The most accurate mechanical length measurement devices are finger indicators.
They usually have a scale interval of 1 µm.
A lever system transmits the movement of the measuring pin to the pointer via gears and pinions.
This results in no full pointer rotation.
Due to the small measuring range of approx. 50 – 100 µm, the finger indicator is mainly used for differential measurement.
Adjustable auxiliary pointers are often included, which allow the marking of the tolerance range.
So it is possible to see at a glance whether the tested part is within this tolerance.
In contrast to dial gauges, a higher resolution and a lower reversal span of 0.5 µm is possible.