What are the commonly used generator sensors?
A sensor that converts the rotational speed of a rotating object into an electrical output. The speed sensor is an indirect measuring device, which can be manufactured by mechanical, electrical, magnetic, optical and hybrid methods. According to the different signal forms, the speed sensor can be divided into analog type and digital type. The output signal value of the former is a linear function of the speed, and the output signal frequency of the latter is proportional to the speed, or its signal peak interval is inversely proportional to the speed. The reason for the wide variety and wide application of speed sensors is that various motors are widely used in automatic control systems and automatic instruments. In many cases, there are strict requirements for accurate measurement of low speed (such as less than one revolution per hour), high speed (such as hundreds of thousands of revolutions per minute), stable speed (such as the error is only a few parts per ten thousand) and instantaneous speed. The commonly used speed sensors include photoelectric, capacitive, variable reluctance and tachogenerator.
The photoelectric speed sensor is divided into projection type and reflection type. The reading plate and the measuring plate of the projection photoelectric speed sensor have the same clearance. The measuring disk rotates with the measured object, and the light projected from the light source to the photosensitive element (see photoelectric sensor) will undergo a light and dark change each time it rotates through the gap, and the photosensitive element outputs a current pulse signal. The reflective photoelectric sensor is equipped with a reflection mark on the measured axis, and the light emitted by the light source is incident to the measured axis through the lens and translucent film. When the rotation axis rotates, the reflectivity of the reflection mark to the projection spot will change. When the reflectivity increases, the reflected light is projected onto the photosensitive element through the lens, and then a pulse signal is sent; When the reflectivity decreases, the sensor has no signal. The rotation speed of the shaft can be measured by counting signals within a certain time.
The variable reluctance speed sensor belongs to the variable reluctance sensor. Three basic types of variable reluctance sensors, inductive sensors, transformer sensors and eddy current sensors can be made into speed sensors. Inductive speed sensors are widely used. It uses the change of magnetic flux to generate induced potential. Its potential depends on the rate of change of magnetic flux. This type of sensor can be divided into open magnetic circuit type and closed magnetic circuit type according to its structure. The open magnetic circuit speed sensor has simple structure and small output signal, and is not suitable for use in places with serious vibration. The closed magnetic circuit speed sensor is composed of an outer gear, an inner gear, a coil and a permanent magnet installed on the rotating shaft. The internal and external gears have the same number of teeth. When the rotating shaft is connected to the measured shaft and rotates together, the magnetic resistance changes due to the relative movement of the internal gear and the external gear, and the AC induction potential is generated in the coil. The corresponding speed can be measured by measuring the electric potential.
