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Anti-interference ability of encoder advantage!

Changchun Rongde Optics Co.,Ltd.   Release time:2019-01-02   Browse:720

An encoder is a rotary sensor that converts rotational displacement into a series of digital pulse signals that can be used to control angular displacement. It can also be used to measure linear displacement if the encoder is combined with a gear bar or a screw.

After the encoder generates an electrical signal, it is processed by a digital control CNC, a programmable logic controller PLC, a control system, and the like. These sensors are mainly used in the following areas: machine tools, material processing, motor feedback systems, and measurement and control equipment. The angular displacement conversion in the ELTRA encoder uses the principle of photoelectric scanning. The reading system is based on the rotation of a radial indexing disk consisting of alternating light transmissive windows and opaque windows. The system is illuminated entirely by an infrared source such that light projects the image on the dish onto the surface of the receiver, which is covered by a layer of grating, called a collimator, which has the same window as the disc. The job of the receiver is to sense the change in light produced by the rotation of the disc and then convert the change in light into a corresponding electrical change. In general, the rotary encoder can also obtain a speed signal that is fed back to the frequency converter to adjust the output data of the frequency converter. Fault phenomenon: 1. When the rotary encoder is bad (no output), the inverter can not work normally, the running speed is very slow, and the inverter protects for a while, the display shows “PG disconnected”... the joint action can work. To raise the electrical signal to a higher level and produce a square wave pulse without any interference, this must be handled by an electronic circuit. The connection between the encoder pg wiring and the parameter vector inverter and the encoder pg must correspond to the model of the encoder pg. In general, the encoder pg model is divided into three types: differential output, open collector output and push-pull output. The signal transmission mode must take into account the interface of the inverter pg card, so choose the appropriate pg card model or set it properly.

Encoders are generally divided into incremental and absolute types. They have the biggest difference: in the case of incremental encoders, the position is determined by the number of pulses calculated from the zero mark, and the position of the absolute encoder is Determined by the reading of the output code. In one lap, the output code reading for each position is unique; therefore, when the power is turned off, the absolute encoder is not separated from the actual position. If the power is turned back on, the position reading is still current and valid; unlike the incremental encoder, it is necessary to look for the zero mark.

Encoder manufacturers produce a full range of products, generally dedicated, such as elevator-specific encoders, machine-specific encoders, servo-motor-specific encoders, etc., and the encoders are intelligent, with various parallel The interface can communicate with other devices.

An encoder is a device that converts an angular displacement or a linear displacement into an electrical signal. The former becomes the code wheel and the latter is called the code ruler. According to the readout mode, the encoder can be divided into contact type and non-contact type. The contact type uses a brush output, and a brush contacts the conductive area or the insulating area to indicate whether the state of the code is "1" or "0"; the non-contact receiving sensitive element is a photosensitive element or a magnetic sensitive element, and when the photosensitive element is used The light transmissive area and the opaque area indicate whether the state of the code is "1" or "0".

According to the working principle, the encoder can be divided into two types: incremental and absolute. The incremental encoder converts the displacement into a periodic electrical signal, which is then converted into a counting pulse, and the number of pulses is used to represent the magnitude of the displacement. Each position of the absolute encoder corresponds to a certain digital code, so its indication is only related to the start and end positions of the measurement, regardless of the intermediate process of the measurement.

The rotary incremental encoder outputs a pulse when it is rotated, and its position is known by the counting device. When the encoder is not moving or power is off, the internal memory of the counting device is used to remember the position. In this way, when the power is off, the encoder can't have any movement. When the caller works, the encoder can not interrupt and lose the pulse during the output pulse. Otherwise, the zero point of the counting device will shift, and this bias will occur. The amount of shift is unknown, and only the wrong production result can be known. The solution is to increase the reference point, and the encoder corrects the reference position into the memory position of the counting device every time the encoder passes the reference point. Before the reference point, the accuracy of the position cannot be guaranteed. For this reason, in the industrial control, there are methods such as finding a reference point for each operation, and starting to change the zero. Such an encoder is determined by the mechanical position of the code wheel and is immune to power outages and interference.

Absolute encoder uniqueness of each position determined by the mechanical position, it does not need to remember, no need to find a reference point, and do not have to count all the time, when you need to know the position, when to read its position. In this way, the anti-jamming characteristics of the encoder and the reliability of the data are greatly improved.

Since absolute encoders are significantly superior to incremental encoders in positioning, they have been increasingly used in industrial positioning. Due to its high precision, the absolute encoder has a large number of output bits. If parallel output is still used, each output signal must ensure that the connection is good, and it is isolated for more complicated working conditions, and the number of connecting cable cores is large. It brings a lot of inconvenience and reduces reliability. Therefore, the absolute encoder is a serial output or a bus type output in the multi-digit output type. The most commonly used serial output of the absolute encoder produced in Germany is SSI (synchronous string). Line output).



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