What is Measurement?
Measurement is about determining the quantifiable attributes of a target object. Examples of these attributes include:
The following sections explain more about what measurement is – and isn’t.
Why is measurement misunderstood?
Sometimes, people use the term “measure” instead of “calculate” or “quantify”. All these terms are related, but they’re not the same. For clarity’s sake, think of measurement as a single action that you perform with instrumentation. Collectively, “instrumentation” describes devices (i.e., instruments) that measure, indicate, and sometimes record values.
Today, there are many different types of specialized measuring instruments. Bakers use different measurement tools than electricians, and both use different measuring systems than carpenters. For the purposes of this article, measurement is understood to be used with the design, inspection, and production of manufactured products.
What’s the difference between inspection and measurement?
Inspection is about determining a physical attribute (e.g., size) and comparing it to a reference standard to decide whether the measured object is close enough to the standard to be acceptable. Measurement is about finding or determining this physical attribute, but not necessarily about comparing it to a standard or making a decision about the product’s acceptability.
Here’s another way to understand the difference. When you’re using a ruler to measure an object’s length, you might say that the measurement is either too long or too short. You probably wouldn’t say that based on the value from the ruler, the measurement obtained is either longer or shorter than the desired measurement. The first statement is far simpler, of course, and it’s also generally understood.
What are the two types of measuring systems?
There are two main types of measuring systems: direct and indirect.
Direct measurement systems do not translate what is measured into some other characteristic. Simply put, they directly measure what you want to know. Examples include measuring your height with a measuring tape, determining the temperature of your oven with a thermometer, or measuring the speed of your morning run with a stopwatch.
Indirect measurement translates what is measured into another characteristic. It’s less common in daily life, but important in manufacturing. For example, Accumeasure technology measures capacitance, the ratio of the change in an electric charge to the corresponding change in its electrical potential (i.e., voltage), in order to determine the distance between a probe and target.
MTI’s Capacitance Guide to Industrial Applications provides more information.