Monday, October 31, 2005

Acceleration

the Definition of:

The rate of change of velocity. Measurement of acceleration breaks into two main categories: for large moving objects, the acceleration is a very low frequency measurement proportional to the change in velocity of the entire object, such as a car or aircraft. For example, we speak of the acceleration of an automobile from 0 to 100 km/h (or 0 to 60 mph).

The second category is primarily used in vibration measurements, where the dynamic changes of the surface of an object are measured. For example, the resonance of an automobile muffler may result in vibrations at a frequency of 67 Hz.

Function of Capacitive Accelerometers
Capacitive accelerometers sense a change in electrical capacitance, with respect to acceleration, to vary the output of an energized circuit. The sensing element consists of two parallel plate capacitors acting in a differential mode.

These capacitors operate in a bridge circuit, along with two fixed capacitors, and alter the peak voltage generated by an oscillator when the structure undergoes acceleration. Detection circuits capture the peak voltage, which is then fed to a summing amplifier that processes the final output signal.

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