JP2009133726A - Viscometer for liquid chromatograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a viscosity detection device for a liquid chromatograph hardly generating tailing of a viscosity signal, capable of measuring highly accurately a viscosity change of liquid having a small flow rate. <P>SOLUTION: An equilibrium bridge type viscosity detection device 24 is equipped with a displacement detection means 46 for detecting displacement of a diaphragm 44 to a reference position, a displacement suppression means 48 for applying a displacement suppression force to the diaphragm 44 so that displacement of the diaphragm 44 is reduced, and a viscosity calculation means 52 for calculating the viscosity of fluid by a displacement suppression force value by the displacement suppression means 48. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an improvement in a viscosity detection device, particularly a viscosity detection device using a diaphragm type differential pressure transducer.

  In order to measure the size and molecular weight of the polymer substance contained in the eluent of the liquid chromatograph, usually an analytical column that can be separated by molecular size etc. with a porous gel, and a differential refractive index detector or An ultraviolet absorption detector is widely used.

  By the way, there is a large difference in the behavior of polymer substances depending not only on the molecular weight but also on the size, such as the degree of spatial development. Therefore, a polymer substance with a known size, molecular weight, and concentration is used as a sample in advance, and the relationship between each characteristic and the elution position is obtained and compared with the elution position of the unknown polymer substance. Size or molecular weight can be estimated. Further, the concentration can be obtained from the magnitude of change in ultraviolet absorbance or refractive index.

  Generally, ultraviolet absorbance and refractive index depend on weight concentration, and viscosity depends on weight concentration, molecular size, and molecular weight. Therefore, size or molecular weight can be determined by measuring refractive index and viscosity, or ultraviolet absorbance and viscosity simultaneously. Information on the can be obtained directly.

By the way, when it is necessary to measure the viscosity in a minute amount continuously like the eluent of the liquid chromatograph apparatus, a viscometer using a capillary bridge is often used.
Examples of viscometers using this capillary bridge are disclosed in Patent Documents 1 to 3. In other words, the capillary bridge is basically a structure in which four capillaries (capillaries) having the same length and inner diameter are connected in a bridge shape. Each capillary tube is filled with a carrier solution, and a sample solution ( Usually, when a carrier liquid containing a polymer substance) is fed into one capillary, the pressure generated at both ends of the capillary varies depending on the difference between the sample liquid viscosity and the carrier liquid viscosity. Therefore, the viscosity of the sample liquid can be obtained from the pressure difference at the midpoint of the bridge. When continuously measuring the viscosity, the sample liquid stays or dilutes between either the downstream tubule and the middle point of either one of the series-paired tubules, and the fluid flowing through the previous tubule has a viscosity. A dilution tube or a delay tube is provided so that it does not flow directly into the downstream tubule during the measurement period. A diaphragm type differential pressure transducer is often used for measuring the pressure difference at the midpoint.

  When a diaphragm type capillary bridge viscometer is used as a liquid chromatograph viscometer, a stainless capillary or PEEK capillary having an inner diameter of 0.2 to 0.4 mm and a length of several tens of cm to several m is used as the capillary. The flow rate flowing through the viscometer varies depending on the size of the analytical column, but is usually 0.2 to 0.3 ml / min to 2 to 3 ml / min.

  When the displacement of the diaphragm is detected by a variable reluctance type differential pressure transducer, the coils are normally arranged close to each other on both sides of the diaphragm made of a magnetic material. Further, the peripheral portion of the diaphragm has a pleat shape so that the central portion of the diaphragm can be easily moved in parallel by the differential pressure while maintaining a flat surface. When a differential pressure is generated on both sides of the diaphragm, the diaphragm surface moves a maximum of 0.025 to 0.05 mm, the distance between the coil and the diaphragm changes, and the reluctance changes. An AC voltage of about 5 V (effective value) and about 3 to 5 kHz is applied to both ends of both coils connected in series with reverse polarity. When there is no difference in the reluctance between the two coils, no AC voltage is generated at the connection point between the two coils, but when there is a difference in the reluctance, an AC voltage is output according to the difference value.

  In general, in a variable reluctance type differential pressure transducer, the diaphragm is made of a soft magnetic material with low hysteresis. By changing the rigidity of the diaphragm by changing the thickness or the like, the displacement amount of the diaphragm with respect to a predetermined differential pressure can be changed, and the detection sensitivity of the differential pressure can be adjusted.

  By the way, in liquid chromatographs, in recent years, in order to reduce the consumption of eluent and shorten the analysis time in order to deal with a small amount of sample, the particle diameter packed in the analytical column and the analytical column diameter have been reduced. Is progressing. Therefore, an eluent flow rate of 0.2 to 0.3 ml / min or less has been increasingly used.

  When the flow rate of the liquid chromatograph is reduced, when a capillary having the same diameter is used for the capillary bridge, the pressure generated between both ends of the capillary is reduced. Therefore, in order to generate a pressure that can be detected at a low flow rate, it is necessary to use a narrow tube having a smaller diameter or a differential pressure transducer with higher sensitivity. However, it has been clarified that the peak of the viscosity signal tails when a thin tube having a diameter of 0.2 mm or less is used. On the other hand, when an investigation such as a differential refractometer is connected downstream of the viscometer, the tailing of the viscosity signal is not caused by the spread of the peak component.

  Also, if the sensitivity of the differential pressure transducer is increased by making the diaphragm thinner, providing more folds around the diaphragm, or making the diaphragm with a material rich in elasticity, etc. Similarly, it was found that the peak of the viscosity signal tails.

JP 59-160740 A Japanese Patent Laid-Open No. 11-83823 Japanese National Patent Publication No. 11-514744

  The present invention has been made in view of the above prior art, and the problem to be solved is to provide a viscosity detection device that is less likely to cause tailing of the viscosity signal and that can measure the viscosity change of a small flow rate liquid with high accuracy. There is.

In order to solve the above problems, an equilibrium bridge type viscosity detection apparatus according to the present invention is provided.
A standard that is installed between the downstream tube and the midpoint of either one of the series-paired tubes, and the fluid that flows in through the upstream tube stays or dilutes during the viscosity measurement period, and introduces the reference viscosity fluid into the downstream tube Viscosity adjusting means;
A displacement detecting means for detecting displacement relative to a reference position of the diaphragm;
A displacement restraining means for applying a displacement restraining force to the diaphragm so as to reduce the displacement of the diaphragm;
Viscosity calculation means for calculating the viscosity of the fluid from the displacement suppression force value by the displacement suppression means;
It is provided with.

  In the apparatus, the diaphragm includes a magnetic material, and the displacement suppression means includes a solenoid coil disposed on the outer periphery of the diaphragm, and excites the solenoid coil based on a detection result by the displacement detection means to displace the diaphragm. It is preferable to apply a restraining force.

In the apparatus, the displacement suppression means includes a fluid pump, and injects liquid into the midpoint when the pressure at the midpoint where the reference viscosity adjusting means is installed becomes lower than the pressure at the other midpoint. Alternatively, when the pressure at the midpoint becomes higher than the pressure at the other midpoint, it is preferable to suck the liquid from the midpoint and apply a displacement suppression force to the diaphragm.
Further, in the apparatus, the displacement suppression means includes at least a pressure regulating valve disposed on the downstream side of the narrow tube series pair, and applies a displacement inhibiting force to the diaphragm by adjusting the opening of the pressure regulating valve. Is preferred.

In the apparatus,
The diaphragm contains a magnetic material,
The displacement detection means includes detection coils arranged on both sides of the diaphragm, and magnetically detects which detection coil is close to the diaphragm,
Preferably, the displacement suppression means applies a displacement suppression current to one of the detection coils in a superimposed manner in accordance with the displacement of the diaphragm.

  In the above apparatus, it is preferable that the displacement suppression means supplies a direct current to any one of the detection coils via a choke coil in accordance with the displacement of the diaphragm.

  The liquid chromatograph viscosity detecting apparatus according to the present invention has the displacement suppressing means for suppressing the displacement of the diaphragm as described above, and does not calculate the viscosity from the displacement amount of the diaphragm, but suppresses the displacement of the diaphragm. Since the viscosity is calculated from the necessary suppression force value, it is not necessary to measure the displacement amount of the diaphragm strictly, so that the detection accuracy can be improved and the sensitivity of the transducer is improved. It is possible to suppress tailing that occurs in

Preferred embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a schematic configuration of a liquid chromatograph 10 to which the present invention is applied.
The liquid chromatograph 10 shown in FIG. 1 includes an analysis column 12, a detector 14 disposed on the downstream side of the column 12, a pump 18 for supplying an eluent (carrier liquid) 16 to the column 12, and an upstream side of the analysis column 12. An injection valve 20 that can inject a sample is provided. A viscosity detector 24 that is characteristic of the present invention is provided between the column 12 and the detector 14.

  As the detector 14, a differential refractometer can be used for general purposes. However, when the analyte has ultraviolet absorption, the ultraviolet absorption detector is more sensitive, More preferably used.

In the present embodiment, the viscosity detection device 24 is configured as shown in FIG.
That is, the viscosity detection device 24 includes four narrow tubes 26, 28, 30, and 32. The narrow tubes 26 and 28 are connected in series to the inflow path 34 and the outflow path 36, and the narrow tubes 30 and 32 are also connected in series. It is connected to the. A viscosity adjusting tube 38 made of a dilution tube or a delay tube is provided between the thin tube 30 and the thin tube 32. Here, as the dilution tube, a hollow cylindrical tube having a sufficiently large internal volume and in which the internal liquid is stirred by a stirrer is used, and as the delay tube, many cylindrical tubes (columns) filled with glass beads are used. Used. A bridge is formed between the midpoint 40 of the narrow tubes 26 and 28, and the midpoint 42 of the narrow tube 30 and the viscosity adjusting tube 38, and a differential pressure transducer 46 having a diaphragm 44 at the midpoint of the bridge. Is installed. The differential pressure transducer 46 substantially converts the pressure into an electric signal by detecting the amount of displacement of the diaphragm 44, and functions as a displacement detecting means of the present invention. The pressure loss of the viscosity adjusting tube 38 is selected to be negligible compared to the pressure loss of the narrow tube 32. The volume of the liquid portion in the viscosity adjusting tube 38 is selected so as to be larger than the volume of the eluent necessary for eluting the analysis object. When the pressure loss of the viscosity adjusting tube 38 cannot be ignored, the pressure loss of the viscosity adjusting tube 38-the thin tube 32 and the pressure loss of the thin tube 28 are adjusted to be equal. By such a reference viscosity adjusting tube 38, the sample liquid flowing in through the thin tube 30 does not flow into the thin tube 32 during the detection period, and the reference viscosity fluid (usually eluent) flows in, or the sample liquid flows. It is fully diluted and adjusted to the same viscosity as the eluent.

  The viscosity detector 24 is configured as described above, and the outlet of the column 12 is connected to the inflow path 34 and the outflow path 36 is connected to the detector 14. When the eluent is allowed to flow through the liquid chromatograph, the pressure loss of the thin tubes 26 and 30 fluctuates equally until the polymer substance dissolved in the eluent reaches the midpoints 40 and 42, while the pressure loss of the thin tubes 28 and 32 changes. Since they are equal, there is no pressure difference between the midpoints 40, 42. However, when the eluent containing the polymer substance passes through the midpoints 40 and 42, the pressure loss of the capillary tube 28 changes in the section A due to the viscosity caused by the polymer substance contained in the liquid, whereas the polymer substance in the section B changes. Stays in the viscosity adjusting tube 38 and no pressure loss occurs until it reaches the narrow tube 32, so that a differential pressure is generated between the midpoints 40 and 42.

  Then, based on detection of the diaphragm displacement by the differential pressure transducer 46, the displacement suppression means 48 applies a suppression force to the diaphragm 44 so as to suppress the displacement, and based on the suppression force value, the viscosity calculating means 52 Output viscosity.

  Therefore, the differential pressure transducer does not need to measure the minute displacement of the diaphragm quantitatively, and each channel capacity does not change. Therefore, it is possible to measure the viscosity with high accuracy and prevent tailing.

  In the present invention, the differential pressure between the midpoints 40 and 42 is detected by a diaphragm type differential pressure transducer 46. As a method of detecting the displacement of the diaphragm, there are a capacitance type, a resistance type, a variable reluctance type, etc., but it is not limited to a specific method.

  Among diaphragm type differential pressure transducers, capacitive and resistive type differential pressure transducers are often filled with an inert liquid such as silicon oil in the pressure measurement chamber to elute the liquid chromatograph. The liquid does not directly touch the diaphragm, electrode, or resistor. On the other hand, in the variable reluctance type differential pressure transducer, the pressure measurement chamber can be filled with the eluent of the liquid chromatograph if the portion in contact with the liquid is made of a corrosion-resistant material.

  There is no particular limitation on the method by which the displacement suppressing means 48 gives a force for suppressing the deformation of the diaphragm, but it is necessary to precisely control a small force. When the diaphragm is made of a magnetic material, a magnetic force can be directly applied to the diaphragm. Regardless of the material of the diaphragm, a force is applied to the diaphragm via a lever or the like, or a pump connected to the midpoint 42 (or 40) of the capillary bridge is used to prevent a differential pressure from being generated. Alternatively, it is possible to adopt a method such as connecting the narrow tube 32 and the pressure regulating valve to change the pressure difference of the pressure regulating valve so as not to generate the differential pressure.

In particular, when a variable reluctance type differential pressure transducer is used, detection coils for detecting a change in reluctance are provided on both sides of the diaphragm. Therefore, without modifying a commercially available variable reluctance type differential pressure transducer, a direct current is superimposed on a coil for detecting a change in reluctance, and a magnetic attraction (displacement suppressing force) can be applied in a direction to suppress the displacement of the diaphragm. it can. That is, the displacement of the diaphragm can be suppressed by comparing a signal proportional to the change in reluctance of the variable reluctance type differential pressure transducer with a zero voltage or a reference voltage and flowing a direct current proportional to the differential voltage through the detection coil. At this time, the diaphragm is preferably made of a soft magnetic material having a small magnetic hysteresis.
Note that the value of the direct current flowing through the coil is obtained by inserting a small resistor in series with the coil and measuring the voltage across the resistor.

  Alternatively, a direct current may be passed through a coil or an electromagnet provided independently of a detection coil for detecting a change in reluctance to generate a magnetic field in the vicinity of the diaphragm.

  The magnetic attractive force depends on the material of the diaphragm, the number of turns of the coil, the current, the shape of the yoke, and the like. When a displacement suppression coil is provided that is independent of the detection coil that detects reluctance changes, the optimal number of coil turns can be selected according to the differential pressure measurement range. It is preferable that the resistance value of the coil is selected so that the amount of heat generated when the maximum current is applied is several watts or less.

  Here, since a direct current according to Ohm's law flows when a direct current voltage is applied to a coil having an electrical resistance, either a current amplifier or a voltage amplifier may be selected when a direct current is applied.

  When the differential pressure fluctuates only on one side (middle point 40 side) as in the case where all dissolved components in the eluent push up the viscosity, a direct current is applied only to one coil (middle point 42 side). As the pressure increases, a larger direct current may be passed. Further, when the differential pressure swings in both positive and negative directions, a coil for passing a direct current may be switched between when it swings in the positive direction and when it swings in the negative direction so that the displacement of the diaphragm is always suppressed.

In order to improve the linearity of the signal when the differential pressure is near zero, it is also preferable to set the reference voltage to a non-zero voltage so that a small suction force works even if the differential pressure is zero. Also, if the differential pressure fluctuates in both the positive and negative directions, the direction of the direct current is constant, even if the differential pressure takes the maximum value of positive and negative, so that the current flows only through one coil. It is also preferable to set the reference voltage to a large voltage. At this time, a differential pressure signal proportional to the differential pressure can be obtained by shifting the voltage that provides the direct current.
Hereinafter, more specific examples of the present invention will be described.

(Example 1)
FIG. 3 shows a viscosity detecting apparatus according to the first embodiment of the present invention. The parts corresponding to those in FIG.

  A characteristic of the viscosity detection device 124 shown in FIG. 6A is that a diaphragm 144 that is permanently magnetized as the displacement suppression means 148 and a suppression that increases the suppression force until the displacement is suppressed based on the output of the transducer 146. A force calculating circuit 50, a solenoid coil 154 including the entire differential pressure transducer 146, and a driving circuit 156 thereof. Then, based on the displacement signal output from the differential pressure transducer 146, the drive circuit 156 energizes the solenoid coil 154, and the viscosity calculating means 152 determines the viscosity from the magnitude of the voltage value or current value necessary for suppressing the displacement. Ask for. In addition, the amount of increase or decrease in viscosity can be detected by changing the direction in which the current flows.

  In this embodiment, the diaphragm 144 is permanently magnetized, but a permanent magnet may be separately attached to the diaphragm 144 so that an attractive force or a repulsive force acts on the diaphragm 144 in a magnetic field.

  In this embodiment, when the flow rate is 0.1 ml / min or 0.2 ml / min, the narrow tube has an inner diameter of 0.1 mm and a length of 450 mm, and the viscosity adjusting tube 138 has an inner diameter of 21 mm and a length of 220 mm. A column filled with glass beads having a diameter of 0.2 mm was used, but the present invention is not limited to this.

  Further, as in the modification shown in FIG. 3B, a displacement suppression force may be generated by providing coils or electromagnets 154a and 154b on the left and right sides of the diaphragm 144 and conducting current to one of them. In this case, the diaphragm 144 needs to be a magnetic material, but need not be permanently magnetized.

(Example 2)
FIG. 4 shows a viscosity detection apparatus according to Embodiment 2 of the present invention, and a portion corresponding to FIG.
A characteristic of the viscosity detection device 224 shown in the figure is that the displacement suppressing means 248 includes a trace liquid discharge pump 258 and its drive circuit 256, and the pressure at the midpoint 242 is adjusted by the pump 258. .

  That is, the pump 258 has a motor 260 and a syringe 262 driven by the motor 260, and the suppression force calculation circuit 250 gives an instruction to the drive circuit 256 based on the output of the differential pressure transducer 246 to drive the motor 260 and the syringe 262. To do. The discharge end of the syringe is connected to the middle point 242, and the pressure control of the middle point 242 portion is performed by the eluent 264 discharged or sucked from the syringe 262, and the displacement of the diaphragm is suppressed. Therefore, the instruction of the suppression force calculation circuit 250, that is, the rotation speed of the motor 260, the eluent discharge speed or the suction speed of the syringe 262 is proportional to the differential pressure between the midpoint 242 and the midpoint 240 generated when no suppression force is applied, The viscosity can be determined from this discharge speed or suction speed.

  The pump 258 is preferably a pump capable of discharging a small amount of liquid. Even an intermittent feed pump such as a syringe pump, the amount of liquid necessary for analyzing one sample with a liquid chromatograph in one stroke of the syringe can be obtained. It only needs to be able to flow.

(Example 3)
FIG. 5 shows a viscosity detecting apparatus according to a third embodiment of the present invention. The parts corresponding to those in FIG.
A characteristic feature of this embodiment is that a pressure regulating valve 366 disposed in the section B is provided as the displacement restraining means 348. In FIG.

  That is, the pressure regulating valve 366 in the present embodiment includes a valve body 366a and a solenoid coil 366b that can drive the valve body 366a in the vertical direction in the drawing, as shown in detail in FIG. Then, the inflow hole 366 c is connected to the narrow tube 332, and the outflow hole 366 d is connected to the outflow path 336. As a result, the pressing force of the valve body 366a can be controlled by the excitation state of the solenoid coil 366b, and the outlet pressure of the narrow tube 332, that is, the pressure at the midpoint 342 can be adjusted.

  Since the exciting force (exciting current value) of the solenoid coil 366b is proportional to the viscosity, the viscosity calculating means 352 can acquire the exciting current value from the suppression force calculating circuit and output the viscosity signal.

Example 4
7 and 8 show a viscosity detecting apparatus according to Example 4 of the present invention, and a portion corresponding to FIG.

  In the viscosity detector 424 according to the present embodiment, as shown in FIG. 7, a diaphragm 444 is formed of a soft magnetic material, and coils 468 and 470 with bobbins having opposite polarities are arranged on both surfaces thereof. As shown in FIG. 8, the transducer 446 includes an AC transformer 446a and coils 468 and 470 connected in series on the secondary winding side of the transformer 446a. Since the coils 468 and 470 have substantially the same characteristics but have opposite polarities, no voltage is generated when the diaphragm is just at the middle point, but depending on which coil the diaphragm 444 forming the magnetic path approaches. The substantial inductance of the coils 468 and 470 changes, and an AC voltage is generated between the connection point of the coils 468 and 470 and the midpoint of the secondary winding of the transformer 446b. The generated AC voltage is amplified by the differential amplifier circuit 446b, and this differential signal is output as a reactance change having no ripple by the phase detection circuit 446c. Therefore, the change in the reactance signal indicates the displacement of the diaphragm 444.

  In this embodiment, the displacement suppression means 448 compares this reactance fluctuation signal with a zero voltage (differential amplifier circuit 448a), and superimposes the amplified output on the coil 468 via the choke coil 448b in the state of direct current, Feedback control is performed so that the reactance fluctuation signal becomes zero.

  According to the viscosity detector 424 according to the present embodiment, the output of the differential amplifier circuit 448a is proportional to the output required to suppress the displacement of the diaphragm 444, and this is output as a viscosity signal.

(Example 5)
FIG. 9 shows a viscosity detecting apparatus according to a fifth embodiment of the present invention. The parts corresponding to those in FIG.

  The viscosity detection device 524 according to the present embodiment compares the reactance signal with a large reference voltage in the comparison circuit 548a of the displacement suppression means 548, and constantly applies a suppression current to the coil 568. The phase signal of the phase detector, the positive / negative of the amplifier, and the coil through which the direct current flows are appropriately selected so that the direct current gives a magnetic attractive force in a direction that suppresses the displacement of the diaphragm.

  The magnitude of the reference voltage is selected so that the current value does not cross zero over the entire range of differential pressure. Since the current value is not zero even when the differential pressure is zero, an offset signal is shifted to obtain an output signal proportional to the differential pressure (difference circuit 548c).

  In this embodiment, the diaphragm is always held at a position displaced by a certain amount. Even when the differential pressure changes from positive to negative or vice versa, the diaphragm has the advantage that the magnetic attractive force in the same direction is always applied to maintain the linearity and is stable without causing hunting.

(Example 6)
FIG. 10 shows a viscosity detecting apparatus according to Example 6 of the present invention, and a portion corresponding to FIG.

  In the viscosity detection device 624 according to the present embodiment, the displacement suppression unit 648 supplies a direct current to the first choke coil 648b when the output of the comparison circuit 648a comparing the reactance signal and the zero voltage is positive. And a second diode 648e that supplies a direct current to the second choke coil 648d when the output of the comparison circuit 648a is negative. The first choke coil 648b can supply a direct current to the coil 668. The second choke coil 648d is connected to the coil 670 so as to supply a direct current.

  As described above, according to the viscosity detection device 624 according to the present embodiment, not only when the sample-containing liquid has a high viscosity with respect to the eluent, but also when the viscosity becomes low, the displacement is appropriately suppressed, It is possible to output a viscosity signal.

(Example 7)
FIG. 11 shows a viscosity detecting apparatus according to a seventh embodiment of the present invention. The portion corresponding to FIG.

  In the viscosity detection device 724 according to the present embodiment, the displacement suppression unit 748 includes a pair of differential amplifier circuits 748a and 748b that output a direct current depending on whether the reactance signal is positive or negative, and a diode 748c. 748d and choke coils 748e, 748f. In this case, the voltage values are adjusted using the respective reference voltages close to zero voltage so that the output currents of the respective differential amplifier circuits 748a and 748b are smoothly connected without causing an overlapping operation region, or the difference between the output currents is different. It is preferable to adjust the offset of the dynamic amplifier circuit. Alternatively, it can be adjusted so that the output current overlaps and the sum of both companies becomes a constant value.

Note that the phase signal of the phase detector and the sign of the amplifier are appropriately selected so that the direct current generates a magnetic attractive force in a direction that suppresses the displacement of the diaphragm.
In the present embodiment, a difference circuit 748g is provided, and a viscosity signal is output based on a difference between a positive signal and a negative signal.

(Example 8)
FIGS. 12 and 13 show a viscosity detecting apparatus according to an eighth embodiment of the present invention. The parts corresponding to those in FIGS.
In this embodiment, the suppression current by the displacement suppression means 848 is not supplied to the coil 868 but is supplied to the coil 848b independent of the detection coil 868.

  Note that the coil 848b may be provided on one side of the diaphragm or may be provided on both sides. When the coil 848b is installed only on one side, it is also preferable to install a dummy coil 848d on the other side in order to balance the reactance characteristics. In addition, when installed on both sides, the current supply coil for passing a direct current may be switched between the case where the differential pressure is positive and the case where the pressure difference is negative as in the sixth to seventh embodiments.

It is a conceptual diagram of the liquid chromatograph to which the viscosity detection apparatus concerning this invention was applied. It is a conceptual diagram of the viscosity detection apparatus concerning this invention. It is a block diagram of the viscosity detection apparatus concerning Example 1 of this invention. It is a block diagram of the viscosity detection apparatus concerning Example 2 of this invention. It is a block diagram of the viscosity detection apparatus concerning Example 3 of this invention. It is explanatory drawing of the pressure control valve used for the viscosity detection apparatus concerning Example 3 of this invention. It is a block diagram of the differential pressure transducer (displacement detection means) used for the viscosity detection apparatus concerning Example 4 of this invention. It is a block diagram of the viscosity detection apparatus concerning Example 4 of this invention. It is a block diagram of the viscosity detection apparatus concerning Example 5 of this invention. It is a block diagram of the viscosity detection apparatus concerning Example 6 of this invention. It is a block diagram of the viscosity detection apparatus concerning Example 7 of this invention. It is a block diagram of the differential pressure transducer (displacement detection means) used for the viscosity detection apparatus concerning Example 8 of this invention. It is a block diagram of the viscosity detection apparatus concerning Example 8 of this invention.

Explanation of symbols

10 Liquid Chromatograph 12 Analysis Column 14 Detector 24, 124, 224, 324, 424, 524, 624, 724, 824
Viscosity detectors 26-32, 126-132, 226-232, 326-332
Capillary 44,144,244,344,444,544,644,744,844
Diaphragm 46,146,246,346,446,546,646,746,846
Differential pressure transducer 48, 148, 248, 348, 448, 548, 648, 748, 848
Displacement suppression means

Claims (7)

A fluid inflow path and a fluid outflow path, and four narrow tubes having substantially the same flow path resistance, and the two thin tubes are connected in series, and the series pair of the narrow tubes is connected to the inflow channel-outflow In the equilibrium bridge type viscosity detector connected in parallel to the road, and the midpoint of each series pair is connected pressure-wise through a diaphragm,
A standard that is installed between the downstream tube and the midpoint of either one of the series-paired tubes, and the fluid that flows in through the upstream tube stays or dilutes during the viscosity measurement period, and introduces the reference viscosity fluid into the downstream tube Viscosity adjusting means;
A displacement detecting means for detecting displacement relative to a reference position of the diaphragm;
A displacement restraining means for applying a displacement restraining force to the diaphragm so as to reduce the displacement of the diaphragm;
Viscosity calculation means for calculating the viscosity of the fluid from the displacement suppression force value by the displacement suppression means;
Equilibrium bridge type viscosity detection device. 2. The apparatus according to claim 1, wherein the diaphragm includes a magnetic body, and the displacement suppression means includes a solenoid coil disposed in proximity to the diaphragm, and excites the solenoid coil based on a detection result by the displacement detection means, An equilibrium bridge type viscosity detecting apparatus, wherein a displacement suppression force is applied. 2. The apparatus according to claim 1, wherein the displacement suppression means includes a fluid pump, and when the pressure at the midpoint on the side where the reference viscosity adjusting means is installed becomes lower than the pressure at the other midpoint, liquid is supplied to the midpoint. An equilibrium bridge type viscosity detecting device characterized by injecting or sucking a liquid from the middle point when the pressure at the middle point becomes higher than the pressure at the other middle point and applying a displacement suppressing force to the diaphragm . 2. The apparatus according to claim 1, wherein the displacement suppressing means includes at least a pressure regulating valve disposed on the downstream side of the narrow tube series pair, and applies a displacement inhibiting force to the diaphragm by adjusting the opening of the pressure regulating valve. An equilibrium bridge type viscosity detector characterized by the above. The apparatus of claim 1.
The diaphragm contains a magnetic material,
The displacement detection means includes detection coils arranged on both sides of the diaphragm, and magnetically detects which detection coil is close to the diaphragm,
The displacement suppression means applies a displacement suppression current in a superimposed manner to any one of the detection coils in accordance with the displacement of the diaphragm. 6. The balanced bridge type viscosity detecting apparatus according to claim 5, wherein the displacement suppressing means supplies a direct current to the one of the detection coils via a choke coil in accordance with the displacement of the diaphragm. 7. The equilibrium bridge type viscosity detecting device according to claim 1, wherein the thin tube has an inner diameter of 0.2 mm or less.

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