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Current sensing
Larger version - 29K - Click For a given current flow, a proportional magnetic field is produced around the current carrying conductor. NK Technologies current sensors measure this field using one of two technologies. For DC currents, we use "Hall Effect" while for AC currents, we use "Inductive" technology.

The Hall Effect sensor has a core, Hall Effect device and signal conditioning circuitry. The current conductor passes through a magnetically permeable core that concentrates the conductor's magnetic field. The Hall Effect device is mounted in the core at a right angle to the concentrated magnetic field. A constant current in one plane excites the Hall device. When the energized Hall device is exposed to a magnetic field from the core, it produces a potential difference (voltage) that can be measured and amplified into process level signals such as 4-20mA or a contact closure.

The Inductive sensor has a wire-wound core and a signal conditioner. The current conductor passes through the core that magnifies the conductor's magnetic field. AC current constantly changes potential from positive to negative and back again, generally at the rate of 50 or 60 Hz. The expanding and collapsing magnetic field induces current in the windings. This secondary current is converted to a voltage and conditioned to output process-level signals such as 4-20mA or contact closures.

Link to Sensors Magazine Article

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