Dial indicator
A dial gauge is a mechanical measuring device for measuring lengths or differences in length. It is used, for example, for comparison, flatness, position or concentricity measurements. Dial indicators have existed since the end of the 19th century and are now manufactured with either an analogue or a digital display. The function and structure of dial gauges are standardized by DIN regulation 878 .
Layout and function
In gauges with round scale and analogue display , the longitudinal movement of the probe by means of rack and pinion on the pointer transmitted. This allows the pointer of the dial indicator to turn in a circle several times. The number of revolutions is indicated by another hand, similar to the hour hand of a clock, which shows the number of revolutions of the minute hand.
The rack ratio has the advantage that the dial indicator has a relatively large measuring range. However, it also has disadvantages: If the measurement to be determined on the measuring object exceeds the travel range of the rack considerably, the gearbox or rack can be damaged if the dial indicator is rigidly locked. Repeatedly exceeding the measuring path of the rack can lead to inaccuracies. A so-called “drag pointer” is also possible, which manifests itself in an extremely delayed pointer return. This means that measurements can no longer be carried out that rely on value differences , i.e. concentricity and flatness measurements .
Furthermore, a dial gauge is characterized by the fact that it can be used in both push and pull operation and the measuring rod is returned via a spring. Thus the applied measuring force is almost constant.
Dial indicators usually achieve an accuracy of approx. 1/100 mm (10 µm ) with a typical measuring range of 5 to 60 mm. Dial gauges with an accuracy of 1/1000 mm (1 µm ) are rarer .
A similar measuring device is the dial indicator , which, however, has a different structure and a smaller measuring range.
Dial gauges, like micrometers and measuring probes, have hardened surfaces or balls with which they touch the object to be measured. Some dial gauges also have shock protection, which protects the measuring mechanism from damage caused by vibrations. Bow dial gauges allow easy measurement of the thickness of flat objects. To do this, the two measuring surfaces are pulled apart and the object to be measured is held between them. After letting go, both surfaces rest on the object again and the pointer shows the thickness of the material.
Presetting measuring device
The presetting measuring device used in wood processing is a special type of dial gauge . The feeler pin is located in the middle between two arched connection and contact feet. If the device is placed on a machine table over a tool, for example a milling cutter in a table milling machine or a saw blade in a circular saw, the cutting edge protrusion and thus the milling or cutting depth can be measured and set. Due to the flat shape of the housing, it is also possible to use the device lying down to determine the tool protrusion at the stops.
See also
Web links
Individual evidence
- ↑ Martin Naumann: Measurement and testing technology. Vieweg + Teubner Verlag, Wiesbaden 1974, ISBN 3-528-04027-0 , p. 22.
- ↑ "Geometrical Product Specifications (GPS) - Mechanical Dial Gauges - Limit Values for Metrological Features". DIN edition 2006-06
- ↑ History, construction methods and use
- ↑ Wolfgang Nutsch and others: expertise for carpenters. 12th edition. Verlag Europa-Lehrmittel, Wuppertal 1980, ISBN 3-8085-4011-7 , p. 231.