Measuring device

Abstract

A measurement device 1 according to the present disclosure is a measurement device 1 for measuring the flow rate of a fluid flowing in a flow channel F, the measurement device 1 comprising: a plurality of pressure sensors 10 respectively arranged at a plurality of positions in the flow channel F; a single reference power source 20 configured to provide a common voltage reference to each pressure sensor 10; a single counter circuit 40 configured to commonly count the frequency of the output signal output from each pressure sensor 10, the frequency being used to calculate the pressure of the fluid at the corresponding location, the pressure being associated with the flow rate; and a single excitation source 50 configured to provide a frequency reference to the counter circuit 40.

Description

[0001] Cross-referencing related applications

[0002] This application claims priority to Japanese Patent Application No. 2023-045953, filed on March 22, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a measuring device. Background Technology

[0004] Technology related to measuring devices for measuring the flow rate of fluid flowing in a flow channel is known. This technology uses multiple pressure gauges arranged at multiple locations within the flow channel. These pressure gauges measure the pressure of the fluid at the installation location based on sensing elements having diaphragms and oscillators.

[0005] For example, Patent Document (PTL) 1 discloses an oscillation sensor measuring device that achieves stable oscillation of the oscillator, improves the measurement accuracy of physical quantities through noise removal, and increases the oscillator output.

[0006] Reference List

[0007] Patent documents

[0008] PTL 1:JP 2010-210371 A Summary of the Invention

[0009] (Technical issue)

[0010] In conventional flow measurement devices for fluids, as described in Patent Document 1, each pressure gauge has a diaphragm and an oscillator. Additionally, each pressure gauge includes a reference power supply for providing a bias voltage applied between the oscillator and a fixed electrode. Furthermore, each pressure gauge also includes a counter circuit for counting the frequency of the output signal from the sensing element with the oscillator, and an excitation source for providing a frequency reference to the counter circuit. This configuration results in significant individual variability in the characteristics of each pressure gauge, thereby reducing the accuracy of flow measurement.

[0011] The purpose of this disclosure is to provide a measuring device that can improve the measurement accuracy of the flow rate of a fluid flowing in a flow channel.

[0012] (Solution to the problem)

[0013] A measurement device according to some embodiments is a measurement device for measuring a flow rate of a fluid flowing in a flow passage, the measurement device including a plurality of pressure sensors respectively arranged at a plurality of positions within the flow passage; a single reference power source configured to provide a common voltage reference to each of the plurality of pressure sensors; a single counter circuit configured to count a frequency of an output signal output from each of the plurality of pressure sensors, the frequency being used to calculate a pressure of the fluid at the corresponding position, the pressure being associated with the flow rate; and a single excitation source configured to provide a frequency reference to the counter circuit.

[0014] This configuration can improve the measurement accuracy of the flow rate of the fluid flowing in the flow passage. The measurement device has a single reference power source, a single counter circuit, and a single excitation source, which can be commonly arranged to the plurality of pressure sensors. Thus, the measurement device is capable of synchronous simultaneous measurement of each of the pressure sensors.

[0015] In addition, the measurement device can reduce individual differences in characteristics of each of the pressure sensors, and improve the accuracy of the flow rate measurement. For example, by arranging a common reference power source to each of the pressure sensors, the relative accuracy of the outputs between the respective sensing elements based on the reference power source is improved. For example, by arranging a common excitation source to each of the pressure sensors, the relative quantization error caused by the excitation source is reduced. Furthermore, the long-term stability due to the reference power source and the excitation source is also improved, thereby suppressing a decrease in the relative accuracy over time.

[0016] The measurement device can also contribute to reducing the board space by sharing the circuit portion between the plurality of pressure sensors. This is advantageous in reducing the size of a measurement system including the measurement device.

[0017] In one embodiment, the measurement device can further include a single arithmetic circuit configured to calculate the pressure of the fluid at the corresponding position based on the frequency counted by the counter circuit.

[0018] This enables the measurement device to arrange the plurality of pressure sensors and the arithmetic circuit within the same device. Thus, the measurement device is capable of contributing to reducing the size by reducing the space occupied by a measurement system including the measurement device, while enabling synchronous simultaneous measurement of each of the pressure sensors.

[0019] In one embodiment, in the measurement device, the arithmetic circuit can be configured to calculate the flow rate based on a pressure difference of the fluid between the plurality of positions. This enables the measurement device to accurately measure the flow rate of the fluid flowing in the flow passage.

[0020] In one embodiment, the measurement device can further include a communication interface configured to transmit the calculation result from the operation circuit to an external device.

[0021] This enables the measurement device to provide the calculation result of the operation circuit as information to the external device as needed. Therefore, the measurement device can cause the external device to display the calculation result as information, and also prompt the user to confirm the information. The measurement device can cause the external device to display the measurement parameters such as the respective pressures, the pressure difference, and the flow rate calculated by the operation circuit, and prompt the user to confirm the measurement parameters.

[0022] In one embodiment, in the measurement device, each of the plurality of pressure sensors can include a diaphragm configured to receive the pressure of the fluid and a sensing element configured to output an output signal having a frequency corresponding to the pressure received by the diaphragm.

[0023] This enables the measurement device to output the output signal from each of the pressure sensors at a frequency corresponding to the pressure received by the diaphragm. The measurement device can thereby calculate the flow rate of the fluid based on the pressure difference between the plurality of positions of the fluid in the flow passage.

[0024] In one embodiment, in the measurement device, the sensing element can include two oscillators configured to output the output signal and one diode configured to output a voltage proportional to the ambient temperature. This enables the measurement device to receive information on the two resonance frequencies and one diode conduction voltage in the operation circuit, and calculate the pressure of each of the pressure sensors based on Equations (1) to (3) described below.

[0025] In one embodiment, in the measurement device, the plurality of pressure sensors can include a first pressure sensor and a second pressure sensor, and the single counter circuit can be configured to count a first frequency for calculating a first pressure of the fluid at a first position where the first pressure sensor is arranged and a second frequency for calculating a second pressure of the fluid at a second position where the second pressure sensor is arranged in common. This enables the measurement device to have two pressure sensors in a single device and measure two pressures at the same time.

[0026] (Beneficial Effects)

[0027] According to the present disclosure, it is possible to provide a measurement device capable of improving the measurement accuracy of the flow rate of a fluid flowing in a flow passage. BRIEF DESCRIPTION OF DRAWINGS

[0028] In the drawings:

[0029] Figure 1is a schematic diagram showing an example configuration of a measurement device according to an embodiment of the present disclosure;

[0030] Figure 2 is a block diagram showing a more detailed example configuration of the measurement device in Figure 1

[0031] Figure 3 is a schematic diagram showing an example configuration of a measurement device according to a modification example of the present disclosure; and

[0032] Figure 4 is a schematic diagram showing a schematic configuration of a conventional measurement system. DETAILED DESCRIPTION

[0033] The background and problems of the conventional technology are described in more detail.

[0034] Figure 4 is a schematic diagram showing a schematic configuration of a conventional measurement system 100. The measurement system 100 measures the flow rate of a fluid flowing in a flow passage F. The flow passage F includes a first flow passage Fl, a second flow passage F2, and a third flow passage F3. The first flow passage Fl, the second flow passage F2, and the third flow passage F3 represent flow passages of fluids such as gases and liquids. The first flow passage Fl, the second flow passage F2, and the third flow passage F3 differ from each other in shape and the like. Therefore, the flow passage resistances in these flow passages differ from each other. The second flow passage F2 is, for example, a flow passage having a known flow passage resistance, and a fluid flows in the second flow passage F2 at a known flow rate when there is a difference in fluid pressure at the left and right ends of the second flow passage F2.

[0035] The measurement system 100 has a first pressure gauge 110 and a second pressure gauge 120 at both ends of the second flow passage F2 having a known flow passage resistance, to measure the flow rate of a fluid flowing in the flow passage F. The measurement system 100 measures the pressure difference at both ends of the second flow passage F2 using the first pressure gauge 110 and the second pressure gauge 120. The measurement system 100 measures the flow rate of a fluid flowing in the second flow passage F2 on the basis of the measured pressure difference and the known flow passage resistance of the second flow passage F2.

[0036] The measurement system 100 has two pressure gauges necessary to measure the flow rate of a fluid, which are provided at both end portions of the second flow passage F2 and the measurement system 100 calculates the pressure difference between the obtained pressures using a calculator 130 provided separately from the first pressure gauge 110 and the second pressure gauge 120. The measurement system 100 transmits the calculation result obtained by the calculator 130 to an externally connected device communicably as needed.

[0037] ​The first pressure gauge 110 and the second pressure gauge 120 are used to measure a pressure difference between the left end and the right end of the second flow passage F2. The first pressure gauge 110 has, in order from the first flow passage Fl side, a diaphragm 111, a sensing element 112, a reference power supply 113, an amplifier 114, a counter circuit 115, an excitation source 116, and an arithmetic circuit 117. The second pressure gauge 120 has, in order from the third flow passage F3 side, a diaphragm 121, a sensing element 122, a reference power supply 123, an amplifier 124, a counter circuit 125, an excitation source 126, and an arithmetic circuit 127.

[0038] The diaphragm 111 receives the first pressure Pl of the fluid flowing in the first flow passage Fl and is bent with a predetermined tension. The amount of deformation of the diaphragm 111 depends on the first pressure Pl. The sensing element 112 outputs a current having a resonance frequency as an output signal, the resonance frequency depending on the amount of deformation of the diaphragm 111, i.e., on the first pressure Pl. The resonance frequency of the current changes in accordance with a change in the first pressure Pl of the fluid flowing in the first flow passage Fl.

[0039] The reference power supply 113 applies a bias voltage to the sensing element 112 so that the current having such a resonance frequency is output from the sensing element 112. The amplifier 114 amplifies the output signal from the sensing element 112. The counter circuit 115 counts the resonance frequency of the output signal output from the sensing element 112 and amplified by the amplifier 114. The excitation source 116 provides a frequency reference to the counter circuit 115. The arithmetic circuit 117 calculates the first pressure Pl of the fluid flowing in the first flow passage Fl on the basis of the resonance frequency counted by the counter circuit 115.

[0040] The first pressure Pl measured by the first pressure gauge 110 as described above is transmitted as information to the upper calculator 130 using a communication function of the first pressure gauge 110.

[0041] Each configuration included in the second pressure gauge 120 has the same function as the corresponding configuration included in the first pressure gauge 110. The aforementioned method of measuring the first pressure Pl of the fluid flowing in the first flow passage Fl using the first pressure gauge 110 is equally applicable to the case of measuring the second pressure P2 of the fluid flowing in the third flow passage F3 using the second pressure gauge 120.

[0042] However, in the conventional measurement system 100, the first pressure gauge 110 and the second pressure gauge 120 are arranged independently of each other. Therefore, due to individual differences in characteristics of each pressure gauge, the accuracy of the flow rate measurement is reduced. It is difficult to make the characteristics of the first pressure gauge 110 and the second pressure gauge 120 exactly the same, and differences in the characteristics inevitably occur. For example, in each pressure gauge, a reference power supply and an excitation source are arranged separately. Based on differences in the reference power supply, this causes a reduction in the relative accuracy of the output of each sensing element between the first pressure gauge 110 and the second pressure gauge 120, and based on differences in the excitation source, this causes a significant relative quantization error. The long-term stability due to these factors is also reduced, causing the relative accuracy to further reduce over time.

[0043] In addition, in the conventional measurement system 100, the superior calculator 130 needs to be arranged separately from the first pressure gauge 110 and the second pressure gauge 120 in order to calculate the pressure difference. The first pressure gauge 110 and the second pressure gauge 120 need to be arranged separately, thereby increasing the space occupied by the measurement system 100 as a whole. For example, it is necessary to separately provide a reference power supply, a counter circuit, an excitation source, and an arithmetic circuit for one pressure gauge, which also increases the space occupied by each pressure gauge.

[0044] To solve the above problems, it is an object of the present disclosure to provide a measurement device capable of improving the accuracy of the measurement of the flow rate of a fluid flowing in a flow passage F.

[0045] Hereinafter, embodiments of the present disclosure will be described mainly with reference to the accompanying drawings.

[0046] Figure 1 is a schematic view showing an example configuration of a measurement device 1 according to an embodiment of the present disclosure. Figure 2 is a schematic view showing an example configuration of the measurement device 1 of Figure 1 is a block diagram showing a more detailed example configuration of the measurement device 1 of Figure 1 and Figure 2 will be described mainly with reference to

[0047] The measurement device 1 is used to measure the flow rate of a fluid flowing in a flow passage F. The measurement device 1 measures the flow rate of a fluid flowing in the flow passage F. In the present disclosure, "fluid" includes a gas, a liquid, and the like. The flow passage F includes a first flow passage Fl, a second flow passage F2, and a third flow passage F3. The first flow passage Fl, the second flow passage F2, and the third flow passage F3 represent flow passages of a fluid. The first flow passage Fl, the second flow passage F2, and the third flow passage F3 differ from each other in shape and the like. Therefore, the flow passage resistances of the flow passages among these differ from each other. The second flow passage F2 is, for example, a flow passage having a known flow passage resistance in which a fluid flows at a known flow rate in the second flow passage F2 when there is a fluid pressure difference between the left end and the right end of the second flow passage F2. The fluid flows through the inside of the flow passage F in the order of the first flow passage Fl, the second flow passage F2, and the third flow passage F3, for example.

[0048] The measurement device 1 has a plurality of pressure sensors 10, a single reference power supply 20, a plurality of amplifiers 30, a single counter circuit 40, a single excitation source 50, a single arithmetic circuit 60, and a single communication interface 70. As described below, each pressure sensor 10 has a diaphragm 11 that receives a fluid pressure and a sensing element 12 that outputs an output signal having a frequency corresponding to the pressure received by the diaphragm 11.

[0049] The plurality of pressure sensors 10 are respectively provided at a plurality of positions in the flow passage F. For example, in the measurement device 1, the plurality of pressure sensors 10 include a first pressure sensor 10a and a second pressure sensor 10b. The first pressure sensor 10a is arranged in the first flow passage Fl at a first position LI adjacent to one end of the second flow passage F2. The second pressure sensor 10b is arranged in the third flow passage F3 at a second position L2 adjacent to the other end of the second flow passage F2. The first pressure sensor 10a and the second pressure sensor 10b are used to measure the pressure difference between the left end and the right end of the second flow passage F2.

[0050] The first pressure sensor 10a has, in order from the first flow passage Fl side, a first diaphragm 11a and a first sensing element 12a. The first sensing element 12a has a first oscillator 121a, a second oscillator 122a, and a first diode 123a. The first sensing element 12a has two oscillators, namely the first oscillator 121a and the second oscillator 122a, that output output signals.

[0051] The first diaphragm 11a receives the first pressure PI of the fluid flowing in the first flow passage Fl and is bent with a predetermined tension. The amount of deformation of the first diaphragm 11a depends on the first pressure PI. The first sensing element 12a outputs a current having a resonance frequency as an output signal, the resonance frequency depending on the amount of deformation of the first diaphragm 11a, that is, on the first pressure PI. The resonance frequency of the current varies in accordance with a change in the first pressure PI of the fluid flowing in the first flow passage Fl.

[0052] When the first diaphragm 11a receives the first pressure PI of the fluid flowing in the first flow passage Fl and is deformed, the first oscillator 121a of the first sensing element 12a is bent in accordance with the first amount of deformation of the first diaphragm 11a in the first oscillator 121a. The first oscillator 121a has a first resonance frequency determined, for example, by the shape of its beam. Further, based on a first bias voltage applied between the first oscillator 121a and the fixed electrode from the reference power source 20, a first self-oscillation circuit is formed to cause the first oscillator 121a to vibrate at the first resonance frequency. Thus, the first oscillator 121a outputs a first current of the first resonance frequency as an output signal, the first resonance frequency depending on the first amount of deformation of the first diaphragm 11a, that is, on the first pressure PI.

[0053] When the first diaphragm 11a receives the first pressure PI of the fluid flowing in the first flow passage Fl and is deformed, the second oscillator 122a of the first sensing element 12a is bent in accordance with the second amount of deformation of the first diaphragm 11a in the second oscillator 122a. The second oscillator 122a has a second resonance frequency determined, for example, by the shape of its beam. Further, based on a second bias voltage applied between the second oscillator 122a and the fixed electrode from the reference power source 20, a second self-oscillation circuit is formed to cause the second oscillator 122a to vibrate at the second resonance frequency. Thus, the second oscillator 122a outputs a second current of the second resonance frequency as an output signal, the second resonance frequency depending on the second amount of deformation of the first diaphragm 11a, that is, on the first pressure PI.

[0054] The first diode 123a in the first sensing element 12a outputs a voltage proportional to the ambient temperature. The first diode 123a housed inside the first sensing element 12a outputs this voltage by passing a constant current therethrough. The on voltage of such a first diode 123a is used as a temperature output of the first sensing element 12a.

[0055] The second pressure sensor 10b has a second diaphragm 11b and a second sensing element 12b in this order from the third flow passage F3 side. The second sensing element 12b has a third oscillator 121b, a fourth oscillator 122b, and a second diode 123b.

[0056] The second diaphragm 11b receives the second pressure P2 of the fluid flowing in the third flow passage F3 and is bent with a predetermined tension. The amount of deformation of the second diaphragm 11b depends on the second pressure P2. The second sensing element 12b outputs a current having a resonance frequency as an output signal, the resonance frequency depending on the amount of deformation of the second diaphragm 11b, that is, on the second pressure P2. The resonance frequency of the current varies in accordance with a change in the second pressure P2 of the fluid flowing in the third flow passage F3.

[0057] When the second diaphragm 11b receives the second pressure P2 of the fluid flowing in the third flow passage F3 and is deformed, the third oscillator 121b of the second sensing element 12b is bent in accordance with the third amount of deformation of the second diaphragm 11b in the third oscillator 121b. The third oscillator 121b has a third resonance frequency determined, for example, by the shape of its beam. Further, based on a third bias voltage applied between the third oscillator 121b and the fixed electrode from the reference power source 20, a third self-oscillation circuit is formed to cause the third oscillator 121b to vibrate at the third resonance frequency. Thus, the third oscillator 121b outputs a third current of the third resonance frequency as an output signal, the third resonance frequency depending on the third amount of deformation of the second diaphragm 11b, that is, on the second pressure P2.

[0058] When the second diaphragm 11b receives the second pressure P2 of the fluid flowing in the third flow passage F3 and is deformed, the fourth oscillator 122b of the second sensing element 12b is bent in accordance with the fourth amount of deformation of the second diaphragm 11b in the fourth oscillator 122b. The fourth oscillator 122b has a fourth resonance frequency determined, for example, by the shape of its beam. Further, based on a fourth bias voltage applied between the fourth oscillator 122b and the fixed electrode from the reference power source 20, a fourth self-oscillation circuit is formed to cause the fourth oscillator 122b to vibrate at the fourth resonance frequency. Thus, the fourth oscillator 122b outputs a fourth current of the fourth resonance frequency as an output signal, the fourth resonance frequency depending on the fourth amount of deformation of the second diaphragm 11b, that is, on the second pressure P2.

[0059] The second diode 123b in the second sensing element 12b outputs a voltage proportional to the ambient temperature. The second diode 123b housed inside the second sensing element 12b outputs this voltage by passing a constant current therethrough. The on voltage of such a second diode 123b is used as a temperature output of the second sensing element 12b.

[0060] In order to cause the corresponding oscillator to output a voltage having a resonance frequency as an output signal, the reference power supply 20 applies a bias voltage to the oscillators. The reference power supply 20 provides a common voltage reference to each pressure sensor 10. For example, the reference power supply 20 provides a first voltage reference as a basis for a first bias voltage and a second bias voltage applied to the first oscillator 121a and the second oscillator 122a of the first sensing element 12a, respectively. For example, the reference power supply 20 provides a second voltage reference as a basis for a third bias voltage and a fourth bias voltage applied to the third oscillator 121b and the fourth oscillator 122b of the second sensing element 12b, respectively. The first voltage reference and the second voltage reference are common to each other.

[0061] The plurality of amplifiers 30 amplify the outputs from each of the plurality of pressure sensors 10. For example, in the measurement device 1, the plurality of amplifiers 30 includes a first amplifier 30a that amplifies the output from the first pressure sensor 10a and a second amplifier 30b that amplifies the output from the second pressure sensor 10b.

[0062] The counter circuit 40 commonly counts the frequencies of the output signals output from each pressure sensor 10. The counter circuit 40 counts the frequencies of the output signals based on a clock signal that is output from a common excitation source 50 and has a higher frequency than the frequencies of the output signals. The frequencies of the output signals are used to calculate the pressures of the fluid at the respective positions in the flow passage F at which the pressure sensors 10 are disposed. The pressures of the fluid are associated with the flow rate of the fluid.

[0063] For example, the counter circuit 40 counts based on a common clock signal, based on a first resonance frequency of the first oscillator 121a, based on a second resonance frequency of the second oscillator 122a, based on a third resonance frequency of the third oscillator 121b, and based on a fourth resonance frequency of the fourth oscillator 122b. The counter circuit 40 commonly counts a first frequency used to calculate a first pressure PI of the fluid at a first position LI in the flow passage F at which the first pressure sensor 10a is disposed and a second frequency used to calculate a second pressure P2 of the fluid at a second position L2 in the flow passage F at which the second pressure sensor 10b is disposed.

[0064] In the present disclosure, the "first frequency" includes, for example, the first resonance frequency and the second resonance frequency. The "second frequency" includes, for example, the third resonance frequency and the fourth resonance frequency. The first resonance frequency and the second resonance frequency obtained based on the first pressure sensor 10a are used to calculate the first pressure PI of the fluid at the first position LI in the flow passage F at which the first pressure sensor 10a is disposed. The third resonance frequency and the fourth resonance frequency obtained based on the second pressure sensor 10b are used to calculate the second pressure P2 of the fluid at the second position L2 in the flow passage F at which the second pressure sensor 10b is disposed.

[0065] The excitation source 50 supplies a frequency reference to the counter circuit 40. The excitation source 50 outputs a clock signal to the counter circuit 40, which is commonly used for counting the first resonance frequency, the second resonance frequency, the third resonance frequency, and the fourth resonance frequency.

[0066] The arithmetic circuit 60 includes one or more processors. In the present disclosure, the "processor" is a general-purpose processor or a dedicated processor specialized for a specific process, but these examples are not limiting. The arithmetic circuit 60 calculates the pressure of the fluid at the respective positions based on the frequencies counted by the counter circuit 40. The arithmetic circuit 60 is a circuit that performs the calculation using software to output the frequency as a pressure indication value.

[0067] For example, the arithmetic circuit 60 calculates the first pressure P1 of the fluid at the first position L1 where the first pressure sensor 10a is arranged using the first resonance frequency and the second resonance frequency counted by the counter circuit 40 and the on voltage of the first diode 123a output from the first diode 123a of the first sensing element 12a. For example, the arithmetic circuit 60 calculates the second pressure P2 of the fluid at the second position L2 where the second pressure sensor 10b is arranged using the third resonance frequency and the fourth resonance frequency counted by the counter circuit 40 and the on voltage of the second diode 123b output from the second diode 123b of the second sensing element 12b.

[0068] The arithmetic circuit 60 calculates the flow rate of the fluid based on the pressure difference of the fluid between the plurality of positions. For example, the arithmetic circuit 60 calculates the flow rate of the fluid flowing in the second flow passage F2 based on the difference between the first pressure P1 and the second pressure P2, which is the pressure difference of the fluid between the first position L1 where the first pressure sensor 10a is arranged and the second position L2 where the second pressure sensor 10b is arranged.

[0069] The communication interface 70 includes a communication interface that conforms to a communication standard based on any appropriate type of wireless or wired communication. The communication standard includes a wireless LAN (Local Area Network) standard, a short-range wireless communication standard, a mobile communication standard such as 4G (4th Generation) and 5G (5th Generation), and an Internet standard. The measurement device 1 is connected with an information communication network or the like through the communication interface 70. The communication interface 70 transmits the calculation results obtained by the arithmetic circuit 60 to an external device communicably connected with the measurement device 1 via the information communication network as needed.

[0070] The measuring device 1 includes a first pressure sensor 10a and a second pressure sensor 10b disposed across the second flow passage F2 having a known flow passage resistance, to measure the flow rate of the fluid flowing in the flow passage F. The measuring device 1 measures the pressure difference between both ends of the second flow passage F2 using the first pressure sensor 10a and the second pressure sensor 10b. The measuring device 1 measures the flow rate of the fluid flowing in the second flow passage F2 based on the measured pressure difference and the known flow passage resistance of the second flow passage F2.

[0071] In more detail, the arithmetic circuit 60 of the measuring device 1 calculates the pressures obtained by the two pressure sensors 10 disposed at the end portions of the second flow passage F2, respectively, and the pressure difference between these pressures, to calculate the flow rate of the fluid. The arithmetic circuit 60 calculates the pressure P obtained by each pressure sensor 10 based on the following equations (1) to (7). The pressure P corresponds to the first pressure PI or the second pressure P2 described above.

[0072]

[0073] As described above, two oscillators are disposed in the sensing element 12 of each pressure sensor 10. The subscript "C" in the equations (1) to (7) is used to indicate that the term is a parameter associated with one of the two oscillators. The subscript "R" in the equations (1) to (7) is used to indicate that the term is a parameter associated with the other of the two oscillators.

[0074] The description of each parameter included in the equations (1) to (7) is summarized in Table 1 below. The subscript "X" in Table 1 corresponds to "C" or "R" described above.

[0075] [Table 1]

[0076]

[0077]

[0078] In the present disclosure, the "reference state" refers to, for example, a state in which the diaphragm 11 is subjected to the reference pressure of the fluid. The "effective gap length" refers to, for example, the distance between the vibrating beam of the corresponding oscillator and the surface of the fixed electrode opposite to the vibrating beam. The "tension generated in the oscillator in the reference state" refers to, for example, the tensile strain of the vibrating beam.

[0079] For example, in the case where the pressure P corresponds to the first pressure PI, f C corresponds to the first resonance frequency. f R corresponds to the second resonance frequency. f 0C corresponds to the first resonance frequency in the reference state. f 0R corresponds to the second resonance frequency in the reference state. HC , L C , d C , e C , De C correspond to parameters associated with the first oscillator 121a.H R , L R , d R , e R , De R correspond to parameters associated with the second oscillator 122a.V CB corresponds to a first bias voltage.V RB corresponds to a second bias voltage.f TS corresponds to a turn-on voltage of the first diode 123a.f 0TS corresponds to a turn-on voltage of the first diode 123a in a reference state.T corresponds to an ambient temperature of the first sensing element 12a.

[0080] For example, in a case where the pressure P corresponds to the second pressure P2, the equation (1) is expressed as follows.f C corresponds to a third resonance frequency.f R corresponds to a fourth resonance frequency.f 0C corresponds to a third resonance frequency in a reference state.f 0R corresponds to a fourth resonance frequency in a reference state.H C , L C , d C , e C , De C correspond to parameters associated with the third oscillator 121b.H R , L R , d R , e R , De R correspond to parameters associated with the fourth oscillator 122b.V CB corresponds to a third bias voltage.V RB corresponds to a fourth bias voltage.f TS corresponds to a turn-on voltage of the second diode 123b.f 0TS corresponds to a turn-on voltage of the second diode 123b in a reference state.T corresponds to an ambient temperature of the second sensing element 12b.

[0081] In the equation (1), “i” and “j” are used to correct degrees of the pressure P with respect to the parameters X and T, respectively. For example, when the pressure is set on a vertical axis and the resonance frequency is set on a horizontal axis, a graph based on the equation (1) does not necessarily vary linearly. In order to accurately calculate the pressure P, X and T used to calculate the pressure P must be corrected to a predetermined degree. Therefore, for such correction, “n” and “m” are appropriately defined by a user or the like.a ijis a coefficient corresponding to each number of times.

[0082] According to the measuring device 1 in the embodiment described above, the measurement accuracy of the flow rate of the fluid flowing in the flow passage F can be improved. The measuring device 1 has a single reference power supply 20, a single counter circuit 40, and a single excitation source 50, which can be commonly arranged for a plurality of pressure sensors 10. Thus, the measuring device 1 enables simultaneous measurement of each pressure sensor 10 to be synchronized.

[0083] In addition, the measuring device 1 can reduce individual differences in the characteristics of each pressure sensor 10, thereby improving the accuracy of the flow rate measurement. For example, by providing a common reference power supply 20 for each pressure sensor 10, the relative accuracy based on the outputs between the respective sensing elements 12 of the reference power supply 20 can be improved. For example, by providing a common excitation source 50 for each pressure sensor 10, the relative quantization error caused by the excitation source 50 is reduced. Furthermore, the long-term stability attributed to the reference power supply 20 and the excitation source 50 is also improved, thereby suppressing a decrease in the relative accuracy over time.

[0084] The measuring device 1 can also contribute to reducing the board space by sharing the circuit portions among the plurality of pressure sensors 10. This contributes to reducing the size of the measurement system including the measuring device 1.

[0085] By further including a single arithmetic circuit 60, the measuring device 1 can have a plurality of pressure sensors 10 and the arithmetic circuit 60 arranged within the same device. Thus, the measuring device 1 can contribute to reducing the size by reducing the space occupied by the measurement system including the measuring device 1, while enabling simultaneous measurement of each pressure sensor 10 to be synchronized.

[0086] The measuring device 1 can accurately measure the flow rate of the fluid flowing in the flow passage F by causing the arithmetic circuit 60 to calculate the flow rate based on the pressure difference of the fluid.

[0087] By further including a communication interface 70 that transmits the calculation results from the arithmetic circuit 60 to an external device, the measuring device 1 can provide the calculation results from the arithmetic circuit as information to the external device as needed. The measuring device 1 can thus cause the external device to display the calculation results as information, and also prompt the user to confirm the information. The measuring device 1 can cause the external device to display the measurement parameters calculated by the arithmetic circuit 60, such as each pressure P, the pressure difference, and the flow rate, and prompt the user to confirm the measurement parameters.

[0088] By having each pressure sensor 10 include the diaphragm 11 and the sensing element 12, the measuring device 1 can output an output signal at a frequency corresponding to the pressure P received by the diaphragm 11 from each pressure sensor 10. The measuring device 1 can thereby calculate the flow rate of the fluid based on the pressure difference between the plurality of positions of the fluid in the flow passage F.

[0089] By having the sensing element 12 include two oscillators and one diode, the measuring device 1 can receive information on the two resonance frequencies and one diode conduction voltage in the arithmetic circuit 60, and calculate the pressure P of each pressure sensor 10 based on the above equations (1) to (3).

[0090] The plurality of pressure sensors 10 include a first pressure sensor 10a and a second pressure sensor 10b. The counter circuit 40 is common to count the first frequency for calculating the first pressure P1 and the second frequency for calculating the second pressure P2. This enables the measuring device 1 to have two pressure sensors 10 in a single device, and to measure two pressures P at the same time.

[0091] It will be apparent to those skilled in the art that the disclosure can be implemented in some other manner than as described above without departing from the spirit or essential characteristics of the disclosure. Therefore, the above explanation is merely provided by way of non-limiting example. The scope of the disclosure is defined by the appended claims rather than by the above explanation. Various changes in the form and details of the disclosure are considered to be included within the scope of equivalents within the claims.

[0092] For example, the shape, size, arrangement, orientation, and number of the above-described components are not limited to the above explanation or the drawings. The shape, size, arrangement, orientation, and number of each component can be freely selected as long as the function of the component can be achieved. The constituent elements of the measuring device 1 in the drawings are illustrated as functional concepts. The specific form of each constituent element is not limited to the form in the drawings.

[0093] In the above-described embodiment, the measuring device 1 has been described as further including a single arithmetic circuit 60 that calculates the pressure of the fluid at the corresponding position based on the frequencies counted by the counter circuit 40, but this configuration is not limiting. The measuring device 1 does not necessarily include the arithmetic circuit 60.

[0094] In the above-described embodiment, the arithmetic circuit 60 has been described as calculating the flow rate based on the pressure difference between the plurality of positions of the fluid, but this configuration is not limiting. The arithmetic circuit 60 does not necessarily calculate the flow rate. In this case, the measuring device 1 can output only the pressure P and the pressure difference of the fluid as information to an external device. The arithmetic circuit 60 can calculate the flow rate based on a method different from the calculation method based on the pressure difference between the plurality of positions of the fluid.

[0095] In the above-described embodiments, the measurement device 1 is described as further including the communication interface 70 that transmits the calculation result from the arithmetic circuit 60 to the external device, but the configuration is not limiting. The measurement device 1 does not necessarily include the communication interface 70. The measurement device 1 can include the arithmetic circuit 60 without including the communication interface 70, or can omit both the arithmetic circuit 60 and the communication interface 70.

[0096] In the above-described embodiments, each pressure sensor 10 is described as including the diaphragm 11 that receives the pressure of the fluid and the sensing element 12 that outputs the output signal having the frequency corresponding to the pressure received by the diaphragm 11, but the configuration is not limiting. The configuration of the pressure sensor 10 is not limited to the combination of the diaphragm 11 and the sensing element 12, but can be any other configuration capable of measuring the pressure P of the fluid.

[0097] In the above-described embodiments, the sensing element 12 is described as including two oscillators that output the output signal and one diode that outputs the voltage proportional to the ambient temperature, but the configuration is not limiting. The sensing element 12 can have any other configuration capable of outputting the signal required for the arithmetic circuit 60 to calculate the pressure P or the flow rate of the fluid.

[0098] Figure 3 is a schematic diagram showing an example configuration of the measurement device 1 according to a variation of the present disclosure. In the above-described embodiments, the plurality of pressure sensors 10 has been described as including the first pressure sensor 10a and the second pressure sensor 10b, but the configuration is not limiting. The plurality of pressure sensors 10 can include three or more pressure sensors 10 instead of two pressure sensors 10. For example, in addition to the first pressure sensor 10a and the second pressure sensor 10b, the plurality of pressure sensors 10 can include a third pressure sensor 10c for measuring a third pressure P3 of the fluid at a third position L3.

[0099] Therefore, in addition to the first diaphragm 11a and the second diaphragm 11b, the plurality of diaphragms 11 can include a third diaphragm 11c. In addition to the first sensing element 12a and the second sensing element 12b, the plurality of sensing elements 12 can include a third sensing element 12c. In addition to the first amplifier 30a and the second amplifier 30b, the plurality of amplifiers 30 can include a third amplifier 30c.

[0100] In this case, the counter circuit 40 can commonly count a first frequency for calculating a first pressure P1 of a fluid at a first position L1 where the first pressure sensor 10a is arranged, a second frequency for calculating a second pressure P2 of a fluid at a second position L2 where the second pressure sensor 10b is arranged, and a third frequency for calculating a third pressure P3 of a fluid at a third position L3 where the third pressure sensor 10c is arranged.

[0101] As described above, the measurement device 1 can also be applied to a plurality of inputs based on a plurality of pressure sensors 10. The measurement device 1 can simultaneously measure a first pressure P1, a second pressure P2, and a third pressure P3 respectively generated in the first flow passage F1, the second flow passage F2, and the third flow passage F3. The measurement device 1 is not limited to two or three inputs, but can be configured to have four or more inputs depending on the pressure P to be measured.

[0102] Even in the above case, the measurement device 1 includes a single reference power source 20, a single counter circuit 40, and a single excitation source 50 for a plurality of pressure sensors. In the measurement device 1, the reference power source 20 and the excitation source 50 respectively contribute to the relative accuracy and the relative quantization error of the output between the sensing elements 12. By sharing the reference power source 20 and the excitation source 50, which mainly affect the relative accuracy, among the plurality of pressure sensors 10, the measurement device 1 can achieve higher accuracy over a long period of time compared to the case where a plurality of pressure sensors 10 having one input are respectively arranged in a plurality of flow passages F. The measurement device 1 achieves the same effect not only in the case of two inputs as in the above-described embodiment, but also in the case where the device is configured with three or more inputs.

[0103] In the above-described embodiment, the output signal from the sensing element 12 is current-based, but this example is not limiting. The output signal from the sensing element 12 can also be voltage-based.

[0104] In a system configuration of a pressure sensor that performs a simultaneous two-input measurement, for example, the measurement device 1 according to an embodiment of the present disclosure can be used to improve the simultaneous measurement performance, the measurement accuracy, and the long-term stability. For example, the measurement device 1 can be used as a compact, high-accuracy flow measurement device of an in-line type.

[0105] Some embodiments of the present disclosure are illustrated below. However, it should be noted that the embodiments of the present disclosure are not limited to these examples.

[0106] APPENDIX 1. A measurement device for measuring a flow rate of a fluid flowing in a flow passage, the measurement device comprising:

[0107] a plurality of pressure sensors arranged at a plurality of positions within the flow passage, respectively;

[0108] a single reference power supply configured to provide a common voltage reference to each of the plurality of pressure sensors;

[0109] a single counter circuit configured to count a frequency of an output signal output from each of the plurality of pressure sensors, the frequency used to calculate a pressure of the fluid at a corresponding position, the pressure being associated with the flow rate; and

[0110] a single excitation source configured to provide a frequency reference to the counter circuit.

[0111] Appendix 2. The measuring device according to Appendix 1, further comprising a single arithmetic circuit configured to calculate the pressure of the fluid at the corresponding position based on the frequency counted by the counter circuit.

[0112] Appendix 3. The measuring device according to Appendix 2, wherein the arithmetic circuit is configured to calculate the flow rate based on a pressure difference of fluid between the plurality of positions.

[0113] Appendix 4. The measuring device according to Appendix 2 or 3, further comprising a communication interface configured to transmit a result of calculation from the arithmetic circuit to an external device.

[0114] Appendix 5. The measuring device according to any one of Appendices 1 to 4, wherein each of the plurality of pressure sensors comprises a diaphragm configured to receive a pressure of the fluid and a sensing element configured to output an output signal corresponding to the pressure received by the diaphragm at a frequency.

[0115] Appendix 6. The measuring device according to Appendix 5, wherein the sensing element comprises two oscillators configured to output the output signal and one diode configured to output a voltage proportional to an ambient temperature.

[0116] Appendix 7. The measuring device according to any one of Appendices 1 to 6, wherein,

[0117] the plurality of pressure sensors comprises a first pressure sensor and a second pressure sensor, and

[0118] The single counter circuit is configured to count a first frequency for calculating a first pressure of the fluid at a first position where the first pressure sensor is arranged and a second frequency for calculating a second pressure of the fluid at a second position where the second pressure sensor is arranged.

[0119] List of reference signs

[0120] 1 measuring device

[0121] 10 pressure sensor

[0122] 10a first pressure sensor

[0123] 10b second pressure sensor

[0124] 10c third pressure sensor

[0125] 11 diaphragm

[0126] 11a first diaphragm

[0127] 11b second diaphragm

[0128] 11c third diaphragm

[0129] 12 sensing element

[0130] 12a first sensing element

[0131] 121a first oscillator

[0132] 122a second oscillator

[0133] 123a first diode

[0134] 12b second sensing element

[0135] 121b third oscillator

[0136] 122b fourth oscillator

[0137] 123b second diode

[0138] 12c third sensing element

[0139] 20 reference power supply

[0140] 30 amplifier

[0141] 30a first amplifier

[0142] 30b second amplifier

[0143] 30c third amplifier

[0144] 40 counter circuit

[0145] 50 excitation source

[0146] 60 arithmetic circuit

[0147] 70 communication interface

[0148] F flow channel

[0149] F1 first flow channel

[0150] F2 second flow channel

[0151] F3 third flow channel

[0152] L1 first position

[0153] L2 second position

[0154] L3 third position

[0155] P1 first pressure

[0156] P2 second pressure

[0157] P3 third pressure

[0158] 100 measurement system

[0159] 110 first pressure gauge

[0160] 111 diaphragm

[0161] 112 sensing element

[0162] 113 reference power supply

[0163] 114 amplifier

[0164] 115 counter circuit

[0165] 116 excitation source

[0166] 117 arithmetic circuit

[0167] 120 second pressure gauge

[0168] 121 diaphragm

[0169] 122 sensing element

[0170] 123 reference power supply

[0171] 124 amplifier

[0172] 125 counter circuit

[0173] 126 excitation source

[0174] 127 arithmetic circuit

[0175] 130 calculator

Claims

1. A measurement device for measuring a flow rate of a fluid flowing in a flow passage, the measurement device comprising: a plurality of pressure sensors respectively arranged at a plurality of positions within the flow passage; a single reference power source configured to provide a common voltage reference to each of the plurality of pressure sensors; a single counter circuit configured to commonly count a frequency of an output signal output from each of the plurality of pressure sensors, the frequency used to calculate a pressure of the fluid at a corresponding position, the pressure being associated with the flow rate; and a single excitation source configured to provide a frequency reference to the counter circuit. 2.The measurement device according to claim 1, further comprising a single arithmetic circuit configured to calculate the pressure of the fluid at the corresponding position based on the frequency counted by the counter circuit.

3. The measuring device of claim 2, wherein, The arithmetic circuit is configured to calculate the flow rate based on a pressure difference of the fluid between the plurality of positions. 4.The measurement device according to claim 2 or 3, further comprising a communication interface configured to transmit a calculation result from the arithmetic circuit to an external device.

5. The measuring device according to any one of claims 1 to 3, wherein, Each of the plurality of pressure sensors comprises a diaphragm configured to receive a pressure of the fluid, and a sensing element configured to output an output signal having a frequency corresponding to the pressure received by the diaphragm.

6. The measuring device of claim 5, wherein, The sensing element comprises two oscillators configured to output the output signal, and one diode configured to output a voltage proportional to an ambient temperature. 7.The measurement device according to any one of claims 1 to 3, wherein, the plurality of pressure sensors comprise a first pressure sensor and a second pressure sensor, and the single counter circuit is configured to commonly count a first frequency and a second frequency, wherein the first frequency is used to calculate a first pressure of the fluid at a first position where the first pressure sensor is arranged, and the second frequency is used to calculate a second pressure of the fluid at a second position where the second pressure sensor is arranged.

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