JP5361602B2 - Vibration density measuring method and vibration density meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration-type density measuring method removing influence on an oscillation cycle from static electricity charged on a liquid sample to be measured and a vibration-type densitometer discharging static electricity charged on a liquid sample to be measured. <P>SOLUTION: A liquid sample is introduced into a glass cell 1 through a sample introducing tube 8a, a metal joint 7a and cell introducing piping 6a, and an earth wire is contacted to the metal joint 7a or 7b, thereby static electricity charged on a liquid sample is discharged. Then the glass cell 1 is vibrated by making electromagnetic force interact on a permanent magnet 2 and density of the liquid sample is calculated from an oscillation cycle measured for the glass cell 1. In this way, the static electricity charged on the liquid sample is discharged, therefore, a correct density value is measured without changing the oscillation cycle of the glass cell due to static electricity. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a vibration type density meter, and more particularly to a vibration type density meter that removes the influence of static electricity charged on a liquid sample to be measured.

  The vibration type density meter is a device that vibrates the measurement cell containing the sample to be measured, and calculates and outputs the density of the sample to be measured from the measured natural vibration period. For example, the density of various fluids such as concentration management of soft drinks It is used for measurement.

  This vibration type density meter has, for example, a glass U-shaped measurement cell, a permanent magnet is fixed to the tip of the glass cell, and a drive coil and a detection unit are built in a position facing the permanent magnet. Is arranged. Then, when measuring the density of the sample to be measured, the sample to be measured is introduced into the glass cell, and the glass cell is vibrated by applying a driving current to the driving coil of the measuring head and applying an electromagnetic force to the permanent magnet. The density of the sample to be measured is obtained from the natural vibration period of the glass cell detected by (see, for example, Patent Document 1).

Hereinafter, a method for calculating the density of the sample to be measured from the natural vibration period will be described.
If the natural vibration period of the glass cell is T and the density of the sample to be measured is ρ, ρ is
ρ = PT ² / 4π ² VM / V (1)
Can be obtained. Where P is the vibration constant of the vibration system, V is the volume of the fluid to be measured (the volume of the glass cell), and M is the mass of the glass cell and the permanent magnet.
Since each P, V, and M is a constant determined by the structure of the sensor unit, when P / 4π ² V = K ₁ and M / V = K ₂ ,
ρ = K ₁ T ² −K ₂ (2)
It can be expressed as

Here, T _water and T _AIR are the natural vibration periods of two kinds of substances having known densities, for example, pure water (ρ _WATER ) and air (ρ _AIR ) measured with a glass cell,
ρ _WATER = K ₁ T _WATER ² -K ₂ (3)
ρ _AIR = K ₁ T _AIR ² −K ₂ (4)
From the above equations (3) and (4), the constants K ₁ and K ₂ are
K ₁ = (ρ _AIR −ρ _WATER ) / (T _AIR ²⁻ T _WATER ² ) (5)
K ₂ = T _AIR ² · (ρ _AIR −ρ _WATER ) / (T _AIR ² −T _WATER ² ) −ρ _AIR (6)
It becomes.

From the above formulas (5) and (6), formula (2) is
ρ = ρ _AIR + (ρ _AIR −ρ _WATER ) * (T ² −T _AIR ² ) / (T _AIR ² −T _WATER ² ) (7)
Since the density ρ _WATER and ρ _AIR at a set temperature of pure water and air are known, the measurement is performed from the vibration periods T _AIR and T _{WATER in} which pure water and air are measured and the vibration period T in which the sample to be measured is measured. The density ρ of the sample can be calculated.

Japanese Patent Laid-Open No. 6-58862

  A cell introduction pipe is connected to one open end of the glass cell of the vibration type densitometer in which measurement is performed as described above, and a cell outlet pipe is connected to the other open end. The cell introduction pipe and the cell outlet pipe are connected to a sample introduction tube for introducing a measurement sample through a joint and a sample discharge tube for discharging a measurement sample which has been measured, respectively, and when measuring the density of the measurement sample, A sample to be measured is introduced into the glass cell via the sample introduction tube.

  As described above, the cell introduction pipe and the cell exit pipe of the glass cell are connected to the sample introduction tube and the sample discharge tube through the joint so that the sample can be easily replaced when the sample is changed. The cell outlet pipe, sample introduction tube, sample discharge tube, and joint must have corrosion resistance to the sample to be measured. Generally, fluororesins such as Teflon (registered trademark) tubes and Teflon joints are used. ing.

  However, when changing the liquid sample, it is necessary to wipe the cell introduction pipe and cell outlet pipe with paper etc. to remove the adhering liquid. Fluorine resin is easily charged by such contact friction, and the charge is measured. There is also a problem that the target liquid sample is affected, the vibration period changes due to the electrostatic field, and correct density measurement cannot be performed.

  The present invention was devised to solve the above-described problem, and a vibration-type density measuring method and a liquid to be measured capable of removing the influence of the static electricity charged on the liquid sample to be measured on the vibration period. An object of the present invention is to provide a vibration type density meter capable of discharging static electricity charged on a sample.

  According to a first aspect of the present invention, there is provided a vibration type density measuring method for measuring a density of a sample to be measured from a vibration period of a glass cell containing the sample to be measured. After the discharge, the density of the sample to be measured is measured.

  According to a second aspect of the present invention, there is provided a vibratory density meter that measures the density of a sample to be measured from the vibration period of a glass cell that contains the sample to be measured. It is characterized by having a discharge mechanism for discharging the gas.

Furthermore, the vibratory density meter of the invention according to claim 3 is the vibratory density meter of the invention of claim 2, wherein the discharge mechanism is connected to the glass cell pipe and the sample tube to be measured, and / or It is composed of a metal joint that connects the discharge tube,
A vibration type density meter according to a fourth aspect of the present invention is the vibration type density meter according to the second aspect of the present invention, wherein the discharge mechanism is constituted by a ground electrode attached to the glass cell.

The vibratory density meter of the invention according to claim 5 is characterized in that, in the vibratory density meter of the invention of claim 2, the discharge mechanism is constituted by a plating coating applied to the glass cell,
The vibratory density meter of the invention according to claim 6 is the vibratory density meter of the invention of claim 2, wherein the discharge mechanism introduces and discharges the sample to be measured into the glass cell, and / or The sample discharge tube is a metal tube.

  Furthermore, the vibration type density meter of the invention according to claim 7 is the vibration type density meter of the invention according to claim 2, wherein the discharge mechanism introduces and discharges the sample to be measured to the glass cell, and / Or the sample discharge tube is a resin tube made of a conductive material.

  According to the vibration type density measuring method of the invention according to claim 1, since the density of the liquid sample is measured after discharging the static electricity charged in the liquid sample to be measured, the liquid sample to be measured is in a charged state. However, since the static electricity is discharged, the correct density value can be measured without changing the vibration period of the glass cell due to the static electricity.

  In addition, according to the vibratory density meter of the inventions according to claims 2 to 7, since the discharge mechanism for discharging the static electricity charged in the liquid sample to be measured is provided, static electricity is charged in the liquid sample to be measured. Similarly, the correct density value can be measured without changing the vibration period of the glass cell due to static electricity.

It is a figure which shows the structure of the sensor part of the vibration type density meter of this invention. It is a conceptual diagram of the vibration type density meter which attached the sensor part of FIG. It is a figure which shows the time change of the vibration period at the time of discharging static electricity. It is a figure which shows the structure of the sensor part provided with the discharge mechanism of this invention. It is a figure which shows the structure of the other Example of the sensor part provided with the discharge mechanism of this invention. It is a figure which shows the structure of the other Example of the sensor part provided with the discharge mechanism of this invention. It is a figure which shows the structure of the other Example of the sensor part provided with the discharge mechanism of this invention. It is a figure which shows the structure of the other Example of the sensor part provided with the discharge mechanism of this invention.

FIG. 1 is a diagram showing the structure of a sensor unit of a vibration type density meter according to the present invention. This sensor unit includes a glass cell 1, permanent magnets 2, holders 3a and 3b, a temperature sensor 4, a glass outer cylinder 5, It is composed of a cell introduction pipe 6a and a cell outlet pipe 6b.
The glass cell 1 is a thin U-shaped tube made of glass having a wall thickness of about 0.2 mm, and a thin plate 2 of a permanent magnet is fixed to the tip of the tube with an adhesive. Further, the base end portion of the glass cell 1 is fixed to the holders 3 a and 3 b, and the holders 3 a and 3 b are fixed to the outer cylinder 5. The temperature sensor 4 has a thermistor inserted in the glass tube, and measures the temperature of the sample.

  In addition, the cell introduction pipe 6a and the cell outlet pipe 6b for introducing and discharging the sample to and from the glass cell 1 are connected to the sample introduction tube 8a and the metal pipe 7a and 7b through the metal joints 7a and 7b so that the sample can be easily replaced when the sample is changed. Connected to the sample discharge tube 8b. A Teflon tube is used for the cell introduction pipe 6a, the cell outlet pipe 6b, the sample introduction tube 8a, and the sample discharge tube 8b, and a metal such as SUS is used for the metal joints 7a and 7b.

On the other hand, FIG. 2 is a conceptual diagram of the vibration type density meter to which the sensor unit of FIG. 1 is attached. The sensor unit is housed in the heat insulating material 11 and has a copper block 12 having a Peltier element (not shown). Is controlled to keep the temperature of the sample to be measured in the sensor unit, that is, the glass cell 1, at the set temperature. A measurement head 15 including a drive coil 13 and a vibration detection sensor 14 for detecting vibration by light is disposed at a position facing the permanent magnet 2 fixed to the tip of the glass cell 1.
As shown in the figure, a thermistor 16 is disposed in the glass tube of the temperature sensor 4 and measures the temperature near the tip of the glass cell 1.

  The control device 17 includes a control unit 21, a drive unit 22, a detection unit 23, a display unit 24, and a storage unit 25. The temperature detection output of the thermistor 16 is input to the control unit 21, and the temperature of the thermistor 16 is measured and set. The Peltier element of the copper block 12 is controlled so that the temperature is reached. The drive unit 22 supplies a drive current to the drive coil 13 of the measurement head 15, and the detection unit 23 detects the output of the vibration detection sensor 14 of the measurement head 15 to detect the vibration cycle of the glass cell 1. Furthermore, the control unit 21 displays the measurement setting screen and the density measurement value on the display unit 24, and stores the measurement condition set by the user, the detected vibration cycle, and the like in the storage unit 25.

Next, the effect | action at the time of the density measurement of a liquid sample is demonstrated.
In the measurement, first, a liquid sample is introduced into the glass cell 1 through the sample introduction tube 8a, the metal joint 7a, and the cell introduction pipe 6a, and a ground wire is brought into contact with the metal joint 7a or 7b to charge the liquid sample. Discharge static electricity. Thereafter, a driving current is input to the driving coil 13 of the measuring head 15 from the driving unit 22 of the control device 17, and an electromagnetic force is applied to the permanent magnet 2 to cause the glass cell 1 to start vibrating.

  The vibration detection sensor 14 of the measurement head 15 detects the vibration at this time, inputs a detection signal to the detection unit 23, and continuously inputs a drive signal synchronized with this vibration cycle to the drive coil 13 of the measurement head 15. The natural vibration period is obtained by vibrating the glass cell 1 at a constant period, and the density of the liquid sample is calculated from the measured vibration period.

  FIG. 3 is a plot of changes over time in the vibration cycle when static electricity is discharged during measurement of the vibration cycle. As shown in FIG. 3, the static electricity is discharged when 0.1 hour has elapsed after the start of measurement. By doing so, it can be understood that the correct density value can be measured without causing a change in the vibration period that has been fluctuated by static electricity until then.

In the above embodiment, the static electricity charged in the liquid sample was discharged by bringing the ground wire into contact with the metal joint 7a or 7b during density measurement. However, as shown in FIG. 4, the metal joint 7a, By grounding one or both of 7b, even if the liquid sample to be measured is charged with static electricity, it can be discharged, so that the vibration cycle of the glass cell 1 does not change due to static electricity and the correct density is obtained. The value can be measured.
In the above embodiment, the static electricity of the liquid sample was discharged by grounding the metal joint during density measurement. However, the liquid sample was grounded by touching the grounded metal to the liquid sample itself or by touching the grounded metal to the liquid sample itself. It is also possible to discharge static electricity.

  In the above embodiment, the joint is made of metal so that static electricity charged in the liquid sample is discharged. However, the discharge mechanism can be configured by other configurations. An example will be described.

FIG. 5 is a diagram showing an embodiment in which a ground electrode is attached to a glass cell as a discharge mechanism. As shown in the figure, a ground electrode 31 is inserted into the glass cell 1 through a holder 3a. As the ground electrode 31, it is desirable to use platinum so that the glass cell 1 does not crack.
Thus, similarly to the above, even if static electricity is charged in the liquid sample to be measured, it can be discharged, so that the correct density value can be measured without changing the vibration period of the glass cell due to static electricity. .

Further, FIG. 6 shows a case where a glass cell is plated as a discharge mechanism. As shown in the figure, the outer periphery of the end of the outer cylinder 5 and the inner peripheral surface of the end of the glass cell 1 are plated. A coating 32 is applied and the plated portion is grounded.
Thus, similarly to the above, even if static electricity is charged in the liquid sample to be measured, it can be discharged, so that the correct density value can be measured without changing the vibration period of the glass cell due to static electricity. .

Furthermore, FIG. 7 shows a sample introduction tube for introducing and discharging a sample to be measured into a glass cell and a sample discharge tube as a metal pipe as a discharge mechanism. As shown in FIG. The tube 8b is constituted by a metal pipe 33, and one or both of the metal pipes 33 are grounded.
Thus, similarly to the above, even if static electricity is charged in the liquid sample to be measured, it can be discharged, so that the correct density value can be measured without changing the vibration period of the glass cell due to static electricity. .

FIG. 8 shows a discharge mechanism in which a sample introduction tube that introduces and discharges a sample to be measured into a glass cell, and the sample discharge tube is a resin tube made of a conductive material. As shown in FIG. The sample discharge tube 8b is composed of a conductive resin tube 34, and one or both of the conductive resin tubes 34 are grounded.
Thus, similarly to the above, even if static electricity is charged in the liquid sample to be measured, it can be discharged, so that the correct density value can be measured without changing the vibration period of the glass cell due to static electricity. .

  1 and 4, both of the two joints on the sample introduction side and the sample discharge side are metal joints, but only one of the sample introduction side or the sample discharge side may be a metal joint, 7 and 8, both the sample introduction tube and the sample discharge tube are metal pipes or conductive resin tubes, but only one of the sample introduction tube or the sample discharge tube is a metal pipe or conductive pipe. A good resin tube may be used.

  In the above embodiment, the metal joint, the ground electrode, the plating coating, the metal pipe, or the conductive tube is grounded. However, it is not always necessary to ground, and the effect of reducing static electricity can be obtained without grounding. it can.

  Furthermore, in the above embodiment, a vibration type density meter having a measurement head having a drive coil and a sensor for detecting vibration by light, which is disposed opposite to a permanent magnet attached to the tip of the measurement cell, will be described as an example. However, the vibration-type density measuring method and the vibration-type density meter of the present invention can be applied to other vibration-type density meters such as a vibration-type density meter that detects vibration with a detection coil.

DESCRIPTION OF SYMBOLS 1 Glass cell 2 Permanent magnet 3a, 3b Holder 4 Temperature sensor 5 Outer cylinder 6a Cell introduction piping 6b Cell exit piping 7a, 7b Metal joint 8a Sample introduction tube 8b Sample discharge tube 11 Heat insulating material 12 Copper block 13 Drive coil 14 Vibration detection sensor DESCRIPTION OF SYMBOLS 15 Measurement head 16 Thermistor 17 Control apparatus 21 Control part 22 Drive part 23 Detection part 24 Display part 25 Memory | storage part

Claims (7)

In the vibration type density measuring method for measuring the density of the sample to be measured from the vibration period of the glass cell containing the sample to be measured,
A vibration type density measuring method comprising: measuring a density of a sample to be measured after discharging static electricity charged in a liquid sample to be measured. In the vibration type density meter that measures the density of the sample to be measured from the vibration period of the glass cell containing the sample to be measured,
A vibration type density meter comprising a discharge mechanism for discharging static electricity charged in a liquid sample to be measured.   3. The vibratory density meter according to claim 2, wherein the discharge mechanism is constituted by a metal joint that connects the pipe of the glass cell and the introduction tube and / or the discharge tube of the sample to be measured. Vibrating density meter.   3. The vibration type density meter according to claim 2, wherein the discharge mechanism is constituted by a ground electrode attached to the glass cell.   3. The vibration type density meter according to claim 2, wherein the discharge mechanism is constituted by a plating coating applied to the glass cell.   3. The vibration type density meter according to claim 2, wherein the discharge mechanism is an introduction tube for introducing and discharging a sample to be measured into the glass cell, and / or a sample discharge tube is a metal tube. Expression density meter.   3. The vibration type density meter according to claim 2, wherein as the discharge mechanism, the sample introduction tube for introducing and discharging the sample to be measured into the glass cell and / or the sample discharge tube is a resin tube made of a conductive material. This is a vibration type density meter.

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