The working principle of the encoder.！

  Absolute pulse coder: APC
  Incremental encoder: SPC
  Both are generally applied to the detection element speed control or position control system.
The rotary encoder is used to measure the speed of the device. It is divided into single output and dual output two kinds. Technical data pulse count (tens to thousands there) per revolution, and power supply voltage. Single Output refers to the output of the rotary encoder is a pulse, and the rotary encoder output pulses two dual output phase difference of 90 degrees, by these two groups can not only measure the speed pulse, can also determine the direction of rotation.
  Incremental encoder and absolute encoder distinction
  In principle, such as the encoder signal points, incremental encoders, absolute encoders.
  Incremental encoder (rotary）

  It consists of a center axis of the optical encoder, which has a ring through the dark of the engraved lines, optoelectronic transmitting and receiving device to read, get a sine wave signals into four groups A, B, C, D, each sine wave phase difference of 90 degrees (with respect to a cycle of 360 degrees), the C, D inverted signal, superimposed on a, B on the two-phase, can enhance stabilization signal; output per rotation other Z-phase pulse to represent a zero reference bit.
 Since the A, B two-phase difference of 90 degrees, the first phase A or B by comparing the first phase, in order to determine the encoder forward and reverse, the zero pulse can be obtained encoder zero reference position.
 Encoder code disc material glass, metal, plastic, glass code discs are deposited thin engraved lines on the glass, good thermal stability, high accuracy, metal code disc directly through the barrier and engraved lines, non-friable, However, since the metal has a certain thickness, there are restrictions precision, thermal stability is necessary an order of magnitude worse than glass, plastic code disc is a economical, low cost, but the accuracy, thermal stability and life are to be worse .
 Resolution - 360 degrees per encoder rotation through or how much dark groove called the resolution, also known as analytic indexing, or direct say how much wire, usually 5 degrees per rpm to 10,000 lines.
 Signal output:
There are a sine wave output signal (current or voltage), square wave (TTL, HTL), open collector (PNP, NPN), push-pull many forms, as long TTL differential drive (symmetric A, A-; B, B -; Z, Z -), HTL, also known as push-pull, push-pull output encoder signal receiving device interface should correspond with the encoder.
 Signal connection - module encoder pulse signal typically connected counter, PLC, computer, PLC and computer are connected to high-speed and low-speed module module of the points, with a high switching frequency is low.
 Such as single-phase connection, for uni-directional counting, one-way speed.
 A.B two coupled for forward and reverse counting, and speed to determine the pros and cons.
 A, B, Z-phase coupling for position measurement with a reference bit correction.
 A, A-, B, B-, Z, Z- connection, since the connection with symmetrical negative signals, the contribution of the current cable for the electromagnetic field is 0, the minimum attenuation, the optimum interference can transmit greater distances.
 For TTL signal output with symmetric negative encoder signal transmission distance up to 150 meters.
 For HTL with symmetrical negative signal output from the encoder, the signal transmission distance up to 300 meters.

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