JP4758673B2 - Flow meter and flow meter correction method - Google Patents

Description

  The present invention relates to a flow meter for measuring a flow rate of a fluid flowing in a water channel and a flow rate correction method for the flow meter, and more specifically, for example, a flow velocity of a fluid flowing in a sewage channel such as factory waste water, domestic waste water, and rainwater. The present invention relates to a flow meter provided with a flow velocity sensor for measuring the flow rate and a flow rate correction method for the flow meter.

  Various forms are considered as a flow meter for measuring the flow rate of the fluid flowing through the water channel. For example, by measuring the water level by installing a flow meter that calculates the flow rate by multiplying the flow velocity of the fluid flowing through the water channel and the cross-sectional area of the fluid (hereinafter referred to as a surface velocity type flow meter), There is a flow meter for obtaining a flow rate (hereinafter referred to as a PBF flow meter).

  The PBF type flow meter could not measure the flow rate in a state where the water level on the downstream side from the measurement point was raised to such an extent that no limit flow was generated in the flume. Therefore, instead of the PBF type flow meter, or in line with the PBF type flow meter, a surface velocity type flow meter is provided, and the flow rate can be measured even in a fluid flow where the PBF type flow meter cannot measure the flow rate. A total is used. Note that the surface velocity type flow meter requires a flow velocity sensor that obtains the flow velocity of the fluid flowing in the water channel, and some of the flow velocity sensors are obtained using the Doppler effect of ultrasonic waves or electromagnetic waves.

  Patent Document 1 shows an example of an apparatus having a flow rate sensor that obtains a flow velocity using the Doppler effect of ultrasonic waves. FIG. 5 is a diagram showing a configuration of a sensor probe of a surface velocity type flow meter using the flow velocity sensor shown in Patent Document 1, and FIG. 6 is a configuration diagram of a fluid velocity calculation device of Patent Document 1. 5 and 6, reference numeral 80 denotes a sensor probe, 81 denotes a flow velocity sensor attached to the tip of the sensor probe 80, and 82 denotes a pressure-type water level sensor. 83 is a water channel, 84 is a fluid to be measured, and 84 a is an object that flows with the fluid 84. Reference numeral 81a denotes an ultrasonic oscillator that transmits ultrasonic waves to the fluid 84, and reference numeral 81b denotes an ultrasonic receiver close to the ultrasonic oscillator 81a.

  In FIG. 6, 85 is a signal generator for generating an electrical signal of a specific frequency, 86 is an amplifier, 87 is an amplifier for a received signal output from the ultrasonic receiver 81b, and 88 is a difference signal detector. The difference signal detector 88 includes a first mixer (in-phase mixer) 89, a second mixer (quadrature phase mixer) 90 connected to the 90 ° phase shift circuit 90a, low-pass filters 91 and 92 connected to these, and an amplifier. 93, 94.

  Reference numeral 95 denotes a D / A converter that automatically adjusts the gains of the amplifiers 93 and 94. The signals output from the amplifiers 93 and 94 are A / D converted by the A / D converters 96 and 97 and then input to the CPU 99. Then, according to the calculation program set and stored in advance, the average flow velocity is calculated using the weighted average method, and the calculation result is D / A converted by the D / A converter 99a and output.

The arithmetic program executed by the CPU 99 converts the in-phase difference signal output via the amplifier 93 and the quadrature difference signal output via the amplifier 94 into an intensity component and a phase component, respectively, by fast Fourier transform. The calculation using the weighted average method is performed using the Doppler shift of each component. By performing this calculation, a highly reliable average flow velocity S is obtained with high accuracy regardless of measurement conditions without being affected by turbulence or the like.
Japanese Patent No. 2890188

  However, a measurement limit occurs in a flow rate sensor that detects the flow rate of fluid regardless of the type. For example, the flow velocity sensor using the Doppler effect as in Patent Document 1 has the amplifiers 93 and 94 when the flow of the fluid is very slow or the number of objects 84a that reflect ultrasonic waves to the fluid is very small. The gain is increased. At this time, noise generated by the ultrasonic receiver 81b is also amplified, and the measurement error of the flow velocity may increase. Therefore, when the gain is raised to the maximum value by setting the maximum value to the gain, the flow velocity is output as zero, and it may be notified that the flow velocity measurement is impossible.

  Specifically, when the water level rises downstream from the measurement point and the pipe is full by closing the gate or stopping the pump on the downstream side of the water channel, the fluid at the measurement point The error included in the measured value of the flow velocity sometimes increased due to the extremely slow flow. For this reason, even when a surface velocity type flow meter is used, the distance to the water channel closing means (hereinafter referred to as the water channel closing portion) such as a pump or a gate stopped from the measurement point is short, and this water channel closure When the water channel is closed using the means, it may be difficult to measure the flow rate. It should be noted that the flow velocity measurement at the measurement point can be resumed by releasing the closing of the water channel by the water channel closing means.

  However, the water level continues to rise from the moment when the flow velocity measurement becomes impossible until the flow velocity measurement becomes possible again, and the fluid stays downstream from the measurement point (referred to as a retained fluid in this specification). ) May increase. Then, since the staying fluid on the downstream side of the measurement point has already passed through the measurement point, there has been a problem that it cannot be measured even after the flow velocity measurement is resumed.

  The present invention has been made in consideration of the above-mentioned matters, and its purpose is to measure the flow rate according to the volume of the fluid that has passed through the measurement point while the flow velocity measurement at the measurement point is disabled for some reason. A flow meter for correcting a value and a flow correction method for the flow meter are provided.

In order to achieve the above object, a flow meter according to claim 1 is a flow meter provided in a water channel in which a fluid stays when closed by a water channel closing means on the downstream side, and a flow rate sensor provided in the water channel A flow rate measurement unit having a measurement impossibility notification function for notifying that the flow rate measurement using the detection value is impossible, and obtaining the flow rate of the fluid in the water channel using the detection value of the flow rate sensor, and the fluid A water level sensor that detects the water level of the liquid, an area measuring unit that obtains the cross-sectional area of the fluid at the measurement point using the water level, a flow rate computing unit that multiplies the cross-sectional area by the flow velocity to obtain the flow rate of the fluid, and the flow velocity measurement And a stay correction unit that corrects the flow rate by using a change in the water level while the water flow is impossible.

The flow meter according to claim 2 is a flow meter provided in a water channel in which fluid stays when closed by a water channel closing means on the downstream side, and a flow rate sensor provided in the water channel, and a detection value of the flow rate sensor The flow rate of the fluid in the water channel is obtained using a flow rate measurement unit having a measurement impossibility notification function for notifying that the flow rate measurement using the detected value is impossible, and at least the flow rate of the fluid using the flow rate Depending on the difference in volume at the time when the flow rate measurement can be resumed, the flow rate calculation unit to be obtained, the volume measurement unit that measures the volume of the fluid in the water channel downstream from the measurement point, and when the flow velocity measurement is disabled And a retention correction unit that obtains the volume of the staying fluid staying in the water channel while the flow velocity measurement is impossible, and adds a correction according to the volume of the staying fluid to the flow rate. That.

  The volume measuring unit may include a water level sensor that detects a water level and a linearizer that converts the detected water level into a volume according to the shape of the water channel (Claim 3).

  The stay correction unit includes a first storage unit that stores the volume when the flow velocity measurement is disabled, a second storage unit that stores the volume when the flow velocity measurement can be resumed, and the second storage unit. By subtracting the volume memorized in the first memory from the memorized volume, the value corresponding to the volume of the accumulated fluid staying in the water channel downstream from the measurement point was retained while the flow velocity measurement was impossible You may have a subtraction part calculated | required as a correction value, a timer part which measures predetermined time, and an addition part which adds the said stagnation correction value to the said flow volume only for the said predetermined time (Claim 4).

The flow rate correction method for a flowmeter according to claim 5 is provided in a water channel in which a fluid stays when closed by a water channel closing means on the downstream side, and measures the flow velocity and water level of the fluid in the water channel to measure the water level. In the flow meter that calculates the flow rate of the fluid by calculating the cross-sectional area of the measurement point from this and multiplying the cross-sectional area by the flow velocity, the flow rate is corrected by using the change in the water level while the flow velocity cannot be measured properly. It is characterized by doing.

The flow rate correction method for a flow meter according to claim 6 is provided in a water channel in which a fluid stays when closed by a water channel closing means on the downstream side, and measures the flow rate of the fluid by measuring at least the flow velocity of the fluid in the water channel. After measuring and storing the volume of the fluid in the water channel at the time when the flow velocity measurement of the fluid becomes impossible, measure the volume of the fluid in the water channel when the flow velocity measurement can be resumed. The volume of the stored fluid is subtracted from the volume to obtain the volume of the staying fluid staying in the water channel while the flow velocity measurement is impossible, and the flow rate is corrected according to the volume of the staying fluid. .

  According to the water level measured at the measurement point, the volume of the fluid in the channel downstream from the measurement point is obtained, and the volume at the time when the flow velocity measurement becomes impossible is stored in the first storage unit, and the flow velocity measurement can be resumed. The volume at the time is stored in the second storage unit, the volume stored in the first storage unit is subtracted from the volume stored in the second storage unit, The volume of the staying fluid staying in the downstream water channel may be obtained, and a staying correction value proportional to the volume of the staying fluid may be added to the flow rate for a predetermined time.

  When the measured value of the flow velocity becomes equal to or lower than a predetermined first threshold, the flow velocity is set to zero and a flow velocity measurement zero signal indicating that the flow velocity measurement is disabled is generated, and the measured value of the flow velocity is the first threshold value. The flow rate measurement restart signal may be generated indicating that the flow rate measurement using the flow rate measured when the second threshold value is higher than the second threshold value is restarted and that the flow rate measurement has been resumed. .

  According to the first aspect of the present invention, in the surface velocity type flow meter that obtains the flow rate using the flow velocity and cross-sectional area of the fluid at the measurement point, the stagnation of the fluid on the downstream side is poor and the stagnation of the fluid on the downstream side of the measurement unit Even in such a case, the volume of the retained fluid can be accurately obtained by using the change in the water level. In particular, when the pump that draws fluid in the downstream channel stops or when the channel closes due to the gate being closed, the flow velocity at the measurement point decreases significantly, making it impossible to measure the flow rate with the flow rate sensor. However, if the flow rate of fluid that has passed through the measurement point is corrected by the change in the water level while the flow velocity measurement is disabled, a situation where the flow velocity measurement cannot be performed has occurred. However, it is possible to perform accurate flow measurement with appropriate correction.

  For example, the water level is measured both when the flow velocity measurement is disabled (that is, when the flow velocity measurement value becomes zero) and when the flow velocity measurement is resumed, and the flow velocity measurement is performed based on the change in the water level. The volume of the staying fluid that has passed through the measurement point during the period during which the measurement cannot be performed can be obtained, and a predetermined stay correction value can be added to the flow rate after the flow velocity measurement is resumed according to this volume.

  The relationship between the water level and the volume of the staying fluid that stays between the measurement point and the water channel closing part is determined by the shape of the water channel from the measurement point to the water channel closing part (such as the cross-sectional shape and length of the water channel). Storing this relationship in a linearizer or the like in advance is preferable because the water level can be easily converted into the volume of the staying fluid.

  In the invention according to claim 2, in the flowmeter for obtaining the flow rate using at least the flow velocity of the fluid at the measurement point, when the fluid stagnation is poor on the downstream side and the fluid stays on the downstream side of the measurement unit, The flow rate of the fluid can be obtained with high accuracy by using the change in the volume of the fluid in the water channel downstream from the measurement point. In particular, when a water channel closing portion occurs in the downstream water channel and the flow velocity at the measurement point is significantly reduced and the flow velocity sensor cannot measure the flow velocity (that is, when the measured flow velocity value is 0), this flow velocity By correcting the flow rate of the fluid that has passed through the measurement point while the measurement is disabled, by correcting the change in the volume of the fluid in the channel downstream of the measurement point, there is a situation where the flow velocity measurement becomes impossible. Even if it occurs, it is possible to perform accurate correction and correct flow rate measurement.

  When the volume measuring unit has a water level sensor that detects the water level and a linearizer that converts the detected water level into a volume according to the shape of the water channel (Claim 3), the measurement is relatively easy. The volume of fluid in the water channel can be determined using the water level that can be generated. In particular, the relationship between the water level and the volume of the retained fluid that stays between the measurement point and the water channel closure part is determined by the shape of the water channel from the measurement point to the water channel closure part (such as the cross-sectional shape and length of the water channel). By storing this relationship in the linearizer in advance, the water level can be easily converted into the volume of the staying fluid.

  The stay correction unit includes a first storage unit that stores the volume when the flow velocity measurement is disabled, a second storage unit that stores the volume when the flow velocity measurement can be resumed, and the second storage unit. By subtracting the volume memorized in the first memory from the memorized volume, the value corresponding to the volume of the accumulated fluid staying in the water channel downstream from the measurement point was retained while the flow velocity measurement was impossible In the case of including a subtracting unit to be obtained as a correction value, a timer unit for measuring a predetermined time, and an adding unit for adding the stay correction value to the flow rate for the predetermined time (Claim 4), In spite of the configuration, since the stay correction value corresponding to the volume of the staying fluid staying in the water channel downstream from the measurement point can be added to the flow rate, the flow rate can be corrected appropriately.

  In the invention according to claim 5, in the surface velocity type flow meter, a water channel closing portion is generated downstream from the measurement point, and the flow velocity at the measurement point is remarkably reduced. In other words, even if the measured value of the flow velocity becomes 0), the flow rate can be corrected by the change in the water level while the flow velocity measurement is disabled, and more accurate flow rate measurement can be performed. it can. That is, in the normal surface velocity type flow meter, while the flow velocity measurement is disabled, the flow rate output is 0, and the flow rate at the measurement point cannot be accurately obtained. During this time, the flow rate can be measured by changing the water level, and the correction can be made.

  The water level can be measured, for example, both when the flow velocity measurement is disabled and when the flow velocity measurement is resumed, and the flow rate after the flow velocity measurement is resumed can be corrected. The change in the water level is converted into a change in the volume (flow rate) of the staying fluid using a linearizer in which the relationship between the water level and the volume of the staying fluid staying between the measurement point and the water channel closing portion is stored in advance. Is desirable.

  In the invention according to claim 6, in the flowmeter for obtaining the flow rate using at least the flow velocity of the fluid at the measurement point, fluid stagnation occurs on the downstream side of the measurement unit, and the flow velocity at the measurement point is significantly reduced. When the flow velocity measurement by means of becomes impossible (that is, when the measured flow velocity value is 0), both when the flow velocity measurement becomes impossible and when the flow velocity measurement can be performed, By measuring and subtracting the volume of fluid in the water channel, the volume of the retained fluid that has accumulated in the water channel while the flow velocity measurement is disabled can be obtained. Measurements can be made.

  According to the water level measured at the measurement point, the volume of the fluid in the channel downstream from the measurement point is obtained, and the volume at the time when the flow velocity measurement becomes impossible is stored in the first storage unit, and the flow velocity measurement can be resumed. The volume at the time is stored in the second storage unit, the volume stored in the first storage unit is subtracted from the volume stored in the second storage unit, When the volume of the staying fluid staying in the downstream water channel is obtained, and when the stay correction value proportional to the volume of the staying fluid is added to the flow rate for a predetermined time (Claim 7), the water channel downstream from the measurement point A stay correction value corresponding to the volume of the staying fluid staying inside can be easily calculated.

  When the measured value of the flow velocity becomes equal to or lower than a predetermined first threshold, the flow velocity is set to zero and a flow velocity measurement zero signal indicating that the flow velocity measurement is disabled is generated, and the measured value of the flow velocity is the first threshold value. When the flow rate measurement restart signal indicating that the flow rate measurement has been resumed and the calculation of the flow rate using the flow rate measured when the second threshold value is higher than the second threshold value is generated (Claim 8). The period during which the flow rate measurement is impossible can be notified easily and appropriately. That is, the minimum necessary flow rate correction can be performed accurately and appropriately.

  FIG. 1 is a diagram showing a configuration of a water channel in which a flow meter 1 according to a first embodiment of the present invention is installed, FIG. 2 is a diagram showing an example of a sensor probe of the flow meter, and FIG. FIG. 4 is a block diagram showing an example, and FIG. 4 is a diagram for explaining an example of the operation of the flow meter.

  In FIG. 1, 2 is a water channel such as a sewer, 3 is a fluid such as sewage flowing through the water channel 2, and 4 is a pump provided at the downstream end of the water channel. For example, the water channel 2 is an open water channel for allowing the fluid 3 to flow in an open state, and the water level rises when the pump well 2a having a slightly depressed shape so as to install the pump 4 in the downstream portion or when the pump 4 is stopped. Thus, a water reservoir 2b for retaining the fluid 3 is formed.

  Reference numeral 5 denotes a sensor probe of the flow meter 1 and is installed at a predetermined position (measurement point) Pa in the water channel 2. On the other hand, Pb is a downstream end of the water channel 2, that is, a water channel closing portion when the pump 4 is stopped. Further, Le indicates the lowest level of the water level of the flow meter 1, Lf indicates the full water level of the water reservoir 2b, and indicates the highest level that can be corrected by the flow meter 1 according to the present invention. Ll and Lh will be described later. The level of the water level related to the correction calculation by the flow meter 1 is shown.

  The sensor probe 5 may have various configurations. For example, the sensor probe 5 may be configured as shown in FIG. That is, the sensor probe 5 in the present embodiment includes a flow rate sensor 10, a pressure type water level sensor 11, and a signal cable 12 connected to an arithmetic device not shown. In addition, it cannot be overemphasized that this invention is not limited to the structure of the flow velocity sensor 10 and the water level sensor 11 which are shown below.

  The flow velocity sensor 10 is, for example, an ultrasonic reflection method, and includes an ultrasonic oscillator 10a that transmits an ultrasonic wave to the fluid 3 and an ultrasonic receiver 10b that is close to the ultrasonic oscillator 10a. That is, when the ultrasonic wave Us irradiated from the ultrasonic oscillator 10 a is irradiated into the fluid 3, the ultrasonic wave Ur reflected by the object 3 a or the like and subjected to Doppler shift according to the flow velocity S of the fluid 3 is received by the ultrasonic receiver. 10b can be received.

  The water level sensor 11 measures the pressure applied to a sensing unit such as a diaphragm disposed so as to be in contact with the fluid 3, and the water level of the fluid from the position of the sensing unit (represented as a water level for convenience but liquid other than water) ), That is, the water level D is measured. Accordingly, the level Le of the water level 0 is the same level as the height position of the sensing part of the water level sensor 11.

  In FIG. 3, reference numeral 20 denotes an arithmetic unit, and a flow rate measurement unit 21 that obtains the flow rate F of the fluid 3 using the detected value Sa of the flow rate S obtained by the flow rate sensor 10 and the detected value Da of the water level D by the water level sensor 11. And a stay correction unit 22 that corrects the flow rate F obtained by the flow rate measurement unit 21.

  The flow rate measuring unit 21 includes, for example, a flow rate measuring unit 25 that calculates an average flow rate S of the fluid 3 in the water channel 2 using the detected flow rate value Sa, and a disconnection of the fluid 3 at a measurement point using the detected water level Da. An area measuring unit 26 for obtaining the area A and a flow rate calculating unit 27 for obtaining the flow rate F of the fluid 3 by multiplying the obtained flow velocity S by the cross-sectional area A are provided. In addition, since the structure of the said flow velocity measurement part 25 in a present Example is substantially the same as the fluid velocity calculating apparatus shown by patent document 1, description of the detailed structure is abbreviate | omitted.

  The flow velocity measuring unit 25 has a measurement impossibility notification function for notifying that the flow velocity measurement is impossible using the flow velocity detection value Sa. More specifically, for example, when the flow rate of the fluid 3 becomes extremely slow, the flow rate sensor 10 cannot measure the flow rate with good accuracy.

  Therefore, in this embodiment, when the measured value of the flow velocity becomes equal to or less than the predetermined first threshold value Th1 (see FIG. 4), the flow velocity measurement zero signal S1 indicating that the flow velocity measurement becomes impossible by setting the flow velocity S to zero. Has a limit alarm to occur. On the other hand, the calculation of the flow rate F using the flow rate S measured when the measured value of the flow rate S became equal to or higher than the second threshold Th2 higher than the first threshold Th1 was resumed while the flow rate measurement was resumed. There is a limit alarm for generating a flow velocity measurement restart signal S2 indicating. As in the present embodiment, the first threshold value Th1 for detecting that the flow velocity measurement is impossible is set to a value different from the second threshold value Th2 for detecting that the flow velocity measurement has been resumed, and a hysteresis difference therebetween. By providing this, it is possible to prevent a phenomenon such as chattering due to a minute change in the measured value of the flow velocity.

  In the description of the present embodiment, the threshold values Th1 and Th2 are described as the threshold values of the flow velocity measurement values for the sake of simplicity, but the flow velocity measurement unit 25 of the present embodiment is shown in FIG. When the amplifiers 93 and 94 are provided, the upper limit of the gain can be set as a threshold value. In this case, the upper limit of the gain set as the first threshold is lower than the upper limit of the gain set as the second threshold.

  The stay correction unit 22 includes, for example, a linearizer 30 as an example of a volume measurement unit that converts the water level detection value Da into a volume V of the fluid 3 in the water channel 2 between the measurement point Pa and the water channel closing unit Pb. The correction control unit 31 for generating various control signals for performing the stay correction of the flow rate F using the flow velocity measurement zero signal S0 and the flow velocity measurement restart signal S1, and the time t1 when the flow velocity measurement is disabled (FIG. 4), the second storage unit 33 that stores the volume V at the time t2 (see FIG. 4) when the flow velocity measurement is resumed, and the volume stored by the second storage unit 33. It has a subtracting section 34 for subtracting the volume Vl stored in the first storage section 32 from Vh, a changeover switch 35, and an adding section 36.

  The linearizer 30 is adapted to the shape of the water channel 2 such as the cross-sectional shape perpendicular to the flow in the water channel 2 from the measurement point Pa to the water channel closing part Pb and the distance from the measurement point Pa to the water channel closing part Pb shown in FIG. The water level D at the measurement point Pa is converted into the volume V. In the case of the present embodiment, since the water reservoir 2b is formed, the conversion from the water level D to the volume V by the linearizer 30 is performed in accordance with a calibration curve approximated by a broken line.

  Therefore, the calibration curve of the linearizer 30 is appropriately set according to the position where the sensor probe 5 is installed, the shape of the flow channel 2, the distance from the measurement point Pa to the water channel closing part Pb, and the like. The linearizer 30 constitutes a volume measuring unit together with the water level sensor 11.

  The correction control unit 31 includes an arithmetic processing device such as a programmable controller. The correction control unit 31 stores, for example, the volume V at the time t1 when the flow velocity measurement is disabled at the time t1 when the flow velocity measurement zero signal S1 is generated, as the various control signals. In order to store the volume V at the time t2 when the flow velocity measurement is resumed at the time t2 when the flow velocity measurement restart signal S2 is generated in the state where the latch signal La1 and the flow velocity measurement zero signal S1 are generated. The latch signal La2 and a timer control signal Tc for measuring a predetermined time T such as 10 minutes from the time t2 are generated. That is, the correction control unit 31 of this embodiment functions as a timer unit that measures a predetermined time.

  The storage units 32 and 33 temporarily store an analog signal of the volume V output from the volume measuring unit 30 by an analog memory, for example, but store a digital signal indicating the volume V. There may be. The signal stored in the first storage unit 32 is the volume Vl in the water channel 2 from the measurement point Pa to the water channel closing part Pb (volume from the water level level Le to the level Ll) at the time t1 when the flow velocity measurement becomes impossible. Is a signal proportional to. And the signal memorize | stored in the 2nd memory | storage part 33 is the volume Vh (volume from the level Le of the water level to the level Lh) in the water channel 2 from the measurement point Pa to the water channel closure part Pb in the time t2 when the flow velocity measurement restarted. Is a signal proportional to.

  Accordingly, by obtaining the difference between the two volumes Vh and Vl by the subtracting unit 34, the volume Va of the portion shown by hatching in FIG. 1, that is, when the flow velocity measurement is resumed from the time t1 when the flow velocity measurement becomes impossible. The retention correction value R is proportional to the volume Va of the staying fluid 3 ′ staying downstream from the measurement point Pa until t2.

The changeover switch 35 is switched to the subtracting section 34 side while the timer control signal Tc is being generated to supply the stay correction value R, and otherwise the current corresponding to the flow rate 0 of the flow rate measuring section 21 (for example, 4 In the case of a current output of −20 mA, the output is switched to the output unit O side of 4 mA current). Here, to explain with specific numerical values, for example, the volume Va when the span of the flow rate F output from the flow rate measurement unit 21 is 3000 m ³ / h and the staying fluid 3 ′ is accumulated up to the maximum level Lf. It is assumed that the span of the stay correction value R corresponding to is 600 m ³ . At this time, the timer control signal Tc is set to a length obtained by dividing 1 hour = 60 minutes by 3000/600 = 5, that is, 12 minutes. If the signal indicating the flow rate F is a current output of ⁴ to 20 mA, the span signal indicating the span 600 m ³ of the stay correction value R is 20 mA.

Further, when the predetermined time Tc is set as described above, for example, if the volume Va of the staying fluid 3 ′ obtained by the subtracting section 34 is 300 m ³ , the stay correction value R is set to a flow rate of 1500 m ^3. A signal corresponding to / h, that is, a current output of 12 mA.

That is, as shown in FIG. 4, the adder 36 outputs the signal of the flow rate F and the stay correction value R (flow rate in this example) only for a predetermined time Tc after the time t2 when the flow velocity measurement is resumed. And a flow rate F ′ subjected to stay correction by adding a signal of 1500 m ³ / h). Further, when the timer control signal Tc becomes inactive, the changeover switch 35 is switched to the original state, and the signal of the flow rate F and the signal of the stay correction value R are not added by the adder 36. In this way, it is possible to output the flow rate F ′ subjected to the retention correction corresponding to 300 m ³ minutes which is the volume Va of the staying fluid 3 ′. Therefore, the flowmeter 1 of the present invention is corrected with the volume Va of the fluid 3 (retained fluid 3 ′) that has passed through the sensor probe 5 during the period in which the flow velocity measurement is impossible, being corrected in consideration of the volume Va. Can be output.

  In the embodiment described above, the present invention has been described by giving examples of specific numerical values for the stay correction value R span, the flow rate F span, the predetermined time Tc, and the like. It goes without saying that the numerical value of is arbitrarily changed. Further, the magnitude of the stay correction value R is proportional to the volume Va of the stay fluid 3 ′ and is inversely proportional to the length of the predetermined time Tc. It can also be changed according to the water levels Ll and Lh at the time t2 when the restart was possible. That is, the specific numerical values described above are merely examples.

  In the embodiment described above, the configuration of the arithmetic unit 20 will be described with reference to the block diagram shown in FIG. 3 so as to facilitate the description of the present invention, and the amounts A, D, and F obtained using the sensors 10 and 11 will be described. , F ′, R, S, V, Vl, Vh, and control signals S1, S2, La1, La2, and Tc are shown to be transferred. This shows that the influence of the staying fluid 3 'can be corrected sufficiently and sufficiently using the arithmetic device 20 having a very simple configuration.

  However, the present invention is not limited to having the arithmetic unit 20 having a circuit configuration that inputs and outputs the above-described signals. That is, it is of course possible to make the circuit configuration of the arithmetic unit 20 a digital circuit or a hybrid circuit. Moreover, you may make it make a computer perform the arithmetic processing corresponded to the arithmetic unit 20. FIG. At this time, a program for causing the computer to execute the arithmetic processing of the units 25 to 27 and 30 to 36 can be created very easily.

  In addition, in the above-described embodiment, an example in which the change in the water level D is measured using the pressure-type water level sensor 11 is shown, but a water level sensor using ultrasonic waves or a float may be used. Similarly, in the above example, since the volume V of the fluid 3 in the flow path 2 below the measurement point Pa is obtained from the water level D, the linearizer 30 including the water level sensor 11 constitutes the volume measuring unit in this embodiment. However, the present invention is not limited to the configuration of the volume measuring unit 30 described above, and the volume V of the fluid 3 in the flow path 2 below the measurement point Pa is obtained from measurement values other than the water level. Also good.

  Further, in the above-described embodiment, the flow rate measurement is performed by obtaining the volume Va of the staying fluid 3 ′ that has accumulated during the time t1 when the flow velocity measurement is disabled and the change in the water level D at the time t2 when the flow velocity measurement can be resumed. Although the example which correct | amends the flow volume F after having restarted is shown, this invention is not limited to this point. That is, the change in the water level D during the measurement of the flow velocity is measured at a short predetermined time, such as every second, and the change in the volume Va of the staying fluid 3 ′ within the predetermined time is obtained. Thus, the flow rate during which the flow velocity measurement is disabled may be obtained almost in real time. In this case, it is possible to correct the flow rate in real time while the flow rate has to be zero even if the surface velocity type flow rate measurement is performed.

It is a figure which shows the example using the flowmeter which is an example of this invention. It is a figure which shows the structure of a part of said flow meter. It is a figure which shows the structure of the arithmetic unit of the said flow meter. It is a figure explaining the flow volume correction method of the said flow meter. It is a figure which shows an example of a flow velocity sensor. It is a figure which shows the structure of the control circuit of the said flow velocity sensor.

DESCRIPTION OF SYMBOLS 1 Flowmeter 2 Water channel 3 Fluid 3 'Retention fluid 10 Flow rate sensor 11 Water level sensor 22 Retention correction part 25 Flow rate measurement part 26 Area measurement part 27 Flow rate calculation part 30 Volume measurement part (linearizer)
31 Timer part (correction control part)
32 First storage section 33 Second storage section 36 Addition section A Cross section D Water level F Flow rate Pa Measurement point R Residence correction value S Flow rate Sa Detected value of flow rate sensor t1 When flow rate measurement is disabled t2 Flow rate measurement can be resumed Time point Th1 first threshold value Th2 second threshold value V volume Va volume of staying fluid

Claims (8)

A flow meter provided in a water channel in which fluid stays when closed by a water channel closing means on the downstream side;
A flow rate sensor provided in the water channel;
A flow velocity measurement unit having a measurement impossibility notification function for notifying that the flow velocity measurement using the detection value is impossible while obtaining the flow velocity of the fluid in the water channel using the detection value of the flow velocity sensor,
A water level sensor for detecting the water level of the fluid;
An area measuring unit for obtaining the cross-sectional area of the fluid at the measurement point using the water level;
A flow rate calculation unit for determining the flow rate of the fluid by multiplying the flow velocity by a cross-sectional area;
A flowmeter comprising: a stay correction unit that corrects the flow rate using a change in water level while the flow velocity measurement is impossible. A flow meter provided in a water channel in which fluid stays when closed by a water channel closing means on the downstream side;
A flow rate sensor provided in the water channel;
A flow velocity measurement unit having a measurement impossibility notification function for notifying that the flow velocity measurement using the detection value is impossible while obtaining the flow velocity of the fluid in the water channel using the detection value of the flow velocity sensor,
A flow rate calculation unit for obtaining a flow rate of the fluid using at least the flow velocity;
A volume measuring unit that measures the volume of fluid in the water channel downstream from the measurement point;
In accordance with the difference between the volume when the flow velocity measurement is disabled and when the flow velocity measurement can be resumed, the volume of the staying fluid staying in the water channel while the flow velocity measurement is impossible is obtained, and the flow rate is calculated. A flowmeter comprising: a stay correction unit that performs correction according to the volume of the stay fluid.   The flow meter according to claim 2, wherein the volume measuring unit includes a water level sensor that detects a water level and a linearizer that converts the detected water level into a volume according to a shape of a water channel.   The stay correction unit includes a first storage unit that stores the volume when the flow velocity measurement is disabled, a second storage unit that stores the volume when the flow velocity measurement can be resumed, and the second storage unit. By subtracting the volume memorized in the first memory from the memorized volume, the value corresponding to the volume of the accumulated fluid staying in the water channel downstream from the measurement point was retained while the flow velocity measurement was impossible 4. The flow meter according to claim 2, further comprising: a subtracting unit that is obtained as a correction value; a timer unit that measures a predetermined time; and an adding unit that adds the stay correction value to the flow rate for the predetermined time. It is provided in the water channel where the fluid stays when closed by the water channel closing means on the downstream side, and the flow velocity and water level of the fluid in the water channel are measured, and the cross-sectional area of the measurement point is obtained from this water level. In a flow meter that calculates the flow rate of fluid by multiplying
A flow rate correction method for a flow meter, wherein the flow rate is corrected by using a change in a water level while proper measurement of the flow velocity is impossible. In a flow meter that is provided in a water channel where the fluid stays when closed by a water channel closing means on the downstream side, and at least measures the flow rate of the fluid in the water channel to determine the flow rate of the fluid,
After measuring and storing the volume of the fluid in the water channel at the time the fluid flow velocity measurement becomes impossible,
Measure the volume of the fluid in the water channel when the flow velocity measurement can be resumed, and subtract the volume of the stored fluid from this volume to obtain the volume of the staying fluid that stays in the water channel while the flow velocity measurement is impossible. ,
A flow rate correction method for a flow meter, wherein the flow rate is corrected according to the volume of the staying fluid.   According to the water level measured at the measurement point, the volume of the fluid in the channel downstream from the measurement point is obtained, and the volume at the time when the flow velocity measurement becomes impossible is stored in the first storage unit, and the flow velocity measurement can be resumed. The volume at the time is stored in the second storage unit, the volume stored in the first storage unit is subtracted from the volume stored in the second storage unit, The flow rate correction method for a flow meter according to claim 6, wherein the volume of the staying fluid staying in the downstream water channel is obtained, and a staying correction value proportional to the volume of the staying fluid is added to the flow rate for a predetermined time.   When the measured value of the flow velocity becomes equal to or lower than a predetermined first threshold, the flow velocity is set to zero and a flow velocity measurement zero signal indicating that the flow velocity measurement is disabled is generated, and the measured value of the flow velocity is the first threshold value. The flow velocity measurement restart signal indicating that the flow velocity measurement using the flow velocity measured at the time when the second threshold value is higher than the second threshold value is restarted and that the flow velocity measurement can be resumed is generated. Flow rate correction method for flowmeters.

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