Reading method, reading device and reading system of pointer type industrial instrument

The invention discloses a reading method, a reading device and a reading system of a pointer type industrial instrument. The reading method comprises a reading step and a calibration step, wherein the reading step comprises a step S1.1, a step S1.2, a step S1.3 and a step S1.4. Obtaining a picture of the industrial instrument, measuring range information of the industrial instrument and a radius; processing the picture to determine the width size of the industrial instrument in the picture, the scale coordinate of each scale, the pointer coordinate of the head of the pointer and the circle center coordinate of the scale line; determining the moving arc length of the head rotating from the starting scale of the scale line to the pointer coordinate around the circle center; and determining the relative position between the head of the pointer and the scale line, and determining the reading of the industrial instrument in the picture according to the relative position and the range information. Therefore, the im