Test indicator

Before the introduction of modern geared dial mechanism, use of a single lever or lever systems were used in test indicators. The difference lied in the range and precision of these devices which were not as good as the modern ones. The typical range was 10/1000 inch to 30/1000 inch, and precision of 1/1000 inch. At the time, a common single lever test indicator was the Starrett (No 64) and systems of lever were made by Starrett (no 564) [2] and Lufkin (No 199A) [3] and another company called Ideal Tool Co.

Digital indicator

The dial (clock face) such as in the clock has been ousted by the digital display indicators like LCDs and the clockwork has been replaced by linear encoders. Of course digital indicators have its advantages and are hence more prominently used. Recording and transmission of data electronically to a computer through an interface (RS 232 or USB) is an easier work. This enables Statistical Process Control (SPC), where a computer tracks the measurement in a database table or a spreadsheet to interpret the result through statistical analysis

Dial test indicator tips

Dial test indicators have tips that swing in an arc, whereas the previous models had spherical tips that were plunging linearly. As the tips moves through the arc, the point contact is made that gives steady measurements. Consistent offset distance from the ball surface to the center point, in spite of any ball contact angle with the measured surface gives consistent measurement result. The spherical diameters offered are available in the standard size of 1mm, 2mm, and 3mm.