Pointer Temperature and Humidity Meter Detection Based on Machine Vision

Lei Geng, Wenke Li, Jiangtao Xi, Yanbei Liu


A new method is proposed to achieve the accurate segmentation and reading of different types of pointer temperature and humidity instruments. The Canny edge detection operator is applied to detect edges of the meter gray image, and the scale line distribution arc and scale lines is obtained according to distribution characteristics of the scale line. The pointer is fitted by concentric method within the radius of the arc. OCR identifies the scale value of the dial, and then determines the corresponding reading number of each scale line and dividing value by mapping relation. Three different types of meters are used to detect, and experiments results demonstrate that the proposed method can achieve accurate segmentation of pointer and scales, as well as accurately calculate the readings of instrument.


temperature and humidity meter; gaussian filter; edge detection; region of interest; canny operator; extracting circular arc; optical character recognition.

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