The Full Form of LVDT is‍ linear variable differential transformer.

An LVDT (linear variable differential transformer= is an electromechanical sensor used to convert mechanical motion or vibrations, specifically rectilinear motion, into a variable electrical current, voltage or electric signals, and the reverse. Actuating mechanisms used primarily for automatic control systems or as mechanical motion sensors in measurement technologies. The classification of electromechanical transducers includes conversion principles or types of output signals.

In short, a linear transducer provides voltage output quantity, related to the parameters being measured, for example, force, for simple signal conditioning. LVDT Sensor devices are sensitive to electromagnetic interference. Reduction of electrical resistance can be improved with shorter connection cables to eliminate significant errors. A linear displacement transducer requires three to four connection wires for power supply and output signal delivery.

Physically, the LVDT construction is a hollow metallic cylinder in which a shaft of smaller diameter moves freely back and forth along the cylinder’s long axis. The shaft, or pushrod, ends in a magnetically conductive core which must be within the cylinder, or coil assembly, when the device is operating.

In common practice, the pushrod is physically attached to the moveable object whose position is to be determined (the measurand), while the coil assembly is attached to a fixed reference point. Movement of the measurand moves the core within the coil assembly; this motion is measured electrically.

Conversion Principles:

• Electromagnetic
• Magnetoelectric
• Electrostatic

Output Signals:

• Analog and discrete output
• Digital

Evaluating Electromechanical Transducers:

• Static and dynamic qualities
• Sensitivity or transfer ratio – E=Δy / Δx or Δy is the change in output quantity y when input quantity x is changed by Δx
• Output signal—range of operating frequency
• Static error of conversion or of the signal