Rotary encoder is used to measure the rotational speed of the device, photoelectric rotary encoder by photoelectric conversion, the output shaft of the angular displacement, angular velocity and other mechanical parameters into the corresponding electrical pulse with digital output (REP). It is divided into two kinds of single output and double output. The main technical parameters are the number of pulses per revolution (tens to thousands of), and the power supply voltage, etc.. Single output is the output of the rotary encoder is a set of pulses, and the dual output of the rotary encoder output two sets of A/B phase difference of 90 degrees of pulse, through the two sets of pulses can not only measure the speed, but also can determine the direction of rotation.

The encoder can be divided into the principle of signal.

Incremental pulse encoder: SPC

Absolute pulse encoder: APC

Both are generally used in speed control or position control system for the detection of components.

The distinction between incremental encoder and absolute encoder

Working principle

By a center shaft of photoelectric encoder and its a groove ring, dark, photoelectric emission and receiving device reads, obtained four groups of sine wave signals are combined into a, B, C, D, each sine wave phase difference of 90 degrees out of phase difference (with respect to a cycle is 360 degrees), C, D reverse signal, superimposed on the A and B phase, stable signal enhancement; other output per turn of a Z phase pulse to represent zero reference.

Due to A, B phase difference of 90 degrees, can be compared to the A phase before or B phase in the former, in order to determine the encoder's forward and reverse, through the zero position pulse, can obtain the encoder zero reference bit.

Encoder of materials, glass, metal, plastic, glass disk is in the glass on the sediment in a thin groove, its thermal stability is good, high precision, metal code disk directly to pass and the barrier dividing, not fragile, but due to the metal with a certain thickness accuracy is limited, its thermal stability to worse than glass and an order of magnitude, the plastic disk is economy, the cost is low, but accuracy, thermal stability and longevity to some difference.

Resolution - encoder to each rotation 360 degree provide much or dark reticle said resolution, also known as analytical indexing, or directly referred to line number, generally with each turn indexing 5~10000 line.

Signal output:

Signal output sine wave (current or voltage), square wave (TTL, HTL), and an open collector (PNP and NPN), push and pull type forms, where the TTL for long-term poor device (symmetric a, a, B, B -, Z, z), HTL, also known as push pull type and push-pull output, the encoder signal receiving device interface should correspond to the encoder.

Signal connection - the encoder pulse signal is generally connected to the counter, PLC, computer, PLC and computer connected modules have low speed module and high speed module, the switch frequency is low and high.

Such as single phase connection, used for single direction counting, single direction velocity measurement.

A.B two phase connection, used for positive and reverse counting, to judge the positive and reverse and speed.

A, B, Z three phase connection, for reference position measurement.

A, A-, B, B-, Z, Z- connection, due to the connection with a symmetrical negative signal, the current electromagnetic field for the cable to contribute to 0, attenuation, the best anti interference, can be transmitted over the distance.

For TTL with symmetric negative signal output of the encoder, the signal transmission distance of up to 150 meters.

The rotary encoder is made up of precision components, so when being subjected to a larger impact, the internal function may be damaged, and the use of the device should be fully paid attention to.