What are KEYENCE proximity sensors and what are the types of proximity sensors?

[Profile]

What are KEYENCE proximity sensors and what are the types of proximity sensors?

The proximity sensors we refer to are a series of sensors used to detect the distance of objects, and their common point is that they will not touch objects during the detection process.

There are many types of KEYENCE proximity sensors. Common proximity sensors have the same principle. They transmit electromagnetic fields or light beams and analyze the changes in reflection to determine whether objects are approaching or appearing, leaving or disappearing.

The farthest detectable distance of KEYENCE proximity sensor is called "rated range". Some sensors can adjust the rated range to suit different purposes. If the rated range is adjusted within a short distance, the proximity sensor is usually used as a touch switch. Proximity sensors are usually characterized by high reliability and long service life. This is because there is no physical contact between the sensor and the sensed object, and the damage of mechanical parts is close to zero.

Different types of proximity sensors include inductive proximity sensors, capacitive proximity sensors, ultrasonic proximity sensors, photoelectric sensors and Hall effect sensors. Different proximity sensors are suitable for detecting different types of objects. For example, capacitive sensors are suitable for detecting plastic objects, while inductive proximity sensors are suitable for metal objects.

Connected to the working principle of KEYENCE proximity sensor

The proximity sensor emits electromagnetic field or electrostatic field or electromagnetic radiation beam (such as infrared) and waits for the return signal or field change. The sensed object is called the target of the proximity sensor.

　　

They have an oscillator as input and change the loss resistance by approaching the conductive medium. These sensors are metal targets of.

2 Capacitive proximity sensor

They convert and detect the electrostatic capacitance changes on both sides of the electrode and the grounding electrode. This occurs by approaching an object with a nearby oscillation frequency change. In order to detect nearby targets, the oscillation frequency is converted into a DC voltage and compared with a predetermined threshold. These sensors are plastic targets.

Type of KEYENCE proximity sensor:

The following are common proximity sensors:

KEYENCE proximity sensor is only used to detect metal objects. It works according to the induction principle, and the oscillator drives the coil until a metal object enters the coil.

Inductive sensors have become increasingly popular in recent years, although they are based on older designs. Unlike other technologies in this list, inductive sensors are only suitable for metallic materials. Inductive sensors will generate magnetic fields, and then detect the changes of magnetic fields when metal objects pass through, similar to the way that a rotating magnet in a coil generates electricity. Any metal detector starts with this.

Their detection range may be greatly limited by settings, especially in applications where gear rotation is calculated by detecting whether the gear teeth are close to the sensor. Inductive sensors can be installed on the road to detect vehicles traveling on them, or optimized to detect space plasma at a greater distance.

However, inductive sensors often work in the range of millimeters to meters when they are used as electronic proximity sensors. They are the best for ferrous materials such as iron and steel. Due to their working principle, they have a small detection range for non-magnetic metal materials. They have an extremely fast refresh rate because they depend on changes in electromagnetic fields.

KEYENCE proximity sensors can detect metal and non-metallic substances, such as liquids, powders and particles. It works by detecting capacitance conversion.

It has an oscillator, Schmidt lever and output switch circuit, much like an inductive sensor. The difference is that it has two charging boards for capacitors (one internal and one external):

·The oscillator is connected to the internal board.

·The sensing surface is an external plate (sensor electrode).

When the induced object approaches the sensor, the object will change the dielectric constant in the capacitive sensor. The sensor can know the distance of the object by measuring the dielectric constant.

However, the response speed of capacitive sensors is generally slow, and the update frequency is only 10~50Hz. However, since capacitive sensors are not affected by dust or opaque containers, they are often used to prohibit optical sensors. Typical capacitive sensors have an approximate rated range of 10 mm and can detect thickness changes within 0.01 mm.

KEYENCE proximity sensor detects the existence of objects, or uses ultrasonic pulse to detect the distance of objects through additional processing. They work by using transmitters and receivers and echo location principles.

The ultrasonic sensor can determine the distance from the object by sending chirp and measuring the time required for the chirp to bounce back from the surface. Although transmitters and receivers are usually configured as similar to each other as possible, these concepts still apply when they are isolated. Also provided is an ultrasonic transceiver that combines transmission and reception functions into one unit.

Ultrasonic detection is very accurate, with a high refresh rate, which can emit tens or hundreds of pulses or chirps per second. The color and transparency of the object have little effect on the reading because they are based on sound rather than electromagnetic waves.

This same characteristic means that they do not need or do not emit light, which makes them very suitable for inherently dark or must be dark conditions. The sound wave will spread over time, expanding the detection area - depending on the application, this may be beneficial or unfavorable. Due to its simple nature, these are also very low-cost, flexible and secure.

On the other hand, ultrasonic sensor has its own series of shortcomings. The sensor consists of transmitter and receiver, which can be used together or purchased separately. Since the sound speed changes with the air temperature, any significant temperature change will affect the accuracy. However, this can be alleviated by updating the calculations using temperature measurements.

Soft materials may affect accuracy due to poor reflection of sound waves on the absorbing surface. Although ultrasonic sensors are essentially similar to sonar, they are not designed for underwater use. Finally, because there is no medium for sound propagation in vacuum, their dependence on sound makes them useless.

KEYENCE proximity sensor emits a beam of infrared light to detect the existence of objects. It works in the same way as the ultrasonic sensor, but it does not use sound waves, but sends infrared signals.

The infrared proximity sensor includes an IR LED that emits light and a light detector that detects reflected light. It has a built-in signal processing circuit, which can provide a light spot on the PSD.

How does the infrared proximity sensor work? First, infrared light is emitted from the infrared LED transmitter. The beam then hits the object and bounces back at an angle. The reflected light will reach the photodetector. Finally, the sensor in the photodetector determines the position/distance of the reflecting object.

KEYENCE proximity sensor consists of beam generator, special beam detector, amplifier and microprocessor. When the emitted beam is reflected by an object, the photodetector will sense it, and the sensor will detect the object by this method.

The emitted beam will be modulated to a specific frequency, and the detector also has a frequency sensitive amplifier, which will only respond to light modulated at a corresponding frequency. This prevents false detection caused by light or sunlight. When the photoelectric proximity sensor senses a black object, the non reflective characteristics of the object will hinder the normal operation of the sensor, as well as the transparent or refractive object.

Although KEYENCE proximity sensors are suitable for many industrial applications, they are also widely used in residential and commercial environments, such as garage door sensors and people counting in stores. The photoelectric sensor can be set in various ways in terms of implementation. The transmitter is used on one side and the detector is used on the other side. When the beam breaks, the detection is carried out.

The transmitter and detector are located in a retroreflective system, and the reflector on the other side reflects the signal from the transmitter back to the detector. Finally, diffusion brings the transmitter and detector close together, but the emitted light will reflect from any surrounding surface, much like an ultrasonic sensor, but cannot measure distance.

Due to the lack of moving parts, the photoelectric sensor has a long life and can detect a wide range of materials, while transparent materials and water may cause problems. Opposite and retro reflective settings provide long sensing range and fast response time. Small objects can be detected through diffuse reflective settings or mobile detectors.

KEYENCE proximity sensors can withstand dirty conditions in industrial applications as long as the lens is not contaminated. However, their ability to measure distance from objects is severely limited, and object color and reflectivity may cause problems. In a busy environment, the installation of equipment can be complex, because it is necessary to install and align the opposed and retroreflective types.