The light transmission speed sensor consists of a turntable with holes or notches, a light source and a photocell. When the disc rotates with the axis to be measured, the light can only shine on the photocell through the hole or notch. When the photocell is illuminated, its reverse resistance is very low, so an electric pulse signal is output. When the light source is covered by the disc, the reverse resistance of the photocell is large, and there is no signal output at the output end. In this way, the rotational speed of the measured shaft can be measured according to the number of holes or notches on the disc. The number of disc holes or notches is usually taken as still, so the photoelectric converter can output 60 pulse signals every time the measured shaft rotates. If the time base signal of the electronic counter is taken as 1s, the speed of the measured shaft can be read directly.
The principle of the reflective speed sensor is the same as that of the transparent type. It converts the perceived light changes into electrical signal changes through a photoelectric cell, but it obtains pulse signals through the reflection of light. Generally, the reflective material is pasted on the measuring part of the measured shaft to form a reflective surface. The commonly used reflective material is special speed measuring reflective paper tape (adhesive tape), which can also be replaced by reflective materials such as aluminum foil, and sometimes white paint can be coated on the tested part as the reflective surface. The projector and reflector shall be properly configured, and the distance between them is usually 5-15M. When the measured shaft rotates, the photoelectric element receives the pulsating light and outputs the corresponding electrical signal to the electronic counter to measure the speed of the measured shaft.
The output signal waveform of the photoelectric speed sensor is relatively regular, close to the standard square wave, and almost no interference signal is generated. However, as the vibration will reduce the life of the light source, the transparent type should not be used under the condition of strong vibration. The reflective type has no mechanical connection with the measured shaft and is easy to use.
Speed sensor
Application: Speed sensors are widely used in production equipment, special locomotives, wind power generation, etc. For example, online cutting of plates and pipes, cable or sandpaper speed measurement, etc; Because they are non-contact measurements, they are very suitable for measuring sensitive or untouchable objects, such as flannelette, fur and other textiles, coatings or viscose surfaces, and foam rubber surface objects; There are also metal processing industries, such as measuring the speed of steel, double pumping speed measurement, coating process control, etc.