A kind of magnetic sensor
that detects changes
in the strength
of a magnetic field
. It consists of a wire
coiled around a magnet
, with a steady current
pumped through. If something metallic
passes close to the magnet, it will effectively become an extension
of the magnet, and change the permeability
within the wire's coils, which will translate into a change in the impedance
of the wire.
Magnetoresistive sensors are found in metal detectors, both the beachcombing kind and the kind you find in airports. Automobile detectors at traffic lights are another example.
They are also popular for use in machinery, where they can count the number of cogs that pass by on a wheel, yet can also stand getting some grease slathered on them.