Air compressors could hold the key to measuring the density of solid objects without having to make direct contact with them.

There are plenty of reasons why direct contact might not be preferable; such as the desire not to deform the object, or the risk that it might chemically react with the surface that comes into contact with it.

But research published at the International Conference on Mechatronics and Automation 2014 in China last month offers an alternative, using air compressors to determine how dense a non-hollow solid object is.

All that is required is for the object to be placed in a container of fixed size, which is then pressurised using compressed air.

Measuring the change in air pressure with the object inside the container allows for its volume to be calculated, which in turn allows its density to be determined.

It’s a simple and elegant process; and by pressurising the container even further, the accuracy of the measurement can be improved.

Depending on the maximum safe pressure of the container itself, the measurement can get to within a 3% margin for error, according to the researchers.