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BB Automacao researches and develops magneto resistive (GMR), capacitive,
magneto elastic, inductive eddy current, and Bragg grating
sensors for the measurements of geometric and mechanical quantities (displacement, length, velocity, acceleration, force, stress, strain, vibration and shock etc.).
The developed sensors have a high sensitivity and good linearity and can be applied to automation machines, machine tools, vehicles,
bridges and buildings etc. The most measurements are contactless.
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GMR Displacement Sensors |
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A GMR displacement sensor consists of a position magnet and a GMR receiver. The permanent magnet sends
magnetic field to the GMR receiver. The field intensity through the GMR sensor is a function of the distance
between the magnet and receiver. The output signal of GMR sensor changes with the displacement when the position
magnet moves. After analog signal processing the output voltage is
proportional to the displacement. |
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Inductive Eddy Current Sensors |
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An Eddy Current Sensor consists of a ferrite U-core and a coil. The permeability of the device under test
(DUT) is changed by applying a force/stress on the DUT. As result the impedance of the sensor coil
changes with the force. The impedance change can be converted to a voltage change by using a measuring
bridge. The force and stress applied on the DUT can be derived by the voltage measurement. The sensitivity
and hysteresis depends on sensor geometry and the electrical measuring conditions. The relation between
the impedance and measurand of an optimized sensor is linear. The mean correlation coefficient is better
than -0.996. The hysteresis of the loading and unloading curves is less than 3%. These sensors can be
applied to force and stress measurement, and to bridge monitoring.
They can also be used for
Contactless Displacement Measurement
in control engineering and vibration measurement of rotatory machines and nano-positioning etc. |
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Capacitive Sensors |
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The simplest configuration of a capacitive sensor is two close-spaced parallel plates. The capacitance
of the sensor is proportional to the area of the electrodes and the dielectric constant, and inversely
related to the space between the parallel plates. Therefore motion, distance and position, dielectric
constant etc. can be directly measured with a capacitive sensor. Capacitive sensors have a very high
sensitivity. As motion detector a sensor can detect less than 10-10m
displacements with good stability and high speed. They can be applied to the positioning of photolithography
and the wafer-positioning in the semiconductor technology. Capacitive sensors can be integrated in
accelerometer ICs with a sensitivity of about 1.5g, and find a lot of applications to the measurements of
position/distance, vibration, pressure, liquid level etc. in control engineering.
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Magnetoelastic Sensors |
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A magneto elastic Sensor works according to the magneto elasticity
of soft ferromagnetic materials. The permeability of a magneto
elastic tape is changed
if a force/strain (wave or vibration) is applied to the magneto
elastic tape. The flux lines created
by a bias-magnet changes with the permeability of the tape. An output voltage is generated
in the detector coil. This signal is proportional to the intensity of the applied force/strain.
Magneto elastic sensors have a very high sensitivity. Strains less than 10 -10 can
be detected with the small magneto elastic sensors developed by BB Automacao.
Therefore, these sensors
are suitable for vibration and knock (shock) sensor applications in automobile and mechanical
engineering.
They can be applied to monitoring systems of machines and buildings, and to the detection of very
weak seismic signals etc. |
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