Tutor4u shows how to get accurate reference using a digital caliper for making 3D models with Blender.
As an artist, you should always use excellent references. When modeling in 3D, there are several ways that you can use a reference to help you model real-world and other objects too. One way is to bring in a drawing as an image plane or a template from which you can build your work. Another way, and likely uncommon but more accurate is to use digital calipers to take measurements off a real-world object. Check out this tutorial from Tutor4u who shows how you can use digital calipers to help along with the modeling process.
The tutorial shows how to make a 3D model of a stereo plug adapter, using a real one as a reference, and building the 3D version inside of Blender. Yes, not everyone has calipers, but it is a new method for getting accurate measurements from an object that you want to build in 3D.