Measurement is the act of determining a target’s weight, length, capacity, size, or other physical dimensions. It’s easy to mistake the term “measurement” for terms such as “quantify” or “calculate” but as a rule of thumb, just think of measurement as a single action within the term instrumentation. To gain a full understanding of this concept we’ll look at the definitions of both measurement and instrumentation:
Instrumentation is a collective term for measuring instruments used for indicating, measuring and recording physical quantities. Measurement – to show measured results using values and symbols
Be mindful that the act of measurement is performed when an individual uses measuring tools or a measurement system or Instrumentation. For the purposes of this article we will examine measurement in terms of inspection, manufacturing, and design of machine components.
Historically, our ability to measure has helped humanity to innovate and evolve in multiple areas of development such as technology, science, trade, and quantitative research. Throughout history, there have been hundreds of measuring systems that existed for every type of field and occupation. For example, a shoe maker would have a different measuring system then a baker just as a stone cutter would have a different measuring system then craftsmen.
Understanding the difference between Measurement and Inspection
Inspection is a reference to the values achieved through measurement with the available references on hand while determining whether a product is acceptable. Measurement refers to the number of results found through the use of measurement tools. In most cases, there is no need to use the definitions of measurement and inspection separately. However, it’s still a good idea to understand that there is indeed a difference between the two. Let’s look at an example. When using a ruler as a tool to determine the length of an object, you can make the statement that “the measurement is too long or too short.” Another way to state this same statement would be “based on the value found from the use of a ruler (the tool of measurement), it can be said that this value is either longer or shorter than the length of interest.” As previously stated, in most cases there’s no need to separate the definitions of measurement and inspection. Simply understanding the difference is sufficient for most situations.
There are two types of measurement systems: direct measurement and indirect measurement.
Direct measurements are ascertained by using a system or tool to directly read the height, length or any other aspect of an object to determine its measurement. The concept of direct measurement allows a measurement to be known as it is, however errors may ensue depending upon the skill of the person performing the measurement. Examples of direct measurements include measuring your height by using a measuring tape, determining the temperature of your oven through the use of a thermometer, and measuring the length of your morning exercise through the use of a stopwatch.
In the world of physics, one of the more common examples of direct measurement is current. When attempting to measure the current flowing through a wire, you use an ammeter connected to the circuit to directly measure it. This method is considered a direct measurement because the tool being utilized, the ammeter, measures the current in the wire without the need to know any information prior to the measurement.
Direct measurements may be what you are most familiar with, but indirect measurements have their uses. Indirect measurements occur when you take the measurement of one unit/object and convert it so that it matches the characteristics of something else. The concept of indirect measurement may be a bit difficult for some people to grasp due to the fact that many people don’t have a use for it in their everyday lives. Let’s look at an example. If you were to take a dial gauge to measure the height difference between a measurement target and a gauge block you would then, using the indirect measuring system, use your calculation to indirectly estimate the target’s height.