Transducer and fluid type discrimination device

Abstract

To provide a heat flow meter by using a transducer capable of transmitting ultrasonic waves of multiple frequencies with a simple structure. [Solution] A pair of transducers 22 and 23 capable of transmitting and receiving multiple frequencies and a temperature sensor 26 are used. The measurement control unit 27 switches between these to measure the received ultrasonic intensity, propagation time, and temperature. The signals obtained from these are processed by the signal processing unit 29 to determine the gas type and measure the flow rate. The heat flow rate is then measured using this data along with a density table and a heat output table previously stored in the storage unit 28.

Description

Technical Field

[0001] The present invention relates to a calorimetric flowmeter that measures the calorimetric flow rate of a fluid to be measured using a transmitter / receiver configured to transmit ultrasonic waves of a plurality of frequencies from a single member by using a vibration propagation member that operates in conjunction with a vibrating body.

Background Art

[0002] Conventionally, a device that transmits a plurality of frequencies and measures a gas value (calorific value, etc.) is known (see, for example, Patent Document 1).

[0003] FIG. 13 is a schematic configuration diagram of a conventional gas value measuring device using a transducer. In FIG. 13, the gas value measuring device 101 includes a gas inlet 102 and an outlet 103. Transducers 105 and 106 are arranged so that measurement is performed by the measurement unit 104. These transducers 105 and 106 transmit and receive signals at the first frequency f1. Further, an ultrasonic transducer 108 and a reflector 109 arranged to transmit and receive ultrasonic waves from the ultrasonic transducer 108 are arranged opposite to each other so that measurement is performed by the measurement unit 107. This ultrasonic transducer 108 transmits and receives signals at the second frequency f2. In this way, the measurement systems 110 and 111 are configured by the transducers 105 and 106 and the ultrasonic transducer 108 and the reflector 109, respectively.

[0004] In this configuration, the gas to be measured flows in from the inlet 102, passes through the measurement unit 104, and flows out from the outlet 103. During this time, the gas also fills the measurement unit 107. In the measurement unit 104, the gas attenuation is measured by ultrasonic waves of frequency f1 transmitted and received between transducers 105 and 106. In addition, the gas attenuation is measured by ultrasonic waves of frequency f2 transmitted and received between ultrasonic transducer 108 and reflector 109. Using these attenuation values ​​at frequencies f1 and f2, the gas value of the measured gas is derived based on the relationship between the frequency and attenuation and the gas value (calorific value, etc.) that has been stored in advance. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 11-511260 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the conventional gas value measuring device described above requires three transducers and two measurement systems composed of them to use two different frequencies for gas type identification. This results in a large number of parts, a complex configuration, and a larger size, leading to increased costs. Furthermore, because attenuation is measured at different locations, the attenuation value differs depending on the temperature at each location, which limits the accuracy of the identification.

[0007] The present invention addresses the above-mentioned problems and aims to achieve heat flow measurement by performing gas type identification and flow rate measurement with a single system, using a vibration propagation member that operates by being bonded to one surface of a vibrating body, and which is formed by a top plate, a bottom plate, side walls, and partition walls positioned approximately perpendicular to the top plate and bottom plate, and which uses vibrations generated by multiple membrane structures formed by the top plate and the partition walls, and which generates different resonant frequencies by setting the distance between the partition walls to different values, and by using a transducer that can transmit and receive multiple frequencies with a single member, an ultrasonic transducer is attached to the vibration propagation member. [Means for solving the problem]

[0008] To solve the aforementioned conventional problems, the heat flow meter of the present invention comprises a flow path through which a fluid to be measured flows, a pair of transducers arranged upstream and downstream of the flow path, a temperature sensor for measuring the temperature of the fluid to be measured flowing through the flow path, a measurement control unit for controlling the transmission and reception operations of the pair of transducers and the temperature measurement operation of the temperature sensor, a signal processing unit for processing the received signals of the pair of transducers and the temperature signal obtained by the temperature sensor, and a storage unit for storing a first table defining the relationship between the type, temperature and density of the fluid to be measured and a second table defining the relationship between the type and heat generation of the fluid to be measured, wherein the transducers are configured to transmit and receive multiple resonant frequencies, and the signal The processing unit includes a fluid type determination unit that determines the type of fluid to be measured based on the signal characteristics of received signals at multiple resonant frequencies, a flow rate calculation unit that measures the flow rate of the fluid to be measured using one of the multiple resonant frequencies, and a heat flow rate calculation unit that determines the heat flow rate of the fluid to be measured based on the type of fluid to be measured identified by the fluid type determination unit, the flow rate calculated by the flow rate calculation unit, the temperature measured by the temperature sensor, and the first and second tables. This configuration enables transmission and reception of multiple frequencies using only one vibration propagation member, and by using a transducer with this configuration, a highly accurate heat flow meter can be constructed in a single system. [Effects of the Invention]

[0009] The heat flow meter of the present invention is configured to transmit and receive multiple frequencies using only one vibration propagation member. By using a transducer with this configuration, measurement can be performed in a single system, and since flow rate measurement and gas type identification can be performed at the same location, heat flow measurement with high identification accuracy can be achieved. [Brief explanation of the drawing]

[0010] [Figure 1] Exploded perspective view of the vibration propagation member in Embodiment 1 of the present invention [Figure 2] Cross-sectional view of the vibration propagation member in Embodiment 1 of the present invention [Figure 3] This figure shows a method for forming a vibration propagation member in Embodiment 1 of the present invention. [Figure 4] Cross-sectional view of the transducer in Embodiment 1 of the present invention [Figure 5] Characteristic graph of the transducer in Embodiment 1 of the present invention [Figure 6] Schematic diagram of the heat flow meter in Embodiment 1 of the present invention [Figure 7] Configuration diagram of the signal processing unit for gas type discrimination in Embodiment 1 of the present invention. [Figure 8] Configuration diagram of the flow rate measurement signal processing unit in Embodiment 1 of the present invention [Figure 9] Gas frequency characteristic diagram in Embodiment 1 of the present invention [Figure 10] Figure showing a table for determining density from gas species and temperature in Embodiment 1 of the present invention. [Figure 11] Figure showing a table for determining the calorific value from the gas type in Embodiment 1 of the present invention. [Figure 12] Flowchart for determining heat flow rate in Embodiment 1 of the present invention [Figure 13] Schematic diagram of a conventional gas value measurement device using a transducer. [Modes for carrying out the invention]

[0011] The first invention includes a flow path through which a fluid to be measured flows, a pair of transceivers arranged upstream and downstream of the flow path, a temperature sensor for measuring the temperature of the fluid to be measured flowing through the flow path, a measurement control unit for controlling the transmission and reception operations of the pair of transceivers and the temperature measurement operation by the temperature sensor, a signal processing unit for processing the received signals of the pair of transceivers and the temperature signal obtained by the temperature sensor, and a storage unit for storing a first table defining the relationship between the type, temperature, and density of the fluid to be measured and a second table defining the relationship between the type and calorific value of the fluid to be measured. The transceiver is configured to perform transmission and reception at a plurality of resonance frequencies. The signal processing unit includes a fluid type discrimination unit for discriminating the type of the fluid to be measured based on the signal characteristics of the received signals at the plurality of resonance frequencies, a flow rate calculation unit for measuring the flow rate of the fluid to be measured using one of the plurality of resonance frequencies, and a calorific value flow rate calculation unit for obtaining the calorific value flow rate of the fluid to be measured based on the type of the fluid to be measured specified by the fluid type discrimination unit, the flow rate calculated by the flow rate calculation unit, the temperature measured by the temperature sensor, and the first and second tables. By having such a configuration, it is possible to perform transmission and reception at a plurality of frequencies using only one vibration propagation member, and by using a transceiver using this, highly accurate calorific value flow measurement can be performed with a single system.

[0012] Hereinafter, embodiments will be described in detail with reference to the drawings. However, a more detailed description than necessary may be omitted. For example, a detailed description of well-known matters or a redundant description of substantially the same configuration may be omitted. This is to avoid making the following description overly redundant and to facilitate the understanding of those skilled in the art.

[0013] Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0014] (Embodiment 1) [1-1. Configuration] (1) Configuration of vibration propagation member The configuration of the vibration propagation member of the transmitter / receiver used in this embodiment will be described with reference to FIGS. 1 to 3.

[0015] FIG. 1 is an exploded perspective view of the vibration propagation member. As shown in FIG. 1, the vibration propagation member 1 is composed of a plurality of partition walls 6, 7, 8, 9 arranged substantially perpendicular to the top plate 2 and the bottom plate 3 in a space surrounded by the top plate 2, the bottom plate 3, and the side walls 4, 5. In FIG. 1, for the sake of easy understanding of the internal structure of the vibration propagation member, the bottom plate 3 and the side wall 5 are shown as being removed. With such a configuration, the top plate 2 is divided into a film surface 10 partitioned by the partition walls 6, 7, a film surface 11 partitioned by the partition walls 7, 8, and a film surface 12 partitioned by the partition walls 8, 9.

[0016] FIG. 2 shows a cross-section of the vibration propagation member 1 in FIG. 1. FIG. 2(a) is a horizontal cross-section AA' of FIG. 1, and FIG. 2(b) is a vertical cross-section BB' of FIG. 1. As shown in FIG. 2(a), the widths (W) of each of the film surfaces 10, 11, 12 are equal, but the lengths (Ma, Mb, Mc) are configured to have the following relationship. This film surface length can also be said to be the interval between the partition walls.

[0017] Ma < Mb < Mc On the other hand, as shown in FIG. 2(b), the heights H of the partition walls 6, 7, 8, 9 are equal, and the thicknesses La of each partition wall 6, the thickness Lb of the partition wall 7, the thickness Lc of the partition wall 8, and the thickness Ld of the partition wall 9 are formed to be substantially equal.

[0018] As a result, the vibration propagation member 1 has vibration portions of three film structures (each indicated by a dashed line): a film structure 13 composed of the partition walls 6, 7 and the film surface 10, a film structure 14 composed of the partition walls 7, 8 and the film surface 11, and a film structure 15 composed of the partition walls 8, 9 and the film surface 12.

[0019] In Figure 1, the vibration propagation member 1 is configured as a top plate 2, bottom plate 3, side walls 4, 5, and partition walls 6, 7, 8, 9, which are separate components. However, as shown in Figure 3, the vibration propagation member 51 can also be formed by stacking multiple intermediate plates 54, which are made by etching thin metal (e.g., SUS) sheets into a predetermined shape, to form partition walls and side walls, and then further stacking the top plate 52 and bottom plate 53 above and below them. The operation of this vibration propagation member will be explained in the following explanation of the operation of the transducer configuration.

[0020] (2) Transmitter configuration The configuration of the transducer used in this embodiment will be explained with reference to Figures 4 and 5.

[0021] Figure 4 shows a cross-sectional view of the transducer 16. The transducer 16 has a vibrating body 17 attached to the bottom plate 3 of the vibration propagation member 1, as described in (1) Configuration of the vibration propagation member above. The vibrating body 17 is, for example, a piezoelectric body. The vibration propagation member 1 is the same as in Embodiment 1, so the same numbers are used for the same parts as in Figures 1 and 2.

[0022] Next, the operation of the transducer 16 will be explained using Figure 4, but before that, the basic characteristics of the vibration propagation member 1 having such a configuration will be explained.

[0023] In Figure 4, the lengths of membrane surfaces 10, 11, and 12 are different, but Figure 5 shows the relationship between length and the resonant frequency of the membrane surface. In Figure 5, the horizontal axis represents the length of the membrane surface (=spacing between septa), and the vertical axis represents the resonant frequency of the membrane structure.

[0024] As shown in Figure 5, it can be seen that the resonance frequency decreases as the length of the film surface of the film structure increases. This means that film structures with a large film surface length resonate at low frequencies, and film structures with a small film surface length resonate at high frequencies. Therefore, by forming film structures with various film surface lengths, it is possible to generate resonances at multiple frequencies. Here, we will explain assuming that three different resonance frequencies (f1, f2, f3) are generated.

[0025] The operation of the vibration transmission member 1, based on its basic characteristics, will be explained with reference to Figure 4.

[0026] When the vibrating body 17 is excited by a drive signal containing the resonant frequency component of the vibrating membrane, and the generated vibration is supplied via the bottom plate 3, the vibration is transmitted to the top plate 2 via partitions 6, 7, 8, and 9, respectively. At this time, as mentioned earlier, the membrane surfaces 10, 11, and 12 have different lengths, so the membrane surfaces 10, 11, and 12 vibrate at different resonant frequencies. In other words, ultrasonic waves of different frequencies are emitted from the membrane surfaces 10, 11, and 12, with the resonant frequency of the membrane surface 10, which has a smaller membrane length, being higher, and the resonant frequency of the membrane surface 12, which has a larger membrane length, being lower.

[0027] The above describes the case where the transducer 16 is used for transmitting ultrasonic waves. However, even when it is used for receiving, the relationship between the membrane length and the resonant frequency remains the same, so this relationship should be taken into consideration. In other words, in Figure 4, when the ultrasonic waves reach the membrane surface, the resonant frequency values ​​of membrane surfaces 10, 11, and 12 correspond in this order from largest to smallest.

[0028] Therefore, when two transducers 16 are used facing each other, as shown in Figure 4, the ultrasonic waves transmitted from the transducer can be received by the receiver by arranging them so that those with equal membrane lengths face each other directly.

[0029] As explained above, this transducer allows the resonant frequency to be controlled by changing the diaphragm length, and as a result, it can transmit ultrasonic waves of multiple resonant frequencies from the top plate. In other words, with a simple configuration of one vibrating body and one vibration propagator, it is possible to transmit and receive ultrasonic waves of multiple resonant frequencies simultaneously.

[0030] (3) Configuration of a heat flow meter The configuration of the heat flow meter in this embodiment will be explained using Figures 6 to 11.

[0031] Figure 6 shows a cross-section of the heat flow meter 20 in Embodiment 1 of the present invention. The flow path 21 through which the fluid to be measured flows has a rectangular cross-section, and a pair of transducers 22 and 23 are arranged facing each other on its short side. The transducers 22 and 23 are the same as those described in (2) Transducer Configuration above. That is, the membrane length is the same as that formed in Figure 4. In Figure 6, arrow 24 indicates the direction of flow of the fluid to be measured. The pair of transducers 22 and 23 are arranged facing each other so as to cross the flow of the fluid to be measured. In this case, the transducers 22 and 23 are arranged so that the portions with equal membrane lengths face each other in the configuration of Figure 4. The direction of transmission and reception of these transducers 22 and 23 can be switched by a switching unit 25.

[0032] Furthermore, the temperature sensor 26 is positioned to measure the temperature of the fluid being measured. The measurement control unit 27 controls the measurement operations of the switching unit 25 and the temperature sensor 26. The storage unit 28 stores tables and other data used in the heat flow rate calculation, which will be described later. The signal processing unit 29 processes signals obtained from the transducers 22 and 23, as well as signals from the temperature sensor 26, and also performs calculations while referring to data stored in the storage unit 28. This signal processing unit 29 includes a fluid type discrimination processing unit 29a that identifies the type of gas, a flow rate measurement processing unit 29b that calculates the flow rate of the fluid being measured, and a heat flow rate calculation unit 29c that calculates the heat flow rate of the fluid being measured, which will be described later.

[0033] Figure 7 is a diagram showing the configuration of the fluid type discrimination processing unit 29a of the signal processing unit 29 in the heat flow meter of the present invention.

[0034] As shown in Figure 7, the fluid type discrimination processing unit 29a consists of an A / D conversion unit 30 for the input signal, filters A31, B32, and C33 corresponding to predetermined frequencies f1, f2, and f3 respectively, processing units A34, B35, and C36 for the signal that has passed through filters A31, B32, and C33, and a gas type discrimination unit 37 for the signal processed by processing units A34, B35, and C36.

[0035] When performing gas type discrimination, processing units A34, B35, and C36 each have the function of measuring the received intensity of the received waves that have passed through filters A31, B32, and C33, respectively. The gas type discrimination unit 37 has the function of discriminating the gas type of the fluid being measured based on these received intensities, using a method described later.

[0036] Figure 8 is a diagram showing the configuration of the flow rate measurement processing unit 29b of the signal processing unit 29 in the heat flow meter of the present invention.

[0037] As shown in Figure 8, the flow rate measurement processing unit 29b consists of a signal input unit 38, a filter D39 corresponding to one of the predetermined frequencies f1, f2, and f3, a signal processing unit D40 for the signal that has passed through filter D, and a flow rate calculation unit 41 that performs flow rate calculation using the signal processed by processing unit D40 in a manner that will be described later.

[0038] Figure 9 is an example of a simulated frequency characteristic diagram of a gas being measured. In Figure 9, the horizontal axis represents frequency f, and the vertical axis represents the received signal strength S at a predetermined distance when a predetermined signal is transmitted to the target gas. Gas Ga and gas Gb have different frequency characteristics (signal characteristics of the received signal). Gas Ga decreases monotonically with changes in frequencies f1, f2, and f3, but gas Gb has a minimum value. Therefore, by using this characteristic diagram, if the received signal strength at a specific frequency (e.g., f1, f2, f3) is known, it is possible to distinguish between gas Ga and gas Gb from the trend and the values.

[0039] Figure 10 shows Table 1 (the first table) for determining the density (ρ) of the fluid being measured, based on the gas type (G) and temperature (t). Figure 11 shows Table 2 (the second table) for determining the calorific value (C) per unit mass, based on the gas type (G). By using these, the heat flow rate can be determined by multiplying the flow rate (Q) by the density (ρ) and then by the calorific value (C). Tables 1 and 2 are stored in the memory unit 28.

[0040] [1-2. Operation] The operation of a heat flow meter, which measures heat flow rate based on the above configuration, will now be explained.

[0041] In explaining the operation of this heat flow measurement, we will first explain the preceding operations: gas type identification and flow measurement. Then, we will explain the heat flow measurement operation itself.

[0042] (a) Gas type discrimination operation The gas type discrimination operation will be explained using Figures 6, 7, and 9.

[0043] First, in Figure 6, the measurement control unit 27 controls the switching unit 25 and transmits a drive signal to the transducer 22, sending ultrasonic waves into the fluid to be measured. The ultrasonic waves sent into the fluid to be measured propagate toward the transducer 23 and are received by the transducer 23.

[0044] Since transducers 22 and 23 use the transducer configuration described in (2) above, when transmitting from transducer 22, ultrasonic waves of multiple frequencies are transmitted. Also, in transducer 23, ultrasonic waves of multiple frequencies are received on the corresponding membrane surface of transducer 22. The received signals are received via the switching unit 25 and sent to the signal processing unit 29.

[0045] Next, the processing details in the fluid type discrimination processing unit 29a of the signal processing unit 29 will be explained in Figure 7. The signal input to the signal processing unit 29 is converted into a digital signal by the A / D conversion unit 30. Then, it is filtered by filter A31 at frequency f1, filter B32 at frequency f2, and filter C33 at frequency f3, and the received signal strength at each frequency is obtained by processing units A34, B35, and C36, respectively.

[0046] These received intensity data are compared in the gas type discrimination unit 37 with the received intensity at frequencies f1, f2, and f3 shown in Figure 9, which are stored in advance, to determine the type of gas that is the measured fluid.

[0047] (b) Flow measurement operation Next, the flow rate measurement operation will be explained using Figures 6 and 8.

[0048] In Figure 6, the measurement control unit 27 controls the switching unit 25 and transmits a drive signal to the transducer 22, sending ultrasonic waves into the fluid to be measured. The ultrasonic waves sent into the fluid to be measured propagate toward the transducer 23 and are received by the transducer 23.

[0049] Since transducers 22 and 23 use the transducer configuration described in (2) above, when transmitting from transducer 22, ultrasonic waves of multiple frequencies are transmitted. Also, in transducer 23, ultrasonic waves of multiple frequencies are received on the corresponding membrane surface of transducer 22. The received signals are received via the switching unit 25 and sent to the signal processing unit 29.

[0050] Next, the processing details in the flow rate measurement processing unit 29b of the signal processing unit 29 will be explained in Figure 8. The received signal input to the signal processing unit 29 is filtered by a filter D39 set to either f1, f2, or f3 via the input unit 38, and the propagation time (t1) from transmission to reception is measured by the processing unit D40 using a well-known method.

[0051] Next, in Figure 6, the measurement control unit 27 controls the switching unit 25 to transmit and receive ultrasonic waves in the opposite direction to before. That is, it transmits a drive signal to the transducer 23 and sends ultrasonic waves into the fluid to be measured. The ultrasonic waves sent into the fluid to be measured then propagate toward the transducer 22 and are received by the transducer 22.

[0052] The same process as described above is then performed in the signal processing unit 29 in Figure 8, and the propagation time (t2) in the reverse direction from the initial propagation time is measured. Using these propagation times t1 and t2, the flow rate value is calculated in the flow rate calculation unit 41 using a well-known method.

[0053] (c) Operation of the heat flow meter Based on the gas type discrimination processing operation of the fluid type discrimination processing unit 29a and the flow rate measurement processing operation of the flow rate measurement processing unit 29b described above, the heat flow rate measurement operation of the heat flow rate calculation unit 29c of the signal processing unit 29 will be explained below using Figures 10, 11, and 12.

[0054] Figure 12 is a flowchart of the heat flow rate measurement operation of the heat flow rate calculation unit 29c. The processes shown in this flowchart are carried out by the measurement control unit 27 and the signal processing unit 29 shown in Figure 6.

[0055] In Figure 12, step S1 is a command to start measurement, step S2 is a command to set the initial value (0) of the number of conditional branches n, and step S3 is a command to increase n.

[0056] Step S4 is a determination command to determine whether n is 1 (temperature measurement). Step S5 is a temperature measurement command, and step S6 is a storage command to store the obtained temperature data in the storage unit 28.

[0057] Step S7 is a determination command to determine whether n is 2 (gas type discrimination). Step S8 is a command to measure the received signal strength of frequencies f1, f2, and f3. Step S9 is a discrimination command to determine the gas type from the obtained received signal strength. Step S10 is a storage command to store the determined gas type in the storage unit 28.

[0058] Step S11 is a command to determine whether n is 3 (flow rate measurement). Step S12 is a command to measure the propagation time at frequency fi (i=1, 2, or 3). Step S13 is a command to calculate the flow rate from the obtained propagation time. Step S14 is a storage command to store the obtained flow rate value in the storage unit 28.

[0059] Step S15 is a reference command to Table 1 (Figure 10) in the storage unit 28, Step S16 is a reference command to Table 2 (Figure 11), and Step S17 is a heat flow rate calculation command that uses the gas type and flow rate values ​​already stored in the storage unit 28 to calculate the heat flow rate based on the values ​​obtained from Table 1 and Table 2. Step S18 is an interval setting command that sets the time for executing this process at a predetermined cycle.

[0060] In this flowchart, 42, enclosed by a dashed line, represents the processing of the fluid type discrimination processing unit 29a, 43 represents the processing of the flow rate measurement processing unit 29b, and 44 represents the processing of the heat flow rate calculation unit.

[0061] Next, the operation sequence of the heat flow measurement operation will be explained based on the flowchart in Figure 12.

[0062] First, the measurement operation begins with a start command (step S1). Next, the instruction to set the initial value (0) of the number of conditional branches n (step S2) sets the number of conditional branches n to its initial value (0). Then, the instruction to increase n (step S3) increases the value of n by "1", setting n=1.

[0063] i) Temperature measurement operation In this state, a decision command (step S4) is executed to determine whether n is 1 (temperature measurement). Since the current state is n=1, the decision is to select Yes.

[0064] Next, the process proceeds to the temperature measurement command (step S5), where the temperature sensor 26 measures the temperature of the fluid to be measured. The obtained temperature data is then stored in the storage unit 28 by the storage command (step S6). After that, the process returns to the n increment command (step S3).

[0065] ii) Gas type discrimination operation Currently, the value of n is 1, so the instruction to increase n (step S3) increases the value of n by "1", setting n=2.

[0066] In this state, a decision command (step S4) is executed to determine whether n is 1 (temperature measurement). Since the current state is n=2, the decision selects No, and then a decision command (step S7) is executed to determine whether n is 2 (gas type discrimination). Since the current state is n=2, the decision selects Yes.

[0067] Next, the process proceeds to the received signal strength measurement command (step S8), where the received signal strength is measured at three frequencies using the method already described in (a) gas type discrimination operation above. Subsequently, the gas type is determined by gas type discrimination (step S9). The determined gas type is stored in the storage unit 28 by the storage command (step S10). After that, the process returns to the n increment command (step S3).

[0068] iii) Flow measurement operation Currently, the value of n is 2, so the instruction to increase n (step S3) increases the value of n by "1", setting n=3.

[0069] In this state, a decision command (step S4) is executed to determine whether n is 1 (temperature measurement). Since the current state is n=3, the decision selects No, and then a decision command (step S7) is executed to determine whether n is 2 (gas type discrimination). Since the current state is n=3, the decision selects No, and then a decision command (step S11) is executed to determine whether n is 3 (flow rate measurement). Since the current state is n=3, the decision selects Yes.

[0070] Next, a propagation time measurement command (step S12) is issued, and a propagation time measurement is performed at one of the three frequencies in the manner already described in (b) flow rate measurement operation above, after which a flow rate calculation command (step S13) is executed.

[0071] The obtained flow rate (Q) is stored in the storage unit 28 by the flow rate storage instruction (step S14). After that, the process returns to the increment n instruction (step S3).

[0072] iV) Calorie flow rate calculation Currently, the value of n is 3, so the instruction to increase n (step S3) increases the value of n by "1", setting n=4.

[0073] In this state, a decision command (step S4) is executed to determine whether n is 1 (temperature measurement). Since the current state is n=4, the decision selects the No side, and then a decision command (step S7) is executed to determine whether n is 2 (gas type discrimination). Since the current state is n=4, the decision selects the No side, and then a decision command (step S11) is executed to determine whether n is 3 (flow rate measurement). Since the current state is n=4, the decision selects the No side.

[0074] Next, a reference command to Table 1 (step S15) is issued, and Table 1 is referenced based on the temperature and gas type stored in the memory unit 28 to determine the density (ρ) of the fluid to be measured. Subsequently, a reference command to Table 2 (step S16) is issued, and the calorific value (C) can be determined based on the gas type stored in the memory unit 28.

[0075] Subsequently, the heat flow rate can be determined by multiplying the flow rate (Q) by the density (ρ) and then by the heat generation amount (C) using the heat flow rate calculation command (step S17).

[0076] Subsequently, after a predetermined interval command (step S18), the same operation is repeated, and the measurement of the heat flow rate of the fluid being measured continues.

[0077] [1-3. Effects] As described above, the heat flow meter of the present invention can measure heat flow with high accuracy in a simple configuration by using a transducer capable of transmitting and receiving multiple frequencies.

[0078] Although three frequencies were described in this embodiment, more than three frequencies are possible by increasing the number of partitions in the vibration propagation member and setting different values ​​for the membrane surface length. The more partitions there are, the more types of gases can be distinguished, and the higher the discrimination accuracy. This allows for discrimination even when the frequency characteristic curves are close together, enabling heat flow measurement for a wider range of gas types.

[0079] Furthermore, while the characteristics of the received signal strength when the frequency changes were used as a criterion for identifying the gas type, other received signal characteristics, such as attenuation rate, may also be used. Also, although a rectangular film surface shape is shown, it is not limited to this and can be circular, elliptical, polygonal, etc. Also, although a one-dimensional arrangement of the film structure is shown, a two-dimensional arrangement is also possible.

[0080] Furthermore, while the procedure for measuring heat flow rate involves sequentially measuring temperature, identifying gas type, and measuring flow rate, this is not the only possible order. It is also possible to perform these operations in parallel.

[0081] Furthermore, while a rectangular cross-section channel was shown as an example of the channel shape, it is also possible to use a multi-layer channel in which the shorter side of the rectangular cross-section is divided into multiple sections by partition plates. [Industrial applicability]

[0082] As described above, the vibration propagation member of the present invention can transmit and receive multiple frequencies, and by attaching a piezoelectric element to the vibration propagation member and applying it as a transducer for fluid type discrimination, it can be configured to accurately distinguish between a wide range of fluids. Therefore, it can be widely used in applications requiring measurement of the heat flow rate of various fluids, such as heat flow meters for various fluids and their application products such as gas meters. [Explanation of Symbols]

[0083] 1.51 Vibration transmission member 6, 7, 8, 9 bulkhead 13,14,15 Membrane structure 16 Transducers 17. Vibrating Body 20 Calorie flow meter 21 Flow channels 22, 23 Transducers 26 Temperature Sensor 27 Measurement and Control Unit 28 Memory section 29 Signal Processing Unit 29a Fluid type determination processing unit 29b Flow rate measurement processing unit 29c Heat flow calculation section

Claims

[Claim 1] The flow path through which the fluid to be measured flows, A pair of transducers arranged upstream and downstream of the aforementioned flow path, A temperature sensor for measuring the temperature of the fluid to be measured flowing through the aforementioned channel, A measurement control unit that controls the transmission and reception operations of the pair of transducers and the temperature measurement operation of the temperature sensor, A signal processing unit that processes the received signals from the pair of transducers and the temperature signal obtained from the temperature sensor, The system includes a storage unit that stores a first table defining the relationship between the type of fluid to be measured, its temperature, and its density, and a second table defining the relationship between the type of fluid to be measured and its heat generation. The aforementioned transducer is configured to transmit and receive signals at multiple resonant frequencies. The signal processing unit, A fluid type determination unit that determines the type of the fluid to be measured based on the signal characteristics of received signals at multiple resonant frequencies, A flow rate calculation unit that measures the flow rate of the fluid to be measured using one of the aforementioned plurality of resonance frequencies, A heat flow meter comprising: the type of fluid to be measured identified by the fluid type determination unit; the flow rate calculated by the flow rate calculation unit; the temperature measured by the temperature sensor; and a heat flow rate calculation unit that determines the heat flow rate of the fluid to be measured based on the first and second tables.

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