The photoelectric speed sensor works

The photoelectric speed sensor works The general principle is based on photoelectric transformation. If divided according to the structure, it can be divided into light-transmitting and reflective.

The transmissive speed sensor consists of a back plate with holes or notches, a light source and a photocell. When the disc rotates with the axis being measured, light can only be directed onto the photocell by holes or notches. When the photocell is illuminated, its reverse resistance is very low, thus sending an electric pulse signal to the mountain. When the light source is blocked by the disk, the photoelectric cell has a large reverse resistance, and there is no signal output at the output end. In this way, according to the number of holes in the disk or the number of gaps, you can measure the rotation speed of the measured shaft. The number of disc holes or notches is usually taken as still, so that each revolution of the measured axis, the photoelectric converter can output 60 pulse signals. If the time base signal of the electronic counter is 1 s, the measured shaft speed can be read directly.

The principle of the reflective speed sensor is the same as that of the transmissive type. It is through the photoelectric tube that converts the perceived light changes into electrical signal changes. However, it is through the reflection of light to obtain the pulse signal. Usually, the reflective material is pasted on the shaft under test. The reflective surface is formed on the measurement site. The commonly used reflective material is a special speed reflective tape (tape). It can also be replaced by a reflective material such as aluminum foil. Sometimes, the part to be measured may be coated with white paint as a reflective surface. The emitter and reflector should be properly configured, usually between 5-15M. When the measured shaft rotates, the photoelectric element receives pulsating light and outputs a corresponding electrical signal to send an electronic counter to measure the rotational speed of the measured shaft.

The waveform of the output signal of the photoelectric speed sensor is relatively regular, close to the standard square wave, and almost no interference signal is generated. However, the light-transmitting type will reduce the life of the light source due to vibration, so it is not suitable for use under conditions with strong vibration. Reflective and measured axis without any mechanical connection, easy to use.

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