Ashcroft AVC [AVC-3000] Pressure Volume Controller, Vacuum to 3000 PSI. The Ashcroft AVC pressure volume controllers are piston/cylinder devices that provide fine pressure adjustments in closed pneumatic systems. Mechanical rotation is directly proportional to volume change due to piston travel. The AVC controllers have an integral balance valve that equalizes pressure and acts as a pressure-relief valve. They are constructed with an aluminum body and stainless steel, brass, Teflon, Delrin and Buna-N materials. When used with digital pressure gauges, dial gauges, transducers, pressure switches, air deadweight testers, manometers, and other similar devices they provide a fast and accurate means for setting a precise pressure.