The Technical Research Of Incremental Of Rotary Encoder Based On Giant Magneto-Resistance

The Rotary Encoder is commonly used as a measurement of rotating object’s angle and speed, it is widely used in the fields of Automation and control, metallurgy, wind power, office supplies and so on. The Rotary Encoder can be classified as contactless encoder, photoelectric encoder and magnetic encoder by principle. The method of contactless encoder is simple, but is heavy, and the accuracy of measurement is low, because it belongs to contact measurement, the device is very easy to damage; The photoelectric encoder belongs to non-contact encoder, it has high precision, but its cost is high, and sensitive to rain and fog weather. A magnetic encoder based on magnetoresistive effect, compared with the photoelectric and contactless encoder, it has the advantages of small size, simple structure, and good resisitance to environment.This article is studied about the key technologies of rotary encoder based on the GMR sensor chip, and make the design of hardware circuit and structure of incremental magnetic rotary encoder., the magnetic sensor, signal processing circuit and structure, is used to measure motor’s speed, direction and displacement. The spin valve GMR sensor is a new sensor chip, its’internal structure is the Wheatstone bridge, which can convert the magnetic field information into an analog differential voltage output. It has high sensitivity, perfect linearity, small package size, is suitable for the production of the magnetic encoder, and can detect accurately the rotation speed and displacement of motor.First, This article introduce the GMR principle, and the structure of the valve GMR chip, mainly describes the relevant principle of incremental magnetic rotary encoder, then make the analysis of multi-pole magnet’s magnetic field, and use the Ansoft Maxwell software to simulate it.Then, article describes the detailed hardware circuit and structure designs and use the PSpice to simulate the hardware circuits, including some signal processing circuits of amplifier, filter, comparator. In order to meet the use requirements of magnetic encoder, put forward the design of strcture. To measure the performance of the magnetic encoder, building a magnetic sensor processing circuit of verification platform, it can measure the output signal. The verification platform including the data acquisition and display module.After finishing the debugging of the encoder, then make experiences. The contents of experience include the source waveform test, the signal processing circuit waveform test and the test about the magnetic sensor validation platform. The results of experience shows that the encoder meets the design’s requirements.