LVDT (linear variable differential transducer)

What is LVDT?

An LVDT (linear variable differential transformer) is an electromechanical sensor used to convert mechanical motion or vibration into a variable electrical current, voltage or electric signals, and vice versa. 

Used to measure the displacement-

As the primary is connected to an AC source so alternating current and voltages are produced in the secondary of the LVDT. The output in secondary S₁ is e₁ and in the secondary S₂ is e₂. So the differential output is null at the midpoint of the core, known as a null point.

if the core approaches the S1 than to S2, more flux is coupled to S1 and less to S2, so the induced voltage e₁ is increased while e2 is decreased, resulting in the differential voltage (e₁ - e2). and vice versa.

The principle of Operation and Working-

• it is a mutual inductance device that consists of one primary and two secondary coils.

• Both secondary coils have equal no. of turns and can be placed on either side of the coil.

• I/P is given to primary windings. 

• The secondary coil 1 and coil 2 are connected in series such that the o/p voltage taken across secondary windings is the difference in EMF induce in each secondary windings. i.e.

• The movable core of high permeability signal producer proportional to displacement changing mutual inductance b/w the secondary coil.

• When the core is in the middle position create an equal sinusoidal voltage in both secondary coils. this voltage cancels each other and produces a null voltage.

• On the displacement of a core to either side of the center position, the net voltage across the secondary coil increases linearly. the o/p voltage loses its linear relationship with i/p displacement.

• Thus it creates a voltage difference which displays on the device