Vac Checker® Digital Absolute Pressure Gauge for Vacuum Resin Infusion Processes The heavy duty design qualifies this gauge particularly for the use in rough workshop environment. If the purpose of the vacuum infusion process is the production of high-quality parts, the use of a precise digital absolute pressure gauge is a must. The Vac Checker® measures the pressure difference relative to the absolute zero of pressure and is unaffected by changing environmental conditions such as weather or altitude. Unlike analog dial gauges, usually mounted on the vacuum pump or resin catch pot, you know exactly what is happening inside the vacuum bag. Vac Checker® Resources:   Vacuum Basic Knowledge | Vac Checker® - Operating Manual