What Are Hall-Effect Sensors

Hall-Effect Sensors are semiconductor wafers . When a Hall-Effect sensor is placed in a magnetic field, it generate an electronic signal whose amplitude is directly proportional to the strength of the magnetic flux.

The basic Hall-Effect sensor was discovered by E. F. Hall in 1879. It is a semiconductor wafer with special magnetic characteristics. When a voltage is applied across one axis of the wafer, the other axis generates a current which is proportional to the magnetic field that is perpendicular to the wafer. In the absence of a magnetic field, the output current is virtually non-existent. Because of this feature, the sensors are sometimes called a "Hall Generator".

Hall-Effect sensors are used in many applications that include AC/DC current transformers, AC/DC current clamps, Gausmeters, ignition systems, speed control systems, security systems, DC circuit breakers, battery powered vehicles, alignment controls, micrometers, mechanical limit switches, machine tools, tachometers, linear potentiometers, current sensing in DC motors and many other applications. They are virtually immune from environmental contaminants and are suitable for use under severe service conditions. They are sensitive to very small magnetic fields and provide reliable and repetitive operation in close tolerance applications.

Magnetic fields have two important characteristics: flux density and polarity. When an electrical current flows in a conductor, it generates a magnetic flux whose density is proportional to the current level. If the current is DC, the flux direction has the same polarity as the current. If the direction of the DC current is reversed, the flux polarity reverses. If the current is AC, the flux density follows the amplitude changes and the polarity of the current. Standard AC current transformers that are used in the electric power industry can sense only AC currents. They are generally specified to meet an accuracy level at the power line frequency, generally at 50 or 60 Hz or 400 Hz. They function only as sensors of alternating flux that is present at power line frequencies. They cannot measure DC currents.

Hall-Effect current sensors can sense both AC and DC magnetic fields and can generally be specified to operate over a frequency range of DC to several thousand Hertz. As such, they are ideal for measuring DC currents and very low frequency currents, and they are capable of capturing the energy that is generated by higher harmonics of high distortion currents that exist in SCR circuits, switching power supplies and other non-linear loads. A highly non-linear load powered by a 60 Hz power line may generate many harmonic frequencies. If an AC current transformer has a frequency range of 50 to 500 Hz, it will not measure the harmonic components of the current above the 8th harmonic, while a Hall-Effect sensor could measure beyond the 35th or 50th harmonic. The AYA Hall-Effect current clamps are specified to operate over frequency ranges of DC (direct Current) and AC up to 2,000 Hz.

Hall-Effect sensors provide an output signal whose value is proportional to the flux density of the magnetic field generated by the current being monitored. The electronic circuits in the AYA Hall-Effect current clamps amplify the signal to provide an analog DC or AC/DC signal which is proportional to the current being measured.

Hall-Effect sensors are used in many AYA current clamps for measuring currents as low as 10 Milliamperes and as high as 15,000 Amperes DC ot 30,000 Amperes Peak-to-Peak.

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