An encoder is a device that encodes signals, such as bitstreams, or data and converts them into signals that can be used for communication, transmission, and storage. The encoder converts angular or linear displacements, known as code disks, into electrical signals. According to the readout mode, the encoder can be divided into contact type and non-contact type. According to working principle, encoders can be divided into incremental and absolute encoders. The incremental encoder converts the displacement into a periodic electrical signal, and then converts the electrical signal into a counting pulse, and uses the number of pulses to represent the displacement. Each position of the absolute encoder corresponds to a certain digital code, so its indication value is only related to the starting and ending positions of the measurement, and has nothing to do with the intermediate process of the measurement.

Encoders can be classified in the following ways. (1) Incremental: it is to send out an impulse signal every time the Angle of the unit is turned. Then subdivide it and cut out pulses with higher frequency), usually A phase, B phase and Z phase output, A phase and B phase pulse output with mutual delay of 1/4 cycle, according to the delay relationship can be distinguished positive and negative rotation, and by taking the rising and falling edges of A phase and B phase can be carried out 2 or 4 times frequency. The Z phase is a single-turn pulse, that is, one pulse is emitted per turn. (2) Absolute value type: it is corresponding to a circle, each datum Angle sends out a unique value corresponding to the binary value of this Angle, and multiple positions can be recorded and measured by the external coil device. 2. According to the output type of the signal, it can be divided into voltage output, collector open output, push-pull complementary output and long-line drive output. (1) Shaft type: Shaft type can be divided into clamping flange type, synchronous flange type and servo type, etc. (2) Axle sleeve type: axle sleeve type can be divided into half-air type, full-air type and large-diameter type, etc. 4. According to the working principle of encoder, it can be divided into photoelectric type, magnetoelectric type and contact brush type.

1. Failure of the encoder itself: it refers to the failure of components of the encoder itself, resulting in its failure to generate and output correct waveforms. In this case the encoder needs to be replaced or its internal components repaired. 2. Encoder connection cable fault: This kind of fault is most likely to occur and is often encountered in maintenance, so it should be a priority factor. It is usually the encoder cable break, short circuit or bad contact, then need to replace the cable or connector. Special attention should also be paid to whether the loose cable caused by loose welding or break, in this case the cable should be tightened. 3. Encoder +5V power drop: it means the +5V power is too low, usually no lower than 4.75V. The cause of the low is the power supply failure or the loss caused by the high resistance value of the power transmission cable, so the power supply needs to be repaired or the cable should be replaced. 4. Battery voltage drop of absolute encoder: This kind of fault usually gives a clear alarm, and the battery needs to be replaced at this time. If the memory of reference point position is lost, the operation of returning to reference point should be performed. 5. The shield wire of the encoder cable is not connected or falls off: interference signals will be introduced to make the waveform unstable and affect the accuracy of communication. The shielded wire must be welded and grounded reliably. 6. Loose encoder installation: This kind of fault will affect the position control accuracy and cause the position deviation in stopping and moving to be out of tolerance. It may even cause overload alarm of the servo system as soon as the machine is started up. 7, grating pollution will reduce the signal output amplitude, must use absorbent cotton dipped in anhydrous alcohol to gently wipe the oil.