JPH07190830A - Flow rate measurement method - Google Patents

Abstract

(57) [Abstract] [Purpose] Weighing error in the vicinity of the measurement switching of the parent-child type flow meter that measures the minute flow rate range by intermittently driving the thermal type flow sensor and measures the higher flow rate range with the fluidic oscillation element. To reduce. Further, erroneous measurement due to periodic pulsation generated in the fluidic oscillation element due to external vibration is eliminated. Furthermore, hunting for switching is eliminated. [Structure] During switching determination when the flow rate increases, each measured value of the flow sensor and fluidic oscillation element is stored in a buffer of a computer, and the value of the buffer is added to the integrated value according to the switching determination result. During the switching determination when the flow rate is decreasing, the lack of the flow rate pulse of the fluidic oscillating element is determined, and the deficiency of measurement is complemented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas flow rate measuring method.

[0002]

2. Description of the Related Art A parent-child type gas flow meter in which a thermal type flow sensor is used to measure a minute flow rate range and a fluidic oscillation element is used to measure a further flow rate range by an electronic circuit. (For example, a gas meter) is known (JP-A-1-308921).

[0003]

In this parent-child type flow meter, the thermal type flow sensor is driven intermittently to measure the flow rate. Therefore, the flow rate increases and the measurement is switched from the flow sensor to the fluidic oscillation element. There is a problem that there is a deficiency in measurement during the period and during the period when the flow rate is reduced and the measurement is switched from the fluidic oscillation element to the flow sensor, which causes a measurement error during the switching determination.

Further, due to the influence of mechanical vibrations / impacts from the outside and the pulsating pressure in the pipe (for example, the pulsation in the pipe when the gas engine heat pump provided in the city gas supply pipe is operated), the gas (for example, gas) is changed. There is also a problem that when a fluidic oscillation element outputs a signal having continuous periodicity, the measurement is switched to the fluidic oscillation element and the measurement is erroneously performed even though it does not flow.

Therefore, an object of the present invention is to provide a gas flow rate measuring method capable of solving these problems.

[0006]

In order to achieve the above object, a flow rate measuring method of the present invention uses a flow sensor in a minute flow rate range and a gas flow rate measurement using a fluidic oscillation element in a higher flow rate range. In the method, a switching determination procedure at the time of switching the flow rate measurement from the flow sensor to the fluidic oscillation element and at the time of switching the flow rate measurement from the fluidic oscillation element to the flow sensor is defined as follows. 1. Switching judgment procedure when switching the flow rate measurement from the flow sensor to the fluidic oscillator. 1.1 At the rising time t ₀ of the flow pulse of the fluidic oscillator, the integration of the flow pulse of the flow sensor is stopped. 1.2 Flow sensor drive cycle from T _s to a short T ′
_The measurement value Q ′ _s is calculated by changing every _s and stored in the first buffer B _s . 1.3 At the same time, the measured value by the flow pulse of the fluidic oscillator is stored in the second buffer B _D. 1.4 Flow rate Q of the fluidic oscillator is measured and the flow rate Q is switched to the fluidic oscillator.
_The number of continuous pulses having a period T _U or less corresponding to _U is counted. 1.5 When the number of continuous pulses is less than the constant value d, at that point, the value of the first buffer B _s is added to the integrated value,
The drive cycle of the flow sensor is returned to the original drive cycle T _s , and the flow sensor measures the flow rate. 1.6 the number of continuous pulses when more than a predetermined value d, the short cycle T 'flow sensor drive number by _s is a predetermined number of times S
At time t ₁ has elapsed _{only, B s ≧ α · Q L} · T '
_{When s} · S, the value of the second buffer B _D is added to the integrated value, and thereafter the flow rate is measured by the flow rate pulse of the fluidic oscillator. However, α is a safety factor for not making a mistake in the determination in consideration of the measurement error, and 0 <α ≦ 1.

[0007] when the _{B s <α · Q L ·} T 's · S, the first
The value of the buffer B _s is added to the integrated value, the drive cycle of the flow sensor is returned to the original drive cycle T _s , and the flow sensor measures the flow rate. 1.7 By the time t ₁ at 1.6, the second buffer when the period of flow pulses fluidic is below measurement switching flow Q _L corresponding to the period T _L which in flow sensor, at which time The value of B _D is added to the integrated value, the drive cycle of the flow sensor is returned to the original drive cycle T _s , and the flow sensor measures the flow rate. 2. Flow measurement switching judgment procedure from fluidic oscillator to flow sensor. 2.1 Measure the period of the flow pulse of the fluidic oscillator every pulse. 2.2 The period T _n of the flow pulses, the measurement switching flow Q period T _L following T _n ≦ corresponding to _L to flow sensor
When T _L , the fluidic flow rate measurement is continued.

[0008] period T _n of the flow pulse of fluidic oscillating element, when the period T _L is greater than T _n> T _L corresponding to the measurement switching rate Q _L of the flow sensor, the period T _L
Monitoring the flow rate pulses to a constant value m times the time m · T _L. During the monitoring of the flow rate pulse, the flow rate for one pulse is added to the integrated value for each cycle T _L. 2.3 Period T of flow pulse of fluidic oscillator
when _n is a constant value m times the period T _L of the following time m · T _L,
That is, when T _n ≦ m · T _L , the next flow rate pulse is monitored for the time until the period T _L.

Time T of the next flow pulse_{n + 1}But the flow
Measurement switching period T to sensor_LThe following T_{n + 1}≤T_Lof
, Continue to measure the flow rate with the fluidic oscillator.
It Also, the cycle T of the next flow rate pulse_{n +1}But Froce
Measurement switching period T to sensor_L Greater T_{n + 1}> T_L
In case of, switch to flow rate measurement to the flow sensor. 2.4 Period T of flow pulse of fluidic oscillator
_nIs the switching cycle T to the flow sensor_LWhen the fixed value m times
Interval m · T_LIf it is larger, flow meter with flow sensor
Switch to measurement.

[0010]

[Operation] During determination of flow rate measurement switching from the flow sensor to the fluidic oscillating element, each weighing value is stored in the buffer, and the value of the buffer is added to the integrated value according to the determination result, so that the weighing Avoid defects.

[0011] During flow measurement switching determination from fluidic oscillator to the flow sensor, if the flow rate pulse period of the fluidic oscillator is extended by chipping and other pulses, the period corresponding to the measured switching rate Q _L of the flow sensor The flow rate for one pulse is added to the integrated value for each _TL to complement the measurement defect.

Further, the drive interval of the flow sensor is shortened,
By increasing the accuracy of the flow rate measurement by the flow sensor and making the determination, integration due to an erroneous signal of periodicity from the fluidic oscillator is avoided. In this way, an error caused by the determination of only the continuous flow pulse of the fluidic oscillator is avoided.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a gas flow meter used for carrying out the flow rate measuring method of the present invention. Reference numeral 1 denotes a piezoelectric film sensor, which detects fluid vibration of a fluidic oscillation element (not shown) and converts it into an electric signal. It is a sensor that does. Reference numeral 2 is an amplification / waveform shaping circuit that amplifies / waveforms the electric signal of the piezoelectric film sensor 1 and converts it into a rectangular pulse signal. Reference numeral 3 is a piezoelectric film sensor circuit unit having the piezoelectric film sensor 1 and the amplification / waveform shaping circuit 2. Reference numeral 4 is a cycle measuring circuit for measuring the cycle of the flow rate pulse signal (flow rate pulse signal of the fluidic oscillation element) from the piezoelectric film sensor circuit section 3 for each pulse.

A thermal type flow sensor 5 converts the gas flow velocity into an analog electric signal. An analog-digital conversion circuit 6 has a function of converting an analog electric signal from the flow sensor 5 into an electric pulse signal train having a pulse number proportional to the flow rate. Reference numeral 7 is a flow sensor circuit section having a flow sensor 5 and an analog / digital conversion circuit 6.

Reference numeral 8 is a control circuit, which is a microcomputer 1.
In response to the command of 0, the power supply to the flow sensor 5 and the clock signal supply to the analog / digital conversion circuit 6 for analog / digital conversion are controlled.

Reference numeral 9 denotes a counter which temporarily stocks the electric pulse (signal B) output from the analog / digital conversion circuit 6 for input to the microcomputer 10.

Reference numeral 10 denotes a microcomputer, which has a signal A from the piezoelectric film sensor circuit section 3 and a signal B from the counter 9.
And are calculated according to the cycle of the signal A measured by the cycle measuring circuit 4, the flow rates are integrated, and the integrated flow rate is displayed on the display unit 11.

The flow of measurement switching by the microcomputer 10 will be described below with reference to the timing chart of FIG. 2 and the flowchart of FIG. Step 101: Normally, in the minute flow rate range, the flow sensor 5 is driven at a constant cycle T _s (for example, 6 seconds), and the flow rate is measured and integrated (before time t _{0 in} FIG. 2A).

Step 102: The presence / absence of a flow pulse (signal A) of the fluidic oscillation element is determined by the rising edge of the signal A (time t _{0 in} FIG. 2A). Step 103: If it is determined that the flow pulse (signal A) of the fluidic oscillator is present, the flow sensor 5 suspends the integration.

Step 104: The flow rate is measured with high accuracy by changing the driving interval of the flow sensor 5 to a short cycle T _'S (for example, 0.1 seconds) (time t ₀ -in FIG. 2A). t ₁ ).

Step 105: Short period T '_SEvery
Measurement value Q'in the flow sensor 5_STo the first buffer B_S
Add to. Step 106: Signal pulse of fluidic oscillator
Period T of signal (signal A) _nTo a fluidic oscillator
Measurement switching flow rate Q_U(In No. 3 gas meter, 142
Cycle T equivalent to [l / h])_U(No. 3 gas meter
Is about 220 [ms]) or less. Cycle T_n
Is the cycle T of this condition_UIf longer, move to step 114
It

Step 107: Fluidic oscillator
Cycle T of flow pulse (signal A) of child _nMeets this condition
If so, the measured value K at the fluidic oscillator_dThe first
Buffer B of 2_DAdd to.

Step 108: Count the number n of continuous flow rate pulses (signal A) having a period of T _U or less. Step 109: It is determined whether or not the number n of continuous pulses has reached a constant value d (for example, 8) (time t _{0 to} t _{1 in} FIG. 2).

Step 110: Fluidic oscillator
To the first and second buffers for weighing the child and the flow sensor 5
Continue to add. Step 111: Flow pulse of fluidic oscillator
Period T of signal (signal A) _nSwitches to flow sensor 5
Flow rate Q_L(135 [l / h] in No. 3 gas meter
Cycle T corresponding to_L(About No. 3 gas meter
240 [ms]) or less is determined. Cycle T_nIs this condition
Cycle T_LIf longer, go to step 121
Buffer B_DValue is added to the integrated value to
Return to flow measurement at SA5.

[0025] Step 112: driving interval T 'count number of driving times is a constant flow sensor 5 at _S S (e.g. 20
Times). When the number of driving times reaches S, the process proceeds to step 113.

Step 113: A constant coefficient for the measured value during the period in which the flow sensor 5 is driven S times at short T _'S intervals, that is, the value of the first buffer B _S , and the switching flow rate Q _L to the fluidic oscillator. The value obtained by multiplying by α (for example, α≈1) is compared to determine whether the flow rate pulse (signal A) of the fluidic oscillation element is an erroneous signal of periodicity.

[0027] The judgment result is _{B S <α · Q L ·} T 'S · S
If the condition is not satisfied, the process proceeds to step 114. Step 114: Add the value of the first buffer B _S to the integrated value, and return to the normal flow rate measurement by the flow sensor 5.

[0028] Step 115: it is determined in step 113, the value of the first buffer B _S is a constant value α · Q _L · T _'S
If it is S or more, the value of the second buffer B _D is added to the integrated value.

Steps 116 and 117: Fluid edit
Cycle T of the flow pulse (signal A) of the oscillation element_nIs flow
Measurement switching flow rate Q to sensor 5_LPeriod T corresponding to
_LIf it is less than (about 240 [ms]), fluidic
Continue weighing with the oscillator. Cycle T _LIf it is larger,
Move to step 118.

Step 118: Monitor the period of the fluidic flow pulse (signal A) and add the measured value for one pulse to the integrated value at each time T _L as the period becomes longer,
The deficiency of measurement is complemented (Fig. 2 (b)).

Step 119: Fluidic oscillator
Cycle T of flow pulse (signal A) of child _nBut the flow sensor
Measurement switching flow rate to 5 Q_LPeriod T corresponding to_LConstant value of
m times (for example, m = 2) mT_LDetermine if
If the conditions are not met, move to step 101
Switch to flow rate measurement at SA5.

Step 120: Fluidic oscillator
Cycle T of flow pulse (signal A) of child _nBut m ・ T_LLess than
If so, the cycle T of the next flow rate pulse_{n + 1}Is T_LIs
If it meets the conditions, go to step 117,
Continue measuring the flow rate with the Ruydic oscillator. The conditions
If not satisfied, move to step 101, flow sensor
Switch to flow rate measurement in 5.

FIG. 4 shows the instrumental error in the vicinity of the measurement switching flow rate, and it is clear that the embodiment of the present invention is greatly improved over the prior art.

[0034]

According to the present invention, during the measurement switching determination from the flow sensor to the fluidic oscillation element, the measured value for each period is stored in the buffer, and after the determination is confirmed, the value of either buffer is set as the integrated value. As a result, the loss of weighing is avoided. Further, when the measurement is switched from the fluidic oscillating element to the flow sensor, even if the flow rate pulse is missing, the error is improved because it is compensated for. In this way, the measurement error is reduced.

Even if a periodic error signal (continuous pulse) is output from the fluidic oscillation element due to mechanical vibration / impact from outside the pipe, pulsating pressure due to pressure fluctuation in the pipe, or the like, at the same time. Since the flow rate measurement is performed by making the drive interval of the flow sensor short, the erroneous signal of the fluidic oscillation element can be prevented from being measured, and the measurement error can be reduced in this respect as well.

Furthermore, even if the flow rate fluctuates in the vicinity of the flow rate at which the measurement is switched from the fluidic oscillation element to the flow sensor, the flow rate pulse is complemented and the measurement at the fluidic oscillation element is continued. Frequent occurrence can be suppressed, an increase in electric power required to drive the flow sensor can be suppressed, and hunting of the switching operation can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a gas flow meter used for carrying out a flow rate measuring method of the present invention.

2 is a timing chart of the gas flow meter of FIG.
(A) shows the measurement switching from the flow sensor to the fluidic oscillation element, and (b) shows the measurement switching from the fluidic oscillation element to the flow sensor.

FIG. 3 is a flowchart of an embodiment of the present invention.

FIG. 4 is an instrumental characteristic diagram.

[Explanation of symbols]

 1 Piezoelectric film sensor 5 Flow sensor 10 Microcomputer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazumi Onui 9-10, Misonodai, Fujisawa City, Kanagawa Prefecture (72) Inventor Shigenori Okamura 4-1-2 1-2 Hiranocho, Chuo-ku, Osaka City Osaka Gas Co., Ltd. (72) Inventor Yukio Kimura 507-2 Shintakaracho, Tokai-shi, Aichi Toho Gas Co., Ltd. Research & Development Center (72) Inventor Masahito Naganuma 1-270, Sennen-ku, Nagoya, Aichi Aichi Clock Electric Co., Ltd. Within

Claims (1)

[Claims] 1. A method for measuring a gas flow rate, wherein a flow sensor is used in a minute flow rate range and a fluidic oscillation element is used in a flow rate range higher than the flow rate range. A flow rate measurement method that defines the switching determination procedure when switching the flow rate measurement from the oscillator to the flow sensor as follows. 1. Switching judgment procedure when switching the flow rate measurement from the flow sensor to the fluidic oscillator. 1.1 At the rising time t ₀ of the flow pulse of the fluidic oscillator, the integration of the flow pulse of the flow sensor is stopped. 1.2 Flow sensor drive cycle from T _s to a short T ′
_The measurement value Q ′ _s is calculated by changing every _s and stored in the first buffer B _s . 1.3 At the same time, the measured value by the flow pulse of the fluidic oscillator is stored in the second buffer B _D. 1.4 Flow rate Q of the fluidic oscillator is measured and the flow rate Q is switched to the fluidic oscillator.
_The number of continuous pulses having a period T _U or less corresponding to _U is counted. 1.5 When the number of continuous pulses is less than the constant value d, at that point, the value of the first buffer B _s is added to the integrated value,
The drive cycle of the flow sensor is returned to the original drive cycle T _s , and the flow sensor measures the flow rate. 1.6 the number of continuous pulses when more than a predetermined value d, the short cycle T 'flow sensor drive number by _s is a predetermined number of times S
At time t ₁ has elapsed only if the _{B s ≧ α · Q L ·} T 's · S, a second buffer B
The value of _D is added to the integrated value, and then the flow rate is measured by the flow rate pulse of the fluidic oscillator. However, α is a safety factor for not making a mistake in the determination in consideration of the measurement error, and 0 <α ≦
1. When _{B s <α · Q L ·} T 's · S, the value of the first buffer B _s is added to the integrated value, return the drive cycle of the flow sensor based on the drive period T _s, the flow rate at the flow sensor To measure. 1.7 By the time t ₁ at 1.6, the second buffer when the period of flow pulses fluidic is below measurement switching flow Q _L corresponding to the period T _L which in flow sensor, at which time The value of B _D is added to the integrated value, the drive cycle of the flow sensor is returned to the original drive cycle T _s , and the flow sensor measures the flow rate. 2. Flow measurement switching judgment procedure from fluidic oscillator to flow sensor. 2.1 Measure the period of the flow pulse of the fluidic oscillator every pulse. 2.2 The period T _n of the flow pulses, the measurement switching flow Q period T _L following T _n ≦ corresponding to _L to flow sensor
When T _L , the fluidic flow rate measurement is continued. Period T of flow pulse of fluidic oscillator
_n it is, when the period T _L is greater than T _n> T _L corresponding to the measurement switching rate Q _L of the flow sensor, for monitoring the flow rate pulse to a predetermined value m times the time m · T _L of the period T _L. During the monitoring of the flow rate pulse, the flow rate for one pulse is added to the integrated value for each cycle T _L. 2.3 Period T of flow pulse of fluidic oscillator
when _n is a constant value m times the period T _L of the following time m · T _L,
That is, when T _n ≦ m · T _L , the next flow rate pulse is monitored for the time until the period T _L. Time T of the next flow pulse
_{When n + 1} is Tn _{+ 1} <= _TL which is the measurement switching period _TL to the flow sensor or less, the flow rate measurement by the fluidic oscillation element is continued. Also, the cycle T of the next flow rate pulse
_{When n + 1} is T _{n + 1} > T _L which is larger than the measurement switching period T _L to the flow sensor, the flow sensor is switched to flow rate measurement. 2.4 When the cycle T _n of the flow pulse of the fluidic oscillator is larger than the time m · T _{L which} is a fixed value m times the cycle _TL for switching to the flow sensor, the flow sensor is switched to flow rate measurement.