Proximity Sensor Types and Uses in Industries
To detect the presence of an object without being into physical contact with the object, proximity sensors are used. The proximity sensor works on different principles to sense different objects. Different types of sensors are used in for different scenarios where the detection of the objects is required through non-physical contact. For example, inductive type proximity sensor used for metallic objects and capacitive type sensor for non metallic objects.
Mainly there are two types like inductive and capacitive. But proximity sensors are further classified into several types depending on the principles that are used for the detection of an object without any physical contact. They are also classified according to the type of material they sense.
Here is the list of some basic types of the proximity sensor.
Inductive Proximity Sensor:
The inductive sensor is the type of proximity sensor used to detect metallic objects without being in physical contact with the object. The principle under which the inductive proximity sensor is the electrical principle of inductance. The target object is detected when an electromagnetic force is induced in the object due to the fluctuation of the current.
The inductive sensor makes use of an oscillator circuit for the generation of the high frequency of the electromagnetic field. When an object comes in touch with the field, then at the surface of the object an eddy current will be produced. The eddy current absorbs radiated energy from the sensor, this will result in the loss of energy and also the strength of the oscillator will be changed.
The changes in the strength of the magnetic field will be detected by the sensor detection section of the sensor, it will then trigger a solid-state output level if the strength of the magnetic field starts decreasing.
- The accuracy rate is high
- Switching rate is also very high
- Harsh environmental condition is not a limitation for this type of proximity sensor.
- Only suitable for the detection of metallic objects
- Range limitation
Capacitive Proximity Sensor:
Capacitive sensors are almost similar to inductive proximity sensors, the only difference between these two types of proximity sensors is that the capacitive inductor produces electrostatic instead of the electromagnetic field.
The formation of the sensing surface is made using two metal electrodes, the oscillator produces the electrostatic field between two plates. Whenever a metallic or non-metallic object meets the electrostatic field, the capacitance of the oscillator changes.
The oscillator circuit begins to oscillate and changes the state of the output of the proximity sensor as a result when it reaches a certain value of amplitude.
- Detection of metal and non-metal object is possible with the help of capacitive sensors
- Very high speed of detecting an object
- Very good stability
- Power usage is efficient
- The cost is very low
- Temperature and humidity effects the performance of the sensor
- The accuracy level is less as compared to the inductive sensor
- Designing very difficult.
Photoelectric Proximity Sensor:
This sensor works on the principle of light for the detection of objects without any physical contact with the object. There are 2 basic types of photoelectric sensors
- Reflective sensor
- Through-beam sensor
The reflective sensor works by the emission of a beam of light that hits the object and reflected the sensor, usually in the same physical house as beam emitter.
The through-beam sensor, on the other hand, comprises two parts, one is an emitter, also known as a source of light and the other is a detector or separate receiver. Whenever an object breaks the beam of light, the detector will register this break.
- It is also known as an all-purpose sensor because it has the capability of sensing all types of material.
- The life span is longer
- The sensing range is good
- It is very reliable
- The response time is very fast
- The cost is very low
- Lens gets contaminated
- Two separate components are required.
All the different proximity sensors types and their application in industries are well described and their comparison you can see in following image
If you want to learn about working principles for all above sensors you can check this link
All images credit goes to machinedesign