LVDT Youre expected to learn Linear Variable Differential

LVDT • You’re expected to learn – Linear Variable Differential Transformer (LVDT) • Architecture • Diagram • Application 1

LVDT-Inductive T A reliable and accurate sensing device that converts linear position or motion to a proportional electrical output. 2

LVDT The cross sectional view of the DC LVDT at left shows the built-in signal conditioning electronics module. The module is secured with a potting compound that is not shown in this drawing 3

Applications of LVDTs 4

LVDT Among the advantages of LVDT are as follows: • • It produces a higher output voltages for small changes in core position. Low cost Solid and robust -capable of working in a wide variety of environments. No permanent damage to the LVDT if measurements exceed the designed range. 5

LVDT Primary Secondary An inductor is basically a coil of wire over a “core” (usually ferrous) It responds to electric or magnetic fields A transformer is made of at least two coils wound over the core: one is primary and another is secondary Inductors and tranformers work only for ac signals 6

EXAMPLES OF LVDT APPLICATION 7

LVDT Operation Windings are connected “series opposing” polarities of V 1 and V 2 oppose each other if we trace through the circuit from terminal A to B. If the core at the center, V 1=V 2, Vo=0 When the core is away from center toward S 1, V 1 is greater than V 2 and the output voltage Vo will have the polarity V 1. When the core is away from center toward S 2, V 2 is greater than V 1 and the output voltage Vo will have the polarity V 2. 8

LVDT Operation That is, the output ac voltage inverts as the core passes the center position The farther the core moves from center, the greater the difference in value between V 1 and V 2, consequently the greater the value of Vo. Thus, the amplitude of Vo is a function of the distance the core has moved, and the polarity or phase indicates which direction is has moved. If the core is attached to a moving object, the LVDT output voltage can be a measure of the position of the object. 9

LVDT Operation 10

Example An ac LVDT has the following data; input 6. 3 V, output 5. 2 V, range ± 0. 50 cm. Determine: a) Plot of output voltage versus core position for a core movement going from +0. 45 cm to -0. 03 cm? b) The output voltage when the core is -0. 35 cm from the center? c) The core movement from center when the output voltage is -3 V? d) The plot of core position versus output voltages varying from +4 V to -2. 5 V. 11

Student’s activity for next class • Based on each measurement, I expect you to gather all the information in the following order – – – Type sensors Architecture Operation Application Diagram • You will need to prepare study materials/notes based on the information above • I will collect them by the end of next class (soft copy) 12