The proximity sensors and photoelectric sensors are widely used in automation applications. But there are some differences between them. Let’s check them one by one.
Differences between the proximity sensor and photoelectric sensor
Differences between proximity and photoelectric sensor are the following.
The proximity sensor is a type of device that detects an object when the object approaches within the detection range and boundary of the sensor. There is no physical contact between the object and the sensor. Inductive proximity sensors detect only metal objects. Capacitive proximity sensors can sense both metallic and non-metallic objects. The photoelectric sensor is an electrical device that responds to a change in the intensity of the light falling upon it.
Method of detection
A proximity sensor uses an electromagnetic field and detects an object without physical contact. Then, converts this information into an electrical signal.
A photoelectric sensor uses light and detects the object without physical contact. The optical signal transmitted from the emitting part of the sensor is modified by being reflected, transmitted, absorbed, etc., by the sensing object and is then detected by the receiving part of the sensor to generate a corresponding output signal.
The proximity sensor has a short sensing range compared to the photoelectric sensor. The sensing range of a proximity sensor is within 1 in. (25,44 mm). The sensing range of a photoelectric sensor is up to 800 ft. (243,8 m)
The proximity sensor detects metallic and non-metallic objects. On the other hand, the photoelectric sensor can detect objects of any material provided they affect the optical beam. This means that a photoelectric sensor can be used to detect virtually any object, including glass, plastic, wood, and liquid. (Whether transparent or opaque, small or fast, perforated or shiny, uneven or wrapped in film, near or far.)
The use of an optical beam for detection and complete electronic circuitry makes the photoelectric sensor respond in microseconds that they can be easily used on a high-speed production line. The response time is extremely fast because light travels at high speed and the sensor performs no mechanical operations because all circuits are comprised of electronic components. The proximity sensor has a little bit longer response time compared to the photoelectric sensor. It detects objects in milliseconds.
The photoelectric sensor can detect invisible markings on products. The proximity sensor cannot detect the markings.
The size of a photoelectric sensor is smaller than a proximity sensor.
Since the reflection and the absorption characteristics vary with the object color for a specified incident optical wavelength, various colors can be detected with a photoelectric sensor as the difference in optical intensity. The proximity sensor cannot identify the colors.
Dust and dirt
The photoelectric sensor has the drawback that if the lens surface is covered with dust or dirt and light transmission is obstructed, detection may not be possible. The proximity sensor does not have this problem.
The incredibly high resolution achieved with the photoelectric sensor derives from advanced design technologies that yielded a very small spot beam and a unique optical system for receiving light. These developments enable detecting very small objects, as well as precise position detection. The proximity sensor can detect larger objects.
Positioning the beam on an object with a photoelectric sensor is simple with models that emit visible light because the beam is visible. The adjustment of a proximity sensor is a bit complex.