Displacement sensor, also known as linear sensor, is a linear device that belongs to metal induction. There are many kinds of displacement sensors and different principles.

Classification of displacement sensors

According to different classification methods, there are many kinds of sensors for measuring displacement. The principle and application range of each sensor are different. The following are some common sensor types.
Pull rope displacement sensor: determine the displacement of the measured object by measuring the length change of the pull rope.
Grating displacement sensor: the grating and readout are used to detect the scratches on the grating to determine the displacement.
Vibrating wire displacement sensor: measure displacement by measuring the vibration of fixed vibrating wire.
Inductive displacement sensor: change the inductance by using a movable iron core to determine the displacement.
Piezoelectric displacement sensor: measure displacement by using the piezoelectric effect of piezoelectric materials.
Volumetric displacement sensor: measure displacement by measuring the volume change of liquid or gas in the container.
Capacitive displacement sensor: measure displacement by using the capacitance change between two metal plates.
Inductive displacement sensor: measure displacement by using the principle of inductive current.

Different principles of displacement sensor

As a kind of sensor for measuring the displacement of objects, the working principle of displacement sensor is based on different physical phenomena and technical principles, and the displacement sensor for different purposes has different principles. The following are the working principles of some common displacement sensors:
1. Resistance displacement sensor: Resistance displacement sensor is a sensor based on resistance change. Its structure usually includes two electrodes and a piece of resistive material. When the measured object is displaced, the length or cross-sectional area of the resistive material will change, thus changing the resistance value. The sensor converts the resistance value into a voltage or current signal to measure the displacement of the measured object. Use the change of resistance value caused by material deformation to measure displacement, which is often used to measure small displacement and micro deformation
2. Capacitive displacement sensor: Capacitive displacement sensor is a sensor based on capacitance change. Its structure usually includes a positioning electrode and a moving electrode. When the measured object is displaced, the position of the moving electrode will change, thus changing the capacitance value. The sensor converts the capacitance value into a voltage or current signal to measure the displacement of the measured object.
3. Inductive displacement sensor: Inductive displacement sensor is a sensor based on inductance change. Its structure usually includes a movable iron core and a coil. When the measured object is displaced, the position of the iron core will change, thus changing the inductance value in the coil. The sensor converts the inductance value into voltage or current signal to measure the displacement of the measured object.
4. Vibrating wire displacement sensor: Vibrating wire displacement sensor is a sensor that measures displacement based on the deformation of vibrating wire. Its structure usually consists of a fixed vibrating string and a mass block with a moving part. When the measured object is displaced, the mass will vibrate under the action of the vibrating string, and the amplitude and frequency of the vibrating string will change. The sensor converts the amplitude and frequency into electrical signals to measure the displacement of the measured object.
5. Inductive displacement sensor: Inductive displacement sensor is a sensor based on induction principle. Its structure usually includes an iron core and a coil. When the measured object is displaced, the position of the iron core will change, thus changing the magnetic field strength in the coil. The sensor can measure the displacement of the measured object by converting the change of magnetic field intensity into voltage or current signal. It is generally divided into linear inductive displacement sensor and rotary inductive displacement sensor.
6. Photoelectric displacement sensor: use the principle of photoelectric sensor to measure displacement, including photoelectric encoder, laser displacement sensor, linear displacement sensor, etc.
7. Rope displacement sensor: uses the rope principle to measure the displacement, which is often used for the measurement of large machinery and equipment.
8. Volumetric displacement sensor: It is used to measure the volume of liquid or gas based on the principle that the internal volume of the measured object changes with displacement.
9. Ultrasonic displacement sensor: It is used to measure the displacement of a large range by using the principle that the propagation speed of ultrasonic wave in the measured object changes with the displacement.
The above are some common types of displacement sensors and the principles of each classification. Different types of displacement sensors are suitable for different applications and measuring ranges. When selecting a suitable displacement sensor, it is necessary to comprehensively consider the factors such as the measured physical quantity, working environment and accuracy requirements.