This document discusses acceleration and velocity sensors. It describes four main types of acceleration sensors: piezoelectric, piezoresistive, capacitive, and servo. It also explains four types of velocity sensors: magnetic, optical, piezoelectric, and GPS sensors. The document outlines the working principles, components, and applications of these different sensor types for measuring acceleration and velocity.

1. Acceleration and
Velocity Sensors
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3. Acceleration Sensor
• An acceleration sensor is a device which measure how something speed
ups or down.
• It is usually composed of a mass block, damper, elastic
element, sensitive element and an adaptive circuit.
• During the acceleration process, the sensor uses Newton's second law
to obtain the acceleration value by measuring the inertial force applied
to the mass.
• According to the different sensitive elements of the sensor, common
acceleration sensors include capacitive, inductive, strain, piezoresistive,
and piezoelectric type
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4. Types of Acceleration
Sensors
Piezoelectric
Piezoresistive
Capacitive
Servo
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5. 1] Piezoelectric
• Piezoelectric acceleration sensors measure acceleration, vibration,
and shock by converting mechanical energy into electrical signals.
• They rely on the piezoelectric effect, which is the ability of certain
materials to generate an electric charge when subjected to
mechanical stress.
• The sensor consists of a piezoelectric crystal sandwiched between
two electrodes.
• When the sensor is subjected to acceleration, the crystal deforms,
generating an electric charge that is proportional to the magnitude
of the acceleration.
• Piezoelectric acceleration sensors are widely used in various
industries, such as aerospace, automotive, and industrial
applications, due to their high sensitivity, low noise, and wide
frequency range.
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6. 2] Piezoresistive
• Based on the world's leading MEMS silicon
micromachining technology, the
piezoresistive acceleration sensor has the characteristics
of small size and low power consumption
• It is easy to be integrated into various analog and digital
circuits.
• It is widely used in automobile crash experiments, testing
instruments, equipment vibration monitoring, etc...
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7. 3] Capacitive
• The capacitive acceleration sensor is a capacitive
sensor with great changes based on the principle of
capacitance.
• The capacitive accelerator is irreplaceable in certain
fields, such as airbags, mobile devices, etc.
• It usually adopts the micro-electromechanical system
(MEMS) technology, which is economical in mass
production, thus ensuring lower cost.
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8. 4] Servo
• The servo acceleration sensor is a closed-loop test
system, which has good dynamic performance, a large
dynamic range, and good linearity.
• The vibration system of the sensor is the "m-k" system
, which is the same as the general acceleration sensor,
but there is an electromagnetic coil on the mass m.
• When there is acceleration input on the base, the
mass deviates from the equilibrium position, and the
displacement is detected by the displacement sensor,
amplified by the servo amplifier, and converted into a
current output.
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9. Working Principle
• Acceleration sensors work according to the principle of the piezoelectric
effect.
• Piezoelectric effect states that "the external force applied to a heteropolar
crystal without asymmetric center will not only deform the crystal but also
change the polarization state of the crystal and establish an electric field
inside the crystal.
• The general acceleration sensor utilizes the characteristic of crystal
deformation due to the acceleration inside.Since this deformation
generates a voltage, as long as the relationship between the generated
voltage and the applied acceleration is calculated, the acceleration can be
converted into a voltage output.
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11. Applications
• Vehicle safety : the acceleration sensor is mainly used in safety performance
as automobile airbags, anti-lock brake systems, traction control systems, and so on.
• Game control : the acceleration sensor can detect the change of the inclination angle.
Therefore, it is easy to control the directions of the objects in the game by tilting the
handheld device forward and backward
• Tilt correction of electronic compass : the acceleration sensor can measure the tilt angle,
it can compensate for the tilt of the electronic compass.
• Image stabilization : acceleration sensor to detect the vibration/shake amplitude of the
handheld device.
• Hard disk protection : the acceleration sensor is used to detect the free-fall
state, thereby protecting the mini hard disk.
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12. Velocity Sensors
A velocity sensor, also known as a speed sensor or a motion
sensor, is a device that measures the velocity or speed of an
object or system. It detects changes in position over time and
calculates the rate at which the position is changing. In addition
to measuring speed, some velocity sensors can also measure
other parameters such as acceleration, displacement, and
position. They can also be used in conjunction with other
sensors such as temperature sensors, pressure sensors, and
strain gauges to provide a more comprehensive picture of the
performance of a system or component.
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13. Types of Velocity
Sensors
Magnetic
Optical
Piezoelectric
Gps Sensors
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14. Magnetic Velocity Sensors
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• A magnetic velocity sensor consists of a magnetic field sensor that
measures the changes in the magnetic field caused by a moving
object
• The sensor is placed close to a rotating shaft or gear, and as the shaft
rotates, it generates a magnetic field that varies with time.
• The sensor detects these changes and converts them into a signal
that can be used to calculate the speed of the rotating shaft.
• They are commonly used in automotive and industrial applications to
monitor the speed of rotating machinery such as engines, motors,
and turbines.

15. Optical Velocity Sensors
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• These sensors use light to detect changes in position and measure the
speed of an object or system.
• an optical velocity sensor uses a light emitter and receiver to measure
changes in the position of an object over time.
• The emitter sends out a beam of light, which is reflected off the moving
object and detected by the receiver.
• The position of the object is determined by analyzing the changes in the
reflected light, and the speed is calculated by measuring the rate at
which the position is changing.
• They are commonly used in robotics, aerospace, and industrial
applications where high accuracy and precision are required.

16. Piezoelectric Velocity Sensors
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• These sensors use a piezoelectric material that generates an electrical
charge in response to mechanical stress or vibration.
• Piezoelectric velocity sensors work by converting mechanical energy
into electrical energy.
• The sensor consists of a piezoelectric material that generates an
electrical charge when it is subjected to mechanical stress or vibration.
• As the object or system being monitored vibrates or moves, the
piezoelectric material generates an electrical charge that is proportional
to the velocity of the object.
• They are commonly used to monitor the vibration and speed of
machinery in industrial applications.

17. GPS Velocity Sensors
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• GPS velocity sensors use GPS (Global Positioning System) technology to
determine the velocity of an object or system.
• The GPS velocity sensor works by measuring the changes in the position
of a GPS receiver over time. The GPS receiver receives signals from
multiple GPS satellites in orbit around the Earth.
• By analyzing the time it takes for the signals to travel from the satellites
to the receiver, the GPS receiver can calculate its position on the Earth's
surface.
• GPS velocity sensors can provide highly accurate velocity
measurements, especially over long distances and high speeds. They are
commonly used in a variety of applications, including navigation,
aviation, marine, and automotive industries.

18. Applications
• Accurate and precise measurements: Velocity sensors can provide highly accurate and
precise measurements of the speed or velocity of an object or system.
• Real-time monitoring: Velocity sensors can provide real-time monitoring of the speed or
velocity of a system or component.
• Non-contact measurement: Many velocity sensors use non-contact measurement
techniques, such as optical or magnetic sensors
• Non-contact measurement: Many velocity sensors use non-contact measurement
techniques, such as optical or magnetic sensors
• Integration with other sensors: Velocity sensors can be integrated with other sensors,
such as temperature sensors, pressure sensors,etc
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