This article addresses the problem that installation errors in the encoder during the detection process result in the generation of installation angular errors. It analyzes the relationship of installation angular errors, rotation angles, and measurement errors. It establishes a model for determining the installation angular errors caused by misalignment in the non-concentric detection system. Through experiments, the impact of three different levels of installation angular errors, namely$ 0^{\circ}\;\mathit{\mathrm{to}}\;0.002^{\circ} $, $ 0.1^{\circ}\;\mathrm{to}\;0.102^{\circ} $, and $ 0.2^{\circ}\;\mathrm{to}\;0.202^{\circ} $, on the static and dynamic accuracy of the detected encoder was analyzed. Three distinct experimental results were obtained. The experimental findings indicate that during encoder detection, initial controllable installation errors within the specified range meet the technical specifications. However, exceeding this safe range of installation errors would cause the deviation of the encoder's detection performance from the standard. The conclusions drawn from the experiments hold importance in enhancing the accuracy and reliability of encoder detection technology. They also provide valuable reference points for future research aimed at improving encoder detection accuracy.