A switched-output residual current sensor detects residual current in a circuit and outputs a switching signal. It is used mainly for electrical safety protection: once residual current exceeds a preset threshold, the sensor outputs a signal that triggers an alarm or cuts the power, preventing electrical fires and electric shock.

Key Functions

• Residual current detection — continuously monitors residual (leakage) current in the circuit.
• Switched output — issues a switching signal (normally open or normally closed) when residual current exceeds the set value.
• Fault protection — works with circuit breakers or relays for automatic power disconnection.
• Easy integration — the switched output connects directly to PLCs, alarm systems, and similar equipment.

Working Principle

1. Alternating magnetic field. Alternating current through the excitation coil creates an alternating field that drives the magnetic flux density in the fluxgate element around saturation.
2. Magnetization of the fluxgate element. The flux density changes periodically; on reaching saturation, the core permeability shifts abruptly — the fluxgate effect.
3. Flux variation detected by the measuring coil. Coupled to the fluxgate element, the coil induces an electromotive force (EMF) whenever the flux changes.
4. Signal processing. The EMF is amplified, filtered, and A/D-converted into a digital signal proportional to the measured current.

Features and Applications of Fluxgate Current Sensors

• Wide range, high accuracy, fast response, strong immunity — which is why fluxgate sensors are widely used in power systems, industrial automation, and new energy.
• Higher sensitivity than Hall-effect designs — with better measurement accuracy and a more stable fluxgate probe.
• Simple structure — a high-permeability core, excitation coil, measuring coil, and signal processing circuit.

Together, these properties let fluxgate current sensors measure and analyze current effectively across a wide range of scenarios.

Selection Guide

• Rated current — match the sensor to the circuit's rated current.
• Residual current threshold — choose the leakage trip value, e.g. 30 mA, 100 mA, or 300 mA.
• Output type — normally open (NO), normally closed (NC), or adjustable.
• Response time — faster response means earlier protective action.
• Mounting — DIN-rail, panel, or flush mounting.
• Environment — check temperature, humidity, and ingress protection (IP) rating.

Common Types

• AC residual current sensors — for AC circuits.
• DC residual current sensors — for DC circuits.
• Multi-function models — combine leakage detection, overload protection, and temperature monitoring.

Installation and Usage Precautions

• Wire correctly — follow the manual to ensure proper operation.
• Test regularly — verify functionality periodically to prevent silent failure.
• Avoid interference — keep the sensor away from strong electromagnetic sources to prevent false tripping.
• Match the load — confirm the switching output's load capacity suits downstream equipment.

Advantages

• Simple and reliable — the switched output triggers protection directly, with no complex configuration.
• Cost-effective — more economical than analog-output sensors.
• Easy to integrate — compatible with a wide range of protection systems.

Chosen and applied correctly, switched-output residual current sensors are a dependable safeguard for personnel and equipment safety.