指针式压力表自动计量校准系统

目前，指针式压力表常采用影像法进行计量校准，但在计量过程中存在压力表指针难分割、背景难分离和识别准确率低等问题，为解决上述问题，结合不同规格压力表表盘的外观尺寸，对压力表自动计量校准系统进行研究。首先，根据工业相机视野范围内压力表表盘外形尺寸，自动判断相机与压力表之间最佳工作距离；其次，利用图像边缘梯度值评价图像清晰度，自动完成相机对焦；最后，采用极坐标转换方法实现刻度线定位、指针提取、实时读数等功能。测试结果表明，该系统适用于外壳直径为40，60，100，150，200，250 mm的指针式压力表计量校准。

Automatic measurement and calibration system of pointer pressure gauge

At present, pointer pressure gauges are often calibrated using image method, but there are some problems in the measurement process, such as difficult to segment the pointer of the pressure gauge, difficult to separate the background and low recognition accuracy. In order to solve the above problems, combined with the appearance size of the pressure gauge dial of different specifications, the automatic measurement and calibration system of the pressure gauge is studied. Firstly, the optimal working distance between the camera and the pressure gauge is automatically determined according to the external dimension of the pressure gauge dial within the field of view of the industrial camera. Secondly, the image sharpness is evaluated by the image edge gradient value, and the camera focusing is automatically completed. Finally, the polar coordinate transformation method is used to realize the functions of scale line positioning, pointer extraction, real-time reading and so on. The test results show that the system is suitable for the calibration of pointer pressure gauges with shell diameters of 40, 60, 100, 150, 200 and 250 mm.