Boyle Law Demonstration PC Technical Description 2 independent transparent cylinders each contain a certain quantity of air. The air is used as the test gas. In the cylinder on the right the air is electrically heated at constant volume and the temperature and pressure changes are measured. The air in the left cylinder is compressed quasi-isothermally using hydraulic oil and a compressor. In this case the pressure and volume changes are measured. All measurements are made electrically and indicated on digital displays. They can be transferred to a PC for further processing.