Working principle of incremental encoder

Incremental encoder (rotary)

1 Working principle:

The photoelectric transmitting receiving device reads a photoelectric code disc with the center as the axis, which is engraved with circular dark engraved lines, combines four groups of sine wave signals into A, B, C, D, each sine wave is 90 degrees apart (Relative to a cycle of 360 degrees), the C D signals are superimposed on the A B phases in reverse to enhance the stable signal; in addition, a Z-phase pulse is output per revolution to indicate the zero reference position.

Since the phase A the phase B are different by 90 degrees, the forward reverse rotation of the encoder can be judged by comparing whether the A phase is the first phase the B phase. The zero reference position of the encoder can be obtained through the zero pulse.

The material of the code disc includes glass, metal plastic. The glass code disc is composed of thin wires deposited on the glass, with good thermal stability high precision. The metal code plate is directly engraved with impenetrable lines, which is fragile. However, because metal has a certain thickness, its accuracy is limited, its thermal stability is one order of magnitude worse than glass. The plastic code wheel is economical low in cost, but its accuracy, thermal stability life are poor.

The number of open dark engraved lines provided by the resolution encoder per 360-degree rotation is called the resolution, also known as the resolution index, directly called the number of lines, usually 5 to 10,000 lines per revolution.

2 signal output:

The signal output has various forms of sine wave (current voltage), square wave (TTL, HTL), open collector (PNP, NPN), push-pull. Among them, TTL is a long-line differential drive (symmetric a, a-; B) , B-; Z, Z-), HTL is also called push-pull push-pull output. The signal receiving device interface of the encoder should correspond to the encoder.

Signal connection The pulse signal of the encoder is usually connected to the counter, plc computer. Modules connected with PLC computer are divided into low-speed modules high-speed modules, the switching frequency is divided into high low.

Such as single-phase connection, used for one-way counting one-way speed measurement.

A B two-phase connection, used for forward reverse counting, forward reverse judgment speed measurement.

A, B, Z three-phase connection, used for position measurement with reference position correction.

A. As the distance between A—Z— is longer, A—Z—is the transmission distance, B—is caused by the negative connection of A—Z—.

For TTL encoders with symmetrical negative signal output, the signal transmission distance can reach 150 meters.

For HTL encoders with symmetrical negative signal output, the signal transmission distance can reach 300 meters.

three. Problems with incremental encoders:

The cumulative error of the incremental encoder is zero, the anti-interference ability is poor. The receiving device needs to be memorized when it is turned off, it is changed referenced when it is turned on. Using an absolute encoder can solve these problems.

General application of incremental encoder:

Speed measurement, rotation direction measurement, movement angle measurement, distance (relative).

DEUPREE (Qingdao) Industrial Technology Co., Ltd. is an integrated enterprise focusing on the research development of automated industrial technology equipment manufacturing. The company’s products mainly include rotational motion sensors, linear displacement sensors, object recognition sensors, laser rangefinders, process Control measurement instruments, signal detection systems, signal transmission systems, immature drive systems, UPS safety power supply systems, automation equipment energy-saving cleaning auxiliary equipment systems are limited to this. We can also customize flexibly customize according to customer needs. Meet the different needs of different customers.