Inductive proximity sensors: basic characteristics, operating principle of the device

Work in manufacturing plants requires partial or complete automation of the system. For this, various devices are used to ensure smooth operation. Metal fixtures quite often control inductive proximity sensors, which have their own advantages and disadvantages. They are small in size and perform well, provided they are properly connected.

General information

An induction sensor is a special device related to non-contact. This means that to determine the location of an object in space, it does not need direct contact with it. Thanks to this technology, the automation of the production process is possible.

Typically, the fixture is used in various lines and systems in large factories and factories. It can also be used as a limit switch. The device is of high quality and reliability, works even in difficult conditions. It affects only metal objects, since other materials are insensitive to it.

The device is quite resistant to aggressive chemicals and is widely used in the machine-building, food and textile industries. The aerospace, military, and rail industries also need these sensors.

The importance of the device makes it in demand, so many companies around the world release various models with a standard and extended set of functions, in different price categories.

Device device

An inductive sensor consists of several interconnected units, which ensure its uninterrupted operation.. The main parts of the fixture are as follows:

1. The generator is considered the main element of the device, since it is responsible for the formation of the electromagnetic field necessary for its functioning.
2. The Schmidt trigger is responsible for processing the information received after turning on the generator and transferring it to other nodes.
3. An indispensable part of every sensor is an amplifier, which is necessary for transmitting a signal over long distances.
4. A special indicator on LEDs allows the person responsible for the operation of the device to monitor its operation and recognize the signal when it is turned on, as well as when settings are changed.
5. Compound is a special part that prevents the ingress of various small particles into the device. Plays an important role, since any foreign objects can interfere with the operation of the device.

All elements are located in a housing made of brass or polyamide. These materials are considered to be very durable in order to protect the core from the negative effects of manufacturing conditions. Due to its robust design, the sensor is able to withstand a significant load and at the same time function correctly.

Principle of operation

Thanks to a special generator that produces special vibrations, the device operates. When an object made of metal enters its field of action, a signal is sent to the control unit.

The work of the device begins after switching on, which gives an impetus to the formation of a magnetic field. This field, in turn, affects eddy currents, which change the oscillation amplitude of the generator, which is the first to react to any changes.

As soon as a signal arrives, processing begins in other nodes of the device. The strength of this signal largely depends on the size of the object that has fallen into the field of action of the device, as well as the distance at which it is located. The next step is to convert the analog signal to a logical one. Only in this way is it possible to accurately determine its meaning.

Such sensors play a special role in production.where the metal parts must follow the line in a specific position. The device can fix it and when it detects any, even a slight deviation, it signals to the main control panel.

As a rule, the reading of the results of the operation of the device is carried out by a specialist who also performs the role of a controller who oversees the smooth operation of the entire system.

Basic definitions

There are several definitions for controlling the operation of the device and reading its signals. The most important are the following:

1. The core is the area where the effect of the magnetic field emitted by the generator is most pronounced. It is located directly in front of the sensitive surface of the sensor, where the highest and most intense concentration level is noted. Usually this area is not difficult to determine, since its diameter is almost the same as the diameter of the device.
2. The nominal switching distance is considered a theoretical parameter, since it does not take into account some of the production characteristics of each particular plant. Its value is approximate, since temperature, pressure and voltage in a certain zone are not taken into account.
3. The working gap is one of the most important parameters that determine the settings of the device, at which it will give the most correct signals without any failures. Usually, to determine these values, the device is tested in different conditions and the average is determined.
4. The correction factor should also be taken into account, since it is from it that the specialist starts when choosing the device settings. The reading will vary depending on the impurities present in the metal object. Typically, deviation is observed when using various metal alloys.

Thanks to these definitions, it is possible to customize the device to obtain the most accurate data that plays an important role in the production process.

Advantages and disadvantages

Induction sensors have their own advantages and disadvantages, just like any other device. The main advantage is considered to be the simplicity of the design, which does not require complex configuration and does not require special conditions for mounting. The device has no sliding contacts, is made of durable material and can work for a long time without interruption.

It is also worth noting that the device rarely fails, and its repair is not difficult. That is why it is often installed in enterprises where almost round-the-clock control over the production process is required. The non-contact connection allows a seamless connection to an industrial voltage system.

An important advantage is considered to be high sensitivity, which makes it possible to install sensors in production, where they work with metal objects from different alloys.

Despite all the advantages of the device, there are some disadvantages. The most important are the errors that the device produces in operation. The non-linear type of error is manifested due to the fact that the device has its own indicator of the inductive value, which may differ from the value of those objects to which it reacts. That is why the sensor can react incorrectly to metal and give incorrect signals.

Temperature errors are often encountered associated with a significant decrease or increase in temperature in the production area. The instruction for the device assumes its correct functioning at an indicator of +25 degrees. If the value deviates in one direction or another, the work of the device is disrupted.

One of the random errors is considered to be a change in the sensor readings due to the effect on it of the electromagnetic field of other devices. In order to avoid such situations, a standard for the frequency of electrical installations, which is 50 Hz, is set in all industries. In this case, the risk of errors due to extraneous electromagnetic radiation is reduced to a minimum. It is possible to exclude any disturbances in the operation of the device by preliminary study of the details.

Connection methods

Depending on the type of device, the methods of connecting it are also different, since certain varieties have a different number of wires. Two-wire are considered the simplest, but also the most problematic option. They are connected directly to the current load circuit. For correct manipulation, a nominal load resistance is required. In the event of its decrease or increase, the device begins to function incorrectly. An important point will be the connection to the network, in which it is necessary to observe the polarity.

Three-wire are considered the most popular and easiest to connect. Some wires are connected to the load, and the other two to the voltage source. This eliminates the likelihood of the device reacting to the nominal resistance in the form of incorrect operation.

There are also four and five wire sensors. When installed, two wires are connected to the voltage source, two to the load. If a fifth cord is present, then there is a choice of a suitable operating mode.

The wires are usually marked with different colors to facilitate installation and subsequent maintenance of the sensor. Minus and plus are marked in blue and red, respectively. The exit is always marked in black. There are devices with two outputs. The second is usually white and can also serve as an entrance. These nuances are indicated in the operating instructions for the inductive sensor.

The body of the device can be made of different materials, have a cylindrical, square or rectangular shape. The first option is considered the most common.

Selection rules

An induction sensor is considered an important element in many enterprises, therefore, its choice should be approached very responsibly. It is recommended to observe the following rules:

• precise definition of the conditions under which the device will be used: temperature conditions in room, humidity, direct sunlight and electromagnetic radiation from others devices;
• the speed of the production process, which will affect the correct operation of the sensor;
• the accuracy of the device itself, promised by the manufacturer, as well as linearity;
• reliability of construction and quality of materials, estimated service life and warranty from the company;
• the class of protection used in the production process, which will help prevent breakdowns that often occur under adverse working conditions;
• the size of the fixture also plays a role as miniature sensors are less prone to being hit by debris and other particles.

An important parameter is the cost of the device. It most often depends on the manufacturer and some additional functions that are built into the sensor. However, there is no significant difference in the performance of devices from different price categories.

Popular models

There are many models of inductive sensors on the market today. The most popular are various devices from the Russian company TEKO. They are distinguished by good quality, excellent technical characteristics, ease of installation and operation. The main advantage of the company's devices is an affordable price.

The cost of simple models starts at 850 rubles, and for this money the device works flawlessly. More expensive sensors are also produced with a price from 2 to 5 thousand rubles. They are usually installed in large factories where high precision and trouble-free operation are required.

The inductive sensor is considered one of the best non-contact devices used in various factories, factories and other enterprises. The high quality and accuracy of the device makes it in demand and necessary.