JP3462013B2 - Method and apparatus for measuring residual gas volume - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas volume measuring method and apparatus for measuring the volume of gas other than dissolved carbon dioxide together with carbon dioxide in carbonated drinking water, beer, sparkling liquor, etc. The present invention relates to a gas volume measuring method and apparatus capable of accurately measuring a gas volume other than carbon dioxide in a time period.

[0002]

BACKGROUND ART carbon dioxide (CO ₂₎ and nitrogen (N ₂₎ with pressurized by soft drink filled in a container (carbonated water), beer, the air included in such happoshu Introduction As an apparatus for measuring a gas volume other than carbon dioxide gas, for example, as shown in FIG. 11, an airtight container 110 and, for example, sodium hydroxide (NaO) are provided in the airtight container 110.
H), calcium hydroxide (Ca (OH) ₂ ), potassium hydroxide (KOH), or the like, and an absorbent supply means 130 for supplying a carbon dioxide absorbent 120, and carbonated drinking water, beer, Some include a gas introducing means 140 for introducing a gas foamed from a test liquid such as sparkling liquor.

The airtight container 110 has a scale 111 on the top.
And an air vent pipe 112 that is in communication with the atmosphere.
And an air vent valve 113 for opening and closing the air vent tube 112
It has and.

The absorbent supply means 130 has an absorbent container 131 for storing the carbon dioxide absorbent 120, and an absorbent supply path 132 for communicating the head of the absorbent container 131 with the bottom of the airtight container 110. The air tight valve 110 of the airtight container 110 is opened, the tank 131 is lifted, the liquid level in the airtight container 110 is raised above the air vent valve 113, and then the air vent valve 113 is closed. The air in the container 110 is discharged and the airtight container 1
The inside of 10 is filled with carbon dioxide absorbent 120.

The gas introducing means 140 is provided with a test liquid container 141 containing a test liquid, a gas introducing passage 142 which is led from the test liquid container 141 and communicates with a lower portion of the airtight container 110, and a gas introducing member. A gas introduction valve (cock) 143 for opening and closing the passage 142 is provided.

After filling the airtight container 110 with the carbon dioxide absorbent 120 as described above, the gas introduction valve 1
43 is closed and the test liquid container 141 is vibrated to foam the gas, and then the gas introduction valve 143 is opened, whereby the gas foamed in the test liquid container 141 as described above is discharged. The gas is injected into the airtight container 110 through the gas introduction passage 142 with the internal pressure, and the bubbles thereof float above the airtight container 110.

The carbon dioxide gas contained in the bubbles injected into the airtight container 110 dissolves in the carbon dioxide gas absorbent,
Other gas components are accumulated in the upper portion of the airtight container 110 as residual gas.

The amount of residual gas accumulated in the upper portion can be confirmed by reading the scale, and when reading the scale, the absorbent container 131 is lifted and the liquid in the absorbent container 131 is lifted. It was necessary to keep the pressure in the airtight container 110 at atmospheric pressure by matching the surface with the liquid surface in the airtight container 110.

When the introduction of the gas into the airtight container 110 is completed, the gas introduction valve 143 is closed. After that, other gas components move to the upper part in the airtight container 110,
The liquid surface in the airtight container 110 foams. Therefore, in order to accurately measure the volume of residual gas (gas volume), it is necessary to read the scale 111 of the airtight container 110 after the bubbling has stopped.

[0010]

According to this conventional gas capacity measuring method and apparatus, the air in the airtight container 110 is previously supplied to the airtight container 110 and the gas introduction path 142,
There is a problem that accurate measurement cannot be performed unless all the air bubbles including the air bubbles attached to the inner surface of the air bleed tube 112 are discharged.

Further, when measuring the volume of the residual gas after introducing the gas, in order to reduce the measurement error, the airtight container 1
There is a problem that the volume of gas cannot be measured until the bubbling of the liquid surface due to the bubbles introduced into 10 is stopped, and the measurement time becomes long.

When the time to wait for this foaming is long, an antifoaming agent is used. Even in this case, however, it takes a considerable time for the foaming to be eliminated, and the cost of the antifoaming agent is high. In addition, there is a problem that it takes time and effort to add the defoaming agent.

Further, there is a problem that air bubbles adhere to the inner surface of the airtight container 110 after introducing the gas, which causes a measurement error.
In view of the above circumstances, it is an object of the present invention to provide a gas volume measuring method and device capable of highly accurately measuring a gas volume in a short time.

[0014]

The present invention takes the following means in order to achieve the above object. The present invention connects an airtight container filled with a carbon dioxide absorbent and a test solution container containing a test solution, and a gas containing carbon dioxide dissolved in the test solution is passed through the carbon dioxide absorbent. It is premised on a gas capacity measuring method of measuring the volume of residual gas remaining in the airtight container after the carbon dioxide gas is removed by introducing the gas into the airtight container.

On the basis of the above-mentioned premise, the present invention starts from a test liquid container 41 containing a test liquid in an airtight container 1 filled with the carbon dioxide absorbent 2 and a carbon dioxide gas dissolved in the test liquid. A gas containing is introduced. As a result, carbon dioxide gas is absorbed in the airtight container 1 to remove the carbon dioxide gas, and then a predetermined amount υ ₂ of the carbon dioxide gas absorbent ₂ is injected into the airtight container 1.

At this time, based on the injection amount υ ₂ and the pressures P _02, P ₂ in the airtight container 1 before and after the supply of the carbon dioxide absorbent 2, the residual gas volume (total volume) of the airtight container 1 is calculated. ) Χ ₂ is calculated according to the following formula 1.

[0017]

[Equation 1]

In this way, the injection amount of carbon dioxide absorbent 2
₂And the pressure P in the airtight container 1 before and after the injection_O2, P₂By
Residual gas volume χ₂The gas of the airtight container 1
In any part of the interior and the space communicating with it
Accurately the residual gas volume χ ₂Can be measured
It In other words, the carbon dioxide absorbent 2 in the airtight container 1 is foamed.
Accurate residual gas volume χ even when standing₂Can be measured
Also, air bubbles attached to the inner surface of the airtight container 1 etc.
Included residual gas volume χ₂Is calculated.

[0019] Therefore, the can be calculated residual gas volume chi ₂ before foaming of the airtight container 1 fits, it can be measured accurately residual gas volume chi ₂ in a short time. In the present invention, before measuring the residual gas volume χ ₂ , the initial gas volume χ ₁ enclosed in the airtight container ₁ is measured, and the initial gas volume (dead volume) χ is calculated from the residual gas volume χ _2. By subtracting ₁ , the volume of the gas containing carbon dioxide gas introduced into the airtight container, that is, the gas volume χ
Can be calculated.

That is, the airtight container 1 (see FIG. 5) filled with the carbon dioxide absorbent 2 is further charged with a predetermined amount of carbon dioxide absorbent 2.
Inject. Injection amount of carbon dioxide absorbent 2 at this time υ ₁
Based on the pressures P _O1 and P ₁ in the airtight container 1 before and after the injection, the initial gas volume χ ₁ is calculated according to the following formula 2.

[0021]

[Equation 2]

Thus, the injection amount of carbon dioxide absorbent 2 υ ₁
And the pressure P _O1 of the front and rear of the airtight container 1 infusion, when obtaining the initial gas volume chi ₁ by P _1, how gas is distributed to any part of the space through inside and communicated to the airtight container 1 However, the initial gas volume χ ₁ can be measured accurately.

Further, the gas volume χ can be calculated by subtracting the initial gas volume χ ₁ from the residual gas volume χ ₂ according to the equation (3).

[0024]

[Equation 3]

In order to realize the above method, it is needless to say that the present invention comprises an airtight container 1 filled with a carbon dioxide absorbent. Further, the airtight container 1 is provided with a gas introducing means 4 for introducing a gas containing carbon dioxide gas from the test liquid container containing the test liquid.

Further, an absorbing agent introducing means 3 is provided, and the absorbing agent introducing means 3 fills the airtight container 1 with the carbon dioxide gas absorbent at the initial stage of the measurement, and of course, the initial gas volume χ ₁ before the measurement. It is possible to supply a predetermined amount υ ₁ of the carbon dioxide absorbent, and to find the residual gas volume χ ₂ a predetermined amount of the υ ₂ carbon dioxide absorbent.

Further, a pressure detecting means 5 is provided, which is provided with
Therefore, the carbon dioxide absorbent of the absorbent supply means 3
Internal pressure of the airtight container 1 before and after injection due to the initial gas
P₀₁, P ₁And internal pressure P due to residual gas₀₂, P₂Measure
can do.

The calculation for calculating the initial gas volume χ ₁ and the residual gas volume χ ₂ is performed by the calculating means 6.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gas volume measuring method and apparatus according to an embodiment of the present invention will be specifically described with reference to the drawings.
It is as follows.

FIG. 1 is a block diagram of a gas capacity measuring device according to an embodiment of the device of the present invention, FIG. 2 is a functional block diagram of control means for controlling this device, and FIG. 3 is a book using this device. It is a flowchart of the gas volume measuring method which concerns on one Example of the method of invention.

As shown in FIGS. 1 and 2, this apparatus comprises an airtight container 1 and an absorbent supply means 3 for supplying a carbon dioxide absorbent 2 made of, for example, sodium hydroxide to the airtight container 1.
A gas introducing means 4 for introducing a gas foamed from the test liquid into the airtight container 1, a pressure detecting means 5 for measuring the pressure in the airtight container 1, and bubbles generated from the test liquid, And a calculation means 6 for calculating the volume of the gas component excluding carbon dioxide. The control means 100 shown in FIGS.
Is an absorbent supply means 3, a gas introduction means 4, which will be described below.
The pressure detecting means 5, the calculating means 6 and the valve V at each work step
It is a control means including a valve control means 7 for instructing opening and closing of _{1 to} V ₄ , and is generally composed of a CPU and a program.

In FIG. 1 and FIG. 2, the absorbent supply means 3 uses the pump 33 from the absorbent container 31 for storing the carbon dioxide absorbent 2 in the airtight container 1 by using the pump 33.
Is configured to supply. Here, the pump 33
For this, a metering pump is used.

As shown in FIG. 1, the airtight container 1 is a communication pipe 1 which is led out from the upper end thereof and communicates with the pressure gauge 51.
1 and a purge pipe 13 led out from the lower end thereof and communicating with the absorbent container 31 and a purge pipe 14 branched from the communication pipe 11, and the purge pipes 13 and 14 are opened and closed respectively. Purge valves V ₃ and V ₄ are interposed.

Further, the gas introducing means 4 has a gas introducing passage 42 for communicating the test liquid container 41 with the bottom of the airtight container 1, and a gas introducing valve V ₁ for opening and closing the gas introducing passage 42.
The purge pipe 12 communicating with the absorbent container 31 is branched from a portion of the gas introduction path 42 on the airtight container 1 side of the gas introduction valve V _{1 and} the purge pipe 12 is provided.
A purge valve V ₂ for opening and closing is provided. The valve control means 7 shown in FIG. 2 controls the opening and closing of the gas introduction valve V ₁ and each of the purge valves V _{2 to} V ₄ .

Further, the vibrating means 8 comprises a vibration control means 83 for vibrating and controlling the test liquid container 41 containing the test liquid and an actuator 84 vibrated by the vibration control means 83.
As shown in FIG. 4, the airtight container 1 is initially empty,
When the control program is started, initialization is first performed (S1). In this initial setting, the valve control means 7
Closes the gas introduction valve V ₁ and each purge valve V _{2 to} V ₄ (S 2), and after the initial valve control is completed, the purge valve V ₄ is opened and the injection control that constitutes the absorbent supply means 3 is performed. The means 34 is activated to drive the pump 33,
As a result, the carbon dioxide absorbent (for example, NaOH) 2 is filled in the airtight container 1 (S3).

The above-mentioned filling step (S3) will be described in more detail. With the pump 33 being driven and the purge valve V ₄ being opened, the carbon dioxide absorbent (for example, NaOH) 2 is filled in the airtight container 1. Then, the purge valve V ₂ is then opened and the purge valve V ₄ is closed. Further, the purge valve V ₃ is opened, the purge valve V ₂ is closed, the pump 33 is finally stopped, and immediately after that, the purge valve V ₃ is closed. Therefore, as shown in FIG. 5, when the carbon dioxide absorbent is filled in the airtight container 1, all the valves V _{1 to} V ₄ are closed (S31 to S38).

Thus, while opening and closing each valve, carbon dioxide gas
By introducing the absorbent into the airtight container, each purge valve
Or gas remaining near the gas inlet valve, that is, the initial gas body
Product χ ₁Can be made smaller. When the above filling process is completed,
The pressure measuring means 52 is provided in the airtight container 1, and is a pressure gauge 5.
1, the pressure P in the airtight container 1 at this time_o1I Read. this
The result is stored in the memory 53 (S4).

When the measurement of the pressure in the airtight container 1 is completed as described above, the injection control means 34 actuates the pump 33 again, and as shown in FIG. 6, the carbon dioxide absorbent 2 in a predetermined amount ν ₁ is airtight. It is injected into the container 1 so that the pressure in the airtight container 1 is equal to or higher than a predetermined threshold value, and the injection amount υ ₁ at this time is stored in the memory 35 (S5).

After the introduction of the injection amount υ ₁ , the pressure P ₁ in the airtight container 1 is further measured by the pressure gauge 51 (S
6). When the measurement of the pressure P ₁ in the container is finished, the volume calculation means 61 of the calculation means 6 stores the injection amounts υ ₁ stored in the memory 53 of the above-mentioned _{Po 1} and P ₁ and the injection control means 34. Based on the above, the gas volume in the airtight container 1 and the space communicating with the airtight container 1, that is, the initial gas volume χ ₁ is calculated based on Equation 1 and stored in the memory 62 (S7).

Thus, the injection amount ν of the carbon dioxide absorbent 2
_When calculating the gas volume χ ₁ based on ₁ and the pressures P _o1 and P 1 in the airtight container 1 before and after the injection, it does not matter whether the gas is collected only in the closed tube 1. , Even if foaming remains in the airtight container 1, or even if gas remains near the gas introduction valve V ₁ and each of the purge valves V _{2 to} V ₄ ,
The total volume of the gas in the airtight container 1 and the air remaining in each of the valves V _{1 to} V ₄ is calculated as the gas volume χ ₁ .

When this calculation is completed, the valve control means 7 opens the purge valve V ₃ (S8), and when the purge valve V ₃ is opened by this, the injection amount υ ₁ injected as described above. Carbon dioxide absorbent 2 from the airtight container 1 to the purge pipe 13
It is discharged to the absorbent container 31 via (S9). Here, as shown in FIG. 6, the purge valve V ₃ may be opened and then closed again, or may be left open and proceed to the next step.

As described above, when the carbon dioxide absorbent 2 is discharged into the absorbent container 31, the vibration control means 83 is operated at the same time and the actuator 84 is operated to vibrate the test liquid container 41 for a predetermined time. When the vibration of the test liquid container 41 ends, the valve control means 7 opens the gas introduction valve V ₁ to introduce the gas contained in the test liquid container 41 into the airtight container 1 (S10 → S11 → S12 → S13). ).

The above steps are further repeated as follows. That is, first, as described above, the test liquid container 41 is vibrated, and the pressure in the test liquid container 41 at this time is measured by the pressure gauge 45. As a result, when the pressure is equal to or higher than the predetermined value, it is considered that carbon dioxide gas still remains in the test liquid container 41, the introduction valve V ₁ is opened, and the gas contained in the test liquid container 41 is opened. Is introduced into the airtight container 1, the introduction valve V ₁ is closed again after a lapse of a predetermined time, and the test liquid container 41 is vibrated again by the vibrating means 8.

When the pressure in the test liquid container 41 after the vibration is below a predetermined value, it is judged by the comparing means 86 that the residual amount of carbon dioxide gas in the test liquid container 41 is already negligible. Accordingly, as shown in FIG. 8, the valve control means 7 closes the gas introduction valve V ₁ and the purge valve V ₃ (S14).

It should be noted that, depending on the type of beverage, even if the process of vibration → gas introduction is repeated a considerable number of times, it may not fall below a predetermined threshold value. In such a case, the number of times vibration → gas introduction is repeated. When is above a predetermined value, the process proceeds to the next step.

In the above gas introducing step, the purge valve V ₃ is kept open, but the sample liquid container 41
It is also possible to close the purge valve V ₃ once before oscillating, and open the introduction valve V ₁ and at the same time open the purge valve V ₃ . As a result, the airtight container 1 is driven by the vibrating means 4.
It is possible to prevent the liquid from leaking.

When the gas introduction valve V ₁ and the purge valve V ₃ are closed as described above, the pressure measuring means 52 measures the pressure P _o2 in the airtight container 1 at that time (S15) and stores it in the memory 53. At the same time, the injection control means 34 operates the pump 33 to cause the carbon dioxide absorbent 2 to have a pressure P in the airtight container 1.
Inject into the airtight container 1 until _o2 exceeds a predetermined threshold,
The injection amount υ ₂ at this time is stored in the memory 35 (S16).

When the above-mentioned injection process is completed, the pressure is again set.
In the airtight container 1 at this time when the measuring means 52 is the pressure gauge 51
Pressure P₂Is measured (S17). Obtained this way
Internal pressure P₂Is stored in the memory 53 and
The product calculating means 61 uses the internal pressure P _o2, P₂And in the memory 35
Remembered infusion volume υ₂Read the injection volume υ₂Toko
These internal pressure P_o2And P₂Based on and according to Equation 2 above
Gas component excluding carbon dioxide in the airtight container 1 after introducing gas
Volume of residual gas volume χ₂Is calculated (S18),
It is stored in the memory 62.

Here, the injection amount of carbon dioxide absorbent 2₂When
Pressure P in airtight container 1 before and after injection _o2, P₂Based on
Initial gas volume χ₂Is calculated, so there is only one gas
It doesn't matter if they're together or not, so it's airtight
Even if bubbles remain in the container 1, or gas is introduced
Gas in the passage 42, the communication pipe 11, and a part of the purge pipes 13 and 14
Air remaining after the gas is introduced, even if
Is the residual gas volume χ₂Is calculated as

When the calculation of the residual gas volume χ ₂ is completed, χ ₁ and χ ₂ are read out from the memory 62 by the subtraction means 63, and the subtraction means 63 introduces the gas according to the above equation 3 based on these χ ₁ and χ _2. In the gas injected into the airtight container during the period, the volume of the gas component excluding the carbon dioxide gas, that is, the gas volume χ is calculated (S19).

The above χ ₁ and χ ₂ are the injection amounts υ ₁ and υ ₂ of the carbon dioxide absorbent ₂ and the pressure P in the airtight container 1 before and after the injection.
_o1, since P _1, P _o2, are calculated based on the P _2,
Since the bubbles including the bubbles attached to the inner surface of the airtight container 1 and the bubbles of the carbon dioxide absorbent 2 are accurately calculated, the calculated gas volume χ based on these is also accurately calculated. For example, as shown in the graph of FIG. 10, the error between the measured value and the gas amount is −0.03 to
It can be seen that extremely accurate measurement within the range of 0.05 ml can be performed.

In the above embodiment, sodium hydroxide is used as the carbon dioxide absorbent, but of course,
Instead of this, for example, calcium hydroxide, potassium hydroxide or the like may be used.

[0053]

As described above, according to the method of the present invention, a predetermined amount of carbon dioxide absorbent is supplied to the airtight container after introducing gas, and the predetermined amount and the amount of carbon dioxide in the airtight container before and after the supply are supplied. Since the residual gas volume is calculated based on the pressure and
The residual gas volume can be measured before the foaming in the airtight container is subsided, and the residual gas volume can be measured in a short time.

Further, even if air bubbles are dispersed in the airtight container and the space communicating with the airtight container or bubbles are attached to the inner surface of the airtight container, the airtight container including the dispersed air bubbles and the space communicating with the airtight container. Since it is possible to measure all of the residual gas volume inside, highly accurate measurement can be performed.

Moreover, since it is not necessary to use an antifoaming agent, the measurement can be carried out inexpensively and in a short time. In the method of the present invention, in particular, a predetermined amount of carbon dioxide absorbent is supplied to the airtight container before introducing gas, and the initial gas volume is calculated based on this predetermined amount and the pressure in the airtight container before and after the supply. When the initial gas volume is calculated from the residual gas volume to calculate the gas volume, the work of discharging the gas in the airtight container (air purging work) before introducing the gas becomes unnecessary, and the operability is improved. In addition, the measurement time can be further shortened.

Further, in this case, even if air bubbles are dispersed in the airtight container and the space communicating with the airtight container at the time of measuring the initial gas volume, or bubbles are adhered to the inner surface of the airtight container, the dispersed air bubbles are included. Since it is possible to measure all initial gas volumes in the airtight container and the space communicating with it,
High-precision measurement can be performed inexpensively without using an antifoaming agent.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus of the present invention.

FIG. 2 is a functional block diagram of control means of the device of the present invention.

FIG. 3 is a flow chart of the method of the present invention.

FIG. 4 is a configuration diagram of the device of the present invention when a carbon dioxide absorbent is injected.

FIG. 5 is a configuration diagram of the device of the present invention at the end of injection of carbon dioxide absorbent.

FIG. 6 is a configuration diagram of the device of the present invention when a carbon dioxide absorbent is injected.

FIG. 7 is a configuration diagram of the device of the present invention when gas is introduced.

FIG. 8 is a configuration diagram of the device of the present invention when gas introduction is completed.

FIG. 9 is a configuration diagram of the device of the present invention when a carbon dioxide absorbent is injected.

FIG. 10 is a graph showing measurement results by the method and apparatus of the present invention.

FIG. 11 is a configuration diagram of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Airtight container 2 Carbon dioxide absorbent 3 Absorbent supply means 4 Gas introduction device 5 Pressure detection means 6 Calculation means 11 Communication pipes 12, 13, 14 Purge pipe 31 Absorbent container 33 Pump 41 Test liquid container 42 Gas introduction path V1 Gas introduction valve V2, V3, V4 Purge valve P ₁ , P _o1 , P ₂ , P _o2 Internal pressure χ Gas volume χ ₁ , χ ₂ Gas volume υ ₁ , υ ₂ Injection amount

Claims (4)

(57) [Claims] 1. An airtight container filled with a carbon dioxide absorbent,
A gas containing carbon dioxide gas dissolved in the test liquid is introduced into the above airtight container through a carbon dioxide absorbent into the airtight container to remove the carbon dioxide gas, and then the airtight In a gas volume measuring method for measuring the volume of residual gas remaining in a container, a gas containing carbon dioxide gas is introduced into the airtight container, a predetermined amount of carbon dioxide absorbent is supplied to the airtight container, and the predetermined amount of carbon dioxide is supplied. A residual gas volume measuring method, characterized in that the residual gas volume in the airtight container is calculated based on the pressure in the airtight container before and after supplying the gas absorbent and the predetermined amount. 2. Before introducing the gas containing carbon dioxide into the airtight container, a predetermined amount of carbon dioxide absorbent is supplied into the airtight container, and before and after the supply of the predetermined amount of carbon dioxide absorbent. Calculate the initial gas volume in the airtight container before gas introduction based on the pressure in the airtight container and the predetermined amount, further subtract the initial gas volume from the residual gas volume,
The residual gas volume measuring method according to claim 1, wherein the gas volume is calculated. 3. An airtight container filled with a carbon dioxide absorbent,
A gas container after communicating with a test liquid container containing the test liquid and introducing a gas containing carbon dioxide gas dissolved in the test liquid into an airtight container via a carbon dioxide absorbent to remove the carbon dioxide gas In the gas volume measuring device for measuring the volume of residual gas remaining in the, the gas introducing means for introducing a gas containing carbon dioxide gas from the test liquid container containing the test liquid in the airtight container, and the gas introducing means After introducing the gas, an absorbent supply means for supplying a predetermined amount of carbon dioxide absorbent to the airtight container, and a pressure for detecting the pressure in the airtight container before and after the supply of the carbon dioxide absorbent by the absorbent supply means. A residual gas capacity measuring device comprising: a detection means; and a calculation means for calculating the residual gas volume in the airtight container based on the pressure in the airtight container and the predetermined amount. 4. The absorbent supply means supplies a predetermined amount of carbon dioxide absorbent to the airtight container before the gas is introduced by the gas introducing means, and the pressure detecting means supplies the predetermined amount of carbon dioxide absorbent. Before and after detecting the pressure in the airtight container, the calculating means calculates the initial gas volume based on the predetermined amount and the pressure in the airtight container, from the residual gas volume to the initial gas volume The gas volume measuring device according to claim 3, wherein the gas volume is calculated by subtracting.