JPH11183231A - Integrating flow meter and gas meter using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make accurately measurable the integrated rate of flow by converting the output of a measuring part by a conversion factor in a storage means corresponding to the type of a gas to be measured inputted by an inputting means. SOLUTION: Temperature sensors Ru and Rd on the upstream and downstream sides from a thermal flow rate sensor installed in a channel 10 are connected to a bridge circuit 22, and a heating coil Rh is heated by a power source 21. The distribution of temperature in the channel 10 is detected by the upstream and downstream temperature sensors Ru and Rd and is outputted from the bridge circuit 22 as detection output F. The detection output F is inputted to an A/D converting circuit 23, and a digitized signal X is supplied for a microcomputer 20. The microcomputer 20 processes signals and displays a converted measured value on an instantaneous flow rate display 24a and integrated flow rate display 24b. In addition, a switch 25 for inputting the type of gas flowing through the channel 10 is connected to the microcomputer 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrating flow meter having a thermal flow sensor in a measuring section and measuring an integrated flow rate of a measuring gas flowing through the measuring section, and a gas meter using the same.

[0002]

2. Description of the Related Art A thermal type flow sensor measures a flow rate of a fluid by detecting that a temperature distribution given to the fluid changes according to the flow of the fluid. A general thermal flow sensor has a heating wire, an upstream temperature sensor and a downstream temperature sensor, heats the fluid to a predetermined temperature by the heating wire, and calculates a difference between the detected temperatures of the upstream and downstream temperature sensors. Measure the flow rate.

FIG. 6 is a diagram for explaining the operation of such a thermal type flow sensor, and FIG. 6 (1) is a circuit diagram thereof. The heating wire Rh, the upstream temperature sensor Ru, and the downstream temperature sensor Rd are arranged in the flow path 10 through which the metered gas flows.
The upstream temperature sensor Ru and the downstream temperature sensor Rd and the resistors R1 and R2 form a bridge circuit 52, and a node n
s and nr are connected to an amplifier 50.

The bridge circuit 52 includes an upstream temperature sensor R
Using the fact that the resistance values of u and the downstream temperature sensor Rd change with temperature, the change in the resistance value is input to the amplifier 50 as a change in voltage.

The heating wire Rh generates heat when a predetermined voltage V0 is applied, and generates a temperature distribution around the heating wire Rh in the metered gas. When there is no flow in the metered gas, the temperature distribution of the metered gas is substantially symmetric about the hot wire Rh, and the detected temperatures of the upstream temperature sensor Ru and the downstream temperature sensor Rd are substantially equal.

On the other hand, if the gas in the flow passage 10 flows in the direction of the arrow, the temperature distribution moves downstream accordingly. Therefore, the temperature detected by the upstream temperature sensor Ru is lower than the temperature detected by the downstream temperature sensor Rd. This temperature difference changes according to the flow rate of the metered gas.

FIG. 6B shows the relationship between the flow rate Q of the metered gas in the flow path 10 and the output F of the amplifier 50. FIG.
(2) As shown, the output F of the amplifier 50 does not change linearly with the flow rate Q. This is because resistance values such as platinum thin film resistors used as the upstream and downstream temperature sensors Ru and Rd do not have linear temperature characteristics.

Therefore, if the output F of the amplifier 50 is used as the measured value of the flow rate as it is, the change of the measured value becomes non-linear. Therefore, the flow rate Q and the measured value are corrected so as to be a straight line by a linearize curve described later. FIG.
(3) shows the relationship between the measured value Z and the flow rate Q after performing the linearization correction on the output F. Linearization correction can be performed by inputting the output F of the amplifier 50 to an amplifier having characteristics opposite to those of FIG.

[0009]

As described above, the thermal type flow sensor performs the linearization correction to obtain the flow rate Q.
And the measurement value Z can be made linear. However, the temperature distribution of the metered gas given by the hot wire Rh is
It depends on the type or composition of the metered gas flowing through the flow path. This is because the thermal conductivity of the measuring gas differs depending on the type or composition of the measuring gas. Therefore, the detection output of the thermal flow sensor differs depending on the type or composition of the gas to be measured.

[0010] The conventional integrating flow meter performs linearization correction specific to the measured gas depending on the type of the measured gas and the like.
A linear measurement was obtained for the flow rate. For example, there are types of city gas such as 6A and 13A, and the compositions of methane, nitrogen and the like are different. For this reason, a conventional integrating flow meter has been used which has been subjected to linearization correction according to the gas to be measured, such as for gas type α or gas type β.

FIG. 7 is an explanatory diagram in the case where another type of gas is passed through the integrating flow meter for a specific gas. For example, a solid line indicates a case where the gas type α is flown, and a dotted line indicates a case where the gas type β is flown. FIG. 7A shows the relationship between the flow rate Q and the detection output F, and FIG. 7B shows the relationship between the flow rate Q and the measured value Z.
As described above, the detection output F and the measured value Z differ depending on the gas type.

For this reason, for example, when an integrating flow meter for gas type α is used for measuring gas type β, an accurate measured value cannot be shown. Further, for example, even within the same gas type, the types and composition ratios of the component gases contained therein vary within an allowable range. Therefore, even if the gas type α is measured by the integrating flow meter for the gas type α, an accurate measured value is not always obtained due to the fluctuation of the composition ratio.

Therefore, the present invention provides an integrated flow meter capable of accurately measuring an integrated flow rate with a conversion coefficient corresponding to the type of the measured gas simply by inputting the type of the measured gas, and a gas meter using the same. Aim.

Further, the present invention provides an integrated flow meter capable of accurately measuring an integrated flow rate by inputting the type and composition ratio of a component gas of a measured gas, calculating a conversion coefficient suitable for the measured gas, and measuring the integrated flow rate. It is an object to provide a gas meter using the same.

[0015]

The object of the present invention is to provide an integrating flow meter having a measuring section for measuring the flow rate of a measuring gas and a converting section for converting the output of the measuring section into an integrated flow rate. Including storage means storing a plurality of conversion coefficients corresponding to the type, and input means for inputting the type of metered gas flowing through the metering unit, the conversion unit, the type of metered gas input by the input means This is achieved by providing an integrated flow meter and a gas meter using the same, wherein the output of the measuring section is converted by a corresponding conversion coefficient in the storage means.

According to the present invention, when the type of the measured gas is input, the measurement is performed with the conversion coefficient corresponding to the type of the measured gas. A gas meter using the same can be provided.

The above object is also achieved in an integrating flow meter having a measuring section for measuring a flow rate of a measuring gas, and a converting section for converting an output of the measuring section into an integrated flow rate, the component corresponding to the component of the measuring gas. A storage unit storing a plurality of conversion coefficients, and an input unit for inputting a component and a component ratio of a measurement gas flowing through the measurement unit, wherein the conversion unit includes a component and a component of the measurement gas input by the input unit. This is achieved by providing an integrating flow meter and a gas meter using the same, wherein the output of the measuring section is converted by a ratio and a conversion coefficient corresponding to the conversion coefficient in the storage means. .

According to the present invention, by inputting the components and the component ratios of the gas to be measured, a conversion coefficient corresponding to the composition of the gas to be measured is calculated, and the integrated flow rate of the gas to be measured is measured using the conversion coefficient. In addition, it is possible to provide an integrating flow meter capable of performing more accurate measurement even if the composition of the measurement gas varies, and a gas meter using the same.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, such embodiments do not limit the technical scope of the present invention.

FIG. 1 is a circuit configuration diagram of a gas meter according to a first embodiment of the present invention. Upstream and downstream temperature sensors R of the thermal flow sensor mounted in the flow path 10
u and Rd are connected to the bridge circuit 22, and the heating wire Rh is heated by the power supply 21. The temperature distribution in the channel 10 is
The temperature is detected by the upstream and downstream temperature sensors Ru and Rd, and is output from the bridge circuit 22 as a detection output F.

The detection output F is input to the A / D conversion circuit 23, and the digitized signal X is
0 is supplied. The microcomputer 20 performs signal processing described later, and displays the converted measured value on the instantaneous flow rate display 24a and the integrated flow rate display 24b.

The microcomputer 20 has a flow path 10
Switch 25 for inputting the type of gas flowing through
Is connected. Gas types include city gas 6A and 13A
, Natural gas, naphtha gas, etc. 6A of the city gas is a gas obtained by mixing nitrogen, oxygen and the like so that the calorific value becomes 7000 kcal / m ³ , and 13A is methane, heavy hydrocarbon and the like so that the calorific value becomes 11000 kcal / m ³ Is mixed gas.

As the input switch 25, for example, a dip switch, a rotary switch, a keyboard, or the like is used, and a signal indicating the type of gas to be measured is given to the microcomputer 20.

Next, each circuit in the microcomputer 20 will be described. The linearization circuit 201 performs the above-described linearization correction on the output X of the A / D conversion circuit 23, and outputs a linearized output Y. Linearization coefficient table 2
Reference numeral 03 includes, for example, a RAM or the like, and stores a linearization coefficient corresponding to the type of gas. The contents of the linearization coefficient table 203 are, specifically, data of a linearization curve shown in FIG. Further, the selection circuit 202 selects a linearization coefficient corresponding to the type of gas input by the input switch 25 from the linearization coefficient table 203 and supplies the selected linearization coefficient to the linearization circuit 201.

The flow rate conversion circuit 204 converts the linearized output Y into a flow rate measurement value Z according to a conversion coefficient specific to the type of gas. The conversion coefficient table 206 is composed of, for example, a RAM or the like, and stores a conversion coefficient corresponding to the type of gas. Further, the selection circuit 205 selects a conversion coefficient corresponding to the type of gas from the conversion coefficient table 206 and supplies the conversion coefficient to the flow rate conversion circuit 204, similarly to the selection circuit 202. With these circuits, the output X of the A / D conversion circuit 23 is converted into a measured value Z of the flow rate, and an accurate flow rate corresponding to the type of gas to be measured is displayed on the instantaneous flow rate display 24a. Also, the weighing value Z
Are integrated by the integrating circuit 210 and displayed on the integrated flow rate display 24a. Note that the flow rate conversion circuit 204 is replaced with the linearization circuit 2
When the number is divided into 01, the storage capacity for storing data corresponding to the type of gas can be saved, and it is easy to cope with a plurality of input signal ranges of the flow rate display 24.

FIG. 2 shows a configuration of a gas meter according to a second embodiment of the present invention. The description of the same parts as those of the gas meter of FIG. 1 will be omitted, and different parts will be described. The input switch 25 of the present embodiment inputs a component and a component ratio of a gas to be measured. As described above, the city gases 6A, 13A and the like are mixed with a specified ratio of nitrogen, methane, and the like, but the component ratio fluctuates within an allowable range. Since the fluctuation of the component ratio fluctuates the thermal conductivity of the metered gas, simply the city gas 6A,
Even when a linearization coefficient and a conversion coefficient corresponding to the type of gas such as 13A are used, an accurate measurement value may not be obtained.

Therefore, in the present embodiment, the linearization coefficient table 203 and the conversion coefficient table 206 store the linearization coefficient and the conversion coefficient for each component gas such as nitrogen and methane. Then, the calculation circuits 207 and 208 read the linearization coefficient and the conversion coefficient of each component from the linearization coefficient table 203 and the conversion coefficient table 206 based on the components and the component ratio of the measurement gas input from the input switch 25, and The linearization coefficient and the conversion coefficient according to the composition of are calculated.

The linearization circuit 201 and the flow rate conversion circuit 204 perform linearization and flow rate conversion using a linearization coefficient and a conversion coefficient according to the composition of the gas to be measured, and output the measurement value Z to the instantaneous flow rate display 24a. . Thereby, an accurate measurement value can be obtained even if the component of the gas to be measured fluctuates.

FIG. 3 is an example of a linearization coefficient table according to the present embodiment. FIG. 3A shows the contents of the linearization coefficient table 203 according to the first embodiment. In the linearization coefficient table 203 of this example, the city gas 6
The linearization coefficient data of B, 12A, 13A, 6A, natural gas, and naphtha gas is stored. For example, in the case of the city gas 6B, the coordinates are (X11, Y11), (X12, Y12), and this value is the coordinate value of the linearize curve in FIG.

FIG. 3B shows the contents of the linearization coefficient table 203 according to the second embodiment of the present invention. In this example,
The linearization coefficient data of a single gas such as carbon monoxide and hydrogen is stored. The linearization coefficient data of the single gas is converted into a linearization coefficient corresponding to the composition of the metered gas by the calculation circuit 207 shown in FIG.

On the other hand, the structure of the conversion coefficient table 206 is
It has the same structure as the linearization coefficient table 203, and stores conversion coefficient data for each gas type or single gas.

Further, in the first and second embodiments, the linearization coefficient and the conversion coefficient are used separately in order to improve the conversion accuracy. Can also. Instead of storing each data in a table, the linearization circuit 201 calculates a linearized output Yn from the output Xn of the A / D conversion circuit 23 using an approximate function of, for example, Yn = F (Xn). You can also.

FIG. 4 is an explanatory diagram of the linearization coefficient according to the present embodiment. FIG. 4A shows the relationship between the flow rate Q of the metered gas flowing through the flow path 10 and the output X of the A / D conversion circuit 23. As described above, the output X shows non-linearity with respect to the flow rate Q.

FIG. 4B shows the input / output characteristics of the linearization circuit 201, that is, the linearization curve. The linearize curve has the opposite characteristic of FIG. 4A, and is created from the data stored in the linearization coefficient table as described above, or calculated by an approximation function. FIG. 4C shows the relationship between the flow rate Q corrected by the linearization curve and the linearized output Y.

FIG. 5 is an explanatory diagram of the flow rate conversion coefficient of the present embodiment. FIG. 5A shows input / output characteristics of the flow rate conversion circuit 204. Although the output Y of the linearization circuit is linearized,
Depending on the type or composition of the gas, the value may not always correspond to the flow rate displayed on the instantaneous flow rate display 24a or the like. In this case, the linearized output Y is converted by the flow rate conversion circuit 204 having the characteristic of FIG. 5A, and the linearized output Y is measured as shown in FIG. The value Z is output.

[0036]

As described above, according to the present invention, when the type of the gas to be measured is input, the measurement is performed with the conversion coefficient corresponding to the type of the gas to be measured. It is possible to provide a compatible integrating flow meter and a gas meter using the same.

According to the present invention, when the components and the component ratio of the measuring gas are input, the conversion coefficient corresponding to the composition of the measuring gas is calculated, and the conversion coefficient is converted into the flow rate of the measuring gas using the conversion coefficient. In addition, it is possible to provide an integrating flow meter capable of performing more accurate measurement even if the composition of the measurement gas varies, and a gas meter using the same.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a gas meter according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a gas meter according to a second embodiment of the present invention.

FIG. 3 is a linearization coefficient table according to the embodiment.

FIG. 4 is an explanatory diagram of a linearization coefficient.

FIG. 5 is an explanatory diagram of a flow rate conversion coefficient.

FIG. 6 is an explanatory diagram of a thermal flow sensor.

FIG. 7 is an explanatory diagram in which the detection output differs depending on the type of gas.

[Explanation of symbols]

 Reference Signs List 20 microcomputer 22 bridge circuit 23 A / D conversion circuit 24a instantaneous flow rate display 24b integrated flow rate display 25 input switch 201 linearization circuit 203 linearization coefficient table 204 flow rate conversion circuit 206 conversion factor table 210 integration circuit

Claims (6)

[Claims] 1. An integrating flow meter having a measuring section for measuring a flow rate of a measuring gas and a converting section for converting an output of the measuring section into an integrated flow rate, wherein a plurality of conversion coefficients corresponding to the type of the measuring gas are determined. Storing means for storing, and input means for inputting a type of a measuring gas flowing through the measuring section, wherein the converting section has a conversion coefficient in the storing means corresponding to the type of the measuring gas input by the input means. Wherein the output of the weighing unit is converted. 2. The method according to claim 1, wherein the storage means stores a first table storing a plurality of linearization coefficients corresponding to the type of the measurement gas, and a plurality of flow rate conversion coefficients corresponding to the type of the measurement gas. A conversion table that converts the output of the measuring section with the conversion coefficient having the linearization coefficient and the flow rate conversion coefficient. 3. An integrating flow meter having a measuring section for measuring a flow rate of a measuring gas and a converting section for converting an output of the measuring section into an integrated flow rate, wherein a plurality of conversion coefficients corresponding to the components of the measuring gas are determined. A storage means for storing, and an input means for inputting a component and a component ratio of the measuring gas flowing through the measuring section, wherein the converting section corresponds to the component and the component ratio of the measuring gas input by the input means and corresponding thereto. An output of the weighing unit is converted by a calculated conversion coefficient calculated based on the conversion coefficient stored in the storage unit. 4. The storage device according to claim 3, wherein the storage means stores a first table storing a plurality of linearization coefficients corresponding to the components of the metered gas, and a plurality of flow rate conversion coefficients corresponding to the components of the gas. A second table stored therein, wherein the conversion unit converts the output of the measuring unit with the conversion coefficient having the linearization coefficient and the flow rate conversion coefficient. 5. The integrating flow meter according to claim 1, wherein the measuring unit measures a flow rate of the measuring gas by a thermal flow sensor. 6. A gas meter comprising the integrating flow meter according to claim 1.