JP3637278B2 - 2-sensor flow meter - Google Patents

2-sensor flow meter Download PDF

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Publication number
JP3637278B2
JP3637278B2 JP2000386549A JP2000386549A JP3637278B2 JP 3637278 B2 JP3637278 B2 JP 3637278B2 JP 2000386549 A JP2000386549 A JP 2000386549A JP 2000386549 A JP2000386549 A JP 2000386549A JP 3637278 B2 JP3637278 B2 JP 3637278B2
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Japan
Prior art keywords
voltage
flow meter
sensor
voltage signal
pitot tube
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JP2000386549A
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Japanese (ja)
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JP2002188943A (en
Inventor
宏慶 許
鵬飛 ▲ハオ▼
岱強 楊
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SMC Corp
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SMC Corp
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Description

【０００１】
【発明の属する技術分野】
本発明は、熱式流量計とピトー管を用いた流量計とを組み合わせた２センサ式流量計に関する。
【０００２】
【従来の技術】
熱式流量計は、わずかな流れを測定することができ、測定精度が高くまた小形で取付が簡単であるため、各種の分野で多用されている。熱式流量計は、流量測定用抵抗体と温度補償用抵抗体との温度差が、流体通路内の流量に関係なく、常に一定に保たれるように、流量測定用抵抗体が通電制御されるようになっている。そして、流体通路内の流量が少ないときには流量測定用抵抗体に低圧の電流が流れ、流量が多いときには流量測定用抵抗体に高圧の電流が流れ、その単調増加関数から流量を測定している。
【０００３】
【発明が解決しようとする課題】
熱式流量計の流量測定用抵抗体に流す電圧には限界があり、流量が多くなる（流速が速くなる）と熱式流量計の出力が飽和するので、測定範囲を大流量域まで広げることは困難である。
本発明は、熱式流量計に大流量を測定可能な他の測定手段を組み合わせて、高い測定精度で測定範囲を拡大することを課題とする。
【０００４】
【課題を解決するための手段】
本発明は、流体通路に熱式流量計の熱式センサ及びピトー管が配設され、熱式センサの電圧信号の電圧値が下限設定電圧を超えかつ（熱式センサの）切換設定電圧以下のときは、熱式流量計で測定された測定結果がディスプレーに表示され、ピトー管を用いた流量計の圧力センサの電圧信号の電圧値が上限設定電圧以下で（圧力センサの）切換設定電圧を超えるときは、ピトー管を用いた流量計で測定された測定結果がディスプレーに表示され、熱式センサの電圧信号の電圧値が（熱式センサの）切換設定電圧を超えるときは、熱式センサの電圧信号の増幅率を下げるともにピトー管を用いた流量計の圧力センサの電圧信号の増幅率を上げ、ピトー管を用いた流量計の圧力センサの電圧信号の電圧値が（圧力センサの）切換設定電圧以下のときは、ピトー管を用いた流量計の圧力センサの電圧信号の増幅率を下げるとともに熱式センサの電圧信号の増幅率を上げることを第１構成とする。 本発明は、第１構成において、熱式センサの電圧信号の電圧値が（熱式センサの）下限設定電圧以下のとき及びピトー管を用いた流量計の圧力センサの電圧信号の電圧値が（圧力センサの）上限設定電圧を超えるときは、ディスプレーにエラー表示がされることを第２構成とする。
【０００５】
【発明の実施の形態】
図１，図２は本発明の実施の形態を示す。図１(a) において、２センサ式流量計10は、管11の上部にケース12が配設された外形をしている。管11の流体通路13の中心線上には、熱式流量計の流量測定用抵抗体16・温度補償用抵抗体17及びピトー管20の鼻管21（図１(b) 参照）が配設され、流体通路13の流体は入口部14から出口部15に向かって流れるように設定されている。流量測定用抵抗体16及び温度補償用抵抗体17は、支持柱により支持され、それらは制御回路18に接続されている。熱式流量計では制御回路18において、流量測定用抵抗体（熱式センサ）16に流れる電圧信号から流量を計算するようにされている。
【０００６】
図１に示すように、標準形のピトー管20には直角に交差した鼻管21と元管22とがあり、鼻管21の中心線は流体通路13の中心線と正しく一致して配置され、元管22は管11の支持具23に挿通され支持されている。ピトー管20は先端部（図１(b) では左端部）及び基端部（図１(b) では下端部）以外は二重管になっており、内側管の内部が全圧通路であり、内側管と外側管との間の部分が静圧通路である。鼻管21の先端には全圧測定孔24が形成され、全圧測定孔24は全圧通路を介して全圧検出器26に連通されている。鼻管21の側部には静圧測定孔25が形成され、静圧測定孔25は静圧通路を介して静圧検出器27に連通されている。ピトー管20を用いた流量計では、全圧検出器26によって全圧Ｐ0 が検出され、静圧検出器27によって静圧Ｐが検出され、制御回路18において、圧力の差（Ｐ0 −Ｐ）から流速が求められる。
【０００７】
ピトー管を用いた流量計は、低速域で発生する差圧が微小であるため、差圧の検出が困難であるが、中速域から高速域の流量の測定には適している。そこで、本発明では、低速域の流量から中速設定値（８．６ｍ／ｓ）の流量（２６０Ｌ／ｍｉｎ（ＡＮＲ））を熱式流量計で測定し、中速設定値の流量から高速域の流量をピトー管を用いた流量計で測定することを基本としている。
【０００８】
図２によって、２センサ式流量計の実施の形態の機能を説明する。プログラムがスタートすると、ステップＳ１で初期値の設定を行い、ステップＳ２で熱式流量計の熱式センサ（流量測定用抵抗体16）の電圧信号を読み取る。ステップＳ３において、熱式センサの電圧信号はＡ／Ｄ変換され増幅され、続いてステップＳ４において制御回路18で熱式センサの電圧信号から流量が計算され、計算結果がケース12の上面のディスプレイ29（図１(a) 参照）に表示される。
【０００９】
ステップＳ５において、熱式センサの電圧信号の電圧値が（熱式センサの）下限設定電圧（実験装置では０．０５Ｖ。このとき、流量が１０Ｌ／ｍｉｎ（ＡＮＲ），流速が０．３３ｍ／ｓ）を超えるか否かの判定が行われる。ステップＳ５で熱式センサの電圧信号の電圧値が下限設定電圧を超えない（下限設定電圧以下である）と判定された場合は、流量が少なすぎて正確な測定ができないので、ステップＳ６でディスプレイ29にエラー表示をし、ステップＳ２に戻る。
【００１０】
ステップＳ５で熱式センサの電圧信号の電圧値が下限設定電圧を超えると判定されたときは、ステップＳ７で熱式センサの電圧信号の電圧値が熱式センサの切換設定電圧（実験装置では５Ｖ。このとき、流量が２６０Ｌ／ｍｉｎ（ＡＮＲ），流速（中速設定値）が８．６ｍ／ｓ）を超えるか否かの判定が行われる。熱式センサの電圧信号の電圧値が熱式センサの切換設定電圧を超えると、熱式センサの出力が飽和する。ステップＳ７で熱式センサの電圧信号の電圧値が熱式センサの切換設定電圧を超えない（切換設定電圧以下である）と判定されたときは、熱式センサの測定範囲内にあるので、ディスプレイ29に流量が継続して表示され（エラー表示はされない）、ステップＳ２に戻る。
【００１１】
ステップＳ７で熱式センサの電圧信号の電圧値が熱式センサの切換設定電圧を超えると判定されたときは、ステップＳ８で、熱式センサの電圧信号の増幅率を下げ、ピトー管20を用いた流量計の圧力センサの電圧信号の増幅率を上げ、ステップＳ９へ進む。この操作により、熱式センサの流量をディスプレイに表示することが不能となり、ピトー管を用いた流量計の流量をディスプレイに表示することとなる。
【００１２】
ステップＳ９でピトー管を用いた流量計の圧力センサ（全圧検出器26・静圧検出器27）の電圧信号を読み取る。ステップＳ１０でこの電圧信号はＡ／Ｄ変換され増幅され、続いてステップＳ１１において制御回路18でこの電圧信号から流量が計算され、計算結果がディスプレイ29に表示される。
【００１３】
ステップＳ１２において、ピトー管を用いた流量計の圧力センサの電圧信号の電圧値が（圧力センサの）上限設定電圧（実験の装置では５Ｖ、流量が１０００Ｌ／ｍｉｎ（ＡＮＲ），流速が３２．９ｍ／ｓ）を超えるか否かの判定が行われ、ピトー管を用いた流量計の圧力センサの電圧信号の電圧値が上限設定電圧を超えると判定された場合は、流量が大すぎて正確な測定ができない。ステップＳ１２でピトー管を用いた流量計の圧力センサの電圧信号の電圧値が上限設定電圧を超えると判定されたときは、ステップＳ１３でディスプレイ29にエラー表示をし、ステップＳ９に戻る。
【００１４】
ステップＳ１２でピトー管を用いた流量計の圧力センサの電圧信号の電圧値が上限設定電圧を超えない（上限設定電圧以下である）と判定されたときは、ステップＳ１４でピトー管を用いた流量計の圧力センサの電圧信号の電圧値が圧力センサの切換設定電圧（実験装置では０．０５Ｖ。このとき、流量が２６０Ｌ／ｍｉｎ（ＡＮＲ），流速（中速設定値）が８．６ｍ／ｓ）を超えるか否かの判定が行われる。ステップＳ１４でピトー管を用いた流量計の圧力センサの電圧信号の電圧値が圧力センサの切換設定電圧を超えると判定されたときは、ピトー管を用いた流量計の測定範囲内にあるので、ディスプレイ29に流量が継続して表示され（エラー表示はされていない）、ステップＳ９に戻る。
【００１５】
ステップＳ１４でピトー管を用いた流量計の圧力センサの電圧信号の電圧値が圧力センサの切換設定電圧を超えない（切換設定電圧以下である）と判定されたときは、ステップＳ１５でピトー管20を用いた流量計の圧力センサの電圧信号の増幅率を下げ、熱式センサの電圧信号の増幅率を上げ、ステップＳ２へ進む。この操作により、ピトー管を用いた流量計の流量をディスプレイに表示することが不能となり、熱式センサの流量をディスプレイに表示することとなる。
【００１６】
【発明の効果】
本発明においては、下限設定電圧を越えかつ切換設定電圧以下のときは、流量が熱式流量計で測定されて測定結果がディスプレーに表示され、上限設定電圧以下で切換設定電圧を越えるときは、流量がピトー管を用いた流量計で測定されて測定結果がディスプレーに表示される。低速域から中速域（切換設定電圧以下のとき）の流量の測定を得意とする熱式流量計と、中速域から高速域（切換設定電圧を越えるとき）の流量を測定できるピトー管を用いた流量計とを組み合わせたので、高い測定精度で測定範囲を拡大することができる。そして、本発明では、熱式流量計で測定された測定結果の表示と、ピトー管を用いた流量計で測定された測定結果の表示とが、切換設定電圧を基準として自動的に切り換えられる。熱式センサの電圧信号の電圧値が切換設定電圧を超えるときは、熱式センサの電圧信号の増幅率を下げるともにピトー管を用いた流量計の圧力センサの電圧信号の増幅率を上げ、ピトー管を用いた流量計の圧力センサの電圧信号の電圧値が切換設定電圧以下のときは、ピトー管を用いた流量計の圧力センサの電圧信号の増幅率を下げるとともに熱式センサの電圧信号の増幅率を上げるので、熱式センサの出力端子とピトー管を用いた流量計の出力端子とを同時にディスプレー装置に接続することができ、回路構成が簡単になる。
【図面の簡単な説明】
【図１】図１(a) は本発明の２センサ式流量計の実施の形態の説明図であり、図１(b) は本発明の実施の形態に用いられるピトー管の説明図である。
【図２】本発明の２センサ式流量計の実施の機能を示すフローチャートである。
【符号の説明】
10 ２センサ式流量計
13 流体通路
16 熱式センサ（流量測定用抵抗体）
20 ピトー管
26・27 圧力センサ
29 ディスプレィ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a two-sensor flow meter in which a thermal flow meter and a flow meter using a Pitot tube are combined.
[0002]
[Prior art]
Thermal flow meters can measure a slight flow, have high measurement accuracy, are small and easy to mount, and are therefore widely used in various fields. The thermal flow meter is controlled by energizing the flow measurement resistor so that the temperature difference between the flow measurement resistor and the temperature compensation resistor is always kept constant regardless of the flow rate in the fluid passage. It has become so. When the flow rate in the fluid passage is small, a low pressure current flows through the flow rate measuring resistor, and when the flow rate is large, a high voltage current flows through the flow rate measuring resistor, and the flow rate is measured from its monotonically increasing function.
[0003]
[Problems to be solved by the invention]
There is a limit to the voltage applied to the flow measurement resistor of the thermal flow meter, and if the flow rate increases (the flow velocity increases), the output of the thermal flow meter saturates, so the measurement range should be expanded to a large flow range. It is difficult.
An object of the present invention is to expand a measurement range with high measurement accuracy by combining a thermal flow meter with other measurement means capable of measuring a large flow rate.
[0004]
[Means for Solving the Problems]
In the present invention, a thermal sensor and a Pitot tube of a thermal flow meter are disposed in a fluid passage, and a voltage value of a voltage signal of the thermal sensor exceeds a lower limit setting voltage and is equal to or lower than a switching setting voltage (of the thermal sensor). When the measurement result measured by the thermal flow meter is displayed on the display, the voltage value of the voltage signal of the pressure sensor of the flow meter using the Pitot tube is below the upper limit set voltage, and the switching set voltage (of the pressure sensor) If it exceeds, the measurement result measured with a flow meter using a Pitot tube is displayed on the display. If the voltage value of the voltage signal of the thermal sensor exceeds the switching setting voltage (of the thermal sensor), the thermal sensor The voltage signal of the pressure sensor of the flow meter using the Pitot tube is increased, and the voltage value of the pressure signal of the flow meter using the Pitot tube is increased (of the pressure sensor) Below the switching set voltage Is to raise the amplification factor of the voltage signal of the thermal sensor with reducing the amplification factor of the voltage signal of the pressure sensor of the flow meter using the Pitot tube and the first configuration. In the first configuration , when the voltage value of the voltage signal of the thermal sensor is equal to or lower than the lower limit set voltage (of the thermal sensor) and the voltage value of the voltage signal of the pressure sensor of the flow meter using the Pitot tube is ( When the upper limit set voltage (of the pressure sensor) is exceeded, the second configuration is that an error is displayed on the display.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show an embodiment of the present invention. In FIG. 1A, a two-sensor type flow meter 10 has an outer shape in which a case 12 is disposed on an upper portion of a pipe 11. On the center line of the fluid passage 13 of the tube 11, a flow measuring resistor 16 and a temperature compensating resistor 17 of the thermal flow meter and a nasal tube 21 of the Pitot tube 20 (see FIG. 1 (b)) are arranged. The fluid in the fluid passage 13 is set to flow from the inlet portion 14 toward the outlet portion 15. The flow rate measuring resistor 16 and the temperature compensating resistor 17 are supported by support columns, and are connected to the control circuit 18. In the thermal type flow meter, the control circuit 18 calculates the flow rate from the voltage signal flowing through the flow rate measuring resistor (thermal sensor) 16.
[0006]
As shown in FIG. 1, the standard pitot tube 20 has a nasal tube 21 and a main tube 22 intersecting at right angles, and the center line of the nasal tube 21 is arranged in line with the center line of the fluid passage 13. The main tube 22 is inserted into and supported by the support 23 of the tube 11. The Pitot tube 20 is a double tube except for the tip (left end in Fig. 1 (b)) and the base end (lower end in Fig. 1 (b)), and the inside of the inner tube is the total pressure passage. A portion between the inner tube and the outer tube is a static pressure passage. A total pressure measurement hole 24 is formed at the tip of the nasal tube 21, and the total pressure measurement hole 24 communicates with the total pressure detector 26 via a total pressure passage. A static pressure measurement hole 25 is formed in the side portion of the nasal canal 21, and the static pressure measurement hole 25 is communicated with the static pressure detector 27 through a static pressure passage. In the flow meter using the Pitot tube 20, the total pressure P 0 is detected by the total pressure detector 26, the static pressure P is detected by the static pressure detector 27, and the pressure difference (P 0 −P) is detected by the control circuit 18. ) To obtain the flow velocity.
[0007]
A flow meter using a Pitot tube is difficult to detect the differential pressure because the differential pressure generated in the low speed range is very small, but is suitable for measuring the flow rate from the medium speed range to the high speed range. Therefore, in the present invention, the flow rate (260 L / min (ANR)) at the medium speed set value (8.6 m / s) is measured from the flow rate in the low speed range with a thermal flow meter, Is basically measured with a flowmeter using a Pitot tube.
[0008]
The function of the embodiment of the two-sensor type flow meter will be described with reference to FIG. When the program starts, the initial value is set in step S1, and the voltage signal of the thermal sensor (flow measurement resistor 16) of the thermal flow meter is read in step S2. In step S3, the voltage signal of the thermal sensor is A / D converted and amplified. Subsequently, in step S4, the flow rate is calculated from the voltage signal of the thermal sensor in the control circuit 18, and the calculation result is displayed on the display 29 on the upper surface of the case 12. (See Fig. 1 (a)).
[0009]
In step S5, the voltage value of the voltage signal of the thermal sensor is the lower limit setting voltage (of the thermal sensor) (0.05 V in the experimental apparatus. At this time, the flow rate is 10 L / min (ANR) and the flow rate is 0.33 m / s. ) Is determined. If it is determined in step S5 that the voltage value of the voltage signal of the thermal sensor does not exceed the lower limit set voltage (below the lower limit set voltage), the flow rate is too small to perform an accurate measurement. An error is displayed in 29, and the process returns to step S2.
[0010]
If it is determined in step S5 that the voltage value of the voltage signal of the thermal sensor exceeds the lower limit setting voltage, the voltage value of the voltage signal of the thermal sensor is changed to the switching setting voltage of the thermal sensor (5 V in the experimental apparatus) in step S7. At this time, it is determined whether or not the flow rate exceeds 260 L / min (ANR) and the flow velocity (medium speed set value) exceeds 8.6 m / s). When the voltage value of the voltage signal of the thermal sensor exceeds the switching setting voltage of the thermal sensor, the output of the thermal sensor is saturated. If it is determined in step S7 that the voltage value of the voltage signal of the thermal sensor does not exceed the switching setting voltage of the thermal sensor (below the switching setting voltage), it is within the measurement range of the thermal sensor, so the display The flow rate is continuously displayed in 29 (no error is displayed), and the process returns to step S2.
[0011]
When it is determined in step S7 that the voltage value of the voltage signal of the thermal sensor exceeds the switching setting voltage of the thermal sensor, in step S8, the amplification factor of the voltage signal of the thermal sensor is lowered and the Pitot tube 20 is used. Increase the amplification factor of the voltage signal of the pressure sensor of the flowmeter, and proceed to step S9. By this operation, it becomes impossible to display the flow rate of the thermal sensor on the display, and the flow rate of the flow meter using the Pitot tube is displayed on the display.
[0012]
In step S9, the voltage signal of the pressure sensor (total pressure detector 26 / static pressure detector 27) of the flow meter using the Pitot tube is read. In step S10, the voltage signal is A / D converted and amplified. In step S11, the control circuit 18 calculates the flow rate from the voltage signal, and the calculation result is displayed on the display 29.
[0013]
In step S12, the voltage value of the voltage signal of the pressure sensor of the flow meter using the Pitot tube is the upper limit set voltage (of the pressure sensor) (5 V in the experimental apparatus, the flow rate is 1000 L / min (ANR), and the flow rate is 32.9 m. / S), and if it is determined that the voltage value of the voltage signal of the pressure sensor of the flow meter using the Pitot tube exceeds the upper limit set voltage, the flow rate is too large and accurate. Measurement is not possible. If it is determined in step S12 that the voltage value of the voltage signal of the pressure sensor of the flow meter using the Pitot tube exceeds the upper limit set voltage, an error is displayed on the display 29 in step S13, and the process returns to step S9.
[0014]
When it is determined in step S12 that the voltage value of the voltage signal of the pressure sensor of the flowmeter using the Pitot tube does not exceed the upper limit set voltage (below the upper limit set voltage), the flow rate using the Pitot tube in step S14. The voltage value of the voltage signal of the pressure sensor of the meter is the switching setting voltage of the pressure sensor (0.05 V in the experimental apparatus. At this time, the flow rate is 260 L / min (ANR) and the flow rate (medium speed setting value) is 8.6 m / s. ) Is determined. When it is determined in step S14 that the voltage value of the voltage signal of the pressure sensor of the flow meter using the Pitot tube exceeds the switching setting voltage of the pressure sensor, it is within the measurement range of the flow meter using the Pitot tube. The flow rate is continuously displayed on the display 29 (no error is displayed), and the process returns to step S9.
[0015]
If it is determined in step S14 that the voltage value of the voltage signal of the pressure sensor of the flow meter using the Pitot tube does not exceed the switching setting voltage of the pressure sensor (below the switching setting voltage), the Pitot tube 20 is determined in step S15. Decrease the amplification factor of the voltage signal of the pressure sensor of the flow meter using, increase the amplification factor of the voltage signal of the thermal sensor, and proceed to step S2. By this operation, it becomes impossible to display the flow rate of the flow meter using the Pitot tube on the display, and the flow rate of the thermal sensor is displayed on the display.
[0016]
【The invention's effect】
In the present invention, when the lower limit set voltage is exceeded and the switching set voltage is less than or equal to, the flow rate is measured with a thermal flow meter and the measurement result is displayed on the display . The flow rate is measured with a flow meter using a Pitot tube, and the measurement result is displayed on the display. A thermal flow meter that excels at measuring the flow rate from the low speed range to the medium speed range (when the switching set voltage is below) and a Pitot tube that can measure the flow rate from the medium speed range to the high speed range (when the switching set voltage is exceeded) Since the flowmeter used is combined, the measurement range can be expanded with high measurement accuracy. In the present invention, the display of the measurement result measured with the thermal flow meter and the display of the measurement result measured with the flow meter using the Pitot tube are automatically switched based on the switching set voltage. When the voltage value of the voltage signal of the thermal sensor exceeds the switching set voltage, the amplification factor of the voltage signal of the flow meter using the Pitot tube is increased while the amplification factor of the voltage signal of the thermal sensor is lowered, and the Pitot When the voltage signal of the pressure sensor of the flow meter using a pipe is below the switching set voltage, the amplification factor of the voltage signal of the pressure sensor of the flow meter using the Pitot tube is lowered and the voltage signal of the thermal sensor is reduced. Since the amplification factor is increased, the output terminal of the thermal sensor and the output terminal of the flowmeter using the Pitot tube can be connected to the display device at the same time, and the circuit configuration is simplified.
[Brief description of the drawings]
FIG. 1 (a) is an explanatory diagram of an embodiment of a two-sensor type flow meter of the present invention, and FIG. 1 (b) is an explanatory diagram of a Pitot tube used in the embodiment of the present invention. .
FIG. 2 is a flowchart showing functions of an implementation of the two-sensor flow meter of the present invention.
[Explanation of symbols]
10 Two-sensor flow meter
13 Fluid passage
16 Thermal sensor (resistance element for flow rate measurement)
20 Pitot tube
26 ・ 27 Pressure sensor
29 Display

Claims (2)

流体通路に熱式流量計の熱式センサ及びピトー管が配設され、熱式センサの電圧信号の電圧値が下限設定電圧を越えかつ切換設定電圧以下のときは、熱式流量計で測定された測定結果がディスプレーに表示され、ピトー管を用いた流量計の圧力センサの電圧信号の電圧値が上限設定電圧以下で切換設定電圧を超えるときは、ピトー管を用いた流量計で測定された測定結果がディスプレーに表示され、熱式センサの電圧信号の電圧値が切換設定電圧を超えるときは、熱式センサの電圧信号の増幅率を下げるともにピトー管を用いた流量計の圧力センサの電圧信号の増幅率を上げ、ピトー管を用いた流量計の圧力センサの電圧信号の電圧値が切換設定電圧以下のときは、ピトー管を用いた流量計の圧力センサの電圧信号の増幅率を下げるとともに熱式センサの電圧信号の増幅率を上げる２センサ式流量計。When the thermal sensor and Pitot tube of the thermal flow meter are installed in the fluid passage, and the voltage value of the voltage signal of the thermal sensor exceeds the lower limit set voltage and is below the switching set voltage, it is measured with the thermal flow meter. When the voltage value of the voltage signal of the pressure sensor of the flow meter using the Pitot tube is below the upper limit set voltage and exceeds the switching set voltage, the measurement result was measured with the flow meter using the Pitot tube. When the measurement result is displayed on the display and the voltage value of the thermal sensor voltage signal exceeds the switching set voltage, the voltage of the pressure sensor of the flow meter using the Pitot tube is lowered while reducing the amplification factor of the voltage signal of the thermal sensor. Increase the signal amplification factor, and lower the voltage signal amplification factor of the flow sensor pressure sensor using the Pitot tube when the voltage signal voltage value of the flow meter pressure sensor using the Pitot tube is less than the switching set voltage. With 2 sensor flow meter to increase the amplification factor of the voltage signal of Formula sensor. 熱式センサの電圧信号の電圧値が下限設定電圧以下のとき及びピトー管を用いた流量計の圧力センサの電圧信号の電圧値が上限設定電圧を超えるときは、ディスプレーにエラー表示がされる請求項１の２センサ式流量計。When the voltage value of the voltage signal of the thermal sensor is below the lower limit set voltage or when the voltage signal voltage value of the pressure sensor of the flowmeter using a pitot tube exceeds the upper limit set voltage, an error is displayed on the display. Item 2. A two-sensor flow meter according to item 1 .
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