A fully pneumatic device, the Piab piSAVE optimize vacuum-controlled proportional pressure regulator is engineered for use with air-driven pumps/ejectors. The unit senses the vacuum level in the system; the feed pressure of the compressed air to the vacuum pump/ejector is automatically regulated and controlled to maintain the set vacuum level. The regulator provides maximum feed pressure/vacuum flow to the vacuum pump until the vacuum level starts to build up, and reacts to changes in compressed air pressure or the degree of leakage into the vacuum system to maintain the set vacuum level. 
Piab; www.piab.com