The working principle of a large air compressor pressure gauge, with a range of 0-240 PSI or 0-16 Bar, is similar to other pressure gauges. It utilizes a diaphragm or a Bourdon tube mechanism to measure and display the pressure. As the air pressure increases, the diaphragm or Bourdon tube experiences mechanical deformation, causing it to move or flex. This movement is transferred to a mechanical linkage connected to a pointer on the gauge dial. The pointer then moves along the calibrated scale, indicating the corresponding pressure reading. The diaphragm or Bourdon tube is carefully calibrated to ensure accurate pressure measurements within the specified range, allowing for precise monitoring and control of the air compressor's output pressure.