JP5525374B2 - Flow rate standard and flow rate calibration method using the same - Google Patents

Description

  The present invention relates to a flow rate standard used when calibrating a flow rate value of a gas flow meter or a flow rate controller and a flow rate calibration method using the same.

  Due to the increasing handling of gas with a small flow rate in fields such as the semiconductor industry, environmental measurement, and chemical analysis, a flow meter that measures a micro flow rate and a flow rate controller that controls the micro flow rate are becoming more and more used. Accordingly, there is a need for a calibration device that can accurately calibrate a minute flow rate.

  Conventionally, calibration of a flow meter is known by a method using a reference volume tube or a method using a soap film, but these methods cannot accurately calibrate a minute flow rate.

  As a method of calibrating a minute flow rate with a flow rate of less than 5 mL / min (dry air), a mass method described in Non-Patent Document 1 or the like is known. In the mass method, gas is introduced into the tank at a constant flow rate, and the flow rate is obtained from the change in the mass of the tank. However, when a minute flow rate is targeted, it takes a long time to greatly change the mass of the tank. Therefore, the time required for calibration is long.

Transactions of the Japan Society of Mechanical Engineers (Part B), Vol. 65, No. 630 (1999-2), p. 677-683

  An object of the present invention is to provide a flow rate standard capable of accurately calibrating a flow meter for measuring a minute flow rate in a short time. It is another object of the present invention to provide a method for calibrating a flow meter using this flow standard.

  The present inventors have conceived that the pressure source and the flow rate standard are shut off after the compressed gas is filled into the flow rate standard equipped with the flow rate controller from the pressure source. As a result, it has been found that a gas flow with a minute flow rate can be accurately generated from the upstream side to the downstream side of the flow meter to be tested in the flow rate standard that is blocked from the pressure source. This minute flow rate can be accurately calculated by multiplying the flow rate of the entire flow rate standard generated by the flow rate controller by the ratio of the volume on the upstream side of the flow meter and the volume of the overall flow rate standard. The present invention has been completed by finding out that it can be used for calibration of a flow meter for a flow rate.

  The present invention for achieving the above object is described below.

[1]
A first flow path pipe having one end connected to a pressure source and a flow controller connected to the other end;
A second flow path pipe having one end connected to the pressure source, the other end connected to the first flow path pipe, and a connection port in which the flow meter to be tested is connected in series in the flow path;
The supply of gas from the pressure source to the first flow path pipe and the supply of gas from the pressure source to the second flow path pipe are blocked, and the first flow path pipe and the second flow path pipe are A blocking means for separating on the upstream side of the connection port;
A flow rate standard characterized by comprising:

[2]
A first flow path pipe having one end connected to a pressure source and a flow controller connected to the other end;
A second flow path pipe having one end connected to the pressure source, the other end connected to the first flow path pipe, and a connection port in which the flow meter to be tested is connected in series in the flow path;
The supply of gas from the pressure source to the first flow path pipe and the supply of gas from the pressure source to the second flow path pipe are blocked, and the first flow path pipe and the second flow path pipe are A blocking means for separating on the upstream side of the connection port;
Means for changing the internal volume of the flow standard on the downstream side of the connection port;
A flow rate standard characterized by comprising:

[3]
Using the flow rate standard described in [1] or [2],
After gas is supplied from a pressure source into the flow rate standard and the flow rate standard is pressure balanced,
Shut off the gas supply from the pressure source by the shut-off means;
An internal volume c downstream of the blocking means of the flow rate standard, and an internal volume a in the second flow path pipe between the blocking means of the flow rate standard and the connection port;
From the flow rate X1 of the gas discharged from the flow rate controller outside the flow rate standard,
Following formula (1)
X2 = X1 × a / c (1)
The flow rate calibration method for pricing the flow rate X2 flowing through the flow meter to be tested by the above.

  According to the flow rate calibration method performed using the flow rate standard of the present invention (hereinafter also referred to as “the present flow rate standard”), the calibration of a minute flow rate can be performed accurately and in an extremely short time.

FIG. 1 is a configuration diagram of the present flow standard according to the first embodiment. FIG. 2 is a configuration diagram of the present flow standard according to the second embodiment. FIG. 3 is a configuration diagram showing another configuration example of the flow rate standard according to the first embodiment.

  Hereinafter, the present invention will be described in detail with reference to two embodiments. In this description, all gas volumes are described as volumes in a standard state (0 ° C., 1 atm).

<First Embodiment>
The first embodiment of the present invention is a flow standard that calibrates a flow meter to be tested by supplying gas into a flow standard having a fixed internal volume. First, the configuration of the flow rate standard device according to the first embodiment of the present invention will be described with reference to FIG. 1, and the operation of this flow rate standard device will be described.

(1) Configuration of Flow Rate Standard of First Embodiment FIG. 1 is a configuration diagram of a flow rate standard according to the first embodiment. In FIG. 1, reference numeral 100 denotes a flow standard (excluding the flow meter 40 which is a test object). On the upstream side of the standard device 100, a pressure source 11, a regulator 15, and a pressure gauge 19 are sequentially connected. In FIG. 1, reference numeral 11 denotes a pressure source provided on the upstream side, and is connected to the inlet side of the regulator 15 by a pipe 13. One end of a pipe 17 is connected to the outlet side of the regulator 15. The other end of the pipe 17 is connected to a pressure gauge 19. One end of a pipe 21 is connected to the pressure gauge 19. The other end side of the pipe 21 branches into two and is connected in parallel to the inlet side of the first on-off valve 23 and the inlet side of the second on-off valve 31.

  One end of the first flow path pipe 25 is connected to the outlet side of the first opening / closing valve 23. The other end side of the first flow path pipe 25 is connected to the intake side of the flow rate controller 27. The exhaust side of the flow controller 27 is open.

  One end of the second flow path pipe 33 a is connected to the outlet side of the second opening / closing valve 31. The other end side of the second gas supply pipe 33a constitutes a connection port 35a. The connection port 35a is connected to the inlet side of the flow meter 40 to be tested. The outlet side of the flow meter 40 is connected to a connection port 35b that is one end of the second flow path pipe 33b. The other end of the second flow path pipe 33 b is connected to the flow path of the first flow path pipe 25.

  The first open / close valve is means for blocking the supply of gas from the pressure source to the first flow path pipe. The second open / close valve is a means for blocking the supply of gas from the pressure source to the second flow path pipe.

(2) Operation of Flow Rate Standard of First Embodiment First, the flow meter 40 to be tested is airtightly attached to the connection ports 35a and 35b. Next, the first on-off valve 23 and the second on-off valve 31 are opened, and compressed gas is supplied from the pressure source 11 into the flow rate standard 100. The compressed gas supplied from the pressure source 11 is sent to the regulator 15 through the pipe 13 and regulated to a constant pressure. The compressed gas sent from the regulator 15 is sent to the pipe 21 via the pipe 17 and the pressure gauge 19. As described above, the first on-off valve 23 and the second on-off valve 31 are open so that compressed gas can flow. The compressed gas is sent to the first flow path pipe 25 and the second flow path pipes 33a and 33b via the first open / close valve 23 and the second open / close valve 31. The compressed gas sent to the first flow path pipe 25 and the second flow path pipes 33 a and 33 b is discharged by the flow rate controller 27 to the outside of the flow rate standard device 100 at a constant flow rate.

  When the pressure in the flow rate standard device reaches a predetermined pressure (pressure regulated by the regulator 15), the first opening / closing valve 23 and the second opening / closing valve 31 are closed substantially simultaneously. The term “substantially simultaneous” refers to an interval within 10 seconds, preferably within 5 seconds, and more preferably within 1 second.

Even after the first opening / closing valve 23 and the second opening / closing valve 31 are closed, the compressed gas in the flow rate standard device 100 is discharged to the outside of the flow rate standard device 100 through the flow rate controller 27 at a constant flow rate. The movement of gas in the flow rate standard 100 at this time is
The second gas supply pipe 33a portion (between the arrows A in the figure, the upstream side of the flow meter 40, that is, between the flow channels of the second opening / closing valve 31 and the flow meter 40, in the flow rate standard 100. Hereinafter, this part is also referred to as “A part”, and this internal volume is a).
The second gas supply pipe 33b portion and the first gas supply pipe 25 (between the arrows B in the figure, below the flow meter 40, that is, between the flow path between the flow meter 40 and the first gas supply pipe 25, hereinafter this The part is also referred to as “B part”, and this internal volume is b).
This will be explained separately.

  The internal volume downstream of the first opening / closing valve 23 and the second opening / closing valve 31 is c. That is, a + b = c.

When the gas in the main flow standard 100 is discharged out of the main flow standard 100 by the flow controller 27, the gas in the main flow standard 100 moves from the upstream side to the downstream side. That is, in FIG. 1, the gas in the A portion moves to the B portion. The flow meter 40 indicates the flow rate X2 by the movement of the gas. The flow rate X2 of the flow meter 40 to be tested is unknown. On the other hand, the flow rate X1 at which the gas in the flow rate standard 100 is discharged out of the flow rate standard 100 by the flow rate controller 27 is known. Accordingly, the flow rate X2 can be obtained by multiplying the flow rate X1 by the volume ratio a / c. That is, the following formula (1)
X2 = X1 × a / c (1)
It can ask for.

  The flow rate X1 is known and is a flow rate that can be accurately calibrated by a conventional calibration method (for example, 5 mL / min. Or more). By multiplying the volume ratio a / c by using this X1 as a reference, it is possible to price a minute flow rate X2 of, for example, less than 5 mL / min.

  By changing the flow rate of the flow rate controller 27, a plurality of minute flow rates can be priced.

  When the internal volume of the flow meter 40 to be tested has a non-negligible internal volume with respect to a and b, the internal volumes before and after the measurement unit of the flow meter 40 are included in a and b, respectively. Specifically, when the flow meter 40 is a differential pressure flow meter, the front volume of the differential pressure generation site is calculated as a and the rear volume is calculated as b.

Second Embodiment
The second embodiment of the present invention is a flow standard that calibrates a flow meter to be tested by supplying a gas into a flow standard that can change the internal volume. First, the configuration of the flow rate standard device according to the second embodiment of the present invention will be described with reference to FIG. 2, and the operation of this flow rate standard device will be described.

(1) Configuration of Flow Rate Standard of Second Embodiment FIG. 2 is a configuration diagram of a flow rate standard according to the second embodiment. In FIG. 2, reference numeral 200 denotes a flow standard (excluding the flow meter 40 which is a test target). An internal volume changing means 26 is connected to the first flow path pipe 25 of the standard device 200. The other parts are the same as those of the flow rate standard 100 according to the first embodiment. Therefore, the same components are denoted by the same reference numerals and description thereof is omitted.

(2) Operation of Flow Rate Standard of Second Embodiment Although it is the same as the operation of the first embodiment, the internal volume changing means 26 is included in the B portion.
Thereby, the volume ratio a / c can be changed freely. Therefore, it is possible to price the flow in a wide range.

<Blocking means>
A known opening / closing valve can be used as the blocking means. For example, an electromagnetic valve or a pneumatic valve can be used.

  When two on-off valves are used as the shut-off means, the first on-off valve and the second on-off valve are configured to be closed substantially simultaneously. Here, “substantially simultaneous” refers to the extent that no pressure difference is generated between the portion A and the portion B in FIG. 1 when the valve is closed. Specifically, the interval is within 10 seconds, preferably within 5 seconds, and more preferably within 1 second.

  The first opening / closing valve and the second opening / closing valve may be integrally formed. For example, the rotary valve 24 shown in FIG. 3 can be used. According to this rotary valve, the supply of gas from the pressure source to the first flow path pipe and the supply of gas from the pressure source to the second flow path pipe can be blocked almost simultaneously.

<Pressure source, regulator>
Examples of the pressure source include a compressor and a gas cylinder. The pressure of the compressed gas introduced into the flow rate standard is adjusted by a regulator or the like. The pressure of the compressed gas introduced into the flow rate standard is not more than the upper limit pressure of the flow rate controller 27. Examples of the compressed gas introduced into the flow rate standard include air and inert gas.

<Connection port>
The connection port 27 may have any structure as long as it is airtightly connected to the flow meter 40 to be tested.

<First channel pipe, second channel pipe, other piping>
The first channel pipe, the second channel pipe, and other pipes need to be made of a material whose internal volume does not easily change. The material is preferably stainless steel or brass.

<Flow controller>
The flow controller may be any one that can accurately control the flow rate. Such a flow controller may be a commercially available one. A flow controller or sonic nozzle calibrated according to national standards is preferred. Moreover, it is preferable that the flow volume controller has such a small internal volume that it can be substantially ignored. When the internal volume cannot be substantially ignored, the internal volume is included in b.

<Internal volume changing means>
The internal volume changing means is connected to the first flow path pipe and is used to change the internal volume b of the B portion. The internal volume changing means is composed of a tank or the like that is airtight and highly rigid and does not change its internal volume. As such an internal volume changing means, a method of detaching a volume tube having a known internal volume is exemplified. Furthermore, a plurality of internal volume changing means may be connected to the first flow path pipe via respective valves, and any internal volume changing means may be selectively used.

<Others>
An exhaust valve may be provided in the first channel pipe. By providing the exhaust valve, the inside of the flow standard can be immediately returned to normal pressure.

100, 200, 300 ... Flow rate standard 11 ... Pressure source 13, 17 ... Piping 15 ... Regulator 19 ... Pressure gauge 23 ... First on-off valve 24 ... Rotary valve 25 ... 1st channel pipe 26 ... Internal volume changing means 27 ... Flow rate controller 31 ... 2nd on-off valve 33a, 33b ... 2nd channel pipe 35a, 35b ... Connection port 40 ···Flowmeter

Claims (3)

A first flow path pipe having one end connected to a pressure source and a flow controller connected to the other end;
A second flow path pipe having one end connected to the pressure source, the other end connected to the first flow path pipe, and a connection port in which the flow meter to be tested is connected in series in the flow path;
The supply of gas from the pressure source to the first flow path pipe and the supply of gas from the pressure source to the second flow path pipe are blocked, and the first flow path pipe and the second flow path pipe are A blocking means for separating on the upstream side of the connection port;
A flow rate standard characterized by comprising: A first flow path pipe having one end connected to a pressure source and a flow controller connected to the other end;
A second flow path pipe having one end connected to the pressure source, the other end connected to the first flow path pipe, and a connection port in which the flow meter to be tested is connected in series in the flow path;
The supply of gas from the pressure source to the first flow path pipe and the supply of gas from the pressure source to the second flow path pipe are blocked, and the first flow path pipe and the second flow path pipe are A blocking means for separating on the upstream side of the connection port;
Means for changing the internal volume of the flow standard on the downstream side of the connection port;
A flow rate standard characterized by comprising: Using the flow standard according to claim 1 or 2,
After gas is supplied from the pressure source into the flow standard and the flow standard is brought into pressure equilibrium,
Shut off the gas supply from the pressure source by the shut-off means;
An internal volume c downstream of the blocking means of the flow rate standard, and an internal volume a in the second flow path pipe between the blocking means of the flow rate standard and the connection port;
From the flow rate X1 of the gas discharged from the flow rate controller outside the flow rate standard,
Following formula (1)
X2 = X1 × a / c (1)
A flow rate calibration method for pricing the flow rate X2 of the flow meter to be tested.

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