having a lumen or piston chamber 44 a hydraulic pressure control rod or piston 46 extends within lumen 44 the proximal end of pressure control rod 46 being operatively connected to a displacement actuator device not shown when pressure control rod 46 is moved in the distal direction as shown by arrow 48 the hydrostatic pressure in chamber 22 increases pressure assembly 42 comprises an end member 52 through which pressure control rod 46 passes o rings 54 in grooves 56 provide sealing another portion of lateral surface 40 of lower chamber 6 comprises a pressure transducer 60 for measurement of the hydrostatic pressure within chamber 22 transducer 60 is operatively e g mechanically or electrically connected to a pressure read out not shown 0057 fig2 represents a schematic of the operation of a chamber of fig1 according to the invention air from air pressure source 70 passes through an air filter 72 into a valve manifold 74 which is operatively connected to a pulse train generator 76 pressurized air from valve manifold 74 is directed to pressure regulation controls 78 80 82 84 in a displacement actuator air piston cylinder 86 connected to actuator rod 32 and a displacement actuator air piston cylinder 88 connected to pressure control rod 46 the latter air piston provides the force necessary to displace the pressure control rod 46 by utilizing the mechanical advantage.