How does sin cos encoder work?
It is similar to quadrature encoder with A and B signal that are shifted 90 degress, except that sic/cos outputs a sine and cosine waveform of signal. The electronic part is then splitted in two main circuits:
1. A comparator with hysetersis converts sin and cos signal to quadrature signal and then you have a counter that counts up/downn like those with quadrature encoder.
2. The position in between two quadrature pulses can be determined by calulation of sin and cos signal: tan(phi) = sin(phi)/cos(phi) , therefore phi = atan(sin_signal / cos_signal).
You get a better resolution in between quadrature pulses, very useful when it running at low speed, since the velocity is determined by diferentiating the encoder position. You may soon understand that if signal has low frequency, then you won't get any good value for the speed calculation. That's why sin/cos are better performance.