Ultrasonic flowmeter and flow rate calculation method

Abstract

To provide an ultrasonic flowmeter with which it is possible to reduce power consumption.SOLUTION: The present invention comprises: a position identification unit 401 for identifying the peak position of a prescribed wave that serves as an index to a maximum amplitude in received signals acquired by a received signal acquisition unit 403 and a received signal acquisition unit 404; a measurement period setting unit 402 for setting a period in which time measurement of a zero-cross point is conducted, on the basis of the peak position identified by the position identification unit; a zero-cross point measurement unit 405 for measuring the time from start of transmission to a zero-cross point in the period set by the measurement period setting unit, on the basis of the received signals acquired by the received signal acquisition units; a zero-cross point measurement unit 406 for measuring the time from start of transmission to a zero-cross point in the period set by the measurement period setting unit; and a stoppage control unit 409 for causing the received signal acquisition units and the zero-cross point measurement units to stop when measurements by the zero-cross point measurement units are finished.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic flowmeter that measures flow rate using ultrasonic waves and a flow rate calculation method. [Background technology]

[0002] 2. Description of the Related Art Conventionally, ultrasonic flowmeters are known that measure the flow rate of a fluid to be measured based on the difference in propagation time between ultrasonic waves transmitted and received by a pair of ultrasonic sensors. A known example of such an ultrasonic flow meter is a zero-crossing ultrasonic flow meter, which detects a predetermined number of zero-crossing points of the received signal after the received signal exceeds a threshold, measures the propagation time of the ultrasonic waves from transmission to detection of the zero-crossing points, and calculates the flow rate of the fluid based on the measured propagation time.

[0003] Such an ultrasonic flowmeter is equipped with an amplifier that amplifies the received signal and a comparator that compares the amplified received signal with the threshold value. However, a challenge with this ultrasonic flowmeter is how to reduce the power consumption of the receiver circuit that includes the amplifier and the comparator.

[0004] In conventional ultrasonic flowmeters, power is normally supplied to the amplification means and reference comparison means shortly (about 50 μs) before the arrival of the received signal, anticipating the arrival time of the received signal from the ultrasonic vibrator on the receiving side and taking into account the waiting time for stabilization of circuit operation, and the power is cut off shortly (about 10 to 20 μs) after the arrival of the received signal so that the maximum value of the received signal is included in order to adjust the gain of the amplification means. Furthermore, the amplifying means and the reference comparing means consume a current of about several hundred μA due to their functional characteristics of amplifying and generating a reference voltage, which accounts for the majority of the operating current of the ultrasonic flowmeter.

[0005] Therefore, a conventional technique has been disclosed in which the timing of cutting off the power to the amplifying means and the reference comparing means is changed depending on the two states of the power supply means, that is, when the gain is adjusted and when the gain is not adjusted (see, for example, Patent Document 1). This conventional technique can shorten the total operating time of the amplifying means and the reference comparing means during the measurement period, and can reduce current consumption. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3443659 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in conventional technology, the operating time of the receiving circuit (a circuit including an amplifier, comparator, etc.) is long when adjusting the gain (broadly speaking, when checking the strength of the received signal) to accommodate changes in the amplitude of the received signal. That is, in conventional technology, the gain of the amplifier is adjusted so that the received signal received by the ultrasonic vibrator on the receiving side has a constant amplitude. For the measurement times required for this, the power supply to the amplifier and comparator must be extended a little later (about 10 to 20 μs) after the arrival of the received signal so that the maximum value of the received signal is included. This is because the peak indicating the maximum amplitude, which is necessary to grasp the strength of the received signal, occurs later than the peak for obtaining the zero-crossing point used in flow measurement.

[0008] In addition, reducing current consumption is an important issue for ultrasonic flowmeters that require long-term battery-powered operation. In addition to simplifying the measurement and calculation operations, reducing current consumption by shortening the operating time of receiving circuits, including amplifiers and comparators that consume a large amount of current, is also an issue for such ultrasonic flowmeters.

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide an ultrasonic flowmeter that can reduce power consumption compared to conventional ultrasonic flowmeters. [Means for solving the problem]

[0010] The ultrasonic flowmeter according to the present invention includes a first received signal acquisition unit that acquires a received signal received by one of a pair of ultrasonic sensors that transmit and receive ultrasonic waves; a second received signal acquisition unit that acquires a received signal received by the other of the ultrasonic sensors; a position identification unit that identifies a peak position of a predetermined wave that is an index of the maximum amplitude in the received signals acquired by the first received signal acquisition unit and the second received signal acquisition unit; a measurement period setting unit that sets a period for measuring time to a zero crossing point based on the peak position identified by the position identification unit; and a measurement period setting unit that sets a period for measuring time from the start of transmission to a zero crossing point based on the received signal acquired by the first received signal acquisition unit for each of a plurality of unit measurement steps after the received signal exceeds a threshold value. a first zero-cross point measurement unit that measures time multiple times; a second zero-cross point measurement unit that measures time from the start of transmission to a zero-cross point multiple times during a period set by a measurement period setting unit after a received signal acquired by a second received signal acquisition unit exceeds a threshold for each of multiple unit measurement steps; a time difference calculation unit that calculates a time difference between a measurement result by the first zero-cross point measurement unit and a measurement result by the second zero-cross point measurement unit; a flow rate calculation unit that calculates a flow rate of a fluid to be measured based on a calculation result by the time difference calculation unit; and a stop control unit that stops the first received signal acquisition unit, the second received signal acquisition unit, the first zero-cross point measurement unit, and the second zero-cross point measurement unit when measurements by the first zero-cross point measurement unit and the second zero-cross point measurement unit are completed. a second amplitude acquisition unit that acquires, based on the received signals acquired by the first received signal acquisition unit and the second received signal acquisition unit, an amplitude at a peak position of a wave that is a starting point for performing the time measurement of the zero crossing point and a maximum amplitude of the wave for performing the time measurement of the zero crossing point; and a deviation determination unit that determines whether or not there is a deviation in the measurement period set by the measurement period setting unit, based on a ratio between the amplitude and the maximum amplitude acquired by the second amplitude acquisition unit, and the stop control unit delays the timing of the stop by a predetermined time when it is determined by the deviation determination unit that the deviation has occurred. It is characterized by: [Effects of the Invention]

[0011] According to the present invention, since it is configured as described above, it is possible to reduce power consumption compared to the prior art. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating a configuration example of an ultrasonic flowmeter according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a calculation unit according to the first embodiment. [Figure 3] 10 is a flowchart showing an example of a measurement period setting operation by a calculation unit in the first embodiment. [Figure 4] 5 is a flowchart showing an example of a flow rate calculation operation by a calculation unit in the first embodiment. [Figure 5] FIG. 4 is a diagram illustrating a specific example of the operation of a calculation unit according to the first embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of the configuration of a calculation unit according to a second embodiment. [Figure 7] FIG. 10 is a diagram illustrating a specific example of the operation of a calculation unit in the second embodiment. [Figure 8] FIG. 11 is a diagram illustrating an example of the configuration of a calculation unit according to a third embodiment. [Figure 9] 9A and 9B are diagrams showing a specific example of the operation of the calculation unit in the third embodiment. [Figure 10] FIG. 13 is a diagram illustrating an example of the configuration of a calculation unit according to a fourth embodiment. [Figure 11] FIG. 13 is a diagram showing a specific example of the operation of the calculation unit in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Embodiment 1 FIG. 1 is a diagram showing a configuration example of an ultrasonic flowmeter according to the first embodiment. An ultrasonic flow meter measures fluid using ultrasonic waves. As shown in Fig. 1, this ultrasonic flow meter includes a measuring pipe 1, ultrasonic sensors 2 and 3, and a calculation unit 4.

[0014] The measuring tube 1 is a cylindrical member through which a fluid to be measured flows.

[0015] The ultrasonic sensor 2 is an ultrasonic transducer that is attached to the upstream side of the side wall of the measuring pipe 1 and transmits and receives ultrasonic waves to and from the ultrasonic sensor 3 inside the measuring pipe 1. That is, the ultrasonic sensor 2 transmits ultrasonic waves to the downstream side (ultrasonic sensor 3) inside the measuring pipe 1, and receives ultrasonic waves from the downstream side (ultrasonic sensor 3) as a reception signal.

[0016] The ultrasonic sensor 3 is an ultrasonic transducer that is attached to the downstream side of the side wall of the measuring pipe 1 and transmits and receives ultrasonic waves to and from the ultrasonic sensor 2 within the measuring pipe 1. That is, the ultrasonic sensor 3 transmits ultrasonic waves to the upstream side (ultrasonic sensor 2) within the measuring pipe 1, and receives ultrasonic waves from the upstream side (ultrasonic sensor 2) as a reception signal.

[0017] The positional relationship between the ultrasonic sensors 2 and 3 is designed according to the propagation paths of the ultrasonic waves used by the ultrasonic sensors 2 and 3.

[0018] The calculation unit 4 calculates the flow rate of the fluid in the measuring pipe 1 based on the transmission and reception results of the ultrasonic sensors 2 and 3.

[0019] As shown in FIG. 2, this calculation unit 4 includes a position identification unit 401, a measurement period setting unit 402, a received signal acquisition unit (first received signal acquisition unit) 403, a received signal acquisition unit (second received signal acquisition unit) 404, a zero cross point measurement unit (first zero cross point measurement unit) 405, a zero cross point measurement unit (second zero cross point measurement unit) 406, a time difference calculation unit 407, a flow rate calculation unit 408, and a stop control unit 409.

[0020] The calculation unit 4 is realized by a processing circuit such as an IC (Integrated Circuit) or a system LSI (Large Scale Integration), or a CPU (Central Processing Unit) that executes a program stored in a memory or the like.

[0021] The position identifying unit 401 identifies the peak position of a predetermined wave, which is an index of the maximum amplitude in the received signals acquired by the received signal acquiring units 403 and 404. In this case, the position identifying unit 401 identifies the peak position of the predetermined wave, which is an index of the maximum amplitude in the received signals, based on, for example, the characteristics of the ultrasonic sensors 2 and 3 and the drive waveforms of the ultrasonic waves transmitted by the ultrasonic sensors 2 and 3. In the first embodiment, the position specifying unit 401 specifies the peak position of the maximum amplitude wave in the received signals acquired by the received signal acquiring unit 403 and the received signal acquiring unit 404 .

[0022] The measurement period setting unit 402 sets a measurement period based on the peak position identified by the position identifying unit 401. The measurement period is a period during which time measurement of the zero-crossing point is carried out. In this case, the measurement period setting unit 402 sets the measurement period so that it includes the peak position identified by the position identifying unit 401. Note that the measurement period setting unit 402 sets the threshold values ​​used by the zero-crossing point measuring units 405 and 406, thereby setting the measurement period.

[0023] The received signal acquisition unit 403 acquires the received signal received by the ultrasonic sensor 2. The received signal acquisition unit 403 has a function of amplifying (amplifying) the received signal acquired from the ultrasonic sensor 2. The amount of amplification (gain) of the received signal is set according to the maximum amplitude of the received signal acquired by the received signal acquisition unit 403, etc.

[0024] The received signal acquisition unit 404 acquires the received signal received by the ultrasonic sensor 3. The received signal acquisition unit 404 has a function of amplifying (amplifying) the received signal acquired from the ultrasonic sensor 3. The amount of amplification (gain) of the received signal is set according to the maximum amplitude of the received signal acquired by the received signal acquisition unit 404, etc.

[0025] After the received signal exceeds the threshold, the zero-crossing point measuring unit 405 measures the time from the start of transmission to the zero-crossing point multiple times during the period set by the measurement period setting unit 402, based on the acquisition result by the received signal acquiring unit 403. The zero-crossing point measuring unit 405 performs the above process for each of the multiple received signals (each unit measurement step). As shown in Fig. 5, for example, a zero-crossing point is a point at which the strength of a received signal becomes zero after it exceeds a threshold (threshold voltage) after reception starts. The threshold is set by the measurement period setting unit 402. In Fig. 5, reference numeral 51 indicates a zero-crossing point. The number of zero-crossing points at which the zero-crossing point measuring unit 405 measures time in one unit measurement step is set in advance. The number of unit measurement steps is also set in advance. The zero-crossing point measuring unit 405 has a function (comparator) of comparing the received signal with a threshold value.

[0026] After the received signal exceeds the threshold, the zero-crossing point measuring unit 406 measures the time from the start of transmission to the zero-crossing point multiple times during the period set by the measurement period setting unit 402, based on the acquisition result by the received signal acquiring unit 404. The zero-crossing point measuring unit 406 performs the above process for each of the multiple received signals (each unit measurement step). The number of zero crossing points at which the zero crossing point measuring section 406 measures time in one unit measurement step is set in advance, and the number of unit measurement steps is also set in advance. The zero-crossing point measuring unit 406 has a function (comparator) of comparing the received signal with a threshold value.

[0027] The operations of the received signal acquisition units 403 and 404 and the zero-crossing point measurement units 405 and 406 can be realized by a single circuit system. That is, the above operations can be realized by switching the connection between the above circuits and the ultrasonic sensors 2 and 3 depending on whether transmission and reception is in the forward direction or the reverse direction.

[0028] Time difference calculation unit 407 calculates the time difference between the measurement result by zero-cross point measurement unit 405 and the measurement result by zero-cross point measurement unit 406. In this case, first, time difference calculation unit 407 calculates an average value by averaging the measurement results in each unit measurement step by zero-cross point measurement unit 405 for each zero-cross point. Similarly, time difference calculation unit 407 calculates an average value by averaging the measurement results in each unit measurement step by zero-cross point measurement unit 406 for each zero-cross point. Then, time difference calculation unit 407 calculates the difference between the above two average values ​​for each zero-cross point, thereby calculating the time difference at each zero-cross point.

[0029] The flow rate calculation unit 408 calculates the flow rate of the fluid in the measuring pipe 1 based on the calculation result by the time difference calculation unit 407. The operating principle of the flow rate calculation unit 408 can be the same as that of a conventional flow rate calculation, and a description thereof will be omitted.

[0030] When the measurement by the zero-cross point measurement unit 405 and the zero-cross point measurement unit 406 is completed, the stop control unit 409 stops the received signal acquisition unit 403, the received signal acquisition unit 404, the zero-cross point measurement unit 405, and the zero-cross point measurement unit 406. In other words, the stop control unit 409 stops the receiving circuit including the amplifier, the comparator, etc. immediately after the time measurement of the zero-cross point is completed.

[0031] Next, an example of the operation of the calculation unit 4 in the first embodiment shown in FIG. 2 will be described. First, an example of the operation of setting the measurement period by the calculation unit 4 in the first embodiment shown in Fig. 2 will be described with reference to Fig. 3. The following describes a case where the position specifying unit 401 specifies the peak position of the maximum amplitude wave in the received signal.

[0032] In the example of the operation of setting the measurement period by the calculation unit 4 in the first embodiment shown in Fig. 2, first, as shown in Fig. 3, the position specifying unit 401 specifies the peak position of the maximum amplitude wave in the received signals acquired by the received signal acquiring units 403 and 404 (step ST301). At this time, the position specifying unit 401 specifies the peak position of the maximum amplitude wave in the received signals based on, for example, the characteristics of the ultrasonic sensors 2 and 3 and the drive waveforms of the ultrasonic waves transmitted by the ultrasonic sensors 2 and 3.

[0033] In this case, the position identifying unit 401 can identify the peak position of the maximum amplitude wave in the received signal by using, for example, the method disclosed in Patent Document 2. That is, as shown in FIG. 5, for example, the relationship between the target zero-crossing point (the first zero-crossing point) and the peak position of the maximum amplitude wave (the time difference indicated by reference numeral 52 in FIG. 5) is determined depending on the frequency of the ultrasonic waves and the characteristics of the ultrasonic sensors 2 and 3 used for transmission and reception, and can be considered to be largely unchanged. Therefore, by using the time difference as an initial value, the position identifying unit 401 can identify the peak position of the maximum amplitude wave according to the detection time of the target zero-crossing point. In the example of FIG. 5, the time difference is 2.75 periods, and the peak position of the maximum amplitude wave is located 2.75 periods after the detection time of the target zero-crossing point. In addition, the position identification unit 401 is not limited to using the detection time of the target zero crossing point, but can also identify the peak position of the maximum amplitude wave according to the detection times of other zero crossing points or peak positions in the received signal, using the same concept as above. [Patent Document 2] Japanese Patent Publication No. 2020-63972

[0034] Furthermore, for example, the position identifying unit 401 can also identify the peak position of the maximum amplitude wave using the voltage of the received signal. That is, in this case, the position identifying unit 401 detects the voltage peak of the received signal when the voltage of the received signal exceeds a set voltage level. Then, the position identifying unit 401 records the occurrence time (elapsed time from transmission) of the detected voltage peak and the voltage value at that time multiple times, compares the respective voltage peaks, and identifies the peak occurrence time at which the highest voltage is observed as the peak position of the maximum amplitude wave. Note that the position identifying unit 401 may perform the above operation by receiving ultrasound once, or may perform the operation by repeating transmission and reception multiple times.

[0035] Furthermore, for example, the position determination unit 401 may set a threshold value for detecting the maximum peak based on the voltage expected to be the peak of the maximum amplitude wave, and determine the time (the elapsed time from transmission) when the voltage of the received signal crosses the threshold value as the approximate peak position of the maximum amplitude wave.

[0036] Next, measurement period setting section 402 sets a measurement period based on the peak position identified by position identifying section 401 (step ST302). At this time, measurement period setting section 402 sets the measurement period so that it includes the peak position identified by position identifying section 401. At this time, measurement period setting section 402 desirably sets the measurement period so that the peak position overlaps with the latter half of the measurement period. Note that measurement period setting section 402 sets the measurement period by setting threshold values ​​used in zero-cross point measuring section 405 and zero-cross point measuring section 406.

[0037] Next, an example of the flow rate calculation operation by the calculation unit 4 in the first embodiment shown in FIG. 2 will be described with reference to FIG.

[0038] In the example of the flow rate calculation operation by the calculation unit 4 in the first embodiment shown in FIG. 2, first, as shown in FIG. 4, the received signal acquisition unit 403 and the received signal acquisition unit 404 acquire the received signal (step ST401). That is, the received signal acquisition unit 403 acquires the received signal received by the ultrasonic sensor 2. Similarly, the received signal acquisition unit 404 acquires the received signal received by the ultrasonic sensor 3 .

[0039] Next, for each unit measurement step, after the received signal exceeds the threshold, the zero-cross point measurement unit 405 and the zero-cross point measurement unit 406 measure the time from the start of transmission to the zero-cross point multiple times during the period set by the measurement period setting unit 402 (step ST402). That is, for each unit measurement step, the zero-crossing point measurement unit 405 measures the time from the start of transmission to the zero-crossing point multiple times during the period set by the measurement period setting unit 402 after the received signal exceeds the threshold value, based on the results acquired by the received signal acquisition unit 403. Similarly, for each unit measurement step, the zero-crossing point measurement unit 406 measures the time from the start of transmission to the zero-crossing point multiple times during the period set by the measurement period setting unit 402 after the received signal exceeds the threshold value, based on the results acquired by the received signal acquisition unit 404.

[0040] 5 shows a case where the zero-cross point measuring units 405 and 406 measure the times of seven zero-cross points in one unit measurement step. The number of unit measurement steps is, for example, 31.

[0041] The time of the m-th zero cross point in the k-th unit measurement step measured by the zero cross point measuring unit 405 is represented as ZCm(k). Furthermore, the time of the m-th zero cross point in the k-th unit measurement step measured by the zero cross point measuring unit 406 is represented as inverse ZCm(k).

[0042] Next, time difference calculation unit 407 calculates the time difference (ZCmΔt) between the measurement result by zero-cross point measurement unit 405 and the measurement result by zero-cross point measurement unit 406, as shown in the following equation (1) (step ST403). At this time, time difference calculation unit 407 first calculates an average value by averaging the measurement results in each unit measurement step by zero-cross point measurement unit 405 for each zero-cross point. Similarly, time difference calculation unit 407 calculates an average value by averaging the measurement results in each unit measurement step by zero-cross point measurement unit 406 for each zero-cross point. Then, time difference calculation unit 407 calculates the difference between the above two average values ​​for each zero-cross point, thereby calculating the time difference at each zero-cross point. ZCmΔt=(ΣReverse ZCm(k) / k)-(ΣOrder ZCm(k) / k) (1)

[0043] Next, the flow rate calculation unit 408 calculates the flow rate of the fluid in the measuring pipe 1 based on the calculation result by the time difference calculation unit 407 (step ST404). At this time, when using a conventional method, for example, the flow rate calculation unit 408 can calculate the flow rate of the fluid based on the time difference (Δt) calculated according to the following formula (2). Δt=ΣZCmΔt / m (2)

[0044] When the measurement by the zero-cross point measurement unit 405 and the zero-cross point measurement unit 406 is completed, the stop control unit 409 stops the received signal acquisition unit 403, the received signal acquisition unit 404, the zero-cross point measurement unit 405, and the zero-cross point measurement unit 406. That is, the stop control unit 409 stops the receiving circuit including the amplifier, the comparator, etc. immediately after the time measurement of the zero-cross point is completed.

[0045] In order to reduce the current consumption of conventional ultrasonic flowmeters, it is important to shorten the operating time of the receiving circuit (a circuit including an amplifier and a comparator) for each transmission and reception operation. On the other hand, it is necessary to grasp the strength of the ultrasonic reception signal and adjust the settings of the receiving circuit (the gain in the amplifier and the threshold used in the comparator) according to the strength of the received ultrasonic signal. In contrast, in the ultrasonic flowmeter according to the first embodiment, the measurement period is set so as to overlap (particularly overlap the latter half of) the peak position of a predetermined wave in the received signal (in the first embodiment, the peak position of the maximum amplitude wave). Then, the ultrasonic flowmeter according to the first embodiment stops the power supply to the receiving circuits (received signal acquisition unit 403, received signal acquisition unit 404, zero-cross point measurement unit 405, and zero-cross point measurement unit 406) as soon as the time measurement of the zero-cross point is completed. This makes it possible for the ultrasonic flowmeter according to the first embodiment to shorten the operating time of the receiving circuit and reduce power consumption compared to conventional ones. Furthermore, in the ultrasonic flowmeter according to the first embodiment, by setting the measurement period so as to overlap the position of the maximum amplitude, it is possible to constantly acquire information indicating the strength of the received signal (amplitude information).

[0046] Next, a specific example of the operation of the calculation unit 4 in the first embodiment shown in Fig. 2 will be described with reference to Fig. 5. Note that Fig. 5 shows a case where the calculation unit 4 measures seven zero-crossing points. The number of zero-crossing points and the wave number in Fig. 5 are just an example.

[0047] In FIG. 5, the ultrasonic sensors 2 and 3 transmit six ultrasonic waves, and the seventh wave generates the maximum amplitude in the received signal. In this case, the calculation unit 4 sets the threshold value so that the peak position of the wave three cycles before the maximum amplitude wave is the peak position of the wave to be tracked (the peak position of the wave that serves as the starting point for measuring the time of the zero-crossing point). This allows the latter half of the measurement period to be set so that it includes the peak position of the maximum amplitude wave. In Figure 5, reference numeral 53 denotes the measurement period, and reference numeral 54 denotes the period of the maximum amplitude wave in the received signal. Then, as soon as the calculation unit 4 has completed time measurement for the number of zero crossing points required for flow rate measurement, it stops supplying power to the receiving circuit. This makes it possible to observe the maximum amplitude in the received signal while shortening the operating time of the receiving circuit and reducing power consumption.

[0048] As described above, according to the first embodiment, the ultrasonic flowmeter includes a received signal acquisition unit 403 that acquires a received signal received by one ultrasonic sensor 2, a received signal acquisition unit 404 that acquires a received signal received by the other ultrasonic sensor 3, a position identification unit 401 that identifies a peak position of a predetermined wave that is an index of the maximum amplitude in the received signals acquired by the received signal acquisition units 403 and 404, a measurement period setting unit 402 that sets a period for measuring the time of a zero-crossing point based on the peak position identified by the position identification unit 401, and a zero crossing time measurement unit that measures the time from the start of transmission to the zero-crossing point multiple times within the period set by the measurement period setting unit 402 based on the received signal acquired by the received signal acquisition unit 403 for each of multiple unit measurement steps after the received signal exceeds a threshold. the zero-cross point measuring unit 405, the zero-cross point measuring unit 406 that measures the time from the start of transmission to the zero-cross point multiple times during the period set by the measurement period setting unit 402 after the received signal acquired by the received signal acquiring unit 404 exceeds the threshold for each of multiple unit measurement steps, a time difference calculating unit 407 that calculates the time difference between the measurement result by the zero-cross point measuring unit 405 and the measurement result by the zero-cross point measuring unit 406, a flow rate calculating unit 408 that calculates the flow rate of the fluid to be measured based on the calculation result by the time difference calculating unit 407, and a stop control unit 409 that stops the received signal acquiring unit 403, the received signal acquiring unit 404, the zero-cross point measuring unit 405, and the zero-cross point measuring unit 406 when the measurements by the zero-cross point measuring unit 405 and the zero-cross point measuring unit 406 are completed. As a result, the ultrasonic flowmeter according to the first embodiment can reduce power consumption compared to conventional ultrasonic flowmeters.

[0049] Embodiment 2 In the ultrasonic flowmeter according to the first embodiment, the position identifying unit 401 identifies the peak position of the maximum amplitude wave in the received signal, and the measurement period setting unit 402 sets the measurement period so that the peak position of the maximum amplitude wave is included in the measurement period. In contrast, in the second embodiment, a configuration example will be described in which it is difficult to include the peak position of the maximum amplitude wave in the measurement period.

[0050] Fig. 6 is a diagram showing an example of the configuration of the calculation unit 4 in embodiment 2. In the calculation unit 4 in embodiment 2 shown in Fig. 6, an amplitude acquisition unit 410 and an amplitude calculation unit 411 are added to the calculation unit 4 in embodiment 1 shown in Fig. 2. The other example of the configuration of the calculation unit 4 in embodiment 2 shown in Fig. 6 is similar to the example of the configuration of the calculation unit 4 in embodiment 1 shown in Fig. 2, and the same reference numerals are used, and only the different parts will be described.

[0051] In addition, the position identifying unit 401 in the second embodiment identifies the peak position of a predetermined wave, other than the maximum amplitude wave, which is an index of the maximum amplitude, in the received signals acquired by the received signal acquiring unit 403 and the received signal acquiring unit 404.

[0052] The amplitude acquisition unit 410 acquires the amplitude at the peak position identified by the position identification unit 401 based on the received signals acquired by the received signal acquisition unit 403 and the received signal acquisition unit 404 .

[0053] The amplitude calculation unit 411 calculates the maximum amplitude of the received signals acquired by the received signal acquisition unit 403 and the received signal acquisition unit 404 based on the amplitude acquired by the amplitude acquisition unit 410. In this case, the amplitude calculation unit 411 calculates the maximum amplitude using the ratio between the reference amplitude at the peak position identified by the position identification unit 401 and the reference maximum amplitude. Note that the ratio is a constant or a function of temperature or propagation time.

[0054] The maximum amplitude of the received signal calculated by this amplitude calculation unit 411 is used, for example, to set the amplification amount (gain) of the received signal in the received signal acquisition units 403 and 404, to set threshold values ​​used in the zero-cross point measurement units 405 and 406, or for various judgments, etc.

[0055] Next, a specific example of the operation of the calculation unit 4 in the second embodiment shown in Fig. 6 will be described with reference to Fig. 7. Note that Fig. 7 shows a case where the calculation unit 4 measures seven zero-crossing points. The number of zero-crossing points and the wave number in Fig. 7 are just an example.

[0056] In the calculation unit 4 in the second embodiment, as shown in FIG. 7, the amplitude acquisition unit 410 acquires an amplitude (Vpd-indi (actual measurement value)) that serves as a guide for the maximum amplitude (Vpd) in the received signal, instead of the maximum amplitude (Vpd). Then, the amplitude calculation unit 411 calculates the actual maximum amplitude (Vpd (estimated value)) from the amplitude (Vpd-indi (actual measurement value)) acquired by the amplitude acquisition unit 410, using the ratio between Vpd (reference value) and Vpd-indi (reference value). In the example of FIG. 6, Vpd (estimated value) can be calculated as Vpd-indi (actual measurement value) * 1.05 ≈ Vpd (estimated value), etc. In FIG. 7, reference numeral 71 indicates a zero-crossing point, reference numeral 72 indicates a measurement period, and reference numeral 73 indicates a wave period for which the amplitude acquisition unit 410 acquires the amplitude.

[0057] The calculation unit 4 may use a representative value or a moving average based on multiple measurement values ​​as Vpd-indi (actual measurement value) in order to avoid the influence of random errors and improve the accuracy of the determination.

[0058] The configuration of the ultrasonic flowmeter according to the second embodiment is considered to be effective when it is difficult to overlap the measurement period with the peak position of the maximum amplitude wave in the received signal, such as when it is desired to measure the zero crossing point before the amplitude of the received signal becomes large, or when there are few zero crossing points required for flow measurement.

[0059] Embodiment 3 In the first and second embodiments, the operating time of the receiving circuit is shortened to reduce power consumption. In this case, the short operating time of the receiving circuit may easily cause erroneous measurement of the maximum amplitude. Therefore, in the third embodiment, a configuration example for solving the above-mentioned problem will be described.

[0060] Fig. 8 is a diagram showing an example of the configuration of the calculation unit 4 in embodiment 3. In the calculation unit 4 in embodiment 3 shown in Fig. 8, an amplitude acquisition unit (second amplitude acquisition unit) 412 and a deviation determination unit 413 are added to the calculation unit 4 in embodiment 1 shown in Fig. 2. The other example of the configuration of the calculation unit 4 in embodiment 3 shown in Fig. 8 is similar to the example of the configuration of the calculation unit 4 in embodiment 1 shown in Fig. 2, and the same reference numerals are used, and only the different parts will be described.

[0061] The amplitude acquisition unit 412 acquires the amplitude at the peak position of the wave to be tracked (the amplitude at the peak position of the wave that is the starting point for measuring the time of the zero crossing point) and the maximum amplitude based on the received signals acquired by the received signal acquisition unit 403 and the received signal acquisition unit 404.

[0062] The deviation determination unit 413 determines whether or not there is a deviation in the measurement period set by the measurement period setting unit 402, based on the amplitude acquired by the amplitude acquisition unit 412. In this case, the deviation determination unit 413 uses the ratio of the reference amplitude and the reference maximum amplitude at the peak position of the wave to be tracked to determine the difference from the amplitude ratio acquired by the amplitude acquisition unit 410. If the difference is equal to or greater than a threshold, the deviation determination unit 413 determines that there is a deviation in the measurement period. Note that the ratio of the reference amplitude and the reference maximum amplitude at the peak position of the wave to be tracked is a constant or a function of temperature or propagation time.

[0063] If deviation determining section 413 determines that a deviation has occurred, stop control section 409 in the third embodiment delays the stop timing of the receiving circuit by a predetermined time.

[0064] Next, a specific example of the operation of the calculation unit 4 in the third embodiment shown in Fig. 8 will be described with reference to Fig. 9. Note that Fig. 9 shows a case where the calculation unit 4 measures seven zero-crossing points. The number of zero-crossing points and the wave number in Fig. 9 are just an example.

[0065] As shown in FIG. 9 , in the calculation unit 4 of the third embodiment, the amplitude acquisition unit 412 acquires the amplitude (Vsp (actual measurement value)) and maximum amplitude (Vpd (actual measurement value)) at the peak position of the wave to be tracked in the received signal. Then, the deviation determination unit 413 uses the ratio of Vsp (reference value) to Vpd (reference value) to determine whether the measurement period has shifted by comparing the ratio of Vsp (actual measurement value) and Vpd (actual measurement value), which are the amplitudes acquired by the amplitude acquisition unit 412. If the deviation determination unit 413 determines that a deviation has occurred, the stop control unit 409 delays the stop timing by a predetermined time. This allows the calculation unit 4 to acquire Vpd over a wide time range in the next measurement, making it possible to grasp the appropriate strength of the received signal.

[0066] 9A shows a case where the measurement period and the peak position of the maximum amplitude wave overlap (when there is no misalignment). In FIG. 9A, reference numeral 91 indicates the zero-crossing point, reference numeral 92 indicates the measurement period, and reference numeral 93 indicates the period of the maximum amplitude wave in the received signal. In this case, the amplitude acquisition unit 412 can acquire the correct Vsp as Vsp (actual measurement value) and the correct Vpd as Vpd (actual measurement value). In this case, Vsp (actual measurement value) / Vpd (actual measurement value)≈0.72.

[0067] On the other hand, Fig. 9B shows a case where the measurement period and the maximum amplitude peak position do not overlap (a case where a shift occurs). Fig. 9B shows a case where the measurement period is shifted one cycle earlier than when the measurement period is normal. In Fig. 9B, reference numeral 94 indicates the period of the maximum amplitude wave in the received signal (shifted). In this case, the amplitude acquisition unit 412 acquires an incorrect Vsp (Vsp-fault) as Vsp (actual measurement value) and an incorrect Vdp (Vpd-fault) as Vpd (actual measurement value). In this case, Vsp (actual measurement value) / Vpd (actual measurement value) is approximately 0.53, and it can be determined that the measurement period has deviated from the original position, causing a deviation.

[0068] The calculation unit 4 may use a representative value or a moving average based on multiple measurement values ​​as Vsp (measured value) and Vpd (measured value) in order to avoid the influence of random errors and improve the accuracy of the determination.

[0069] Here, it is ideal to observe the received signal over a wide range to obtain the maximum amplitude, but in the ultrasonic flowmeters according to the first and second embodiments, the operating time of the receiving circuit is narrowed to reduce current consumption. Therefore, in the ultrasonic flowmeter according to the third embodiment, in order to reduce the risk of erroneous measurement that occurs as a result of the above, a deviation in the measurement period is determined based on the ratio of the amplitude at the peak position of the wave to be tracked in the received signal to the maximum amplitude. Then, in the ultrasonic flowmeter according to the third embodiment, if it is determined that a deviation in the measurement period has occurred, the maximum amplitude is obtained by observing the received signal over a wide range in the next measurement.

[0070] In addition to the above operations, the calculation unit 4 may also be configured to determine the appropriate strength of the received signal by extending the time period during which the maximum amplitude is acquired and acquiring Vpd over a wide time range in cases where there is a sudden change in TOF or temperature, or where there is a possibility that appropriate flow measurement has not been performed.

[0071] In the above description, an amplitude acquisition unit 412 and a deviation determination unit 413 are added to the calculation unit 4 in the first embodiment. However, the present invention is not limited to this, and an amplitude acquisition unit 412 and a deviation determination unit 413 may be added to the calculation unit 4 in the second embodiment, and the same effects as those described above can be obtained.

[0072] Embodiment 4 In the fourth embodiment, a configuration example will be described in which the threshold value is set to a value higher than that in normal times, thereby making it easier to obtain the maximum amplitude in the received signal.

[0073] Fig. 10 is a diagram showing an example of the configuration of the calculation unit 4 in embodiment 4. In the calculation unit 4 in embodiment 4 shown in Fig. 10, a threshold value changing unit 414 and an amplitude acquisition unit (third amplitude acquisition unit) 415 are added to the calculation unit 4 in embodiment 1 shown in Fig. 2. The other example of the configuration of the calculation unit 4 in embodiment 4 shown in Fig. 10 is similar to the example of the configuration of the calculation unit 4 in embodiment 1 shown in Fig. 2, and the same reference numerals are used, and only the different parts will be described.

[0074] Threshold value changing section 414 changes the threshold value used in zero-cross point measuring section 405 and zero-cross point measuring section 406. At this time, threshold value changing section 414 changes the threshold value to a value greater than normal.

[0075] In the measurement using the threshold value changed by the threshold value changing unit 414, the amplitude acquiring unit 415 acquires the maximum amplitude of the received signal based on the acquisition results by the received signal acquiring units 403 and 404.

[0076] Next, a specific example of the operation of the calculation unit 4 in the fourth embodiment shown in Fig. 10 will be described with reference to Fig. 11. Note that Fig. 11 shows a case where the calculation unit 4 measures seven zero-crossing points. The number of zero-crossing points and the wave number in Fig. 11 are just an example.

[0077] 11, when Vs is used as the threshold, the calculation unit 4 puts the receiving circuit into a pause state upon completing measurements of ZC1 to ZC7. However, the maximum amplitude wave in the received signal may be located after ZC7 due to deformation of the received waveform caused by disturbances or fluctuations in voltage. In this case, the calculation unit 4 cannot correctly obtain the maximum amplitude (Vpd). Therefore, the threshold value changing unit 414 changes the threshold value to VsH, which allows the calculation unit 4 to operate the receiving circuit until the measurement of ZC5 to ZC11 is completed, thereby making it possible to reliably acquire Vpd. In FIG. 11, reference numeral 111 indicates the zero crossing point, reference numeral 112 indicates the measurement period when the threshold is Vs, reference numeral 113 indicates the period of the maximum amplitude wave in the received signal, and reference numeral 114 indicates the measurement period when the threshold is VsH.

[0078] An example of threshold value change by the threshold value change unit 414 is an operation of alternately setting multiple levels of threshold value as disclosed in Patent Document 2, and the calculation unit 4 may acquire the maximum amplitude in synchronization with the time when a higher threshold value is set in this operation. In this case, Vpd can be reliably acquired without changing the normal flow rate measurement operation and threshold value setting operation, and without affecting the flow rate measurement accuracy.

[0079] In the ultrasonic flowmeter according to the fourth embodiment, it is possible to reduce the possibility that the measurement period will end before the maximum amplitude of the received signal due to disturbances such as voltage fluctuations in the received signal, and that the maximum amplitude will not be obtained.

[0080] In the above description, a case has been shown in which the threshold value changing unit 414 and the amplitude acquiring unit 415 are added to the calculation unit 4 in the first embodiment. However, the present invention is not limited to this, and the threshold value changing unit 414 and the amplitude acquiring unit 415 may be added to the calculation unit 4 in the second and third embodiments, and the same effects as those described above can be obtained. Furthermore, the threshold value changing unit 414 and the amplitude acquiring unit 415 in the fourth embodiment may be configured to operate in response to a determination that there is a suspicion that the maximum amplitude has not been acquired correctly in the third embodiment (i.e., when the deviation determining unit 413 determines that a deviation has occurred).

[0081] It should be noted that within the scope of the present invention, the embodiments may be freely combined, or any of the components of the embodiments may be modified, or any of the components of the embodiments may be omitted. [Explanation of symbols]

[0082] 1 Measuring tube 2 Ultrasonic sensors 3 Ultrasonic Sensor 4 Arithmetic section 401 Location identification part 402 Measurement period setting unit 403 Received signal acquisition unit (first received signal acquisition unit) 404 Received signal acquisition unit (second received signal acquisition unit) 405 Zero-crossing point measurement unit (first zero-crossing point measurement unit) 406 Zero-crossing point measurement unit (second zero-crossing point measurement unit) 407 Time Difference Calculation Unit 408 Flow rate calculation section 409 Stop control section 410 Amplitude acquisition section 411 Amplitude calculation section 412 amplitude acquisition unit (second amplitude acquisition unit) 413 Deviation judgment unit 414 Threshold change unit 415 Amplitude acquisition unit (third amplitude acquisition unit)

Claims

1. a first received signal acquisition unit that acquires a received signal received by one of a pair of ultrasonic sensors that transmit and receive ultrasonic waves; a second received signal acquisition unit that acquires a received signal received by the other of the ultrasonic sensors; a position specifying unit that specifies a peak position of a predetermined wave that is an index of a maximum amplitude in the received signals acquired by the first received signal acquiring unit and the second received signal acquiring unit; a measurement period setting unit that sets a period for measuring time at zero crossing points based on the peak position identified by the position identifying unit; a first zero-crossing point measuring unit that measures the time from the start of transmission to a zero-crossing point multiple times during a period set by the measurement period setting unit after the received signal acquired by the first received signal acquiring unit exceeds a threshold for each of multiple unit measurement steps; a second zero-crossing point measuring unit that measures the time from the start of transmission to a zero-crossing point multiple times during the period set by the measurement period setting unit after the received signal acquired by the second received signal acquiring unit exceeds a threshold for each of multiple unit measurement steps; a time difference calculation unit that calculates a time difference between a measurement result by the first zero-cross point measurement unit and a measurement result by the second zero-cross point measurement unit; a flow rate calculation unit that calculates the flow rate of the fluid to be measured based on the calculation result by the time difference calculation unit; a stop control unit that stops the first received signal acquisition unit, the second received signal acquisition unit, the first zero-cross point measurement unit, and the second zero-cross point measurement unit when measurements by the first zero-cross point measurement unit and the second zero-cross point measurement unit are completed; a second amplitude acquisition unit that acquires, based on the received signals acquired by the first received signal acquisition unit and the second received signal acquisition unit, an amplitude at a peak position of a wave that is a starting point for performing time measurement of the zero crossing points, and a maximum amplitude of the wave for performing time measurement of the zero crossing points; a deviation determination unit that determines whether or not there is a deviation in the measurement period set by the measurement period setting unit based on a ratio between the amplitude acquired by the second amplitude acquisition unit and a maximum amplitude, The stop control unit delays the stop timing by a predetermined time when the deviation determination unit determines that the deviation has occurred.

1. An ultrasonic flow meter comprising:

2. The measurement period setting unit sets a threshold value based on the maximum amplitude in the received signal calculated from the amplitude of the predetermined wave, and sets a period for performing time measurement of the zero crossing point based on the threshold value and the peak position identified by the position identifying unit, a threshold value changing unit that alternately sets the threshold value set by the measurement period setting unit and a threshold value greater than the threshold value for each unit measurement step; and a third amplitude acquisition unit that acquires a maximum amplitude of the received signal based on the results of acquisition by the first received signal acquisition unit and the second received signal acquisition unit in the unit measurement step in which the threshold value change unit sets the large threshold value.

2. The ultrasonic flowmeter according to claim 1.

3. The measurement period setting unit sets a threshold value based on the maximum amplitude in the received signal calculated from the amplitude of the predetermined wave, and sets a period for performing time measurement of the zero crossing point based on the threshold value and the peak position identified by the position identifying unit, a threshold value changing unit that changes the threshold value used by the first zero-cross point measuring unit and the second zero-cross point measuring unit to a value greater than the threshold value set by the measurement period setting unit when the deviation determining unit determines that a deviation has occurred; and a third amplitude acquisition unit that acquires a maximum amplitude of the received signal based on the acquisition results by the first received signal acquisition unit and the second received signal acquisition unit in the measurement using the threshold value changed by the threshold change unit.

2. The ultrasonic flowmeter according to claim 1.

4. a step in which a first received signal acquisition unit acquires a received signal received by one of a pair of ultrasonic sensors that transmit and receive ultrasonic waves; a second received signal acquiring unit acquiring a received signal received by the other of the ultrasonic sensors; a step in which a position specifying unit specifies a peak position of a predetermined wave that is an index of a maximum amplitude in the received signals acquired by the first received signal acquiring unit and the second received signal acquiring unit; a measurement period setting unit setting a period for measuring the time of zero crossing points based on the peak position identified by the position identifying unit; a step in which a first zero-crossing point measuring unit measures a time from the start of transmission to a zero-crossing point multiple times during a period set by the measurement period setting unit after the received signal acquired by the first received signal acquiring unit exceeds a threshold for each of multiple unit measurement steps; a step in which a second zero-crossing point measuring unit measures a time from the start of transmission to a zero-crossing point multiple times during a period set by the measurement period setting unit after the received signal acquired by the second received signal acquiring unit exceeds a threshold for each of multiple unit measurement steps; a time difference calculation unit calculating a time difference between a measurement result by the first zero-cross point measurement unit and a measurement result by the second zero-cross point measurement unit; a flow rate calculation unit calculating a flow rate of the fluid to be measured based on the calculation result by the time difference calculation unit; a stop control unit stopping the first received signal acquisition unit, the second received signal acquisition unit, the first zero-cross point measurement unit, and the second zero-cross point measurement unit when measurements by the first zero-cross point measurement unit and the second zero-cross point measurement unit are completed; a second amplitude acquisition unit acquiring, based on the received signals acquired by the first received signal acquisition unit and the second received signal acquisition unit, an amplitude at a peak position of a wave that is a starting point for performing time measurement of the zero crossing point, and a maximum amplitude of the wave for performing time measurement of the zero crossing point; a deviation determining unit determining whether or not there is a deviation in the measurement period set by the measurement period setting unit based on a ratio between the amplitude acquired by the second amplitude acquiring unit and the maximum amplitude; when the deviation determination unit determines that the deviation has occurred, the stop control unit delays the timing of the stop by a predetermined time; A flow rate calculation method using an ultrasonic flowmeter having the above structure.

5. The measurement period setting unit sets a threshold value based on the maximum amplitude in the received signal calculated from the amplitude of the predetermined wave, and sets a period for performing time measurement of the zero crossing point based on the threshold value and the peak position identified by the position identifying unit, a step in which a threshold value changing unit alternately sets the threshold value set by the measurement period setting unit and a threshold value greater than the threshold value set by the measurement period setting unit for each unit measurement step; and a step in which, in the unit measurement step in which the threshold value changing unit sets the large threshold value, a third amplitude acquiring unit acquires a maximum amplitude in the received signal based on the results of acquisition by the first received signal acquiring unit and the second received signal acquiring unit.

5. The method for calculating a flow rate using an ultrasonic flowmeter according to claim 4.

6. The measurement period setting unit sets a threshold value based on the maximum amplitude in the received signal calculated from the amplitude of the predetermined wave, and sets a period for performing time measurement of the zero crossing point based on the threshold value and the peak position identified by the position identifying unit, a threshold value changing unit changing the threshold value used by the first zero-cross point measuring unit and the second zero-cross point measuring unit to a value greater than the threshold value set by the measurement period setting unit when the deviation determining unit determines that a deviation has occurred; and a step in which a third amplitude acquisition unit acquires a maximum amplitude of the received signal based on the acquisition results by the first received signal acquisition unit and the second received signal acquisition unit, in the measurement using the threshold value changed by the threshold change unit.

5. The method for calculating a flow rate using an ultrasonic flowmeter according to claim 4.

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