in the presence of interference. By processing binary image
using the probabilistic Hough transform
center of rotation of a pointer is determined by any pointer of two different positions
according to fixed features of coordinates of rotation center
when there is interference in the image
through the relationship between all lines dected and the intersection point of the zero scale pointer of the instrument and the size of the coordinate of rotation center
the straight line which represents pointer correctly is determined. The stability of instrument detection is improved
and the validity and correctness of the method are proved by the experiment of the ammeter.