Shaft type: shaft type can be divided into clamping flange type, synchronous flange type and servo installation type.

Axle sleeve type: axle sleeve type can be divided into half - empty type, full - empty type and large caliber type.

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

Encoders can be classified into incremental and absolute encoders according to the way of hole cutting.

The incremental encoder converts the displacement into a periodic electrical signal, and then converts the electrical signal into a counting pulse.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 measurement, and has nothing to do with the middle process of measurement.

The rotary incremental encoder outputs pulses as it rotates, and its position is known by the counting device. When the encoder is stationary or has a power failure, it relies on the internal memory of the counting device to remember the position.In this way, after 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, otherwise, the zero point of the memory of the counting device will be offset, and the amount of this offset is not known, only the wrong production results to know.

The solution is to add a reference point. Each time the encoder passes through the reference point, the reference position is corrected into the memory position of the counting device.Before the reference point, the accuracy of the position cannot be guaranteed.To this end, in the industrial control, there are each operation to find a reference point, such as starting the zero method.

Printers, scanners, for example, the positioning of the principle is to use incremental encoder, the computer, we can all hear chip, li crash of a ring, it is looking for a reference zero, then work.

Such a method for some industrial control projects more trouble, even do not allow the boot change (boot will know the exact location), so there is an absolute encoder.

Absolute rotary photoelectric encoder, because of its absolute unique position, anti-interference, no power memory, has been more and more widely used in various industrial systems in the Angle, length measurement and positioning control.

Absolute encoder optical encoder, there are many scribed line, every groove in turn in line 2, line 4, 8, 16 line arrangement, so, in every position of encoder, by reading each groove and the dark, get a set of zero power from 2 to 2 n - 1 to the power of the only two hexadecimal code (gray code), it is called a n a absolute encoder.Such an encoder is determined by the mechanical position of the code disk, which is not affected by power failure and interference.

Absolute encoder by the mechanical position of the uniqueness of each position, it does not need to remember, do not look for a reference point, and do not always count, when you need to know the position, when to read its position.In this way, the anti-interference characteristic and data reliability of the encoder are greatly improved.

Because absolute encoder is obviously better than incremental encoder in positioning, it has been used more and more in industrial positioning.Absolute encoder because of its high precision, output figures, such as still using parallel output, the output signal must ensure that every connection is very good, for more complex conditions and isolation, connecting cable some more, thus bring many inconvenience and reduce the reliability, therefore, absolute encoder in multibit output type, generally selects the serial output or linear output, the German production of absolute encoder is the most commonly used serial output SSI (synchronous serial output)