3 Exploring Sensing Technologies: LVDT, Angularity Sensors, Optical Tachometers, Toothed Rotor Tachometers, DC Tachometers, and Proximity Sensors
Introduction
Sensors play an important role in the field of automation in detecting physical phenomena.This reading material aims to provide insights into several sensing devices, including the Linear Variable Differential Transformer (LVDT), Angularity Sensors, Optical Tachometers, Toothed Rotor Tachometers, DC Tachometers, and Proximity Sensors.
Linear Variable Differential Transformer (LVDT)
The LVDT is a precision displacement sensor that converts linear motion into an electrical signal. Its design involves a movable core and three coils that enable precise measurements of linear displacement.
How it Works: As the core moves within the transformer, it induces voltages in the coils. The resulting signals are then processed to determine the displacement of the core. LVDTs are known for their accuracy, reliability, and ability to operate in harsh environments. Figure. 1 shows that if the iron core is exactly in the center, the voltages induced on the secondaries by the primary will be equal and when the core is moved a little to the right. In that case there is more coupling to secondary 2, so its voltage is higher, while secondary 1 is lower.
Figure 1: Linear Variable Differential Transformer (Adapted from “Modern control technology: components and systems” by Kilian, Christopher T. , West Publishing Co., 1996.)
Angularity Sensors
Angularity sensors measure the angular displacement of an object. These sensors find applications in robotics, automotive systems, and machinery where monitoring rotation is critical.
Working Principle: Angularity sensors use various technologies, such as Hall Effect or optical encoding, to detect and measure angular movement. They are crucial for applications where knowing the exact angle of rotation is essential.
Optical Tachometers
Optical tachometers are devices that measure the rotational speed of an object. They use optical sensors to detect markings or reflective surfaces on a rotating object.
Figure 2: Optical Tachometer (Adapted from “Modern control technology: components and systems” by Kilian, Christopher T. , West Publishing Co., 1996.)
Operation: As the object rotates, the optical sensor detects changes in light intensity or reflections, converting them into electrical signals. The frequency of these signals corresponds to the rotational speed of the object.
Toothed Rotor Tachometers
Purpose: Toothed rotor tachometers are specifically designed to measure the speed of rotating machinery. They utilize a toothed wheel attached to the rotating object.
Figure 3: Toothed-Rotor Tachometer (Adapted from “Modern control technology: components and systems” by Kilian, Christopher T. , West Publishing Co., 1996.)
Detection Method: As the teeth pass a sensor, electrical pulses are generated. The frequency of these pulses provides information about the rotational speed, making toothed rotor tachometers valuable in industrial applications.
DC Tachometers
DC tachometers are devices that measure the speed of a rotating object by generating a direct current (DC) voltage proportional to the rotational speed.
Principle of Operation: They often use a permanent magnet and a rotating coil or a magnetic field variation to produce a voltage proportional to the rotational speed. DC tachometers find applications in control systems and motor speed monitoring.
Proximity Sensors
Proximity sensors detect the presence or absence of an object within a certain range without physical contact. They play a crucial role in automation, security, and manufacturing processes.
Working Mechanism: Proximity sensors use various technologies, including inductive, capacitive, ultrasonic, or optical methods. When an object enters the sensor’s range, it triggers a response, providing information about the object’s presence or position.
Deepen your understanding: Watch the accompanying lecture video to delve deeper into the concepts covered in the reading.