JPH0894406A - Output correction device for flow velocity sensor and flow meter - Google Patents

Abstract

(57) [Summary] [Purpose] It is possible to reduce the influence of fluctuations in flow velocity due to pressure fluctuations, etc., without causing an error in the calculated flow rate. [Structure] The linearizing circuit 40 inputs the output signal of the flow sensor 30 which has a non-linear relationship with the flow rate,
A signal having a substantially linear relationship with the flow rate is output. The averaging circuit 41 averages the output signal of the linearizing circuit 40. The calculation unit 45 inputs the output signal of the averaging circuit 41 via the A / D converter 42 and calculates the flow rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow velocity sensor output correction device for correcting the output of a flow velocity sensor, and a flow meter using this output correction device.

[0002]

2. Description of the Related Art As a flow meter used for a gas meter or the like, one using a flow velocity sensor is known. For example, the thermal type flow velocity sensor obtains the flow velocity by utilizing the fact that the movement of heat in the pipe is related to the flow velocity of the fluid flowing in the pipe, and in the flow meter using the thermal type flow velocity sensor,
The flow rate is calculated from the flow velocity and displayed. Further, since the thermal type flow rate sensor is suitable for measuring a small flow rate, there is a flow rate meter in which a fluidic flow meter and a thermal type flow rate sensor are used in combination.

By the way, in a flow velocity sensor, for example, a thermal type flow velocity sensor, the relation between the flow velocity or flow rate and the sensor output is non-linear. In the conventional flowmeter using the flow velocity sensor having such a non-linear characteristic, the flow rate calculation unit using a microcomputer or the like calculates the flow rate in consideration of the non-linear characteristic of the flow velocity sensor.

[0004]

By the way, in a flowmeter using a flow velocity sensor, there is a problem that the flow velocity fluctuates due to disturbance such as pressure fluctuation of gas on the upstream side, and as a result, the calculated flow amount also fluctuates. is there. Therefore, it is conceivable to obtain the average value of the output of the flow velocity sensor in a predetermined time and calculate the flow rate from this average value.

However, in this case, the following problems occur due to the non-linear characteristics of the flow velocity sensor. That is,
As shown in FIG. 8, if the flow rate Q fluctuates in the width of W _Q and the average flow rate is Q _AV , the sensor output S fluctuates in the width of W _S , and the average value of the sensor output S is S _AV . Become. On the other hand, the true sensor output corresponding to the average flow rate Q _AV is S ₀ . However, since the flow rate Q and the sensor output S have a non-linear relationship, an error e (= S ₀ −) between the true sensor output S ₀ corresponding to the average flow rate Q _AV and the average value S _AV of the sensor outputs. S _AV )
Occurs. Therefore, this error causes an error in the flow rate calculated from the average value S _AV of the sensor output.

The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to reduce the influence of fluctuations in flow velocity due to pressure fluctuations and the like without causing an error in the calculated flow rate. An object is to provide an output correction device for a flow velocity sensor and a flow meter.

[0007]

According to a first aspect of the present invention, there is provided an output correction device for a flow velocity sensor, wherein an output signal of a flow velocity sensor for outputting a signal according to a flow velocity of a fluid is input, and a relation with a flow rate is substantially linear. And a averaging means for averaging the output signals of the linearizing means.

In this output correction device for the flow velocity sensor, the output signal of the flow velocity sensor is input to the linearizing means, and the linearizing means outputs a signal having a substantially linear relationship with the flow rate. Then, the averaging means averages the output signals of the linearizing means. The signal averaged in this way corresponds to the average value of the true flow rates.

According to another aspect of the flowmeter of the present invention, a flow velocity sensor that outputs a signal corresponding to the flow velocity of the fluid and an output signal of the flow velocity sensor are input, and a signal that has a substantially linear relationship with the flow rate is output. The linearizing means, the averaging means for averaging the output signals of the linearizing means, and the flow rate calculating means for calculating the flow rate based on the signal averaged by the averaging means.

In this flow meter, the output signal of the flow velocity sensor is input to the linearizing means, and the linearizing means outputs a signal having a substantially linear relationship with the flow rate. And
The output signal of the linearization means is averaged by the averaging means, and the flow rate calculation means calculates the flow rate based on the averaged signal.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 2 is a sectional view showing the structure of a flowmeter according to the first embodiment of the present invention. This flow meter is used as a gas meter. As shown in FIG. 2, the flowmeter includes a main body 10 having an inlet portion 11 for receiving gas (gas) and an outlet portion 12 for discharging gas. A partition wall 13 is provided in the main body 10, and a first gas flow path 14 is formed between the partition wall 13 and the inlet portion 11.
The second gas flow path 15 is formed between the outlet 12 and the outlet 12. An opening 16 is provided in the partition wall 13, and a shutoff valve 17 capable of closing the opening 16 is provided in the first gas flow path 14. A solenoid 18 is fixed to the outside of the body 10, and a plunger 19 of the solenoid 18 is fixed.
Is penetrated through the side wall of the main body 10 and joined to the shutoff valve 17. Further, a spring 20 is provided around the plunger 19 between the shutoff valve 17 and the main body 10, and the spring 20 biases the shutoff valve 17 toward the opening portion 16 side.

In the second gas passage 15, there is provided a nozzle 21 for passing the gas received from the inlet portion 11 to generate a jet flow. A flow sensor 30 which is a thermal type flow velocity sensor is arranged in the passage of the nozzle 21.
Although not shown, the flow sensor 30 has a heat generating part and two temperature sensors arranged on the upstream side and the downstream side of the heat generating part, and keeps a constant temperature difference detected by the two temperature sensors. Therefore, the flow rate corresponding to the flow velocity is calculated from the power supplied to the heat generating section, or the heat generating section is heated with a constant current or constant power, and the flow rate is calculated from the temperature difference detected by the two temperature sensors. There is.

On the downstream side of the nozzle 21, a pair of side walls 23 and 24 forming an enlarged flow path are provided. A predetermined space is provided between the side walls 23, 24 so that the first target 25 is located upstream and the second target 26 is located downstream.
Are arranged respectively. The gas that has passed through the nozzle 21 is provided outside the side walls 23 and 24.
A return guide 29 that forms a pair of feedback flow paths 27, 28 for returning to the ejection port side of the nozzle 21 is provided along the outer peripheral portion of the. A pair of discharge passages 31 and 32 are formed between the outlet portions of the feedback flow passages 27 and 28 and the outlet portion 12 by the back surface of the return guide 29 and the main body 10. In addition, the nozzle 21
The pressure guiding holes 33, 34 are provided in the vicinity of the ejection port of the piezoelectric film sensor 35 for detecting the pressure difference between the pressure guiding hole 33 and the pressure guiding hole 34 (see FIG. 2). (Not shown) is provided.

FIG. 1 is a block diagram showing the configuration of the circuit portion of the flow meter shown in FIG. As shown in this figure, the flow meter receives the output signal of the flow sensor 30, and outputs a signal having a substantially linear relationship with the flow rate. An averaging circuit 41 as an averaging means for averaging the output signal of the circuit 40, and an A / D for analog-digital (hereinafter referred to as A / D) conversion of the output signal of the averaging circuit 41.
The converter 42, an analog amplifier 43 that amplifies the output signal of the piezoelectric film sensor 35, and a waveform shaping circuit 44 that waveform-shapes the output of the analog amplifier 43 to generate a pulse. The flow meter further inputs the respective outputs of the A / D converter 42 and the waveform shaping circuit 44, and displays a flow rate calculation unit 45 for calculating the flow rate and the integrated flow rate, and the integrated flow rate calculated by the flow rate calculation unit 45. The display unit 46 for controlling the flow rate, the flow rate calculating unit 45 controls the shutoff valve 17 by controlling the shutoff valve 17 by driving the solenoid 18, and the flow rate calculating unit 45 controls the flow sensor 3 according to the flow rate.
0 and a sensor switching unit 48 that switches the operating state of the piezoelectric film sensor 35. The flow rate calculation unit 45, the shutoff valve control unit 47, and the sensor switching unit 48 are configured by, for example, a microcomputer.

In the flowmeter shown in FIG. 1, the flow sensor 30 measures in a small flow rate range, and the piezoelectric film sensor 35 is used.
Measures in a large flow rate range, and both sensors 30, 35
The measurement areas of are partially overlapped. The sensor switching unit 48 is
The operation states of the flow sensor 30 and the piezoelectric film sensor 35 are switched according to which sensor the flow rate is in.

Further, the shut-off valve control section 47, for example, when the flow rate calculation section 45 detects a flow rate of a predetermined amount or more, or a predetermined flow rate for a predetermined time or more, the solenoid 18 is operated.
Is operated to shut off the gas by closing the opening 16 with the shutoff valve 17.

FIG. 3 shows the linearizing circuit 40 shown in FIG.
3 is a circuit diagram showing an example of the configuration of FIG. The linearize circuit 40 has two operational amplifiers 51 and 52. The inverting input terminal of the operational amplifier 51 is connected to the input terminal 53 of the linearizing circuit 40 via the resistor R ₁ . A series circuit of a resistor R ₂ , a DC battery V ₂ and a diode D _{2 and} a series circuit of a resistor R ₃ , a DC battery V ₃ and a diode D ₃ are connected in parallel at both ends of the resistor R _1. There is. The positive electrodes of the DC batteries V ₂ and V ₃ are arranged on the input end 53 side, and the anodes of the diodes D ₂ and D ₃ are arranged on the input end 53 side. Also,
The non-inverting input terminal of the operational amplifier 51 is grounded, and the output terminal and the inverting input terminal are connected via a resistor R ₄ . In addition,
When the voltages of the DC batteries V ₂ and V ₃ are expressed as V ₂ and V ₃ ,
These voltages have a relationship of V ₂ <V ₃ .

The output terminal of the operational amplifier 51 is a resistor R.
It is connected to the inverting input terminal of the operational amplifier 52 via ₅ . The non-inverting input terminal of the operational amplifier 52 is grounded, and the output terminal and the inverting input terminal are connected via a resistor R ₆ . The output terminal of the operational amplifier 52 is connected to the output terminal 54 of the linearization circuit 40.

The characteristics of the linearize circuit 40 shown in FIG. 3 will be described with reference to FIG. FIG. 4 shows the relationship between the input voltage V _I at the input terminal 53 and the output voltage V _O ′ of the operational amplifier 51. In this figure, the voltages of the DC batteries V ₂ and V ₃ are represented as V ₂ and V ₃ . As shown in this figure, when the input voltage V _I is in the range of 0 to V ₂ , the diodes D ₂ and D ₃ are turned off, so that no current flows through the resistors R ₂ and R ₃ . Thus, the operational amplifier 51, the resistance value of the resistor _{R 1, R 4 R 1,} R 4
Then, it becomes an anti-phase linear amplifier with a gain of −R ₄ / R ₁ . Next, when the input voltage V _I is in the range of V ₂ to V ₃ , the diode D ₂ is turned on and a current flows through the resistor R ₂ .
Therefore, the resistor R ₁ and the resistor R ₂ are in parallel on the input side of the operational amplifier 51, so that the gain is increased. Further, when the input voltage V _I becomes V ₃ or more, the diodes D ₂ and D ₃ are turned on and a current flows through the resistors R ₂ and R ₃ . Therefore,
On the input side of the operational amplifier 51, the resistors R ₁ , R ₂ and R ₃ are in parallel, so that the gain is further increased. In this way, the output voltage V _O ′ of the operational amplifier 51 becomes equal to the input voltage V _I
Has a non-linear relationship with.

The operational amplifier 52 and the resistors R ₅ and R ₆ are negative phase linear amplifiers, and output voltage V _{O of the} operational amplifier 51.
′ Is inverted and the gain is adjusted as necessary to obtain the output voltage V _O.

This linearizing circuit 40 is shown in FIG.
The input voltage V _I having a non-linear relationship with the flow rate Q as shown in FIG. 5 is input, and the output voltage V ₀ having a substantially linear relationship with the flow rate Q as shown in FIG. It is what is output. Therefore, depending on the relationship between the flow rate Q and the input voltage V _I , the resistance values of the resistors R _{1 to} R ₆ and the DC batteries V ₂ , V
The voltage of ₃ is appropriately selected so that the relationship between the input voltage V _I and the output voltage V ₀ of the linearization circuit 40 is appropriately set. In FIG. 3, the relationship between the input voltage V _I and the output voltage V _O ′ of the operational amplifier 51 is changed by increasing the number of series circuits of resistors, DC batteries and diodes connected to both ends of the resistor R ₁ . The curve can be more smoothly approximated, and the relationship between the flow rate and the output voltage V ₀ can be made closer to a straight line.

FIG. 6 is a circuit diagram showing an example of the configuration of the averaging circuit 41 in FIG. This averaging circuit 41 includes a resistor R connected in series between an input terminal 61 and an output terminal 62.
₁₁ , a resistor R _12, and a capacitor C whose one end is connected to the middle point of these resistors R ₁₁ and R _{12 and} whose other end is grounded.
Have ₁ and. The averaging circuit 41 absorbs a high frequency component of the input voltage and outputs an averaged output voltage.

Next, the operation of the flowmeter according to this embodiment will be described.

The gas received from the inlet portion 11 of the flowmeter enters the nozzle 21 through the first gas passage 14, the opening 16 and the second gas passage 15 in this order. Nozzle 21
The output signal of the flow sensor 30 arranged in the passage of
A / D via the linearize circuit 40 and the averaging circuit 41
It is converted into digital data by the converter 42 and input to the flow rate calculation unit 45. When the flow rate is within the measurement area of the flow sensor 30, the flow rate calculation unit 45 determines that the flow sensor 3
Based on the output of 0, the flow rate corresponding to the flow velocity of the gas passing through the passage of the nozzle 21 is calculated.

Here, the output signal of the flow sensor 30 is
Although it has a non-linear relationship with the flow rate as shown in FIG. 5 (a), the linearizing circuit 40 outputs a signal having a substantially linear relationship with the flow rate as shown in FIG. 5 (b). To be done. Then, the averaging circuit 41 averages the output signals of the linearizing circuit 40. in this way,
The signal obtained by averaging the signals having a substantially linear relationship with the flow rate corresponds to the true average value of the flow rate, unlike the case of averaging the signals having a nonlinear relationship with the flow rate. Therefore, there is no error in the flow rate calculated by the flow rate calculation unit 45.

The gas passing through the nozzle 21 becomes a jet flow and is jetted from the jet outlet. The gas ejected from the ejection port flows along one side wall due to the Coanda effect. Here, it shall first flow along the side wall 23. The gas flowing along the side wall 23 is further fed back to the feedback channel 2
After returning to the ejection port side of the nozzle 21, the discharge passage 3
It is discharged from the outlet portion 12 via 1 At this time, the gas ejected from the nozzle 21 is changed in direction by the gas flowing through the feedback flow path 27, and now flows along the other side wall 24. The gas is further returned to the ejection port side of the nozzle 21 via the feedback flow path 28, and is discharged from the outlet section 12 via the discharge path 32. Then, the direction of the gas ejected from the nozzle 21 is changed by the gas flowing through the feedback flow passage 28, and the side wall 23 and the feedback flow passage 2 again.
It comes to flow along 7. By repeating the above operation, the gas passing through the nozzle 21 performs fluidic oscillation which alternately flows through the pair of feedback flow paths 27 and 28. The frequency and period of this fluidic oscillation have a correlation with the flow rate.

The fluidic oscillation is generated by the piezoelectric film sensor 35.
Detected by. When the flow rate is in the measurement area of the piezoelectric film sensor 35, the flow rate calculation unit 45 causes the waveform shaping circuit 44 to operate.
The flow rate is calculated based on the period of the pulse output from.

The display unit 46 displays the integrated flow rate calculated by the flow rate calculation unit 45. In addition, the shutoff valve control unit 47
Is operated by the solenoid 18 to close the opening 16 by the shutoff valve 17 when the flow rate calculation unit 45 detects a flow rate of a predetermined amount or more or when the flow rate is detected for a predetermined time or more. The supply of gas to the downstream side is stopped.

As described above, according to this embodiment, the output signal of the flow sensor 30 is output by the linearizing circuit 40.
The signal having a substantially linear relationship with the flow rate is used, the signal is averaged by the averaging circuit 41, and the flow rate calculation unit 45 calculates the flow rate from the averaged signal. It is possible to reduce the influence of the fluctuation of the flow velocity due to the pressure fluctuation or the like without causing an error in

Further, in this embodiment, since the linearizing means and the averaging means are realized by circuits, the load of software is reduced as compared with the case where these are realized by software of a microcomputer.

FIG. 7 is a block diagram showing the circuit configuration of a flowmeter according to the second embodiment of the present invention. The present embodiment is an example in which the linearization means and the averaging means are realized by software using a microcomputer. As shown in FIG. 7, in this embodiment, the linearization circuit 4 in the first embodiment is used.
0 and the averaging circuit 41 are not provided, and the output signal of the flow sensor 30 is converted into digital data by the A / D converter 42 and then input to the microcomputer 70. Microcomputer 70
Is a linearization calculation unit 71 as a linearization unit that inputs the output data of the A / D converter 42 and outputs data that has a substantially linear relationship with the flow rate, and the output of the linearization calculation unit 71. An average value calculator 72 as an averaging means for averaging the data, and a flow rate calculator that inputs the output data from the average value calculator 72 and the output signal of the waveform shaping circuit 44 to calculate the flow rate and the integrated flow rate. 45, the shutoff valve control unit 47 and the sensor switching unit 4 similar to those in the first embodiment.
8 is provided.

The linearization calculation unit 71 may have, for example, a relationship between the input and the output as a table, and by referring to this table, the data having a substantially linear relationship with the flow rate may be obtained. Data having a substantially linear relationship with the flow rate may be obtained by using the arithmetic expression of Further, the average value calculator 72 holds, for example, a plurality of input data within a predetermined time, calculates the average value of these input data, and outputs the calculated average value.

Other configurations and operations are similar to those of the first embodiment.

According to this embodiment, as in the case of the first embodiment, it is possible to reduce the influence of the fluctuation of the flow velocity due to the pressure fluctuation and the like without causing an error in the calculated flow rate, and the linearizing means. Since the averaging means is realized by software using a microcomputer, the relationship between the input and the output in the linearizing means can be set easily and accurately.

The present invention is not limited to the above embodiments, and for example, the flow velocity sensor is not limited to the one having a heat generating portion and two temperature sensors, but has, for example, one heat generating portion. Even if the flow velocity is obtained from the power supplied to the heat generating part required to keep the temperature (resistance) of the part constant, or the heat generating part is heated with a constant current or constant power and the flow velocity is calculated from the temperature (resistance) of the heat generating part good.

[0037]

As described above, according to the output correction device for the flow velocity sensor and the flowmeter of the present invention, the linearizing means outputs a signal having a substantially linear relationship with the flow rate, and this signal is output. Since the averaging means is used for averaging, the averaged signal corresponds to the true average value of the flow rate, and there is no error in the calculated flow rate. Is effective.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a flowmeter according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of the flow meter according to the first embodiment of the present invention.

3 is a circuit diagram showing an example of a configuration of a linearization circuit in FIG.

FIG. 4 is a characteristic diagram showing characteristics of the linearizing circuit shown in FIG.

5 is a characteristic diagram showing an operation of the linearizing circuit shown in FIG.

FIG. 6 is a circuit diagram showing an example of a configuration of an averaging circuit in FIG.

FIG. 7 is a block diagram showing a circuit configuration of a flowmeter according to a second embodiment of the present invention.

FIG. 8 is a characteristic diagram showing a relationship between a flow rate and an output of a flow velocity sensor.

[Explanation of symbols]

 30 flow sensor 40 linearization circuit 41 averaging circuit 45 flow rate calculation unit 46 display unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuharu Oishi 1-1-2 Kawana, Fujisawa-shi, Kanagawa Yamatake Honeywell Co., Ltd. Fujisawa Plant

Claims (2)

[Claims] 1. A linearizing means for inputting an output signal of a flow velocity sensor, which outputs a signal corresponding to a flow velocity of a fluid, and outputting a signal having a substantially linear relationship with a flow rate, and an output of the linearizing means. And an averaging means for averaging the signals. 2. A flow velocity sensor that outputs a signal according to the flow velocity of the fluid, and linearization means that inputs the output signal of the flow velocity sensor and outputs a signal that has a substantially linear relationship with the flow rate, A flowmeter, comprising: an averaging means for averaging the output signals of the linearizing means; and a flow rate computing means for computing a flow rate based on the signal averaged by the averaging means.