1. As the name says,its a comparator. Basically what it does is,it will compare the size of finished component to the size of a master component.
2. It comes under non-contact type comparator.This means that surface of comparator never actually comes in contact with surface of job or product.
3. The working principal is of back pressure.But,first you need a compressor to create as well as to maintain the pressure.It will be better if this compressor is of positive displacement displacement type,so that you can get a continuous and high pressure.
4. To compare two objects we need to hold them to the end of outlet pipe compressor. You can imagine it like this,if the distance of an object from end of the compressor changes the back pressure created by that object will also change.Now,if the two objects have dimensions overall back pressure created by these objects will the same.
5. The back pressure can be measured by special gauges which are readily available in market.