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Closed
Loop Hall effect current transducers
Operation principle
A closed loop current
sensor consists of a Hall generator mounted in an air gap of a
magnetic core, a coil wound around the core and a current amplifier.
The current carrying conductor placed through the aperture of the
sensor produces a magnetic field that is proportionate to the
current. This field is concentrated by the core and sensed by the
Hall generator. The Hall generator is connected to the input of the
current amplifier, which drives the coil. The current through the
coil produces an opposing field to that provided by the current
through the aperture Thus the flux in the core is constantly driven
to zero. The coil connects the output of the sensor.
Therefore the output is a
current proportional the aperture current multiplied by the number
of turns on the coil. A sensor with a 1000 turn coil provides an
output of 1mA per ampere. The current output is converted to a
voltage by connecting a resistor to the output of the sensor and
ground. The output is scaled by selecting the resistor value.
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1. Measuring Principle
The magnetic flux created by the
primary current lp is balanced by a
complementary flux produced by driving a current through the
secondary windings.
A hall device and associated
electronic circuit are used to generate the secondary (compensating)
current that is an exact representation of the primary
current. |
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Closed loop sensors measure dc and ac currents and provide
electrical isolation. They offer fast
response, high linearity and low temperature drift. The current
output of the closed loop sensor
is relatively immune to electrical noise. They are the sensor of
choice when high accuracy is
essential.
Features:
• Wide frequency range
• Good overall accuracy
• Fast response time
• Low temperature drift
• Excellent linearity
• No insertion losses
5.
Typical Applications
• General
Purpose Inverter
• AC/DC Variable Speed Drivers
• Battery Supplied Applications
• Uninterruptible Power Supplies
• Switched Mode Power Supplies
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