Flow rate measuring device

Abstract

This flow rate measuring device includes: a zero-cross identifying means for identifying a zero-crossing point at which the voltage of an amplified signal changes from positive to negative for the first time after exceeding a reference voltage, the amplified signal being obtained by amplifying a received signal received by a first oscillator or a second oscillator; a timing means for measuring an elapsed time from when a drive signal was transmitted until the zero-crossing point; a peak detecting means for detecting a plurality of peak voltages of the amplified signal; a reference determining means for determining a voltage between two adjacent peak voltages among the plurality of peak voltages as a reference voltage for flow rate measurement; and a necessity determining means for determining, on the basis of the voltage of the amplified signal, whether it is necessary for the reference determining means to re-determine the reference voltage for flow rate measurement.

Description

Flow Metering Device

[0001] The present disclosure relates to a flow rate measurement device that uses ultrasound to measure the flow rate of a fluid such as gas or water.

[0002] A conventional flow measurement device is known that resets the reference voltage so that it falls within a predetermined peak voltage range of the received signal when the difference between the time difference measured by the time difference measuring means (the time from the start of ultrasonic wave transmission to the zero crossing point) and the value stored in the time difference storage means exceeds a predetermined value (Patent Document 1). This is said to prevent a deterioration in the accuracy of the calculation of the flow velocity and flow rate by the calculation means.

[0003] JP 2014-006170 A

[0004] However, in recent years, the types of gases to be measured have become more diverse, and the peak voltage may fluctuate depending on the gas type. As a result, it may not be possible to maintain the reference voltage within the specified peak voltage range of the received signal. While it is possible to periodically reset the reference voltage, this method may result in resetting the reference voltage even when it is being maintained within the specified peak voltage range, resulting in an increase in current consumption due to unnecessary processing.

[0005] Therefore, an object of the present disclosure is to provide a flow rate measurement device that can suppress an increase in current consumption while avoiding a decrease in the accuracy of calculating the flow velocity and flow rate of a fluid.

[0006] The flow rate measurement device of the present disclosure includes a first oscillator and a second oscillator that are provided in a fluid pipeline and transmit and receive ultrasonic signals, a transmitting means that transmits a drive signal to the first oscillator or the second oscillator, a switching means that switches between the first oscillator and the second oscillator as a target that receives the drive signal, an amplifying means that amplifies a received signal received by the first oscillator or the second oscillator and outputs an amplified signal, and a zero-crossing identifying means that compares the voltage of the amplified signal with a reference voltage and identifies a zero-crossing point where the voltage of the amplified signal changes from positive to negative for the first time after the voltage of the amplified signal exceeds the reference voltage. a timing means for timing the elapsed time from the transmission of the drive signal to the zero crossing point; a peak detection means for detecting a plurality of peak voltages of the amplified signal; a reference determination means for determining a voltage between two adjacent peak voltages among the plurality of peak voltages as a reference voltage for flow measurement; a calculation means for calculating the flow velocity and flow rate of the fluid flowing through the fluid pipeline based on the elapsed time when the reference voltage for flow measurement is set as the reference voltage; and a necessity determination means for determining whether or not the reference voltage for flow measurement needs to be redetermined by the reference determination means based on the voltage of the amplified signal.

[0007] According to the present disclosure, the peak voltage detection process and the process of redetermining the flow rate measurement reference voltage based on the peak voltage are performed only when the necessity determination means determines that redetermining the flow rate measurement reference voltage is necessary based on a change in the voltage of the amplified signal of the received signal. This prevents a decrease in calculation accuracy (calculation accuracy of the fluid flow velocity and flow rate) caused by the flow rate measurement reference voltage, which is set to be between predetermined peak voltages, deviating from the predetermined peak voltage range due to peak voltage fluctuations depending on the gas type. In addition, the number of times the ultrasonic signal is transmitted can be reduced, thereby suppressing an increase in current consumption.

[0008] In the above disclosure, the necessity determination means may determine that the redetermination is necessary when, between two adjacent peak voltages, a voltage lower than the reference voltage for flow measurement is defined as a first voltage and a voltage higher than the reference voltage for flow measurement is defined as a second voltage, and when the peak detection means changes the reference voltage between the first voltage and the second voltage in predetermined increments, there is a voltage of the amplified signal at which the elapsed time obtained by the timing means in the predetermined increments changes at a rate equal to or greater than a predetermined rate of change.

[0009] According to the above configuration, the flow rate measurement reference voltage can be redetermined only when a peak voltage is detected between the first voltage and the second voltage. A case in which a peak voltage is detected between the first voltage and the second voltage means that the voltage difference between the flow rate measurement reference voltage and the peak voltage is relatively small, and there is a high possibility that the flow rate measurement reference voltage will deviate from the peak voltage range. As a result, if the flow rate measurement reference voltage is unlikely to deviate from the peak voltage range, there is no need to redetermine the flow rate measurement reference voltage unless a peak voltage is detected between the first voltage and the second voltage. This reduces the number of times an ultrasonic signal is transmitted, and avoids a decrease in calculation accuracy (calculation accuracy of the fluid flow velocity and flow rate) caused by a peak voltage being detected between the first voltage and the second voltage.

[0010] In the above disclosure, the necessity determination means may determine that the redetermination is necessary if, when the peak detection means changes the reference voltage between the first voltage and the second voltage in predetermined increments, the voltage between two adjacent peak voltages is defined as a first voltage and a voltage higher than the higher of the two adjacent peak voltages is defined as a second voltage, and the elapsed time obtained by the timing means in the predetermined increments does not have a voltage of the amplified signal that changes at a rate equal to or greater than a predetermined rate of change.

[0011] According to the above configuration, the flow rate measurement reference voltage can be redetermined only when a peak voltage that was originally located between the first voltage and the second voltage is no longer detected between the first voltage and the second voltage, i.e., when the waveform of the amplified signal changes. As a result, there is no need to redetermine the flow rate measurement reference voltage when the waveform of the amplified signal does not change. This makes it possible to reduce the number of times the ultrasonic signal is transmitted and to avoid a decrease in calculation accuracy (calculation accuracy of the fluid flow velocity and flow rate) caused by changes in the waveform of the amplified signal.

[0012] In the above disclosure, the necessity determining means may determine whether or not it is necessary to further determine the reference voltage for flow rate measurement again immediately after the reference voltage for flow rate measurement is redetermined by the reference determining means.

[0013] The gas type may fluctuate instantaneously, changing the waveform of the amplified signal. According to the above configuration, if the fluctuation occurs during peak voltage detection, it is possible to avoid determining the reference voltage for flow rate measurement based on the amplified signal while it is fluctuating. Therefore, the reference voltage for flow rate measurement can be re-determined based on the received signal after the gas type has changed.

[0014] In the above disclosure, the necessity determining means may determine whether or not it is necessary to redetermine the reference voltage for flow rate measurement immediately after power-on.

[0015] According to the above configuration, when the flow measurement device is in a power-off state, if the reference voltage for flow measurement deviates from a predetermined peak voltage range or is a value near the peak voltage rather than at the midpoint between the peak voltages, it can be determined that the reference voltage for flow measurement needs to be redetermined. As a result, the reference voltage for flow measurement can be redetermined based on the determination result.

[0016] In the above disclosure, when the necessity determination means determines that the re-determination is necessary, the standard determination means may re-determine the reference voltage for flow measurement multiple times at predetermined time intervals, and may repeat the re-determination of the reference voltage for flow measurement until the variation of the re-determined reference voltages for flow measurement falls within a threshold value.

[0017] According to the above configuration, it is possible to determine that the reference voltage for flow measurement needs to be redetermined when the waveform of the received signal is fluctuating instantaneously, and by repeating the redetermining of the reference voltage for flow measurement until the variation in the reference voltage for flow measurement falls within the threshold, it is possible to avoid determining the reference voltage for flow measurement while the waveform of the received signal is fluctuating.

[0018] In the above disclosure, the peak detection means may vary the first voltage and the second voltage based on the detected peak voltage.

[0019] Depending on the type of gas, the interval between the peak voltages may become narrow. In some cases, the voltage difference between the first voltage and the second voltage may be greater than the interval between the peak voltages. According to the above configuration, it is possible to avoid the step of the necessity determination means determining that redetermining the reference voltage for flow rate measurement is necessary and the step of the reference voltage determination means redetermining the reference voltage for flow rate measurement based on the determination result.

[0020] According to the present disclosure, it is possible to provide a flow measurement device that can suppress an increase in current consumption while avoiding a decrease in the accuracy of calculating the flow velocity and flow rate of a fluid.

[0021] FIG. 1 is a block diagram showing the configuration of a flow measurement device according to an embodiment. FIG. 2 is a diagram for explaining the elapsed time from the transmission of a burst wave to a zero-crossing point. FIG. 3(a) is an explanatory diagram showing an example of a case where redetermining the reference voltage for flow measurement is not necessary, and FIG. 3(b) is an explanatory diagram showing an example of a case where redetermining the reference voltage for flow measurement is necessary. FIG. 3(a) is an explanatory diagram showing another example of a case where redetermining the reference voltage for flow measurement is not necessary, and FIG. 3(b) is an explanatory diagram showing another example of a case where redetermining the reference voltage for flow measurement is necessary. FIG. 4 is a flowchart showing the flow of processing in the flow measurement device. FIG. 5 is an explanatory diagram showing another example of a method for detecting a peak voltage.

[0022] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of already well-known matters or repeated description of substantially identical configurations may be omitted. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0023] 1, the flow rate measuring device 100 includes a fluid pipeline 1, a first ultrasonic vibrator 2, a second ultrasonic vibrator 3, a transmitting means 4, a switching means 5, an amplifying means 6, a zero-cross identifying means 7, a timing means 8, a necessity determining means 9, a peak detecting means 10, a reference determining means 11, and a calculating means 12. In this embodiment, the first ultrasonic vibrator 2 corresponds to the first vibrator, and the second ultrasonic vibrator 3 corresponds to the second vibrator.

[0024] The flow measurement device 100 has a CPU and a storage unit (ROM, RAM, EEPROM, HDD, etc.). The CPU 20 executes a predetermined program stored in the storage unit to functionally realize the above-mentioned transmitting means 4, switching means 5, amplifying means 6, zero-crossing identifying means 7, timing means 8, necessity determining means 9, peak detecting means 10, reference determining means 11, and calculating means 12. The CPU may be implemented as a single processor, or may be implemented as multiple processors that cooperate with each other.

[0025] The fluid pipeline 1 extends in a predetermined direction. A fluid flows through the fluid pipeline 1. Examples of the fluid flowing through the fluid pipeline 1 include gas and water.

[0026] The first ultrasonic transducer 2 is installed in the fluid pipeline 1 so that its ultrasonic transmitting and receiving surface is exposed inside the fluid pipeline 1. The second ultrasonic transducer 3 is installed in the fluid pipeline 1 so that its ultrasonic transmitting and receiving surface is exposed inside the fluid pipeline 1 and so that it faces the ultrasonic transmitting and receiving surface of the first ultrasonic transducer 2 in the direction of the ultrasonic propagation path. The first ultrasonic transducer 2 and the second ultrasonic transducer 3 transmit and receive ultrasonic waves. That is, ultrasonic waves transmitted from the first ultrasonic transducer 2 are received by the second ultrasonic transducer 3. Also, ultrasonic waves transmitted from the second ultrasonic transducer 3 are received by the first ultrasonic transducer 2.

[0027] The transmitting means 4 drives the first ultrasonic vibrator 2 and the second ultrasonic vibrator 3 via the switching means 5. The transmitting means 4 applies, for example, a burst wave as a drive signal to the first ultrasonic vibrator 2 and the second ultrasonic vibrator 3 via the switching means 5.

[0028] The switching means 5 switches the target for receiving the drive signal from the transmitting means 4 between the first ultrasonic transducer 2 and the second ultrasonic transducer 3. When the target for receiving the drive signal from the transmitting means 4 is switched to the first ultrasonic transducer 2 by the switching means 5, the first ultrasonic transducer 2 transmits ultrasonic waves, and the second ultrasonic transducer 3 receives the ultrasonic waves. On the other hand, when the target for receiving the drive signal from the transmitting means 4 is switched to the second ultrasonic transducer 3 by the switching means 5, the second ultrasonic transducer 3 transmits ultrasonic waves, and the first ultrasonic transducer 2 receives the ultrasonic waves.

[0029] The amplifier 6 amplifies the signal received by the receiving ultrasonic transducer of the first ultrasonic transducer 2 or the second ultrasonic transducer 3 and passed through the switch 5 to a predetermined amplitude and outputs the amplified signal.

[0030] The zero-crossing identifying means 7 compares the voltage of the amplified signal with a reference voltage. As shown in Fig. 2, the zero-crossing identifying means 7 identifies a zero-crossing point Pz at which the voltage of the amplified signal changes from positive to negative for the first time after the voltage of the amplified signal exceeds the reference voltage. This zero-crossing point Pz indicates the time when the ultrasonic wave transmitted by the ultrasonic transducer on the transmitting side is received by the ultrasonic transducer on the receiving side.

[0031] The timing means 8 measures the elapsed time Tp from the time when the drive signal is transmitted by the transmitting means 4 to the zero cross point Pz. That is, the elapsed time Tp is the time from the time when the ultrasonic wave is transmitted by the ultrasonic transducer on the transmitting side to the time when the ultrasonic wave is received by the ultrasonic transducer on the receiving side, and corresponds to the propagation time of the ultrasonic wave.

[0032] The necessity determining means 9 determines, based on the voltage of the periodic amplified signal, whether or not it is necessary for the reference determining means 11 to redetermine the reference voltage Vref for flow rate measurement, which will be described later. Details of the processing by the necessity determining means 9 will be described later.

[0033] The peak detection means 10 varies the reference voltage in predetermined increments from a predetermined start voltage to a predetermined end voltage, and detects a plurality of reference voltages as peak voltages of the amplified signal when the elapsed time Tp obtained by transmitting the drive signal at each predetermined increment changes suddenly (for example, when it changes at a rate greater than a predetermined rate). Specifically, as shown in FIG. 2 , the peak detection means 10 detects peak voltages p1, p2, p3, p4, and p5 of the amplified signal. In this embodiment, the start voltage corresponds to the first voltage, and the end voltage corresponds to the second voltage.

[0034] In this embodiment, for example, the predetermined start voltage may be a voltage lower than the reference voltage Vref for flow measurement, and the predetermined end voltage may be a voltage higher than the reference voltage Vref for flow measurement. Alternatively, the predetermined start voltage may be a voltage lower than any one of the multiple peak voltages p1, p2, p3, p4, and p5 detected by the peak detection means 10, and the predetermined end voltage may be a voltage higher than any one of the peak voltages. Furthermore, the predetermined increment may be one control unit (e.g., 2 mV) of the variable range of the reference voltage.

[0035] Furthermore, the peak detection means 10 may change the start voltage and the end voltage based on the detected peak voltage. In this case, it is possible to avoid as much as possible the step in which the necessity determination means 9 determines that redetermining the flow rate measurement reference voltage Vref is necessary, and the step in which the reference determination means 11 redetermines the flow rate measurement reference voltage Vref based on the determination result.

[0036] The reference determination means 11 determines the flow rate measurement reference voltage Vref based on the peak voltages p1, p2, p3, p4, and p5 detected by the peak detection means 10. Specifically, the reference determination means 11 may determine the voltage between two adjacent peak voltages among the plurality of peak voltages p1, p2, p3, p4, and p5 as the flow rate measurement reference voltage Vref. The flow rate measurement reference voltage Vref is a voltage for determining the zero-cross point Pz (in other words, a voltage for measuring the elapsed time Tp), a voltage used when the calculation means 12 calculates the flow velocity and flow rate of the fluid, and is a voltage located midway between a predetermined range of peak voltages, for example, peak voltages p2 and p3. This is because the difference between peak voltages p2 and p3 is the largest, and setting the flow rate measurement reference voltage Vref between these peak voltages can avoid a decrease in calculation accuracy (calculation accuracy of the fluid flow velocity and flow rate) caused by the flow rate measurement reference voltage Vref deviating from the predetermined range of peak voltages due to peak voltage fluctuations depending on the gas type. In this embodiment, the reference voltage for flow rate measurement is set between peak voltage p2 and peak voltage p3, but this is not limited to this, and the range between the peak voltages to which the reference voltage for flow rate measurement is set may be changed as appropriate depending on the characteristics of the first ultrasonic vibrator 2 and the second ultrasonic vibrator 3.

[0037] Furthermore, when the necessity determination means 9 determines that redetermining the flow rate measurement reference voltage Vref is necessary, the reference determination means 11 may redetermine the flow rate measurement reference voltage Vref multiple times at predetermined time intervals, and may repeat the redetermining of the flow rate measurement reference voltage Vref until the variation in the multiple redetermined flow rate measurement reference voltages Vref falls within a threshold. In this case, by repeatedly redetermining the flow rate measurement reference voltage Vref until the variation in the flow rate measurement reference voltage Vref falls within the threshold, it is possible to avoid determining the flow rate measurement reference voltage Vref while the waveform of the amplified signal is fluctuating. After repeatedly redetermining the flow rate measurement reference voltage Vref, the reference determination means 11 may, for example, determine the final flow rate measurement reference voltage Vref as the flow rate measurement reference voltage Vref, or may determine the average value of the multiple flow rate measurement reference voltages Vref as the flow rate measurement reference voltage Vref.

[0038] The calculation means 12 calculates the flow velocity and flow rate of the fluid flowing through the fluid pipeline 1 based on the elapsed time Tp when the flow rate measurement reference voltage Vref is used as the reference voltage. In this case, an ultrasonic signal transmitted by the first ultrasonic transducer 2 based on a drive signal from the transmission means 4 propagates through the fluid flow and is received by the second ultrasonic transducer 3. The received signal is then amplified by the amplification means 6. The zero-crossing identification means 7 compares the voltage of the amplified signal with the reference voltage and identifies the zero-crossing point Pz. The timing means 8 measures the elapsed time Tp from the transmission of the drive signal to the zero-crossing point Pz. In this manner, the process from the transmission of the burst wave by the transmission means 4 to the calculation of the elapsed time Tp by the timing means 8 (hereinafter referred to as the elapsed time calculation process) is executed a predetermined number n of times. That is, the elapsed time calculation process is executed one or more times. Furthermore, the time required for the above-described elapsed time calculation process to be completed n times (hereinafter referred to as the total processing time) is measured by a timing means (not shown).

[0039] The ultrasonic wave transmitting and receiving sides of the first ultrasonic transducer 2 and the second ultrasonic transducer 3 are switched by the switching means 5, and the above-mentioned elapsed time calculation process is executed n times for each of the first mode in which the first ultrasonic transducer 2 is the transmitting side and the second mode in which the second ultrasonic transducer 3 is the transmitting side. The calculation means 12 calculates the flow velocity based on the elapsed time Tp (i.e., propagation time) in each of the above modes, and calculates the flow rate Q from the following equation 1. In equation 1, L is the effective distance in the flow direction between the ultrasonic transducers, t1 is the time required to execute the above process n times in the first mode (the total processing time measured by the time measurement means, i.e., the total time of the elapsed times Tp for n times), and t2 is the time required to execute the above process n times in the second mode (the same time as above). In Equation 1, v is the fluid flow velocity, S is the cross-sectional area of ​​the fluid conduit 1, and Φ (FIG. 1) is the angle between the ultrasonic propagation path between the ultrasonic transducers and the fluid flow direction. Note that the above t1 and t2 are times assuming that the flow rate measurement reference voltage is between the same peaks (between peak voltage p2 and peak voltage p3 in this embodiment) in both the first and second modes. For example, if the flow rate measurement reference voltage is set between peak voltage p2 and peak voltage p3 in the first mode and between peak voltage p3 and peak voltage p4 in the second mode, the desired measurement time t2 will not be obtained, resulting in a decrease in the flow velocity of the fluid and the accuracy of calculation of the flow rate calculated based on the flow velocity.

[0040] (Math. 1) Q=S・v=S・L / 2・cosΦ((n / t1)-(n / t2))

[0041] Next, a detailed description will be given of the process of determining whether or not the flow rate measurement reference voltage Vref needs to be redetermined by the necessity determining means 9.

[0042] First, as shown in FIG. 3A, the peak detection means 10 sets a voltage lower than the flow rate measurement reference voltage Vref (i.e., the current flow rate measurement reference voltage Vref) as the start voltage and a voltage higher than the flow rate measurement reference voltage Vref as the end voltage, and increases the reference voltage between the start voltage and the end voltage in predetermined increments for each elapsed time calculation process. Accordingly, the zero-crossing identification means 7 identifies the zero-crossing point Pz in predetermined increments for each elapsed time calculation process. Furthermore, the timing means 8 measures the elapsed time Tp in predetermined increments for each elapsed time calculation process. At this time, the necessity determination means 9 determines that the flow rate measurement reference voltage Vref needs to be redetermined if the elapsed time Tp obtained by the timing means 8 changes rapidly (changes at a rate greater than a predetermined rate) and there is a voltage of the amplified signal.

[0043] 3A, the zero-crossing point Pz obtained by the zero-crossing identification means 7 when the reference voltage is the start voltage is the zero-crossing point Pz3 of the third wave (the wave corresponding to the peak voltage p3) of the amplified signal. On the other hand, the zero-crossing point Pz obtained by the zero-crossing identification means 7 when the reference voltage is the end voltage is also the zero-crossing point Pz3. Therefore, in the case of FIG. 3A, the elapsed time Tp obtained when the reference voltage is the start voltage is the same as the elapsed time Tp obtained when the reference voltage is the end voltage. Therefore, the necessity determination means 9 determines that it is not necessary to redetermine the flow rate measurement reference voltage Vref when there is no voltage of the amplified signal at which the elapsed time Tp changes abruptly.

[0044] 3(b), when the reference voltage is the start voltage, the zero-crossing point Pz obtained by the zero-crossing identification means 7 is zero-crossing point Pz3. On the other hand, when the reference voltage is the end voltage, the zero-crossing point Pz obtained by the zero-crossing identification means 7 is zero-crossing point Pz4 of wave 4 (the wave corresponding to peak voltage p4) of the amplified signal. Therefore, in the case of FIG. 3(b), the elapsed time Tp obtained when the reference voltage is the start voltage is different from the elapsed time Tp obtained when the reference voltage is the end voltage. Therefore, the necessity determination means 9 determines that redetermining the flow rate measurement reference voltage Vref is necessary when there is a voltage of the amplified signal where the elapsed time Tp changes abruptly. As described above, with respect to the aspects shown in FIGS. 3(a) and 3(b), it is possible to determine that redetermining the flow rate measurement reference voltage Vref is necessary only when there is a voltage of the amplified signal where the elapsed time Tp changes abruptly.

[0045] Alternatively, the necessity determining means 9 may determine whether or not it is necessary to redetermine the reference voltage Vref for flow rate measurement based on whether or not there is a change in the peak voltage of the amplified signal as follows.

[0046] As shown in FIG. 4A , when the reference voltage is set to the start voltage, a voltage between two adjacent peak voltages p2 and p3 detected in the past is taken as the start voltage. The zero-crossing point Pz obtained by the zero-crossing identification unit 7 when the reference voltage is set to the start voltage is zero-crossing point Pz3. On the other hand, when the end voltage is set to a voltage higher than the higher of the two adjacent peak voltages p2 and p3, the zero-crossing point Pz obtained by the zero-crossing identification unit 7 when the reference voltage is set to the end voltage is zero-crossing point Pz4 of wave 4 (the wave corresponding to peak voltage p4) of the amplified signal. Therefore, in the case of FIG. 4A , the elapsed time Tp obtained when the reference voltage is the start voltage is different from the elapsed time Tp obtained when the reference voltage is the end voltage. Therefore, the necessity determination unit 9 determines that redetermining the flow rate measurement reference voltage Vref is unnecessary when the peak voltage of the amplified signal has not changed, i.e., when there is a voltage of the amplified signal where the elapsed time Tp changes abruptly. The start voltage may not only be a voltage between two adjacent peak voltages p2 and p3, but also, for example, a voltage between two adjacent peak voltages p3 and p4, etc. However, even in this case, in order to prevent a decrease in the determination accuracy, it is desirable not to set the peak voltage p1, which has a voltage value very small compared to the other peak voltages, and the peak voltage p2 adjacent to the peak voltage p1, as the two adjacent peak voltages.

[0047] 4(b), the zero-crossing point Pz obtained by the zero-crossing identification means 7 when the reference voltage is the start voltage is the zero-crossing point Pz4 of the fourth wave (the wave corresponding to the peak voltage p4) of the amplified signal. On the other hand, the zero-crossing point Pz obtained by the zero-crossing identification means 7 when the reference voltage is the end voltage is also the zero-crossing point Pz4. Therefore, in the case of FIG. 4(b), the elapsed time Tp obtained when the reference voltage is the start voltage is the same as the elapsed time Tp obtained when the reference voltage is the end voltage. Therefore, the necessity determination means 9 determines that redetermining the flow rate measurement reference voltage Vref is necessary when the peak voltage of the amplified signal is changing, i.e., when there is no amplified signal voltage at which the elapsed time Tp changes abruptly. As described above, with respect to the aspects of FIGS. 4(a) and 4(b), it is possible to determine that redetermining the flow rate measurement reference voltage Vref is necessary only when there is no amplified signal voltage at which the elapsed time Tp changes abruptly.

[0048] The necessity determination means 9 may further determine whether or not redetermining the flow rate measurement reference voltage Vref is necessary immediately after the reference voltage Vref has been redetermined by the reference determination means 11. In this case, if a fluctuation in the gas type occurs during peak voltage detection, it is possible to avoid determining the flow rate measurement reference voltage Vref based on the amplified signal during the fluctuation. Note that, as an example of determining whether or not redetermining the flow rate measurement reference voltage Vref is necessary immediately after redetermining, the determination on whether or not redetermining is necessary may be performed at a predetermined cycle, and even if it is determined that redetermining is necessary and the flow rate measurement reference voltage Vref has been redetermined, the determination on whether or not redetermining is performed at the same cycle without changing the cycle may be performed.

[0049] Furthermore, the necessity determination means 9 may determine whether or not redetermining the flow measurement reference voltage Vref is necessary immediately after the power supply to the flow measurement device 100 is turned on. In this case, it can be determined that redetermining the flow measurement reference voltage Vref is necessary when the flow measurement reference voltage Vref deviates from a predetermined peak voltage range while the power supply to the flow measurement device 100 is turned off, or when the flow measurement reference voltage Vref is not at the midpoint between the peak voltages but is near the peak voltage. Note that an example of determining whether or not redetermining the flow measurement reference voltage Vref is necessary immediately after the power supply is turned on may include determining whether or not redetermining is necessary by prioritizing the flow rate measurement by the calculation means 12 after the power supply is switched from off to on.

[0050] Next, the flow of processing in the flow measurement device 100 will be described with reference to a flowchart.

[0051] As shown in FIG. 5, first, one of the first ultrasonic transducer 2 and the second ultrasonic transducer 3 transmits ultrasonic waves toward the other ultrasonic transducer based on a burst wave from the transmitting means 4 (step S1).

[0052] Next, the timing means 8 measures the elapsed time Tp from the transmission of the burst wave to the zero-cross point Pz identified by the zero-cross identifying means 7 when the flow rate measurement reference voltage Vref is used as the reference voltage (step S2).The calculation means 12 calculates the flow velocity and flow rate of the fluid based on the elapsed time Tp (step S3).

[0053] Next, the peak detection means 10 determines whether a predetermined time has elapsed (step S4). If the predetermined time has not elapsed (No in step S4), the process returns to step S1 and repeats the subsequent processes. On the other hand, if the predetermined time has elapsed (Yes in step S4), the peak detection means 10 changes the reference voltage in predetermined increments by setting the start voltage of the reference voltage to a voltage lower by a predetermined value than the current reference voltage for flow rate measurement Vref and setting the end voltage of the reference voltage to a voltage higher by a predetermined value than the current reference voltage for flow rate measurement Vref (step S5).

[0054] The timer 8 measures the elapsed time Tp (the elapsed time Tp corresponding to the current reference voltage) from the time the burst wave is transmitted to the zero-cross point Pz identified by the zero-cross identifying means 7 (step S6).

[0055] Next, the peak detection means 10 determines whether or not the elapsed time calculation process using the reference voltage as the end voltage has been completed (step S7). If the elapsed time calculation process using the reference voltage as the end voltage has not been completed (No in step S7), the peak detection means 10 returns to the process of step S5 and repeats the subsequent processes. On the other hand, if the elapsed time calculation process using the reference voltage as the end voltage has been completed (Yes in step S7), the necessity determination means 9 determines whether or not it is necessary to redetermine the flow rate measurement reference voltage Vref based on the method described above (step S8).

[0056] If it is determined that redetermining the reference voltage Vref for flow rate measurement is not necessary (No in step S8), the process returns to step S1 and the subsequent processes are repeated. On the other hand, if it is determined that redetermining the reference voltage Vref for flow rate measurement is necessary (Yes in step S8), the peak detection means 10 changes the reference voltage in predetermined increments, setting the start voltage of the reference voltage to the minimum voltage (e.g., zero voltage) in the setting range of the reference voltage and the end voltage of the reference voltage to the maximum voltage (e.g., the voltage of the maximum amplitude of the amplified signal) in the setting range of the reference voltage (step S9).

[0057] The timer 8 measures the elapsed time Tp (the elapsed time Tp corresponding to the current reference voltage) from the time the burst wave is transmitted to the zero-cross point Pz identified by the zero-cross identifying means 7 (step S10).

[0058] Next, the peak detection means 10 determines whether or not the elapsed time calculation process using the reference voltage as the end voltage has been completed (step S11). If the elapsed time calculation process using the reference voltage as the end voltage has not been completed (No in step S11), the peak detection means 10 returns to the process of step S9 described above and repeats the subsequent processes. On the other hand, if the elapsed time calculation process using the reference voltage as the end voltage has been completed (Yes in step S11), the reference determination means 11 updates the flow rate measurement reference voltage Vref based on the multiple peak voltages detected by the peak detection means 10 (step S12). Thereafter, the process returns to the process of step S5 described above and repeats the subsequent processes.

[0059] As described above, according to the flow measurement device 100 of this embodiment, only when the necessity determination means 9 determines that redetermining the flow measurement reference voltage Vref is necessary based on a change in the voltage of the amplified signal of the received signal, the peak voltage detection process and the process of redetermining the flow measurement reference voltage Vref based on that peak voltage need to be performed. This makes it possible to avoid a decrease in calculation accuracy (calculation accuracy of the fluid flow velocity and flow rate) caused by the flow measurement reference voltage Vref, which has been set to be between predetermined peak voltages, deviating from that predetermined peak voltage range due to peak voltage fluctuations depending on the gas type. In addition, the number of times the ultrasonic signal is transmitted can be reduced, thereby suppressing an increase in current consumption.

[0060] It should be noted that the above-described embodiments are intended to illustrate the technology of the present disclosure, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents. For example, as follows:

[0061] In the above embodiment, the reference voltage when the elapsed time Tp changes suddenly is detected as the peak voltage of the amplified signal, but the method of detecting the peak voltage is not limited to this. As shown in FIG. 6 , in the relationship between the reference voltage and time A (the time from when the magnitude relationship between the amplified signal voltage and the reference voltage is inverted to the zero-crossing point Pz), each of the reference voltages corresponding to inflections Tp1, Tp2, Tp3, and Tp4, at which time A suddenly increases, may be detected as a peak voltage of the amplified signal. Even in this case, the difference p3-p2 between the peak voltage p3 of the third wave and the peak voltage p2 of the second wave is the largest, so the reference voltage Vref for flow rate measurement can be set between these peak voltages. As in the above embodiment, this avoids a decrease in calculation accuracy caused by the reference voltage Vref deviating from the above peak voltage range due to peak voltage fluctuations depending on the gas type.

[0062] Furthermore, in the above embodiment, the flow rate measurement reference voltage Vref is set between the peak voltage p3 of wave 3 and the peak voltage p2 of wave 2 of the amplified signal, but this is not limiting and it may be set between the peak voltage p4 of wave 4 and the peak voltage p3 of wave 3. The difference p4-p3 between the peak voltage p4 of wave 4 and the peak voltage p3 of wave 3 is smaller than the difference p3-p2 between the peak voltage p3 of wave 3 and the peak voltage p2 of wave 2, but the slope of the voltage change at the zero crossing point Pz becomes relatively steep, making it easier to identify the zero crossing point Pz. This improves the accuracy of measuring the elapsed time Tp, thereby improving the accuracy of calculating the flow velocity and flow rate.

[0063] In addition, in the above embodiment, the start voltage is the first voltage and the end voltage is the second voltage, but this is not limited to this, and the start voltage may be the second voltage and the end voltage may be the first voltage.

[0064] Furthermore, in the above embodiment, a burst wave is used as the drive signal from the transmitting means 4, but this is not limiting, and other drive signals may be used.

[0065] REFERENCE SIGNS LIST 1 fluid pipeline 2 first ultrasonic vibrator 3 second ultrasonic vibrator 4 transmitting means 5 switching means 6 amplification means 7 zero cross identifying means 8 timing means 9 necessity determining means 10 peak detecting means 11 reference determining means 12 calculation means 100 flow rate measuring device Pz zero cross point p1, p2, p3, p4, p5 peak voltage Tp elapsed time Vref reference voltage for flow rate measurement

Claims

a reference voltage determining means for determining a voltage between two adjacent peak voltages of the plurality of peak voltages as a reference voltage for flow measurement; and a calculation means for calculating a flow velocity and a flow rate of the fluid flowing through the fluid pipeline based on the elapsed time when the reference voltage for flow measurement is set to the reference voltage. and a necessity determination means for determining whether or not the reference voltage for flow measurement needs to be redetermined by the reference determination means based on the voltage of the amplified signal.

2. The flow measurement device according to claim 1, wherein the necessity determining means determines that the re-determination is necessary when, between two adjacent peak voltages, a voltage lower than the reference voltage for flow measurement is defined as a first voltage and a voltage higher than the reference voltage for flow measurement is defined as a second voltage, and when the reference voltage is changed in predetermined increments between the first voltage and the second voltage by the peak detection means, there is a voltage of the amplified signal at which the elapsed time obtained by the timing means in the predetermined increments changes at a rate of change or greater.

3. The flow measurement device as described in claim 1, wherein the necessity determining means determines that the redetermination is necessary when, when the peak detection means changes the reference voltage between the first voltage and the second voltage in predetermined increments, the voltage between two adjacent peak voltages is defined as a first voltage and a voltage higher than the higher of the two adjacent peak voltages is defined as a second voltage, and when there is no voltage of the amplified signal at which the elapsed time obtained by the timing means in the predetermined increments changes at a rate greater than or equal to a predetermined rate of change.

4. The flow measurement device according to claim 1, wherein said necessity determining means determines whether or not it is necessary to further determine again said reference voltage for flow measurement immediately after said reference voltage for flow measurement has been redetermined by said reference determining means.

5. The flow rate measurement device according to claim 1, wherein said necessity determining means determines whether or not it is necessary to redetermine said reference voltage for flow rate measurement immediately after power-on.

6. A flow measurement device as described in claim 1, wherein when the necessity determination means determines that the re-determination is necessary, the standard determination means re-determines the reference voltage for flow measurement a plurality of times at predetermined time intervals, and repeats the re-determination of the reference voltage for flow measurement until the variation of the re-determined reference voltages for flow measurement falls within a threshold value.

7. The flow rate measurement device according to claim 2 or 3, wherein said peak detection means changes said first voltage and said second voltage based on the detected peak voltage.

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