What is LVDT Displacement Sensor
A Linear Variable Differential Transformer (LVDT) displacement sensor is a highly accurate and reliable device used to measure linear displacement or position. The LVDT is a type of electromechanical transducer that converts mechanical motion into an electrical signal. It is widely used in various industries and applications, including manufacturing, aerospace, automotive, and robotics, where precise and repeatable measurements are critical.
In this article, we will explore the features, working principles, advantages and disadvantages of LVDT displacement sensors. Whether you are an engineer, a researcher, or an enthusiast in the field of position sensing, understanding the capabilities and benefits of LVDT displacement sensors will empower you to select the most suitable sensor for your specific measurement needs.
What is LVDT Displacement Sensor
An LVDT (Linear Variable Differential Transformer) displacement sensor is a type of electromechanical transducer used to measure linear displacement or position.
Features of LVDT Displacement Sensor
Here are the features of lvdt displacement sensor,
LVDT Displacement Sensor Structure
The structure of an LVDT (Linear Variable Differential Transformer) displacement sensor consists of three main components: a primary coil, a secondary coil assembly, and a movable core. Let’s explore each component in detail:
Primary Coil:
The primary coil is typically a cylindrical winding made of insulated wire.
It is the input component of the LVDT and is excited by an alternating current (AC) power source.
The primary coil generates a magnetic field in the surrounding space when the AC current passes through it.
The magnetic field serves as the reference for the displacement measurement.
Secondary Coil Assembly:
The secondary coil assembly consists of two secondary coils symmetrically positioned on either side of the primary coil.
The secondary coils are also wound with insulated wire and connected in a differential configuration.
They are typically constructed as cylindrical windings with a center hole to accommodate the movable core.
The purpose of the secondary coils is to detect the changes in the magnetic field induced by the movement of the core.
Movable Core:
The movable core is a cylindrical rod made of a ferromagnetic material, such as nickel-iron or ferrite.
It is placed within the center of the primary and secondary coils.
The core is mechanically linked to the object or component whose displacement is being measured.
As the object moves, the core also moves linearly along the axis of the LVDT.
How Does LVDT Displacement Sensor Work
An LVDT (Linear Variable Differential Transformer) displacement sensor works based on the principle of electromagnetic induction. Here’s a step-by-step explanation of how an LVDT displacement sensor operates:
Step1. Excitation: An alternating current (AC) is applied to the primary coil of the LVDT. The primary coil generates an alternating magnetic field around it.
Step2. Magnetic Field Interaction: The alternating magnetic field induces a voltage in the two secondary coils of the LVDT. The induced voltages are equal when the movable core is in its null or centered position.
Step3. Displacement: When the object or component being measured undergoes linear displacement, the movable core also moves along the axis of the LVDT. This movement changes the magnetic coupling between the primary coil and the secondary coils.
Step4. Differential Output: As the movable core shifts, the magnetic coupling between the primary and secondary coils becomes imbalanced. This causes the induced voltages in the secondary coils to vary in magnitude and phase. The output voltage from the LVDT is obtained by taking the difference between the voltages of the two secondary coils, resulting in a differential output signal.
Step5. Proportional Output: The output voltage of the LVDT is directly proportional to the displacement of the movable core and, consequently, the measured displacement of the object. As the core moves further away from the null position, the output voltage increases or decreases proportionally depending on the direction of displacement.
Step6. Signal Conditioning: The AC output voltage from the LVDT is typically conditioned and amplified to suit the measurement or control system requirements. This may involve converting the AC signal to a direct current (DC) voltage or further processing the signal for filtering, amplification, or digitization.
Step7. Measurement or Control: The conditioned output signal from the LVDT can be used for various applications. It can be measured using analog or digital instruments to determine the displacement of the object accurately. It can also be utilized in control systems for feedback, position control, or automation purposes.
Advantages and Disadvantages of LVDT Displacement Sensor
Advantages of LVDT Displacement Sensors:
High Accuracy: LVDT displacement sensors offer excellent accuracy, providing precise and reliable measurements of linear displacements.
Wide Measurement Range: LVDTs can measure a wide range of displacements, from fractions of a millimeter to several inches or more, making them versatile for various applications.
Linearity: LVDTs exhibit a linear relationship between the position of the core and the output voltage, allowing for easy and predictable interpretation of the measured displacements.
High Resolution: LVDT displacement sensors can provide high resolution, enabling precise measurement of small position changes or variations.
Long-Term Stability: LVDTs typically exhibit excellent long-term stability, maintaining their calibration and measurement accuracy over extended periods of use.
Insensitivity to External Factors: LVDTs are relatively immune to external factors such as temperature, humidity, and electromagnetic interference, ensuring reliable operation in diverse environments.
Non-Contact Operation: LVDTs operate without physical contact between the core and the sensor coils, resulting in low friction, minimal wear, and increased lifespan.
Disadvantages of LVDT Displacement Sensors:
Environmental Limitations: While LVDTs are relatively resilient, extreme environmental conditions such as high temperatures, corrosive substances, or exposure to liquids can affect their performance.
Complex Signal Conditioning: The output signal of an LVDT is typically an alternating current (AC), requiring additional signal conditioning electronics to convert it into a usable form, such as a direct current (DC) voltage or digital signal.
Cost: LVDT displacement sensors can be more expensive compared to other types of displacement sensors, primarily due to their precision and complex design.
Size and Form Factor: LVDTs can be relatively larger in size, which may limit their integration in space-constrained applications.
Sensitivity to Vibrations: Vibrations and mechanical shocks can introduce noise and affect the accuracy of LVDT measurements, requiring proper isolation or damping measures.
Power Requirements: LVDTs require an alternating current (AC) power supply for excitation, which may pose limitations in certain applications where DC power is preferred.
Conclusion
In conclusion, LVDT displacement sensors offer high precision, reliability, and versatility in measuring linear displacement or position. Their robust construction, wide operating range, and immunity to external disturbances make them ideal for demanding industrial applications. When choosing an LVDT displacement sensor, consider factors such as measurement range, accuracy, environmental conditions, and mounting options to ensure optimal performance.
Stay updated with the latest advancements in position sensing technology, explore datasheets and technical documentation, and make informed choices when incorporating LVDT displacement sensors into your projects. Embrace the accuracy and reliability offered by these sensors and unlock new possibilities in position measurement and control.
