19 - Translational motion transducers

Abstract

This chapter discusses about translational displacement transducers, which are instruments used to measure the motion of a body in a straight line between two points. The resistive potentiometer is perhaps the best-known displacement-measuring device. The piezoelectric transducer is effectively a force-measuring device that is used in many instruments measuring force, or the force-related quantities of pressure and acceleration. The nozzle flapper is a displacement transducer that translates displacements into a pressure change. The linear inductosyn is an extremely accurate instrument that is widely used for axis measurement and control within machine tools. The Fotonic sensor is one of the many instruments developed recently that make use of fiber-optic techniques. Translational velocity cannot be measured directly and therefore must be calculated indirectly by other means. The only class of device available for measuring acceleration is the accelerometer. Vibrations are very commonly encountered in machinery operation, and therefore measurement of the accelerations associated with such vibrations is extremely important in industrial environments. The peak accelerations involved in such vibrations can be of 100g or greater in magnitude, while both the frequency of oscillation and the magnitude of displacements from the equilibrium position in vibrations have a tendency to vary randomly. It is apparent that the intensity of vibration can be measured in terms of either displacement, velocity, or acceleration. Acceleration is clearly the best parameter to measure at high frequencies. Shock describes a type of motion where a moving body is brought suddenly to rest, often because of a collision.