JP2005037325A - Flow measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure an average flow of a pulsating flow in a short time as to a flow measuring instrument for measuring the flow of gas, etc. <P>SOLUTION: This flow measuring instrument is equipped with a flow calculation means 12 for calculating a flow based on a measurement of a flow detector 19, a pulsating flow change calculation means 16 for calculating the degree of change in a flow in pulsating, a measurement time varying means 17 for varying measurement time from the start of measurement to its end, and a pulsation measuring/learning means 18 for learning a relation between the degree of change in the flow and the measurement time. In pulsating, the measurement time is varied based on the measuring/learning means 18. The average flow can be measured in a short time and also power consumption can be reduced by selecting appropriate measurement time in pulsating. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a flow rate measuring device for measuring a flow rate of gas or the like.

  A conventional flow measuring device of this type will be described with reference to FIGS. In FIG. 5, transmitters / receivers 2 and 3 that transmit ultrasonic waves in the middle of the fluid conduit 1 are arranged in the flow direction.

  Reference numeral 4 denotes transmission means for the transmitter / receiver 2. Reference numeral 5 denotes amplification means for the signal received by the transmitter / receiver 3. The amplified signal is compared with the reference signal by the comparison means 6, and a signal equal to or higher than the reference signal is detected. The ultrasonic signal is repeatedly transmitted again by the trigger unit 9 after the repetition unit 8 by the number of times set by the number setting unit 7.

  The time when the number of times set by the repetition number setting means 9 is repeated is obtained by the time counting means 10 such as a timer counter. Next, transmission / reception between the transmitter / receiver 2 and the transmitter / receiver 3 is switched by the switching means 11, and an ultrasonic signal is transmitted from the transmitter / receiver 3 to the transmitter / receiver 2, that is, from downstream to upstream, and this transmission is repeated as described above. , Time the time.

  Then, the flow rate of the fluid is obtained from the time difference, and then the flow rate value is obtained by the flow rate calculation means 12 in consideration of the size of the pipe line and the flow state.

When the flow rate value periodically fluctuates, a fluctuation period is detected by the period detection means 13, a measurement time that is an integral multiple of the period is set by the measurement time changing means 14, and the repetition corresponding to the set time is repeated. The number of times is set in the number setting means 7. The period detection means 13 continuously measures the flow rate in a very short time, and calculates from the time interval at the point where the flow rate increases and crosses the average value as shown by the waveform A in FIG. 15, the period T1 of the waveform A is obtained by detecting and calculating the pressure fluctuation in the fluid pipe line 1, and the average flow velocity is calculated by performing measurement for an integral multiple of the period (see, for example, Patent Document 1). ).
JP 10-197303 A

  However, the above conventional measuring device not only requires a special device to detect the cycle, but also sometimes cannot accurately measure the cycle.

  For example, a pulsation waveform such as waveform B in FIG. 6 has a real problem. The period is not accurately measured and it is determined that the period is shorter than the actual period T2, and the average value of the period T2 is calculated as the flow rate. Therefore, the average flow rate is detected erroneously, and the accurate flow rate is calculated. Have problems.

  This invention solves the said subject, and aims at measuring the flow volume at the time of a pulsation correctly.

  In order to solve the above problems, the present invention provides a flow rate calculating means for calculating a flow rate based on a value of a flow rate detector, a pulsating flow change calculating means for calculating a flow rate change degree during pulsation, and a start of measurement. The measurement time changing means for changing the measurement time until the end, and the pulsation measurement learning means for learning the relationship between the change degree of the flow rate and the measurement time, and the measurement time was changed based on the pulsation measurement learning means at the time of pulsation Therefore, the flow rate is measured by selecting an appropriate measurement time by learning during pulsation.

  The flow rate measuring device of the present invention includes a flow rate calculating means for calculating a flow rate based on a value of a flow rate detector, a pulsating flow change calculating means for calculating a change degree of the flow rate during pulsation, and measurement from the start to the end of measurement. Since the measurement time changing means for changing the time and the pulsation measurement learning means for learning the relationship between the change degree of the flow rate and the measurement time are provided and the measurement time is changed based on the pulsation measurement learning means at the time of pulsation, Not only can the average flow rate be measured accurately in a short time by selecting an appropriate measurement time, but also the power consumption can be reduced.

  The embodiment of the present invention includes a flow rate detector for detecting a flow rate in a fluid, a flow rate calculation means for calculating a flow rate based on a value of the flow rate detector, and a pulsating flow change for calculating a change rate of the flow rate during pulsation. Based on the pulsation measurement learning means at the time of pulsation, comprising a calculation means, a measurement time change means for changing the measurement time from the start to the end of measurement, and a pulsation measurement learning means for learning the relationship between the degree of change in flow rate and the measurement time Therefore, an accurate average flow rate can be obtained in a short time because the flow rate is measured by selecting an appropriate measurement time during pulsation.

  In addition, an ultrasonic transmitter / receiver that transmits or receives ultrasonic waves in the fluid, a repeating unit that performs transmission / reception between the ultrasonic transmitters / receivers a plurality of times, a time measuring unit that measures the propagation time of sound waves between the ultrasonic transmitters / receivers, A flow rate calculating means for calculating a flow rate based on the value of the time measuring means, a pulsating flow change calculating means for calculating a change degree of the flow rate during pulsation, and a measuring time changing means for changing a measuring time from the start to the end of the measurement, Pulsation measurement learning means that learns the relationship between the degree of change in flow rate and measurement time, and changes the measurement time based on the pulsation measurement learning means at the time of pulsation, so that the measurement time suitable for the pulsation cycle is selected. Can accurately measure the average flow rate.

  The pulsation measurement learning means stores the relationship between the length of the measurement time during pulsation and the flow rate change degree for each measurement, and prioritizes the measurement time with the smallest flow rate change degree.

  The measurement time is changed when the flow rate change degree is large even if the pulsation measurement learning means is applied.

  The data of the pulsation measurement learning means is updated when the pulsation continues.

  When the flow rate change degree is less than or equal to a predetermined value for a predetermined number of times or for a predetermined time, measurement is performed with a preset measurement time set in advance, and the measurement time is reset according to the flow rate change degree at that time.

  The measuring time changing means was changed by changing the number of repetitions.

  Correction was added according to the supersonic speed of the measurement fluid.

  A transmission / reception delay means for generating a delay time during repeated transmission / reception of ultrasonic waves is provided, and the measurement time changing means changes with this delay time.

  The time measuring means was measured including the delay time.

  The measurement time changing means changes the measurement time of the dispersion measuring means for measuring by repeating the measurement by the repetition means as a set at predetermined time intervals.

  The measurement time changing means changes the time interval between the measurement sets and sets the measurement time.

  The measurement time changing means sets the measurement time by changing the number of measurement sets.

  The pulsation measurement learning means discriminates learning data according to the date or time.

  Embodiments of the present invention will be described below with reference to the drawings.

(Example 1)
In FIG. 1, the same reference numerals are assigned to the same components as in the conventional example.

  In FIG. 1, ultrasonic transceivers 2 and 3 are provided in a part of a flow path 1 so as to be opposed to the flow direction, a transmission signal is transmitted by a trigger means 4, and the upstream transceiver 1 is directed in the same direction as the flow. Generate ultrasound.

  This ultrasonic wave propagates in the flow at the speed of sound, is detected by the transmitter / receiver 2 and converted into an electric signal, the amplification means 5 amplifies the signal, the comparison means 6 compares it with the reference signal, and the ultrasonic signal is received. It is detected that

  This change of the comparison signal is sent to the repetition means 7 and transmitted again by the trigger means 4 via the delay means 8. The number of repetitions ends with the number set by the number setting means 9.

  The timer 10 resets the timer when the first trigger signal is transmitted, and measures the time until the repetition is completed. The total time of the ultrasonic propagation time and the delay time by the delay means 8 is measured.

  The flow rate detector 19 is formed by the above components.

  When the transmission of the ultrasonic wave from the upstream to the downstream is finished, the transmission / reception direction is switched by the switching means 11, and the transmission is performed from the transmitter / receiver 3 to the transmitter / receiver 2, that is, from the downstream to the upstream. Similarly, transmission is repeated and the time is counted. From the time difference from the upstream to the downstream and the time difference from the downstream to the upstream, the flow rate calculation unit 12 calculates the flow rate by an arithmetic expression such as a reciprocal difference in propagation time.

  The magnitude of the change in the flow rate is calculated by the pulsation change calculating means 16. The pulsation change calculating means 16 calculates the magnitude of fluctuation such as the maximum and minimum difference or standard deviation of the flow rate value.

  Reference numeral 17 denotes measurement time changing means for setting the time from the start to the end of one measurement. In FIG. 1, the number setting means 9 and the delay adjusting means 13 are adjusted.

  Reference numeral 18 denotes pulsation measurement learning means, which sequentially stores the relationship between the flow rate measurement time and the pulsating flow change calculation means 16 for each measurement.

  Next, the operation will be described. The time difference measured by the flow rate detector 19 is calculated by the flow rate calculation means 12. This flow rate measurement is performed at intervals of several seconds, but in a battery-driven measuring instrument such as a gas meter, the actual measurement time must be shortened to about one-tenth of a few seconds in order to reduce power consumption.

  Since a part of the time is measured and integrated, an error occurs if there is pulsation. The largest pulsation is when the periodic pulsation due to the operation of the gas engine continues.

  When the pulsation like the waveform B in FIG. 2 is repeated, if each point of the broken line is measured by ultrasonic waves, the average value can be accurately calculated by measuring the time T1, and T2 If this time is measured, the flow rate becomes larger than the actual flow rate.

  However, since the pulsation waveform and the measurement timing are not fixed, when the measurement is performed at the same measurement time T2 or T3, the measured flow rate is large at T2 and small at T3. The variation degree of the flow rate can be calculated by the pulsating flow change calculating means 16.

  If the measurement time is changed by the measurement time changing means 17 and the flow rate change degree at that time is obtained, the variation is small when measured at the measurement time T1, and the variation is large when measured at the measurement time T2.

  If the measurement time and the degree of variation in the flow rate are stored, the measurement time (in this case, T1) at which the average flow rate is most likely to be measured when pulsation occurs may be selected.

  Since the frequency of the pulsation source is limited to a certain range, if it is learned once, it can be measured with an almost optimal measurement time, but when the frequency changes due to a new pulsation source, it automatically starts a new learning It will be.

  FIG. 3 shows an example when the frequency is changed.

  When a low-frequency pulsation such as waveform C occurs instead of waveform B, the variation in the flow rate calculation value becomes large at measurement time T1, and the measurement time is learned by changing the measurement time.

  As a result, the measurement time T4 can be obtained. When the waveform B and the waveform C appear alternately, the two measurement times T1 and T4 are applied with priority, and the measurement time is determined based on the degree of variation.

  When learning the measurement time, it is possible to avoid the influence of sudden pulsation. For example, in an instantaneous water heater, the gas amount may be changed in order to adjust the hot water temperature. In order not to store such fluctuations in the gas amount as pulsation learning data, fluctuations in the flow rate value continued for a predetermined time. Only when it is determined to be pulsation, learning is applied.

  When the pulsation of the waveform C in FIG. 3 is measured at the measurement time T4, when the pulsation is stopped, the variation in the flow rate calculation value becomes extremely small, so it can be determined that the pulsation has disappeared. Even if it is shortened to reduce power consumption, accurate flow rate can be measured.

  However, in some cases, the determination cannot be made and the measurement may be continued for a long measurement time T4. In such a case, if a period in which the variation in the flow rate calculation value is somewhat small during measurement at the measurement time T4 continues, it can be determined that there is no pulsation if there is no difference compared to the previous flow rate value by reducing the measurement time. .

  The measurement time can be changed by changing the number of measurement repetitions by the number setting means 9 of the repetition means 7 in FIG. The propagation time of the sound wave and the delay time of the delay means 8 are known, and the repetition time per time can be calculated.

  Since the propagation time of the sound wave changes depending on the type and temperature of the fluid, it can be calculated by correcting or by actually measuring the time per one time.

  The measurement time can be changed without increasing the number of measurements by adjusting the delay time with the delay adjusting means 13 of FIG.

  If the delay time is increased to increase the measurement time, the flow rate value is affected by the deterioration of the accuracy of the delay time (the power consumption increases when the high resolution delay time occurs), and the power consumption increases when the number of repetitions is increased.

  In such a case, as shown in FIG. 4, the transmission from the upstream to the downstream is a white circle, the transmission black circle from the downstream to the upstream, and the measurement of a small number of repetitions (2 times in the figure) is one measurement set as a predetermined time interval. If the measurement is performed in a distributed manner, the total number of repetitions does not increase and a long measurement time can be obtained.

  In this case, the timing means 10 includes two timing means for transmitting from the upstream to the downstream and a timing means for transmitting from the downstream to the upstream, and is performed without using a microcomputer in synchronization with the switching means 11. be able to. When measuring in a distributed manner in this way, the measurement time can be changed by changing the number of measurement sets.

  The source of pulsation may vary depending on the time zone such as night and noon, or may vary depending on the season.

  In this case, the pulsation measurement learning means 18 can perform learning by time zone or learning by season, and can determine the measurement time based on the learning data by time zone or season. Thus, the optimum measurement time can be determined without using the pressure sensor, and the number of parts can be reduced and the cost can be reduced.

  Although the flow rate measurement method has been described in the above embodiment, it is possible to determine pulsation based on a flow velocity value that is an intermediate result of the calculation, or to calculate a flow velocity as a final output value. These techniques can be applied to measuring instruments such as gas meters.

  Further, the flow rate detecting means can be applied to a thermal type or a vortex type in addition to the acoustic type.

  As described above, according to the flow rate measuring device according to the present invention, an appropriate measurement time can be selected at the time of pulsation, and the average flow rate can be accurately measured in a short time. It can be used in a wide range up to liquid fluid.

Control block diagram of the flow rate measuring apparatus of the first embodiment of the present invention Flow waveform diagram during pulsation showing the flow measurement status of the device Flow waveform diagram during pulsation showing the flow measurement status of the device Flow waveform diagram during pulsation showing the flow measurement status of the device Control block diagram of a conventional flow measurement device Flow waveform diagram during pulsation showing the flow measurement status of the device

Explanation of symbols

2, 3 Ultrasonic transmitter / receiver 8 Delay means 9 Count setting means 10 Timing means 12 Flow rate calculation means 13 Delay adjustment means 16 Pulsating flow change calculation means 17 Measurement time changing means 18 Pulsation measurement learning means 19 Flow rate detector

Claims (14)

A flow rate detector for detecting a flow rate in the fluid, a flow rate calculating means for calculating a flow rate based on the value of the flow rate detector, a pulsating flow change calculating means for calculating a change degree of the flow rate during pulsation, and start of measurement Measurement time changing means for changing the measurement time from the end to the end, and a pulsation measurement learning means for learning the relationship between the change degree of the flow rate and the measurement time, and changing the measurement time based on the pulsation measurement learning means during pulsation A flow rate measuring device designed to be used. An ultrasonic transmitter / receiver that transmits or receives ultrasonic waves in the fluid, a repeating unit that performs transmission / reception between the ultrasonic transmitters / receivers a plurality of times, a time measuring unit that measures a propagation time of sound waves between the ultrasonic transmitters / receivers, Flow rate calculating means for calculating the flow rate based on the value of the time measuring means, pulsating flow change calculating means for calculating the degree of change in flow rate during pulsation, and measurement time changing means for changing the measurement time from the start to the end of measurement And a pulsation measurement learning unit that learns the relationship between the change degree of the flow rate and the measurement time, and the measurement time is changed based on the pulsation measurement learning unit during pulsation. The flow rate measurement according to claim 1 or 2, wherein the pulsation measurement learning means stores the relationship between the length of the measurement time and the flow rate change degree at the time of the pulsation for each measurement, and preferentially applies the measurement time with the smallest flow rate change degree. apparatus. The flow rate measuring device according to claim 1 or 2, wherein the measurement time is changed when the flow rate change degree is large even when the pulsation measurement learning means is applied. The flow rate measuring device according to claim 3, wherein the data of the pulsation measurement learning means is updated when the pulsation continues. The measurement time is reset according to a predetermined flow rate change at that time, when the state where the change rate of the flow rate is a predetermined value or less continues for a predetermined number of times or for a predetermined time, and the measurement time is reset. Flow measurement device. The flow rate measuring device according to claim 2, wherein the measurement time changing means is performed by changing the number of repetitions. The flow rate measuring apparatus according to claim 2, wherein correction is made according to the sound velocity of the measurement fluid. The flow rate measuring device according to claim 2, further comprising a transmission / reception delay unit that generates a delay time during repeated transmission / reception of ultrasonic waves, and wherein the measurement time changing unit changes the delay time. The flow rate measuring device according to claim 9, wherein the time measuring means performs measurement including a delay time. 3. The flow rate measuring device according to claim 2, wherein the measurement time changing means changes the measurement time of the dispersion measuring means that performs measurement by dispersing at predetermined time intervals with the measurement by the repetition means as one set. The flow measurement device according to claim 11, wherein the measurement time changing means sets the measurement time by changing a time interval between measurement sets. The flow rate measuring device according to claim 11, wherein the measurement time changing means sets the measurement time by changing the number of measurement sets. The flow rate measuring device according to claim 1 or 2, wherein the pulsation measurement learning means distinguishes learning data according to a date or time.

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