Linear Variable Differential Transformer (LVDT)

LVDT is a type of transformer.

LVDT is a type of inductive transducer.

LVDT contains electronic components inside it.

LVDT measures physical quantities directly without the need for a primary transducer.

LVDT consists of a primary coil wound over the whole length of a ferromagnetic cylinder.

LVDT's electrical output is obtained due to the difference in primary voltages.

The primary winding is connected to a DC source, not an AC source.

The iron core inside the former is generally of low permeability.

The LVDT is placed inside an aluminum housing for electrostatic and electromagnetic shielding.

The amplitude of the differential output voltage (Va-Vb) is not proportional to the core position.

The phase shift of (Va-Vb) with reference to the excitation determines the direction towards the zero position.

The null position is defined as the core position where the phase shift of the (Va-Vb) differential output is 180 degrees.

The differential output between the two secondary outputs (Va-Vb) when the core is at null position is called the Null Voltage.

The residual voltage, known as quadrature voltage, is high due to the simple nature of the LVDT electrical model.

AC excitation of 20-25 Volts at a frequency of 40-350Hz is applied to the primary winding.

The working principle of LVDT is based on Faraday's law of electromagnetic induction.