Abstract:
A Coriolis flowmeter for the measurement of a process material requiring an ultra high level of purity. This is achieved by forming the entire Coriolis flowmeter of a PFA plastic material that does not transfer ions from the Coriolis flowmeter to the process material flowing through the flowmeter.

Description:
RELATED APPLICATIONS  
       [0001]     This patent application is a continuation of pending application Ser. No. 09/994,251, filed Nov. 26, 2001, and entitled Flowmeter for the Precision Measurement of an Ultra-Pure Material Flow, and is hereby incorporated by reference into this application to the extent as fully set forth herein. This application is further related to the following concurrently filed patent applications assigned to the same assignee: 
        1. U.S. application Ser. No. 09/994,257, filed Nov. 26, 2001, titled METHOD OF MANUFACTURING A FLOWMETER FOR THE PRECISION MEASUREMENT OF AN ULTRA-PURE MATERIAL FLOW;     2. U.S. application Ser. No. 09/994,264, filed Nov. 26, 2001, titled MANUFACTURING FLOW METERS HAVING A FLOW TUBE MADE OF A FLUOROPOLYMER SUBSTANCE; and     3. U.S. application Ser. No. 09/995,174, filed Nov. 26, 2001, titled HIGH PURITY CORIOLIS MASS FLOW CONTROLLER, now Patent No. 6,606,917.       
 
     
    
     FIELD OF THE INVENTION  
       [0005]     This invention relates to a Coriolis flowmeter that measures a flow of process material having an ultra high level of purity.  
       Problem  
       [0006]     It is known to use Coriolis effect mass flowmeters to measure mass flow and other information pertaining to materials flowing through a pipeline as disclosed in U.S. Pat. No. 4,491,025 issued to J. E. Smith, et al. of Jan. 1, 1985 and Re. 31,450 to J. E. Smith of Feb. 11, 1982. Flowmeters have one or more flow tubes of a straight, curved or irregular configuration. Each flow tube has a set of natural vibration modes which may be of a simple bending, torsional, or twisting type. Each material filled flow tube is driven to oscillate at resonance in one of these natural modes. The natural vibration modes are defined in part by the combined mass of the flow tubes and the material within the flow tubes. If desired, a flowmeter need not be driven at a natural mode.  
         [0007]     Material flows into the flowmeter from a connected material source on the inlet side. The material passes through the flow tube or flow tubes and exits the outlet side of the flowmeter.  
         [0008]     A driver applies force to oscillate the flow tube. When there is no material flow, all points along a flow tube oscillate with an identical phase in the first bending mode of the flow tube. Coriolis accelerations cause each point on the flow tube to have a different phase with respect to other points on the flow tube. The phase on the inlet side of the flow tube lags the driver; the phase on the outlet side leads the driver. Pickoffs are placed on the flow tube to produce sinusoidal signals representative of the motion of the flow-tube. The phase difference between two sensor signals is divided by the frequency of oscillation to obtain a delay which is o proportional to the mass flow rate of the material flow.  
         [0009]     It is known to use flowmeters having different flow tube configurations. Among these configurations are single tube, dual tube, straight tube, curved tube, and flow tubes of irregular configuration. Most of the flowmeters are made of metal such as aluminum, steel, stainless steel and titanium. Glass flow tubes are also known.  
         [0010]     The positive attributes of titanium in flowmeters are its high strength and low coefficient of thermal expansion (CTE). The negative attributes of titanium are its metallic properties and cost of manufacturing. In semiconductor wafer processing, metal ions are a contaminant. Metal ions in contact with the wafer areas of an integrated circuit can cause a short circuit and ruin the device. Also, a Titanium flowmeter is difficult and expensive to produce.  
         [0011]     The prior art also suggests plastic flow tubes and plastic flowmeters. This includes prior art in which the entirety of the flowmeter is plastic as well as that in which only the flow tube is formed of plastic. Much of this prior art merely contains an assertion that a flowmeter may be made of various materials such as steel, stainless steel, titanium or plastic. This prior art is not instructive in so far as concerns the disclosure of a plastic Coriolis flowmeter that can accurately output information over a range in operating conditions including temperature.  
         [0012]     The mere substitution of a plastic flow tube for a metal flow tube will produce a structure that looks like a flowmeter. However, the structure will not function as a flowmeter to generate accurate output information over a useful range of operating conditions. The mere assertion that a flowmeter could be made out of plastic is nothing more than the abstraction that plastic can be substituted for metal. It does not teach how a plastic flowmeter can be manufactured to generate accurate information over a useful range of operating conditions.  
         [0013]     It is a problem in some applications that the typical Coriolis flowmeter may contaminate the process material. This is undesirable for systems in which material of an ultra high level of purity must be delivered by the flowmeter to a user application. This is the case in the fabrication of semi-conductor wafers which requires the use of a process material that is free of contaminants including ions migrating from the tubes of the process material flow path. In such applications, the flow tube can be a source of contaminants. The metal walls of a flow tube can release ions into the process material flow. The released ions can cause the chips on a semi-conductor wafer to be defective. The same is true for a glass flow tube which can release the lead ions from the glass into the process material flow. The same is also true for the flow tubes formed of conventional plastics.  
         [0014]     A plastic termed PFA is free from this objection since the material of which it is composed does not release deleterious ions into the material flow. The use of PFA for a flow tube is suggested in U.S. Pat. No. 5,918,285 to Vanderpol. This suggestion is incidental to the Vanderpol disclosure since the patent discloses no information regarding how a flowmeter having a PFA flow tube could be manufactured to generate accurate flow information.  
         [0015]     Flow tubes lined with PFA, as disclosed in U.S. Pat. No. 5,403,533 to Dieter Meier, attempted to combine the positive attributes of both metal and plastic technologies but encountered new challenges that could not be solved until the present invention. Metal flow tubes lined with PFA allow metal ions to migrate through the thin PFA coating layer and into the flow stream to cause contamination. Also, the metal flow tube material and the PFA liner have different thermal properties. This caused the PFA liner to disengage from the flow tube to create leaks and performance problems. The manufacturing process for lining the metal flow tubes with PFA is also extremely costly.  
       Solution  
       [0016]     The above and other problems are solved and an advance of the art is achieved by the present invention which discloses a Coriolis flowmeter having at least one flow tube formed of perfluoroalkoxy copolymer (PFA) plastic. The flow tube is coupled to a driver and to at least one pickoff sensor to enable the PFA flow tube to function as part of Coriolis flowmeter that can provide accurate output information over range of operating conditions for a process material flow of ultra high purity suitable for use in applications such as semi-conductor fabrication and the like which require the material flow to be free of contaminants down to the ionic level.  
         [0017]     A flow path constructed entirely of PFA has many of the benefits of Titanium and PFA lined flow tubes without the drawbacks. PFA is a fluoropolymer with superior chemical resistance, little metal ion release, low particle generation, and is manufacturable without expending large amounts of capital. PFA material is strong and can be extruded into high quality thin wall tubing. Thin-walled PFA tubing has low flexural stiffness enabling a higher sensitivity to mass flow rate and improved immunity to elastic dynamic interaction between the flow tube and the process pipeline. The material and physical properties of PFA allow larger tube vibration amplitudes at lower stress levels and result in near infinite fatigue life span. Also, the higher vibration amplitude allows the use of small low-mass transducers, which in turn improves density sensitivity and immunity to mount variation.  
         [0018]     A first preferred exemplary embodiment of the invention comprises a flowmeter having a single PFA plastic flow tube coupled to a massive metal base which balances the end node vibration of the flow tube. The base is U-shaped and the plastic flow tube extends through coaxial holes in the two legs of the U. The plastic flow tube is affixed to the holes in the base by means of an appropriate adhesive such as cyanoacrylate also termed Loctite  420 . The longitudinal center of the flow tube is affixed to an electromagnetic driver which receives a drive signal from a meter electronics to vibrate the flow tube transversely to the longitudinal axis of the flow tube. This vibration may be at the first bending resonant frequency of the flow tube. The flow tube is coupled to pickoffs which detect the Coriolis response of the vibrating flow tube with material flow. In the first embodiment, the pickoffs may be a conventional electromagnet combination with magnets affixed to the flow tube and a coil affixed to the base. In an alternative embodiment, the pickoffs are optical devices which generate a light beam and that is modulated by the vibrations of the flow tube. The optical sensing embodiment offers the advantage that the weight of the pickoff magnets is removed from the vibrating flow tube. This increases density sensitivity. The driver is a source of heat that can raise the temperature of the plastic; thermally expand the plastic and degrade the accuracy of the generated output information. In this embodiment, the driver is advantageously affixed on top of the flow tube when in use. This mounting arrangement has the advantage that the heat generated by the driver radiates upwardly away from the flow tube.  
         [0019]     In accordance with another embodiment, the magnets associated with the driver and sensor pickoffs have low mass since they are small and do not have keepers or pole pieces. The magnets and coils have been optimized to make the magnets as small (low mass) as possible. The magnet material has been chosen to have the most magnetic field per unit mass as possible. The tube geometry has been designed to achieve the desired motion with as little drive force as possible. PFA has naturally low damping, so drive force is inherently low due to selecting this material for the flow tube. All of these factors contribute to achieving low mass transducer parts on the flow tube. This is advantageous since it reduces the physical loading of the flow tube and enhances the output accuracy of the flowmeter.  
         [0020]     The single flow tube comprises an unbalanced structure whose vibration is minimized by the massive base. The ratio of the mass of the base to mass of the single plastic flow tube together with its magnetic material mass is in the order of 3,000 to 1. This results in a heavy base structure having a weight of approximately 13 pounds for a flow tube, plus magnets and material mass having a total weight of about 2 grams. Although the 13 pound weight minimizes the vibrations at the nodes of the flow tube, it has a disadvantage of increasing the weight of the equipment of which the flowmeter is a part. These vibrations may be minimized by the use of a dynamic balancer or a active dynamic balancer. The active dynamic balancer transmits signals to the meter electronics which analyzes the signals and returns a control signal to the active dynamic balancer to reduce the undesired vibrations. This has the advantage that the overall weight of the base structure may be reduced from 13 pounds down to about 2 pounds.  
         [0021]     As mentioned, the first preferred embodiment comprises a Coriolis flowmeter having a single straight tube operating in an unbalanced mode in cooperation with a massive base. Other flow tube configurations are provided by other embodiments of the invention. The invention may be practiced with the use of dual flow tubes vibrating in phase opposition. These dual tubes may either be straight, they may be unshaped, or they may be of a irregular configuration. The use of dual flow tubes is advantageous in that it provides a dynamically balanced structure that reduces the mass of the base required to mount the flow tubes.  
         [0022]     An additional embodiment that can be associated with any tube configuration is the provision of a temperature measurement device. A preferred embodiment is the use of a Resistive Temperature Device (RTD) attached to a flow tube. If desired, the temperature can be measured using an infrared temperature measurement device. The benefits to this device is that it is non-contact and can be located off the tube, thereby reducing mass on the tube. Also, the RTD can be mounted to another flow carrying tube in the sensor which is not the vibrating flow tube.  
         [0023]     Another embodiment comprises a massive base having upwardly extending sidewalls and a single flow tube extending through coaxial holes in the sidewalls. The base has an inner and an outer pair of upwardly extending walls. The inner walls contain the stationary vibrational nodes of the active portion of the flow tube; the outer walls mount connectors to which an inlet of the flow tube is connected at one end and an outlet of the flow tube is connected at the other end. This arrangement provides a dynamically unbalanced structure comprising a single flow tube with any vibrations at the nodes of the active portion of the flow tube being suppressed by the inner pair of upwardly extending walls.  
         [0024]     Still another embodiment of the invention comprises a massive base having upwardly extending side walls and a pair of flow tubes extending through holes in the side walls. The two flow tubes are connected in series in so far as concerns the process material flow. This connection is accomplished by means of short u-shaped length of PFA tubing at one end of the base. This short unshaped length of tubing connects an outlet end of the first flow tube to an inlet end of the second flow tube which is positioned in the base parallel to the first flow tube. With this arrangement, an inlet end of the first flow tube and an outlet end of the second flow tube are positioned in the same upwardly extending wall of the massive base. The two flow tubes are vibrated by separate drivers in phase opposition. Each flow tube also has its pair of pickoffs for detecting the Coriolis response of its flow tube with material flow.  
         [0025]     In summary, the Coriolis flowmeter embodying the present invention is advantageous in that it provides for the measurement and delivery of a process material having an ultra high level of purity. This level of purity is provided by the use of a PFA plastic flow tube which is superior to metals, glass and ordinary plastics all of which permit ion transfer from the flow tube material to the processed material. The processed material may typically comprise a slurry which is an organic compound used as a polishing agent in the fabrication of wafers in the semi-conductor industry. This polishing operation provides a flat surface for the wafers. The polishing operation can take about an hour during which time the slurry must be free from any contaminants. The deposit of a single undesired ion onto a semi-conductor wafer can short circuit all or a portion of the wafer and render it useless.  
         [0026]     An aspect of the invention is a Coriolis flowmeter for measuring a process material flow having an ultra high level of purity, said Coriolis flowmeter comprising: 
        a base;     flow tube apparatus adapted to receive said process material flow, said flow tube apparatus is formed of a material that does not transfer ions from said flow tube apparatus to said process material;     end portions of said flow tube apparatus are coupled to said base to create substantially stationary nodes at said end portions;     said flow tube apparatus has high flexibility and also has a stiffness substantially lower than flow tube apparatus formed of metal or glass;     a driver coupled to said flow tube apparatus for vibrating said flow tube apparatus containing said process material flow;     pickoff means coupled signalwise to said flow tube apparatus for generating signals representing induced Coriolis deflections of said vibrating process material filled flow tube apparatus; and     meter electronics that receives said signals from said pickoff means and generates output information pertaining to said process material flow.        
 
         [0034]     Preferably said flow tube apparatus defines a substantially straight single flow tube.  
         [0035]     Preferably the entirety of the wetted flow path of said Coriolis flowmeter comprises a PFA substance.  
         [0036]     Preferably said flow tube apparatus defines more than one flow tube.  
         [0037]     Preferably said pickoff means is an electro-magnetic device having a magnet connected to said flow tube apparatus and further having a coil.  
         [0038]     Preferably said pickoff means comprises a light source and an optical detector; 
        said vibrating flow tube apparatus is positioned between said light source and said optical detector to alter the characteristics of the light received by said optical detector from said light source;     said optical detector is responsive to said alteration to generate said signals representing said Coriolis deflections.        
 
         [0041]     Preferably said base has a lower surface and an inner pair of upwardly extending side walls as well as an outer pair of upwardly ending walls; 
        openings in each of said upwardly extending walls are coaxially aligned to receive said flow tube apparatus.        
 
         [0043]     Preferably said base is substantially u-shaped and has a lower surface and a pair of upwardly extending walls proximate sides of said base; openings in each of said upwardly extending walls are coaxially aligned to receive said flow tube apparatus.  
         [0044]     Preferably ends of said flow tube apparatus extend beyond said walls.  
         [0045]     Preferably said base is a solid rectangular element defining a parallelepiped; 
        said flow tube apparatus is connected to posts affixed between said walls to a top surface of said base.        
 
         [0047]     Preferably an inlet of said flow tube apparatus receives said process material flow from a supply tube; 
        an outlet of said flow tube apparatus is coupled to an inlet of a return tube;     said return tube is coupled to said base and is positioned parallel to said flow tube apparatus and extends through walls of said base, and     said return tube is adapted to be connected to an exit tube to extend said process material flow towards a user application.        
 
         [0051]     Preferably said flow tube apparatus comprises a single flow tube and that said base has a mass substantially greater than the mass of said flow tube with process material.  
         [0052]     Preferably the mass of said base is at least 1000 times the mass of said single flow tube with process material.  
         [0053]     Preferably the mass of said base is at least 100 times the mass of said single flow tube with process material.  
         [0054]     Preferably said driver is affixed to the top of said single flow tube when in use.  
         [0055]     Preferably a dynamic balancer means coupled to said base proximate said nodes to maintain said nodes at a reduced level of vibration.  
         [0056]     Preferably said dynamic balancer means is an active dynamic balancer controlled by the exchange of signals with said meter electronics.  
         [0057]     Preferably said base is substantially unshaped and has a lower surface and a pair of upwardly extending side walls containing coaxially aligned openings for receiving said single flow tube.  
         [0058]     Preferably said single flow tube extends through coaxial openings in said walls.  
         [0059]     Preferably said flow tube apparatus comprises a first and a second flow tube coupled to said base and positioned parallel to each other, said first and second flow tubes are adapted to be vibrated in phase opposition by said driver.  
         [0060]     Preferably said driver is affixed to both said first flow tube and said second flow tube and is adapted to vibrate said first and second flow tubes in phase opposition; 
        said pickoffs being affixed to both said first and second flow tubes to detect the Coriolis deflections of said first and second flow tubes.        
 
         [0062]     Preferably said first and second flow tubes are connected in series with respect to said material flow.  
         [0063]     Preferably said first and second flow tubes are connected in parallel with respect to said material flow.  
         [0064]     Preferably a return tube coupled to said base and oriented parallel to said first and second flow tubes; 
        said return tube receives said process material flow from said first and second flow tubes and extends said material flow towards a user application.        
 
         [0066]     Preferably said base is unshaped and has upwardly extending walls; 
        said first and second flow tubes extend through said walls of said base and have inlet and outlet ends projecting beyond the outer surfaces of said walls.        
 
         [0068]     Another aspect comprises a Coriolis flowmeter for measuring a flow of process material having an ultra high level of purity; 
        said Coriolis flowmeter comprising:     a single flow tube formed of a material, such as PFA, that does not transfer ions from said single flow tube to said process material;     said single flow tube has high flexibility and further has a stiffness substantially lower than a metal or glass flow tube;     the entirety of the wetted path of said Coriolis flowmeter comprises said PFA material;     a driver affixed to said single flow tube for vibrating said single flow tube containing said process material flow;     a massive base affixed to ends of said single flow tube to absorb undesired vibratory forces generated by said vibrating flow tube;     said base defines stationary nodes at ends of said flow tube;     an inlet connector connected to said massive base and adapted to receive a flow of said process material from a supply tube;     an inlet end of said single flow tube is affixed to said inlet connector;     said input connector sealably connects said inlet end of said single flow tube to an outlet end of said supply tube to effect the extension of said process material flow in said supply tube to said single flow tube;     said inlet connector maintains said inlet end of said flow tube fixed with respect to said massive base;     an outlet end of said single flow tube affixed to a second connector for extending said process material flow via an exit tube towards a user destination;     a pair of pickoffs coupled to said single flow tube on opposite sides of said driver for generating signals representing Coriolis induced deflections of said vibrating material filled single flow tube;     meter electronics; and     conductors extending signals from said pickoffs to said meter electronics;     said meter electronics receives said pickoff output signals and generates output information pertaining to said process material flow.        
 
         [0085]     Preferably a return tube connected to said massive base parallel to said single flow tube; 
        end portions of said single flow tube and said return tube are glued to said massive base to maintain said single flow tube and said return tube immovable with respect to said massive base;     an inlet of said return tube;     an intermediate tube connecting said outlet end of said single flow tube and said inlet end of said return tube via said second connector to extend said process material flow from said outlet end of said single flow tube to said return tube;     an outlet connector connected to said massive base for receiving said flow of said process material from said outlet end of said return tube;     said outlet connector sealably connects said outlet end of said return tube to an inlet end of an exit tube to effect the extension of said process material flow in said return tube to said exit tube;     said exit tube is adapted to extend said process material flow to a user destination.        
 
         [0092]     Preferably said pickoffs are electromagnetic devices each having a magnet and a coil.  
         [0093]     Preferably said pickoffs each comprises a light source and an optical detector with the magnitude of the Coriolis deflection of said single flow tube defining the magnitude of the output current of said optical detector.  
         [0094]     Preferably said massive base has a pair of upwardly extending parallel side walls having coaxial openings through which said single flow tube and said return tube extend.  
         [0095]     Preferably said massive base is substantially unshaped.  
         [0096]     Preferably said massive base is a solid rectangular element defining a parallelepiped; 
        said single flow tube is mounted to upwardly extending posts affixed to a surface of said massive base.        
 
         [0098]     Preferably ends of said single flow tube and said return tube extend beyond the outer surface of each leg.  
         [0099]     Preferably said single flow tube is substantially straight.  
         [0100]     Preferably Coriolis flowmeter comprises a second flow tube coupled to said massive base to define a dynamically balanced structure when vibrated by said driver while containing said process material.  
         [0101]     Preferably said driver is positioned when in use on a top surface of said single flow tube.  
         [0102]     Preferably a dynamic balancer means coupled to said massive base proximate said nodes to reduce the vibration of said nodes.  
         [0103]     Preferably said dynamic balancer means is an active dynamic balancer controlled by the exchange of signals with said meter electronics.  
         [0104]     Preferably said first and second flow tubes have an irregular shape.  
         [0105]     Preferably the mass of said massive base is at least 100 times the mass of said flow tube with material flow.  
         [0106]     Preferably the mass of said massive base is at least 1000 times the mass of said single flow tube with material flow.  
         [0107]     Preferably said driver vibrates said flow tube at a resonant frequency of said material filled flow tube.  
         [0108]     Preferably said driver vibrates said flow tube at a non resonant frequency of said material filled flow tube.  
         [0109]     Preferably said Coriolis flowmeter is adapted to extend a flow of corrosive material including nitric acid. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0110]     These and other advantages and features of the present invention may be better understood in connection with a reading of the following detailed description thereof in connection of the drawings in which:  
         [0111]      FIG. 1  discloses a perspective view of a first exemplary embodiment of the invention.  
         [0112]      FIG. 2  is a top view of the embodiment of  FIG. 1 .  
         [0113]      FIG. 3  is a front view of the embodiment of  FIG. 1 .  
         [0114]      FIG. 4  is a cross-sectional view taken along lines  4 - 4  of  FIG. 2 .  
         [0115]      FIG. 5  is a perspective view of an alternative embodiment having a pair of base elements.  
         [0116]      FIG. 6  discloses a dynamically balanced flowmeter having a U-shaped base.  
         [0117]      FIGS. 7 and 8  disclose a flowmeter having optical pickoffs.  
         [0118]      FIGS. 9 and 10  disclose flowmeters having dynamic balancers.  
         [0119]      FIG. 11  discloses a flowmeter having a pair of substantially U-shaped flow tubes.  
         [0120]      FIGS. 12 and 13  discloses another embodiment of a flowmeter having a pair of dynamically balanced straight flow tubes.  
         [0121]      FIG. 14  discloses an alternative embodiment having a single flow tube and no return tube.  
         [0122]      FIG. 15  discloses an alternative embodiment having two flow tubes vibrated in phase opposition.  
         [0123]      FIG. 16  discloses an alternative embodiment having a single flow tube. 
     
    
     DETAILED DESCRIPTION  
       [heading-0124]     Description of  FIG. 1   
         [0125]      FIG. 1  is a perspective view of a first possible exemplary embodiment of the invention and discloses a flowmeter  100  having a flow tube  102  inserted through legs  117 ,  118  of base  101 . Flowmeter  200  has a base  101 , sidewalls  119  and  120 , a front surface  116  and top wall surfaces  117  and  118 . Pickoffs LP 0  and RP 0  and driver D are coupled to flow tube  102 . Flowmeter  100  receives a process material flow from supply tube  104  and extends the flow through connector  108  to flow tube  102 . Flow tube  102  is vibrated at its resonant frequency with material flow by driver D. The resulting Coriolis deflections are detected by pickoffs LP 0  and RP 0  which apply signals over conductors  112  and  114  to meter electronics  121 . Meter electronics  121  receives the pickoff signals, determines the phase difference between them, determines the frequency of oscillation and applies output information pertaining to the material flow over output path  122  to a utilization circuit not shown. The material flow passes from flow tube  102  and through tube  106  which redirects the material flow through return tube  103  through connector  107  to exit tube  105  which delivers the material flow to a user application. This user application may be a semiconductor processing facility. The process material may be a semiconductor slurry which is applied to the surface of a semiconductor wafer to form a flat surface. The PFA material used in the flow tubes shown on  FIG. 1  ensures that the process material is free of impurities such as ions which could be transferred from the walls of metals or glass flow tubes. Locking holes  130  receive set screws  411  to fixably connect element  111  to base  101  as shown on  FIG. 4 .  
         [0126]     In use, flow tube  102  is of a narrow diameter approximating one half that of a soda straw, but with thicker walls and of negligible weight such as, for example, 0.8 gram plus 0.5 gram for the process material. This excludes the weight of the magnets. The magnets associated with the pickoffs and driver have a mass of 0.2 gram each so that the combined mass of the flow tube  102 , the affixed magnets and the process material is approximately 2 grams. Vibrating flow tube  102  is a dynamically unbalanced structure. Base  102  is massive and weighs approximately 12 pounds. This provides a ratio of the mass of the base to that of a material filled flow tube of approximately 3000. A base of this mass is sufficient to absorb vibrations generated by the dynamically unbalanced flow tube  102  with material flow.  
         [0127]     Connectors  107 ,  108 ,  109  and  110  connect tubes  104 ,  105  and intermediate tube  106  to the ends of flow tube  102  and return tube  103 . These connectors are shown in detail in  FIG. 4 . The connectors have a fixed portion  111  that includes threads  124 . The movable portion of connectors  107  through  110  are threaded onto male threads  124  to connect their respective tubes to the fixed body of the connector of which the fixed portion  111  is a part. These connectors function in a manner similar to the well known copper tubing flared connectors to connect tubes  104 ,  105  and  106  to ends of flow tube  102  and return tube  103 . Details regarding the connectors are further shown in  FIG. 4 . RTD is a temperature sensor that detects the temperature of return tube  103  and transmits signals representing the detected temperature over path  125  to meter electronics.  
         [heading-0128]     Description of  FIG. 2   
         [0129]     In  FIG. 2  is a top view of flowmeter  100  of  FIG. 1 . Pickoffs LP 0  and RP 0  and driver D each include a coil C. Each of these elements further includes a magnet which is affixed to the bottom portion of flow tube  102  as shown in  FIG. 3 . Each of these elements further includes a base, such as  143  for driver D, as well as a thin strip of material, such as  133  for driver D. The thin strip of material may comprise a printed wiring board to which coil C and its winding terminals are affixed. Pickoffs LP 0  and RP 0  also have a corresponding base element and a thin strip fixed to the top of the base element. This arrangement facilitates the mounting of a driver or a pickoff to be accomplished by the steps of gluing a magnet M to the underside of PFA flow tube, gluing the coil C to a printed wiring board  133  (for driver D), positioning the opening in coil C around the magnet M, moving the coil C upwardly so that the magnet M fully enters the opening in coil C, then positioning base element  143  underneath the printed wiring board  133  and gluing or bolting these elements together so that the bottom of base  143  is affixed by glue to the surface of the massive base  101 .  
         [0130]     The male threads  124  of connectors  107 - 110  are shown on  FIG. 2 . The inner details of each of these elements is shown on  FIG. 4 . Opening  132  receives conductors  112 ,  113  and  114 . Meter electronics  121  of  FIG. 1  is not shown on  FIG. 2  to minimize drawing complexity. However it is to be understood that the conductors  112 ,  113  and  114  extend through opening  126  and further extend over path  123  of  FIG. 1  to meter electronics  121  of  FIG. 1 .  
         [heading-0131]     Description of  FIG. 3   
         [0132]      FIG. 3  shows pickoffs LP 0 , RP 0  and driver D as comprising a magnet M affixed to the bottom portion of flow tube  102  and a coil C affixed to the base of each of elements LP 0 , RP 0  and driver D.  
         [heading-0133]     Description of  FIG. 4   
         [0134]      FIG. 4  is a sectional taken along line  4 - 4  of  FIG. 2 .  FIG. 4  discloses all the elements of  FIG. 3  and further details of connectors  108  and  109 .  FIG. 4  further discloses openings  402 ,  403  and  404  in base  101 . The top of each of these openings extends to the lower surface of the base of pickoffs LP 0 , RP 0  and driver D. The coil C and magnet M associated with each of these elements is also shown on  FIG. 4 . Meter electronics  121  of  FIG. 1  is not shown on  FIGS. 3 and 4  to minimize drawing complexity. Element  405  in connector  108  is the inlet of flow tube  102 ; element  406  in connector  109  is the outlet of flow tube  102 .  
         [0135]     The fixed portion  111  of connector  108  includes male threads  409  which screw into mating threads in base  401  to attach fixed connector portion  111  to segment  401  of base  101 . The fixed body of connector  109  on the right is similarly equipped and attached by threads  409  to element  401  of base  101 . Fixed portion  111  of connector  108  further includes a threaded portion  124  whose threads receive the movable portion  415  of connector  108 . Connector  109  is similarly equipped. Fixed portion  111  of connector  108  further includes on its left a conical stub  413  which together with movable element  415  acts as a flare fitting to force the right end of input tube  104  over the conical stub  413  of fixed portion  111 . This creates a compression fitting that sealably affixes the flared opening of supply tube  104  onto the conical stub portion  413  of fixed portion  111  of the connector. The inlet of flow tube  102  is positioned in connector fixed portion  111  and is flush with the outer surface of stub  413 . By this means, the process material delivered by supply tube  104  is received by inlet  405  of flow tube  102 . The process material flows to the right through flow tube  102  to fixed portion  111  of connector  109  where the outlet  406  of flow tube  102  is flush with the end of connector stub  413 . This sealably affixes the outlet of tube  102  to connector  109 . The other connectors  107  and  110  of  FIG. 1  are identical to those described for the details of connectors  108  and  109  on  FIG. 4 .  
         [heading-0136]     Description of  FIG. 5   
         [0137]      FIG. 5  discloses flowmeter  500  as an alternative embodiment of the invention similar to that of  FIG. 1  except that the base of the flowmeter  500  is not a single element and comprises separate structures  517  and  518 . Flow tube  502  and return tube  503  extend through the elements  517 ,  518  to connectors  507  through  510  which are comparable in every respect to connectors  107  through  110  of  FIG. 1 . Flowmeter base elements  517 ,  518  are separate and each is of sufficient mass to minimize the vibrations imparted by driver D to the dynamically unbalanced structure comprising flow tube  502 . Base elements  517  and  518  rest on surface  515  of element  516  which supports base elements  517  and  518 .  
         [0138]     All elements shown on  FIG. 5  operate in the same manner as do their corresponding elements on  FIG. 1 . This correspondence is shown by the designation of each element which differs only in that the first digit of the part designation of the element. Thus, supply tube  104  on  FIG. 1  corresponds to supply tube  504  on  FIG. 5 .  
         [heading-0139]     Description of  FIG. 6   
         [0140]      FIG. 6  discloses yet another alternative embodiment of the invention as comprising flowmeter  600  which is different from the embodiment of  FIG. 1  in that flowmeter  600  has two active flow tube  602  and  603  which comprise a dynamically balanced structure that does not require the massive base such as base  101  of  FIG. 1 . Base  601  may have significantly less mass than that of  FIG. 1 . Flowmeter  600  has connectors  607  through  610  comparable to connectors  107 - 110  of  FIG. 1 . In addition, it has connectors  611 ,  612 . Process material is received by flowmeter  600  from a supply tube  604 . The material extends via a connector  608  to the left end of flow tube  602 . Flow tube  602  extends through leg  618  of base  601  and connector  609  by means where it is connected to tube  615  which loops back via connector  607  to flow tube  603 . Flow tube  603  is vibrated in phase opposition to flow tube  602  by driver D. The Coriolis response of the vibrating flow tubes  602  and  603  is detected by pickoffs LP 0  and RP 0  and transmitted via conductors not shown to meter electronics element also not shown to minimize drawing complexity.  
         [0141]     The material flow through tube  603  proceeds to the right and extends via connector  610  to tube  606  which loops back through connector  611  and tube  616 , connector  612  to return flow tube  605  which delivers the material flow to the application process of the end user.  
         [0142]     Flowmeter  600  is advantageous in that it comprises a dynamically balanced structure of flow tubes  602  and  603  formed of PFA material. The dynamically balanced structure is advantageous in that the massive base  101  of  FIG. 1  is not required. Base  601  may be of conventional mass and vibrating PFA tubes  602  and  603  to provide output information pertaining to the material flow. The PFA flow tubes ensure that the material flow have an ultra high level of purity.  
         [heading-0143]     Description of  FIGS. 7 and 8   
         [0144]      FIG. 7  discloses a top view of a flowmeter  700  comparable to flowmeter  100  of  FIG. 1 . The difference between the two embodiments is that flowmeter  700  uses an optical detector for pickoffs LP 0  and RP 0 . The details of the optical detectors are shown in  FIG. 8  as comprising a LED light source and photo-diode together with a flow tube  702  interposed between the LED and photo-diode. At the rest position of the flow tube, a nominal amount of light passes from the LED to the photo-diode to generate a nominal output signal. A downward movement of the flow tube increases the amount of light received by the photo-diode; an upward movement of the flow tube decreases the amount of light received by the photo-diode. The amount of light received by the photo-diode translates to an output current indicative of the magnitude of the Coriolis vibration for the portion of the flow tube  702  associated with the LED and the light source. The output of the photo-diodes are extended over conductors  730  and  732  to meter electronics not shown in  FIG. 7  to minimize drawing complexity. The embodiment of  FIG. 7  is otherwise identical in every respect to the embodiment of  FIG. 1  and includes supply tubes  704 , exit tube  705  together with connectors  707  through  710  flow tubes  702  and return tube  703 . The parts of flowmeter  700  and their counterparts on  FIG. 1  and are designated to facilitate the correspondence with the only difference being the first digit of the designation of each element.  
         [heading-0145]     Description of  FIG. 9   
         [0146]      FIG. 9  discloses flowmeter  900  which corresponds to flowmeter  100  of  FIG. 1  except that flowmeter  900  is equipped with dynamic balancers  932  and  933 . Base  901  is smaller and of less mass than  101  of  FIG. 1 . The dynamic balancers function to counteract the vibrations imparted to legs  917  and  918  of base  901  by the dynamically unbalanced structure comprising the material filled vibrating flow tube  902 . In the embodiment of  FIG. 1 , these vibrations are absorbed by the massive base  101 . In this embodiment, the material filled flow tube with the attached magnets weigh approximately 2 grams while the base weighs approximately 12 pounds. This limits the range of commercial applications for which the flow tube of  FIG. 1  since the upper limit on the size and mass of the material filled vibrating flow tube  102  is limited by the mass of the base that must be provided to absorb unbalanced vibrations. Using the 3,000 to 1 ratio between the mass of the base and the mass of the material filled vibrating flow tube, an increase of one pound in the mass of the material filled flow tube would require an increase of mass of 3,000 pounds for base  101 . This clearly limits the range of commercial applications in which the flow tube  100  of  FIG. 1 .  
         [0147]     Flowmeter  900  of  FIG. 9  has a wider range of commercial applications since the dynamic balancers  932  and  933  are affixed to legs  917  and  918  to absorb much of the vibrations imparted to the legs by the dynamically unbalanced vibrating flow tube  902 . In practice, dynamic balancers (DB) may be of any type including the conventional mass and spring configuration as is well known in the art of dynamic balancers.  
         [heading-0148]     Description of  FIG. 10   
         [0149]      FIG. 10  discloses a flowmeter  1000  that is identical to flowmeter  900  except that the dynamic balancers of  FIG. 10  are of the active type (ADB) and are designated  1032  and  1033 . These active dynamic balancers are controlled by an exchange of signals with meter electronics  1021  over paths  1023 ,  1024 ,  1025  and  1026 . Meter electronics  1021  receives signals over path  1003  from active dynamic balancer  1032  representing the vibrations applied by the dynamically unbalanced vibrating flow tube  1002  to leg  117 . Meter electronics receive these signals and generates a control signal that is applied over path  1024  to active dynamic balancer  1032  to counteract the flow tube vibrations. Operating in this manner, active dynamic balancer  1032  can be controlled to reduce the vibrations of leg  1017  to whatever magnitude may be desired so hat the resulting mass of base  1001  may be of an acceptable level for commercial use of flowmeter  1000 . The active dynamic balancer  1033  mounted atop leg  1018  of base  1001  operates in the same manner as described for the active dynamic balancer mounted to leg  1017 .  
         [heading-0150]     Description of  FIG. 11   
         [0151]      FIG. 11  discloses yet another alternative embodiment comprising a flowmeter  1100  having dual flow tubes  1101 ,  1102  which are substantially U-Shaped and have right side legs  1103 ,  1104  and left side legs  1105 ,  1106 . The bottom portion of the side legs are connected to form “Y” sections  1107  and  1108  which may be connected to a suitable base not shown to minimize drawing complexity. The dual flow tubes of flowmeter  1100  vibrate as dynamically balanced elements around the axes W-W and W′-W′ of brace bars  1009  and  1010 . Flow tubes  1101 ,  1102  are driven in phase opposition by driver D affixed to the top portion of the U-shaped flow tubes. The Coriolis deflections imparted by the vibrating material filled flow tubes are detected by right pickoff RP 0  and left pickoff LP 0 . Meter electronics  1121  functions to apply signals over path  1123  to cause driver D to vibrate flow tubes  1101 ,  1102  in phase opposition. The Coriolis response detected by pickoffs LP 0  and RP 0  as transmitted over paths  1122 ,  1124  to meter electronics  1121  which processes the signals and derives material flow information which is transmitted over output path  1124  to a utilizations circuit not shown.  
         [heading-0152]     Description of  FIGS. 12 and 13   
         [0153]      FIGS. 12 and 13  disclose a dynamically balanced flowmeter  1200  having a pair of flow tubes  1201  and  1202  which are vibrated in phase opposition by driver D. The flow tubes receive a material flow; driver D vibrates the flow tubes in phase opposition in response to a drive signal received over path  1223  from meter electronics  1221 . The Coriolis response of the material filled vibrating flow tubes is detected by pickoffs LP 0  and RP 0  with their output being applied over conductors  1221  and  1224  to meter electronics which processes the received signals to generate material flow information that is applied over output path  1225  to a utilization circuit not shown.  
         [heading-0154]     Description of  FIG. 14   
         [0155]      FIG. 14  discloses an alternative embodiment  1400  of the invention comprising a massive base  1401  having an outer pair of upwardly extending sidewalls  1443  and  1445  as well as an inner pair of upwardly extending sidewalls  1417  and  1418 . A single flow tube  1402  extends from an input connector  1408  on the left through the four upwardly extending sidewalls to an output connector  1409  on the right. The flow tube  1402  is vibrated by driver D with the resulting Coriolis deflections of the vibrating flow tube with material flow being detected by pickoffs LP 0  and RP 0  which transmit signals over the indicated paths to meter electronics  1421  which functions in the same manner as priorly described or  FIG. 1 . Temperature sensing element RTD senses the temperature of the material filled flow tube and transmits this information over path  1425  to meter electronics  1421 .  
         [0156]     The flowmeter of  FIG. 14  differs from that of  FIG. 1  in two notable respects. The first is that the embodiment of  FIG. 14  is only a single flow tube  1402 . The material flow extends through this flow tube from input connector  1408 ; the output of the flow tube is applied via output connector  1409  to output tube  1406  for delivery to a user. The embodiment of  FIG. 14  does not have the return flow tube comparable to element  103  of  FIG. 1 .  
         [0157]     Also, the massive base  1401  has two pairs of upwardly extending walls whereas in the embodiment of  FIG. 1  the massive base  101  had only the single pair of upwardly extending walls  117  and  118 . The single pair of walls in  FIG. 1  performed the function of being a zero motion vibrational node as well as a mounting for connectors  107  through  110 . On  FIG. 14 , the inner pair of walls  1417  and  1418  function as a zero motion vibrational node for the ends of the active portion of flow tube  102 . The outer pair of upwardly extending walls  1443  and  1444  mount connectors  1408  on the left and  1409  on the right.  
         [0158]     When in use, process material is received from tube  1404  connected to connector  1408 . The inlet of flow tube  1402  is also connected to connector  1408 . Flow tube  1402  extends the process material flow to the right through the two pairs of sidewalls to output connector  1409  to which is connected the output tube  1406 .  
         [0159]     The part numbers on  FIG. 14  not specifically mentioned immediately above are analogous to and perform the functions identical to their corresponding elements on the previous FIGS. including  FIG. 1 .  
         [heading-0160]     Description of  FIG. 15   
         [0161]      FIG. 15  discloses an alternative embodiment  1500  which is similar in most respects to the embodiment of  FIG. 1 . The primary difference is that in the embodiment of  1500 , the rear flow tube  1503  is not dormant as is return tube  103  of the embodiment of  FIG. 1 . Instead, on  FIG. 15 , rear tube  1503  is vibrated by its driver DA with the resulting Coriolis deflections of this vibrating tube with material flow being detected by its pickoffs LP 0 A and RP 0 A. Their output signals are transmitted over paths  1542  and  1544  to meter electronics  1521  which receives these signals as well as signals from pickoffs LP 0  and RP 0  of flow tube  1502  to generate material flow information.  
         [0162]     The process material flows to right on  FIG. 15  through flow tube  1502 , through tube  1500  and flows to the left through flow tube  1503 . This phase reversal of mated pickoffs can be compensated by reversing the connections to pickoffs. LP 0 A and RP 0 A so that the Coriolis signals from all pickoffs received by meter electronics  1521  are additive to enhance meter sensitivity.  
         [0163]     The parts shown on  FIG. 15  not specifically mentioned above are identical in function to their corresponding elements on  FIG. 15 .  
         [heading-0164]     Description of  FIG. 16   
         [0165]      FIG. 16  discloses an alternative embodiment  1600  that is similar to the embodiment of  FIG. 14 . It has a base  1601 , front surface  1616 , side walls  1644  and  1641  and front wall surfaces  1644 . The differences are that upwardly extending inner  
         [0166]     mounting posts  1617  and  1618  replace walls  1417  and  1418  of  FIG. 14 . Also upwardly extending outer mounting posts  1643  and  1645  replace walls  1443  and  1445  of  FIG. 14 . Outer posts  1643  and  1645  prevent flow tube  1602  from pivoting about post  1617  and  1618  as an axis. Connectors  1608  and  1609  are optional and if desired flow tube  1602  may extend outwardly through posts  1643  and  1645  and replace inlet tube  1604  and outlet tube  1402 . The extended flow tube may be connected downstream and upstream by a user to the user&#39;s equipment. Posts  1443  and  1445  serve as a mounting for connector  1608  and  1609  when provided.  
         [0167]     It is to be expressly understood that the claimed invention is not to be limited to the description of the preferred embodiment but encompasses other modifications and alterations within the scope and spirit of the inventive concept. For example, the flowmeter embodiments shown herein may be operated in an upside down orientation it is desired to have the driver D positioned on top of a vibrating flow tube to allow the driver heat to move upward away from the flow tube. This can better isolate the flow tube from thermal stress that might degrade the accuracy or the output data of the flowmeter. Also, the Coriolis flowmeter herein disclosed has applications other than those herein disclosed. For example the disclosed Coriolis flowmeter may be used in applications in which the flowing process material is corrosive, such as nitric acid, and incompatible for use with flow meters having a metal wetted flow path.