An encoder is ... An incremental encoder

The word "encoder" is of English origin. It arose from the word encode, which means "convert." The most famous world manufacturers of these devices are such well-known brands as Siemens, SKB IS, HEIDENHAIN RLS, Baumer, SICK AG, Balluff, Schneider electric (Autonics Telemecanique), OMRON.

Scope and purpose of application

An encoder is a sensor used in an industrial area to convert a controlled quantity into an electrical signal. With it, for example, the position of the electric motor shaft is determined. Due to the fact that each device in which the rotation is applied must necessarily be equipped with a device that controls the accuracy of the torque, popular systems for the use of such converters are systems of precise displacement. The main purpose with which the encoder is applied is to measure the angle of rotation of an object during rotation. Encoders are indispensable in the production process at machine-tool manufacturing plants, in work-engineering complexes. They are also used in many modern measuring instruments, which require the recording of high-precision measurements of angles, rotation, turns and inclinations.

Ranking of encoders

All currently known encoders are divided into absolute and incremental, resistor, magnetic and optical, working through industrial networks or bus interface.

Depending on the general principle of work, absolute and incremental encoders are distinguished. The difference between these two types lies in the tasks they perform. The list of tasks of the absolute encoder is much wider than the list, which is covered by the incremental encoder.

Incremental encoders

This is a pulse sensor. In the process of turning the object at its outputs, pulses are fixed, the number of which is directly proportional to the angle of rotation of the object. Typically, incremental transducers are used in the machine tool process to record the angular movement of the shaft or in automated systems in the feedback circuit to measure and record the speed of rotation of the shaft.

An incremental encoder is a device that operates on the basis of the data of the pulses generated during rotation. The number of pulses per unit of revolution is the main operating parameter of this device. The current value is determined by the sensor by the method of counting the number of pulses from the reference point. With the aim of linking the reference systems to the pulse encoder, reference marks are set, which are the starting tags after switching on the equipment. Data definition using an incremental converter is possible only during rotation or rotation. When the rotation is stopped, all encoder data is reset. As a result, the next time you turn on the counter, the previous data will not be known. For ease of operation, the shaft must be brought to its original position. The incremental encoder is ideally suited to the task of measuring the speed of rotation. By counting the number of pulses from the reference mark, one can also accurately determine the current coordinate of the object's rotation angle.

Absolute encoders

This is the absolute position sensor. Usually in such encoders there are more complicated processes of electronic signal processing and there is an optical scheme. But they issue the requisites of the object immediately after the inclusion, which is often mandatory for the correct functioning of the system as a whole. In comparison with incremental, the use of absolute encoders allows solving a much wider range of problems, since measurements are made not by means of pulse fixing, but by special digital codes. The unit of measurement of such a device is the number of unique digital codes per unit of rotation (1 revolution). Due to the fact that all digital codes issued by the sensor are unique, it is not difficult to determine the current coordinate of the linear movement immediately after switching on the device and without using a reference label. At the time of activation, the code from the digits appears on the sensor outputs. It is the designation of the current position of the angle of rotation of the object. Thus, the absolute encoder does an excellent job not only with the task of tracking the rate of rotation (rotation) of the object, but also gives the correct data about its exact location at a given time, regardless of whether it is connected or not.

Varieties of absolute encoders

Depending on the characteristics of the characteristics, the absolute encoders may differ in the type of attachment, the presence of a blind or through, hollow or protruding shaft. The range of such devices is also very diverse in terms of external characteristics: length, body diameter and so on. In addition, it is known that absolute position measurement sensors during rotation are multi-turn and single-turn. Single-turners determine the current coordinate within 1 revolution, and multi-turn ones are capable of recognizing several additional turns.

Optical encoder - what is it?

This converter is a disk rigidly fixed to the shaft, made of glass. The optical encoder, in contrast to the above-described sensors, is additionally equipped with an optical discoloration that, during the rotation of the shaft, moves and converts the rotational moment into a light stream subsequently received by the photosensor.

This type of converter captures the rotation angles, where each unique position corresponds to a special unique code from the digits. It, together with the number of revolutions, represents the unit of measurement of the sensor. The encoder connection and its operation are identical to the operation of the incremental device described above.

Types of sensors depending on the principle of operation

According to the characteristics of the work, the encoders are divided into magnetic and photoelectric.

The physical principle of the first is based on the use of the Hall effect, discovered in 1879 by E. Hall. In this case, the potential difference arises only when a direct current conductor is placed in the magnetic field region.

According to the resolution and accuracy characteristics, the magnetic encoder is inferior to the photoelectric encoder, but its implementation is simpler. It is much less exacting to the spaces and conditions of functioning.

The representative of the magnetic encoder is a device that fixes the cycle of the magnetic pole of a rotating magnet located near the sensor element. The expression of the transmitter data also has the form of a digital code.

The photoelectric encoder is a sensor that operates on the basis of the photoelectric effect, which is observed as a result of the action of light on the substance. This principle was discovered in 1887 by H. Hertz. During the operation of the sensor of this type, a constant conversion of the light beam into an electrical signal is observed.

Synonymous with photoelectric encoder are optronic, optical and optoelectronic. Sensors of this type are more exacting to the characteristics of production, operation and much more than other encoders, but this is justified, since the potential for their accuracy is much higher than that of competitors.