CN116075707A - Vibrating densitometer and method for determining bubble mixing in vibrating densitometer - Google Patents
Vibrating densitometer and method for determining bubble mixing in vibrating densitometer Download PDFInfo
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- CN116075707A CN116075707A CN202180056422.9A CN202180056422A CN116075707A CN 116075707 A CN116075707 A CN 116075707A CN 202180056422 A CN202180056422 A CN 202180056422A CN 116075707 A CN116075707 A CN 116075707A
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
- G01N11/10—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material
- G01N11/16—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material by measuring damping effect upon oscillatory body
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- G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
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Abstract
Provided is a vibrating densitometer which can detect bubbles mixed into a sample container without repeating the introduction of a sample to be measured into the sample container. A vibrating densitometer (1) for measuring the density of a sample to be measured contained in a sample container (10) is provided with: an excitation unit (20) for exciting the sample container (10) to vibrate; a measurement unit (30) that measures the vibration cycle of the excited sample container (10); a drive control unit (80) that drives the excitation unit (20) with a first drive force and a second drive force that is smaller than the first drive force; and a determination unit (90) that determines the presence or absence of air bubbles in the sample container (10) based on a difference between a first vibration period of the sample container (10) excited by the first driving force and a second vibration period of the sample container (10) excited by the second driving force.
Description
Technical Field
The present invention relates to a vibrating densitometer for measuring the density of a sample to be measured contained in a sample container (sample cell) and a method for determining the mixing of bubbles in the vibrating densitometer.
Background
A vibrating densitometer is a device that holds a liquid sample to be measured in a sample container having one end fixed, vibrates the sample, and calculates the density of the sample to be measured from the vibration period (for example, refer to patent document 1).
Assuming that the vibration period of the sample container for storing the sample to be measured is T, the calculation in the vibration densitometer obtains the density ρ of the sample to be measured by the following formula (1) sample ：
ρ sample ＝K 1 ×T 2 +K 2 …(1)。
Here, correction parameter K 1 、K 2 The constant is determined based on the density and the vibration period when 2 kinds of reference substances having known densities are respectively contained in the sample container at the reference temperature and vibrated. For this reason, if the vibration cycle of the sample container containing the sample to be measured is measured at a temperature different from the reference temperature, an error occurs in the calculated value of the density.
The vibrating densitometer of patent document 1 can suppress errors in the calculation of the density of the sample to be measured by controlling the temperature of the sample container so as to maintain the temperature at the reference temperature by using a temperature control means such as a copper block having a heat insulator or a peltier element.
Prior art literature
Patent literature
Patent document 1: JP-A2011-38810
Disclosure of Invention
Problems to be solved by the invention
In the calculation of the density in the vibrating densitometer, not only the temperature is measured, but also the mixing of bubbles into the sample container becomes a factor of error. For this reason, in the past, when the calculated density is not changed any more by repeating the introduction of the sample to be measured into the sample container and the measurement of the vibration cycle, it was confirmed that the air bubbles were discharged from the sample container.
However, if the introduction of the sample to be measured is repeated, the temperature of the sample container changes every time the sample is repeated. In the vibrating densitometer of patent document 1, since it is necessary to wait until the sample container reaches the reference temperature from the introduction of the sample to be measured, if the introduction of the sample to be measured is repeated for confirming the discharge of the air bubbles from the sample container, there is a problem that the measurement time becomes long.
The present invention has been made in view of the above-described problems, and an object thereof is to provide a vibrating densitometer capable of detecting bubbles mixed into a sample container without repeating introduction of a sample to be measured into the sample container, and a bubble mixing determination method in the vibrating densitometer.
Means for solving the problems
In order to solve the above-described problems, a vibrating densitometer according to the present invention is a vibrating densitometer for measuring a density of a sample to be measured stored in a sample container, comprising: an excitation unit that excites and vibrates the sample container; a measurement unit that measures the excited vibration cycle of the sample container; a drive control unit that drives the excitation unit with a first driving force and a second driving force smaller than the first driving force; and a determination unit that determines the presence or absence of bubbles in the sample container based on a difference between a first vibration period of the sample container excited by the first driving force and a second vibration period of the sample container excited by the second driving force.
The vibrating densitometer according to the present structure includes: an excitation unit for exciting and vibrating the sample container; a measurement unit that measures the vibration cycle of the excited sample container; a drive control unit that drives the excitation unit with a first driving force and a second driving force smaller than the first driving force; and a determination unit that determines the presence or absence of air bubbles in the sample container based on a difference between a first vibration period of the sample container excited by the first driving force and a second vibration period of the sample container excited by the second driving force, whereby it is unnecessary to repeat the introduction of the sample to be measured into the sample container and the measurement of the vibration period in order to confirm the discharge of the air bubbles, and it is possible to determine the presence or absence of the air bubbles while maintaining a state in which the sample to be measured is accommodated in the sample container. Therefore, in the vibrating densitometer of the present configuration, the presence or absence of air bubbles can be determined in a short time without generating a plurality of temperature changes in the sample container accompanied by repetition of introduction of the sample to be measured. As a result, the time from introduction of the sample to be measured to measurement of the density can be shortened while preventing occurrence of errors due to mixing of bubbles.
In the vibrating densitometer according to the present invention, the second driving force is preferably a driving force 1/5 to 1/2 times the first driving force.
According to the vibrating densitometer of the present structure, the second driving force is 1/5 to 1/2 times the first driving force, and the difference between the first vibration period and the second vibration period becomes remarkable, so that the presence or absence of air bubbles in the sample container can be accurately determined.
In the vibrating densitometer according to the present invention, preferably, the first vibration cycle is a vibration cycle measured by the measuring means immediately before the driving force of the exciting means is changed from the first driving force to the second driving force, and the second vibration cycle is a vibration cycle measured by the measuring means at an arbitrary time point between 8 and 10 seconds from the time when the driving force of the exciting means is changed to the second driving force.
According to the vibrating densitometer of the present configuration, the first vibration cycle is a vibration cycle measured by the measuring means immediately before the driving force of the exciting means is changed from the first driving force to the second driving force, and the second vibration cycle is a vibration cycle measured by the measuring means at any time point between 8 and 10 seconds from the time when the driving force of the exciting means is changed to the second driving force, whereby the difference between the first vibration cycle and the second vibration cycle becomes more remarkable, and the determination of the presence or absence of air bubbles in the sample container becomes more accurate.
In the vibrating densitometer according to the present invention, it is preferable that the difference between the first vibration period and the second vibration period by the determination unit is 1.5x10 -2 If μ seconds or more, it is determined that the bubbles are present.
According to the present knotThe difference between the first vibration period and the second vibration period in the determination unit of the configured vibrating densitometer is 1.5X10 -2 In the case of μsec or more, the presence or absence of bubbles in the sample container can be reliably determined.
In the vibrating densitometer according to the present invention, the viscosity of the sample to be measured is preferably 200mpa·s or less.
The higher the viscosity of the sample to be measured, the smaller the difference between the first vibration period and the second vibration period tends to be. According to the vibrating densitometer of the present structure, the viscosity of the sample to be measured is 200mpa·s or less, whereby the influence of the viscosity of the sample to be measured can be suppressed, and the presence or absence of bubbles in the sample container can be determined.
In the vibrating densitometer according to the present invention, preferably, the sample container is a U-tube, and the determination means determines the presence or absence of the air bubble in a section of 1/2 or less from a distal end to a fixed end of the U-tube.
In the calculation of the density in the vibrating densitometer, if a bubble exists in a region of 1/2 or less from the tip to the fixed end of the U-shaped tube, an error becomes large. According to the vibrating densitometer of the present configuration, the sample container is a U-tube, and the determination means determines the presence or absence of air bubbles in the section of 1/2 or less from the tip to the fixed end of the U-tube, whereby the density of the sample to be measured can be calculated with practically sufficient accuracy.
In order to solve the above problems, a feature of the present invention is a bubble mixing determination method for determining mixing of bubbles into a sample container in a vibrating densitometer for measuring a density of a sample to be measured stored in the sample container, the method comprising: a first excitation step of exciting the sample container to vibrate with a first driving force; a first measurement step of measuring a first vibration cycle of the sample container excited by the first driving force; a second excitation step of exciting the sample container to vibrate with a second driving force smaller than the first driving force; a second measurement step of measuring a second vibration cycle of the sample container excited by the second driving force; and a determination step of determining the presence or absence of bubbles in the sample container based on a difference between the first vibration period and the second vibration period.
The bubble mixing determination method according to the present configuration includes: a first excitation step of exciting the sample container to vibrate by a first driving force; a first measurement step of measuring a first vibration cycle of the sample container excited by a first driving force; a second excitation step of exciting the sample container to vibrate with a second driving force smaller than the first driving force; a second measurement step of measuring a second vibration cycle of the sample container excited by a second driving force; and a determination step of determining the presence or absence of air bubbles in the sample container based on the difference between the first vibration period and the second vibration period, whereby it is not necessary to repeat the introduction of the sample to be measured into the sample container and the measurement of the vibration period in order to confirm the discharge of the air bubbles, and the presence or absence of air bubbles can be determined while maintaining the state in which the sample to be measured is accommodated in the sample container. Therefore, in the bubble incorporation determination method of the present configuration, the presence or absence of bubbles can be determined in a short time without generating a plurality of temperature changes in the sample container accompanied by repetition of introduction of the sample to be measured. As a result, the time from introduction of the sample to be measured to measurement of the density can be shortened while preventing occurrence of errors due to mixing of bubbles.
Drawings
Fig. 1 is a structural diagram of a vibrating densitometer according to the present invention.
Fig. 2 is a graph showing the measurement result of the vibration cycle in the measurement unit.
Fig. 3 is a diagram schematically showing the position of the bubble in the sample container.
Fig. 4 is a graph showing the measurement result of the vibration cycle in the sample container in which no air bubbles are mixed in a state where there is a change in temperature after the introduction of the sample to be measured.
Detailed Description
Hereinafter, the vibrating densitometer and the bubble detection method in the vibrating densitometer according to the present invention will be described. The present invention is not limited to the configurations described in the embodiments and drawings described below.
< vibrating densitometer >
Fig. 1 is a structural diagram of a vibrating densitometer 1 according to the present invention. The vibrating densitometer 1 includes: a measuring unit 100 for vibrating a sample container 10 containing a sample to be measured of a liquid to measure a vibration cycle thereof; and an arithmetic unit 200 for calculating the density of the sample to be measured from the measured vibration period.
< measurement part >
The measurement unit 100 includes a sample container 10, an excitation unit 20, and a measurement unit 30, which are accommodated in a case 52 containing a heat insulator or the like.
The sample container 10 is a U-shaped glass tube. A thin plate-like permanent magnet 11 is fixed to the tip (curved tube portion of the glass tube) 10a of the sample container 10 by an adhesive or the like. The fixed ends (both tube openings of the glass tube) 10b of the sample container 10 are fixed by a bracket 51, and the bracket 51 is fixed to a housing 52. One nozzle of the sample container 10 is connected to a sampling tube into which a sample to be measured is introduced via a holder 51, and the other nozzle is connected to a drain tube for discharging the sample to be measured, the measurement of which has been completed, via the holder 51. As the sampling tube and the drain tube, for example, a pump (not shown) such as a peristaltic pump may be connected to the drain tube, and the sample to be measured may be introduced into the sample container 10 and discharged by suction by the pump. Furthermore, the sampling tube can also be connected to an automatic sampler for continuous automatic measurement of a large number of samples to be measured.
A temperature sensor 40 such as a thermistor is disposed near the front end 10a of the sample container 10. The temperature of the sample container 10 is feedback-controlled to a predetermined reference temperature based on the temperature measured by the temperature sensor 40 by a thermostatic block 53 containing a metal such as aluminum and having a thermoelectric element such as a peltier element (not shown).
The wall thickness of the glass tube constituting the sample container 10 is preferably 0.2mm or less. If the glass tube has a wall thickness of 0.2mm or less, the sample container 10 has excellent thermal conductivity, and therefore, when a sample to be measured having a temperature different from the reference temperature is introduced, the time from the introduction of the sample to the sample container 10 reaching the reference temperature is shortened, and the density can be measured in a short time. When the wall thickness of the glass tube exceeds 0.2mm, the thermal conductivity of the glass tube is reduced, and the time from the introduction of the sample to be measured to the sample container 10 reaches the reference temperature is prolonged, and thus the measurement of the density may take a relatively long time. The length L from the front end 10a to the fixed end 10b of the sample container 10 is preferably 60 to 90mm. If the length L is within the above range, the vibration cycle in the state where the sample to be measured is accommodated becomes appropriate, and the accuracy of determination of the mixing of bubbles can be improved. If the length L exceeds the above range, the vibration period in the state where the sample to be measured is stored becomes excessively short or long, and thus the accuracy of determination of the mixing of bubbles may be deteriorated. Further, since the vibrating densitometer 1 can be used for density measurement of a smaller amount of a sample to be measured than a float-type densitometer or the like, the volume of the sample container 10 is preferably 1mL or less.
The excitation unit 20 is a driving coil disposed at a position facing the permanent magnet 11. The excitation unit 20 causes the sample container 10 to vibrate by applying a magnetic field change generated by a drive current of a predetermined frequency flowing through the drive coil to the permanent magnet 11. The vibration of the sample container 10 is detected by a measuring unit 30 described later, and a driving current synchronized with the vibration cycle of the sample container 10 is applied to the driving coil based on the detection signal. As a result, the sample container 10 resonates with the frequency of the driving current flowing through the driving coil, and vibrates in the natural vibration period. The excitation means 20 changes the driving force by controlling the voltage applied to the driving coil or the current flowing through the driving coil by a driving control means 80 described later.
The measurement unit 30 includes an LED31 and a light receiving element 32. The LED31 and the light receiving element 32 are disposed so as to sandwich a curved portion of a U-shaped glass tube constituting the sample container 10 in the extending direction. If the sample container 10 vibrates, the intensity of light emitted from the LED31 and transmitted through the sample container 10 varies in accordance with the vibration period. The light receiving element 32 that continuously receives the transmitted light measures the vibration period of the sample container 10 based on a detection signal that detects the fluctuation of the transmitted light. The measuring unit 30 is not limited to the optical measurement, and may measure the vibration cycle of the sample container 10 in other manners. For example, the measurement unit 30 may be constituted by a detection coil disposed at a position facing the permanent magnet 11 fixed to the distal end 10a of the sample container 10. By detecting a change in the magnetic field generated by the movement of the permanent magnet 11 due to the vibration of the sample container 10 in the detection coil, the vibration cycle of the sample container 10 can be measured from the detection signal.
< arithmetic part >
The arithmetic unit 200 can be configured as an integrated circuit that executes a part or all of the functions of the vibrating densitometer 1 by realizing the functions of controlling the operations of the vibrating densitometer by reading and executing a program recorded in a memory by a CPU in a computer having the CPU, the memory, and the like. The operation unit 200 includes, in addition to the frequency detection unit 60 and the calculation unit 70, which are means for performing density operation in the conventional vibrating densitometer, a drive control unit 80 for driving the excitation unit 20, and a determination unit 90 for determining the presence or absence of bubbles. The arithmetic unit 200 also controls the operation of the peltier element of the thermostatic block 53.
The frequency detection unit 60 refers to a clock signal from a crystal oscillator (not shown), and calculates the vibration period of the sample container 10 from the detection signal output from the light receiving element 32 of the measurement unit 30. The frequency detection unit 60 outputs the calculated vibration cycle of the sample container 10 to the calculation unit 70 and the determination unit 90.
The calculating unit 70 calculates the density of the sample to be measured by the above-described expression (1) using the vibration period input from the frequency detecting unit 60. The density of the sample to be measured calculated by the calculation unit 70 is used for display on a display unit (not shown) and recording in a memory. After the calculation of the density of the sample to be measured by the calculation unit 70 is completed, the calculation unit 200 notifies the completion of the measurement to a pump connected to the liquid discharge pipe, an automatic sampler connected to the sampling pipe, or the like. Thereby, the liquid discharge of the sample to be measured in the sample container 10 and the introduction of a new sample to be measured into the sample container 10 are performed.
The drive control unit 80 and the determination unit 90 are unique to the present invention. In the present invention, the mixing of bubbles into the sample container 10 is determined by the operation of the drive control unit 80 and the determination unit 90.
The drive control unit 80 has a function of changing the driving force of the excitation unit 20 to excite the sample container 10 to vibrate. Since the driving force of the excitation means 20 for vibrating the sample container 10 is proportional to the magnitude of the magnetic field change generated by the driving current flowing through the excitation means 20, the driving control means 80 can control the driving force of the excitation means 20 by setting the voltage applied to the driving coil or the current flowing through the driving coil by a digital-to-analog conversion circuit (hereinafter, referred to as a "D/a converter") or the like. The amplitude of the vibrations generated at the sample container 10 also varies in proportion to the magnitude of the voltage or current. By such voltage or current control, the drive control unit 80 drives the excitation unit 20 with the first driving force at the time of a normal operation for measuring the density of the sample to be measured, and temporarily changes the excitation unit 20 from the first driving force to the second driving force to drive the sample at the time of a determination of the operation of mixing of bubbles. The second driving force is preferably 1/5 to 1/2 times the first driving force. If the second driving force is within the above range, the change in the vibration period is greatly different between when there is a bubble in the sample container 10 and when there is no bubble, and the presence or absence of a bubble can be accurately determined. If the second driving force is less than 1/5 times the first driving force, or if the second driving force exceeds 1/2 times the first driving force, the vibration cycle may be similarly changed when there is a bubble in the sample container 10 and when there is no bubble, and it may be impossible to accurately determine whether there is a bubble.
The determination unit 90 obtains a vibration cycle (hereinafter referred to as a "first vibration cycle") measured by the measurement unit 30 in the sample container 10 excited by the excitation unit 20 driven by the first driving force, and a vibration cycle (hereinafter referred to as a "second vibration cycle") measured by the measurement unit 30 in the sample container 10 excited by the excitation unit 20 driven by the second driving force, and determines the presence or absence of bubbles in the sample container 10 based on an absolute value of a difference between the first vibration cycle and the second vibration cycle (hereinafter referred to as a "vibration cycle difference"). Specifically, the vibration period difference of the determination unit 90 between the first vibration period and the second vibration period is 1.5x10 -2 In the case of a mu second or more,the presence of bubbles is detected. Here, the first vibration cycle is preferably a vibration cycle measured by the measuring unit 30 immediately before the driving force of the excitation unit 20 is changed from the first driving force to the second driving force, and the second vibration cycle is preferably a vibration cycle measured by the measuring unit 30 at any time point between 8 and 10 seconds after the driving force of the excitation unit 20 is changed to the second driving force.
< determination action of bubble mixing >
Fig. 2 is a diagram showing the measurement result of the vibration cycle in the measurement unit 30. Fig. 3 is a diagram schematically showing the position of the bubble in the sample container 10. The measurement result shown in fig. 2 (a) is a measurement result of measuring the vibration cycle in the sample container 10 without mixing the bubbles in the state where the temperature of the sample container 10 is stabilized at 20 ℃ using water as the sample to be measured. The measurement result shown in fig. 2 (b) is a measurement result of measuring the vibration cycle in the sample container 10 at a position (position a in fig. 3) where the bubble is mixed into the tip 10a in a state where the temperature of the sample container 10 is stabilized at 20 ℃ using water as the sample to be measured. In fig. 2 (a) and (b), the vibration cycle was measured at a 1.75 second cycle.
In the measurement of the vibration cycle in the sample container 10 in which no air bubbles are mixed as shown in fig. 2 (a), the drive control unit 80 drives the excitation unit 20 with the first driving force until time t0, then drives the sample container with the second driving force until time t1 after 8.75 seconds from time t0, and then drives the sample container again with the first driving force after time t 1. At this time, the output of the D/a converter is set so that the current flowing through the driving coil of the excitation unit 20 at the time of driving under the second driving force becomes 1/4 times the current flowing through the driving coil of the excitation unit 20 at the time of driving under the first driving force, thereby controlling the second driving force to be 1/4 times the first driving force. By such control, in the sample container 10 in which no air bubbles are mixed, the vibration cycle becomes approximately constant until time t0 when the excitation unit 20 is driven with the first driving force, and when the driving force of the excitation unit 20 is reduced from the first driving force to the second driving force at time t0, the vibration cycle is also temporarily reduced, and the sample container returns to the and state after about 5 measurement cycles (8.75 seconds) from the reduction of the driving forceThe value at which the vibration cycle approaches at time t0 before the driving force is changed. When the driving force of the excitation means 20 is increased from the second driving force to the first driving force at time t1, the vibration cycle is also temporarily increased, and the value close to the vibration cycle at time t0 is restored again after the increase of the driving force by about 5 measurement cycles (8.75 seconds). In this measurement, the vibration period difference d1 between the first vibration period measured at time t0 immediately before the driving force of the excitation unit 20 is changed from the first driving force to the second driving force and the second vibration period measured at time t1 after 8.75 seconds from the time when the driving force of the excitation unit 20 is changed to the second driving force is as small as 3.7x10 is due to the fluctuation pattern of the vibration period -3 Mu seconds. In this way, the threshold value 1.5x10 for determining the presence of the air bubbles in the sample container 10 becomes insufficient by the vibration cycle difference d1 -2 In μsecond, the determination unit 90 can determine that no air bubbles are mixed in the sample container 10.
On the other hand, in the measurement of the vibration cycle in the sample container 10 in which the bubbles are mixed as shown in fig. 2 (b), the drive control unit 80 drives the excitation unit 20 with the first driving force until time t0, then drives the sample container with the second driving force until time t1 after 8.75 seconds from time t0, and then drives the sample container with the first driving force again after time t1, as in the case of fig. 2 (a). By such control, in the sample container 10 in which the bubbles are mixed, if the driving force of the excitation means 20 is reduced from the first driving force to the second driving force at time t0, the vibration cycle temporarily increases in contrast to the sample container 10 in which the bubbles are not mixed. Further, in the sample container 10 in which the air bubbles were not mixed, the value was recovered to a value close to the vibration period at the time t0 immediately before the driving force was changed in about 5 measurement periods (8.75 seconds) from the change of the driving force, but the vibration period was continued to rise from the change of the driving force to the time point when about 5 measurement periods (8.75 seconds) passed in the sample container 10 in which the air bubbles were mixed. In this measurement, the first vibration period measured at time t0 immediately before the driving force of the excitation unit 20 is changed from the first driving force to the second driving force and the time after 8.75 seconds from the time when the driving force of the excitation unit 20 is changed to the second driving force are caused by the fluctuation pattern of the vibration periodThe vibration period difference d2 of the second vibration period measured at the time t1 becomes larger than 2.6X10 -1 Mu seconds. In this way, the vibration cycle difference d2 becomes the threshold value 1.5x10 for determining the presence of the air bubbles in the sample container 10 -2 Mu second or more, the determination unit 90 can determine that bubbles are mixed in the sample container 10.
< measurement temperature >
The effect of the temperature of the sample container 10 on the vibration cycle difference was studied. Fig. 4 is a graph showing the measurement result of the vibration cycle in the sample container 10 without air bubbles mixed in a state where there is a change in temperature after the introduction of the sample to be measured. In the measurement of the vibration cycle shown in fig. 4, water is used as a sample to be measured, and the calculation unit 200 controls the peltier element of the thermostatic block 53 so that the sample container 10 is maintained at the reference temperature, that is, 20.0 ℃, and the sample to be measured at 21 ℃ is introduced into the sample container 10. The drive control unit 80 normally drives the excitation unit 20 with the first driving force, but drives the excitation unit 20 with the second driving force for each of 8.75 seconds until the temperature from the introduction of the sample to be measured into the sample container 10 reaches 20.0 ℃ which is the reference temperature. At this time, the output of the D/a converter is set so that the current flowing through the driving coil of the excitation unit 20 at the time of driving under the second driving force becomes 1/4 times the current flowing through the driving coil of the excitation unit 20 at the time of driving under the first driving force, thereby controlling the second driving force to be 1/4 times the first driving force.
When the exciting unit 20 is driven with the second driving force when the temperature of the sample container 10 is less than 20.1 ℃, the vibration period difference d13 between the first vibration period measured immediately before the first driving force is changed to the second driving force and the second vibration period measured 8.75 seconds after the driving force of the exciting unit 20 is changed to the second driving force becomes 6.3×10 -3 Mu second, vibration period difference d14 became 0 mu second, and vibration period difference d15 became 3.7X10 -3 Mu seconds. These vibration period differences are insufficient to determine the threshold value of 1.5X10 for the presence of bubbles in the sample container 10 -2 Mu second, it can be determined that no bubbles were mixed. As described above, in the vibrating densitometer 1 of the present invention, the sample at the time of mixing of the bubbles into the sample container 10 is determinedThe temperature of the product container 10 is preferably less than 0.1 c from the reference temperature.
On the other hand, when the excitation unit 20 is driven with the second driving force when the temperature of the sample container 10 exceeds 20.1 ℃, the vibration period difference d11 between the first vibration period measured immediately before the change from the first driving force to the second driving force and the second vibration period measured 8.75 seconds after the change of the driving force of the excitation unit 20 to the second driving force becomes 8.4×10 -2 Mu second, the vibration period difference d12 becomes 3.3X10 -2 Mu seconds. In this way, when the temperature of the sample container 10 is higher than the reference temperature by 0.1 ℃, even if no air bubbles are mixed in the sample container 10, the difference between the vibration period of the first vibration period and the vibration period of the second driving force becomes 1.5x10 as the threshold value for determining the presence of air bubbles in the sample container 10 -2 Mu second or more. For this reason, in the vibrating densitometer 1 of the present invention, when the difference between the temperature of the sample container 10 and the reference temperature is 0.1 ℃ or more at the time of determining the mixing of bubbles into the sample container 10, the threshold value for determining the presence of bubbles in the sample container 10 is preferably set to be larger than the rising value of the vibration cycle assumed by the temperature change by 1.5×10 -2 Mu seconds.
< location of bubble in sample Container >
The effect of the position of the air bubble in the sample container 10 on the vibration cycle difference was studied. In the sample container 10, since the temperature of the sample container 10 is stabilized at 20 ℃ in the state where the air bubbles exist at each of the positions a to E and in the state where the air bubbles do not exist, the vibration cycle difference between the first vibration cycle measured immediately before the change from the first driving force to the second driving force and the second vibration cycle measured after the change from the driving force of the excitation unit 20 to the second driving force is measured by driving the excitation unit 20 with the first driving force for 8.75 seconds and then driving with the first driving force again after driving the excitation unit 20 with the second driving force is measured by using water as the sample to be measured. At this time, the output of the D/a converter is set so that the current flowing through the driving coil of the excitation unit 20 at the time of driving under the second driving force becomes 1/4 times the current flowing through the driving coil of the excitation unit 20 at the time of driving under the first driving force, thereby controlling the second driving force to be 1/4 times the first driving force. In addition, in the state where bubbles exist at each of positions a to E and in the state where bubbles do not exist as shown in fig. 3, the density is calculated in the calculating unit 70.
TABLE 1
As shown in table 1, when the air bubbles are present at the position A, B or C of the section of 1/2 or less from the front end 10a to the fixed end 10b of the sample container 10, the difference between the density calculated by the calculating unit 70 and the density calculated by the calculating unit 70 when the air bubbles are not mixed in the sample container 10 is at most 2.0×10 -2 g/cm 3 An error of 2.0% is produced. In the case where the bubble exists at the position A, B or C, the difference between the vibration period of the first vibration period and the second vibration period becomes 2.5X10 -1 Mu second or more. In this way, even in the case of either of the bubble existence positions A, B or C, the vibration period difference becomes larger than the threshold value of 1.5×10 for determining the existence of the bubble in the sample container 10 -2 Mu seconds are large. For this reason, when the air bubbles exist in the section from the front end 10a to the fixed end 10b of the sample container 10, the determination unit 90 can detect the presence of the air bubbles in the sample container 10, and the density calculated by the calculation unit 70 can be handled as the density of the error caused by the presence of the generated air bubbles.
On the other hand, when the bubble exists at the position D, E in the section from the fixed end 10b to the front end 10a of the sample container 10 equal to or less than 1/2, the difference between the vibration period of the first vibration period and the vibration period of the second vibration period becomes 3.3x10 -3 And μ seconds or less. For this purpose, in the determination unit 90, a threshold value of 1.5x10 based on detecting the presence of air bubbles in the sample container 10 is used -2 Mu seconds, the presence of air bubbles in the sample container 10 could not be detected. However, in the case where the air bubbles exist in the sample container 10 at the position D or E, the difference between the density calculated in the calculating unit 70 and the density calculated in the calculating unit 70 in the case where the air bubbles are not mixed in the sample container 10 is 1.4×10 -3 g/cm 3 The error stays below 0.14%. For this reason, even if the air bubbles exist in the sample container 10 at the position D or E, the density calculated by the calculating unit 70 can be handled as a density having practically sufficient accuracy regardless of the existence of the air bubbles.
< viscosity of sample to be measured >
The effect of the viscosity of the sample to be measured on the vibration cycle difference was investigated. Using a density of 0.85g/cm 3 And a viscosity standard solution JS50 with a viscosity of 42 mPas and a density of 0.86g/cm 3 And a viscosity standard solution JS200 with a viscosity of 172 mPas or a density of 0.87g/cm 3 In the sample container 10, the viscosity standard solution JS500 having a viscosity of 436mpa·s was used as the sample to be measured, and in the state where the air bubbles were present at each of the positions a to E shown in fig. 3 and in the state where the air bubbles were not present, after the temperature of the sample container 10 had stabilized at 20 ℃, the excitation unit 20 was driven at the first driving force, and after that, was driven at the second driving force for 8.75 seconds, and then was driven again at the first driving force, whereby the difference between the vibration cycle of the first vibration cycle measured immediately before the change from the first driving force to the second driving force and the vibration cycle of the second vibration cycle measured after 8.75 seconds from the change of the driving force of the excitation unit 20 to the second driving force was measured. At this time, the output of the D/a converter is set so that the current flowing through the driving coil of the excitation unit 20 at the time of driving under the second driving force becomes 1/4 times the current flowing through the driving coil of the excitation unit 20 at the time of driving under the first driving force, thereby controlling the second driving force to be 1/4 times the first driving force. In addition, in a state where bubbles exist at each of positions a to E shown in fig. 3 and in a state where no bubbles exist, the density is calculated in the calculating unit 70. Table 2 shows the measurement results of the case where the viscosity standard solution JS50 was used as the sample to be measured, table 3 shows the measurement results of the case where the viscosity standard solution JS200 was used as the sample to be measured, and table 4 shows the measurement results of the case where the viscosity standard solution JS500 was used as the sample to be measured.
TABLE 2
As shown in table 2, when the viscosity standard solution JS50 having a viscosity of 42mpa·s is used as the sample to be measured, if a bubble exists at a position A, B or C in the region of 1/2 or less from the front end 10a to the fixed end 10b of the sample container 10, the difference between the density calculated by the calculation unit 70 and the density calculated by the calculation unit 70 when no bubble is mixed in the sample container 10 becomes 4.7x10 at the maximum -3 g/cm 3 An error of 0.6% is produced. In the case where the bubble exists at the position A, B or C, the difference between the vibration period of the first vibration period and the second vibration period becomes 4.8X10 -2 Mu second or more. In this way, when the viscosity standard solution JS50 is used as the sample to be measured, even if the air bubble exists at either one of the positions A, B and C, the vibration cycle difference becomes larger than the threshold value 1.5×10 for determining the existence of the air bubble in the sample container 10 -2 Mu seconds are large. For this reason, when the viscosity standard solution JS50 having a viscosity of 42mpa·s is used as the sample to be measured, if the air bubbles are present in the region of 1/2 or less from the front end 10a to the fixed end 10b of the sample container 10, the determination unit 90 can detect the presence of the air bubbles in the sample container 10, and the density calculated by the calculation unit 70 can be handled as the density of the error caused by the presence of the generated air bubbles.
TABLE 3
As shown in table 3, when the viscosity standard solution JS200 having a viscosity of 172mpa·s is used as the sample to be measured, if the air bubbles are present at the position B of the front end 10a of the sample container 10, the difference between the density calculated by the calculation unit 70 and the density calculated by the calculation unit 70 when the air bubbles are not mixed in the sample container 10 is 4.0×10 -3 g/cm 3 An error of 0.5% is produced. In the case where the bubble exists at the position B, the vibration period difference between the first vibration period and the second vibration period becomes 3.5×10 -2 Mu seconds. In this way, when the viscosity standard solution JS200 is used, if bubbles are present at the positionB, the vibration period difference becomes larger than the threshold value of 1.5×10 for determining the presence of air bubbles in the sample container 10 -2 Mu seconds are large. For this reason, even when the viscosity standard solution JS200 having a viscosity of 172mpa·s is used as the sample to be measured, if the air bubbles are present near the tip 10a of the sample container 10, the determination unit 90 can detect the presence of the air bubbles in the sample container 10, and the density calculated by the calculation unit 70 can be handled as the density of the error caused by the presence of the generated air bubbles.
On the other hand, when the air bubbles are present at the positions A, C to E, the vibration period difference between the first vibration period and the second vibration period becomes 8.0x10 -3 And μ seconds or less. For this reason, when the viscosity standard solution JS200 having a viscosity of 172mpa·s is used as the sample to be measured, the determination unit 90 is based on the threshold value 1.5×10 for detecting the presence of the air bubbles in the sample container 10 -2 Mu seconds, the presence of air bubbles in the sample container 10 could not be detected. However, when the viscosity standard solution JS200 having a viscosity of 172mpa·s is used as the sample to be measured, if bubbles are present in the sample container 10 at the positions A, C to E, the difference between the density calculated by the calculation unit 70 and the density calculated by the calculation unit 70 when no bubbles are mixed in the sample container 10 becomes 1.4×10 -3 g/cm 3 The error stays below 0.17%. For this reason, when the viscosity standard solution JS200 having a viscosity of 172mpa·s is used as the sample to be measured, even if bubbles are present at the positions A, C to E in the sample container 10, the density calculated by the calculation unit 70 can be handled as a density having practically sufficient accuracy regardless of the presence or absence of the bubbles.
TABLE 4
As shown in table 4, when the viscosity standard solution JS500 having a viscosity of 436mpa·s is used as the sample to be measured, if bubbles are present at the position B of the front end 10a of the sample container 10, the density calculated by the calculating unit 70 is calculated, and if no bubbles are mixed in the sample container 10, the density calculated by the calculating unit 70 is calculatedThe calculated density was compared and the difference was 2.6X10 -3 g/cm 3 A somewhat large error of 0.3% is produced. However, when the viscosity standard solution JS500 having a viscosity of 436 mPas is used as the sample to be measured, the difference between the vibration period of the first vibration period and the vibration period of the second vibration period becomes 6.3X10 even if the air bubble exists at any of the positions A to E -3 A vibration cycle difference of 3.0X10% or less from the case where no bubble exists in the sample container 10 -3 Since μsec is an extremely close value, it is difficult to determine whether or not there is any bubble in the sample container 10 based on the vibration cycle difference.
According to the above-described study, in consideration of the influence of the viscosity of the sample to be measured on the vibration cycle difference, in the vibrating densitometer 1 of the present invention, when an error occurs in the density calculated in the calculating unit 70 due to the mixing of the air bubbles into the sample container 10, the viscosity of the sample to be measured is preferably 200mpa·s or less in order to properly detect the air bubbles in the sample container 10.
As described above, the vibrating densitometer 1 according to the present invention can determine the presence or absence of air bubbles in the sample container 10 based on the difference between the first vibration period of the sample container 10 measured by the measuring unit 30 when the exciting unit 20 is driven with the first driving force and the second vibration period of the sample container 10 measured by the measuring unit 30 after the driving force of the exciting unit 20 is changed to the second driving force, and therefore, it is not necessary to repeat the introduction of the sample to be measured into the sample container 10 and the measurement of the vibration period in order to confirm the discharge of the air bubbles before the density measurement of the sample to be measured, and it is possible to determine the presence or absence of the air bubbles while maintaining the state in which the sample to be measured is stored in the sample container 10. Therefore, the presence or absence of the air bubble can be determined in a short time without generating a plurality of temperature changes in the sample container 10 accompanying repetition of introduction of the sample to be measured. As a result, the time from introduction of the sample to be measured to measurement of the density can be shortened while preventing occurrence of errors due to mixing of bubbles.
Industrial applicability
The vibrating densitometer of the present invention can be used for density measurement of various samples such as concentration management of a cool beverage.
Symbol description-
1. Vibrating densimeter
10. Sample container
10a front end
10b fixed end
20. Excitation unit
30. Measuring unit
80. Drive control unit
90. And a determination unit.
Claims (7)
1. A vibrating densitometer for measuring the density of a sample to be measured contained in a sample container, the vibrating densitometer comprising:
an excitation unit that excites and vibrates the sample container;
a measurement unit that measures the excited vibration cycle of the sample container;
a drive control unit that drives the excitation unit with a first driving force and a second driving force smaller than the first driving force; and
and a determination unit that determines whether or not bubbles are present in the sample container based on a difference between a first vibration period of the sample container excited by the first driving force and a second vibration period of the sample container excited by the second driving force.
2. The vibrating densitometer of claim 1, wherein,
the second driving force is 1/5 to 1/2 times the first driving force.
3. A vibrating densitometer according to claim 1 or 2, characterized in that,
the first vibration cycle is a vibration cycle measured by the measuring unit immediately before the driving force of the exciting unit is changed from the first driving force to the second driving force,
the second vibration cycle is a vibration cycle measured by the measurement unit at any time point between 8 and 10 seconds from when the driving force of the excitation unit is changed to the second driving force.
4. A vibrating densitometer according to any of claims 1 to 3, wherein,
the difference between the first vibration period and the second vibration period of the judging unit is 1.5X10 -2 If μ seconds or more, it is determined that the bubbles are present.
5. The vibrating densitometer of any of claims 1 to 4, wherein,
the viscosity of the sample to be measured is 200 mPas or less.
6. The vibrating densitometer of any of claims 1-5, wherein
The sample container is a U-shaped tube,
the determination unit determines whether or not the air bubble is present in a section of 1/2 or less from the front end to the fixed end of the U-shaped pipe.
7. A bubble mixing determination method for determining mixing of bubbles into a sample container in a vibrating densitometer for measuring a density of a sample to be measured stored in the sample container, the bubble mixing determination method comprising:
a first excitation step of exciting the sample container to vibrate with a first driving force;
a first measurement step of measuring a first vibration cycle of the sample container excited by the first driving force;
a second excitation step of exciting the sample container to vibrate with a second driving force smaller than the first driving force;
a second measurement step of measuring a second vibration cycle of the sample container excited by the second driving force; and
and a determination step of determining the presence or absence of bubbles in the sample container based on a difference between the first vibration period and the second vibration period.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
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| JP2020174557A JP7473198B2 (en) | 2020-10-16 | 2020-10-16 | Vibration type density meter and method for determining whether air bubbles are present in the vibration type density meter |
| JP2020-174557 | 2020-10-16 | ||
| PCT/JP2021/036800 WO2022080187A1 (en) | 2020-10-16 | 2021-10-05 | Vibration-type density meter, and air bubble entrainment determination method in vibration-type density meter |
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| CN116075707A true CN116075707A (en) | 2023-05-05 |
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| JP (1) | JP7473198B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH05180680A (en) * | 1991-12-27 | 1993-07-23 | Tokico Ltd | Vibration-type measuring device |
| JPH07286880A (en) * | 1994-04-20 | 1995-10-31 | Tokico Ltd | Vibration-type measuring instrument |
| JPH09196730A (en) * | 1996-01-19 | 1997-07-31 | Tokico Ltd | Vibration-type measuring apparatus |
| JP5180680B2 (en) | 2008-05-20 | 2013-04-10 | サンデン株式会社 | Refrigeration cycle |
| JP3181293U (en) | 2012-11-16 | 2013-01-31 | 京都電子工業株式会社 | Density measuring device |
| JP7286880B2 (en) | 2019-12-09 | 2023-06-05 | テレフオンアクチーボラゲット エルエム エリクソン（パブル） | Method and associated wireless device for providing information messages including RACH reports |
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