The encoder working principle, Function and Classification！

The encoder working principle, Function and Classification

    Encoder (encoder) is a signal (such as bit-stream) or data compiled, converted to be used to signal in the form of communication, transport and storage equipment.

The encoder working principle

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.

Encoder Function
The encoder is a rotational displacement of the pulse signal into a stream of digital rotary transducer, these pulses can be used to control the angular displacement, if the encoder strip or in combination with the screw gear together, can also be used to measure linear displacement.

After the encoder generates an electrical signal from the speed control is set CNC, programmable logic controller PLC, control system to deal with. These sensors are used in the following areas: machine tools, material processing, motor feedback systems, and measurement and control equipment. In ELTRA angular displacement encoder using a photoelectric conversion scanning principle. Reading system is based on the rotation of the radial indexing plate, the indexing consists of alternating opaque and translucent window windows constructed. This whole system is irradiated with an infrared light source vertically, so put the image on a plate light projected onto the surface of the receiver, the receiver is covered with a grating, said collimator device, and it has a disc the same window. The receiver's job is to feel the light generated by the change in rotation of the disc, and then converts the light into a corresponding change in the electrical changes. In general, the rotary encoder can also get a speed signal, the signal to be fed back to the inverter, thereby adjusting the output data of the inverter.

Symptom: 1, rotary encoders bad (no output), the inverter does not work, it becomes very slow speed, and while the drive protection, display "PG off." . . Joint action to work. For electric signal rises to a higher level, without any interference, and produce a square wave pulse, which must be processed by the electronic circuit. Pg encoder connection wiring and parameter vector inverter and encoder pg between the encoder must correspond to the model pg. Generally, the encoder pg model points differential output, open collector output and push-pull output three, the transfer mode signal must take into account the frequency converter pg card interface, so choosing the right card model or set reasonable pg.

Encoder Classification

The encoder is generally divided into incremental and absolute, they kept the biggest difference: in the incremental encoder, the position is the number of pulses from the zero position mark the beginning of the calculation determined, and the absolute encoder position by reading the output code determined. In the circle, the output code reading each location is unique; therefore, when the power is turned off, the absolute encoder is not separated from the actual location. If the power is turned on again, the location is the current reading is still effective; unlike incremental encoders, as necessary to find the zero mark.

Now the encoder manufacturers are whole series, usually proprietary, dedicated elevator type encoder, machine-specific encoder, servo motor special type encoder, and the encoder are intelligent, there are various parallel interface can communicate with other devices.

The encoder is a device the angular displacement or linear displacement into electrical signals. The former became the code disc, the latter known as the yardstick. In accordance with the readout mode encoder can be divided into contact and non-contact two. Contact output using brush, a brush contact conductive region or insulating region to represent the status code is "1" or "0"; the acceptance of non-contact sensor is a photosensitive element or magnetic element, when using a photosensitive element photic zone and opaque regions to indicate the status code is "1" or "0."

An encoder according to the principle can be divided into incremental and absolute categories. Incremental encoder displacement is converted into periodic electrical signals, then converted into electrical signals that count pulse represents the magnitude of displacement by the number of pulses. Absolute encoders at each position corresponding to a certain digital code, so its value is only shown with the beginning and end of the measurement, but not to the middle of the process measurement.

Incremental rotary encoder rotates the output pulse by counting device to know its position when the encoder does not move or power outage, counting on internal memory to remember the location of the device. Thus, when the power failure, the encoder does not have any movement, when work calls, encoder output pulse process, it can not have lost the pulse interference, otherwise, it will count zero offset memory device, and this bias the amount of shift is no way to know, to know only after the wrong production results appear. The solution is to increase the reference point, the encoder after every reference point, the reference position correction position count into the memory device. In the previous reference point, it is not guarantee the accuracy of the location. To this end, every operation in the industrial in there to go first reference point, turn the change and other methods. Such encoder is a mechanical encoder position determined, it is not a power outage, the impact of interference.

Absolute encoder is determined by the mechanical position of the uniqueness of each location, without having to remember it, no need to find a reference point, and would not have to count, when you need to know where and when to go read its position. Thus, interference encoder properties, has greatly enhanced the reliability of the data.

Since the absolute encoder positioning clearly superior to incremental encoder, has been increasingly used in industrial targeting. Absolute encoders because of its high accuracy, the output bit more, if you still use parallel outputs, each of which an output signal of the need to ensure a good connection, but also for more complex conditions isolation, the number of multi-core cable connection, thereby inconvenience and reduced reliability, and therefore, the absolute encoder multi-bit output type, generally use the serial output or bus output, the German production of absolute encoder is the most common serial output SSI (synchronous serial line output).

Multi-turn absolute encoder. Encoder manufacturers use mechanical timepiece gear principle, when the center of the code wheel rotates through another set of code wheel gear (or sets of gear, multiple sets of code disk), single-turn encoder, based on the additional number of turns coding, to expand the measurement range of the encoder, absolute encoder so called multi-turn absolute encoder, it is also determined by the mechanical position encoders, position encoding each unique non-repetition, without memory. Another advantage of the multi-turn encoder is due to the large measurement range, the actual use is often more affluent, so that the installation of unnecessary hard to find zero, as a starting point to an intermediate position on it, and greatly simplifies the installation difficult. Multi-turn absolute encoder positioning advantage in length significantly, it has been increasingly used in industrial targeting.

Previous：Photoelectric encoder working principles
Next：The distinction between the incremental encoder and absolute encoder