This paper presents an inductosyn angle measurement system based on AD2S80 resolver-to-digital converter. The reason
why the reference signal is not orthogonal with the excitation signal is analyzed, and a mathematical model is established
for the error. The correctness of the error model is proved by measuring data. The error that the reference signal not be
orthogonal with the stimulating magnetism signal causes the quadratic sine harmonic error which has a significant effect
on the precision of the angle measurement system.