What is Accuracy?
Accuracy refers to the closeness of a measured dimension to a standard or known value. It is identified as the difference between the measurement of a dimension and the accepted value for that dimension from a trusted external source or the percentage by which the two values differ.
What is Repeatibilty?
Also known as precision, it is defined as the spread of values obtained with repeated measurements on a given specimen using a specific measuring instrument by a specific operator under given lab environment. It is important to specify these variables and conditions when quoting a precision value. Normally, when a large number of measurements are done, the spread in measured values is caused due to randomness so that the a multiple of the RMS of the measured deviations about the mean can be taken as the precision value.
What is Traceability?
In 1962, the US department of defense was the first to outline the guidelines of industrial traceability. The guideline clearly describes that the shop floor measuring and testing instruments shall be calibrated utilizing the reference standards which by themselves have the calibration being traceable to a national standard. Thus the traceability relates individual measurement results to national standards or nationally accepted measurement systems through an unbroken chain of comparisons. The emphasis on traceability is important because it enables measurement consistency from laboratory to laboratory in a logical and consistent manner.
What is Edge Detection?
Image processing technique for finding the boundaries of objects within images. It works by detecting the discontinuities in brightness. By using it features like corners, lines and curves can be extracted from an image for dimensional measurement uses. The four steps of edge detection are smoothing, enhancement, detection and localization. Firstly, the noise is suppressed in the image, without destroying the true edges, then a filter is applied to enhance the quality of edges. The next step is determining which pixels should be discarded as noise and which should be retained . The last step is determining the exact location of the edge.