Heat flow meter

Abstract

To provide a calorific flow meter using a transducer capable of sending out ultrasound waves at multiple frequencies with a simple structure.SOLUTION: Gas type identification and flow measurement are performed by using a pair of transducers 22 and 23 capable of transmission and reception of multiple frequencies and a temperature sensor 26, measuring ultrasonic reception strength, propagation time, and temperature while switching of these by a measurement control unit 27, and processing the signals obtained from these by a signal processing section 29. The heat quantity flow rate is measured by using the data, and a density table and a calorific value table stored in a storage unit 28 in advance.SELECTED DRAWING: Figure 6

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 transducer configured to emit ultrasonic waves of multiple frequencies from a single member by utilizing a vibration propagation member that operates by being joined to a vibrating body. [Background technology]

[0002] BACKGROUND ART Conventionally, there is known a device that measures gas values ​​(calorific value, etc.) by transmitting a plurality of frequencies (see, for example, Patent Document 1).

[0003] FIG. 13 is a schematic diagram of a gas level measurement device using a conventional transducer. In FIG. 13, gas level measurement device 101 has gas inlet 102 and outlet 103. Transducers 105 and 106 are arranged so that measurement is performed by measurement unit 104. Transducers 105 and 106 transmit and receive at a first frequency f1. Also, ultrasonic transducer 108 and reflector 109 are arranged opposite each other so that measurement is performed by measurement unit 107. Ultrasonic transducer 108 transmits and receives at a second frequency f2. In this manner, transducers 105 and 106 constitute measurement system 110. Also, ultrasonic transducer 108 and reflector 109 constitute measurement system 111.

[0004] In this configuration, the gas to be measured flows in through inlet 102, passes through measuring section 104, and flows out through outlet 103. During this time, this gas also fills measuring section 107. In measuring section 104, the amount of gas attenuation is measured by ultrasonic waves of frequency f1 transmitted and received between transducers 105 and 106. In addition, the amount of gas attenuation is measured by ultrasonic waves of frequency f2 transmitted and received between ultrasonic transducer 108 and reflector 109. Using these attenuation amounts at frequencies f1 and f2, the gas value of the measured gas is derived based on a pre-stored relationship between the frequency and the gas value (heat value, etc.) associated with the attenuation amount. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 11-511260 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional gas value measurement device, in order to use two types of frequencies to identify the gas type, three transducers and two measurement systems composed of them are required, and the number of parts is large, which makes the configuration complicated and the size large, leading to problems such as increased costs.In addition, since the attenuation is measured at different positions, if the temperature at each position is different, the attenuation value will also be different, which causes problems such as limited discrimination accuracy.

[0007] The present invention addresses the above-mentioned problems, and provides a vibration propagation member that is joined to one surface of a vibrating body and operates, the vibration propagation member being formed of a top plate, a bottom plate, side walls, and partition walls disposed approximately perpendicular to the top plate and the bottom plate, and using vibrations generated in a plurality of membrane structures formed by the top plate and the partition walls, and by setting the spacing between the partition walls to different values ​​so that the plurality of membrane structures generate different resonance frequencies, by attaching an ultrasonic vibrator to the vibration propagation member and using a transmitter / receiver that can transmit and receive signals of a plurality of frequencies using a single member, it is possible to transmit and receive signals of a plurality of gas types using a single system. The purpose is to realize calorie flow measurement by performing discrimination and flow measurement. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems of the related art, a calorimetric 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 by the temperature sensor, a signal processing unit for processing the reception signals of the pair of transducers and the temperature signal obtained by the temperature sensor, and a memory 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, wherein the transducers are configured to transmit and receive a plurality of resonant frequencies, and the signal The processing unit has a fluid type determination unit that determines the type of fluid to be measured based on the signal characteristics of the received signals of 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 calculates 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 makes it possible to configure a system that can transmit and receive multiple frequencies using only one vibration propagation member, and by using a transmitter / receiver that uses this, a highly accurate heat flow meter can be configured with a single system. [Effects of the Invention]

[0009] The calorific flow meter of the present invention can be configured to transmit and receive signals at multiple frequencies using only one vibration propagation member, and by using a transmitter / receiver incorporating this, measurements can be made using a single system. Since flow rate measurement and gas type discrimination can be performed in the same location, calorific flow measurement with high discrimination accuracy is possible. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an exploded perspective view of a vibration propagation member according to a first embodiment of the present invention; [Figure 2] 1 is a cross-sectional view of a vibration propagation member according to a first embodiment of the present invention; [Figure 3] 1A and 1B are diagrams illustrating a method for forming a vibration propagation member according to the first embodiment of the present invention. [Figure 4] 1 is a cross-sectional view of a transducer according to a first embodiment of the present invention; [Figure 5] Characteristics graph of the transducer according to the first embodiment of the present invention [Figure 6] 1 is a schematic diagram of a calorie flow meter according to a first embodiment of the present invention; [Figure 7] FIG. 1 is a configuration diagram of a gas type determination signal processing unit according to a first embodiment of the present invention. [Figure 8] FIG. 1 is a configuration diagram of a signal processing unit for flow rate measurement according to a first embodiment of the present invention. [Figure 9] Frequency characteristic diagram of gas in embodiment 1 of the present invention [Figure 10] FIG. 10 is a table showing how density is calculated from gas type and temperature according to the first embodiment of the present invention. [Figure 11] FIG. 10 is a table showing how to calculate the calorific value from the type of gas in the first embodiment of the present invention. [Figure 12] Flowchart for determining the heat flow rate in the first embodiment of the present invention [Figure 13] Schematic diagram of a gas value measuring device using a conventional transducer DETAILED DESCRIPTION OF THE INVENTION

[0011] A first aspect of the present invention provides a fluid measurement device comprising: 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 by 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 amount of the fluid to be measured, wherein the transducers are configured to transmit and receive signals at a plurality of resonance frequencies, and the signal processing unit is a fluid type determination unit for determining the type of the fluid to be measured based on the signal characteristics of the received signals at a plurality of resonance frequencies. and a flow rate calculation unit that measures the flow rate of the fluid to be measured using one of the plurality of resonant frequencies, and a heat flow rate calculation unit that calculates 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 makes it possible to configure a system that can transmit and receive multiple frequencies using only one vibration propagation member, and by using a transmitter / receiver that uses this, it is possible to perform highly accurate heat flow rate measurements with a single system.

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

[0013] 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) Structure of vibration transmission member The configuration of the vibration propagation member of the transducer used in this embodiment will be described with reference to FIGS.

[0015] Figure 1 is an exploded perspective view of a vibration propagation member. As shown in Figure 1, vibration propagation member 1 is composed of a top plate 2, a bottom plate 3, and a plurality of partitions 6, 7, 8, and 9 arranged approximately perpendicular to top plate 2 and bottom plate 3 in a space surrounded by side walls 4 and 5. In Figure 1, to make it easier to understand the internal structure of the vibration propagation member, the bottom plate 3 and side wall 5 are shown removed. With this configuration, top plate 2 is divided into membrane surface 10 partitioned by partitions 6 and 7, membrane surface 11 partitioned by partitions 7 and 8, and membrane surface 12 partitioned by partitions 8 and 9.

[0016] Figure 2 shows a cross section of the vibration propagation member 1 in Figure 1. Figure 2(a) is a horizontal cross section taken along line AA' in Figure 1, and Figure 2(b) is a vertical cross section taken along line BB' in Figure 1. As shown in Figure 2(a), the widths (W) of membrane surfaces 10, 11, and 12 are the same, but their lengths (Ma, Mb, Mc) are configured to have the following relationship. This membrane length can also be said to be the distance 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, and 9 are equal, and the thicknesses La of the partition walls 6, Lb of the partition walls 7, Lc of the partition walls 8, and Ld of the partition walls 9 are approximately equal.

[0018] As a result, the vibration propagation member 1 has vibrating portions made up of three membrane structures (each shown by a dotted line): membrane structure 13 made up of partitions 6, 7 and membrane surface 10; membrane structure 14 made up of partitions 7, 8 and membrane surface 11; and membrane structure 15 made up of partitions 8, 9 and membrane surface 12.

[0019] In FIG. 1, the vibration propagation member 1 is configured as separate members, with the top plate 2, bottom plate 3, side walls 4 and 5, and partition walls 6, 7, 8 and 9. However, as shown in FIG. 3, the vibration propagation member 51 can be formed by laminating a plurality of intermediate plates 54, which are formed by etching thin metal (e.g., SUS) plates into a predetermined shape, to form the partition walls and side walls, and then laminating top plates 52 and bottom plates 53 above and below them. The operation of this vibration propagation member will be explained in the next section on the operation of the transducer configuration.

[0020] (2) Transmitter / receiver configuration The configuration of the transducer used in this embodiment will be described with reference to FIGS.

[0021] Fig. 4 shows a cross-sectional view of the transducer 16. The transducer 16 is configured by attaching a vibrating body 17 to the bottom plate 3 of the vibration propagation member 1 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 the first embodiment, and therefore the same parts as in Figs. 1 and 2 are designated by the same numbers.

[0022] Next, the operation of the transducer 16 will be explained with reference to FIG. 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, and the relationship between the length and the resonant frequency of the membrane surface is shown in Figure 5. The horizontal axis of Figure 5 represents the length of the membrane surface (= the spacing between the partition walls), and the vertical axis represents the resonant frequency of the membrane structure.

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

[0025] The operation of the vibration propagation member 1 based on the basic characteristics of the vibration propagation member 1 will be explained with reference to FIG.

[0026] Now, 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 the partitions 6, 7, 8, and 9. At this time, since the lengths of the membranes 10, 11, and 12 are different as mentioned above, the membranes 10, 11, and 12 vibrate at different resonant frequencies. In other words, ultrasonic waves of different frequencies are emitted from the membranes 10, 11, and 12, with the resonant frequency of the membrane 10, which has a shorter membrane length, being higher and the resonant frequency of the membrane 12, which has a longer membrane length, being lower.

[0027] The above is the case where the transducer 16 is used for transmitting ultrasonic waves, but even when it is used for receiving waves, the relationship between the membrane length and the resonance frequency remains the same, so it is sufficient to consider this relationship. In other words, in Figure 4, when an ultrasonic wave reaches the membrane surface, the resonance frequency values ​​of the membrane surfaces 10, 11, and 12 correspond in this order from largest to smallest.

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

[0029] As explained above, this transducer can control the resonant frequency by changing the membrane length, and as a result, ultrasonic waves of multiple resonant frequencies can be transmitted from the top plate. In other words, with a simple configuration consisting of one vibrating body and one vibration propagating body, ultrasonic waves of multiple resonant frequencies can be transmitted and received simultaneously.

[0030] (3) Configuration of the heat flow meter The configuration of the calorimeter flow meter of this embodiment will be described with reference to FIGS.

[0031] FIG. 6 shows a cross section of a calorimetric flowmeter 20 according to the first embodiment of the present invention. A 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 on the short sides of the rectangular cross section to face each other. The transducers 22 and 23 are the transducers described in (2) Transmitter-Receiver Configuration above. That is, the transducers used have a membrane length as shown in FIG. 4. In FIG. 6, an arrow 24 indicates the flow direction of the fluid to be measured. The pair of transducers 22 and 23 are arranged to face each other so as to intersect the flow of the fluid to be measured. In this case, the transducers 22 and 23 are arranged so that the portions of the membrane length that are equal in length face each other in the configuration of FIG. 4. The direction of transmission and reception of the transducers 22 and 23 can be switched by a switching unit 25.

[0032] A temperature sensor 26 is disposed at a position where it can measure the temperature of the fluid to be measured. The measurement control unit 27 controls the measurement operations of the switching unit 25 and the temperature sensor 26. The memory unit 28 stores tables and the like for the calorific flow rate calculation described below. The signal processing unit 29 processes signals obtained from the transducers 22 and 23 and signals from the temperature sensor 26, and also performs calculations while referring to data and the like stored in the memory unit 28. This signal processing unit 29 has a fluid type discrimination processing unit 29a that discriminates the gas type, a flow rate measurement processing unit 29b that calculates the flow rate of the fluid to be measured, and a calorific flow rate calculation unit 29c that calculates the calorific flow rate of the fluid to be measured, which will be described below.

[0033] FIG. 7 is a configuration diagram of the fluid type determination processing unit 29a of the signal processing unit 29 in the calorimetric flowmeter of the present invention.

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

[0035] When gas type discrimination is performed, processing units A34, B35, and C36 have the function of measuring the reception strength of the received waves that have passed through filters A31, B32, and C33, respectively, and gas type discrimination unit 37 has the function of discriminating the gas type of the fluid to be measured based on these reception strengths using a method described later.

[0036] FIG. 8 is a configuration diagram of the flow rate measurement processing unit 29b of the signal processing unit 29 in the calorimetric flowmeter of the present invention.

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

[0038] FIG. 9 is a diagram showing a simulated frequency characteristic of a gas, which is a fluid to be measured. In FIG. 9, the horizontal axis represents frequency f, and the vertical axis represents the reception strength S at a given distance when a given signal is transmitted for the target gas. Gases Ga and Gb have different frequency characteristics (signal characteristics of the received signal). Gas Ga exhibits a monotonically decreasing trend with changes in frequencies f1, f2, and f3, but has a minimum value. Therefore, by using this characteristic diagram and knowing the reception strength at a specific frequency (e.g., f1, f2, or f3), it is possible to distinguish between gases Ga and Gb from the trend and value.

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

[0040] [1-2. Operation] The operation of the calorie flowmeter that measures the calorie flow rate based on the above configuration will now be described.

[0041] In explaining the operation of this calorie flow rate measurement, the gas type discrimination and flow rate measurement operations performed as the preceding operations will be explained first, and then the calorie flow rate measurement operation will be explained.

[0042] (a) Gas type discrimination operation The gas type determination operation will be described with reference to FIGS.

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

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

[0045] Next, the processing contents of the fluid type determination processing unit 29a of the signal processing unit 29 will be described with reference to FIG. The signal input to the signal processing unit 29 is converted into a digital signal by the A / D conversion unit 30. Thereafter, the signal is filtered by a filter A31 of frequency f1, a filter B32 of frequency f2, and a filter C33 of frequency f3, and the reception strength at each frequency is obtained by processing units A34, B35, and C36, respectively.

[0046] These reception intensity data are compared in the gas type determination unit 37 with the reception intensities at the frequencies f1, f2, and f3 in FIG. 9 that are stored in advance, and the type of gas that is the fluid to be measured can be determined.

[0047] (b) Flow rate measurement operation Next, the flow rate measurement operation will be described with reference to FIGS.

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

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

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

[0051] 6, the measurement control unit 27 controls the switching unit 25 to transmit and receive ultrasonic waves in the opposite direction to the previous direction. That is, after transmitting a drive signal to the transducer 23 and transmitting ultrasonic waves into the fluid to be measured, the ultrasonic waves transmitted into the fluid to be measured propagate toward the transducer 22 and are received by the transducer 22.

[0052] 8, the signal processing unit 29 measures the propagation time (t2) in the opposite direction to the initial propagation time. Using these propagation times t1 and t2, the flow rate is calculated by a flow rate calculation unit 41 using a 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, the calorific flow rate measurement operation of the calorific flow rate calculation unit 29c of the signal processing unit 29 will be explained below using Figures 10, 11, and 12.

[0054] FIG. 12 is a flowchart of the calorie flow rate measurement operation of the calorie flow rate calculation unit 29c. The processing shown in this flowchart is performed by the measurement control unit 27 and the signal processing unit 29 shown in FIG.

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

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

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

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

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

[0061] Next, the operation sequence of the calorie flow rate measurement operation will be described with reference to the flowchart of FIG.

[0062] First, a measurement operation is started by a start command (step S1). Next, the conditional branch designation number n is initialized to 0 by a command (step S2). A constant n is set to an initial value (0). After that, an instruction to increase n (step S3) increases the value of n by "1" and sets n=1.

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

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

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

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

[0067] Next, the process proceeds to a reception intensity measurement command (step S8), where reception intensity measurements are performed at three frequencies using the method already described in the above (a) gas type discrimination operation, and then the gas type is discriminated by gas type discrimination (step S9). The discriminated gas type is stored in memory unit 28 by a storage command (step S10). Then, the process returns to the command to increase n (step S3).

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

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

[0070] Next, a propagation time measurement command (step S12) is issued to perform propagation time measurement at one of the three frequencies using the method already described in (b) Flow rate measurement operation above, and then a flow rate calculation command (step S13) is executed.

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

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

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

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

[0075] Thereafter, a calorie flow rate calculation command (step S17) is issued to multiply the flow rate (Q) by the density (ρ) and further multiply this by the calorific value (C), thereby obtaining the calorie flow rate.

[0076] Thereafter, after a predetermined interval command (step S18), the same operation is repeated to continue measuring the calorific flow rate of the fluid to be measured.

[0077] [1-3.Effects] As described above, the calorific flowmeter of the present invention can measure the calorific flow rate with high accuracy using a simple configuration by using a transducer capable of transmitting and receiving signals at a plurality of frequencies.

[0078] Although three types of frequencies were used in the present embodiment, three or more types are possible by increasing the number of partition walls of the vibration propagation member and setting different film surface lengths. The more the number, the more types of gases that can be distinguished. In addition, since the accuracy of distinction can be improved, distinction is possible even when the frequency characteristic curves are close to each other, and calorific flow measurement corresponding to a greater number of gases becomes possible.

[0079] Furthermore, although the characteristics of the reception intensity when the frequency changes are used as a criterion for distinguishing the gas type, reception signal characteristics other than reception intensity, such as attenuation rate, may also be used. Furthermore, although a rectangular shape is shown as the shape of the membrane surface, it is not limited to this and may be a circle, an ellipse, a polygon, etc. Furthermore, although a one-dimensional membrane structure arrangement is shown, a two-dimensional arrangement is also possible.

[0080] Furthermore, although the procedure for measuring the calorific flow rate has been described as a method of sequentially measuring the temperature, determining the gas type, and measuring the flow rate, the order of these steps is not limited to this. These steps can also be performed in parallel.

[0081] Furthermore, although the flow path has a rectangular cross section, it is also possible to use a multi-layer flow path in which the short side direction of the rectangular cross section is divided into a plurality of sections by partition plates. [Industrial Applicability]

[0082] As described above, the vibration propagation member of the present invention is capable of transmitting and receiving signals at multiple frequencies, and by applying it to fluid type discrimination as a transmitter / receiver with a piezoelectric body attached to the vibration propagation member, it can be configured to accurately discriminate between a wide variety of fluids.Therefore, it can be widely used in applications requiring measurement of the calorific flow rate of a fluid, such as calorific flow meters for various fluids and gas meters, which are application products thereof. [Explanation of symbols]

[0083] 1, 51 Vibration transmission member 6, 7, 8, 9 bulkhead 13,14,15 Membrane structure 16 Transmitter / Receiver 17 Vibration body 20 Calorie flow meter 21 Flow path 22, 23 Transducer 26 Temperature Sensor 27 Measurement control section 28 Memory section 29 Signal Processing Section 29a Fluid type discrimination processing section 29b Flow measurement processing section 29c Heat flow calculation section

Claims

[Claim 1] a flow path through which a fluid to be measured flows; a pair of transducers disposed upstream and downstream of the flow path; a temperature sensor that measures the temperature of the fluid to be measured flowing through the flow path; 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 by the temperature sensor; a storage unit that stores a first table that defines the relationship between the type of the fluid to be measured, the temperature, and the density of the fluid, and a second table that defines the relationship between the type of the fluid to be measured and the calorific value of the fluid, The transducer is configured to be capable of transmitting and receiving signals at a plurality of resonant frequencies, The signal processing unit a fluid type determination unit that determines the type of the fluid to be measured based on signal characteristics of received signals of a plurality of resonance frequencies; a flow rate calculation unit that measures a flow rate of the fluid to be measured using one of the plurality of resonance frequencies; a calorific flow rate calculation unit that calculates the calorific flow rate of the fluid to be measured based on the type of the 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.

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