公开(公告)号：US6085577A

公开(公告)日：2000-07-11

申请号：US43952

申请日：1998-07-16

申请人： Tanya C. Christensen ,  Alexander F. Teichmann ,  Victor P. Janule

发明人： Tanya C. Christensen ,  Alexander F. Teichmann ,  Victor P. Janule

IPC分类号： G01N13/02 ,  G01N13/00

CPC分类号： G01N13/02 ,  G01N2013/0266

摘要： Method and apparatus for measuring the surface tension of a liquid inside a vessel (2), reactor, or inside a section of flow-through process pipe that is pressurized above normal ambient pressure, up to but not limited, to 100 psig (7000 kPa), includes a pair of tubes (2,3) having a small and large orifice in a modular probe assembly that allows the probes to be positioned at selected and variable distances below the surface of the liquid. A high pressure source (4) provides an inert nitrogen or process gas through a pressure regulator (5) to the input of two or three mechanical or electronic mass flow controllers (6,7,8), powered by an external power supply (9), which control the bubble rate at each orifice through manual adjustments, or electronic set points determined by a computer software program, independent of the pressure in the vessel, reactor, or flow-through process pipe. One or more differential pressure transducers (10,11) measure the pressure of bubbles being formed and released from the two orifices. A transducer demodulator circuit (12) converts the resulting fluctuating pressure signal directly to an equivalent fluctuating electrical DC voltage signal. This signal is input to a (13) computer using one or more plug-in analog input/output computer interface circuit boards (14). A software program tracks the differential waveform and captures the maximum differential bubble pressure which is directly proportional to fluid surface tension. A temperature probe (15) and/or other commercially available probe (such as conductivity, viscosity, or density) is immersed at the same level as the orifices to measure liquid temperature, and/or other process parameters. A pneumatic damper (16) smoothes the large orifice signal in the single transducer apparatus (FIG. 1), whereas in a two transdcuer apparatus the average maximum values of the two individual, undampened, pressure signals are electronically substracted to provide the maximum differential bubble pressure which is directly proportional to fluid surface tension.