Current Sensing

Current sensing is the process of measuring or detecting the flow of electric current through a conductor or circuit. The information can be used to monitor equipment, control power delivery, measure energy use or detect conditions such as an overload. Current sensing is common in power supplies, motor controls, industrial equipment and electrical monitoring systems.

There are several ways to sense current. A shunt resistor measures the small voltage drop created as current passes through a known resistance. Hall-effect sensors detect the magnetic field associated with current flow. Another approach uses a current transformer, which relies on electromagnetic induction to produce a measurable signal related to alternating current in a conductor.

A typical current transformer has a magnetic core and a secondary winding. The conductor carrying the current being measured acts as the primary winding, sometimes passing through the core only once. Alternating current in that conductor creates a changing magnetic field, which induces current in the secondary winding. The relationship between the primary and secondary currents is determined largely by the winding turns ratio, within the device’s operating limits.

Conventional current transformers are designed for alternating current and do not measure steady direct current. Hall-effect devices and suitable shunt-based circuits can be used for direct-current measurements. The appropriate sensing method depends on the current range, required accuracy, electrical isolation and operating environment.

In magnetic component manufacturing, current sensing is especially relevant to wound current transformers and related sensor assemblies. Their core material, winding design and electrical connections help determine how accurately the component can represent current in the larger system.