Pneumatic Comparator

A comparator measures the accuracy of a dimension by comparing it against a standard length. A pneumatic comparator uses compressed air, or a pneumatic system, to magnify the dissimilarity when the difference is very small.

A pneumatic comparator, or air plug gage. is connected to a source of compressed air creating a reference pressure. The test part is connected to the same air source and the resulting pressure is measured. The difference between the reference pressure and the test piece pressure is represented by a liquid height, or by a graphical representation. By comparing these values to reference standards or templates measured under the same conditions, the conformity to the dimensional or geometrical specifications can be measured.