Research Of Verification System For Pointer Pressure Gauge Based On Machine Vision

Pointer pressure gauge is widely used in industry and scientific research field, it has a simple structure, and it is easy to install, less susceptible to magnetic interference,and it has high stability and low price. In recent years, domestic and international recognition of pointer pressure gauge readings based on machine vision technology has a number of studies, to a certain extent, it gradually replaced the manual reading, but there are still some problems :(1) When collecting image, background will affect readings, currently there are some researches for this effect: 1) Through finding the coordinates of the vertices pointer 3 times,according to the principle of three points determine a circle, fit the dial general contour, and then separate dial from background, but this method requires a pointer in three different locations before they can complete the positioning of the dial, it lost the meaning of real-time verification. 2) Using threshold methods, as a result of threshold segmentation derived measurement accuracy in most cases is determined by the selected threshold when dividing, if the gray value of the background is close to the gray value of dial, that is, in the context of a very bright background, no matter how to set the threshold, it is difficult to separate the dial from the background.(2) Since the gauge size is different, it needs to adjust the camera’s working distance or focal length to make the dial completely imaging in the field of view, it takes long time to adjust.(3) Pressure gauge in industry test is according to national standard test procedures, using a pressure gauge pump to add pressure to each test point, then execute tapping test, return test and other operations in each test point, read each point data in order and fill the data in gauge test records, but pressure gauge test has large data, it still need manually filling in,it spends a lot of time.To solve the above problems, a set of pointer pressure gauge verification system based on machine vision technology is developed:(1) This article uses image segmentation based on edge extraction, according to the position of the dial profile features and shape features, locate the dial contour, and segmente dial from the entire image, then overcome the impact of the background on the dial readings;(2) Select fixed focus lens according to the gauge size and working distance, to ensure maximum diameter gauge in the field of view and imaging completely and clearly, fix the camera through experimental bracket, verify gauges in different diameters by adjusting the height roughly, it saves time.(3) Use Microsoft Visual Studio 2010 to call Microsoft Word 2007 database, then the system can read and write local data in word documents, ultimately the gauge test data is automatically written to the national standard test records, and it saves the step of artificial copying data, and improve efficiency.After repeated experiments, it shows that the system can quickly and accurately identify the gauge readings and can verify precision pressure gauge of accuracy class 0.4, and can test the pointer pressure gauge of different diameters, and it can well adapt to the complex and variable working environment.