As auto technicians, the need for precise dimensional measurements is far less frequent than it used to be. Measuring brake rotors used to be a daily practice; now it’s almost completely forgotten. Occasionally, however, we still find ourselves needing the accuracy. It may be on an engine diagnosis or repair, or maybe it’s an expensive brake rotor that we’re hoping to resurface.You reach into your toolbox to grab your digital caliper or micrometer. Many of us upgraded to digital many years back. After all, it’s a lot quicker, and when you’re getting older and your eyesight isn’t what it used to be, digital is a nice way to go. But if your luck is like mine, the battery is dead.You still have your old ones, but you don’t have time to waste, and you’re thinking, “how do I read this thing again?” Need a refresher? Here’s a crash course.