Photoelectric sensor types
1. Standard photoelectric sensor
Diffuse reflectance type: normal or energy type (-8), focused type (-8-H), type with background and suppression function (8-H), type with background analysis function (-8-HW)
2. Reflective photoelectric switch/photoelectric sensor: Standard type (-6), type with polarization filtering function (-54-55), type with transparent body detection function (-54-G), type with background suppression function (-54-V)
A photoelectric switch that integrates the emitter and receiver into a single device, with a reflector mounted in front of it, and uses the principle of reflection to achieve photoelectric control, is called a reflector-type (or mirror-type) photoelectric switch. Under normal circumstances, the light emitted by the emitter is reflected back by the reflector and received by the receiver; if the light path is blocked by the object being detected, and the receiver cannot receive the light, the photoelectric switch will activate and output a switch control signal.
3. Through-beam photoelectric switch/photoelectric sensor
Separating the light emitter and receiver increases the detection distance. A photoelectric switch consisting of a light emitter and a receiver is called a through-beam photoelectric switch, or simply a photoelectric switch. Its detection distance can reach several meters or even tens of meters. In use, the light emitter and receiver are installed on opposite sides of the path of the object being detected. When the object passes by and blocks the light path, the receiver activates and outputs a switch control signal.
4. Slotted photoelectric switch/photoelectric sensor
A slotted photoelectric switch consists of a transmitter and a receiver mounted face-to-face on opposite sides of a slot. The transmitter emits infrared or visible light, which the receiver can pick up when there is no obstruction. However, when an object being measured passes through the slot, the light is blocked, triggering the photoelectric switch. It outputs a switch control signal to cut off or connect the load current, thus completing a control action. The detection distance of a slotted switch is typically only a few centimeters due to the limitations of its overall structure.
5. Fiber optic photoelectric switch/photoelectric sensor
A fiber optic photoelectric switch is formed by correctly guiding the light emitted by the emitter to the detection point using optical fiber, and then correctly guiding the detected light signal to the optical receiver using optical fiber. Depending on the operating method, fiber optic photoelectric switches can be divided into several types, including through-beam, reflective, and diffused reflective types.
Working principle of photoelectric sensors
Photoelectric sensors achieve control by converting changes in light intensity into changes in electrical signals.
A photoelectric sensor typically consists of three parts: a transmitter, a receiver, and a detection circuit.
The transmitter aims at the target and emits a light beam, typically from a semiconductor light source such as a light-emitting diode (LED), laser diode, or infrared emitting diode. The beam is emitted continuously or with varying pulse widths. The receiver consists of a photodiode, phototransistor, or photovoltaic cell. Optical elements such as lenses and apertures are mounted in front of the receiver. Behind it is a detection circuit that filters out the valid signal and applies it.
In addition to the above, the structural components of a photoelectric switch also include an emitting plate and optical fibers. The triangular reflector is a robust emitting device. It consists of very small triangular pyramidal reflective material and can accurately reflect the beam back from the reflector, which is of practical significance. It can also change the emission angle within the range of 0 to 25 degrees with respect to the optical axis, so that the beam almost originates from a single emission line and returns from the same reflection line after reflection.
Practical applications of photoelectric sensors
1. Avoid using dust turbidity monitoring instruments
Industrial dust pollution is a crucial aspect of energy conservation and environmental protection. To better eliminate industrial dust pollution, the first step is to determine the amount of dust emitted. Therefore, it is essential to monitor dust sources, automatically display emissions, and issue alarms for exceeding limits. The turbidity of dust in flues is detected by measuring the change in light intensity during its transmission within the flue. If the flue turbidity increases, the absorption and refraction of light emitted from the light source by dust particles increases, reducing the amount of light reaching the photodetector. Therefore, the strength of the photodetector's output signal reflects the change in flue turbidity.
II. Applications of photovoltaic cells in photoelectric detection and automatic control
When photovoltaic cells are used as photodetectors, their basic principle is the same as that of photodiodes, but their basic structure and manufacturing process are not exactly the same. Because photovoltaic cells do not require an external voltage to operate; they have high photoelectric conversion efficiency, a wide spectral range, good frequency characteristics, and low noise, they are widely used in photoelectric readout, photoelectric coupling, grating ranging, laser collimation, movie sound reproduction, ultraviolet monitors, and flameout protection devices for gas turbines, etc.
What types of photoelectric sensors are there? Most people probably already know the answer to this question! The global sensor market is experiencing rapid growth amidst constant change and innovation, and photoelectric sensors are currently a hot research topic in the international scientific community, although there is no unified, precise definition. With the rapid advancement of sensor technology, the types of photoelectric sensors will become increasingly diverse and practical in the future!
