JPH0669749U - Volume measuring device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a volume measuring device based on the gas volume method, which takes a short time to stabilize data and can perform measurement at an arbitrary set temperature. [Structure] A temperature sensor 4 for measuring the temperature of a constituent member 3 of a measurement sample chamber 1 and an expansion chamber 2, a heat exchanger 5 directly attached to the constituent member 3 and capable of absorbing and generating heat, and a temperature sensor. A temperature adjusting circuit 8 for maintaining the temperature of the constituent members 3 of the chambers 1 and 2 at a set temperature by inputting the output of 4 to drive the heat exchanger 5 is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an apparatus for measuring the volume of a sample to be measured based on the gas volume method, and more particularly to a volume measuring apparatus based on the constant volume method, which can be applied to, for example, a density meter.

[0002]

[Prior art]

 A method called a gas volume method is known as a method for measuring the volume of a solid. The gas volumetric method is a volumetric measurement method that utilizes the fact that a sample in gas is excluded by the volume of the sample, and can be classified into a constant volume method, an indefinite volume method, a pressure comparison method, etc. depending on the detection method. In addition, since there is no risk of sample dissolution compared to liquid permeation method, etc., it is advantageous for volume measurement of powder and granules, and since gas is used as the medium, it can be used in the small holes of the sample. In addition, there is an advantage that the medium surely enters and the true volume can be accurately measured even in the case of a porous sample. Among them, the constant volume method and the so-called constant volume expansion method, which utilizes the expansion process, are characterized in that they do not require moving parts such as pistons and have a simple structure.

A volume measuring apparatus utilizing the constant volume expansion method generally has a structure in which a measurement sample chamber and an expansion chamber each having a known inner volume are provided and these are connected via an on-off valve. In measurement, the same ambient pressure chambers of the pressure is Mazuko P _a (usually atmospheric pressure) and. State equation of the expansion chamber of the gas in this state, the inner volume of the expansion chamber V _EXP, ambient temperature and T _a, the number of moles of n _E of the expansion chamber of the gas, when the gas constant and R, P _a V _EXP = n _E RT _a ··· (1)

Next, the sample to be measured is accommodated in the sample chamber for measurement with the on-off valve closed, and the sample chamber is pressurized to a constant pressure P ₁ . In this state, the gas state in the measurement sample chamber is expressed as follows: V _{CELL is} the internal volume of the measurement sample chamber, n _{C is} the number of moles of gas in the chamber, and V _SAMP is the volume (unknown) of the test sample. Then, P ₁ (V _CELL −V _SAMP ) = n _C RT _a ··· (2).

After that, the sample chamber and the expansion chamber are connected by opening the on-off valve. As a result, the gas in the system expands and its pressure changes to P ₂ . State equation of the gas in this state is _{P 2 (V CELL -V SAMP +} V EXP) = n C RT a + n E RT a ·· (3). The volume of the sample V _{SAMP to} be measured can be calculated by the following equation (4) derived from the equations (1) to (3).

V _SAMP = V _CELL −V _EXP / (P _1g / P _2g −1) ··· (4) where P _1g = P ₁ −P _a , P _2g = P ₂ −P _a In the volume measuring device based on the expansion method, because of the measurement theory using the equation of state of gas, in principle, the time between the introduction of gas into the sample chamber and the opening into the expansion chamber It is necessary to perform pressure measurement with the system temperature kept constant, including gas, or always calculate temperature and make corrections to calculate the volume from the pressure. However, in reality, it is difficult to keep the temperature of the entire system constant due to changes in the ambient temperature, etc. It is also difficult to add in reality.

Therefore, in the conventional measuring apparatus of this type, the sample chamber for measurement and the expansion chamber are treated so that the temperature change during measurement is minimized while the temperature change is treated as if there is no temperature change during measurement. It is formed by an integral block made of a material such as aluminum having good heat conduction. In addition, measures such as placing the sample to be measured in the sample chamber for measurement after waiting for thermal equilibrium with the device at a location where it can be considered that the temperature is almost the same as that of the device.

[0008]

[Problems to be solved by the device]

 By the way, the temperature change of the system containing the gas in each chamber has a direct effect on the accuracy of the measured value as described above.The factor is that in addition to the change of the ambient temperature, The temperature difference between the sample to be measured and the gas introduced into the sample chamber (usually an inert gas) cannot be ignored. Therefore, in the measurement, stable data can be obtained when waiting for thermal equilibrium between them until they all reach the same temperature before starting the measurement or when starting the measurement in the presence of a temperature difference. It is necessary to repeat the measurement until the measurement is completed, and in any case it will take a long time.

Moreover, even if the apparatus, the sample to be measured, and the inert gas have the same temperature and stable data are obtained, and even if the volume is calculated based on the data, the volume is naturally these. It is the volume at the temperature at which thermal equilibrium is reached, not at the controlled temperature.

This means that in a sample having a large coefficient of thermal expansion, the difference in temperature during measurement has a great influence on the measurement result. Also, when calculating the density of the sample to be measured using this volume measurement result, if the temperature at the time of measurement is specified in the standards such as JIS applied to the sample, it must be converted to that temperature. It will have to be done. However, when such conversion is performed, the converted value is not a density but a physical quantity called specific gravity. Here, in the volume or density measurement method based on other measurement methods, the temperature adjustment during measurement is relatively easy, so in practice, avoid the above conversion as much as possible and measure at the temperature determined by the standard. Is done. For example, the density and specific gravity of plastics are specified in JIS K 7112, and there are the density gradient tube method, the water displacement method, the pycnometer method, and the float-sink method. Is measured, and if the measured temperature is other than that temperature, it is converted to 23 ° C and the specific gravity is determined. In order to obtain correlation data between such other measuring method and the gas volume method, the gas volume method should also be measured at 23 ° C. In other words, the best way to obtain correlation data is to be able to maintain the sample temperature at the time of measurement not only in plastics but also in other samples at the temperature determined by the relevant JIS standards, but the conventional gas No measuring device based on the volumetric method has such a function.

The present invention has been made in view of the above circumstances, and it takes a shorter time for the data to stabilize than that of a conventional device, and a gas that can be measured at an arbitrary set temperature. The purpose is to provide a volume measuring device based on the volume method.

[0012]

[Means for Solving the Problems]

 A configuration for achieving the above object will be described with reference to FIG. 1 corresponding to an embodiment. The volume measuring apparatus of the present invention includes a measurement sample chamber 1 for storing a sample to be measured and a measurement sample chamber 1 for the measurement. An expansion chamber 2 communicating with the sample chamber 1 via an on-off valve (expansion valve) 15 is formed by a constituent member (block) 3 made of a material having good heat conduction. Is a temperature at which the temperature of the constituent member 3 of the measurement sample chamber 1 and the expansion chamber 2 is measured in a volume measuring apparatus based on the gas volume method, which is provided with an on-off valve (introduction valve) 14 for introducing an inert gas. A sensor 4, a heat exchanger 5 that is directly attached to the first and second constituent members 3 of each chamber in common and capable of absorbing and generating heat, and driving the heat exchanger 5 by inputting the output of the temperature sensor 4. Therefore, the constituent members 3 of the chambers 1 and 2 are Accordingly, it characterized in that it comprises a temperature control circuit 8 to keep the temperature at a set temperature.

[0013]

[Action]

 The temperature of the constituent member 3 of the measurement sample chamber 1 and the expansion chamber 2 is measured by the temperature sensor 4, and heat exchange capable of absorbing and generating heat directly attached to the constituent member 3 so that the measurement result matches the set temperature. The vessel 5 operates. Since the heat exchanger 5 is commonly attached to the measurement sample chamber 1 and the expansion chamber 2 which are made of a material having good heat conduction, the sample W to be measured and the inside of the same chamber 1 which are put in the measurement sample chamber 1 Even if the temperature of the gas introduced into the chamber differs from the temperature of the constituent member 3, the temperatures of the measurement sample chamber 1 and the expansion chamber 2 are the same in a short time and reach the set temperature. Can achieve the purpose of.

[0014]

Embodiment FIG. 1 is a sectional view showing the structure of a basic embodiment of the present invention. A measurement sample chamber 1 for accommodating a sample W to be measured and an expansion chamber 2 are formed in one block 3 made of a material having good thermal conductivity, such as aluminum.

The measurement sample chamber 1 is provided with a detachable cap 11, and the sample W to be measured is stored in the measurement sample chamber 1 while being stored in the container 12. The measurement sample chamber 1 communicates with a pressure gauge 13 outside the block 3 through a pipe 31 formed in the block 3, and the sample chamber 1 has a pipe 32 and an inlet valve which is an on-off valve. An inert gas source such as a cylinder can be connected via 14.

The measurement sample chamber 1 and the expansion chamber 2 are in communication with each other via the conduits 33 and 34 in the block 3 and the expansion valve 15 which is an on-off valve. Further, the expansion chamber 2 is connected to a discharge valve 16 which is also an on-off valve via a pipe 35.

The output of the above-mentioned pressure gauge 13 is taken into the micro computer 10 through an AD converter (not shown), and the introduction valve 14, the expansion valve 15 and the discharge valve 16 are respectively provided with a micro. A control signal from the computer 10 opens and closes at a predetermined timing.

A temperature sensor 4 is attached to the block 3, and a heat exchanger 5 having a Peltier element as a driving source is directly attached to one surface of the temperature sensor 4 almost entirely. The Peltier element of the heat exchanger 5 is driven and controlled by a control signal from a temperature adjusting circuit 8 described later. Further, the heat exchanger 5 is provided with a heat sink / radiator 6, and a fan 7 for blowing air toward the heat sink / radiator 6 is disposed in the vicinity of the heat sink / radiator 6. Further, the periphery of the block 3 excluding the mounting portion of the heat exchanger 5 is covered with a heat insulating material 9. Note that 9a is a lid for loading and unloading the sample, and this lid 9a is also formed of a heat insulating material.

The Peltier element can heat or cool the block 3 by changing the direction of the electric current to flow. Therefore, when the block 3 is cooled, the heat absorber 6 dissipates heat absorbed by the block 3. It radiates heat to the surroundings, and when heating, it absorbs heat from the surroundings.

The temperature adjusting circuit 8 is provided with a temperature setter 8a and inputs the output of the temperature sensor 4 so that the temperature detection value by the temperature sensor 4 matches the set temperature by the temperature setter 8a. The direction and magnitude of the current flowing through the Peltier element of the heat exchanger 5 are changed. As a result, the temperature of the block 3 can be set higher or lower than the ambient temperature depending on the temperature set by the temperature setter 8a.

The measurement operation in the above embodiment of the present invention is as follows. The symbols such as P _a described in the following description correspond to the symbols in the above equations (1) to (4). Prior to the measurement, the temperature setting device 8a is operated to set the measurement temperature. As a result, the Peltier element of the heat exchanger 5 and the fan 7 operate, and thereafter, the temperature of the block 3 is controlled so as to match its set temperature.

After waiting until the temperature of the block 3 reaches a steady state, first, the lid 9 a of the heat insulating material 9 is opened, the cap 11 is removed, and the container 12 containing the sample W to be measured is placed in the measurement sample chamber 1. After inserting, the cap 11 is attached to seal the measurement sample chamber 1.

Next, the expansion valve 15 and the discharge valve 16 are opened, and the pressure gauge 13 measures P _a . In that state, only the introduction valve 14 is opened to pressurize the inside of the measurement sample chamber 1 to a pressure near P ₁ , then the introduction valve 14 is closed, and after waiting until an equilibrium state is reached, an accurate pressure P ₁ is set. taking measurement.

Next, the expansion valve 15 is opened to connect the measurement sample chamber 1 and the expansion chamber 2 to each other. When the pressure reaches equilibrium in this state, the pressure P ₂ is measured. Then, the discharge valve 16 is opened to return the pressures of the measurement sample chamber 1 and the expansion chamber 2 to the atmospheric pressure.

According to the operation of the embodiment of the present invention, the temperature of the block 3 is controlled by the Peltier element of the heat exchanger 5 so as to always match the set temperature even if the ambient temperature changes. Therefore, the volume can be measured at a desired temperature. Here, if the temperature of the sample W to be measured has a difference from the temperature of the block 3, after inserting the sample W to be measured, wait until both temperatures can be regarded as the same, or repeat until the data becomes stable. It suffices to perform the return measurement, and even in this case, even if the temperature of the block 3 changes due to the insertion of the sample W to be measured, the block 3 quickly reaches the set temperature by the Peltier element, the heat sink / radiator 6 and the fan 7. Since it is heated or cooled as described above, the temperature of the sample W to be measured also reaches the set temperature quickly.

Next, another embodiment of the present invention will be described. FIG. 2 is a cross-sectional view showing the structure, and this example shows a high precision type device developed from the previous example. In FIG. 2, the same members as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In addition to the basic structure shown in FIG. 1, this high precision type apparatus is provided with a gas heat exchange block 300 for an inert gas introduced into the measurement sample chamber 1, It is characterized in that a standby sample chamber 100 is provided for holding the measured sample W before measurement.

That is, in addition to the block 3 in which the measurement sample chamber 1 and the expansion chamber 2 are formed in one heat exchanger 5 driven by a Peltier element, an inert gas introduction valve 14 and an inert gas are provided. Gas heat exchange block 300 in which a conduit 300a communicating with the reactive gas source is formed, and a standby chamber block 301 in which the standby sample chamber 100 is formed are directly attached. Similarly to the block 3, the blocks 300 and 301 are also temperature-controlled so as to match the temperature set by the temperature setter 8a.

The gas heat exchange block 300 and the standby chamber block 301 have a structure that is thermally separated from the block 3, and the upper part of the standby sample chamber 100 is also made of a heat insulating material. Is provided with a lid 9b.

In the method of using such a high precision type device, the measurement temperature is set by the temperature setting device 8a prior to the measurement operation as in the above example. As a result, the Peltier element of the heat exchanger 5 and the fan 7 are driven, and the temperatures of the block 3, the gas heat exchange block 300, and the standby chamber block 301 are controlled to match their set temperatures. In this state, the container 12 containing the sample W to be measured is inserted into the measurement sample chamber 1 and the standby sample chamber 100, and the caps 11 are closed. Then, from the time when it can be considered that the temperatures of the block 3 and the sample W to be measured inside thereof, and the blocks 300 and 301 have reached the set temperature, the measurement is started in the same procedure as the above-mentioned example.

In this measurement operation, the inert gas passes through the pipe line 300a in the gas heat exchange block 300 provided in the preceding stage of the introduction valve 14 to reach a temperature close to the preset temperature in advance. Is introduced into the measurement sample chamber 1. Therefore, the heat conduction is worse than that of a solid, and the introduced gas, which takes a long time to reach the thermal equilibrium even if it is introduced into the measurement sample chamber 1, reaches the thermal equilibrium in a short time.

After the measurement of one sample is completed, the measured sample W in the standby sample chamber 100 is transferred to the measurement sample chamber 1 and another sample is further placed in the standby sample chamber 10 After inserting into 0, measurement is started. As a result, the next sample reaches the temperature of the block 3, that is, the set temperature during the measurement of the previous sample, and stable data can be obtained immediately after the measurement operation is started.

In the example of FIG. 2, one heat exchanger 5 controls the blocks 3, 300 and 301 to the same temperature, and the blocks 300 and 301 are heated with respect to the block 3. Separated. The reason is that the introduction of an inert gas with a large temperature difference and the storage of the sample for the next measurement do not adversely affect the block 3. However, even if such a configuration is not necessarily adopted, even if the entire block is configured as an integrated block, if the heat capacity of the block is large, the influence on the data is small. On the contrary, including the example of FIG. 2 and the example of FIG. 1, even if the measurement sample chamber 1 and the expansion chamber 2 are formed by separate blocks and these are directly attached to the single heat exchanger 5, The same effect can be obtained.

Further, the volume of the measurement sample chamber 1 is calibrated in the same manner as in the prior art by introducing a gas into the empty container 12 in a state of being housed therein. When using the container 12 described above, it is no problem if the volume of the sample chamber 1 is calibrated in advance using individual containers and the calculation is performed using the numerical value corresponding to the container used at the time of measurement.

Next, a configuration example of the heat exchanger 5 used in each of the above embodiments will be described. FIG. 3 shows an example thereof. In this example, a structure in which a plurality of Peltier elements 51 are sandwiched by plates 52 and 53 made of, for example, aluminum or copper having good heat conduction and fixed by screws 54 made of plastic having poor heat conduction is used. I am collecting. Then, for example, the plate 52 is directly fixed to the block 3 or 300 to 301, and the heat sink / radiator 6 is fixed to the plate 53.

The Peltier element 51 is a combination of a P-type semiconductor and an N-type semiconductor, and can cool or heat one surface side depending on the direction of the current. Therefore, by changing the direction of the current to the element 51, either the plate 52 side is heated and the plate 53 side is cooled, or the plate 52 side is cooled and the plate 53 side is heated, whichever is selected. can do.

The number of Peltier elements 51 may be determined according to the heat capacity of the controlled object and the target temperature. Further, regarding the temperature control of the gas introduced into the measurement sample chamber 1, a gas heat exchange block 300 having a pipe line 300a formed therein as shown in FIG. 2 is shown, for example, shown in FIG. Such a structure can be adopted.

In the example of FIG. 4, a cylindrical block 400 made of a material having good heat conduction is closely attached to the heat exchanger 5, and a gas is passed around the cylindrical block 400 to introduce the introduction valve 14. A pipe 401 made of a material having good heat conductivity is closely wound to guide the wire.

In each of the above embodiments, the heat exchanger 5 having a Peltier element as a driving source is used as the heat exchanger 5. However, the present invention is not limited to this, and the temperature control is performed outside the device. The temperature control of the block 3 or the blocks 300 and 301 in addition thereto may be performed by using the heat medium thus prepared. In this case, a pipe for passing the heat medium is formed in each block, or another member having a pipe for flowing the heat medium is attached to the mounting position of the heat exchanger 5 shown in each of the above examples. It can be configured to be attached.

[0040]

[Effect of device]

 As described above, according to the present invention, the common heat exchanger capable of absorbing and generating heat is directly attached to the measurement sample chamber and the expansion chamber, which are formed by the constituent members made of the material having good heat conduction. At the same time, the temperature measurement results of the components of the measurement sample chamber and expansion chamber were introduced, and a temperature control circuit was installed to control the heat exchanger so that the temperature would reach the set temperature. In the volume measuring device based on the gas volume method, which is the most suitable for obtaining the true volume of, it is possible to set the measurement temperature to an arbitrary temperature and control the ambient temperature like the conventional device of this type. Compared with the above, it has become possible to perform highly accurate measurement temperature control in a short time at low cost.

Further, since the device temperature is maintained at the set temperature even during the measurement, when used for the density measurement of the sample, the density gradient method which has been used conventionally and has an accuracy of about 4 digits below the decimal point is used. It has become possible to perform measurements with equivalent accuracy in a short time. As a result, when used for quality control, the feedback time to the production line was shortened, and it became possible to improve the quality of production.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a basic embodiment of the present invention.

FIG. 2 is a sectional view showing the structure of a high precision type embodiment of the present invention.

FIG. 3 is an explanatory diagram of a configuration example of a heat exchanger 5 that can be used in the present invention.

FIG. 4 is an explanatory diagram of a configuration example of a gas heat exchange section applicable to the embodiment of FIG.

[Explanation of symbols]

 1 Measurement Sample Chamber 2 Expansion Chamber 3 Block 4 Temperature Sensor 5 Heat Exchanger 6 Heat Sink / Dissipator 7 Fan 8 Temperature Control Circuit 8a Temperature Setting Device 9 Insulation Material 10 Microcomputer 13 Pressure Gauge 14 Introduction Valve 15 Expansion Valve 16 Discharge Valve 100 Standby sample chamber 300 Gas heat exchange block 301 Standby chamber block

Claims (1)

[Scope of utility model registration request] 1. A sample chamber for measurement that stores a sample to be measured,
In order to introduce an inert gas into the measurement sample chamber, the expansion chamber communicating with the measurement sample chamber via an on-off valve is formed by constituent members made of materials with good heat conduction. In the volume measuring device based on the gas volume method provided with the on-off valve, a temperature sensor for measuring the temperature of the constituent members of the measurement sample chamber and the expansion chamber,
The temperature of the constituent members of each chamber is directly attached to the constituent members of each chamber and capable of absorbing and generating heat, and driving the heat exchanger by inputting the output of the temperature sensor. A volume measuring device, comprising a temperature adjusting circuit for maintaining the temperature of the liquid at a set temperature.