What Is A LVDT?

Simply put, the Linear Variable Differential Transformer (LVDT) is an electro mechanical sensor that converts mechanical motion into variable electric current. The LVDT specifically converts rectilinear motion into electrical signals, which makes it apt for use in mechanical motion sensors or automatic control systems. The voltage generated by the linear motion of a mechanical system is directly proportional to the force of the movement.

How does an LVDT work?

The physical construction of an LVDT is effectively a shaft made of magnetically conductive material that fits snugly inside a hollow metallic cylindrical tube. The shaft, also known as the push rod, is small enough to move back and forth within the long axis of the metallic tube. The mechanical motion of the system is connected to the shaft, where the linear motion of the shaft generates electricity at the hollow tube/ electrical coil set up around the same.

A LVDT is often considered to be a mini transformer with one primary winding and two symmetrical secondary coils. The single armature rod is free to be displaced off center every time the connecting component shifts its position.

The movement of the core disturbs the linkage between the primary and secondary coils, which in turn induces voltages. This voltage results in a current flowing through the system, which then acts as a measuring signal. Since the internal core does not touch the hollow tube, the readouts are highly reliable and additional movements of the systems does not impact the read outs. This sliding core mechanism also ensures that the sensor can be set up in a sealed environment to minimize electromagnetic interference. The versatility of the LVDT assures its place in a variety of industries such as aerospace industries, manufacturing industries, and more.

Types of LVDT

LVDTs are generally divided based on the relative current that they are required to measure, such as C-in, AC-out, DC-in, DC out; or they are distinguished based on the resonant frequencies of the coils. LVDTs are also categorized based on their armature mechanism, namely-

* Unguided armatures that are attached to the mechanical specimen that needs to be measured, and are freely movable within the body of the LVDT. The external hollow tube is supported separately. This design allows for virtually no wear, and it does not limit the resolution of the data that needs to be measured.

* Captive armatures have their action restricted by the flow friction assembly, which allows for guided and long-range movements. This set up prevents any misalignment and thus offers precise measurements.

* Force extended armatures use an internal spring, a pneumatic force cylinder, or an electrical motor to achieve the linear to and fro motion within the cylinder. Such types of LVDTs are suitable for use in slow applications where the connection between the armature and the mechanical equipment is of little importance.

LVDT Sensors are just one of many sensor types dealt at Positek Limited. Do visit their website to know more about the Company’s services and full range of products.

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