Measurement and associated experimental techniques play a significant role in the practice of vibration. The objective of this chapter is to introduce the instrumentation that is important in vibration applications. Chapter 9 provides complementary material on signal conditioning associated with vibration instrumentation. Academic exposure to vibration instrumentation usually arises in laboratories, in

relation to learning, training, and research. In vibration practice, perhaps the most important task of instrumentation is the measurement or sensing of vibration. Vibration sensing is useful in the following applications:

1. Design and development of a product

2. Testing (screening) of a finished product for quality assurance

3. Qualification of a good-quality product to determine its suitability for a specific application

4. Mechanical aging of a product prior to carrying out a test program

5. Exploratory testing of a product to determine its dynamic characteristics such as resonances, mode shapes, and even a complete dynamic model

6. Vibration monitoring for performance evaluation

7. Control and suppression of vibration

Figure 8.1 indicates a typical procedure of experimental vibration, highlighting the essential instrumentation. Vibrations are generated in a device (test object) in response to some excitation. In some experimental procedures (primarily in vibration testing, see Figure 8.1), the excitation signal has to be generated in a signal generator, in accordance with some requirement (specification), and applied to the object through an exciter after amplification and conditioning. In some other situations (primarily in performance monitoring and vibration control), the excitations are generated as an integral part of the operating environment of the vibrating object and may originate either within the object (e.g., engine excitations in an automobile) or in the environment with which the object interacts during operation (e.g., road disturbances on an automobile). Sensors are needed to measure vibrations in the test object. In particular, a control sensor is used to check whether the specified excitation is applied to the object, and one or more response sensors may be used to measure the resulting vibrations at key locations of the object.