Information processing device and ultrasonic flowmeter

Abstract

To provide an information processing device and an ultrasonic flowmeter which can further suppress a change in hierarchical relationship between a plurality of voltage values than possible before.SOLUTION: An information processing device (100) comprises: a voltage value acquisition unit (30) for acquiring a first voltage value at a first peak of a pulse signal including a first peak and a second peak and a second voltage value at a second peak that is greater than the first voltage value; a change information acquisition unit (41) for acquiring first change information pertaining to a first change amount which is a positive change amount of the first voltage value and second change information pertaining to a second change amount which is a negative change amount of the second voltage value; and a specific voltage value setting unit (145) for setting a specific voltage value between the first and the second voltage values as a specific voltage value on the basis of the first and second voltage values and the first and second change information.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an information processing apparatus and an ultrasonic flowmeter.

Background Art

[0002] Conventionally, there has been known an apparatus for measuring the flow rate of a fluid to be measured based on the propagation times of a signal output from one of a pair of ultrasonic transducers, input to the other ultrasonic transducer through the fluid to be measured, and a signal output from the other ultrasonic transducer, input to the one ultrasonic transducer through the fluid to be measured (see Patent Document 1). The apparatus described in Patent Document 1 calculates the propagation time of the signal based on the zero-crossing time of the voltage value of the signal after a reference voltage value is set in advance and the voltage value of the signal reaches the reference voltage value. Further, the apparatus described in Patent Document 1 sets such a reference voltage value to the voltage value at the midpoint between the peak voltage values of the second and third waves of the received signal.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, in an ultrasonic flowmeter such as the apparatus described in Patent Document 1, in order to ensure sufficient measurement accuracy, it is required that the vertical relationship among the peak voltage value of the second wave, the peak voltage value of the third wave, and the reference voltage value does not change. However, these peak voltage values of the second wave and the third wave may change due to the influence of various factors during measurement. Thus, there is a problem that when the peak voltages of the second and third waves change, the vertical relationship among the peak voltage value of the second wave, the peak voltage value of the third wave, and the reference voltage value may change.

[0005] The present disclosure solves the above problems, and an object thereof is to provide an information processing apparatus and an ultrasonic flowmeter capable of suppressing changes in the vertical relationship between a plurality of voltage values.

Means for Solving the Problems

[0006] The information processing apparatus according to the present disclosure includes a voltage value acquisition unit that acquires a first voltage value of a first peak of a pulse signal including a first peak and a second peak, and a second voltage value of a second peak that is larger than the first voltage value; a variation information acquisition unit that acquires first variation information regarding a first variation amount that is a positive variation amount of the first voltage value, and second variation information regarding a second variation amount that is a negative variation amount of the second voltage value; and a specific voltage value setting unit that sets a specific voltage value between the first voltage value and the second voltage value as a specific voltage value based on the first voltage value, the second voltage value, the first variation information, and the second variation information.

Effects of the Invention

[0007] According to the present disclosure, based on the first variation information indicating the variation amount of the first voltage value and the second variation information indicating the variation amount of the second voltage value, a specific voltage value between the first voltage value and the second voltage value is set as the specific voltage value. Therefore, even when the first voltage value and the second voltage value vary, it is possible to suppress a change in the vertical relationship between the first voltage value, the second voltage value, and the specific voltage value more than before.

Brief Description of the Drawings

[0008]

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Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the drawings. Embodiment 1. FIG. 1 is a schematic diagram showing the configuration of the flow measurement system according to Embodiment 1. As shown in FIG. 1, the flow measurement system according to Embodiment 1 includes a measurement pipe 1 which is a tubular member through which a fluid to be measured flows inside, transducers 2 and 3 having ultrasonic vibrators (not shown), a flow calculation device 100 as an ultrasonic flow meter for measuring the flow rate of the fluid flowing inside the measurement pipe 1, and an input device 90 for inputting information to the flow calculation device 100.

[0010] The transducer 2 as a signal generation unit is disposed on the side wall of the measurement pipe 1. The transducer 2 outputs a second ultrasonic wave which is a pulse wave of a plurality of cycles toward the inside of the measurement pipe 1, and receives the first ultrasonic wave output from the transducer 3. The transducer 3 is disposed on one side of the upstream and downstream of the transducer 2 on the side wall of the measurement pipe 1. The transducer 3 outputs a first ultrasonic wave which is a pulse wave of a plurality of cycles toward the inside of the measurement pipe 1, and receives the second ultrasonic wave output from the transducer 2. Configured in this way, the pair of transducers 2 and 3 are configured such that the ultrasonic wave output from one is input to the other through the fluid flowing inside the measurement pipe 1. In other words, the pair of transducers 2 and 3 are configured such that the ultrasonic wave output from one is propagated to the other using the fluid flowing inside the measurement pipe 1 as a medium. The transducers 2 and 3 convert the input ultrasonic wave into a voltage signal and transmit it to the flow rate calculation device 100.

[0011] FIG. 2 is a block diagram showing a schematic configuration of the flow rate measurement system according to Embodiment 1. The flow rate calculation device 100 as an ultrasonic flow meter calculates the flow rate of the fluid flowing inside the measurement pipe 1 based on the signals from the transducers 2 and 3. As shown in FIG. 2, the flow rate calculation device 100 includes a first signal acquisition unit 10, a second signal acquisition unit 20, a voltage value acquisition unit 30, a reference voltage value control unit 140, a propagation time calculation unit 50, a time difference calculation unit 60, a flow rate calculation unit 70, and a storage unit 80.

[0012] The first signal acquisition unit 10 acquires a first ultrasonic signal, which is a pulse signal of a plurality of cycles, based on the first ultrasonic wave input to the transducer 2. In other words, the first signal acquisition unit 10 acquires a first ultrasonic signal, which is a pulse signal of a plurality of cycles, based on the first ultrasonic wave input to the ultrasonic vibrator included in the transducer 2. For example, the first signal acquisition unit 10 acquires the first ultrasonic signal, which is a signal from the transducer 2. Also, for example, the first signal acquisition unit 10 acquires the first ultrasonic signal, which is a signal with the gain of the signal from the transducer 2 adjusted.

[0013] The second signal acquisition unit 20 acquires a second ultrasonic signal, which is a pulse signal of a plurality of cycles, based on the second ultrasonic wave input to the transducer 3. In other words, the second signal acquisition unit 20 acquires a second ultrasonic signal, which is a pulse signal of a plurality of cycles, based on the second ultrasonic wave input to the ultrasonic vibrator included in the transducer 3. For example, the second signal acquisition unit 20 acquires the second ultrasonic signal, which is a signal from the transducer 3. Also, for example, the second signal acquisition unit 20 acquires the second ultrasonic signal, which is a signal with the gain of the signal from the transducer 3 adjusted.

[0014] Note that when the first signal acquisition unit 10 and the second signal acquisition unit 20 are configured to acquire signals with the gains of the signals from the transducers 2 and 3 adjusted, the flow rate calculation device may include a gain adjustment unit (not shown) that adjusts the gains of the signals from the transducers 2 and 3.

[0015] The voltage value acquisition unit 30 acquires the peak voltage value of each wave of the first ultrasonic signal and the peak voltage value of each wave of the second ultrasonic signal based on the first ultrasonic signal acquired by the first signal acquisition unit 10 and the second ultrasonic signal acquired by the second signal acquisition unit 20. For example, the voltage value acquisition unit 30 acquires the peak voltage value of the second wave of the first ultrasonic signal, the peak voltage value of the third wave of the first ultrasonic signal, and the maximum peak voltage value of the first ultrasonic signal, and the peak voltage value of the second wave of the second ultrasonic signal, the peak voltage value of the third wave of the second ultrasonic signal, and the maximum peak voltage value of the second ultrasonic signal, based on the first ultrasonic signal acquired by the first signal acquisition unit 10 and the second ultrasonic signal acquired by the second signal acquisition unit 20.

[0016] In addition, in Embodiment 1, the peak of the second wave of the first ultrasonic signal is also referred to as the first peak, the peak of the third wave of the first ultrasonic signal is also referred to as the second peak, the voltage value of the first peak is also referred to as the first voltage value, and the voltage value of the second peak is also referred to as the second voltage value. Further, in Embodiment 1, the maximum peak voltage value refers to the maximum voltage value of the ultrasonic signal from the start to the end of the input of the ultrasonic wave to each transducer. In other words, the maximum peak voltage value of the first ultrasonic signal refers to the maximum voltage value of the first ultrasonic signal from the start to the end of the acquisition of the first ultrasonic signal, and the maximum peak voltage value of the second ultrasonic signal refers to the maximum voltage value of the second ultrasonic signal from the start to the end of the acquisition of the second ultrasonic signal. Therefore, assuming that the second voltage value is greater than the first voltage value, the voltage value acquisition unit 30 acquires the first voltage value of the first peak, the second voltage value of the second peak greater than the first voltage value, and the maximum peak voltage value for the first ultrasonic signal including the first peak and the second peak, and acquires the first voltage value of the first peak, the second voltage value of the second peak greater than the first voltage value, and the maximum peak voltage value for the second ultrasonic signal including the first peak and the second peak.

[0017] The reference voltage value control unit 140 includes a variation information acquisition unit 41 and a reference voltage value setting unit 145. The variation information acquisition unit 41 acquires information indicating the amount of variation in the peak voltage value of each wave of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30 due to various factors. For example, the peak voltage value of each wave of the first ultrasonic signal and the second ultrasonic signal varies due to the temperature of the flow measurement system, the temperature of the fluid flowing inside the measurement tube 1, the flow velocity of the fluid flowing inside the measurement tube 1, and the difference in pressure of the fluid flowing inside the measurement tube 1.

[0018] Also, for example, the peak voltage value of each wave of the first ultrasonic signal and the second ultrasonic signal varies due to the difference in the type of fluid flowing inside the measurement tube 1. In other words, the peak voltage value of each wave of the first ultrasonic signal and the second ultrasonic signal varies due to the difference in the physical properties of the fluid being measured. For example, the physical properties of the fluid differ depending on the difference in the substances that make up the fluid when the fluid is composed of a single substance, and differ depending on the difference in each substance that makes up the fluid and the difference in the ratio of each substance when the fluid is composed of a plurality of substances. Specifically, the peak voltage value of each wave of the first ultrasonic signal and the second ultrasonic signal varies depending on whether the fluid flowing inside the measurement tube 1 is propane gas or city gas, and also varies depending on the ratio of each gas that makes up the city gas.

[0019] Also, for example, the transducers 2, 3 may deteriorate in parts and the adhesive bonding a plurality of parts due to the elapsed time since the transducers 2, 3 were produced and the number of uses. In other words, the transducers 2, 3 may deteriorate in parts and the adhesive bonding a plurality of parts due to the aging change since the transducers 2, 3 were produced. In such a case, the peak voltage value of each wave of the first ultrasonic signal and the second ultrasonic signal varies depending on the elapsed time since the transducers 2, 3 as products were produced and the number of uses. Also, for example, the peak voltage value of each wave of the first ultrasonic signal and the second ultrasonic signal varies due to errors caused by noise in the environment and other accidental errors.

[0020] The variation information acquisition unit 41 acquires information indicating the amount of variation in the peak voltage value of each wave of the first ultrasonic signal and the second ultrasonic signal that varies due to such various factors. For example, the variation information acquisition unit 41 acquires information indicating the amount of variation in the peak voltage value of each wave of the first ultrasonic signal and the second ultrasonic signal based on the input signal from the input device 90.

[0021] Also, for example, the variation information acquisition unit 41 acquires information indicating the amount of variation in the first voltage value of the second wave of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30, and information indicating the amount of variation in the second voltage value of the third wave of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30. Specifically, the variation information acquisition unit 41 acquires first variation information indicating a first variation amount, which is the positive variation amount of the first voltage value of the second wave of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30, and second variation information indicating a second variation amount, which is the negative variation amount of the second voltage value of the third wave of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30.

[0022] For example, various factors that cause the first voltage value and the second voltage value to vary include temperature, the flow rate of the medium through which the pulse signal propagates, the pressure of the medium through which the pulse signal propagates, the elapsed time since the transducers 2 and 3 were produced, the number of times the transducers 2 and 3 have been used, and random errors. In other words, the first variation amount includes any one or a plurality of the following: the variation amount of the first voltage value due to the difference in temperature, the variation amount of the first voltage value due to the difference in the flow rate of the medium through which the pulse signal propagates, the variation amount of the first voltage value due to the difference in the pressure of the fluid through which the pulse signal propagates, the variation amount of the first voltage value due to the difference in the physical properties of the medium through which the pulse signal propagates, the variation amount of the first voltage value due to the elapsed time since the transducers 2 and 3 were produced, the variation amount of the first voltage value due to the number of times the transducers 2 and 3 have been used, and the variation amount of the first voltage value due to random errors. Also, the second variation amount includes any one or a plurality of the following: the variation amount of the second voltage value due to the difference in temperature, the variation amount of the second voltage value due to the difference in the flow rate of the medium through which the pulse signal propagates, the variation amount of the second voltage value due to the difference in the pressure of the fluid through which the pulse signal propagates, the variation amount of the second voltage value due to the difference in the physical properties of the medium through which the pulse signal propagates, the variation amount of the second voltage value due to the elapsed time since the transducers 2 and 3 were produced, the variation amount of the second voltage value due to the number of times the transducers 2 and 3 have been used, and the variation amount of the second voltage value due to random errors.

[0023] For example, the variation information acquisition unit 41 acquires information indicating the variation amount of the first voltage value and information indicating the variation amount of the second voltage value based on the results of measuring the first voltage value and the second voltage value under a plurality of conditions corresponding to various factors causing the first voltage value and the second voltage value to vary. Specifically, the variation information acquisition unit 41 measures the first voltage value and the second voltage value within the temperature range in which the flow measurement system can be used, which is preset, within the temperature range of the fluid for which the flow rate can be measured by the preset flow rate calculation device 100, within the flow velocity range of the fluid for which the flow rate can be measured by the preset flow rate calculation device 100, and within the pressure range of the fluid for which the flow rate can be measured by the preset flow rate calculation device 100. By changing the measurement conditions and based on the results of measuring the first voltage value and the second voltage value for various fluids for which the flow rate is expected to be measured by the flow rate calculation device 100, the variation information acquisition unit 41 acquires information indicating the variation amount of the first voltage value and information indicating the variation amount of the second voltage value.

[0024] Also, specifically, the variation information acquisition unit 41 acquires information indicating the variation amount of the first voltage value and information indicating the variation amount of the second voltage value based on the results of measuring the first voltage value and the second voltage value in ultrasonic flow rate systems with different elapsed times and usage frequencies since the transducers 2 and 3 were produced. Also, specifically, the variation information acquisition unit 41 acquires information indicating the variation amount of the first voltage value and information indicating the variation amount of the second voltage value based on the representative value of the variation amount of the results of measuring the first voltage value and the second voltage value in a plurality of ultrasonic flow rate systems.

[0025] For example, regarding the first and second variation amounts related only to the temperature of the flow rate measurement system, when the usable temperature range of the flow rate measurement system is from -40°C to 70°C, with other conditions being the same except for temperature, at -40°C (the lowest temperature), 20°C (the reference temperature), and 70°C (the highest temperature) respectively, the first voltage value and the second voltage value are measured with n (n is a natural number, the same hereinafter) flow rate measurement systems. If the average value of the measurement results of the first voltage value at -40°C is -1 mV relative to the average value of the first voltage value of the measurement results at 20°C, and the average value of the measurement results of the first voltage value at 70°C is +5 mV relative to the average value of the first voltage value of the measurement results at 20°C, the first variation amount is +5 mV. Also, if the average value of the measurement results of the second voltage value at -40°C is -2 mV relative to the average value of the second voltage value of the measurement results at 20°C, and the average value of the measurement results of the first voltage value at 70°C is +6 mV relative to the average value of the first voltage value of the measurement results at 20°C, the second variation amount is 2 mV. For example, in this way, by only measuring the maximum and minimum values of the usable temperature range and estimating the variation amount, the work can be reduced. For example, by obtaining the first and second variation amounts at the upper and lower limits of the usage conditions and using these as representative values, the variation amount across the entire usage temperature range can be simply estimated. Thereby, the measurement time required to grasp the characteristics of the variation amount can be significantly shortened. Similarly, when fluctuations in the composition of the fluid to be measured are expected, by obtaining the variation amount at the upper and lower limits of the molecular weight of the fluid to be measured, the variation amount for the entire fluid to be used can be estimated in a short time in the same way as for temperature. Also, for example, from past tests, the variation amount can be estimated more quickly by measuring only the temperature, flow rate, and physical properties of the medium, which are generally factors that greatly affect the variation amount. For example, the applicant has identified that in a flow rate measurement system for gases, the factors that strongly affect the first and second variation amounts are temperature, physical properties of the medium, and flow rate. By obtaining representative values of the variation amount for all or part of these factors, it becomes possible to estimate the variation amount that occurs under actual usage conditions in a short time.

[0026] Thus, the first variation amount and the second variation amount are numerical values obtained based on measurement results under specific conditions. For example, the first variation amount and the second variation amount may be numerical values obtained based on the average value of the measurement results under specific conditions, or may be numerical values obtained based on the maximum value of the absolute values of the measurement results under specific conditions, or may be numerical values obtained based on the mode of the measurement results under specific conditions, or may be numerical values obtained based on the median of the measurement results under specific conditions.

[0027] Note that when the first variation amount and the second variation amount are obtained by calculation, the variation information acquisition unit 41 may be configured to acquire the first variation information and the second variation information based on the calculation results of the first variation amount and the second variation amount, or may be configured to acquire the first variation information and the second variation information based on the estimation results of the first variation amount and the second variation amount estimated by a specific learned model.

[0028] The reference voltage value setting unit 145 as the specific voltage value setting unit sets a specific voltage value that serves as a reference when calculating the propagation speed of the ultrasonic wave output from the transducers 2 and 3 with the fluid as the medium, and a reference voltage value as the set voltage value, based on the first ultrasonic signal and the second ultrasonic signal acquired by the first signal acquisition unit 10 and the second signal acquisition unit 20, and the first variation information and the second variation information acquired by the variation information acquisition unit 41. For example, the reference voltage value setting unit 145 sets a specific voltage value between the first voltage value and the second voltage value of the first ultrasonic signal as the first reference voltage value as the first specific voltage value that is the reference voltage value, based on the first voltage value, the second voltage value, the first variation information, and the second variation information of the first ultrasonic signal. Also, for example, the reference voltage value setting unit 145 sets a specific voltage value between the first voltage value and the second voltage value of the second ultrasonic signal as the second reference voltage value as the second specific voltage value that is the reference voltage value, based on the first voltage value, the second voltage value, the first variation information, and the second variation information of the second ultrasonic signal.

[0029] When setting the first reference voltage value, the reference voltage value setting unit 145 takes into account the first variation information and the second variation information of the first ultrasonic signal, and even when the first voltage value and the second voltage value vary, sets the first reference voltage value so that the first reference voltage value is between the first voltage value and the second voltage value of the first ultrasonic signal. Similarly, when setting the second reference voltage value, the reference voltage value setting unit 145 takes into account the first variation information and the second variation information of the second ultrasonic signal, and even when the first voltage value and the second voltage value vary, sets the first reference voltage value so that the second reference voltage value is between the first voltage value and the second voltage value of the second ultrasonic signal. Details of the reference voltage value setting unit 145 will be described later.

[0030] The propagation time calculation unit 50 acquires output time information indicating the first output time when the first ultrasonic wave is output from the transducer 3 and the second output time when the second ultrasonic wave is output from the transducer 2, and based on the output time information, the first ultrasonic wave signal and the second ultrasonic wave signal acquired by the first signal acquisition unit 10 and the second signal acquisition unit 20, and the first reference voltage value and the second reference voltage value set by the reference voltage value control unit 140, calculates the propagation time of the first ultrasonic wave and the second ultrasonic wave output from the transducers 2 and 3 with the fluid as the medium. For example, the propagation time calculation unit 50 calculates the propagation time of the first ultrasonic wave based on the time from the first output time to the zero-crossing time, which is the time when the sign of the voltage value of the first ultrasonic wave signal changes after the voltage value of the first ultrasonic wave signal reaches the reference voltage value. Note that since the process of calculating the propagation time of the second ultrasonic wave is the same as the process of calculating the propagation time of the first ultrasonic wave, the description thereof is omitted.

[0031] The time difference calculation unit 60 calculates the difference between the propagation time of the first ultrasonic wave and the propagation time of the second ultrasonic wave acquired by the propagation time calculation unit 50.

[0032] The flow rate calculation unit 70 calculates the flow rate of the fluid flowing inside the measurement pipe 1 based on the calculation result by the propagation time calculation unit 50. For example, the flow rate calculation unit 70 calculates the flow rate of the fluid flowing inside the measurement pipe 1 based on the following mathematical formulas (1) and (2). Here, v is the velocity of the fluid, L is the distance between the transducer 2 and the transducer 3 in the fluid flow direction, T1 is the propagation time of the first ultrasonic wave, T2 is the propagation time of the second ultrasonic wave, S is the cross-sectional area of the measurement pipe 1, Φ is the sensor angle (the angle formed by the fluid flow direction and the ultrasonic wave transmission direction from the transducer), and Q indicates the flow rate. v=(L / (2*cosΦ))*(1 / T2 - 1 / T1) ···(1) Q = v*S ···(2)

[0033] The storage unit 80 stores the information acquired by each part of the flow rate calculation device 100, the information used when the flow rate calculation device 100 performs various processes, and the information regarding the results of these various processes. For example, the storage unit 80 stores the information regarding the signals acquired by the first signal acquisition unit 10 and the second signal acquisition unit 20, the information indicating the reference voltage value set by the reference voltage value control unit 140, the information regarding the measurement conditions when the flow rate calculation device 100 measures the flow rate of the fluid, the information regarding the type of fluid measured in the past, and the like.

[0034] Configured in this way, the flow rate calculation device 100, based on the first ultrasonic wave signal and the second ultrasonic wave signal acquired by the first signal acquisition unit 10 and the second signal acquisition unit 20, and the reference voltage value set by the reference voltage value control unit 140, calculates the propagation time of the first ultrasonic wave and the second ultrasonic wave with the fluid as the medium output from the transducers 2 and 3 by the propagation time calculation unit 50. Based on the propagation time calculated by the propagation time calculation unit 50, the time difference calculation unit 60 calculates the difference between the propagation time of the first ultrasonic wave and the propagation time of the second ultrasonic wave. Based on the calculation result by the time difference calculation unit 60, the flow rate calculation unit 70 calculates the flow rate of the fluid. Note that the voltage value acquisition unit 30 and the reference voltage value control unit 140 described above constitute the information processing device in the first embodiment.

[0035] Next, with reference to FIGS. 3 and 4, the hardware configuration of the flow rate calculation device 100 will be described. FIG. 3 is a block diagram showing an example of the hardware configuration of the flow rate calculation device 100 according to Embodiment 1, and FIG. 4 is a block diagram showing an example of a hardware configuration different from that of FIG. 3 of the flow rate calculation device 100 according to Embodiment 1. For example, as shown in FIG. 3, the flow rate calculation device 100 includes a processor 100a, a memory 100b, and an I / O port 100c, and is configured such that the processor 100a reads and executes a program stored in the memory 100b. The memory 100b may be a non-volatile or volatile semiconductor memory such as, for example, RAM, ROM, flash memory, EPROM, or EEPROM. Further, the memory 100b may be a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, or the like. Furthermore, the memory 100b may be an HDD or an SSD.

[0036] Also, for example, as shown in FIG. 4, the flow rate calculation device 100 includes a processing circuit 100d, which is dedicated hardware, and an I / O port 100c. The processing circuit 100d is configured by, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, a system LSI (Large-Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. Each function of the flow rate calculation device 100 is realized by the processor 100a or the processing circuit 100d, which is dedicated hardware, executing a program that is software, firmware, or a combination of software and firmware. Note that, in addition to the above hardware, the flow rate calculation device 100 may include other hardware such as a hardware timer.

[0037] Next, with reference to FIGS. 2, 5 to 6, the details of the processing performed by the flow rate calculation device 100 according to Embodiment 1 will be described. FIG. 5 is a flowchart showing the reference voltage value setting process performed by the flow rate calculation device 100 according to Embodiment 1. The reference voltage value setting process shown in FIG. 5 is a process for the flow rate calculation device 100 to set a first reference voltage value related to the first ultrasonic signal. For example, the reference voltage value setting process is a process performed at a predetermined timing when the flow rate calculation device 100 is shipped from the manufacturing factory that manufactures the flow rate calculation device 100. Also, for example, the reference voltage value setting process is a process performed when the user uses the flow rate calculation device 100. Note that the process for the flow rate calculation device 100 to set the first reference voltage value related to the first ultrasonic signal and the process for the flow rate calculation device 100 to set the second reference voltage value related to the second ultrasonic signal are the same. Therefore, hereinafter, the process for the flow rate calculation device 100 to set the first reference voltage value related to the first ultrasonic signal will be described, and the description of the process for the flow rate calculation device 100 to set the second reference voltage value related to the second ultrasonic signal will be omitted.

[0038] As shown in FIG. 5, when the process starts, the flow rate calculation device 100 acquires a first voltage value and a second voltage value (step ST1). For example, in this process, the flow rate calculation device 100 acquires, by the voltage value acquisition unit 30, the first voltage value that is the peak voltage value of the second wave and the second voltage value that is the peak voltage value of the third wave, based on the first ultrasonic signal acquired by the first signal acquisition unit 10.

[0039] After performing the process of step ST1, next, the flow rate calculation device 100 acquires first variation information and second variation information (step ST2). For example, in this process, the flow rate calculation device 100 acquires, by the variation information acquisition unit 41, the first variation information indicating the variation amount of the peak voltage value of the second wave and the second variation information that is the variation amount of the peak voltage value of the third wave.

[0040] When the process of step ST2 is performed, next, the flow rate calculation device 100 calculates a reference voltage value (step ST3). In this process, the flow rate calculation device 100 calculates the reference voltage value by the reference voltage value setting unit 145 based on the first ultrasonic signal and the second ultrasonic signal acquired by the first signal acquisition unit 10 and the second signal acquisition unit 20.

[0041] FIG. 6 is a graph showing the first ultrasonic signal acquired by the first signal acquisition unit according to Embodiment 1. For example, as shown in FIG. 6, in the process of step ST3, the flow rate calculation device 100 sets the first reference voltage value V0 to be a value between the first voltage value V2 which is the peak voltage value of the second wave P2 of the first ultrasonic signal and the second voltage value V3 which is the peak voltage value of the third wave P3 of the first ultrasonic signal. For example, as shown in the following formula (3), the flow rate calculation device 100 calculates the first reference voltage value V0 to be a value between the voltage value obtained by adding the first variation amount ΔV2 to the first voltage value V2 and the voltage value obtained by subtracting the second variation amount ΔV3 from the second voltage value V3. V2 + ΔV2 ≦ V0 ≦ V3 - ΔV3 ···(3)

[0042] Also, for example, the flow rate calculation device 100 calculates the first reference voltage value after weighting by the reference voltage value setting unit 145 for each of various factors that cause the first voltage value and the second voltage value to vary. Specifically, when the first variation amount ΔV2 is composed of the variation amount ΔV2a due to accidental error and the variation amount ΔV2b due to other factors, and the second variation amount ΔV3 is composed of the variation amount ΔV3a due to accidental error and the variation amount ΔV3b due to other factors, if the weighting coefficient of the variation amount ΔV2a and the variation amount ΔV3a is M, and the weighting coefficient of the variation amount ΔV2b and the variation amount ΔV3b is N, then the flow rate calculation device 100 calculates the first reference voltage value as shown in the following formula (4). Note that it is desirable that both M and N are 1 or more (1 ≦ M, N). Also, generally, since the variation amount due to accidental error is more difficult to predict than the variation amount due to other errors, it is desirable that M is set to a value larger than N (M > N). V2+(M*ΔV2a+N*ΔV2a)≦V0≦V3-(M*ΔV3a+N*ΔV3a) ···(4)

[0043] When the process of step ST3 is performed, next, the flow rate calculation device 100 stores the reference voltage value in the storage unit 80 (step ST11). In this process, the flow rate calculation device 100 causes the storage unit 80 to store the first reference voltage value V0 calculated by the reference voltage value setting unit 145. When calculating the flow rate of the subsequent fluid, by using the first reference voltage value calculated in the process of step ST3, when the voltage value of the first ultrasonic signal reaches the reference voltage value, based on the zero-crossing time t1 which is the time when the sign of the voltage value of the first ultrasonic signal first switches after the time t0, it is possible to calculate the flow rate of the fluid. Multiple zero-crossing times may be used. When the process of step ST11 is performed, the flow rate calculation device 100 ends the reference value setting process.

[0044] As described above, the flow rate calculation device 100 according to the first embodiment includes a voltage value acquisition unit 30 that acquires the first voltage value of the first peak of the pulse signal including the first peak and the second peak, and the second voltage value of the second peak that is greater than the first voltage value; a variation information acquisition unit 41 that acquires first variation information indicating a first variation amount that is a positive variation amount of the first voltage value, and second variation information indicating a second variation amount that is a negative variation amount of the second voltage value; and a reference voltage value setting unit 145 that sets a specific voltage value between the first voltage value and the second voltage value as the reference voltage value based on the first voltage value, the second voltage value, the first variation information, and the second variation information. Generally, in an apparatus that performs processing based on the vertical relationship of a plurality of acquired voltage values, it is desirable that the vertical relationship of these voltage values does not change due to errors. For example, in the flow rate calculation device 100 according to Embodiment 1, based on the vertical relationship between a preset reference voltage value, the peak voltage value of the second wave and the peak voltage value of the third wave of the received signal, in an apparatus for measuring the flow rate of a fluid flowing inside the measurement tube 1, the reference voltage value is required to be set to a value that can ensure a margin for both the peak voltage value of the second wave and the peak voltage value of the third wave. However, for example, when setting the reference voltage value to the voltage value at the midpoint of the peak voltage values of the second and third waves acquired in advance, if the peak voltage values of the second and third waves vary by different amounts due to factors such as temperature change, flow rate change, gas type change, pressure change, and sensor aging, the vertical relationship between the reference voltage, the peak voltage value of the second wave, and the peak voltage value of the third wave may change.

[0045] In contrast, the flow rate calculation device 100 according to Embodiment 1 configured as described above sets a specific voltage value between the first voltage value and the second voltage value as the reference voltage value based on the first variation information indicating the variation amount of the first voltage value acquired in advance and the second variation information indicating the variation amount of the second voltage value. Therefore, even when the first voltage value and the second voltage value vary by different amounts due to various factors, the change in the vertical relationship among the first voltage value, the second voltage value, and the reference voltage value can be suppressed more than before.

[0046] Also, the flow rate calculation device 100 according to Embodiment 1 is configured to set a specific voltage value between the voltage value obtained by adding the first variation amount to the first voltage value and the voltage value obtained by subtracting the second variation amount from the second voltage value as the reference voltage value. Configured in this way, the flow rate calculation device 100 can prevent the change in the vertical relationship among the first voltage value, the second voltage value, and the reference voltage value even when the first voltage value and the second voltage value vary.

[0047] Note that in Embodiment 1, the flow rate calculation device 100 is configured to set a specific voltage value between the peak voltage of the second wave and the peak voltage of the third wave as the reference voltage value, but it is not limited thereto. The flow rate calculation device may be configured to set a specific voltage value between the first voltage value of the first peak of the pulse signal including the first peak and the second peak and the second voltage value of the second peak larger than the first voltage value as the specific voltage value based on the first variation information indicating the first variation amount that is the positive variation amount of the first voltage value and the second variation information indicating the second variation amount that is the negative variation amount of the second voltage value. For example, the first voltage value may be the peak voltage of the first wave of the pulse signal and the second voltage value may be the peak voltage of the second wave of the pulse signal, or the first voltage value may be the peak voltage of the third wave of the pulse signal and the second voltage value may be the peak voltage of the fourth wave of the pulse signal, or the second voltage value may be the maximum peak voltage value of the pulse signal. However, it is desirable that the second voltage value is a peak adjacent to the first peak later.

[0048] Also, in Embodiment 1, the flow rate calculation device 100 is configured to set a specific voltage value between the voltage value obtained by adding the first variation amount to the first voltage value and the voltage value obtained by subtracting the second variation amount from the second voltage value as the specific voltage value, but it is not limited thereto. The flow rate calculation device may be configured to set a specific voltage value between the first voltage value of the first peak of the pulse signal including the first peak and the second peak and the second voltage value of the second peak larger than the first voltage value as the specific voltage value based on the first variation information indicating the first variation amount that is the positive variation amount of the first voltage value and the second variation information indicating the second variation amount that is the negative variation amount of the second voltage value. For example, the flow rate calculation device may be configured to set a specific voltage value between the voltage value obtained by adding a value obtained by multiplying the first variation amount by a weighting coefficient less than 1 to the first voltage value and the voltage value obtained by subtracting a value obtained by multiplying the second variation amount by a weighting coefficient less than 1 from the second voltage value as the specific voltage value. Also, the weighting coefficient multiplied by the first variation amount and the weighting coefficient multiplied by the second variation amount may be the same value or different values from each other.

[0049] Further, the first variation information and the second variation information are not limited to information indicating the first variation amount and the second variation amount. The first variation information and the second variation information may be any information related to the first variation amount and the second variation amount. For example, the first variation information and the second variation information may be information indicating the ratio of the first variation amount to the maximum peak voltage value and information indicating the ratio of the second variation amount to the maximum peak voltage value, respectively. Specifically, as shown in the following mathematical formula (5), the reference voltage value setting unit can set the reference voltage value based on such first variation information and second variation information (see FIG. 6). Here, Vmax represents the maximum peak voltage value, δV2 represents the ratio of the first variation amount to the maximum peak voltage value, and δV3 represents the ratio of the second variation amount to the maximum peak voltage value. V2 + Vmax * δV2 ≤ V0 ≤ V3 - ΔVmax * δV3 ···(5)

[0050] Embodiment 2. Next, with reference to FIGS. 7 to 10, the flow rate calculation device 200 according to Embodiment 2 will be described. The flow rate calculation device 200 according to Embodiment 2 has a different configuration of the reference voltage value control unit from the flow rate calculation device 100 according to Embodiment 1, but the other configurations are the same. For the same configurations as those in Embodiment 1, the same names and reference numerals as those in Embodiment 1 will be given and the description will be omitted.

[0051] FIG. 7 is a block diagram showing a schematic configuration of a flow rate measurement system according to Embodiment 2. As shown in FIG. 7, the flow rate calculation device 200 according to Embodiment 2 includes a first signal acquisition unit 10, a second signal acquisition unit 20, a voltage value acquisition unit 30, a reference voltage value control unit 240, a propagation time calculation unit 50, a time difference calculation unit 60, a flow rate calculation unit 70, and a storage unit 80. The reference voltage value control unit 240 includes a variation information acquisition unit 41, a setting information acquisition unit 42, an upper and lower limit setting unit 244, and a reference voltage value setting unit 245.

[0052] The variation information acquisition unit 41 according to Embodiment 2 acquires information indicating the amount of variation in the peak voltage value of each wave of the first ultrasonic signal and the second ultrasonic signal that vary due to various factors. For example, the variation information acquisition unit 41 acquires information indicating the amount of variation in the first voltage value, which is the peak voltage value of the first wave of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30, information indicating the amount of variation in the third voltage value, which is the peak voltage value of the second wave of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30, and information indicating the amount of variation in the second voltage value, which is the peak voltage value of the third wave of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30.

[0053] Specifically, the variation information acquisition unit 41 acquires first variation information indicating a first variation amount, which is a positive variation amount of the first voltage value of the first wave (first peak) of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30, third variation information indicating a third variation amount, which is a negative variation amount of the third voltage value of the second wave (third peak) of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30, fourth variation information indicating a fourth variation amount, which is a positive variation amount of the third voltage value of the second wave of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30, and second variation information indicating a second variation amount, which is a negative variation amount of the second voltage value of the third wave (second peak) of the first ultrasonic signal and the second ultrasonic signal acquired by the voltage value acquisition unit 30.

[0054] The setting information acquisition unit 42 acquires setting information, which is information regarding the first reference voltage value and the second reference voltage value set by the reference voltage value setting unit 245. For example, the setting information acquisition unit 42 acquires setting information indicating voltage values corresponding to the first reference voltage value and the second reference voltage value that the user intends to set based on an input operation of the user on the input device 90.

[0055] The upper and lower limit setting unit 244 as the specific voltage value setting unit sets the upper limit voltage value and the lower limit voltage value of the first reference voltage value and the second reference voltage value set by the reference voltage value setting unit 245. For example, based on the first voltage value, the second voltage value, the first variation information, and the second variation information of the first ultrasonic signal, the upper and lower limit setting unit 244 sets two specific voltage values between the first voltage value and the second voltage value of the first ultrasonic signal as the upper limit voltage value and the lower limit voltage value of the first reference voltage value, and based on the first voltage value, the second voltage value, the first variation information, and the second variation information of the second ultrasonic signal, sets two specific voltage values between the first voltage value and the second voltage value of the second ultrasonic signal as the upper limit voltage value and the lower limit voltage value of the second reference voltage value.

[0056] In other words, based on the first voltage value, the second voltage value, the first variation information, and the second variation information of the first ultrasonic signal, the upper and lower limit setting unit 244 sets a specific voltage value between the first voltage value and the second voltage value of the first ultrasonic signal as the lower limit voltage value of the first reference voltage value, and based on the first voltage value, the second voltage value, the first variation information, and the second variation information of the first ultrasonic signal, sets a specific voltage value that is a voltage value greater than or equal to the lower limit voltage value of the first reference voltage value between the first voltage value and the second voltage value of the first ultrasonic signal as the upper limit voltage value of the first reference voltage value. Based on the first voltage value, the second voltage value, the first variation information, and the second variation information of the second ultrasonic signal, the upper and lower limit setting unit 244 sets a specific voltage value between the first voltage value and the second voltage value of the second ultrasonic signal as the lower limit voltage value of the second reference voltage value, and based on the first voltage value, the second voltage value, the first variation information, and the second variation information of the second ultrasonic signal, sets a specific voltage value that is a voltage value greater than or equal to the lower limit voltage value of the second reference voltage value between the first voltage value and the second voltage value of the second ultrasonic signal as the upper limit voltage value of the second reference voltage value. Note that the upper limit voltage value and the lower limit voltage value of the first reference voltage value and the second reference voltage value constitute the specific voltage value in Embodiment 2. Details of the upper and lower limit setting unit 244 will be described later.

[0057] The reference voltage value setting unit 245 sets a reference voltage value based on the information acquired by the setting information acquisition unit 42 and the upper and lower limit voltage values of the reference voltage value set by the upper and lower limit setting unit 244. For example, the reference voltage value setting unit 245 sets a reference voltage value based on the voltage value acquired by the voltage value acquisition unit 30. Hereinafter, an example of a configuration in which the reference voltage value setting unit 245 sets a reference voltage value based on the voltage value acquired by the voltage value acquisition unit 30 will be described.

[0058] First, initially, the reference voltage value setting unit 245 sets the peak voltage of the second wave of the ultrasonic signal acquired in advance as the reference voltage value. With the reference voltage value set, the reference voltage value setting unit 245 detects a plurality of trigger points at which the voltage value acquired by the voltage value acquisition unit 30 crosses the reference voltage value. Next, for each trigger point, the reference voltage value setting unit 245 detects a zero-crossing point that first reaches 0 volts after crossing the reference voltage value. When a plurality of first ultrasonic signals and a plurality of second ultrasonic signals are acquired by the first signal acquisition unit 10 and the second signal acquisition unit 20, the reference voltage value setting unit 245 detects a zero-crossing point for each of these plurality of ultrasonic signals.

[0059] Next, the reference voltage value setting unit 245 calculates the ratio of the ultrasonic signals among the plurality of ultrasonic signals acquired by the first signal acquisition unit 10 and the second signal acquisition unit 20, in which the leading zero-crossing point, which is the first zero-crossing point in each ultrasonic signal, is the zero-crossing point that first reaches 0 voltage after the peak of the second wave. Then, when the calculated ratio is smaller than a preset ratio (for example, 50%), the reference voltage value setting unit 245 decreases the reference voltage value by a voltage value that is the preset adjustment width. Also, when the calculated ratio is larger than the preset ratio, the reference voltage value setting unit 245 increases the reference voltage value by a voltage value that is the preset adjustment width. In this way, the reference voltage value setting unit 245 can set the reference voltage value based on the voltage value acquired by the voltage value acquisition unit 30. Note that the initially set reference voltage value is not limited to the peak voltage value of the second wave, and may be the peak voltage value of another wave whose peak voltage value is between the peak voltage value of the first wave and the maximum voltage value, or may be a voltage value other than the peak voltage value.

[0060] Note that the reference voltage value setting unit 245 may be configured to set the reference voltage value by a method other than the above. For example, when the voltage value indicated by the information acquired by the setting information acquisition unit 42 is between the upper limit voltage value and the lower limit voltage value of the reference voltage value set by the upper and lower limit setting unit 244, the reference voltage value setting unit 245 may be configured to set the voltage value indicated by the information acquired by the setting information acquisition unit 42 as the reference voltage value. Also, for example, when the voltage value indicated by the information acquired by the setting information acquisition unit 42 is larger than the upper limit voltage value of the reference voltage value set by the upper and lower limit setting unit 244, the reference voltage value setting unit 245 may be configured to set the upper limit voltage value of the reference voltage value set by the upper and lower limit setting unit 244 as the reference voltage value.

[0061] Further, for example, when the voltage value indicated by the information acquired by the setting information acquisition unit 42 is a voltage value smaller than the lower limit voltage value of the reference voltage value set by the upper and lower limit setting unit 244, the reference voltage value setting unit 245 may be configured to set the lower limit voltage value of the reference voltage value set by the upper and lower limit setting unit 244 as the reference voltage value. Note that when the voltage value indicated by the information acquired by the setting information acquisition unit 42 is not a voltage value between the upper limit voltage value and the lower limit voltage value of the reference voltage value set by the upper and lower limit setting unit 244, the reference voltage value setting unit may be set to output an error signal indicating that the reference voltage value cannot be set.

[0062] Next, with reference to FIGS. 8 and 9, details of the processing performed by the flow rate calculation device 200 according to the second embodiment will be described. FIG. 8 is a flowchart showing the reference voltage value setting process performed by the flow rate calculation device 200 according to the second embodiment. The reference voltage value setting process shown in FIG. 8 is a process for the flow rate calculation device 200 to set a first reference voltage value related to the first ultrasonic signal. For example, the reference voltage value setting process is a process performed at a predetermined timing when the flow rate calculation device 200 is shipped from the manufacturing factory that manufactures the flow rate calculation device 200. Further, for example, the reference voltage value setting process is a process performed when the user uses the flow rate calculation device 200. Note that since the process for the flow rate calculation device 200 to set the first reference voltage value related to the first ultrasonic signal is the same as the process for the flow rate calculation device 200 to set the second reference voltage value related to the second ultrasonic signal, hereinafter, the process for the flow rate calculation device 200 to set the first reference voltage value related to the first ultrasonic signal will be described, and the description of the process for the flow rate calculation device 200 to set the second reference voltage value related to the second ultrasonic signal will be omitted. Further, since a part of the reference voltage value setting process performed by the flow rate calculation device 200 according to the second embodiment is the same as the reference voltage value setting process performed by the flow rate calculation device 100 according to the first embodiment, the same processes as the reference voltage value setting process according to the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

[0063] As shown in FIG. 8, when the process of step ST2 is performed, next, the flow rate calculation device 200 calculates the upper voltage value and the lower voltage value of the first reference voltage value (step ST4). In this process, the flow rate calculation device 200 calculates, based on the first voltage value, the second voltage value, the first fluctuation information, and the second fluctuation information of the first ultrasonic signal, two specific voltage values between the first voltage value and the second voltage value of the first ultrasonic signal as the upper voltage value and the lower voltage value of the first reference voltage value by the upper and lower limit setting unit 244.

[0064] FIG. 9 is a graph showing the first ultrasonic signal acquired by the first signal acquisition unit according to the second embodiment. For example, as shown in FIG. 9, in the process of step ST4, the flow rate calculation device 200 calculates the upper voltage value Va and the lower voltage value Vb of the first reference voltage value V0 so as to be values between the peak voltage value V1 of the first wave P1, which is the first voltage value of the first ultrasonic signal, and the peak voltage value V3 of the third wave P3, which is the second voltage value of the first ultrasonic signal. Specifically, in the process of step ST4, the flow rate calculation device 200 calculates the lower voltage value Vb of the first reference voltage value V0 so as to be a value between the peak voltage value V1 of the first wave P1 and the peak voltage value V2 of the second wave P2 of the first ultrasonic signal, and calculates the upper voltage value Va of the first reference voltage value V0 so as to be a value between the peak voltage value V2 of the second wave P2 and the peak voltage value V3 of the third wave P3 of the first ultrasonic signal. For example, as shown in the following mathematical formulas (6) and (7), the flow rate calculation device 200 calculates the lower voltage value Vb so as to be a value between the voltage value obtained by adding the first fluctuation amount ΔV1 to the peak voltage value V1 of the first wave and the voltage value obtained by subtracting the third fluctuation amount ΔV2b from the peak voltage value V2 of the second wave, and calculates the upper voltage value Va so as to be a value between the voltage value obtained by adding the fourth fluctuation amount ΔV2a to the peak voltage value V2 of the second wave and the voltage value obtained by subtracting the second fluctuation amount ΔV3 from the peak voltage value V3 of the third wave. V1 + ΔV1 ≤ Vb ≤ V2 - ΔV2b ···(6) V2 + ΔV2a ≤ Va ≤ V3 - ΔV3 ···(7)

[0065] Note that for each of the various factors that cause the first voltage value, the second voltage value, and the third voltage value to fluctuate, the upper and lower limit setting unit 244 weights them and then calculates the upper limit voltage value Va and the lower limit voltage value Vb of the reference voltage value. Regarding the weighting for each of the various factors when calculating the upper limit voltage value Va and the lower limit voltage value Vb, since it is the same as the weighting for the various factors by the reference voltage value setting unit 145 according to Embodiment 1, the description thereof is omitted.

[0066] When the process of step ST4 is performed, next, the flow rate calculation device 200 acquires setting information of the reference voltage value (step ST9). In this process, the flow rate calculation device 200 acquires, by the setting information acquisition unit 42, the setting information that is information regarding the first reference voltage value and the second reference voltage value set by the reference voltage value setting unit 245.

[0067] When the process of step ST9 is performed, next, the flow rate calculation device 200 calculates the reference voltage value (step ST10). In this process, the flow rate calculation device 200 calculates the reference voltage value based on the information acquired by the setting information acquisition unit 42 and the upper limit voltage value and the lower limit voltage value of the reference voltage value set by the upper and lower limit setting unit 244 so that the reference voltage value is between the upper limit voltage value and the lower limit voltage value. When the process of step ST10 is performed, next, the flow rate calculation device 200 stores the calculated reference voltage value in the storage unit (step ST11).

[0068] As described above, the flow rate calculation device 100 according to Embodiment 2 includes a voltage value acquisition unit 30 that acquires the first voltage value of the first peak of the pulse signal including the first peak and the second peak, and the second voltage value of the second peak that is greater than the first voltage value, a variation information acquisition unit 41 that acquires first variation information indicating a first variation amount that is a positive variation amount of the first voltage value and second variation information indicating a second variation amount that is a negative variation amount of the second voltage value, and an upper and lower limit setting unit 244 that sets a specific voltage value between the first voltage value and the second voltage value as the upper limit voltage value and the lower limit voltage value of the reference voltage value based on the first voltage value, the second voltage value, the first variation information, and the second variation information.

[0069] Configured in this way, the flow rate calculation device 100 according to Embodiment 2 sets a specific voltage value between the first voltage value and the second voltage value as the upper limit voltage value and the lower limit voltage value of the reference voltage value based on the first variation information indicating the variation amount of the first voltage value and the second variation information indicating the variation amount of the second voltage value. Therefore, even when the first voltage value and the second voltage value vary, it is possible to suppress the change in the vertical relationship between the first voltage value, the second voltage value, and the reference voltage value more than before.

[0070] In Embodiment 2, the flow rate calculation device 100 is configured to set a specific voltage value between the peak voltage value V1 of the first wave P1 and the peak voltage value V2 of the second wave P2 as the lower limit voltage value of the reference voltage value, and set a specific voltage value between the peak voltage value V2 of the second wave P2 and the peak voltage value V3 of the third wave P3 as the upper limit voltage value of the reference voltage value. However, the present invention is not limited to this. The flow rate calculation device acquires the first voltage value of the first peak of the pulse signal including the first peak and the second peak, and the second voltage value of the second peak larger than the first voltage value, and acquires the first variation information indicating the first variation amount that is the positive variation amount of the first voltage value, and the second variation information indicating the second variation amount that is the negative variation amount of the second voltage value. As long as it is configured to set a specific voltage value between the first voltage value and the second voltage value as the upper limit voltage value and the lower limit voltage value of the reference voltage value based on the first voltage value, the second voltage value, the first variation information, and the second variation information. For example, the flow rate calculation device may be configured to set a specific voltage value between the peak voltage value V1 of the first wave P1 and the peak voltage value V2 of the second wave P2 as the lower limit voltage value of the reference voltage value, and set a specific voltage value between the peak voltage value V3 of the third wave P3 and the maximum voltage value Vmax as the upper limit voltage value of the reference voltage value, or may be configured to set a specific voltage value between the peak voltage value V2 of the second wave P2 and the peak voltage value V3 of the third wave P3 as the lower limit voltage value of the reference voltage value, and set a specific voltage value between the peak voltage value V4 of the fourth wave P4 and the fifth wave P5 as the upper limit voltage value of the reference voltage value.

[0071] FIG. 10 is a graph showing a first ultrasonic signal acquired by a first signal acquisition unit, an upper voltage value and a lower voltage value set by an upper and lower limit setting unit, and a reference voltage value set by a reference voltage value setting unit, according to a modification of Embodiment 2. The flow rate calculation device according to the modification of Embodiment 2 is configured to set a specific voltage value between the peak voltage value V2 of the second wave P2 and the peak voltage value V3 of the third wave P3 as the upper and lower voltage values of the reference voltage value. Thus, various positions can be considered as the positions where the upper and lower voltage values of the reference voltage value are set.

[0072] Embodiment 3. Next, with reference to FIGS. 11 and 12, the flow rate calculation device 300 according to Embodiment 3 will be described. The flow rate calculation device 300 according to Embodiment 3 has a different configuration of the reference voltage value control unit from the flow rate calculation device 100 according to Embodiment 1, but the other configurations are the same. For the same configurations as those in Embodiment 1, the same names and reference numerals as those in Embodiment 1 will be given and the description will be omitted.

[0073] FIG. 11 is a block diagram showing a schematic configuration of a flow rate measurement system according to Embodiment 3. As shown in FIG. 11, the flow rate calculation device 300 according to Embodiment 3 includes a first signal acquisition unit 10, a second signal acquisition unit 20, a voltage value acquisition unit 30, a reference voltage value control unit 340, a propagation time calculation unit 50, a time difference calculation unit 60, a flow rate calculation unit 70, and a storage unit 80. The reference voltage value control unit 340 includes a variation information acquisition unit 41, a measurement information acquisition unit 43, and a reference voltage value setting unit 345.

[0074] The measurement information acquisition unit 43 acquires measurement information regarding various conditions when measuring the flow rate of the fluid flowing inside the measurement tube 1. For example, as various conditions, the measurement information acquisition unit 43 acquires, based on an input signal from the input device 90, the temperature of the flow rate measurement system, the temperature of the fluid flowing inside the measurement tube 1, the flow velocity of the fluid flowing inside the measurement tube 1, the pressure of the fluid flowing inside the measurement tube 1, the type of the fluid to be measured, and measurement information indicating any one or a plurality of the elapsed time and the number of uses since the transducers 2 and 3 were produced.

[0075] Based on the first voltage value, the second voltage value, the first fluctuation information, the second fluctuation information, and the measurement information acquired by the measurement information acquisition unit 43 of the first ultrasonic signal, the reference voltage value setting unit 345 sets a specific voltage value between the first voltage value and the second voltage value of the first ultrasonic signal as the first reference voltage value which is the reference voltage value. Further, based on the first voltage value, the second voltage value, the first fluctuation information, the second fluctuation information, and the measurement information acquired by the measurement information acquisition unit 43 of the second ultrasonic signal, the reference voltage value setting unit 345 sets a specific voltage value between the first voltage value and the second voltage value of the second ultrasonic signal as the second reference voltage value which is the reference voltage value.

[0076] For example, when the measurement information acquired by the measurement information acquisition unit 43 is the measurement information indicating the temperature of the flow measurement system, the reference voltage value setting unit 345 calculates the first variation amount and the second variation amount based on the acquired temperature of the flow measurement system, and sets the reference voltage value based on the calculation result. By varying the first variation amount and the second variation amount according to the measurement information in this way, it becomes possible to more accurately suppress the change in the vertical relationship between a plurality of voltage values.

[0077] Next, with reference to FIG. 11, the details of the processing performed by the flow rate calculation device 300 according to Embodiment 3 will be described. FIG. 11 is a flowchart showing the reference voltage value setting process performed by the flow rate calculation device 300 according to Embodiment 3. The reference voltage value setting process shown in FIG. 11 is a process for the flow rate calculation device 300 to set a first reference voltage value related to the first ultrasonic signal. For example, the reference voltage value setting process is a process performed when the user uses the flow rate calculation device 100. Note that since the process for the flow rate calculation device 300 to set the first reference voltage value related to the first ultrasonic signal and the process for the flow rate calculation device 300 to set the second reference voltage value related to the second ultrasonic signal are the same, hereinafter, the process for the flow rate calculation device 300 to set the first reference voltage value related to the first ultrasonic signal will be described, and the description of the process for the flow rate calculation device 300 to set the second reference voltage value related to the second ultrasonic signal will be omitted. Further, since a part of the reference voltage value setting process performed by the flow rate calculation device 300 according to Embodiment 3 is the same as the reference voltage value setting process performed by the flow rate calculation device 100 according to Embodiment 1, the same processes as the reference voltage value setting process according to Embodiment 1 will be denoted by the same reference numerals and the description thereof will be omitted.

[0078] As shown in FIG. 11, when the process of step ST2 is performed, next, the flow rate calculation device 200 acquires measurement information (step ST5). In this process, the flow rate calculation device 200 acquires, by the measurement information acquisition unit 43, measurement information regarding various conditions when measuring the flow rate of the fluid flowing inside the measurement tube 1.

[0079] When the process of step ST5 is performed, next, the flow rate calculation device 300 calculates a reference voltage value according to the measurement information (step ST7). In this process, the flow rate calculation device 300 calculates the first reference voltage value in a state where the factors causing the first voltage value and the second voltage value to vary are narrowed down based on the measurement information acquired by the measurement information acquisition unit 43. When the process of step ST7 is performed, next, the flow rate calculation device 300 stores the reference voltage value in the storage unit 80 (step ST11).

[0080] Embodiment 4. Next, with reference to FIGS. 13 and 14, the flow rate calculation device 400 according to Embodiment 4 will be described. The flow rate calculation device 400 according to Embodiment 4 has a different configuration of the reference voltage value control unit from the flow rate calculation devices according to Embodiments 1 to 3, but the other configurations are the same. For the same configurations as those in Embodiments 1 to 3, the same names and reference numerals as those in Embodiments 1 to 3 will be given and the description thereof will be omitted.

[0081] FIG. 13 is a block diagram showing a schematic configuration of a flow rate measurement system according to Embodiment 4. As shown in FIG. 13, the flow rate calculation device 400 according to Embodiment 4 includes a first signal acquisition unit 10, a second signal acquisition unit 20, a voltage value acquisition unit 30, a reference voltage value control unit 440, a propagation time calculation unit 50, a time difference calculation unit 60, a flow rate calculation unit 70, and a storage unit 80. The reference voltage value control unit 440 includes a variation information acquisition unit 41, a setting information acquisition unit 42, a measurement information acquisition unit 43, an upper and lower limit setting unit 444, and a reference voltage value setting unit 345.

[0082] The upper and lower limit setting unit 444 sets a specific voltage value between the first voltage value and the second voltage value of the first ultrasonic signal as the upper limit voltage value and the lower limit voltage value of the first reference voltage value based on the first voltage value of the first ultrasonic signal, the second voltage value, the first variation information, the second variation information, and the measurement information acquired by the measurement information acquisition unit 43. Further, the reference voltage value setting unit 345 sets a specific voltage value between the first voltage value and the second voltage value of the second ultrasonic signal as the upper limit voltage value and the lower limit voltage value of the second reference voltage value based on the first voltage value of the second ultrasonic signal, the second voltage value, the first variation information, the second variation information, and the measurement information acquired by the measurement information acquisition unit 43.

[0083] For example, when the measurement information acquired by the measurement information acquisition unit 43 is measurement information indicating the temperature of the flow rate measurement system, the reference voltage value setting unit 345 calculates the first variation amount and the second variation amount based on the acquired temperature of the flow rate measurement system, and sets the upper limit voltage value and the lower limit voltage value of the reference voltage value based on the calculation result. By varying the first variation amount and the second variation amount according to the measurement information in this way, it becomes possible to more accurately suppress the change in the vertical relationship between a plurality of voltage values.

[0084] The reference voltage value setting unit 445 sets a reference voltage value based on the information acquired by the setting information acquisition unit 42 and the upper and lower limit voltage values of the reference voltage value set by the upper and lower limit setting unit 444. Since the process of the reference voltage value setting unit 445 setting the reference voltage value is the same as the process of the reference voltage value setting unit 245 setting the reference voltage value, the description thereof is omitted.

[0085] Next, with reference to FIG. 14, details of the process performed by the flow rate calculation device 400 according to Embodiment 4 will be described. FIG. 14 is a flowchart showing the reference voltage value setting process performed by the flow rate calculation device 400 according to Embodiment 3. The reference voltage value setting process shown in FIG. 14 is a process for the flow rate calculation device 400 to set a first reference voltage value related to the first ultrasonic signal. For example, the reference voltage value setting process is a process performed when the user uses the flow rate calculation device 100. Since the process of the flow rate calculation device 400 setting the first reference voltage value related to the first ultrasonic signal is the same as the process of the flow rate calculation device 400 setting the second reference voltage value related to the second ultrasonic signal, hereinafter, the process of the flow rate calculation device 400 setting the first reference voltage value related to the first ultrasonic signal will be described, and the process of the flow rate calculation device 400 setting the second reference voltage value related to the second ultrasonic signal will be omitted. Further, since a part of the reference voltage value setting process performed by the flow rate calculation device 400 according to Embodiment 4 is the same as the reference voltage value setting process performed by the flow rate calculation devices according to Embodiments 1 to 3, the same processes as the reference voltage value setting processes according to Embodiments 1 to 3 will be denoted by the same reference numerals and the description thereof will be omitted.

[0086] As shown in FIG. 14, when the process of step ST2 is performed, next, the flow rate calculation device 400 acquires measurement information (step ST6). In this process, the flow rate calculation device 400 acquires, by the measurement information acquisition unit 43, measurement information regarding various conditions when measuring the flow rate of the fluid flowing inside the measurement tube 1.

[0087] When the process of step ST6 is performed, next, the flow rate calculation device 400 calculates the upper voltage value and the lower voltage value of the reference voltage value according to the measurement information (step ST8). In this process, based on the measurement information acquired by the measurement information acquisition unit 43, the flow rate calculation device 400 calculates the upper voltage value and the lower voltage value of the first reference voltage value in a state where the factors causing the first voltage value and the second voltage value to fluctuate are narrowed down. By calculating the upper voltage value and the lower voltage value of the first reference voltage value based on the measurement information in this way, it becomes possible to increase the difference between the upper voltage value and the lower voltage value, and it becomes possible to improve the degree of freedom in setting when setting the reference voltage value as a voltage value between the upper voltage value and the lower voltage value. When the process of step ST8 is performed, next, the flow rate calculation device 300 acquires setting information (step ST9).

[0088] Note that in the present disclosure, free combinations of each embodiment, or modifications of any component of each embodiment, or omission of any component in each embodiment are possible.

Description of Reference Numerals

[0089] 1: Measurement tube 2, 3: Transducer (signal generation unit) 10: First signal acquisition unit 20: Second signal acquisition unit 30: Voltage value acquisition unit 41: Fluctuation information acquisition unit 42: Setting information acquisition unit 43: Measurement information acquisition unit 50: Propagation time calculation unit 60: Time difference calculation unit 70: Flow rate calculation unit 80: Storage unit 90: Input device 100, 200, 300, 400: Flow rate calculation device (information processing device, ultrasonic flow meter) 140, 240, 340, 440: Reference voltage value control unit 145, 245, 345, 445: Reference voltage value setting unit (specific voltage value setting unit) 244, 444: Upper and lower limit setting unit (specific voltage value setting unit) P1: The first wave P2: The second wave P3: The third wave

Claims

1. a voltage value acquisition unit that acquires a first voltage value of the first peak of a pulse signal including a first peak and a second peak, and a second voltage value of the second peak that is greater than the first voltage value; a variation information acquisition unit that acquires first variation information regarding a first variation amount that is a positive variation amount of the first voltage value, and second variation information regarding a second variation amount that is a negative variation amount of the second voltage value; a specific voltage value setting unit that sets a specific voltage value between the first voltage value and the second voltage value as a specific voltage value based on the first voltage value, the second voltage value, the first variation information, and the second variation information; An information processing apparatus characterized by the above.

2. The specific voltage value setting unit sets, as the specific voltage value, a specific voltage value between a voltage value obtained by adding the first variation amount to the first voltage value and a voltage value obtained by subtracting the second variation amount from the second voltage value. The information processing apparatus according to claim 1, characterized by the above.

3. The first variation amount and the second variation amount include variation amounts of the first voltage value and the second voltage value due to a difference in temperature. The information processing apparatus according to claim 1, characterized by the above.

4. The first variation amount and the second variation amount include variation amounts of the first voltage value and the second voltage value due to a difference in the flow velocity of the medium through which the pulse signal propagates. The information processing apparatus according to claim 1, characterized by the above.

5. The first variation amount and the second variation amount include variation amounts of the first voltage value and the second voltage value due to a difference in the pressure of the medium through which the pulse signal propagates. The information processing apparatus according to claim 1, characterized by the above.

6. The first variation amount and the second variation amount include variation amounts of the first voltage value and the second voltage value due to a difference in the physical properties of the medium through which the pulse signal propagates. The information processing apparatus according to claim 1, characterized by the above.

7. The first variation amount and the second variation amount include variation amounts of the first voltage value and the second voltage value due to secular changes in the signal generation unit that generates the pulse signal. The information processing apparatus according to claim 1, characterized by the above.

8. The first variation amount and the second variation amount include variation amounts of the first voltage value and the second voltage value due to accidental errors. The information processing apparatus according to claim 1, characterized by the above.

9. The information processing apparatus according to any one of claims 1 to 8, and A first signal acquisition unit that acquires a first ultrasonic signal, which is a pulse signal based on a first ultrasonic wave output from one ultrasonic vibrator and propagated to the other ultrasonic vibrator through a fluid to be measured as a medium; A second signal acquisition unit that acquires a second ultrasonic signal, which is a pulse signal based on a second ultrasonic wave output from the other ultrasonic vibrator and propagated to the one ultrasonic vibrator through the fluid as a medium; A propagation time calculation unit that calculates the propagation time of the first ultrasonic wave and the second ultrasonic wave; A time difference calculation unit that calculates the difference between the propagation time of the first ultrasonic wave and the propagation time of the second ultrasonic wave acquired by the propagation time calculation unit; A flow rate calculation unit that calculates the flow rate of the fluid based on the calculation result by the time difference calculation unit, and is provided with: The propagation time calculation unit calculates the propagation time of the first ultrasonic wave based on the zero-crossing time of the voltage value of the first ultrasonic signal after reaching the specific voltage value set by the specific voltage value setting unit. An ultrasonic flow meter characterized by the above.

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