How does an LVDT measure displacement using the differential voltage induced in a transformer coil?
1 Answer
An LVDT (Linear Variable Differential Transformer) is a type of sensor used to measure linear displacement or position. It operates on the principle of electromagnetic induction to measure the displacement of an object relative to the sensor.
The basic components of an LVDT include a primary coil (also called the excitation coil) and two secondary coils wound on a cylindrical core. The primary coil is supplied with an alternating current (AC) voltage, which generates a magnetic field around the core.
When there is no displacement, the core is centered within the LVDT, and an equal amount of magnetic flux links the two secondary coils. In this central or null position, the output voltage induced in both secondary coils is equal and opposite, resulting in a net differential voltage of zero across the secondary output terminals.
However, when an object is displaced relative to the LVDT, the position of the core changes. Let's assume the core is moved to the right:
Core Displacement to the Right: When the core moves to the right, it becomes closer to one of the secondary coils (let's call it "Secondary A") and farther from the other secondary coil (let's call it "Secondary B").
Change in Induced Voltage: Due to this displacement, the amount of magnetic flux linking the Secondary A coil increases, while the amount of magnetic flux linking the Secondary B coil decreases. This change in magnetic coupling results in different induced voltages in the two secondary coils.
Differential Output Voltage: The net result is that the voltage induced in Secondary A increases, while the voltage induced in Secondary B decreases. This leads to a differential voltage across the secondary output terminals, which is proportional to the magnitude and direction of the displacement.
Signal Conditioning: The differential voltage output is then processed by electronic circuitry, typically through amplification and filtering, to obtain a more robust and usable measurement of the displacement. The LVDT output can be either analog (varying voltage) or digital (digitally encoded) based on the signal conditioning used.
The key advantage of using an LVDT is its high sensitivity and accuracy in measuring linear displacement, making it a popular choice in various industrial, automotive, and aerospace applications where precise position sensing is required.
The basic components of an LVDT include a primary coil (also called the excitation coil) and two secondary coils wound on a cylindrical core. The primary coil is supplied with an alternating current (AC) voltage, which generates a magnetic field around the core.
When there is no displacement, the core is centered within the LVDT, and an equal amount of magnetic flux links the two secondary coils. In this central or null position, the output voltage induced in both secondary coils is equal and opposite, resulting in a net differential voltage of zero across the secondary output terminals.
However, when an object is displaced relative to the LVDT, the position of the core changes. Let's assume the core is moved to the right:
Core Displacement to the Right: When the core moves to the right, it becomes closer to one of the secondary coils (let's call it "Secondary A") and farther from the other secondary coil (let's call it "Secondary B").
Change in Induced Voltage: Due to this displacement, the amount of magnetic flux linking the Secondary A coil increases, while the amount of magnetic flux linking the Secondary B coil decreases. This change in magnetic coupling results in different induced voltages in the two secondary coils.
Differential Output Voltage: The net result is that the voltage induced in Secondary A increases, while the voltage induced in Secondary B decreases. This leads to a differential voltage across the secondary output terminals, which is proportional to the magnitude and direction of the displacement.
Signal Conditioning: The differential voltage output is then processed by electronic circuitry, typically through amplification and filtering, to obtain a more robust and usable measurement of the displacement. The LVDT output can be either analog (varying voltage) or digital (digitally encoded) based on the signal conditioning used.
The key advantage of using an LVDT is its high sensitivity and accuracy in measuring linear displacement, making it a popular choice in various industrial, automotive, and aerospace applications where precise position sensing is required.