TABLE OF CONTENTS Displacement transducers are used to measure the physical distance between the sensor and a target. Since most displacement transducers can measure dynamic as well as static displacements they are often used to measure the vibration of a target. The range of displacements measured can range from a few micro inches, using laser-based transducers, to tens of feet, using cable-driven potentiometers. In some types, there must be physical contact between the target and some part of the transducer. Other transducers do not require any contact.
Linear displacement transducers measure the dimensional change that occurs on a straight line between the transducer and the target. Their relevant units of measurement include the inch and foot as well as the metric units of centimeter, millimeter, and micrometer. The measurement system has the usual components: a transducer, cabling, and a signal conditioner. The typical system produces a voltage output that is linearly proportional to the distance measured.
The Linear Variable Differential Transformer or LVDT consists of a movable magnetic rod that acts as a core element between the primary coil and two secondary coils that surround the rod. The LVDT's body is usually cylindrical, with the core moving in a central, tubular cavity that runs the length of the cylinder. The primary coil is wound around the tube at the center of the cylinder, while the secondary coils are wound around the tube at opposite ends of the...
