Different inspection tools exist for different purposes, but all tools require proper set-up in order to be used accurately. Users lift the plunger of a dial indicator from one surface to another to measure the distance between the two planes, or slide the tool across a flat object to measure any small variances in surface flatness. The key to using a dial indicator correctly is to zero in the tool to the reference plane before taking any readings.
Position the dial indicator over the object being measured, perpendicular to the reference plane. Lock the dial indicator in place.
Lower the dial indicator's plunger until it rests on the top of the reference plane.
Loosen the bezel's locking knob if your indicator is a traditional model with a rotating face. Rotate the face of the indicator until the "0" marking aligns with the dial. Tighten the knob afterward to lock the face in position.
Twist the zero adjustment knob if your dial indicator does not feature a rotating face. Continue twisting the knob until the dial aligns with the "0" marking.