How do digital calipers work?

The digital calipers was introduced in the late 70s early 80s and has become very popular for a variety of reasons.
Constructed more like the dial than the original vernier, they offer even more functions because of their electronics.
They still perform the outside, inside and depth readings, but have the ability to convert from English to Metric, provide high and low limits alerts (some with colors) and the ability to set your zero position anywhere along the bar. The calipers have the ability to send readings to personal computers or data collectors for unlimited applications.
How do electronic tools work? The calipers employ a capacitance system. To the layman the system is like the electronic ignition in your car, (no actual physical contact). The system consists of a series of rectangular plates etched into a copper or glass strip that stretches the length of the bar, usually concealed by a taped scale or simple cover.
Mounted above this in the movable jaw is a similarly plated slider board. When these rectangular boxes align and misalign, signals are sent to an electronic chip within the calipers case to generate the readings you see on the display.
Since the electronic calipers have no moving parts, foreign matter and other contaminates are less of an issue. However moisture is a problem, if water gets between the stator strip and the slider board the necessary air gap is eliminated and the signal can become garbled or nonexistent. There are some specially designed calipers with protective cases if you are required to work in harsh conditions like these.