29.4 VIBRATION MEASUREMENT

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Vibration Source - hammers can be used to generate impulse/step function responses. Load cells/vibrators can be used to excite frequency responses (Bode plots and phase shift plots)

Sensors - Velocity Pickups/Accelerometers - lightweight devices that are mounted on structures. They produce small voltages (approx. 10mV). Velocity meters are not as accurate as accelerometers. Accelerometers are very common, and are used for vibrations above 1KHz. Many other sensors are possible.

Preamplifiers - Can power sensors, filter and amplify output.

Signal Processor - Many types used, from software packages, to older pen based plotters, or tape recorders

Consider the example of an amplitude and phase plot measured for a real device,