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Figure 12.12, with the result that the effects of noise are reduced. However, because of the
accumulation of error, the technique must balance the integration period against error accumulation.
Differentiation tends to be extremely sensitive to low amplitude, high-frequency noise, which can
create very large errors in derivatives, especially at high sampling frequencies. This is apparent in
Figure 12.14, in which the signal in Figure 12.12 has been differentiated numerically. Appropriate
filtering or smoothing techniques are generally effective at reducing errors associated with noise in
derivatives in cases where the noise has low amplitude.
Moving Coil Transducers
Moving coil transducers take advantage of the voltage generated when a conductor experiences a
displacement in a magnetic field. This is the same phenomenon used to generate electric power in
generators and alternators. An illustration of a moving coil velocity pickup is provided in
Figure 12.15. Recall that a current carrying conductor experiences a force in a magnetic field,
and that a force is required to move a conductor in a magnetic field. For the latter case, an emf is
induced in the conductor. Consider the case in which the magnetic field strength is at right angles to
the conductor. The induced emf is given by
emf ¼ pBD c lN
dy
dt
ð12:14Þ
Figure 12.13 Result of integrating the noisy signal from Figure 12.12.
520 Chapter 12 Mechatronics: Sensors, Actuators, and Controls
13:54:10 Page 520
Figure 12.12, with the result that the effects of noise are reduced. However, because of the
accumulation of error, the technique must balance the integration period against error accumulation.
Differentiation tends to be extremely sensitive to low amplitude, high-frequency noise, which can
create very large errors in derivatives, especially at high sampling frequencies. This is apparent in
Figure 12.14, in which the signal in Figure 12.12 has been differentiated numerically. Appropriate
filtering or smoothing techniques are generally effective at reducing errors associated with noise in
derivatives in cases where the noise has low amplitude.
Moving Coil Transducers
Moving coil transducers take advantage of the voltage generated when a conductor experiences a
displacement in a magnetic field. This is the same phenomenon used to generate electric power in
generators and alternators. An illustration of a moving coil velocity pickup is provided in
Figure 12.15. Recall that a current carrying conductor experiences a force in a magnetic field,
and that a force is required to move a conductor in a magnetic field. For the latter case, an emf is
induced in the conductor. Consider the case in which the magnetic field strength is at right angles to
the conductor. The induced emf is given by
emf ¼ pBD c lN
dy
dt
ð12:14Þ
Figure 12.13 Result of integrating the noisy signal from Figure 12.12.
520 Chapter 12 Mechatronics: Sensors, Actuators, and Controls