The difference between incremental absolute encoder

The difference between incremental absolute encoder

The incremental encoder converts the displacement into a periodic electrical signal, the electrical signal is converted into a counting pulse. The number of pulses indicates the magnitude of the displacement; in an absolute encoder, each position corresponds to a certain digital code, which represents the value It is only related to the start end positions of the measurement, has nothing to do with the middle process of the measurement.

Why is an encoder installed in the motor?

When using an incremental encoder, the position is determined by the number of pulses counted the zero mark, while the position of an absolute encoder is determined by the reading of the output code. In a circle, the reading of the output code of each position is unique; 　 Therefore, when the power is disconnected, the absolute encoder is separated the actual position. If the power is turned on again, the position reading is still current valid.

Parameters to be determined when the encoder is selected

Installation size, outlet method protection. Including two aspects: positioning spigot, shaft diameter, installation hole position, cable outlet method. Installation space volume; whether the working environment protection level meets the requirements.

Resolution. The number of pulses output per revolution when the encoder is working.

Encoder output electrical interface. The common ones are push-pull output type, voltage output, line drive output type. Its output mode should match the interface circuit of its control system.

Encoders commonly used in motors

Incremental encoder

Directly use the photoelectric conversion principle to output three groups of square wave pulses A, B Z phases. The A B pulses have a phase difference of 90o, which can easily determine the direction of rotation; each pulse of the Z phase is used for reference point positioning. Its advantages: the principle structure is simple, the average mechanical life can be more than tens of thousands of hours, the anti-interference ability is strong, the reliability is high, it is suitable for long-distance transmission. Disadvantage: unable to output absolute position information of shaft rotation.

Absolute value encoder

Sensors that directly output digital quantities. There are a number of concentric code tracks along the radial direction on the sensor's circular code disc. Each track consists of light-transmissive opaque sectors. The number of sectors of adjacent code channels is doubled. , The number of code channels on the code disc is the number of binary digits. On one side of the code disc is the light source, the other side corresponds to each code track. There is a photosensitive element; when the code disc is in different positions, each photosensitive element Whether it is illuminated , the corresponding level signal is converted to form a binary number.

The characteristic of this kind of encoder is that no counter is needed, a fixed digital code corresponding to the position can be read out at any position of the shaft. Obviously, the more code channels, the higher the resolution. For an encoder with N-bit binary resolution, the code disk must have N code channels. At present, there are 16-bit absolute encoder products in China.

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 rotary motion sensors, linear displacement sensors, object recognition sensors, laser rangefinders, process control measurement Class 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 to meet different Different needs of customers.