Current Probe Working Principles
A current probe is an electrical sensor used to measure the current flowing through a conductor without breaking the circuit.
1. Hall-Effect Sensors (AC/DC)
For measuring both AC and DC, probes utilize a Hall-Effect Sensor. When current flows through a wire, it creates a magnetic field. The probe's core concentrates this field onto a semiconductor (the Hall element). A small voltage is generated across the semiconductor that is proportional to the current in the wire.
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2. Rogowski Coils (AC Only)
A Rogowski Coil is an air-cored helical coil. It measures the rate of change of current ($di/dt$). The output voltage from the coil is then electronically integrated to provide a signal proportional to the actual current. These are ideal for measuring high-speed transients or very high currents because they do not have a magnetic core that can "saturate."
3. Current Transformers (Passive AC)
The most basic current probe is a Current Transformer (CT). The wire being measured acts as the primary winding of a transformer, and the probe contains the secondary winding. This type is very robust but can only measure alternating current (AC).