Working principle and function of the encoder: it is a rotary type of sensor which converts rotating displacement into a series of digital pulse signals, which can be used to control the angular displacement. If the encoder is combined with the gear bar or the screw, it can also be used to measure the linear displacement.

The encoder generates an electrical signal, which is processed by CNC system, CNC, programmable logic controller PLC, control system, etc.. These sensors are mainly used in the following aspects: machine tools, materials processing, motor feedback systems and measurement and control equipment. The photoelectric scanning principle is adopted in the conversion of the angular displacement in the ELTRA encoder. The reading system is based on the rotation of the radial index disc, which is composed of an alternating light transmitting window and a non transparent window. This system with an infrared light source vertical illumination and so the light the plate on the image projected onto the surface of the receiver on, the receiver is covered with one layer of raster, collimator, it has and disc of the same window. The receiver 's job is to experience the light changes produced by the rotation of the disc, and then convert the light to the corresponding electrical changes. In general, the rotary encoder can also get a speed signal, this signal should be fed back to the inverter, which can adjust the output data of the converter. Fault phenomenon: 1, rotary encoder is bad (no output), the inverter can not work, become very slow, and for a while inverter protection, show "PG off"... In order to increase the electrical signal to a higher level and produce a square wave pulse without any interference, it is necessary to use the electronic circuit to deal with it. The connection mode between the encoder PG connection and the parameter vector transducer and the encoder PG must correspond to the type of encoder pg. Generally speaking, the encoder PG type points differential output, encoder collector open and push-pull outputs, the signal transfer must take into account the inverter PG card interface, so choose suitable PG card type or set reasonable.

Encoders are generally divided into incremental and absolute, they are the biggest difference: in the case of an incremental encoder, the position is determined from the number of pulses to start counting the number of bits, while the absolute encoder position is determined by the output code reading. In a circle, the reading of the output code of each position is unique; therefore, when the power supply is disconnected, the absolute encoder does not separate from the actual position. If the power is turned on again, then the position reading is still current and valid; unlike the incremental encoder, it is necessary to find the zero mark.

Now the encoder of the manufacturers are all very wide range, are generally dedicated, such as elevator specific type of encoder, machine tool dedicated encoder, servo motor specific encoder and so on, and the encoder is intelligent, there are a variety of parallel interface can communicate with other devices.

A device for converting angular displacement or linear displacement into electrical signals. The former became encoder, the latter known yardstick. According to the readout encoder can be divided into two types: contact and non-contact. Contact the output brush, brush, a contact conductive region or insulating region to represent the status code is "1" or "0"; non contact type acceptance of the sensitive element is photosensitive element or a magnetic sensitive element, the photosensitive element to translucent and opaque area to represent the status code is "1" or "0".

According to the working principle of the encoder can be divided into two categories of incremental and absolute. Incremental encoder is to convert the displacement into a periodic signal, and then the electrical signal into a counting pulse, the number of pulses used to indicate the size of the displacement. Each position of the absolute encoder corresponds to a defined number code, so that its value is only related to the beginning and end of the measurement, but not in the middle of the measurement.

Rotary incremental encoder to rotate the output pulse, through the counting device to know its location, when the encoder does not move or power outage, rely on counting the internal memory of the device to remember the location. In this way, when the power failure, the encoder can not have any movement, when the call work, the encoder output pulse process, there can be no interference and loss of pulse, or the zero point of the memory of the counting device will be offset, and the amount of this offset is not known, only the production of the wrong results appear to know. The solution is to increase the reference point, the encoder passes through the reference point, the reference position to modify the memory location of the counting device. Before the reference point, it is not to ensure the accuracy of the location of the. Therefore, in the industrial control have each operation to find a reference point, boot change method. This encoder is decided by the mechanical position encoder, it can't be affected by power outages, interference.