LVDT displacement sensor is one of the widely used sensors in displacement measurement, occupying an important position in many application fields. What is LVDT sensor? What are its characteristics? Let's introduce everyone below.
Working principle of LVDT displacement sensor
LVDT (differential transformer) displacement sensor is based on the principle of electromagnetic induction. Like traditional power transformers, LVDT is a measuring element with open magnetic circuit weak magnetic coupling. The structure of LVDT consists of an iron core, an armature, a primary coil, and a secondary coil. The primary and secondary coils are distributed on the coil skeleton, and there is a freely movable rod-shaped armature inside the coil. Using enameled wire of the same diameter, a set of primary coils and two sets of secondary coils are wound on the skeleton. The working mode depends on the movement of the magnetic core inside the coil skeleton. When the coil is supplied with a constant frequency alternating voltage, the movement of the iron core inside the coil changes the spatial magnetic field distribution, thereby changing the mutual inductance between the primary and secondary coils. The secondary coil generates induced electromotive force, and as the position of the iron core is the same, the mutual inductance is also the same, and the induced electromotive force generated by the secondary coil is the same. In this way, the displacement of the iron core is converted into a voltage signal output.
Main features of LVDT displacement sensor:
1. Long service life: Due to the gap between the iron core and the inner wall of the coil, the iron core comes into contact with the coil during movement without frictional loss; At the same time, using excellent production technology to solidify the skeleton and the wrapped enamel wire into a whole can cause faults such as breakage and cracking. With other optimized designs, the service life of the sensor can theoretically be unlimited. According to a test conducted by an external organization, the MTBF of such sensors can reach 300000 hours, and in actual normal use, it can reach ten years. The ultimate failure is often caused by human factors or determined by the lifespan of the transmitter circuit components.
2. Diverse environmental adaptability: LVDT is one of the few displacement sensors that can be applied in various harsh environments. Sensors that are sealed in a special way can prevent moisture and salt spray, and can be placed in pressurized liquids or gas sealed containers, which is more sensitive to nuclear radiation electromagnetic interference than some corrosive environments. They can resist vibration and have a wide working temperature range of -25 ℃ to 85 ℃ and meet the standard of -55 ℃ to 125 ℃. The displacement sensor of electromechanical separation can work at 200 ℃ when used alone.
3. Fast response speed: Based on non-contact measurement, this type of sensor can provide a wide frequency response for measuring the impact and vibration of certain fast-moving objects.
4. High linearity: The linearity of LVDT displacement sensors has been significantly improved through the coil winding method developed.
5. High resolution: Any small movement of the iron core determined by the principle of electromagnetic induction will change the induced electromotive force of the secondary coil in the magnetic field, making LVDT displacement sensors theoretically have infinite resolution. With the improvement of design, process, and electronic component performance.
6. Low noise: For rebound displacement sensors, when the rated displacement output signal is 10.0000V or 5.0000V, the peak to peak voltage of ripple and interference noise is only 0.2-1.5mVp-p.
7. Low temperature drift: The temperature range of universal small and medium range products is between ± 0.001%/℃ and ± 0.01%/℃. FS。
8. Small initial drift: When the power is turned on (turned on), the displacement reading can quickly stabilize without the need for prolonged preheating, resulting in small time drift.
9. Zero point residual voltage free: Due to the use of a detection circuit, the existence of zero point residual voltage is avoided.
10. Good repeatability: The repeatability accuracy can reach a few micrometers or even smaller.
11. Wide range coverage: LVDT displacement sensors can achieve high linear accuracy within a wide range of ranges.
12. Strong load capacity: One measuring instrument can work with 1-30 LVDTs simultaneously
13. Low failure: This refers to various measures designed to prevent sensor damage due to human negligence or misoperation during abnormal use.
14. Low power consumption: When powered by dual sources and outputting voltage signals, the supply current is less than 10mA
15. Diversity of input and output: It can input single or dual power supplies, with voltage values ranging from 5V to 24V or ± 5V to ± 15V; output signal voltage ranging from 20mV to 10V or ± 20mV to ± 10V; output signal current; 4-20mA or 0-10mA, and has good constant current characteristics. Output signal frequency: 0-10000Hz (TTL level square wave).