The Sin/Cos encoder is an incremental encoder that outputssin/cos analog signal, different from the common incremental encoder outputs an AB orthogonal square wave pulse signal. The Sin-Cos encoder outputs two sine waves with a phase difference of 90 °, so it is called Sin-Cos encoder.
The following figure shows the output signal of the square wave encoder.
In order to improve the resolution of incremental encoders, sometimes quadruple frequency is also used, which calculates both the rising edge and the falling edge, so that each cycle can be subdivided into four parts.
In order to further improve the resolution of the encoder, it is necessary to increase the density of the encoder's code disk lines. However, the resolution of the square wave incremental encoder is constrained by two factors; firstly it is limited by the size of the encoder. For encoders with an outer diameter of 60mm, the physical marking generally does not exceed 10000 lines. Secondly the output frequency is directly proportional to the speed and resolution of the encoder. Higher resolution means higher output frequency, which cannot achieve long-distance transmission.
The Sin/Cos encoder can solve this problem. Although the number of sine and cosine cycles (physical resolution) may not seem very high, each sine and cosine cycle can be subdivided into many steps through arctangent interpolation operation, thus it can achieve very high resolution.
X = Arctan（Sin（X）/Cos（X））
Based on the real-time amplitude of sine and cosine signals, the exact position (electrical angle) of the encoder within this sine and cosine period can be determined through Arctan Calculator. Depending on the resolution of analog-to-digital AD conversion and the quality of sine and cosine signals, each sine and cosine period can usually be subdivided into 212 to 214 steps. The number of sine and cosine cycles each circle of the encoder, multiplied by the number of subdivision steps per sine and cosine cycle, we’ll get the total resolution of each circle of the encoder. It should be noted that the resolution after subdivision is calculated by the controller or driver through input circuit processing, and is not directly output by the encoder.
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