Definitions Of Accuracy, Precision In Manufacturing
Standardized measurement tools are very important instruments in quality control departments in manufacturing sites. There must be very detailed measurement section at production facilities to measure the produced parts to see whether they are inside the dimensions or tolerances defined before. In this article, we will explain the general measurement instruments that are used in industry, and you will find out the general classification and the general definitions of these tools.
Measurement instruments can be in angular or linear scales. You will find out the general linear measurement instruments in this article. Linear measurement instruments are classified into two categories as; graduated and non-graduated.
In graduated measurement devices, there some kinds of standardized scaling markings. In measurement process with these graduated measurement devices, comparisons are generaly made with these scaling markings with object that is being measured. One of the biggest example of this category og measurement devices is ruler. As you know, there are scaling markings on them such as centimeters, milimeters etc. There are varios kinds of rulers avaliable in metric scale or US scale.
At non-graduated measurement devices, there are no scaling markings. There is a standardized physical dimensions that has known dimension and tolerance. Comparison is made with that physical dimension and the object that is being measured. The biggest example of that category of measurement devices is non-graduated calipers. In most simple example of calipers as above, there is a geometry that includes two of jaws that hinged themselves, and there is a space between the jaw at the tip of them. This space is used for non-graduated measurement of objects.
Also there are graduated calipers to measure the outside or inside diameters of different objects. There are scaling markings on these graduated calipers to measure diameters. Slide calipers has two of feature to measure inside diameters and outside diamenters with one jaw construction.
Vernier caliper also very important graduated measurement tools. Difference of the vernier calipers compared to simple slide calipers, there is a vernier scaling to scale the decimal side of the dimensions.
The most sensitive graduated measurements device is micrometer. There are three types of micrometers generally as; external micrometers that external dimensions or diameters can be measured, internal micrometer that internal dimensions or diameters can be measured and the depth micrometers that the depths of various geometrical shapes can be measured. Accuracy can be much more superior if a digital screen is used as in example above.
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Source of images: Fundamentals of modern manufacturing.