What are the Linear Variable Differential Transformers (LVDT)? Describe some applications of LVDT.

Linear Variable Differential Transformers (LVDT):

The linear variable differential transformer (LVDT) is a displacement sensor, which consists of a transformer with a single primary coil and two identical secondary coils connected in a seriesopposing manner.  An LVDT is operated based on the mutual inductance concept.

Some applications of LVDT include the following:

1. Weighing systems: LVDTs can be used to measure spring deformation in weighing systems. The measured displacement can be used to calculate the applied force based on the characteristics of the spring.  
2. Displacement sensing: An LVDT may be mounted externally in parallel with the cylinder, thus making the core assembly free to move with the piston rod, and allowing measurement of the displacement of a piston. 
3. Bill detector in ATMs: Using an LVDT, ATMs can detect the number of bills inserted. When bills pass, a motion signal is transferred to the LVDT core element and then a changing output signal is generated. As the bills pass between the rollers, the voltages vary according to the thickness of the bills.     

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