Introduction to the principle of encoder

An encoder is a device that compiles and converts a signal (such as a bit stream) or data into a signal form that can be used for communication, transmission, and storage. The encoder converts angular displacement or linear displacement into electrical signals. The former is called a code wheel and the latter is called a code ruler. Encoders can be divided into two types: contact type and non-contact type according to the readout mode; encoders can be divided into two types: incremental type and absolute type according to the working principle. The incremental encoder converts the displacement into a periodic electric signal, and then converts this electric signal into a counting pulse, and the number of pulses is used to indicate the magnitude of the displacement. Each position of the absolute encoder corresponds to a certain digital code, so its indication is only related to the start and end positions of the measurement, and has nothing to do with the middle process of the measurement.

Encoders can be classified in the following ways.

1. According to the different classification of code discs

(1) Incremental type: It is to send out a pulse signal every time the angle of the unit is rotated. Then it is subdivided, and the higher frequency pulse is generated), usually A phase, B phase, Z phase output, A Phase and Phase B are pulse outputs delayed by 1/4 cycle. According to the delay relationship, the forward and reverse can be distinguished, and the frequency can be doubled or quadrupled by taking the rising and falling edges of Phase A and Phase B; Phase Z is single-turn Pulse, that is, one pulse per revolution.

(2) Absolute value type: it corresponds to a circle, and each reference angle emits a unique binary value corresponding to the angle, and the recording and measurement of multiple positions can be performed through an external circle device.

2. According to the type of signal output, it is divided into: voltage output, open collector output, push-pull complementary output and long-line drive output.

3. Classified by encoder mechanical installation form

(1) Shaft type: Shaft type can be divided into clamping flange type, synchronous flange type and servo mounting type.

(2) Shaft sleeve type: The shaft sleeve type can be divided into half hollow type, full hollow type and large diameter type.

4. According to the working principle of the encoder, it can be divided into: photoelectric type, magnetoelectric type and contact brush type.

1. Encoder failure: it refers to the failure of the encoder's own components, causing it to fail to generate and output the correct waveform. In this case, you need to replace the encoder or repair its internal components.

2. Encoder connection cable failure: This type of failure has the highest probability of occurrence. It is often encountered during maintenance and should be the priority factor. Usually the encoder cable is open, short-circuited or poorly contacted. At this time, the cable or connector needs to be replaced. Special attention should also be paid to whether the cable is not tightly fixed, causing loosening or disconnection. At this time, the cable needs to be clamped.

3. Encoder +5V power supply drop: refers to the +5V power supply is too low, usually not lower than 4.75V, the cause of the too low is the power supply failure or the power transmission cable resistance is too large and the loss is caused, then the power supply needs to be repaired Or replace the cable.

4. Absolute encoder battery voltage drop: This type of failure usually has a clear alarm. At this time, the battery needs to be replaced. If the memory of the reference point position is lost, the operation of returning to the reference point must be performed.

5. The shielded wire of the encoder cable is not connected or falls off: This will introduce interference signals, make the waveform unstable, and affect the accuracy of communication. It is necessary to ensure that the shielded wire is reliably welded and grounded.

6. Loose encoder installation: This kind of failure will affect the accuracy of position control, causing excessive position deviation during stopping and moving, and even the servo system overload alarm will be generated as soon as it is turned on. Please pay special attention.

7. Grating pollution This will reduce the signal output amplitude, so you must use absorbent cotton dipped in absolute alcohol to gently wipe off the oil.

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