A piezoelectric accelerometer utilizes the piezoelectric effect of certain materials to measure dynamic changes in mechanical variables, such as mechanical shock, vibration and acceleration. Like other transducers, piezoelectric accelerometers convert one form of energy into another and provide an electrical signal in response to the condition, property or quantity. Acceleration acts upon a seismic mass that is restrained by a spring or suspended on a cantilever beam, and converts a physical force into an electrical signal.
There are two types of piezoelectric accelerometers: high and low impedance. High impedance accelerometers have a charge output that is converted into a voltage using a charge amplifier or external impedance converter. Low impedance units use the same piezoelectric sensing element as high-impedance units, and incorporate a miniaturized built-in charge-to-voltage converter and an external power supply coupler to energize the electronics and decouple the subsequent DC bias voltage from the output signal.
Working Principle of Piezoelectric Accelerometer
A piezoelectric accelerometer consists of a mass attached to a piezoelectric crystal which is mounted on a case. When the accelerometer body is subjected to vibration, the mass on the crystal remains undisturbed in space due to inertia. As a result, the mass compresses and stretches the piezoelectric crystal. This force is proportional to acceleration in accordance with Newton’s second law, F = ma, and generates a charge.
The charge output is then converted into low impedance voltage output with the help of electronics.
Benefits of Piezoelectric Accelerometer
The key benefits of piezoelectric accelerometers are:
- Wide frequency range
- No moving parts
- Excellent linearity over their dynamic range
- Low output noise
- Self-generating - no external power required
- Acceleration signal can be integrated to provide velocity and displacement
Major applications of piezoelectric accelerometers include:
- Engine testing - Combustion and dynamic stressing
- Ballistics - Combustion, explosion, and detonation
- Industrial/factory - Machining systems, metal cutting, and machine health monitoring
- Original equipment manufacturer - Transportation systems, rockets, machine tools, engines, flexible structures, and shock/vibration testers
- Engineering - Dynamic response testing, shock and vibration isolation, auto chassis structural testing, structural analysis, reactors, control systems and materials evaluation
- Aerospace - Ejection systems, rocketry, landing gear hydraulics, shock tube instrumentation, wind tunnel and modal testing.