Dial test indicators are precision instruments used to measure linear displacement along the axis of a spindle. The spindle moves in and out and the dial shows the measurement. They are mainly used for checking height, depth, thickness, and runout in various mechanical and technical applications.

Centering dial indicators are similar but designed to measure angular displacement, usually with an arm instead of a spindle. They are more sensitive and mainly used for inspecting surface flatness, alignment, and small differences, especially in tight spots or for centering tasks.