Any type of current flow creates a proportional magnetic field, and DC current transducers measure this generated field using Hall Effect technology. Hall Effect is defined as the generation of a magnetic field perpendicular to the current and a voltage difference across an electrical conductor transverse to an electrical current in the conductor. This article discusses how Hall Effect devices work, their limitations, and how they can be improved.
Understanding Hall Effect devices
A Hall Effect-based transducer is generally composed of a signal conditioning circuitry, a core, and a Hall Effect device. The current conductor travels through a magnetically pervious core that focuses the conductor’s magnetic field. Inside the core is the Hall Effect device mounted in a right angle to the focused magnetic field. When the Hall device detects a magnetic field, it produces a potential voltage that could be amplified by the transformer it is attached to into the standards desired by the user.
A new type of Hall Effect technology
Hall Effect sensors are a widely accepted means of measuring current. With the existing technology, however, the devices are subject to measurement inaccuracy over time since they’re sensitive to other magnetic fields outside of the current to be measured, causing magnetic field error. Researchers are trying to make the devices a more accurate long-term solution. Sensors Magazine guest contributor James Sterling suggests one possible answer: coreless sensing technology with galvanic isolation.
According to Sterling, a coreless differential Hall-based device can address the problems associated with most Hall-based solutions, because instead of a ferrite core focusing on the current, the current pathway is spread throughout the sensor device. This could effectively remove the magnetic field error of the ferrite core, thereby limiting the offset error to below 25mA over a sensor’s lifetime.
The article adds that the differential dual-Hall cell technology also gets rid of any magnetic offset between two Hall measurements, strengthening the magnetic field. The new Hall device assembly incorporates up to 2.5kV of Galvanic isolation, effectively removing the need for optocouplers.
(Source: Hall Effect Accurate Current Measurement Without Power Dissipation And Added Impedance, Sensors, Dec. 5, 2014)