“One accurate measurement is worth a thousand expert opinions,” said Grace Murray Hopper, widely recognized as a true pioneer of computing. This could be faulted by the overly literal as an idea that may not always hold true. But for the workforce in manufacturing, it is certainly of paramount importance.
Proper knowledge of, and skills in, measurement techniques are required to properly construct engineering works and structures. Lack of knowledge and miscalculations can result in catastrophic events. Take, for example, the Great Kersten Blunder, in which software controlling a space probe on course for Venus used “24.5” instead of “25.4” to convert millimeters to inches. The error meant that the probe missed its target planet completely, losing $2 billion worth of technology. The eponymous Kersten was the programmer who made the error.
No two objects are exactly alike. All things differ by some degree. Some variation may be obvious, but other variation may require precise measuring equipment to detect. As measurements increase in precision, the differences between parts become greater and greater until ultimately none of the parts would be the same. As the level of comparison becomes more precise, the concept that no two objects are exactly alike is realized.
All manufactured parts exhibit this type of variation. It is the concept of variation that forms the basis of probability, statistics, and quality control. For example, a piston must fit exactly into the cylinder bore for an engine to work properly. A visual check of the diameters may reveal no differences between these two components. However, once the diameter is measured with a steel scale, some differences may be found. Then, if the measurements are taken using a micrometer, a greater variation will likely be detected. Each level of comparison, or method of measurement, reveals a greater degree of variation.
A product that does not conform to its design specifications will not properly perform its intended function. Manufacturing engineers will use design drawings and specifications to develop their manufacturing specifications and arrange the operations necessary to produce the product. This includes the floor layout, machinery, test sets, tools, and other equipment.
In the engineering and science professions, measurement, accuracy, and precision are of paramount importance, as they are the basis of what we do and how we do it.
Measurement is fundamental to control, to improvement, and to verification. We measure success and failure, and often base our actions on judgments that arise from measurement. It is far more powerful than just a set of numbers on a scale, and by exploiting the value of measurement we, as engineers, can achieve more.
Take better measurements by:
- Using the International System of Units (SI), whenever possible
- Ensuring the measurement techniques result in valid readings
- Understanding core concepts such as precision, accuracy, uncertainty, repeatability and reproducibility, acceptance criteria (such as tolerance), traceability, and calibration
- Estimating the overall uncertainty of a group of measurements
- Applying geometric tolerances
To find out more about the science of measurement and the national and international standards associated with it, or to refresh your knowledge of measurement concepts in general, click the button below.