Abstract:
A viscosimeter for measuring the relative, intrinsic or inherent viscosity of a solution in a solvent with at least one flow resistance and one feeding point for the solution to be examined in a conduit system as well as with respective manometers on the flow resistance which are coupled with a differential amplifier, wherein the viscosimeter includes flow resistances such as disk-shaped or leaf-shaped Venturi nozzles or different KV flow resistances with the smallest possible thickness and with a small volume with respect to all other parallel and following capillaries in a flow conduit system with two legs which contains in the first leg at least three pressure reducing elements, for example capillaries, whereby behind the capillary following the branch point a pressure manometer is provided for with a connected bigger vessel, whereby behind further capillaries connected with each other with different diameters and with a big volume which corresponds to 100 to 1000 times the KV flow resistance in the second leg, a branch point leads to a differential pressure sensor or a sensor for differential pressure followed by capillaries with different diameters connected with each other up to the junction in a common outlet conduit, whereby in the second leg the KV flow resistance follows the branch point, this resistance being followed by further big volume conduits which lead to the branch point of the opposing side of the differential pressure sensor or of the sensor for differential pressure, whereby further capillaries with different diameters and with different lengths connected with each other follow the branch point, these capillaries joining into the common outlet conduit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a viscosimeter for measuring the relative intrinsic or inherent viscosity of a solution in a solvent. 
     2. Description of the Related Art 
     According to the state of the art, the difference is made between the relative, the specific as, well as the inherent viscosity, and finally, the limiting viscosity number (intrinsic viscosity). By relative viscosity, we understand the quotient of the viscosity of the solution, for example of a polymer, to the viscosity of the pure solvent. The inherent viscosity results as the quotient of the natural logarithm of the relative viscosity divided by the concentration in gram of the dissolved substance per millimeter solution. There results herefrom the intrinsic viscosity as a limiting value of the inherent viscosity for the case that the aforesaid concentration goes towards zero. The so-called Hagen-Poiseuille&#39;s formula is fundamental for viscosity measures. According to the state of the art, individual capillary measures are known for which the volume rate of the solution flow and the flow pressure drop are measured and, the geometric dimensions of the capillars being known, the viscosities of the examined liquids can be determined herefrom. The disadvantage of this measuring method consists in the unfavorable signal-to-noise ratio. The noise is essentially produced by high-frequency interfering signals of the pump which is required for conveying the substance to be examined. Moreover, irregular flow rates of the substance including the counterpressure fluctuations produce interfering signals on flow resistances. Finally, it is known that the viscosity is of course temperature-dependent, for which reason variations of temperatures during the measure can distort the measuring result. 
     According to the U.S. Pat. No. 3,808,877, to solve this problem, a flow limiter is used between the solvent feeding point and the measuring capillaries to produce a constant flow rate. The relative viscosity is determined by separate measures of the pressure drop on the capillary for the direct flowing polymer solutions and for the pure solvent. From this printed document, a device of two capillaries in parallel running legs is also known, one of them being filled with the polymer solution and the other one with the solvent. Basically, separated measures of said substances are also possible in such a way that the first substance flows through the first capillary and the second substance through the second capillary of a conduit during the measuring, whereby these capillaries are connected in series the one behind the other. The condition for carrying out an exact viscosity determination is in particular the geometric coincidence of the diameter and of the length of the used capillaries, likewise a temperature uniformity at the measuring points. 
     According to the EP 0 181 224, a capillary viscosimeter is proposed with two capillaries connected in series for which one serves as a reference capillary only for the solvent and the second as an analysis capillary for the polymer solvent solution. The capillaries consist of long thin tubes into which the solvent is introduced through a pump. A resistance path in the form of a tube with a small diameter is between the pump and the reference capillary which serves to produce a counterpressure. A further pulse attenuator can eventually be added to this resistance path. The differential pressure measured in the reference capillary (pressure drop) is supplied to a differential amplifier or to an evaluating unit just as the pressure drop which is measured on the analysis capillary. The feeding point for the substance to be examined, for example a polymer, is between the reference capillary and the analysis capillary so that the analysis capillary is traversed by a solution consisting of the polymer and the solvent. This arrangement connected in series can be changed as far as the feeding point for the test substrate can also be situated before the first capillary. 
     In this case, the first capillary becomes the analysis capillary. After having passed through it, the solution flows into a retaining vessel which assumes the function of diluting the solution further so that substantially only the solvent is measured by the reference capillary. In the described arrangement, a gel permeation chromatograph can be placed between the feeding point, for example for the polymer, and the analysis capillary, chromatograph in which polymer substances can be separated in a dilution solution according to their molecular size. 
     Besides the series connection described above, capillary bridge viscosimeters are also still known which are characterized by a relatively high sensitivity. In the bridge connection, a conduit is separated into two parallel running conduit parts in which there are respectively two capillaries connected in series. A place situated between the respectively first and the second capillary of each leg is connected with the corresponding place of the other leg over a connection conduit in which a high sensitive pressure sensor is placed. 
     According to the embodiment described in the EP 0 113 560, a retention basin in the form of a switchable bypass device is moreover provided for before the second capillary of a leg. As far as all existing four capillaries are flown through by the same liquid—and in particular without including the bypass—the connection conduit remains unpressurized. However, if a storage tank is placed above the bypass conduit, the second measuring capillary is substantially only flown through by the solvent so that there results a pressure drop with respect to the other measuring leg because of the different viscosities of the liquids. This pressure drop can be recorded and can be used for determining the viscosity. 
     Moreover, from EP 0 083 524, we still know devices with only one capillary which are supposed to have a length of several meters for a diameter between 0.2 and 0.3 mm. This capillary with a total length of, for example 3 mm, is wound in form of a loop with a diameter of at least 10 cm. 
     SUMMARY OF THE INVENTION 
     The aim of this invention is to improve the device mentioned in the introduction in order to avoid the detector dispersion appearing until now because of the used capillaries or to considerably reduce it and thus to increase the measuring accuracy of the device so that the least pressure differences are measurable. 
     According to an embodiment of the invention, a flow resistance with the smallest possible volume is used in the sample flow leg (hereunder designated as KV flow resistance), this flow resistance being placed directly behind the feeding point of the flow division. Accordingly, the viscosimeter shows flow resistances, such as disk-shaped or leaf-shaped Venturi nozzles or different KV flow resistances, with the smallest possible thickness and with a small volume with respect to all other parallel and following capillaries in a flow conduit system with two legs. This flow conduit system contains in the first leg at least three pressure reducing elements, for example capillaries, whereby behind the capillary following the branch point a pressure manometer is provided for with a connected bigger vessel, whereby behind further capillaries connected with each other with different diameters and with a big volume which corresponds to 100 to 1000 times the KV flow resistance in the second leg, a branch point leads to a differential pressure sensor or a sensor for differential pressure followed by capillaries with different diameters connected with each other up to the junction in a common outlet conduit. In the second leg, the KV flow resistance follows the branch point, this resistance being followed by further big volume conduits which lead to the branch point of the opposing side of the differential pressure sensor or of the sensor for differential pressure, whereby further capillaries connected with each other with different diameters and with different lengths follow the branch point, these capillaries joining into the common outlet conduit. 
     The viscosimeter comprises an inlet which runs into a junction from which the one capillary in one first leg leads over a big distance and with a comparatively big volume to a manometer (absolute pressure manometer) and from this to a still bigger vessel which has a 100 times to 1000 times bigger volume than the volume of the KV flow resistance in the second leg, a connecting conduit leading from the vessel to a pressure reducing element which is a capillary, a nozzle, a frit, or an appropriate supplying conduit which reduces the pressure in the flow conduit. The pressure reducing element is connected over a connection with a further capillary with a big volume which runs into the branch point, whereby the differential manometer or the sensor for differential pressure placed in the connecting conduit between the two branch points in both legs measures high sensitively the slightest pressure differences between the two branch points of the flow conduit. The big volume capillary following the connecting point leads over a connection to a further pressure reducing capillary, whereby the pressure reduction must not be identical with that in the upper section of the flow conduit. A connecting conduit follows the capillary into the junction of both legs to a common outlet conduit which makes possible the common discharge of the solvents from different flow lines. From the branch in the second leg, a pressure reducing element which can have different configurations leads directly into a big volume vessel and from there into a conduit with a big internal diameter which is connected by the branch with the differential manometer or differential pressure sensor, whereby the differential pressure sensor is switched here in such a way that it generates a positive signal for a pressure drop at the branch point, a conduit with a big internal diameter following the branch point, this conduit being connected over the connection with a pressure reducing capillary and constituting the access to the junction and to the outlet conduit. 
     The viscosimeter according to another embodiment also shows flow resistances, such as disk-shaped or leaf-shaped Venturi nozzles or different KV flow resistances with the smallest possible thickness and a small volume compared with all other parallel and following capillaries in a flow conduit system with two legs. Unlike the viscosimeter according to the first embodiment, the flow conduit system shows three parallel flow circuits among which at least two flow circuits are connected by a differential pressure sensor or sensor for differential pressure. These three flow circuits constitute an analogy to the Thomson bridge. The arrangement itself consists of an inlet which runs into a branch and divides into two legs, whereby one of the two legs comprises a pressure reducing element, a following branch point to a differential pressure and a pressure reducing element in the feeding conduit to a junction which runs into an outlet conduit. The other leg starting from the branch point comprises a pressure reducing element which leads to a branch which first leads into a big volume vessel leading to a junction and second which leads to a resistance capillary which is connected in the junction with the differential pressure sensor or the sensor for differential pressure and which is furthermore connected with a resistance capillary in the conduit led from the junction to a further junction, whereby the resistance capillary is connected on the outlet side over the junction with a pressure reducing element which runs over a conduit section into the junction and thus into the outlet conduit. 
     The invention according to another embodiment consists in that the viscosimeter shows flow resistances, such as disk-shaped or leaf-shaped Venturi nozzles or different KV flow resistances, with the smallest possible thickness and a small volume compared to all other parallel and following capillaries, whereby these flow resistances are placed directly behind the feeding points of the flow division and in the other partial leg behind the flow division there follows a long conduit with a big internal diameter which is furthermore more precisely defined by the fact that the capacity of this long tube amounts to 100 to 1000 times the KV flow resistance. 
     The KV flow resistance can be a very short capillary piece with a small internal diameter which is considerably lower than all other following or parallel running capillaries, a so-called microsystem technique component, for which engravings are built into the silicium basic material by photolytic methods and which can be connected in combination with external macroscopic flow resistances with viscosimeters according to the invention. 
     Furthermore, a KV flow resistance can also be created in that the flow resistances can be used for example in form of disk-shaped or leaf-shaped Venturi nozzle bodies with the smallest possible thickness. Here, the low spatial or volumetric dimension is decisive, which is advantageous in that, because of the favorable ratio of volume, the sample can be decomposed into nearly infinitesimal signal sizes in time and thus a systematic enlarging of the measuring signals through the measuring system, as it is observed for all measuring cells used according to the state of the art, is avoided. This enlarging had to be corrected, for example mathematically, up to now as far as this was possible. For example in the case of the Venturi nozzle body, the thickness should be smaller or bigger than 2 mm, preferably 2 mm or 3 mm. Preferably, the Venturi nozzle body flow opening is circular of slit-shaped. Alternatively, the nozzle body can however also have several hole-type openings of 1μ to 10μ. The channels of the microsystem technique components can have structures with a width of 10μ to 100μ. The same is valid for so-called fused silica capillaries and capillaries with which corresponding ratios of volume can be realized because of their internal diameter. 
     Basically, the KV flow resistance according to the invention can be used in all viscosimeters in which capillaries have been used until now. However, because of the high measuring accuracy which can be achieved, a bridge arrangement is chosen with two parallel running flow paths in which, among respectively three flow resistances placed the one behind the other, one KV flow resistance is at least respectively in one leg. Apart from that, the bridge arrangement known from the state of the art and described for example in the EP 0 113 560 can be gone back to. 
     Moreover, preferably a KV flow resistance, for example a Venturi nozzle or a microsystem technique channel is directly behind a gel permeation chromatography column, this being seen in flow direction, which is fundamentally known according to the state of the art with respect to its structure as well as to its mode of operation and which is already used for example in a viscosimeter arrangement according to EP 0 181 224. 
     With respect to Venturi nozzles existing one behind the other or in a branched bridge arrangement, a big volume retention basin can be provided for in the supply network for increasing the measuring speed. The function of these retention basins is basically known by the state of the art from the aforesaid printed documents, in series arrangements as well as in bridge arrangements. 
     For checking or for further detection, it can be advantageous to place a refraction detector or a membrane osmosis detector in the supply network. Further detectors are conceivable in specific combinations and represented in FIGS. 12 to  14 . 
    
    
     For avoiding temperature variations and thus for increasing the measuring accuracy, it is finally recommended to place the whole supply network in a thermally constant closed space, preferably in a thermally adjustable heat bath. The invention will be explained in detail below with reference to concrete embodiments. 
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows the flow profile of a sample in a capillary. 
     FIG. 1A shows the flow profile of a sample with a high flow rate or a high molecular weight. 
     FIG. 2 shows the signal course of a sample which flows through the cell with a rectangular flow profile. 
     FIG. 3 shows a curve course according to FIG. 2 by considering the real flow profile of a sample as well as in dotted lines by considering the flow profile represented in FIG.  1 A. 
     FIG. 4 shows a representation of two measuring signals of different detectors with a different layer thickness. 
     FIG. 5 shows the signal course by using a KV flow resistance according to the invention. 
     FIGS. 6 to  14  show respectively schematic arrangements of viscosimeters according to the invention. 
     FIG. 15 is an annex with formulae. 
     FIG. 16 shows the arrangement in form of a flow chart of a further embodiment of the viscosimeter according to the invention. 
     FIG. 17 shows the arrangement in form of a flow chart with three parallel flow circuits of a further embodiment of the viscosimeter according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     When a capillary  10  is flown through by a liquid in direction of a part  11  represented in FIG. 1, it shows the parabolic flow profile known according to the state of the art. As may be seen in FIG. 1, this is also valid for the case that a sample  13  is given into an eluent  12 , for example in form of a drop. 
     For a finite layer thickness of a cell  10  and an ideal sample with a rectangular flow profile, there results the signal course represented in FIG. 2 for which at the time t 1  the sample enters the cell, whereby there is a mixture between the sample and the eluent in the cell up to the time t 2 . From the time t 2 , the sample fills the cell completely, namely until the time t 3  from which the eluent  12  is charged later. At the time t 4 , the sample  13  has completely left the cell, there is only the eluent therein. 
     If we consider the real flow profile according to FIG. 1, there results the signal course which can be seen in FIG. 3 in which during the period between t 1  and t 2  the sample  13  with its parabolic front flows into the cell. The same is valid by leaving the sample  13  with respect to the period between the times t 5  and t 6  in which the curve course is not linear. Due to this curve course which is not linear, the analysis is however considerably complicated. A further complication appears when, in case of high flow rates and samples with a high molecular weight with a corresponding concentration, a flow profile according to FIG. 1A is constituted. For these cases, there results the signal course represented in dotted lines in FIG. 3 which only allows relative relations. 
     The signal is completely insoluble when two detectors emit output signals A and B which have, for example, the idealized time history represented in FIG.  4 . It comes regularly to a so-called offset C of the detectors because of the distance differences for the sample stopper  13 . Moreover, there results, because of different layer thicknesses of the cells  10 , a different edge steepness of both signals A and B. 
     The different times concern the following states: 
     t 1 : The sample enters the cell  10  of the first detector. 
     t 2 : The cell  10  is fully filled, the sample  13  enters the second cell. 
     t 3 : The second cell is also fully filled. 
     t 4 : The sample leaves the first cell. 
     t 5 : The sample leaves the second cell. 
     t 6 : The first cell is fully filled again with eluent and 
     t 7 : The second cell is also filled with eluent. The parabolic form of the flow profile is not yet taken into account, what leads to a further complication for a signal course, as represented in FIG.  3 . 
     Apart from the different signal courses, there remains, in the analytic practice, further the problem that in many cases no plateaus are constituted what results in that intrinsic properties and systematic errors cannot be distinguished any longer. 
     This invention remedies, as FIG. 5 shows with the curve for a viscosimeter with a small thickness of the KV flow resistance. The times t 1  and t 2  represent the inlet of the sample  13  into the KV flow resistance or the outlet of the sample thereof. Before and after these times t 1  and t 2 , the eluent is respectively in the KV flow resistance. As may be seen in FIG. 5, we obtain not only quasi signal rectangular courses, i.e. the omission of the leading eges and of the trailing edges, but in the case of the use of two detectors, also definite resolution possibilities. This also results from the following theoretical considerations: 
     The pressure drop which is registered by the pressure sensors is related to the viscosity by the following known relations:              n   =         π   ·     R   4         8   ·   L       ·       Δ                 P     Q               (   1   )                 γ   .     =       4     π   ·     R   3         ·   Q             (   2   )               σ   =         R     2   ·   L       ·   Δ                   P             (   3   )               I   =     Q   =       A   1     ·       L   ·         2   ·   Δ                   P       [       (       A   1       A   2       )     -   1     ]                       (   4   )                                
     Here, 
     n=viscosity of a Newton liquid 
     L=thickness of the KV flow resistance 
     A=cross section of the flow opening (or frit pore) 
     R=radius of the opening (or frit pore) 
     Q=flow rate through the opening and 
     p=pressure drop at the opening over the thickness (or the direct flow length) 
     Unlike the capillary viscosimeter according to the state of the art, the Venturi equation stated above as equation 4 is included in the viscosity definition according to the equation 1. Thus, the error resulting of the different frictional force which appears in capillary viscosimeters is avoided, what is clear by the following conversion of the equation 1: 
     
       
         
           F 
           r 
           =R 
           2 
           πΔp  
         
       
     
     Along the way that a sample covers in a capillary, there results a different frictional force as well as other shearing forces so that, despite a supposed homogeneity of the probe, the detected pressures are different. On the other hand, with this invention, it is not a mean value of the pressure difference which is constituted, as it is usual for capillary measurements, but the pressure respectively corresponding with the viscosity is exactly indicated. 
     The KV flow resistance can principally also be configured as a frit, a filter, or a membrane, as far as it constitutes a flow channel taper and it simultaneously possesses the smallest possible thickness (or length). 
     The arrangement of the KV flow resistances in different assemblies can be seen in FIGS. 6 to  14 . 
     The arrangement according to FIG. 6 possesses an inlet opening  14  into which the eluent  12  is introduced, eventually after filtration. The lead-through conduit possesses two KV flow resistances placed in series  15  and  16  over which the pressure drop can be respectively measured with pressure sensors  17  and  18 . Both values measured by the pressure sensors  17  and  18  are supplied to a differential amplifier  19 , are amplified there and treated in the usual manner. 
     The sample solution is supplied over the supply pipe  20  into the loop of a valve  21 . The pressure drop which results because of the flowing through of the pure solvent (eluent) is thus measured at the KV flow resistance  15 , while the pressure drop which is caused by a solution composed of solvent and sample is measured on the nozzle body  16 . The solution leaves the measuring device by the outlet  22 . 
     The arrangement represented in FIG. 7 possesses, in contrast to the arrangement described above, a retention basin  23  instead of the loop of the valve  21 . Compared with the arrangement described above, the solvent is examined with the sample in the first KV flow resistance  15  which serves here as analytical appliance. If the sample comes into the retention basin  23 , it is there considerably diluted and moreover retarded in time in such a way that the KV flow resistance  16  measures only or at least substantially only the solvent. The resistances of this arrangement must not be balanced since their variations do not influence the result. 
     FIG. 8 shows the principally known bridge arrangement for which the supplying conduit  24  is separated into two partial conduits  25  and  26  which have KV flow resistances  27  and  28  or  29  and  30  respectively placed in series. The conduits  25  and  26  join behind the KV flow resistances  28  and  30  to an outlet conduit  31 . A bridge conduit  32  with a highly sensitive pressure detector  33  is between the KV flow resistance  27  and  28  on the one hand and the KV flow resistance  29  and  30  on the other hand. Additionally, there are still a retention basin  34  of the above described type in the conduit  26  and a compensating vessel  35  in the conduit  25  before the KV flow resistance  28  for the temperature conditioned expansion of the liquid, this being seen in flow direction, as well as a tank  36  from which the sample solution can be given into the eluate. A safety valve  37  is switched in parallel for the protection of the highly sensitive pressure measuring device  33 . 
     In this bridge arrangement, the KV flow resistances  27  and  29  can be configured for example with the smallest possible thickness while the flow resistances  28  and  30  are configured as capillaries. It is also possible that only  29  is configured as a KV flow resistance and the supplying conduit  25  is placed in as a very long capillary with a big internal diameter, all other parts  27 ,  28 , and  30  being configured as capillaries. In the same way, the parts  27  to  29  can also be configured as KV flow resistances with the smallest possible thickness and the part  30  as a capillary or all parts  27  to  30  as KV flow resistances of the above mentioned type. 
     The solution displaced through the inlet conduit  24  and with the sample is separated approximately in the ratio 1:1 and flows through the conduits  25  and  26 . After having flown through the KV flow resistance  29 , the solution is diluted in the retention basin  34  and the pure solvent which is therein is then extruded. But in the leg  25 , the solution does not undergo any concentration change so that respectively different pressure drops are registered at the KV flow resistances or capillaries  28  and  30 , these pressures drops being measurable by the pressure sensor  33 . The measured pressure is proportionate to the viscosity of the sample solution in the measuring leg  25 . 
     FIG. 9 shows in the inlet conduit an admission pressure sensor  44  which measures the pressure drop over the whole capillary arrangement. In the branch conduit  25 , from the branch point with a vessel with a big internal diameter, a dilution vessel  35  and downstream an aforesaid capillary is connected. The second conduit part  26  is comparatively short up to the KV flow resistance  29  in order to run into a dilution vessel behind  29 . The volumes of the vessel and of the supplying capillaries are big in comparison with the volume of  29 . The part of the arrangement lying behind the part near the pressure sensor  33  again corresponds to the arrangement of FIG.  8 . The working principle of FIG. 9 differs from that of FIG. 8 in that the signal detection takes place completely differently in the front part of the arrangement. As soon as the sample stopper enters the partial leg  26  and reaches the KV flow resistance, a signal value is determined, since the sample part which is simultaneously eluted in the partial leg  26  has to flow through the wide big volume vessels and the dilution vessel. Here, the already described dilution and retardation take place so that the rise of pressure recorded in the partial leg  26  is not compensated (as this is the case for the arrangement described in FIG.  8 ), but can be measured. The components following behind the diagonal leg (in  33 ) only serve by appropriately selecting the resistances to fix the distribution ratio of the flow between  25  and  26 . Due to this arrangement, more than 50% of the sample can be used for the further increase of sensitivity. 
     According to FIG. 10 which is substantially constituted like the arrangement according to FIG. 8, a gel permeation chromatograph column  38  is inserted between the first and the second flow resistances  29  and  30  in the leg  26 , column from which the polymer stopper emerges and directly enters the taper of the nozzle  30 . The pressure drop takes place after the shortest distance, whereby the sample is not enlarged. Preferably, the whole arrangement is in a sealed space  39  which guarantees the constancy of temperature. For the differential measurement carried out, a compensation of the temperature flow fluctuation can eventually be performed, if necessary. 
     As indicated in FIG. 11, the arrangement  40  represented for example according to one of FIGS. 6 to  14  can also be connected to a refraction detector  41  or basically to further detectors which can give further information about the physical or chemical constitution of the sample. Here, the RI detector can also be divided and inserted into the two partial legs, as represented in FIG.  13 . The same is valid for further detectors, such as membrane osmometers, laser scattered light detectors and others. Both possible types of placing are represented in FIGS. 12 and 14. 
     Furthermore, it is possible to have a block-type arrangement of the detectors, for example in an arrangement in a row, whereby the first detector is the viscosimeter. By omitting a partial flow, a single-capillary viscosimeter is obtained, whereby a vessel or a container with a comparatively big volume is placed before the measuring capillaries. The pressure measurement is then performed between the big volume vessel and the measuring capillaries. A sufficient quantity of the sample solution is then available in the big volume vessel in order to displace the solvent so that the sample is then conveyed to the first measuring cycle. In this way, high-purity measurements are carried out since the measure is based only exclusively on the sample solution. 
     According to a further embodiment of the invention according to FIG. 16, an arrangement for a viscosimeter with a flow conduit system with two legs L 1 , L 2  is provided for. The first leg L 1  comprises at least three pressure reducing elements, whereby behind the capillary  103  following a branch point  102 , a pressure manometer  104  with a consecutive bigger vessel  105  is provided for. In the conduit after the branch point  102 , further capillaries  106 ,  108  with different diameters and with big volumes, which are connected by a junction  107 , are provided for which correspond to 100 to 1000 times a KV flow resistance  221  in the second leg L 2 . In the conduit of the leg L 1  leading from the branch point  102 , a further branch point  109  follows the capillaries  106 ,  108 , this branch point leading to a differential pressure sensor or to a sensor for differential pressure  122 . A conduit section with two capillaries  110 ,  112  with different diameters which are connected with each other by a junction  111  follows this branch point  109 . The conduit section of the leg L 1  which shows the capillaries  110 ,  112  runs into a junction  113  and from there into an outlet conduit  114 . In the other leg L 2 , the KV flow resistance  221 , which is followed by further big volume conduits, follows the branch point  102 . The conduit section which receives the big volume conduits and the KV flow resistance  221  leads to a branch point  118  which is connected by a conduit section with the branch point  109 , whereby the differential pressure sensor or the sensor for differential pressure  122  is placed. From the branch point  118  in the leg L 2 , there follows a conduit section which leads to the junction  113 , and thus, into the outlet conduit  114 . Capillaries  115 ,  117  with different diameters and with different lengths, which are connected with each other by a conduit  116 , are placed in this conduit section. In this arrangement for the viscosimeter, the liquid supply takes place over the inlet  101  and from the junction  102  into leg L 1  or into leg L 2 . From this junction  102 , a conduit section leads to the branch point  109 . In this conduit section, the capillary  103  is led over a big distance with a comparatively big volume to a manometer (absolute pressure manometer)  104  and from there to a still bigger vessel  105  which is then followed by the conduit section with the two capillaries  106 ,  108 . The two capillaries  110 ,  112  with different diameters which are connected with each other by a conduit  111  are placed in the conduit section following the branch point  109 . From the vessel  105  in the leg L 1 , a connection conduit leads to a pressure reducing element  106  which is a capillary, a nozzle, a frit, or an appropriate device which reduces the pressure in the flow conduit, whereby all other pressure reducing elements which are used can be configured in the same way. This pressure reducing element  106  is connected by the conduit  107  with a further capillary  108  with a big volume which runs into the branch point  109 , whereby the differential manometer or the manometer for differential pressure  122  placed in the connecting conduit between the two branch points  109 ,  118  in the two legs L 1 , L 2  is highly sensitive and shows the slightest pressure differences between the two branch points  109 ,  118  of the flow conduit. The big volume capillary  110  which is placed in the conduit section following the branch point  109  is connected by the conduit  111  with a pressure reducing capillary  112 , whereby the pressure reduction must not be identical with that in the upper section of the flow conduit. 
     The conduit branch L 2  derives from the junction  102 . The pressure reducing element  121  which can be configured in different ways is placed in this leg L 2 . The big volume vessel  120  directly follows this pressure reducing element  121 , vessel from which a conduit  119  with a big internal diameter then leads to the branch  118 . From this branch  118 , it then leads over the conduit section with the inserted differential manometer or manometer for differential pressure  122  to the junction  109 . In the area of the conduit branch L 2 , a conduit section leads from the junction  118  to the outlet conduit  114  and a conduit  117  with a big internal diameter is then provided for in this conduit section. The conduit then leads over the junction  116  to the pressure reducing capillary  115 . The differential pressure manometer or manometer for differential pressure  122  is connected in such a way that it generates a positive signal for a pressure drop at the branch point  118 . This is also the way how the viscosity signal is generated. 
     The viscosimeter according to FIG. 17 shows a flow chart different from that of the viscosimeter according to FIG. 16 in so far as three parallel flow circuits are provided for which constitute an analogy with the so-called Thomson bridge. This arrangement stands out in particular in case of low flow rates for which the resistances of supply conduits, even if slight, influence the accuracy of measurement. As shown in FIG. 17, a flow conduit system with two legs L 1 , L 2  is provided for the viscosimeter. This flow conduit system comprises three parallel flow circuits, at least two of them are connected by a differential press u ire sensor or a sensor for differential pressure  216 . The arrangement itself consists of an inlet  201  which runs into a junction  202  and divides into two legs L 1 , L 2 . The leg L 1  comprises a conduit section with a pressure reducing element  203 , a following branch point  204 , and a further pressure reducing element  205 . This conduit section runs into a junction  206  with a following outlet conduit  207 . The other leg L 2  which starts from the branch point  202  comprises a pressure reducing element  212  which is followed by a junction  211 . In connection with this junction  211  there follows a big volume vessel  210 , whereby a further junction  209  and a pressure reducing element  208  are placed in the following conduit section. This conduit section leads to the outlet conduit  207 . Both junctions  211 ,  209  are connected over conduit sections with a junction  215  which is again connected with the branch point  204  over a conduit section. The differential pressure sensor or the sensor for differential pressure  216  is placed in this conduit section. A resistance capillary  213 ,  214  is respectively placed in each of the two conduit sections between the junctions  211  and  209  and the junction  215 . A flow conduit system with three parallel flow circuits is obtained on the base of this arrangement.