## 4.6 Acceleration Transducers

Acceleration transducers or accelerometers use piezoelectric, strain gauge, variable reluctance, or integrated circuit technology as basic principles of operation.

### 4.6.1 Acceleration and Acceleration Measurement

Acceleration is a measure of how the velocity is changing with respect to time. Acceleration is a vector quantity and thus has a magnitude and a direction. The units of acceleration include inches per second per second (inches per second squared) or feet per second per second (feet per second squared). Another unit of acceleration is the g, which is the acceleration of a body due to the force of the earth's gravity. One g is equal to 32.2 feet per second squared or 9.81 meters per second squared.

Transducers that are used to measure acceleration are normally called accelerometers. They are used most commonly to measure the vibration of an object.

### 4.6.2 Piezoelectric Acceleration Transducer

Piezoelectric accelerometers (see Figure 4-28) are constructed using a mass that is spring loaded against a crystal. Accelerating the transducer will increase or decrease the force on the crystal, depending on the direction of the acceleration. The magnitude of the force is equal to the mass times the acceleration (F = ma). The force acting on the crystal will produce an electrical charge across opposite faces of the crystal that is proportional to the applied force. We thus have a transducer that produces a charge output that is proportional to acceleration.

(Courtesy, Br el & Kj r)

Figure 4-28: Piezoelectric Accelerometer

As with the piezoelectric pressure transducer, the...

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Accelerometers
Accelerometers are instruments for measuring, displaying, and analyzing acceleration and vibration.
Shock and Impact Sensors
Shock and impact sensors are devices that detect sudden or severe impacts at a predetermined level and indicate whether the level has been exceeded.
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Piezoelectric sensors measure the electrical potential caused by applying mechanical force to a piezoelectric material. They are used in a variety of pressure-sensing applications.
Inertial navigation systems use a combination of accelerometers and angular rate sensors (gyroscopes) to detect altitude, location, and motion. They may also be capable of detecting attitude, position, velocity, temperature, or magnetic field.
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Shock and vibration testing shakers are force generators or transducers that provide a vibration, shock, or modal excitation source for testing and analysis.

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