What is true value? It is defined as the actual physical weight/length/width or other measurable parameter of a specific object – for example, the length of a piece of string or the weight of a rock[1]. All objects have a true value because all have exact properties that can (in theory) be measured.
Thus, when we measure, we seek to identify the true value. However, no measurement system can do this with complete accuracy because measurement systems are subject to error. The goal or measurement therefore is to get as close as possible to determining the true value by taking all available precautions when measuring the object in question.
Why do I say, “as close as possible”? Because, as noted, we know that in any system of measurement, there will always be some deviation (or “measurement error”). Sometimes such errors are acceptable, but sometimes (particularly in industrial settings) they are not. In the everyday world when, for example, you’re cooking or making clothes, then measuring with kitchen scales or a tailor’s tape measure is, generally speaking, sufficient – because we don’t need the highest degrees of accuracy.
On the other hand, if you are building a bridge for example, then you need accuracy to another level altogether. So, in such cases, we have to be confident that we are getting as close to true value as possible. To do this, we need to know that we have the right tools to take measurements to the required degree of accuracy, for the specific measuring tasks in hand.
If all this sounds somewhat complicated, an example might help to make things clearer.
Measured value and true value
A measured value is expressed as the product of an object stated in terms of a numerical value and is presented in the form of appropriate units (inches, kilos, etc.), sometimes as a percentage and sometimes in a standardized form. The result needs to be as accurate as the context demands – which can require highly specialized measuring systems and tools, so we can get as close to true value as we possibly can.
Generally, in everyday life we don’t do this because it’s not necessary when baking a cake. We know that when taking measurements, the results will deviate from the true value – though even in in domestic settings we will try to minimize these errors (for instance, by re-balancing our scales before use) while accepting that they are, sadly, unavoidable.
Where do these errors arise? They derive from the system used to take the measurement and we always want to minimize these errors. Doing so is particularly essential when we are manufacturing complex industrial machinery or precision medical equipment. In commercial situations, getting as close as possible to the true value really matters.
Understanding and using the correct terms is always important if you need to measure very small tools and parts – or wires and cables – with high accuracy and repeatability. It’s also why true value must be kept front of mind. When you measure any object – for instance a wire – you need to maximize the accuracy of the measurements you capture, to suit the purposes for which the objects are intended.
About Conoptica
A leading source of high accuracy measurement systems for drawing dies is Conoptica. We provide a variety of measurement systems suitable for dies of different sizes. They enable high accuracy measurement of dies, so that you can track consistency and take appropriate actions – avoiding excessive quality deterioration, better management of your die stocks – and to maintain production output.
Our measurement systems will give an average measurement expected to be within ±0.4 µm (for the 20X objective) from the true value (to put that in context, an average human hair is 16 – 50 µm). That expectation is based on reference to measurements from the PTB [2]measurements, which have much higher accuracy, though even those will have an error compared to the true value.
Conoptica is the market leader for measurement equipment in the wire & cable industry and has been providing high tech camera-based measurement solutions since 1993. We make sure that the metal working industry has access to key quantitative data about their products and tools.
[1] https://www.bipm.org/documents/20126/2071204/JCGM_200_2012.pdf/f0e1ad45-d337-bbeb-53a6-15fe649d0ff1