What is a Current Sensor
A Current Sensor detects electric currents in circuits to generate signals proportional to that current. The signals can be displayed, measured or stored for further analysis. Current sensors will measure AC and DC current. While the physical principles are the same, the details of a “current” sensor compared with a voltage transformer will differ owing to different requirements of the application. Shop now and see our wide ranges of current sensing and voltage sensing products.
Current sensors are of two main types, open or closed loop. The open-loop current sensors measure AC and DC currents and provide electrical isolation between the circuit being measured and the output of the sensor (the primary current is measured without electrical contact with the primary circuit, providing galvanic isolation). Open loop current sensors are usually preferred in battery-powered circuits for their low power needs and small footprint features. Open-loop current sensors are also typically cheaper than closed loop sensors.
Closed Loop CT’s
Closed-loop sensors provide electrical isolation and measure AC and DC currents. They ideal for their fast response, low temperature drift and high linearity. The closed-loop sensor current output is relatively immune to electrical noise. Due to its Hall-Effect sensor feeds back an opposing current into a secondary coil, the Closed- Loop sensor is sometimes called a ‘Zero-Flux’ sensor. The secondary coil is wound on the magnetic core to zero the flux produced in the magnetic core by the primary current. When high accuracy is priority, closed-loop sensors are a good choice of sensor.
Open Loop CT’s
Open loop current sensors have a Hall sensor mounted in the air gap of a magnetic core. A conductor gives a magnetic field that is comparable to the current. The magnetic field is measured by the Hall sensor and concentrated by the core. The signal from the Hall generator is amplified as it is low, this amplified signal becomes the sensor’s output. Normally open-loop sensors have circuitry that provides temperature compensation and calibrated high-level voltage output. While they are cheaper than their counterparts, they can be prone to saturation and temperature drift. However by injecting a positive coefficient in the control current to reduce the drift in sensitivity over temperature the drift can be minimised.
3 Types of Current Sensors
Hall Effect – Hall Effect current sensors have a core, Hall Effect device and signal conditioning circuitry. When the Hall device is exposed to magnetic field from the core it produces a potential difference which can be measured and amplified. Current Sensors work when a current conductor passes through a magnetically permeable core that concentrates the conductors magnetic field. Inductive – This type of sensor uses coils which current-carrying wires pass. Making power that is proportional to the current flow in the coil. The current flow then can be measured or transformed. Magnetoresistive – The property of certain materials changes the value of its resistance when a current flows through the plate. When currents flow for a longer distance, resistance is increased and decreased at the shorter distance.
Current sensors generate a proportional signal for measurement and control by detecting electric current in a wire. While the physical principles are the same, the details of a “current” transformer compared with a voltage transformer will differ owing to different requirements of the application. Shop now and see our wide ranges of current sensing and voltage sensing products.
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