A Linear Variable Differential Transformer (LVDT) is a type of electromechanical sensor used to measure displacement or linear position. It is a highly accurate and reliable transducer that converts linear motion into an electrical signal. LVDTs are commonly used in various applications, such as industrial automation, robotics, aerospace, and automotive systems.
Here's how an LVDT measures displacement:
Basic Construction: An LVDT consists of three main components: a primary coil (also known as the excitation coil) and two secondary coils, wound on a cylindrical core made of a magnetically permeable material. The core is usually made of a non-magnetic, electrically conductive material, allowing it to move freely inside the coils.
Excitation: An alternating current (AC) is applied to the primary coil, creating an electromagnetic field around the core.
Null Position: When the core is centered within the coils, an equal voltage is induced in the two secondary coils. At this point, the output voltage across the secondary coils is ideally zero. This position is known as the null position.
Displacement Sensing: When an external force or displacement is applied to the LVDT, it moves the core from its null position. The amount of displacement determines how much of the core is within each secondary coil's field.
Differential Output: The displacement-induced change in the position of the core inside the coils causes an imbalance in the voltages induced in the secondary coils. This imbalance creates a differential AC voltage output between the two secondary coils. The amplitude and phase of this output signal are directly proportional to the core's position within the primary coil.
Signal Processing: The differential AC output is then converted to a DC voltage using a demodulator. The DC output voltage is proportional to the displacement or position of the core. Typically, this signal is further conditioned, amplified, and processed to make it suitable for various control and measurement applications.
Accuracy and Linearity: The accuracy and linearity of an LVDT depend on its design, the quality of the core and coils, and the precision of the signal conditioning electronics. High-quality LVDTs can achieve excellent accuracy and linearity over a wide range of displacements.
LVDTs are preferred for their non-contact operation, high precision, reliability, and ability to operate in harsh environments. They are commonly used in applications where accurate and repeatable linear position measurements are essential.