The lvdt displacement sensor is one of the widely used sensors in displacement measurement and plays an important role in many applications. What is the lvdt sensor? What are its characteristics? Let's take a look at it.
Lvdt displacement sensor works
The LVDT (differential transformer) displacement sensor is an electromagnetic induction principle. Unlike a conventional power transformer, the LVDT is a measuring component for weak magnetic coupling of an open magnetic circuit. The structure of the LVDT consists of a core, an armature, a primary coil, and a secondary coil. The primary coil and the secondary coil are distributed on the bobbin, and the coil has a freely movable rod-shaped armature inside. Using a different wire diameter enameled wire, a set of primary coils are wound on the skeleton, and two sets of secondary coils, the working mode of which depends on the movement of the magnetic core in the coil bobbin, when the primary coil supplies an alternating voltage of a certain frequency, iron The movement of the core in the coil changes the magnetic field distribution of the space, thereby changing the amount of mutual inductance between the primary and secondary coils, and the secondary coil generates an induced electromotive force. As the position of the core is different, the mutual inductance is also different, and the secondary generation is generated. The induced electromotive force is also different, so that the displacement of the iron core becomes 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 does not contact the coil during the movement, and there is no friction loss. At the same time, the skeleton and the wrapped enameled wire are solidified into one whole by using an excellent production process. There will be broken lines, cracking and other faults, plus other optimization designs, so the service life of the sensor can theoretically be unlimited. According to a foreign institution, the MTBF of such a sensor can reach 300,000 hours, in actual normal use. It can last for decades, and its final failure is often determined by human or the life of the transmitter circuit components.
2, diverse environmental adaptability: LVDT is one of the few displacement sensors that can be used in a variety of harsh environments. Sensors that are sealed by special means can be protected from moisture and salt spray, and can be placed in pressurized liquids and gases. In a closed container, even in some corrosive environments, it is not sensitive to nuclear radiation electromagnetic radiation interference, can resist vibration, has a wide operating temperature range of -25 ° C ~ 85 ° C and meets the national military standard -55 ° C ~ 125 ° C Operating temperature. The electromechanical split displacement sensor can be used at 200 ° C alone.
3, fast response: based on the realization of non-contact measurement, for the impact vibration measurement of some fast moving objects, such sensors can provide a wide frequency response.
4, high linearity: through the continuous development of the coil winding method, the linearity of the LVDT displacement sensor has been significantly improved.
5. High resolution: Any tiny core movement determined by the principle of electromagnetic induction will change the induced electromotive force of the secondary coil in the magnetic field, making the LVDT displacement sensor theoretically have infinite resolution. As design, process and electronic components continue to improve performance.
6. Low noise: For the rebound type displacement sensor, the peak-to-peak voltage of ripple and interference noise is only 0.2~1.5mVp-p when the rated displacement output signal is 10.0000V or 5.0000V.
7. Low temperature drift: The temperature coefficient of general-purpose small and medium-range products is ±0.001%/°C～±0.01%/°C. FS.
8. Start-up drift is small: When the power is turned on (on), the displacement reading can be basically stabilized quickly, without long-time warm-up, and the time drift is small.
9, no zero residual voltage: due to the use of advanced detection circuit, to avoid the existence of zero residual voltage.
10, good repeatability: repeatability can reach a few micrometers or even smaller.
11. Wide range coverage: LVDT displacement sensors can achieve high linearity accuracy over a wide range.
12, strong carrying capacity: a measuring instrument can work with 1-30 LVDT at the same time
13. Low fault: This refers to various measures designed for human negligence or misoperation under abnormal use to avoid damage to the sensor.
14, low power consumption: in dual power supply, output voltage signal, supply current <10mA
15. Variety of input and output: It can input single or dual power supply, its voltage value is from 5V to 24V or ±5V to ±15V; output signal voltage is 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).
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