Two sealed glass cylinders with access valves are mounted on a base board and connected via a tube. One cylinder performs the measuring function and the other is used to pressurise the volume of gas contained above oil in the measuring cylinder. The measuring cylinder is fitted with a compound gauge designed to measure the gas pressure both above and below atmospheric pressure.
The height of oil and hence the volume of gas in the measuring cylinder is measured using a graduated scale. A thermometer in the measuring cylinder allows the temperature of the gas in the measuring cylinder to be determined.
A small *electric compressor provides a means of adjusting the pressure of the test gas above and below atmospheric pressure. The compressor is mounted on the base board and controlled by a panel mounted switch. A pressure switch and relief valves ensure operator safety.
