What is a proximity sensor? What types of proximity sensors are there? How they work, their structure and application, let’s find out with plctop.com in the article below.
What is a Proximity Sensor?
Proximity sensor or proximity switch is a response when an object is near the sensor. In most cases, this gap is only a few millimeters. The proximity sensor usually detects the end position of the machine part and the output signal of the sensor initiates another function of the machine. Especially this sensor works well even in harsh environments.
Proximity sensors convert signals about the movement or appearance of objects into electrical signals. There are three detection systems to do this conversion: the system uses the change in capacitance when approaching the object to be detected, the system uses the eddy current generated in the metal object by the current electromagnetic induction object, the system using magnets and the magnetic addition switching system.
Features of the proximity sensor:
- Detect objects without contact, no impact on objects, the longest distance up to 30mm.
- Stable operation, good vibration and shock resistance.
- Fast response speed, long life compared to limit switch.
- Small sensor head can be installed in many places.
- Can operate in harsh environments.
The most popular types of proximity sensors today:
There are many types of proximity sensors in the industry, but there are mainly two types: inductive proximity sensors and capacitive inductive proximity sensors.
+ Inductive proximity sensor: detects objects by generating an electromagnetic field. This category is further divided into 2 categories:
- Protected magnetic induction: The magnetic field is concentrated on the front of the proximity sensor, so it has the advantage of less interference by surrounding metal. However, it makes the measuring distance shorter.
- Unprotected magnetic induction: because there is no magnetic field protection around the sensor face, the measuring distance is longer than the shielded induction type. However, it is susceptible to interference by surrounding metal.
+ Electrostatic Proximity Sensor: This sensor detects nearby objects based on electrostatic principle. That is, based on the change in capacitance between the object being detected and the sensor head. The advantage of this type is that it can detect all objects.
Structure and working principle of Proximity Sensor
In terms of structure, the proximity sensor consists of 4 parts: the sensor part, the oscillator circuit, the sensor and the output signal circuit.
In principle of operation, the proximity sensor operates on the principle of electromagnetic, or capacitive region. This electromagnetic/capacitive field will radiate around the sensor for a maximum distance of up to 60mm. In this distance, when it encounters an object, it will emit a signal and transmit it to the processor. Here, the processor will convert the signal about the movement or appearance of an object into an electrical signal. This signal is used as an alarm, or used to control the application through programming from the PLC/server.
To do this conversion, the proximity sensor needs 3 signal detection systems, which are:
The system uses the change in capacitance when approaching the object to be detected: the system uses a magnet and the system uses a magnetic addition switching system.
Application of Proximity Sensor
Proximity sensors are very commonly used in industries, especially in the electronics and factory industries. They can be mounted on production lines, cars, smartphones…
The most common uses of proximity sensors are usually:
+ Control liquid in tank yet, paper box.
+ Metal control.
+ Quantity control.
