Indicator Gaging Tips
In many applications digital indicators are becoming so powerful that they are taking on the performance and features of bench amplifiers.
Dial indicators—also known as dial gages, clocks, comparators, or just indicators—are widely used as basic gages for measuring linear dimensions.
When digital electronic indicators were first introduced in the early 1980s, observers expected them to blow mechanical dial indicators out of the water. But despite the clear superiority of electronic indicators in terms of higher resolutions, better accuracy, and usefulness in statistical process control and data collection systems, mechanical indicators retained other advantages and continued to be specified by many users.
When most of us think about measurement environments, what generally comes to mind are pleasant laboratories with temperatures controlled to 68°F/20°C -- plus or minus a degree or two.
Dial indicators have been around since the early 1900s. To maintain high levels of quality and precision, take heed of the following tips.
Most dial indicators have a total measurement range of 2.5 revolutions of the needle, as per AGD (American Gage Design) specifications. Indicators that allow the needle to go around only once are comparatively rare but offer a distinct advantage for shop-floor inspection applications.
Most engineers are afflicted with insatiable curiosity and can't help but take things apart. However, as dial indicators are highly sensitive instruments, we'd like to help them resist this urge with the following anatomical description.
The golden rule is that a clockwise dial indicator should be used when the indicator and/or the sensitive contact is on the opposite side of the part from the reference point, while the counterclockwise indicator is used when the indicator and the sensitive contact are on the same side as the reference point.
Test indicators are distinct from dial indicators in that they excel at "consistency" in making comparative measurements. They are used most often to explore relatively broad part surfaces in either one or two dimensions:
Test indicators are pretty distinct from dial indicators. The immediately obvious difference is that test indicators have lever-type contacts, while dial indicators have plunger-type contacts.
There are few worse feelings for a manufacturer than having a product returned because the customer determines it is defective. Not to say that things are always perfect, but the vast majority of products manufactured do meet their design requirements.
When we think about comparative indicators, we usually are referring to dial indicators. However, test indicators also provide comparative measurements.