Metrology is defined as the science of measurements or the precision of measurements. Even it can be defined as the accuracy of measurements.
The science which is dealing with measurements and their conditions is called measurement science or metrology.
In this article, we will discuss Methods, Standards, and Instruments for Linear Measurements.
But before that, we should have to know about Precision and Accuracy.
It is the repeatability or reproducibility of measurements.
Whatever the number of times a given dimension is measured by using given measuring equipment if the same dimension is obtained every time called repeatability or reproducibility of measurements.
Whenever only one measuring equipment is involved in the measurement of the dimensions, the Precision is important.
The nearness to the true value is called accuracy.
The precise measurements made by using standard measuring equipment or non-errored measuring equipment is called Accuracy of measurements.
Whenever more than one measuring equipment is involved in measuring dimensions, accuracy is important.
The measurement of lengths, thickness, diameter, and heights including external and internal measurements is called Linear measurement.
They are 3 standards used for Linear Measurements and are as follows:
The explanation is as follows.
The detailed explanation for the Methods of linear measurements is as follows.
If the lines of measuring equipment are coincided with the ends of a measurand, by counting the number of lines in between the coincidence lines and multiplied by one scale division, the dimension of the component will be obtained called line standard measurement.
For Example, Scale, tape, etc.
No.of lines = 95-32 = 63.
L= n*one scale division
= 63*1
= 63
If ends of measuring equipment are coincided with the ends of the measurand and by adding the individual dimensions of the end standards used. The dimensions of the component will be obtained called End Standard Measurement.
For example, Slip gauges, end bars, etc.
If the ends of measuring equipment are coincided with the ends of a measurand and by using the lines if the dimension of the component is obtained called as Line and End standard method of measurement.
For example, Vernier Caliper, Screwgauge, etc.
A Slip gauge is specified by using its height only.
They are made by using high carbon steel as a material.
The top and bottom surfaces of the slip gauge are lapped with other slip gauges so as to construct a given height to measure the angle of the given specimen by sine bar and for that, a final machining operation is to be done on the slip gauges to get a very high degree of surface finish.
Building a given dimension using more than one slip gauge by forming a temporary bond between the slip gauge surfaces is called the Wringing of slip gauges.
Atoms present on the highly polished surface are more active to share the energy with the other atoms.
Therefore, when two slip gauge surfaces are contacting and placed at 90° and rotated with the application of the little amount of force so that the temporary Bond formation is taking place between the two slip gauge surfaces. This is called as wringing of slip gauges.
The direct measuring instrument is divided into two types.
Therefore, this is the detailed information about the Linear Measurements. If you have any doubts, feel free to ask in the comments section.
Mohammed Shafi is the founder, managing editor, and primary author of Mechanical E-Notes. He is an Assistant Professor (Department of Mechanical Engineering) at the Sreenidhi Institute of Science and Technology. He has a 6 years of vast experience in design, research, and data analysis. Shafi has co-authored two journals 1. Dynamic and Fatigue Analysis on Tillage Equipment 2. Welding Procedure and Testing Analysis on Mixing and Nodulizing Drum.
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