Abstract: In a method for detecting an encoder material reading error, at least one of a sensor and an encoder material is slewed with respect to each other. Markers on the encoder material are detected with the sensor as at least one of the sensor and the encoder material is slewed with respect to each other to obtain position vs. time data of the sensor with respect to the encoder material. The position vs. time data is analyzed to determine whether a speed at which at least one of the sensor and the encoder material travels with respect to each other fell below a predetermined threshold. In addition, a determination that an encoder material reading error has occurred is made in response to a determination that the speed fell below the predetermined threshold.