JPH0827201B2 - Turbine flow meter flow rate correction device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate correction device for a turbine type flow meter, and more particularly to a flow rate correction device for a turbine type flow meter that corrects the instrumental error of the turbine type flow meter.

The turbine type flow meter detects the rotation of the turbine according to the flow rate of the fluid to be measured and detects the rotation detection pulse (hereinafter simply referred to as "pulse").
Is generated, and the flow rate is measured from the pulse interval or frequency.

2. Description of the Related Art Conventionally, a turbine type flow meter has been used in a relatively high-speed rotation region, but when it is applied to a household gas meter for home use, the rotation speed varies widely from 1 to 20000 rpm.

When the number of revolutions changes over a wide range in this way, the relationship between the meter constant (the number of revolutions per unit flow rate) and the flow rate has an instrumental difference that greatly changes depending on the flow rate as shown by a characteristic curve I shown in FIG. .

Conventionally, as a means for correcting the above instrumental error, Japanese Patent Laid-Open No. 52-
As described in Japanese Patent No. 153768 and Japanese Patent Laid-Open No. 56-58622, the flow rate range is divided into n, and the meter constants K _{0 to} K _n for each divided flow rate range are memorized and the flow rate measured at the pulse interval or pulse frequency is used. There is a first method of reading out a predetermined meter constant and performing correction.

Further, as described in JP-A-58-223021, the differences ΔK _{1 to} ΔK _n between the meter constant of each flow rate and the meter constant K _{0 of} FIG. 7 are stored and the difference is corrected according to the flow rate. There is a second method.

Further, as described in JP-A-58-66820, there is a third method in which the characteristic curve of the flow rate and the meter constant is approximated by a broken line and the meter constant at each flow rate is obtained using the broken line equation.

Problems to be Solved by the Invention In the first and second conventional methods, when the flow rate range is wide and the curvature of the characteristic curve is large, the number of divisions is n in order to reduce the instrumental error.
And the storage capacity of the correction data increases. Especially when it is necessary to store several characteristic curves in order to cover the deviation of each flow meter, the above storage capacity is a single chip.
There is a problem that the internal memory of the microcomputer is insufficient, and it becomes indispensable to add an external memory, which is uneconomical. Of course, it is possible to select the characteristic curve for each flow meter and write the stored data, but in this case, it takes time and is not practical.

Further, in the third conventional method, since the meter constant is calculated from the flow rate by the equation, complicated calculation is required. For this reason, since the flow rate is obtained by measuring the pulse interval or frequency, there is a problem that the meter constant cannot be calculated by an ordinary microcomputer when the flow rate is short and the flow rate is large. Although it is possible to calculate the meter constant by using a high-speed computing microcomputer, the current consumption increases remarkably, which is not suitable for a gas meter or the like that requires explosion-proof property.

Further, in all of the first to third methods, the flow rate is measured at either the pulse interval or the frequency.

The pulse interval is measured by the number of clock counts between pulses, for example, 18000 rpm (1 rotation 3.33 mse
To obtain 1% accuracy in c), a clock with a period of 30 μsec is required. When the pulse interval of 1 rpm is measured with this clock, the number of counts becomes 2 × 10 ⁶ , and the counter configuration is extremely uneconomical.

The pulse frequency can be measured, for example, by the number of pulses for 1 second during high-speed rotation, but it takes 2000 seconds to measure with an accuracy of 1% at 3 rpm, for example, and the measurement time becomes long.

The present invention has been made in view of the above points, and provides a flow rate correction device for a turbine type flow meter that requires a small storage capacity for correction data, low power consumption, and highly accurately corrects instrumental error in a short time. The purpose is to do.

Means for Solving the Problems The device of the present invention detects the rotation of a turbine rotating according to the flow velocity of a fluid to be measured, generates a pulse, and measures the flow rate of the fluid to be measured from the pulse.

The pulse interval measuring means measures the pulse interval of the pulse.

The pulse measuring means measures the number of pulses per unit time of the pulse.

The flow rate determination means determines whether the flow rate is a low flow rate range, a medium flow rate range, or a high flow rate range from the pulse interval or the number of pulses.

The low flow rate region flow rate correction means obtains a corrected flow rate according to the pulse interval using the characteristic curve of the pulse interval and the flow rate when the flow rate is in the low flow rate region.

The medium flow rate correction amount generation means obtains a correction amount according to the number of pulses per unit time using the characteristic curve of the number of pulses per unit time and the flow rate when the flow amount is within the medium flow rate region.

The calculation means adds the corrected flow rate output from the low flow rate area flow rate correction means in the low flow rate area every time the pulse comes in, and obtains a constant flow rate every time the pulse comes in in the middle flow rate area and the high flow rate area. Then, the correction amount output from the medium flow amount correction amount generation means is added every unit time in the medium flow amount region, and the instrumental error is corrected by different correction methods for the low flow amount region, the medium flow amount region, and the high flow amount region. Get the flow rate.

Effect In the present invention, in a low flow rate region where the pulse interval is relatively long, a corrected flow rate is calculated from the characteristic curve of the pulse interval and the flow rate, and in the medium flow rate region where the pulse interval is short. A correction amount corresponding to the number of pulses per unit time is calculated from the characteristic curve of the number of pulses per unit time and the flow rate. In addition, the flow rate corrected in the low flow rate area and the constant flow rate in the middle and high flow rate areas are added each time a pulse arrives, and the above correction amount is added in the middle flow rate area to add the low flow rate area, the middle flow rate area, and the high flow rate area. The flow rate in which the instrumental error is corrected is obtained by a different correction method.

In this way, depending on the pulse interval, when this is short, the calculation is simplified, the calculation can be performed with low power consumption, the number of divisions in the flow rate range is small, and the correction data storage capacity is small. Can be done.

First, the principle of the device of the present invention will be described. Turbine rotation frequency f and meter constant K (that is, rotation speed per unit flow rate)
The relationship with and is represented by the characteristic curve II shown in FIG. A low flow rate region of the flow range rotational frequency f ₃ or less in the present invention, the flow rate range within less than f ₄ exceeds the rotational frequency f _3, is divided into a high flow rate range of the rotation frequency f ₄ above.

In the low flow rate region, the characteristic curve II is represented by the turbine rotation period, that is, the pulse interval T and 1 / K as shown by the broken line in FIG. 2 (B), and the straight lines IIIa, IIIb, III Approximate by c.

1 / K = ai · T + bi (1) (where i is a subscript indicating each line III a, III b, III c) 1 / T ₀ = f ₀ , 1 / T ₁ = f ₁ , 1 / T ₂ ＝ f ₂ , 1 / T ₃ ＝ f ₃ , 1 / T ₄ ＝
f ₄ Since the pulse interval T is long in the low flow rate region (1)
The calculation of the formula can be easily realized.

In the medium flow rate range, the number of revolutions P per second is obtained, and the flow rate Q is obtained from the following equation using the reference data constant K ₀ and the positive correction amount ΔQ _P corresponding to the number of revolutions P.

Q = P / K ₀ + ΔQ _P (2) The correction amount ΔQ _P is the difference between the apparent flow rate P / K ₀ and the true flow rate Q obtained at the rotational speed _P of 1 second, and is a value measured in advance. is there. Note that P / K ₀ can be obtained by adding 1 / K ₀ for each pulse.

In the high flow rate region, the change of the meter constant due to the flow rate is very small and can be ignored. Therefore, 1 / K ₀ is added to each pulse to obtain the flow rate.

 FIG. 1 shows a block diagram of an embodiment of the apparatus of the present invention.

In the figure, in the turbine unit 1, the rotor 3 is supported in the outer shell 2 by the flow path controllers / bearings 4 and 5, and the fluid flows in from the inflow port 6 and flows out from the outflow port 7. Magnets 9 and 10 are attached to the rotor 3, and the rotation of the rotor 3 is detected by a magnetic sensor 11, and this detection signal is supplied to a pulsing circuit 12, where the waveform is shaped and the rotor 13 is rotated per revolution. One pulse is output.

The pulse interval measuring unit 20 measures the number of clock counts between incoming pulses to obtain a pulse interval, and the pulse number measuring unit 21 counts the number of incoming pulses per second. The flow rate determination and control unit 22 determines whether the flow rate range is low, medium, or high based on the pulse interval and the number of pulses, and the memory control unit 23 and the correction calculation units 24 and 25 according to the determination result.
And the operation mode of the unit flow rate generation unit 26 is switched.

The correction data memory 27 stores the coefficients ai and bi of the equation (1) according to each of several characteristic curves that cover the deviation of each flow meter, and the correction data memory 28 stores the correction amount ΔQ of the equation (2). _P is stored according to each of the above-mentioned several characteristic curves.

Which of the above several characteristic curves is selected is determined by whether any one of the terminals 29a to 29d of the characteristic designating section 29 is connected by using a jumper wire.
The instruction signal output from 29 is supplied to the memory control unit 23.

The memory control unit 23 generates an address corresponding to the pulse interval or the number of pulses in accordance with the instruction signal and the operation mode designated by the flow rate determination and control unit 22 and supplies it to the memories 27 and 28.

In the low flow rate region, the correction calculation unit 24 operates under the control of the flow rate determination and control unit 22, and the equation (1) is calculated using the pulse interval from the pulse interval measurement unit 20 and the coefficients ai, bi from the correction data memory 27. Then, the obtained flow rate is supplied to the unit flow rate generation unit 26.

The correction calculator 25 operates in the medium flow rate range, and the pulse number measurement unit
In synchronization with 21, the correction amount ΔQ _P from the correction data memory 28 is supplied to the unit flow rate generation unit 26 as it is from the correction data memory 28.

The unit flow rate generation unit 26 adds the flow rate from the correction calculation unit 24 every time a pulse from the pulsing circuit 12 comes in the low flow rate region by the flow rate determination and control of the control unit 22, and makes the correction calculation in the medium flow rate region. The correction amount ΔQ _P from the unit 25 is added, and 1 / K ₀ is added every time a pulse from the pulse circuit 12 arrives in the medium and high flow rate range. Whenever the added value exceeds the unit flow rate, the integration counter
The unit flow rate pulse having the value "1" indicating the unit flow rate is supplied to 31 and the unit flow rate is subtracted from the self added value.

The integration counter 31 counts the unit flow rate pulse and displays the count value on the display 22.

When the turbine rotates at the boundary of each flow rate region, the operation of the correction calculation units 24 and 25 and the unit flow rate generation unit 26 becomes unstable.Therefore, a hysteresis characteristic is added to the flow rate determination and the flow rate determination of the control unit 22. There is.

The operation of the apparatus shown in FIG. 1 can be executed by a low power consumption 4-bit microcomputer such as the μPD7500 series, which will be described.

FIG. 3 shows a state transition diagram of the microcomputer.
In the figure, the microcomputer is
The initialization process 50 is executed to enter the stop mode 51. In the stop mode 51, the system clock for program execution is stopped to enter the low power consumption state. The release of the stop mode 51 is performed by the internal timer interrupt 52 generated in the program timer cycle and the flow rate pulse interrupt 53 generated by the arrival of a pulse for each rotation of the turbine, respectively, in order of priority. The flow rate pulse processing 55 is executed.

The initialization processing 50 has the configuration shown in FIG. First, the stack pointer is set to the final address of the internal RAM (step 57), and the mode in which the internal timer interrupt and the external interrupt are possible is selected (step 58). Next, the signal level of the I / O port for outputting the unit flow rate pulse is set to a predetermined value (step 59), and the internal RAM is cleared or set to a predetermined value (step 60). Then, the internal timer period is set to, for example, 1000 msec, the internal timer is started (step 61), and the process is ended.

The internal timer processing 54 has the configuration shown in FIG. First,
Set the counter TCNT, which is a timer for pulse interval measurement, to "1"
Incremented (step 64), correction method flag
Determine whether LFLG is "1" (step 6)
Five). This flag LFLG is set to "1" in the low flow rate range and "0" in the medium and high flow rate range. If the flag LFLG is "1", the pulse counter PCNT is cleared to "0" in step 74 and the process ends. If the flag LFLG is "0", the pulse counter PCNT that counts the number of pulses per second is Figure 2 (A)
It is compared with the pulse frequency f ₃ shown in (step 66). If the pulse counter PCNT becomes large, step as a low flow rate region.
At 76, the flag LFLG is set to "1" and the process proceeds to step 69. When the pulse counter PCNT is f ₃ or less, the pulse counter PCNT is compared with the pulse frequency f ₄ (step 67), and in the high flow rate range where the pulse counter PCNT is f ₄ or less, the correction method flag HFLG is set to “1” in step 77. Set and proceed to step 74. The correction method flag HFLG is set to "0" in the low and medium flow rate range and "1" in the high flow rate range.

Flag HF in medium flow rate range where pulse counter PCNT is less than f ₄
LG is set to "0" (step 68), and it is determined whether the characteristic curve C1 is selected (step 69). Here, n characteristic curves, C1 to Cn, are prepared.
Similar to 29, the selection of any one of the characteristic curves is specified.

If the characteristic curve C ₁ is selected, the correction amount ΔQ _P in the middle flow rate range corresponding to the value of the pulse counter PCNT in step 70 ₁ .
Generates an address to read from the ROM (step 71),
The read correction amount ΔQ _P is transferred to the variable KVAL in RAM (step 72), and the value of the variable KVAL is added to the integration counter TVAL (step 73). Step 70 for the characteristic curves C _{2 to} C _n
The same process is performed for each of ₂ to 70 _n .

After this, in step 74, the pulse counter PCNT is cleared to zero, the processing ends, and the mode shifts to the stop mode 51.

The flow rate pulse processing 55 has the configuration shown in FIG. First,
The pulse counter PCNT is incremented by "1" (step 79), and the flow rate range is discriminated from the flags LFLG, HFLG (steps 80, 93). Integration counter TVAL in high flow rate range
1 / K ₀ is added to (step 95), 1 / K ₀ is added to the integration counter TVAL in the medium flow rate range (step 94), and then the process proceeds to step 89.

In the low flow rate region, the pulse interval T is calculated from the value of the counter TCNT (step 81) and the characteristic curve is determined (step 8).
2). If it is the characteristic curve C ₁ , then step 83 ₁ in FIG.
A polygonal line corresponding to any of the straight lines IIIa, IIIb, and IIIc shown in (4) is selected (step 84). According to the result, 1 / K _L is calculated in steps 85 to 87. 1 / K _L is obtained by the equation (1). It should be noted that although the broken line is described here as including three straight lines, it may be m (m is an integer of 4 or more) straight lines. Similar processing is performed on the characteristic curves C _{2 to} C _{n in} steps 83 _{2 to} 83 _n .

Thereafter was added the 1 / K _L the integrating counter TVAL in step 88, compared with the values TAN corresponding value of the counter TVAL the unit flow rate (step 89), a unit flow rate pulse if unit flow rate than I / 0 Output from port (step 90), counter TVA
The value TAN is subtracted from the value of L (step 91), the process is terminated, and the stop mode 51 is entered.

In this way, since the instrumental error is corrected by the optimum method according to the pulse interval, it is possible to perform highly accurate correction even if the rotational speed variation range of 1 to 20000 rpm is wide, and the storage capacity of the correction data stored in advance is small. Complete.

Moreover, since the calculation is simplified when the pulse interval is short, the calculation circuit consumes less power, the explosion-proof property is improved, and the device using the battery power source can be downsized and have a long life.

Further, since a plurality of characteristic curves are stored in advance and any one of them is selected by the characteristic designating unit 29 in each device, it is not necessary to install the device.

EFFECTS OF THE INVENTION As described above, according to the flow rate correction device of the turbine type flow meter of the present invention, the storage capacity of the correction data is small, the power consumption is low, the explosion proof is improved, and the device is highly accurate in a short time. The difference can be corrected, which is extremely useful in practice.

[Brief description of drawings]

1 is a block diagram of an embodiment of the device of the present invention, FIG. 2 is a characteristic diagram for explaining a correction operation of the device of the present invention, FIG. 3 is a state transition diagram of a microcomputer applied to the device of the present invention, FIG. 4, FIG. 5, and FIG. 6 are respectively flowcharts of the microcomputer, and FIG. 7 is a diagram showing characteristic curves of the turbine meter. 1 ... Flowmeter, 20 ... Pulse interval measurement unit, 21 ... Pulse number measurement unit, 22 ... Flow rate determination and control unit, 23 ... Memory control unit, 24,25 ... Correction calculation unit, 26 ... Unit flow rate generator, 2
7,28 …… Correction data memory, 31 …… Integration counter, 32…
… Display, 57-95 …… Step.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Mikiro Toriyabe 2-31-12 Nishiikebukuro, Toshima-ku, Tokyo Pacific Mejiro Mansion 502 (72) Inventor Keiichi Miyamoto 1-17-20 Kitamachi, Kokubunji, Tokyo ( 72) Inventor Teruhisa Kojima 1-7-16 Weir, Tama Ward, Kawasaki City, Kanagawa Prefecture (72) Masayuki Komaki 1188 Oshidate, Inagi City, Tokyo (72) Inventor Hiroshi Morita 3-2-95 Chiyosaki, Nishi Ward, Osaka City, Osaka Prefecture Gas Co., Ltd. (72) Inventor Takatoshi Murakami 3-2-95 Chiyosaki, Nishi-ku, Osaka City, Osaka Prefecture Osaka Gas Co., Ltd. (72) Inventor Yasushi Sato, 507-1 Shinhocho, Tokai City, Aichi Prefecture Toho Gas Co., Ltd. 72) Inventor Yasuo Oto, 502-1 Shinhocho, Tokai City, Aichi Prefecture Toho Gas Co., Ltd.

Claims (1)

[Claims] 1. A flow rate correction device for a turbine type flow meter, which detects a rotation of a turbine rotating according to a flow velocity of a fluid to be measured, generates a pulse, and measures a flow rate of the fluid to be measured from the pulse. A pulse interval measuring means for measuring the pulse interval of the pulses, a pulse number measuring means for measuring the number of pulses of the pulse per unit time, and the pulse interval or the number of pulses in the low flow rate region or the medium flow rate region. Flow rate determining means for determining whether the flow rate is in a high flow rate range or a high flow rate range, and a low flow rate determining means for obtaining a corrected flow rate according to the pulse interval using the characteristic curve of the pulse interval and the flow rate when the flow rate is in a low flow rate range. Flow rate range flow rate correction means, and when the flow rate is in the medium flow rate range, a medium flow rate range correction amount generation method for obtaining a correction amount according to the pulse number per unit time using the characteristic curve of the pulse number per unit time and flow rate Means and low flow in the low flow rate region The corrected flow rate output by the regional flow rate correction means is added for each arrival of the pulse, a constant flow rate is added for each arrival of the pulse in the middle flow rate region and the high flow rate region, and the A calculation unit that adds the correction amount output from the medium flow rate correction amount generation unit for each unit time to obtain a flow rate in which the instrumental error is corrected by different correction methods in the low flow rate region, the medium flow rate region, and the high flow rate region. A flow rate correction device for a turbine type flow meter, comprising: