Air Gages Information

Air Gauges Information

Air gauges use pneumatic pressure and flow to measure and sort dimensional attributes. They provide a high degree of speed and accuracy in high-volume production environments. Air metrology instruments can provide comparative or quantitative measurements such as thickness, depth, internal diameter (ID), outer diameter (OD), bore, taper and roundness. Air gauges and gaging systems may also use an indicator or amplifiers such as air columns combined with air probes or gauges.

Types of Air Gauges

There are several types of air gauges. Air plugs are production-quality, functional gauges for evaluating hole and slot dimensions or locations against specified tolerances. Air rings are also production-quality, functional gauges, but are used for evaluating specified tolerances of the dimensions or attributes of pins, shafts, or threaded studs. Air gaging systems or stations are large, complex units available in bench-top or floor-mounted configurations. These systems often include several custom gauges for OEM applications, as well as fixtures or other components for holding or manipulating parts during inspection. Air probes, or gauge heads, are also used in conjunction with other gauges, and connect to remote displays, readouts, or analog amplifiers. 


Test indicators and comparators are instruments for comparative measurements where the linear movement of a precision spindle is amplified and displayed on a dial or digital display. Dial displays use a pointer or needle mounted in a graduated disc dial with a reference point of zero. Digital displays present metrology data numerically or alphanumerically, and are often used with air gauges that have data output capabilities. Remote gauges are used on electronic or optical gauges, probes, or gauge heads that lack an integral gauge. Air gauges can use the English measurement system (e.g., inches) or the metric system (e.g., centimeters). 


Air gauges use changes in pressure or flow rates to measure dimensions and determine attributes. Back pressure systems use master restrictor jets, as well as additional adjustable bleeds or restrictions, to measure pressure changes and adjust for changes in air tooling. Flow systems use tubes or meters to measure flow rates through air jets, orifices, or nozzles. Back pressure systems have high sensitivity and versatility, but a lower range than flow systems. Flow system gauges require larger volumes of air and nozzles, and are useful where larger measurement ranges are required. Differential, balanced air, single master, or zero setting air gauge systems are back pressure systems with a third zero-setting restrictor.


Some air gauges are handheld and portable. Others are designed for use on a benchtop or table, or mount on floors or machines. Operators who use benchtop, table-based, and floor-mounted air gauges load parts and measure dimensions manually. Automatic gauges, such as the inline gauges on production lines, perform both functions automatically. In semi-automatic systems, operators load parts manually and gauges measure automatically. Typically, machine-mounted gauges include test indicators, dial indicator, and or micrometer heads.