the black transformer (the "donut"). As AC current flows through that wire, it induces a proportionally smaller current in the module's secondary coil.

Features

• Non-Invasive Sensing: No need to cut or strip the wire being measured; simply pass the live or neutral wire through the centre hole.
• High Precision and Linearity: With a 0.2% linearity rating, this module provides highly accurate data suitable for energy auditing and digital watt meters.
• Excellent Isolation: The 3000V insulation rating ensures that the high-voltage AC side is completely isolated from your low-voltage microcontroller (Arduino, ESP32, etc.).
• Ultra-Compact Design: One of the smallest AC current sensors available, making it easy to integrate into small distribution boxes or smart plugs.
• Onboard Sampling Resistor: Most versions of this module include an onboard "burden" resistor that converts the 5mA output current into a measurable analog voltage.

Pin Configuration

• Centre Hole: Pass one AC wire (Live or Neutral) through this hole. Do not pass both, as the magnetic fields will cancel each other out.
• Out: Analog signal output (Sine wave proportional to the measured AC current).
• GND: Ground connection.

Common Applications

• Smart Home Energy Monitoring: Measuring the current draw of individual appliances.
• Overload Protection: Sensing when a motor or heater is drawing more current than safe limits.
• AC Load Detection: Confirming if a remote device (like a pump) is actually powered on.
• Industrial Automation: Real-time current feedback for small-scale control systems.

Usage Tips

• Analog Waveform: The output is a raw AC sine wave. To read this with an Arduino, you must either use a DC offset circuit or take many samples rapidly to calculate the Peak-to-Peak or RMS value.
• Burden Resistor: If your specific module does not have an onboard resistor, you must add one (e.g., 100 Ohm) across the output terminals to convert the current signal into voltage.
• AC Only: This sensor only detects AC. It will not work with DC current because a changing magnetic field is required to induce current in the transformer.