Abstract: A pump system for producing high and exactly controllable pressure levels includes a piston pump which has a piston (32) connecting to a spindle shaft (22), a spindle nut (44) on said spindle shaft, a cylinder block (34) having a bore (36) for receiving said piston, a mechanism (14, 16, 26) for imparting relative rotational and axial motions between said piston and said cylinder block including a device for causing relative rotary motion of said spindle and spindle nut. A helical spring (46) or other resilient element is connected between said cylinder block (34) and said spindle nut (44) to compensate the reaction force generated by a pressurized fluid sample in said cylinder bore (36) when put under compresion. A flexible element (30) is connected between the piston (32) and the spindle shaft (22) to compensate for any axial misalignment of the piston and the cylinder bore. Methods for operating such a system under adiabatic, isothermal, isobaric and isochoric conditions are described. (FIG. 3).

Abstract: A cell for measuring acoustical properties for fluid sample includes a stack consisting essentially of a first end piece (20), a first, wafer-shaped electro-acoustical transducer (18), a main body (12), a second electro-acoustical transducer (16) and a second end piece (22). C-shaped clamps (24) or other means are used to apply pressure on the stack. The main body (12) and the end pieces (20, 22) form axially extending, aligned cavities (14, 29, 31). The main body (12) and each end piece (20, 22) has a radial channel (28; 32) which extends from the respective cavity to an opening at a circumferential surface. A thin elastic membrane (50) tightly encloses the stack. An annular member (51) is forced in each channel opening urging a portion of the sleeve (50) into the respective channel to form a pressure resistant seal.

Abstract: A system for measuring fluid parameters of one or more liquids by an ultrasonic method comprises a voltage controlled oscillator; an ultrasonic resonator comprising one or more resonator cells, each of the resonator cells comprising an electro-acoustical transmitting transducer, an electro-acoustical receiving transducer, and a sample cavity between the transducers, wherein the transmitting transducer is connected to the output terminal of the voltage controlled oscillator; and a phase locked loop circuit comprising one of the resonator cells.