JPH0835865A - Gain correction device for thermal velocity sensor for fowmeter - Google Patents

Abstract

PURPOSE:To enable gain correction which is more accurate as a whole by increasing the chance of gain correction. CONSTITUTION:A correction processor 50 sets a plurality of different conditions in tolerable range of flow rate fluctuation in the flow range measured with both a flow sensor 30 and a piezoelectric film sensor 35 and judges whether the flow rate fluctuation based on the output of the flow sensor 30 is in the tolerable range or not. At the first step when the flow fluctuation is judged to be within the torelable range, the gain of the flow sensor 30 is corrected with the flow rate obtained based on the piezoelectric film sensor 35 and judges the relation between the input and output in the gain correction circuit 41.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate meter using a fluidic flow rate meter and a thermal type flow rate sensor in combination, and relates to a gain correction device for a thermal type flow rate sensor for a flow rate meter for correcting the gain of the thermal type flow rate sensor.

[0002]

2. Description of the Related Art As a flow meter used for a gas meter or the like, one using a thermal type flow velocity sensor is known. 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.In the flow meter using this thermal type flow velocity sensor, Is calculated 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, the output of the thermal type flow velocity sensor varies depending on the temperature and the like. Therefore, conventionally, in a flow meter that uses a fluidic flow meter and a thermal flow velocity sensor together, as shown in, for example, Japanese Patent Laid-Open No. 3-96817, measurement is performed by both a sensor that detects fluidic oscillation and a thermal flow velocity sensor. When a flow rate range for performing the flow rate is set, and the flow rate is within this flow rate range and the flow rate fluctuation is minute, the output signal of the thermal type flow velocity sensor and this output signal are output based on the measurement value by the sensor that detects fluidic oscillation. The relationship with the flow rate (which is referred to as the gain of the thermal type flow velocity sensor in the present invention) calculated based on the above is corrected.

Here, an example of a conventional gain correction method for a thermal type flow velocity sensor will be described with reference to FIGS. In the following description, the sensor that detects fluidic oscillation will be referred to as a piezoelectric film sensor, and the thermal flow velocity sensor will be referred to as a flow sensor.

As shown in the flow chart of FIG. 4, in the conventional gain correction method for a flow sensor, it is first judged whether or not the piezoelectric film sensor is measuring the flow rate (step S201), and if it is measuring (Y). Acquires the measured flow rate using the piezoelectric film sensor (step S202). Next, it is determined whether this measured flow rate is within the corrected reference flow rate range (step S20).
3). The corrected reference flow rate range is a flow rate range in which measurement is performed by both the piezoelectric film sensor and the flow sensor, for example, 250
~ 400 liters / hour. When the measured flow rate is within the corrected reference flow rate range (Y), the flow sensor measures the flow rate (step S204).

The operation of flow rate measurement using the piezoelectric film sensor and the flow sensor will be described with reference to FIG. Figure 5
As shown in (a), the output of the piezoelectric film sensor is pulsed by a waveform shaping circuit or the like. The flow rate calculation part of the flow meter is
For example, 12 seconds are counted from the rise of a predetermined pulse, and the time t (sec) until the rise of the first pulse after that,
The number of pulses in 12 + t seconds is measured, and the integrated flow rate Q in 12 + t seconds is calculated based on the time t and the number of pulses.
_FD is calculated, and the cumulative flow rate Q _FD ′ per 6 seconds is calculated by the following formula.

[0007]

[Formula 1] Q _FD ′ = {6 / (12 + t)} × Q _FD

The flow rate calculation unit of the flow meter further determines the instantaneous flow rate based on the integrated flow rate Q _FD ′ per 6 seconds, and when the instantaneous flow rate is within the corrected reference flow rate range (step S203; Y). 12 seconds after the rising edge of the predetermined pulse
For example, 3 seconds after the lapse of + t seconds, the driving of the flow sensor is started as shown in FIG. As shown in this figure, the flow sensor is intermittently driven, for example, every 6 seconds.

Returning to FIG. 4, when the flow rate is measured by the flow sensor (S204), it is determined whether the flow rate measured by the flow sensor is within the corrected reference flow rate range (step S205). This correction reference flow rate range is set in step S203.
It is the same as the corrected reference flow rate range in, and the judgment is made again to confirm that the flow rate has not changed significantly. When the measured flow rate is within the corrected reference flow rate range (Y), it is determined whether or not the fluctuation of the measured flow rate using the flow sensor within the predetermined time is within the flow rate fluctuation range (step S206). The flow rate fluctuation range is, for example, within ± 2.5% of the average value of the measured flow rate within a predetermined time. If it is within the flow rate fluctuation range (Y), a sensitivity change rate described later is calculated (step S207), the correction table is updated based on this sensitivity change rate (step S208), and the process is ended. If the piezoelectric film sensor is not measuring the flow rate in step S201 (N), and if it is not in the corrected reference flow rate range in step S203 (N), step S205.
If it is not within the correction reference flow rate range in (N) and if it is not within the flow rate fluctuation range in step S206 (N), the process is ended as it is.

Next, the rate of change in sensitivity will be described with reference to FIG. FIG. 6 shows the relationship between the output of the flow sensor and the measured flow rate using the flow sensor. As shown in this figure, the straight line representing the relationship between the output of the flow sensor and the measured flow rate using the flow sensor changes around the fixed point b _n on the horizontal axis representing the output of the flow sensor. The gain correction of the flow sensor is to change the slope of this straight line based on the measured flow rate using the piezoelectric film sensor so that the measured flow rate using the flow sensor and the measured flow rate using the piezoelectric film sensor match. . Here, the output of the flow sensor is P
_{At FS} , if the measured flow rate using the flow sensor before gain correction is Q _C and the measured flow rate using the piezoelectric film sensor is Q _n , the slope a _n of the straight line before gain correction is obtained by the following equation. .

[0011]

[Number 2] _{a n = Q C / (P} FS -b n)

Similarly, the slope a _n ′ of the straight line after the gain correction so that the measured flow rate using the flow sensor and the measured flow rate using the piezoelectric film sensor are matched is obtained by the following equation.

[0013]

## EQU3 ## a _n ′ = Q _n / (P _FS −b _n ).

When the rate of change in sensitivity is defined as r = a _n ′ / a _n , from the above two equations, r = Q _n / Q _C , and a _n
′ Is calculated by the following formula.

[0015]

## EQU4 ## a _n ′ = ra _n = (Q _n / Q _C ) a _n

The correction table showing the input / output relation in the gain correction circuit is updated based on the slope a _n ′ of the straight line after the gain correction obtained as described above (step S208).

[0017]

However, in the conventional gain correction method of the thermal type flow velocity sensor, the gain correction is not performed when the flow rate fluctuation is large due to the disturbance such as the pressure fluctuation of the gas. Therefore, there is a problem that an error in the measured flow rate is likely to occur.

The present invention has been made in view of the above problems, and an object thereof is to increase the chances of gain correction and to perform more accurate gain correction as a whole. To provide a gain correction device.

[0019]

A gain correction device for a thermal type flow velocity sensor for a flow meter according to the present invention measures a flow rate by using a fluidic oscillation detection sensor for detecting fluidic oscillation and a thermal type flow velocity sensor in combination. Flow rate calculation means used for a flow meter to calculate the flow rate based on the output of the fluidic oscillation detection sensor and the flow rate based on the output of the thermal type flow velocity sensor within a predetermined flow rate range, and the allowable range of fluctuation of the flow rate are different. A plurality of conditions are set, and in order from the condition with the narrowest allowable range, the fluctuation of at least one of the flow rate based on the output of the fluidic oscillation detection sensor and the flow rate based on the output of the thermal type flow velocity sensor, which is obtained by the flow rate calculation means, is within the allowable range. It was determined based on the output of the fluidic oscillation detection sensor when it was first determined that the flow rate fluctuation was within the allowable range. Using the amounts, in which a gain correction means for correcting the gain of a thermal flow sensor.

In this gain correction device for a thermal type flow velocity sensor for a flow meter, the flow amount calculation means causes the flow amount based on the output of the fluidic oscillation detection sensor and the flow amount based on the output of the thermal type flow velocity sensor to be within a predetermined flow amount range. Is calculated. Then, the gain correction means sets a plurality of conditions with different allowable ranges of flow rate fluctuations, and the flow rate and the thermal equation based on the output of the fluidic oscillation detection sensor obtained by the flow rate calculation means in order from the condition with the narrowest allowable range. Based on the output of the fluidic oscillation detection sensor, it is determined whether at least one fluctuation of the flow rate based on the output of the flow velocity sensor is within the allowable range, and when the fluctuation of the flow rate is first determined to be within the allowable range. The gain of the thermal flow sensor is corrected using the obtained flow rate.

[0021]

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 including a gain correction device for a thermal type flow sensor for a flowmeter according to an 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, a first gas flow channel 14 is formed between the partition wall 13 and the inlet portion 11, and a second gas flow channel 15 is provided between the partition wall 13 and the outlet portion 12. Are formed. An opening 16 is provided in the partition wall 13, and the first gas flow path 14 is provided.
A shutoff valve 17 capable of closing the opening 16 is provided therein. A solenoid 18 is fixed to the outside of the main body 10, and a plunger 19 of the solenoid 18 penetrates a side wall of the main body 10 and is joined to the shutoff valve 17. In addition, the plunger 1 between the shutoff valve 17 and the main body 10
A spring 20 is provided around 9 and biases the shutoff valve 17 toward the opening 16 side.

In the second gas passage 15, there is provided a nozzle 21 which allows the gas received from the inlet 11 to pass therethrough to generate a jet flow. A rectifying member 22 for regulating the flow of gas is provided on the upstream side of the nozzle 21. In addition, 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 portion and two temperature sensors arranged upstream and downstream of the heat generating portion,
Two temperature sensors are used to obtain the flow rate corresponding to the flow velocity from the power supplied to the heat generating part required to keep the difference in temperature detected by the two temperature sensors constant, or to heat the heat generating part with a constant current or constant power. The flow rate is obtained from the difference in temperature detected by.

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 has a gain correction circuit 41 for correcting the gain of the flow sensor 30 and an A for analog-digital (hereinafter referred to as A / D) conversion of an output signal of the gain correction circuit 41.
/ D converter 42, analog amplifier 43 for amplifying the output signal of the piezoelectric film sensor 35, and this analog amplifier 43
Waveform shaping circuit 4 that waveform-shapes the output of
4 and. The flow meter further includes an A / D converter 42.
And a flow rate calculation unit 45 that inputs each output of the waveform shaping circuit 44 and calculates a flow rate and an integrated flow rate, and this flow rate calculation unit 45.
A display unit 46 for displaying the integrated flow rate calculated by
An operation state of the flow sensor 30 and the piezoelectric film sensor 35, which is controlled by the flow rate calculation unit 45 and drives the solenoid 18 to control the shutoff valve 17, and the flow rate calculation unit 45, which is controlled by the flow rate calculation unit 45. And a sensor switching unit 48 for switching between.

The flow meter further includes a correction processing section 50 for performing gain correction processing based on the flow rate obtained by the flow rate calculation section 45 and controlling the gain correction circuit 41. In the gain correction processing performed by the correction processing unit 50, the flow sensor 3
In the flow rate range in which the flow rate is measured using both 0 and the piezoelectric film sensor 35, a plurality of conditions having different allowable ranges of flow rate variation are set, and the flow rate based on the output of the flow sensor 30 is set in order from the narrowest allowable range. Of the flow sensor 30 by using the flow rate obtained based on the output of the piezoelectric film sensor 35 at the time when the fluctuation of the flow rate is first determined to be within the permissible range. Correct the gain.
The gain correction circuit 41 and the correction processing section 50 constitute the gain correction means in the present invention. Further, the gain correction circuit 41, the flow rate calculation unit 45, and the correction processing unit 50 constitute the gain correction device of this embodiment. The flow rate calculation unit 45,
The shutoff valve control unit 47, the sensor switching unit 48, and the correction processing unit 50 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 predetermined flow rate or more, or when the predetermined flow rate is detected 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.

Next, the main operation of the flowmeter shown in FIGS. 1 and 2 will be described.

The gas received from the inlet part 11 of the flow meter enters the nozzle 21 through the first gas flow path 14, the opening 16, the second gas flow path 15 and the rectifying member 22 in this order.
When the flow rate is in the measurement area of the flow sensor 30, the flow rate calculation unit 45 corresponds to the flow rate of the gas passing through the passage of the nozzle 21 based on the output of the flow sensor 30 arranged in the passage of the nozzle 21. Calculate the flow rate to be applied.

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.
Is 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.

Next, the operation of the gain correction processing in the correction processing section 50 will be described with reference to the flowchart of FIG.

In this gain correction processing, first, the measured flow rate using the piezoelectric film sensor 35 is acquired from the flow rate calculation unit 45, and it is determined whether this measured flow rate is within the corrected reference flow rate range (step S101). The corrected reference flow rate range is a flow rate range in which the flow rate is measured using both the flow sensor 30 and the piezoelectric film sensor 35, and is, for example, 180 to 400 liters / hour. If the measured flow rate is not within the correction reference flow rate range (N), the gain correction processing ends. If the measured flow rate is within the correction reference flow rate range (Y), it is determined whether or not one hour has passed since the previous gain correction (step S1).
02). When 1 hour has not elapsed (N), the gain correction processing is ended. If one hour has passed (Y),
The flow rate calculation unit 45 measures the flow rate using both the flow sensor 30 and the piezoelectric film sensor 35 (step S10).
3). The flow rate measurement using the flow sensor 30 is, for example, 6
The measurement is performed 5 times at an interval of 30 seconds, and the flow rate measurement using the piezoelectric film sensor 35 is performed for 30 seconds, for example. Next, it is determined whether the difference between the flow rate measured using the flow sensor 30 and the flow rate measured using the piezoelectric film sensor 35 is less than 2% (step S104). 2%
When it is less than (Y), the gain correction processing is ended.

If the difference between the measured flow rates is not less than 2% in step S104 (N), the variation in the measured flow rate using the flow sensor 30 is less than 2% as the first condition of the allowable range of flow rate fluctuation. It is determined whether or not (step S105). The variation in the measured flow rate is, for example, the difference between the maximum value and the minimum value of the measured flow rate obtained by five measurements is 5
The value is divided by the average value of the measured flow rate for each time. If the variation in the measured flow rate is less than 2% (Y), the gain correction is performed (step S106). This gain correction is based on the measured flow rate using the piezoelectric film sensor 35 so that the measured flow rate using the flow sensor 30 matches the measured flow rate using the piezoelectric film sensor 35, as described with reference to FIG. Then, the slope of the straight line representing the relationship between the output of the flow sensor 30 and the measured flow rate using the flow sensor 30 is changed. Then, according to the relationship between the output of the flow sensor 30 and the measured flow rate using the flow sensor 30 thus determined,
The input / output relationship in the gain correction circuit 41 is determined. Next, the timer that counts one hour is reset (step S107), and the gain correction process ends.

If the variation in the measured flow rate is not less than 2% in step S105 (N), the flow rate calculating section 45 measures the flow rate again using both the flow sensor 30 and the piezoelectric film sensor 35 (step S108). ). The flow rate measurement using the flow sensor 30 is performed 30 times at 1 second intervals, and the flow rate measurement using the piezoelectric film sensor 35 is performed for 30 seconds, for example. Note that the flow rate measurement using the flow sensor 30 may be performed 5 times at 6-second intervals, as in step S103. Next, as a second condition of the allowable range of flow rate fluctuation, it is determined whether or not the variation in the measured flow rate using the flow sensor 30 is less than 6% (step S1).
09). When the variation in the measured flow rate is less than 6% (Y)
Performs gain correction (step S106).

In step S109, if the variation in the measured flow rate is not less than 6% (N), the flow rate calculating section 45 measures the flow rate again using both the flow sensor 30 and the piezoelectric film sensor 35 (step S110). ). The flow rate measurement using the flow sensor 30 is performed 30 times at 1 second intervals, and the flow rate measurement using the piezoelectric film sensor 35 is performed for 30 seconds, for example. Note that the flow rate measurement using the flow sensor 30 may be performed 5 times at 6-second intervals, as in step S103. Next, the previous time (step S10
The measurement data of 8) and the measurement data of this time (step S110) are added (step S111), and the flow sensor 30 is used as the third condition of the permissible range of fluctuation of the flow rate for all the measurement data after the addition. There were 8 variations in the measured flow rate
It is determined whether it is less than% (step S109). If the variation in the measured flow rate is less than 8% (Y), the gain correction is performed (step S106). 8% variation in measured flow rate
If it is not less than (N), the timer is reset without performing the gain correction (step S107), and the gain correction process is ended.

The above gain correction processing is repeatedly executed in the processing of the entire flow meter.

As described above, according to the present embodiment, a plurality of conditions having different permissible ranges of flow rate variation are set, and it is determined whether or not the flow rate variation is within the permissible range in order from the condition with the narrowest permissible range. Since the gain correction of the flow sensor 30 is performed at the time when the fluctuation of the flow rate is determined to be within the allowable range, the chances of the gain correction are increased even if there is a disturbance such as a pressure fluctuation of the gas. More accurate gain correction can be performed. Further, when the disturbance is small, the gain correction is performed under the condition that the allowable range is narrow, so that more accurate gain correction can be performed.

The present invention is not limited to the above embodiment,
For example, as the gain correction means, instead of providing the gain correction circuit 41 shown in FIG. 1, the data after A / D conversion may be corrected by a microcomputer or the like.

Further, in the embodiment, it is determined whether or not the fluctuation of the measured flow rate using the flow sensor 30 is within the allowable range, but whether the fluctuation of the measured flow rate using the piezoelectric film sensor 35 is within the allowable range. It is also possible to judge whether or not the fluctuation of the measured flow rate using the flow sensor 30 and the piezoelectric film sensor 3
It may be possible to determine whether or not both the fluctuations in the measured flow rate using 5 are within the allowable range. Further, the plurality of conditions having different allowable ranges of flow rate variation are not limited to three, and may be two or four or more.

Further, the thermal type flow velocity sensor is not limited to the one having the heat generating part and the two temperature sensors, and for example, it has one heat generating part and in order to keep the temperature (resistance) of this heat generating part constant. The flow velocity may be obtained from the power supplied to the required heat generating portion, or the heat generating portion may be heated with a constant current or constant power and the flow velocity may be obtained from the temperature (resistance) of the heat generating portion.

[0044]

As described above, according to the gain correction device for a thermal type flow velocity sensor for a flow meter according to the present invention, a plurality of conditions having different allowable ranges of flow rate variation are set, and the conditions of narrow allowable ranges are set. Sequentially, it was judged whether the fluctuation of the flow rate was within the allowable range, and when the fluctuation of the flow rate was first judged to be within the allowable range, the gain correction of the thermal type flow velocity sensor was performed. Even if there is a disturbance such as the above, the chances of gain correction are increased, and there is an effect that more accurate gain correction can be performed as a whole. Further, when the disturbance is small, the gain correction is performed under the condition that the allowable range is narrow, so that there is an effect that more accurate gain correction can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a flow meter including a gain correction device for a thermal type flow sensor for a flow meter according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a flow meter including a gain correction device for a thermal type flow sensor for a flow meter according to an embodiment of the present invention.

FIG. 3 is a flowchart showing an operation of a correction processing unit in FIG.

FIG. 4 is a flowchart for explaining a gain correction method for a conventional thermal type flow velocity sensor.

FIG. 5 is an explanatory diagram showing a flow rate measuring operation of a piezoelectric film sensor and a flow sensor in a conventional flowmeter.

FIG. 6 is a characteristic diagram showing a relationship between an output of a flow sensor and a measured flow rate using the flow sensor.

[Explanation of symbols]

 30 Flow sensor 35 Piezoelectric film sensor 41 Gain correction circuit 45 Flow rate calculation unit 46 Display unit 50 Correction processing unit

Claims (1)

[Claims] 1. An output of a fluidic oscillation detection sensor within a predetermined flow rate range, which is used in a flow meter for measuring a flow rate by using a fluidic oscillation detection sensor for detecting fluidic oscillation and a thermal type flow velocity sensor in combination. Flow rate calculation means for calculating the flow rate based on the output of the thermal type flow rate sensor and a plurality of conditions with different permissible ranges of flow rate fluctuations are set. Judge whether the fluctuation of at least one of the calculated flow rate based on the output of the fluidic oscillation detection sensor and the flow rate based on the output of the thermal type flow velocity sensor is within the allowable range, and first judge that the fluctuation of the flow rate is within the allowable range. Gain correction means for correcting the gain of the thermal flow sensor using the flow rate obtained based on the output of the fluidic oscillation detection sensor It is provided with a gain correction device of the thermal type flow sensor for a flowmeter, wherein.