The Research Of Visual Inspection System For Glass Thermometer Indication

Glass thermometer in modern measuring technology is still one of the indispensable toolsfor temperature measurement, that is widely used particularly in petroleum, chemical industry,shipbuilding, machinery and other industries, so the use of the thermometer quantity is stillbigger. The thermometer in a certain period of time to re-certification, in order to ensureaccurate and reliable. Usually the thermometer verification work is handed over to the localdepartment of metrological verification to complete, therefore, for the metrologicalverification department, the verification of the thermometer quantity is relatively large, andverify a thermometer need a longer time, resulting in greater labor intensity for verifypersonnel. Although the test personnel can be numerically to read the thermometer throughreading telescope, but still rely on the staff of the visual reading, reading and imagingtelescope is inverted, such a reading error is inevitable.resulting in labor intensity testpersonnel larger. Although verification personnel can through the telescope to read the value ofthermometer, but still rely on personnel to read,and the reading by personnel is inverted, sothat the reading error is inevitable.To solve the above problem, and cut down the work intensity of verification personnel, atthe same time reduce the reading error, this paper according to the structural characteristics ofglass thermometer, combined with the actual working conditions of verification thermometer,a visual inspection system for glass thermometer indication is developed. The systemaccording to the characteristics of the thermometer transverse in the image, using grayminimum value method, horizontal projection method to find and extract the thermometerimage, according to the characteristics of vertical scale line in the image, using templatebinarization processing the thermometer image, after processing thermometer image,refinement and analysis it gets the scale line position, according to the characteristic of liquidcolumn in the thermometer image, using template method, expansion algorithm and corrosionalgorithm, as well as the level hough transform get liquid stigma position, and then thecharacter images on the thermometer is obtained through the connected domain detection andprojection analysis, and get the position of the long scale line corresponding to the character.and ultimately makes the system can correctly read thermometer indication. Finally the system can correctly read the thermometer indication.Through many experiments to verify the system construct and algorithms. Experimentsshow that this visual inspection system for glass thermometer indication has good performance,can make sure that the acquired image real-time and clear, and the thermometer readingsalgorithm can overcome the effects of image brightness non-uniformity, adapt to theenvironment ability is strong, and perform fast, stable running, can meet the needs ofverification personnel to the device.