A dial indicator is a small tool that measures very small distances or changes in position. It has a needle that moves along a dial or scale, showing you the exact measurement. Full definition
Quality inspection of steel coils, check for defects coming out mill from hot end using 1 - 2 «calipers 1 - 2 «micrometers, height gauges, and dial indicator Tested steel hardness with birnell machine. (livecareer.com)
I've used many different types (dial indicator, electronic) and broken each and every one of them. (mechanics.stackexchange.com)
You can check them for true with a dial indicator when you have the car on jack - stands. (mechanics.stackexchange.com)