SDVB20Z is mainly used to monitor the seam of the concrete surface, rock and building constructions. It is a customized style . A basic LVDT comprises one primary coil, two secondary coils, and a movable
core. The coils are wound onto a tubular coil form, the interior of which is called the bore. Communication between the moving and stationary parts of the sensor is achieved by means of inductive coupling. Therefore, any number of position changes can be made without incurring wear to the transducer parts.
The core is a magnetically permeable material, usually a nickel–iron alloy. When the core is centered on the primary and thus equally spaced relative to the two secondaries, the voltage induced into each of the secondaries is approximately equal.
The LVDT is a popular choice for high-reliability military applications. They are often used as the position feedback sensor in the actuator for control surfaces in airplanes. LVDT gauge heads are used successfully throughout industry on the production floor as well as in quality assurance. An array of LVDT gauge heads can be assembled to a template of an automobile door, for example. Samples are taken from the production line and placed against the template. Deviations from the standard profile are measured and used to determine if the tool making the door panels needs adjustment or reworking to keep the finished parts within the allowed tolerances. Incoming inspection tools use LVDTs to measure critical dimensions and read them into a computer that compares the data against the accepted tol-
erances. The gauge head of Figure 6.10 is a configuration often used in this way. There is a resistance-welding tool on the market that uses an LVDT to measure the submicron motion that occurs in the mating parts as the welding progresses (this measurement is called the weld set-down). LVDTs have been used as components in many other products, including pressure transducers and valve positioners for process control.