JP3719802B2 - Multipoint flow meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a multipoint measurement type flow meter that measures flow velocity values at a plurality of positions with a plurality of thermal flow sensors, and is capable of highly accurate measurement even in an environment where the temperature, pressure, and concentration of a fluid change. The present invention relates to a point measurement type flow meter.
[0002]
[Prior art]
An instrument that measures the flow rate of fluid flowing through pipes and grooves is called a flow meter, and it uses this measurement method to determine the average flow velocity in a direct measurement method that divides the fluid into constant volumes. And the indirect measurement method to obtain the flow rate by multiplying the pipe cross-sectional area. The thermal flow sensor is one of measuring instruments used in the indirect measurement method, and inserts a heating body into a fluid flow and measures the flow velocity and flow rate by using the cooling. When accuracy is required, sensors are used in multiple locations. When measuring the flow rate in a place where the length of the straight pipe part is only several times less than the diameter of the pipe, the measurement accuracy can be obtained by performing multipoint measurement taking into account the difference in flow velocity depending on the position and time. Therefore, a multipoint measurement type flow meter in which a plurality of thermal flow sensors are combined is used.
[0003]
A conventional multipoint flow meter will be described with reference to FIGS.
In FIG. 3, the multipoint measurement type flow meter 1 ′ has a plurality of thermal flow sensors 12 ′ attached to one surface of the substrate 11 ′ and a temperature sensor 13 ′ attached to the back surface of the substrate 11 ′. And when using, as shown in FIG. 4, it was inserted at right angles to the direction of the flow of a pipe line.
[0004]
This flow meter has an advantage that it has a wide flow measurement range over two digits, responds in a short time on the order of ms, has low pressure loss, and is easy to insert into a pipe. However, since the measured value of the thermal flow sensor is easily affected by changes in the temperature, pressure, and concentration of the fluid, it has the disadvantage that the measurement accuracy of the flowmeter decreases, especially in an environment where these parameters change greatly. . Therefore, conventionally, the temperature change is corrected by the temperature sensor, but the change in pressure and concentration is not taken into consideration. In addition, it is known that the performance of the thermal flow sensor changes with use due to changes in the properties of the heater over time, adhesion of dust, and the like. In the case of long-term use, it is necessary to correct this change with time. However, it is difficult to correct without change, and maintenance is required.
[0005]
[Problems to be solved by the invention]
Conventional multi-point measurement type flowmeters cannot be used alone as accuracy deteriorates when there is a change in the pressure or concentration of the fluid. A pressure gauge and concentration meter are installed separately from the flowmeter. It was necessary to perform correction calculation of the flow meter output value based on those output values. For this reason, a place for installing a pressure gauge and a concentration meter is required, and a computer for performing a complicated correction calculation is also required. Especially when the installation place of the multi-point measurement type flow meter is narrow, it is necessary to install a pressure gauge and a concentration meter at a distant place, so correct correction cannot be performed and the accuracy of the flow meter can be sufficiently improved. It was difficult.
Furthermore, there has been a demand for a function of correcting the change with time of the thermal flow sensor without maintenance.
[0006]
In view of these problems, the object of the present invention can be used in a place where a change in fluid pressure or concentration occurs, and can output a flow rate value converted with respect to pressure or concentration. It is also necessary to realize a multipoint measurement type flow meter that is not necessary and that can correct a change with time without maintenance.
[0007]
[Means for Solving the Problems]
The present invention provides a multipoint measurement type flow meter that measures flow velocity values at a plurality of positions with a plurality of thermal flow sensors, and includes means for measuring the temperature, pressure, or concentration of the fluid, and the measured values of the thermal flow sensor are , have a correction means for correcting the measured value of the pressure or concentration, the resistance value of the resistance portion of the thermal type flow sensor with obtaining temperature information of the fluid by measuring in a state that does not self-heating, the flow does not hit surrounding it is obtained Ru multipoint measurement flow meter density information of the fluid by the fluid to measure the power consumption value or resistance value of the heater of the thermal type flow sensor disposed in a position and out by diffusion.
[0008]
In the present invention, temperature information can be obtained by measuring the resistance value of the resistance portion of the thermal flow sensor in a state that does not cause self-heating without providing a temperature sensor.
[0009]
In the present invention, the concentration information can be obtained by measuring the power consumption value or resistance value of the heater of the thermal flow sensor installed at a position where the flow does not directly hit without providing the concentration sensor.
Further, according to the present invention, at least one thermal flow sensor is installed at a position where the flow is not directly applied to obtain a reference output in a state where there is no flow, so that the zero point output of each thermal flow sensor can be changed over time. Correction can be performed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described.
An embodiment of the present invention will be described with reference to FIGS.
[0011]
FIG. 1 is an explanatory diagram of an embodiment of the multipoint measurement type flow meter 1 of the present invention.
The multipoint measurement type flow meter 1 includes a plurality of thermal flow sensors 12 attached to one surface of a substrate 11 that is a rectangular parallelepiped, and a temperature sensor 13, a pressure sensor 14, and a concentration sensor 15 attached to the other surface of the substrate 11. And a lead wire 17, an attached circuit 18 and the like. The substrate 11 is made of a material such as metal or ceramic. As the thermal flow sensor 12, the temperature sensor 13, the pressure sensor 14, and the concentration sensor 15, conventional ones may be used. As the thermal type flow sensor 12, there is used a sensor that measures by utilizing the fact that the heating body is inserted into the fluid flow and the amount of heat taken away by the fluid changes depending on the flow velocity. As the temperature sensor 13, a thermocouple, a resistance thermometer, or the like is used. As the pressure sensor 14, a semiconductor pressure sensor using a piezoresistive effect or using a change in capacitance is used. As the concentration sensor 15, a gas sensor that measures a change in electrical resistance due to surface adsorption of gas molecules is used.
It is also possible to obtain temperature information by measuring the resistance value of the resistance portion 16 of the thermal flow sensor in a state where it does not cause self-heating. If this method is used, it is not necessary to provide the temperature sensor 13. Further, concentration information can be obtained from the power consumption value or the resistance value of the heater portion so that no flow is applied to the thermal flow sensor. If this method is used, concentration information can be obtained using a thermal flow sensor, so that a thermal flow sensor with a windbreak wall can be used as a component, and the attached circuit is also a thermal flow sensor. There are merits such as common and good.
[0012]
The temperature sensor 13 measures the temperature of the fluid near the thermal flow sensor 12, the pressure sensor 14 measures the pressure of the nearby fluid, and the concentration sensor 15 measures the concentration of the nearby fluid.
Therefore, as compared with the case where these sensors are provided separately from the flow meter, errors relating to correction of the flow value due to temperature, pressure, and concentration can be reduced, and the response speed to environmental changes is increased.
[0013]
In addition, as in the case of the concentration sensor 15 in FIG. 1, at least one thermal flow sensor is installed at a position where the flow of the surrounding fluid does not hit but the surrounding fluid enters and exits by diffusion, so that an output in a state where there is no flow ( Zero point output). By comparing this value with the zero point output at the time of shipment stored in the microcomputer, you can know the drift amount of the zero point output due to changes over time, and subtract this drift amount from the output value of each thermal flow sensor. The correction for the change with time can be performed.
[0014]
FIG. 2 shows a circuit block diagram for calculating a flow value based on measured values of various sensors attached to the multipoint measurement type flow meter 1.
The output of the thermal flow sensor 12, the temperature sensor 13 (or the resistance portion 16 in a non-heat generation state), the pressure sensor 14 and the concentration sensor 15 (including the type using the thermal flow sensor) and the reference zero point output are respectively It is controlled by the control circuit 21, is input to the A / D converter 23 via the control circuit 21 and the arithmetic circuit 22, and is input to the microcomputer 24 at once. In the microcomputer 24, correction is performed using the measured values of the temperature sensor, pressure sensor, and concentration sensor. The measured value of the concentration sensor is corrected by the measured value of the temperature sensor and the pressure sensor, and the measured value of the thermal flow sensor is corrected for temperature, pressure, concentration, and the like. These obtained data are averaged for a plurality of thermal flow sensors or with past data, etc., so that flow rate values such as instantaneous flow rate, integrated flow rate, local flow rate, average flow rate, temperature, Various data such as pressure and concentration are calculated. These various data are output or displayed by the output or display means 25.
[0015]
In the microcomputer 24, instead of various corrections performed by the measured values of the temperature sensor 13, the pressure sensor 14, and the concentration sensor 15, other conditions may be input and processed for the temperature, pressure, and concentration as parameters. The flow rate value can be calculated and output as a value under a desired temperature, pressure and concentration condition. Further, the microcomputer 24 can perform failure diagnosis using the reference zero point output.
[0016]
As described above, since the temperature sensor, the pressure sensor, and the concentration sensor are built in the multipoint measurement type flow meter equipped with the plurality of thermal flow sensors 1, it can also serve as the thermometer, the pressure meter, and the concentration meter. Furthermore, it is possible to accurately correct the temperature, pressure, and concentration of the measured value of the thermal flow sensor, and it is possible to perform highly accurate measurement even in an environment where the temperature, pressure, or concentration changes.
[0017]
【The invention's effect】
According to the present invention, highly accurate measurement is possible even in an environment where temperature, pressure, or concentration changes. Moreover, since the temperature sensor, the pressure sensor, and the concentration sensor are built in the multipoint measurement type flow meter, the installation space can be reduced. By using the resistance part of the thermal type flow sensor as a temperature sensor and using the heater of the thermal type flow sensor installed in a place where no flow is applied as a concentration sensor, it is possible to divert parts and attached circuits and reduce manufacturing costs. be able to.
Furthermore, since the correction with respect to the aging of the thermal flow sensor can be automatically performed using the reference zero point output, it can be used without maintenance for a long time. Since it is possible to input different conditions for the temperature, pressure, and concentration as parameters instead of the sensor measurement values obtained, conversion values assuming the desired temperature, pressure, and concentration conditions (for example, flow rate values) Standard values (values at 0 ° C. and 1 atm) can also be output.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a multipoint measurement type flow meter of the present invention.
FIG. 2 is a circuit block diagram of the present invention.
FIG. 3 is an explanatory diagram of a conventional multipoint measurement type flow meter.
FIG. 4 is an explanatory diagram of the use of a multipoint measurement type flow meter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Multipoint measurement type flow meter 11 Board | substrate 12 Thermal type flow sensor 13 Temperature sensor 14 Pressure sensor 15 Concentration sensor 16 Resistance part 17 Lead wire 18 Attached circuit 21 Control circuit 22 Arithmetic circuit 23 A / D converter 24 Microcomputer 25 Output or display means

Claims (3)

In a multipoint measurement type flow meter that measures flow velocity values at multiple positions with multiple thermal flow sensors,
Temperature of the fluid, the provided means for measuring the pressure or concentration, temperature measurements of the thermal type flow sensor, have a correction means for correcting the measured value of the pressure or concentration, the resistance value of the resistance portion of the thermal type flow sensor The temperature information of the fluid is obtained by measuring in a state that does not cause self-heating, and the power consumption value or resistance value of the heater of the thermal flow sensor installed at a position where the surrounding fluid does not flow but the surrounding fluid enters and exits by diffusion is calculated. multipoint measurement flow meter, characterized in Rukoto obtain density information of the fluid by measuring. Compare the zero point output measured in the absence of the flow of the thermal flow sensor installed at a position where the flow of the fluid flows in and out of the surroundings with the flow, but with the factory zero point output stored in the microcomputer. A draft amount of a zero point output due to a change with time is obtained, and the draft amount of the zero point output is subtracted from an output value of a thermal flow sensor installed at a position where a flow hits to correct for a change with time. The multipoint measurement type flow meter according to 1. The multipoint measurement type flow meter according to claim 1 , wherein a plurality of thermal flow sensors are provided on one surface of the rectangular parallelepiped, and a temperature sensor, a pressure sensor, and a concentration sensor are provided on the other surface .

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