Since the development of LVDTs more than half a century ago, these sensors continue to be a preferred sensing technology used in many industrial applications. Earlier uses of linear transducers were in laboratory equipment. Today, linear transducers remain a reliable option for taking measurements in laboratory applications. But in addition to laboratory measurements, LVDTs have further gained widespread use in process control applications and monitoring. The primary working principle of a linear variable differential transducer makes it perfect for measuring high-speed displacement. In addition to this, there are many other advantages to using a linear sensor over other sensing technologies.
Construction and working principle
An LVDT is an electromechanical transducer consisting of a cylinder with three free-moving coils around a core. Although a linear sensor is an electromechanical device, it requires a consistent supply of AC power to perform. The primary winding coil gets amplified by the AC power supply which produces magnetic flux. The magnetic flux generated is coupled with the secondary winding coil moving in an opposite direction.
Advantages of using an LVDT
There are many reasons why LVDTs are popular in various industrial applications. These benefits make LVDTs superior to other sensors used today.
• Contactless operation. One key advantage of an LDVT is its frictionless operation. The core of an LVDT does not have contact with the winding coils during its normal function. The absence of friction means the sensor is resistant to the effects of vibration. LVDTs perform with consistent accuracy and high resolution even when applied in hazardous conditions.
• Limitless resolution. The electromagnetic coupling of coils within the linear transducer allows it to measure an infinite degree of slight core displacement. The only limitation to the ability of an LVDT to measure endless resolution is the display’s output resolution and signal conditioning.
• Increased performance and mechanical life. Since a linear transducer uses non-contact technology, the internal parts of the sensor will not rub together or wear out. Improved reliability and mechanical life are essential when a linear sensor finds application in harsh industrial applications. Some examples that prefer using LVDTs include communication satellites, aircraft, aerospace vehicles, and nuclear reactors.
• Damage resistance. An LVDT is not vulnerable to the effects of overload in position input.
• Environmental robustness. LVDTs can perform in rugged environments. Environmental sealing is added to enhance the capability of an LVDT to function when applied in situations exposed to moisture and humidity. Recent experiments in using metal alloys produce linear transducers capable of working in extreme heat or cold weather conditions. These new materials also produced sensors that will not corrode when exposed to highly oxidised situations. That is the primary reason why the use of linear transducers is common in oil and gas exploration, as well as underwater conditions.
LVDTs remain one of the most robust devices used in industrial machines. With new developments and advancements in engineering technology, LVDTs will find their way into more modern applications such as wireless technology and consumer electronics.
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