Pneumatic Comparator

Pneumatic Comparator

The comparator in Metrology is a precision instrument, used for measuring the accuracy of a given component by comparing the given component dimension with the actual working standard. It is an indirect type of accuracy measurement because it will not measure the dimension, but it will specify the dissimilarity within measurement between the specified component & working standard. Generally, comparators are available in different types which are used based on the requirement in different fields like electrical & electronics, optical, electromechanical, mechanical-optical, pneumatic, multi-check, fluid displacement, projection, automatic gauging  & mechanical comparator. So this article discusses one of the types of comparator namely – pneumatic comparator, working, types & its applications.

What is a Pneumatic Comparator?

A comparator that uses compressed air (or) pneumatic system as a means of magnification is known as a pneumatic comparator. The term ‘Pneumatic’ in pneumatic comparator means ‘air’. The main function of this comparator is to analyze the dimensional variation between the standard workpiece & workpiece to be measured. So these comparators are extremely preferred in most cases over other types of comparators due to many benefits.

Working Principle

The working principle of the Pneumatic comparator is the variation of pressure generated within the airflow. When the air escapes under stable pressure by flowing through the two orifices then the pressure of air among them mainly depends on the cross-sectional regions of the two orifices. So the dimension of one is kept consistent, and the pressure of the remaining one changes based on its dimension.

Pneumatic Comparator Design

The pneumatic comparator is designed with some important parts like a compressor, water tank, air filter, pressure regulator, dip tube, manometer tube, control orifice, flexible tube, gauging head, and scale which are explained below.

Pneumatic Comparator Working

The pneumatic comparator working is; it includes a water tank where the water is filled up to a particular level. After that, a calibrated manometer is connected to the tank vertically. In the water tank, the water level, as well as the manometer, must be similar & it is adjusted with a workpiece. A compressor is used at maximum pressure to compress the air. So, the air is filtered as well as regulated with pressure with the help of a pressure regulator & air filter.

The air which is filtered will be supplied through a dip tube where this tube is submerged within a tank. At the same time, the compressed air by the equivalent pressure flows throughout the opening of the control orifice. Once air flows throughout the CO or control orifice, then velocity will be increased & at the same time, pressure will become stable. The air including vast velocity supplied through the pneumatic hose or flexible tube and lastly it arrives at the measuring head.

The head of water is maintained stably in the dip tube because of the expansion of air within. The surplus air will run away within the tank like bubbles of air. At stable pressure, the air runs away using a measuring jet in the measuring head.

When the workpiece is standard then the air escapes continuously through the measuring jet. At the same time, the water level within the tank & manometer tube will be matched. If there is any irregularity within the workpiece, especially for actual flow within the measuring jet, then a certain back force will be formed.

In the manometer, the water level will be dropped because of the induced back pressure through the limits within the workpiece. So, the level of water change can be signified as the dimensional variation or any abnormalities within the workpiece as compared to the normal workpiece.