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# Three skills of image measuring instrument in measuring angle

by：Sinowon     2021-05-05
The three skills of image measuring instrument in measuring angle. Tip 1: Small regression linear error. In the process of measuring the arc of the product viewpoint, the repeatability is usually very poor. One person uses the same method, but the error reaches 0.5 degrees. This is a common situation. In many impression measurement software today, the straight line collection is silently divided into two points. For parts with good regularity and straightness, there will not be too many errors in the viewpoint measurement, but for parts with poor straightness and a lot of burrs, the method of collecting straight lines at two points brings many errors and repeat accuracy Nor is it satisfactory. The repeatability of repeated measurements with such a straight line is definitely not ideal. If we use a multi-point regression line to confirm the two ends of the viewpoint, the resulting line is closer to reality. Tip 2: Keeping the edge of the measured workpiece not only reduces the error, but also reduces the measurement error, and greatly improves the repeatability. Collecting as many straight lines as possible affects the measuring instrument due to the limited screen display, and the magnification is generally in the range of 0.7 to 4.5, 28X to 180X. In fact, the scale of the workpiece displayed on the screen is only a few millimeters. Many testers only Only get used to the display part of the screen when testing the collection points and line elements. If there is an error in the collected points, the shorter the line segment, the greater the error of the measured viewpoint value, and the longer the line segment, the smaller the error of the measured viewpoint value. The theoretical viewpoint is 30 degrees, and the sampling point error is 0.25 mm. We can clearly see the effect of the length of the line segment on the measured value. Therefore, when measuring the viewpoint, we should collect the line at both ends of the point and the longer the viewing time, the better. If the screen looks too small, we can move the workbench, By selecting a point at the starting point of the line where the viewpoint is located, and then selecting a point at the end point, the viewpoint error will be greatly reduced.

Tip 3: Expand the magnification as much as possible. For many mechanical parts, the measured angle of the edge is very short, only 2mm~3mm, such as chamfering the shaft part. If we also use a smaller lens 0.7 or 1 to measure a point, the workpiece imaging will only be 48mm~120mm, and the deviation of this point will have a great impact on the measured value. If you switch to 3 or 4 magnification, the workpiece imaging can reach 240mm ~480mm, it is easier to observe the true situation of the edge of the image, and the deviation of the excavation point can be reduced. However, this method also brings a lot of inconvenience. The graphics are too large and the display window can only display a small part. This should not be a problem for inspectors who are skilled in image measuring instruments and pursuing high-precision quality control.

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