Signal processing method, signal processing system, and signal processing program

Abstract

According to one form of the invention, a signal processing method in an assay system is provided. A measurement system in the signal processing method is provided with a thermoelectric conversion unit. On the basis of the abnormal Nernst effect, the thermoelectric conversion unit is configured so as to convert a temperature gradient, which is generated by heat exchange with the measurement target, into an electric signal. The signal processing method includes the following steps. In the modulation step, modulation including a predetermined modulation frequency is introduced into the electrical signal output from the thermoelectric conversion unit, thereby generating a modulated signal. The modulation frequency is a frequency different from the frequency band of the thermoelectric conversion unit. In the extraction step, a signal of a component of a modulation frequency is extracted from the modulation signal.

Description

Technical Field

[0001] The present invention relates to a signal processing method, a signal processing system, and a signal processing program product. Background Art

[0002] Patent Document 1 discloses a technology related to a humidity detection device, which has more excellent responsiveness than conventional ones and is less affected by dew condensation.

[0003] The humidity detection device described in Patent Document 1 includes a heat flux sensor mounted on a side wall surface of a gas-liquid separator that forms an internal space through which fuel exhaust gas flows, and a hydrophilic sheet for generating a liquid film on the surface side of the heat flux sensor. The humidity detection device includes a detection processing unit that performs detection processing for detecting the humidity of fuel exhaust gas based on an output signal output from the heat flux sensor.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Laid-Open No. 2019-086490 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, a signal representing the detection result of a temperature gradient such as a heat flux sensor is very weak compared to a signal directly representing the temperature detection result of a thermometer or the like. Therefore, in order to utilize the signal related to the temperature gradient, for example, there is still room for improvement from various viewpoints such as noise influence and size.

[0009] Means for Solving the Problems

[0010] According to one form of the present invention, there is provided a signal processing method in a measurement system. The measurement system in the signal processing method includes a thermoelectric conversion unit. The thermoelectric conversion unit is configured to convert a temperature gradient generated by heat exchange with a measurement object into an electric signal based on the anomalous Nernst effect. The signal processing method includes the following steps. In the modulation step, a modulation including a predetermined modulation frequency is introduced into the electric signal output from the thermoelectric conversion unit, thereby generating a modulation signal. The modulation frequency is a frequency different from the frequency band of the thermoelectric conversion unit. In the extraction step, a signal of the component of the modulation frequency is extracted from the modulation signal.

[0011] According to this configuration, it is possible to provide a method for more appropriately utilizing a signal representing the detection result of a temperature gradient, etc.

[0012] Brief Description of the Drawings

[0013] Figure 1 It is a diagram showing a configuration example of the measurement system 1a.

[0014] Figure 2 It is a block diagram showing the hardware configuration of the signal processing device 4.

[0015] Figure 3 It is an activity diagram showing an example of signal processing performed in the measurement system 1a.

[0016] Figure 4 It is a graph showing the time variation of the total electromotive force V1 output from one heat flux sensor 2.

[0017] Figure 5 It is a graph showing the time variation of the modulation signal V2.

[0018] Figure 6 It is showing Figure 5 A graph showing an example of the spectrum of the modulation signal V2 shown in.

[0019] Figure 7 It is a graph showing a configuration example of the measurement system 1b.

[0020] Figure 8 It is a graph showing the time variations of the first total electromotive force V1a and the second total electromotive force V1b.

[0021] Figure 9 It is a graph showing the time variations of the first modulation signal V2a and the second modulation signal V2b respectively.

[0022] Figure 10 It is showing Figure 7 A graph showing an example of the spectrum of the arithmetic electric signal V4 obtained by subtracting the first modulation signal V2a and the second modulation signal V2b shown in using the arithmetic circuit 315.

[0023] Figure 11 It is a graph showing a configuration example of the measurement system 1c.

[0024] Figure 12 It is a top view of the heat flux sensor 2 with the magnetic field application unit 53 built in, observed from the z-axis direction.

[0025] Figure 13 It is a top view of the magnetic field application unit 53 built in the heat flux sensor 2, observed from the z-axis direction.

[0026] Figure 14 It is showing Figure 12 A cross-sectional view of the heat flux sensor 2 shown in, including the plane in the z-axis direction.

[0027] Figure 15 It is an activity diagram showing an example of signal processing performed by the measurement system 1c.

[0028] Figure 16 This is a diagram showing another example of the magnetic field application unit 53. Detailed implementation mode

[0029] Hereinafter, preferred implementation modes of the present disclosure will be described in detail with reference to the accompanying drawings. Note that in this specification and the accompanying drawings, for components having substantially the same functional configuration, repeated description is omitted by assigning the same reference numerals.

[0030] In addition, a program product for implementing the software that appears in this implementation mode can be provided as a computer-readable non-transitory storage medium (Non-Transitory Computer-Readable Medium), can also be provided so as to be downloadable from an external server, and can also be provided so that the function thereof is realized on a client terminal by starting the program product through an external computer (so-called cloud computing).

[0031] In addition, the "unit" in this implementation mode may include, for example, a combination of hardware resources implemented by a general circuit and software information processing that can be specifically realized by such hardware resources. In addition, although various information is processed in this implementation mode, this information is, for example, a numerical value having the physical meaning of a signal value representing voltage or current, or the high and low of a signal value that can be a bit set (Bit set) composed of 0 or 1, or is represented by quantum superposition (so-called qubit), and communication or calculation can be performed on a general circuit.

[0032] In addition, a general circuit is a circuit realized by at least appropriately combining a circuit, circuitry, a processor, a memory, etc. That is, it includes application specific integrated circuits (ASICs) for specific purposes, programmable logic devices (for example, simple programmable logic devices (SPLDs), complex programmable logic devices (CPLDs), and field programmable gate arrays (FPGAs)).

[0033] 1. Outline of this implementation mode

[0034] Conventional heat flux sensors are prone to interference from low-frequency noise due to their high impedance and cannot accurately measure. For example, in devices such as heat flux sensors based on the anomalous Nernst effect, signals corresponding to the magnetization of the sensor are output. Therefore, for example, if the magnetization direction or intensity of the sensor changes due to an interfering magnetic field (i.e., magnetic field noise), the sensitivity will change. As a result, in an environment with a large interfering magnetic field, the measurement accuracy will decrease. In addition, the influence caused by electrical noise is also likely to occur. Therefore, there is still room for improvement in the measurement accuracy of heat flux. Additionally, as a conventional method, using shielding can be considered, but the cost will increase and the structure is likely to become larger.

[0035] Therefore, in the devices, systems using such devices, and methods related thereto according to the present embodiment, for example, noise components and signal components are separated by performing electrical and / or magnetic chopping. Thereby, frequency separation of the noise components can be achieved, and thus the measurement accuracy can be improved.

[0036] The heat flux sensor (an example of a device) according to the present embodiment is preferably a heat flux sensor based on the thin-film type anomalous Nernst effect from the viewpoint of responsiveness. The element (thermoelectric conversion element) of the heat flux sensor (i.e., a thermoelectric conversion device) may be composed of a compound exhibiting the anomalous Nernst effect. This element can be composed of, for example, a topological ferromagnet or topological antiferromagnet called a Weyl semimetal, or can be composed of a ferrimagnet, or can also be a combination thereof. The topological ferromagnet can be an alloy of Co2TX such as Co2MnGa (X is any one of Si, Ge, Sn, Al, and Ga), or can be a metal with a composition formula of Fe3X (X is a stoichiometric or non-stoichiometric composition of a typical element or transition element such as Al or Ga) and other known topological ferromagnet alloys. In addition, the topological antiferromagnet can be a known topological antiferromagnet such as Mn3X (X is one or more elements selected from Sn, Ge, Ga, Pt, Ir, Rh or a compound thereof). The composition ratio of the alloy constituting the topological ferromagnet or topological antiferromagnet does not necessarily have to be only the above-mentioned stoichiometric composition ratio, as long as it is a substance having a partial stoichiometric structure, and the composition ratio is not particularly limited. The compound constituting the element can be composed of an alloy having a transition metal, and the alloy is a compound having a crystal structure with a Kagome lattice plane composed of a transition metal and can exhibit the anomalous Nernst effect. The ferrimagnet is not particularly limited as long as it can exhibit the anomalous Nernst effect. There is no particular limitation on the structure of the element, and a known structure can be used. In addition, the element according to the present embodiment can be provided by means such as sputtering, evaporation, MBE, electroplating, sintering, printing, and pasting. The heat flux sensor according to the present embodiment is not only a device for measuring heat, but can also be a device configured to detect light, chemical substances, etc. Hereinafter, for convenience of explanation, the thermoelectric conversion element is sometimes referred to as a thermoelectric conversion unit.

[0037] A chopper circuit is provided between the output section (the end of the element) of the heat flux sensor and the amplifier / AD conversion circuit. Thus, by shifting the noise frequency band and the sensor frequency band, electromagnetic field noise can be eliminated. Sampling is performed with different chopping phases, and signal processing is performed using, for example, differential processing, a low-pass filter, or a high-pass / band-pass filter. Thus, only the information of the signal can be obtained. Note that the signal processing itself can be analog or digital, and an amplifier can be added midway.

[0038] In addition, when a magnetic field noise (interference magnetic field) is applied to the heat flux sensor, since the magnetization of the element changes, the coefficient a that affects the signal output of the heat flux sensor changes. Thus, the heat flux value Q also changes.

[0039] Therefore, it can also be configured to provide a coil near the heat flux sensor (device) so that a magnetic field can be applied to the heat flux sensor from the outside. By measuring the heat flux in a state where an external magnetic field is applied, the influence of the interference magnetic field of the magnetic body can be suppressed. In this way, the sensitivity of the sensor is stabilized. That is, by applying a relatively large magnetic field Hb as an external magnetic field, magnetization M can be stably obtained, and high sensitivity can be maintained.

[0040] In addition, by changing the direction of the magnetic field applied by the coil, noise can be reduced using differential processing, a low-pass filter, or a high-pass / band-pass filter. Note that the signal processing itself can be analog or digital, and an amplifier can be added midway.

[0041] A modification example of the present embodiment will be described below. As Figure 5 shown, the coil may not be provided outside the sensor but may be stacked on the sensor. By making the magnetic field direction of the coil in the plane of the sensor, a stable magnetic field can be applied to the sensor. An insulating layer (adhesive layer) may be provided between the sensor and the coil.

[0042] In addition, by increasing the number of turns of the coil, a larger magnetic field can be generated with a small coil.

[0043] In addition, a heat sink may be provided below the sensor and the coil. Thus, the measurement accuracy of the heat quantity Q can be further improved.

[0044] Another modification example of the present embodiment will be described below. The coil provided outside can be an air-core coil. Thus, a strong magnetic field can be generated in the sensor. A soft magnetic body may be provided inside the air-core coil. The coil may be provided on one side or both sides of the sensor.

[0045] By inputting a periodic wave, particularly a sine wave, to an external coil, the external magnetic field also becomes an output based on this waveform. If this input signal, the output signal of the sensor, and a large external magnetic field Hb are added, the magnetic field can be stabilized and maintain high sensitivity. The signal processing itself can be implemented in an analog or digital manner, and it is also okay to add an amplifier midway. The applied magnetic field from the coil can be of an optimal size with excellent linearity. In addition, the circuit can also be of a heterodyne structure. Hereinafter, examples of various forms of the above-described embodiment will be described in detail.

[0046] 2. Regarding the measurement system according to the first embodiment

[0047] In this section, the measurement system 1a according to the first embodiment (hereinafter simply referred to as the measurement system 1a) will be described.

[0048] 2.1. Configuration example of the first embodiment

[0049] Figure 1 is a diagram showing a configuration example of the measurement system 1a. As Figure 1 shown, the measurement system 1a includes at least one heat flux sensor 2 and a signal processing system 3.

[0050] <Heat flux sensor 2>

[0051] The heat flux sensor 2 is arranged to perform heat exchange with a measurement object (not shown). The heat flux sensor 2 includes a substrate 21 as an insulating part, at least one (a plurality in this embodiment) thermoelectric conversion part 22, a wiring 23, and an output part 24.

[0052] The substrate 21 is configured to be in contact with the measurement object (not shown). The substrate 21 includes a connection surface 211 as the second surface and a measurement surface 212 as the first surface. The connection surface 211 is configured to be in contact with the measurement object. The measurement surface 212 is configured to be located at a position opposite to the connection surface 211 in the thickness direction of the substrate 21. Hereinafter, for convenience of explanation, the thickness direction of the substrate 21 may sometimes be referred to as the z-axis direction.

[0053] The thermoelectric conversion unit 22 is configured to convert a temperature gradient generated by heat exchange with a measurement object into an electric signal based on the anomalous Nernst effect. A plurality of thermoelectric conversion units 22 are arranged (for example, stacked) on the measurement surface 212 of the substrate 21, and are configured to perform heat exchange with the measurement object via the substrate 21. Thus, each thermoelectric conversion unit 22 is configured to generate a temperature gradient in the normal direction of the measurement surface 212 based on the heat flow flowing into the measurement surface 212. Each thermoelectric conversion unit 22 is configured to have spontaneous magnetization in a direction different from the temperature gradient, and thus is configured to generate an electromotive force in the in-plane direction due to the above temperature gradient. The normal direction of the measurement surface 212 coincides with, for example, the z-axis direction. The thermoelectric conversion unit 22 is formed in a thin film shape. In addition, the thermoelectric conversion unit 22 may include magnetic domains configured to be magnetized in the in-plane direction of the thin film. Note that the thermoelectric conversion unit 22 may also be formed in a bulk shape. The in-plane direction is perpendicular to the normal direction of the measurement surface 212. In the present embodiment, the in-plane direction is defined by the x-axis direction and the y-axis direction. The y-axis direction is the direction in which the thermoelectric conversion unit 22 extends, and the x-axis direction is defined to be perpendicular to the y-axis direction. In the present embodiment, the thermoelectric conversion unit 22 is configured to be magnetized in the x-axis direction, which is one of the in-plane directions.

[0054] The wiring 23 is configured to connect a plurality of thermoelectric conversion units 22 in series such that their polarities are consistent.

[0055] The output unit 24 is a terminal configured to output the sum value of the electromotive forces output from the entire plurality of thermoelectric conversion units 22. Note that the output unit 24 is not necessarily installed as an actual connection terminal, and may also be a virtual terminal connected to an external component. In the present embodiment, the heat flux sensor 2 includes a pair of output units 24, and outputs a total electromotive force V1, which is the sum value of the electromotive forces of the thermoelectric conversion units 22, from the pair of output units 24. In the present embodiment, the heat flux sensor 2 outputs the total electromotive force V1 output from the output unit 24 due to the heat flux accompanying the temperature gradient. Ideally, V1 = k × M × Q (where k is a proportionality constant, M is the magnetization of the thermoelectric conversion unit 22, and Q is the heat flux), but in reality, since a noise component N is superimposed, V1 = k × M × Q + N. Hereinafter, for the sake of convenience of explanation, the ideal V1 = k × M × Q is referred to as the true total electromotive force V1t.

[0056] <Signal processing system 3>

[0057] The signal processing system 3 is used to measure the system 1a and is configured to process the signal output from the measurement system 1a (the total electromotive force V1 in this embodiment). The signal processing system 3 includes at least one (two in this embodiment, which is the same number as the number of heat flux sensors 2) signal processing circuit 31 and a signal processing device 4. In this embodiment, each signal processing circuit 31 is respectively assigned to each of the plurality of heat flux sensors 2 and is configured to process the total electromotive force V1 output from each heat flux sensor 2.

[0058] Each signal processing circuit 31 includes a chopper circuit 311 as an electrical modulation unit, a switch controller 312, a filter circuit 313 as an extraction unit, and an amplification unit 314.

[0059] The chopper circuit 311 is configured to input the total electromotive force V1 as the electrical signal output from the thermoelectric conversion unit 22. The chopper circuit 311 is configured to introduce modulation including a predetermined modulation frequency fm into the input total electromotive force V1, thereby generating a modulation signal V2. The modulation frequency is a frequency outside the frequency band of the thermoelectric conversion unit 22. The so-called outside the frequency band of the thermoelectric conversion unit 22 means, for example, a frequency different from the main frequency components of the noise generated when the thermoelectric conversion unit 22 operates, such as electrical noise, magnetic noise, electromagnetic wave noise, etc. The chopper circuit 311 may include a switch capable of blocking the transmission of the electrical signal. The chopper circuit 311 is configured to switch the on and off of the switch based on the predetermined modulation frequency fm, thereby performing modulation. For example, the chopper circuit 311 outputs the total electromotive force V1 when the switch is in the on state and does not output the total electromotive force V1 when the switch is in the off state, and outputs, for example, zero voltage. In this way, the chopper circuit 311 can output a rectangular-wave modulation signal V2 in which the total electromotive force V1 and zero voltage are alternately switched over time by modulating the total electromotive force V1. According to this configuration, the modulation of the total electromotive force V1 can be achieved with a relatively simple configuration of the on and off of the switch.

[0060] The switch controller 312 is configured to output a signal for controlling the on or off of the switch of the chopper circuit 311 based on a preset duty ratio, frequency, etc. In this embodiment, the switch controller 312 is configured to receive the input of information such as the duty ratio and frequency required to control the switch state of the chopper circuit 311 and output a signal for controlling the switch state of the chopper circuit 311 based on the received information.

[0061] The filter circuit 313 is configured to extract the signal of the modulation frequency fm from the modulation signal V2. For example, the filter circuit 313 is configured to pass the component of the modulation frequency fm included in the modulation signal V2 and remove the main frequency components of the noise. The specific form of the filter circuit 313 can be appropriately set to a low-pass filter, a high-pass filter, a band-pass filter, etc. according to the main frequency components of the noise. According to this configuration, since the component of the modulation frequency fm in the total electromotive force V1 can be selectively extracted, the influence of noise in the measurement system 1 can be reduced, and the heat flow detection accuracy by the thermoelectric conversion unit 22 can be improved.

[0062] The amplifier unit 314 is configured to amplify the modulation signal V2 with reduced noise components via the filter circuit 313, and thus output the output signal V3. Note that the signal processing circuit 31 may also include a filter circuit configured to pass the component of the modulation frequency fm included in the output signal V3 output from the amplifier unit 314 and remove the main frequency components of the noise. In this case, the filter circuit 313 is not necessary.

[0063] The signal processing system 3 of the present embodiment is configured to perform modulation on the total electromotive force V1 from the first heat flow sensor 2a and the total electromotive force V1 from the second heat flow sensor 2b respectively. For example, the signal processing system 3 includes a signal processing circuit 31 for performing signal processing on the total electromotive force V1 from the first heat flow sensor 2a, and a signal processing circuit 31 for performing signal processing on the total electromotive force V1 from the second heat flow sensor 2b.

[0064] <Signal processing device 4>

[0065] The signal processing device 4 is a device for processing the output signal V3 output from the signal processing circuit 31. Figure 2 is a block diagram showing the hardware configuration of the signal processing device 4. The signal processing device 4 includes a communication unit 41, a storage unit 42, at least one processor 43 as an example of a control circuit, a display unit 44, and an input unit 45, and these constituent elements are electrically connected via a communication bus 40 inside the signal processing device 4.

[0066] The communication unit 41 is preferably a wired communication method, such as USB, IEEE1394, Thunderbolt (registered trademark), wired LAN network communication, etc., but may also include wireless LAN network communication, mobile communication such as 3G / LTE / 5G, Bluetooth (BLUETOOTH, registered trademark) communication, etc. as needed. That is, it is more preferably implemented as a collection of these multiple communication methods. That is, the signal processing device 4 can communicate various information with the outside via the communication unit 41 and the network.

[0067] The storage unit 42 stores various information defined by the above description. This can be implemented, for example, as a storage device such as a solid state drive (SSD) that stores various program products related to the signal processing device 4 executed by the processor 43, or as a memory such as a random access memory (RAM) that stores temporary information (parameters, arrays, etc.) required for program operations. The storage unit 42 stores various programs or variables related to the signal processing device 4 executed by the processor 43.

[0068] The processor 43 performs processing and control of the overall operation related to the signal processing device 4. The processor 43 is, for example, a central processing unit (CPU) not shown. The processor 43 realizes various functions related to the signal processing device 4 by reading a predetermined program stored in the storage unit 42. That is, the information processing of the software stored in the storage unit 42 is specifically realized by the processor 43 as a hardware example, and thus can be executed as each functional unit included in the processor 43. These will be further described in detail in the next section. Note that the processor 43 is not limited to a single one, and can also be implemented as having multiple processors 43 for each function. In addition, it can also be a combination of these.

[0069] The display unit 44 can be included in the housing of the signal processing device 4 or can be external. The display unit 44 displays a screen of a graphical user interface (GUI) operable by the user. This is preferably implemented using display devices such as a CRT monitor, a liquid crystal display, an organic EL display, and a plasma display, respectively, according to the type of the signal processing device 4.

[0070] The input unit 45 is configured to be able to receive input from the user. The input unit 45 can be included in the housing of the signal processing device 4 or can be external. For example, the input unit 45 can be integrated with the display unit 44 as a touch panel. If it is a touch panel, the user can input click operations, swipe operations, etc. Of course, instead of the touch panel, a switch button, a mouse, a QWERTY keyboard, a voice recognition device, a gesture measurement device, a gaze measurement device, a biological signal measurement device, a camera device, etc. can also be used. That is, the input unit 45 receives the operation input performed by the user. In response, the input unit 45 transmits a signal corresponding to the operation input to the processor 43 via the communication bus 40. The processor 43 performs predetermined control or arithmetic as needed.

[0071] The processor 43 is configured to be able to obtain information from the signal processing device 4 or other devices. The processor 43 is configured to obtain various information by reading various information stored in a storage area that is at least a part of the storage unit 42 and writing the read information into a working area that is at least a part of the storage unit 42. The storage area is, for example, an area implemented as a storage device such as an SSD in the storage unit 42. The working area is, for example, an area implemented as a memory such as a RAM. Note that the obtaining by the processor 43 includes obtaining the output results of the respective functional units included in the processor 43.

[0072] As an extraction unit, the processor 43 is configured to extract a specific frequency component from the obtained information. For example, the processor 43 can convert a signal included in the obtained information into a frequency spectrum by Fourier transform or the like, and selectively extract the signal intensity of a specific frequency from the frequency spectrum.

[0073] The processor 43 is configured to be able to display various information. This information can be presented to the user via the display unit 44 of the signal processing device 4 or other devices. In this case, for example, the processor 43 controls so that the display unit 44 of the signal processing device 4 displays visual information including a screen, a still image, or a moving image, an icon, a message, etc. The processor 43 can also generate only rendering information for displaying visual information on the display unit 44.

[0074] 2.2. Regarding the signal processing flow related to the measurement system 1a

[0075] Figure 3 It is an activity diagram showing an example of the signal processing executed in the measurement system 1a. Note that this signal processing can include any exception handling not shown. The exception handling can include interruption of this signal processing, omission of each process, etc. The selection or input performed in this signal processing can be based on the user's operation or can be automatically performed without depending on the user's operation.

[0076] [Activity A1]

[0077] First, in activity A1, the processor 43 obtains the driving conditions of the chopper circuit 311. The driving conditions are conditions related to parameters for determining the driving form of the switching elements included in the chopper circuit 311. For example, they can include the modulation frequency fm that specifies the main frequency component of the modulation introduced into the total electromotive force V1 output from the heat flow sensor 2, the duty ratio, etc. The driving conditions can be input by the user, can be predetermined, or can be automatically determined based on the spectral analysis of the input total electromotive force V1. The modulation frequency fm is preferably a frequency different from the frequency band of the noise component superimposed on the total electromotive force V1.

[0078] The frequency band of the noise component is, for example, a frequency band composed of the frequency band of the noise caused by the inherent characteristics of the thermoelectric conversion unit 22, the main frequency bands included in the noise inevitably introduced into the thermoelectric conversion unit 22, etc., and the main frequency components of the noise that may be superimposed on the total electromotive force V1 of the thermoelectric conversion unit 22. As such noise, for example, there can be cited electromagnetic noise (e.g., electrical noise or electromagnetic wave noise) superimposed in the circuit for transmitting the total electromotive force V1 from the heat flow sensor 2 to the signal processing system 3, electromagnetic noise applied to elements such as the thermoelectric conversion unit 22, etc.

[0079] [Activity A2]

[0080] Next, in Activity A2, the processor 43 sends an instruction to the switch controller 312 based on the acquired driving conditions. In the present embodiment, instructions are sent to the respective switch controllers 312 of the plurality of signal processing circuits 31.

[0081] [Activity A3]

[0082] Next, in Activity A3, the switch controller 312 sends a signal for controlling the switch of the chopper circuit 311 to the chopper circuit 311 according to the driving conditions sent from the processor 43, drives the chopper circuit 311, and introduces modulation to the total electromotive force V1. As a result, the on and off states of the switch of the chopper circuit 311 are switched at a period including the modulation frequency fm as the main frequency component. In the present embodiment, when the switch of the chopper circuit 311 is in the on state, the output modulation signal V2 from the chopper circuit 311 becomes zero, and when the switch of the chopper circuit 311 is in the off state, the output modulation signal V2 from the chopper circuit 311 becomes a finite value (e.g., the total electromotive force V1). Thus, modulation in which zero and the total electromotive force V1 are alternately switched at a predetermined modulation frequency fm is introduced to the total electromotive force V1. In this way, the chopper circuit 311 outputs a modulation signal V2 to which modulation has been introduced to the total electromotive force V1.

[0083] In other words, as a modulation unit, the chopper circuit 311 is configured to introduce modulation including a predetermined modulation frequency fm into the total electromotive force V1, which is an electric signal output from the thermoelectric conversion unit 22. Note that the processor 43 may also directly introduce modulation into the total electromotive force V1 without going through the switch controller 312 and the chopper circuit 311. Further, as described above, as an electric modulation unit, the chopper circuit 311 is configured to change the electric characteristics (in this embodiment, the resistance characteristics that define the transfer characteristics of the total electromotive force V1) of the circuit that transfers the total electromotive force V1, which is an electric signal output from the thermoelectric conversion unit 22, to the filter circuit 313, which is an extraction unit, in synchronization with the modulation frequency fm. With this configuration, it is possible to suppress an increase in the inherent noise induced in the thermoelectric conversion unit 22 while extracting a signal that is not easily affected by noise. This circuit includes a switch that can block the transfer of the total electromotive force V1, which is an electric signal. Then, the processor 43 modulates the total electromotive force V1 by switching the chopper circuit 311 between on and off based on the modulation frequency fm. With this configuration, it is possible to simplify the mechanism for modulating the total electromotive force V1. Note that synchronization means that two signals are linked with the same period, regardless of the presence or absence of a phase difference. The processor 43 may also be configured to function as a modulation unit (specifically, an electric modulation unit). In other words, the modulation unit may be installed as a control circuit constituted by the processor 43.

[0084] [Activity A4]

[0085] Next, in Activity A4, the filter circuit 313 extracts a signal having a frequency that is amplified by the modulation from the modulation signal V2 output from the chopper circuit 311. For example, the filter circuit 313 extracts a signal having a modulation frequency fm. As a result, the filter circuit 313 outputs an output signal V3. Note that this extraction may also be performed by a digital circuit installed in the processor 43. In other words, the processor 43 may function as an extraction unit instead of or in addition to the filter circuit 313. In this embodiment, the output signal V3 extracted by the filter circuit 313 is appropriately amplified by the amplifier unit 314 and then sent to the signal processing device 4.

[0086] [Activity A5]

[0087] Next, in activity A5, the processor 43 detects the heat flux in the z-axis direction flowing through the heat flux sensor 2 (in other words, the temperature gradient in the z-axis direction generated in the heat flux sensor 2) based on the output signal V3. For example, the processor 43 calculates the heat flux from the output signal V3 based on a predetermined relational expression between the output signal V3 and the heat flux (such as a proportional coefficient or an offset). The processor 43 outputs the result obtained through this calculation as the detection result of the heat flux. The processor 43 can utilize the detected heat flux-related information in various forms such as presenting it to the user and controlling the device. Then, the signal processing system 3 ends this signal processing.

[0088] According to the signal processing described above, since the component of the modulation frequency fm in the total electromotive force V1 can be selectively extracted, the influence of the noise that the total electromotive force V1 in the measurement system 1 may contain can be reduced, and the heat flux detection accuracy by the thermoelectric conversion unit 22 can be improved.

[0089] 2.3. State transition of the electrical signal for signal processing

[0090] In this section, reference will be made to Figures 4 to 6 to describe the state transition of the electrical signal caused by the signal processing described in the previous section.

[0091] Figure 4 is a diagram showing the time variation of the total electromotive force V1 output from one heat flux sensor 2. As Figure 4 shown, the total electromotive force V1 can contain the true total electromotive force V1t and the noise component N as described above. Here, for the sake of convenience of explanation, the case where the temperature gradient generated in the heat flux sensor 2 does not change with time and the true total electromotive force V1t is constant will be described. The noise component N is, for example, a voltage caused by electromagnetic noise applied to the thermoelectric conversion unit 22 or electromagnetic noise generated in the circuit from the heat flux sensor 2 to the signal processing system 3. The total electromotive force V1 is transmitted to the signal processing system 3 in a state where the noise component N is superimposed. In this embodiment, it is assumed that the frequency band of the noise component N is lower than the modulation frequency fm. In other words, it is assumed that the main period of the noise component N is longer than the period T defined by the modulation frequency fm.

[0092] Figure 5 is a diagram showing the time variation of the modulation signal V2. Figure 6 is a diagram showing Figure 5 an example of the spectrum of the modulation signal V2 shown in Figure 5 shown. As Figure 6As shown, the spectrum of the total electromotive force V1 has a peak at the frequency caused by the noise component N, i.e., the noise frequency fN, and a frequency peak at the modulation frequency fm caused by the introduced modulation. By using the filter circuit 313 whose cut-off frequency fc is between the noise frequency fN and the modulation frequency fm, the filter circuit 313 can cut off the peak component of the noise frequency fN included in the modulation signal V2 and selectively pass through the modulation frequency fm included in the modulation signal V2. Then, the signal processing system 3 amplifies the modulation signal V2 with the reduced noise component N, and can obtain an output signal V3 with lower noise than before.

[0093] 3. Regarding the measurement system according to the second embodiment

[0094] In this section, the measurement system 1b according to the second embodiment (hereinafter, simply referred to as the measurement system 1b) will be described. Note that in the description of the measurement system 1b, for the parts common to the above-mentioned measurement system 1a, the description may sometimes be omitted by assigning the same reference numerals.

[0095] Figure 7 is a diagram showing a configuration example of the measurement system 1b. As Figure 7 shown, the measurement system 1b includes a plurality of heat flux sensors 2 and a signal processing system 3.

[0096] In the present embodiment, the plurality of heat flux sensors 2 include a first heat flux sensor 2a and a second heat flux sensor 2b. The first heat flux sensor 2a and the second heat flux sensor 2b are configured to generate substantially the same temperature gradient with each other. The first heat flux sensor 2a and the second heat flux sensor 2b are configured to output total electromotive forces V1 with opposite signs with respect to the same temperature gradient. Specifically, the thermoelectric conversion units 22 of the first heat flux sensor 2a and the second heat flux sensor 2b are configured to have opposite polarities (for example, the direction of magnetization M). Therefore, for a certain heat movement amount Q and the same noise component N, as described above, the total electromotive force V1 output by the first heat flux sensor 2a is k×M×Q + N, while the second heat flux sensor 2b outputs -k×M×Q + N. Note that the specific configurations of the first heat flux sensor 2a and the second heat flux sensor 2b are the same as those of the heat flux sensor 2 included in the measurement system 1a except for the above-mentioned different polarities. Hereinafter, for the sake of convenience of explanation, the total electromotive force V1 output from the first heat flux sensor 2a is referred to as the first total electromotive force V1a, and the total electromotive force V1 output from the second heat flux sensor 2b is referred to as the second total electromotive force V1b.

[0097] The signal processing system 3 of the measurement system 1b includes a signal processing circuit 31 and a signal processing device 4 in the same manner as the signal processing system 3 of the measurement system 1a. Since the specific hardware configuration of the signal processing device 4 of the measurement system 1b is the same as that of the signal processing device 4 of the measurement system 1a, the description thereof is omitted.

[0098] The signal processing circuit 31 of the measurement system 1b is different from the signal processing circuit 31 of the measurement system 1a in that it further includes an arithmetic circuit 315 in addition to the chopper circuit 311, the switch controller 312, the filter circuit 313, and the amplifier unit 314.

[0099] The filter circuit 313 of the measurement system 1b is configured to introduce modulation based on the modulation frequency fm into the first total electromotive force V1a and the second total electromotive force V1b, respectively. Thus, the filter circuit 313 can generate a first modulation signal V2a, which is a modulation signal V2 obtained by introducing modulation into the first total electromotive force V1a, and a second modulation signal V2b, which is a modulation signal V2 obtained by introducing modulation into the second total electromotive force V2b.

[0100] The arithmetic circuit 315 of the measurement system 1b is configured to perform arithmetic operations on the first total electromotive force V1a and the second total electromotive force V1b to reduce the common noise component N included in the first total electromotive force V1a and the second total electromotive force V1b, thereby generating an arithmetic electric signal V4. For example, the arithmetic circuit 315 may be a subtraction circuit that outputs an electric signal corresponding to the difference between the first modulation signal V2a and the second modulation signal V2b as the arithmetic electric signal V4. In addition, the arithmetic circuit 315 may also be an addition circuit that outputs an electric signal corresponding to the sum of the first modulation signal V2a and the second modulation signal V2b as the arithmetic electric signal V4. Note that the arithmetic electric signal V4 is an electric signal into which modulation has been introduced and is an example of the modulation signal V2.

[0101] The filter circuit 313 extracts a signal of a frequency amplified by modulation from the arithmetic electric signal V4 output from the arithmetic circuit. Thus, the filter circuit 313 outputs an output signal V3. The filter circuit 313 of the measurement system 1b may extract a signal of the modulation frequency fm in the same manner as the filter circuit 313 of the measurement system 1a, or may extract a signal amplified by performing arithmetic operations on the modulation signal V2 by the arithmetic circuit 315. Note that the signal amplified by modulation does not include a signal that may be amplified (added) by arithmetic operations regardless of the presence or absence of modulation, such as the noise component N.

[0102] The processor 43 of the signal processing device 4 can obtain information about the heat flux by performing the signal processing of the measurement system 1a on the output signal V3.

[0103] At this time, the processor 43 can, for example, set drive conditions for the chopper circuits 311 of the plurality of signal processing circuits 31 in activity A1. The processor 43 preferably sets the drive conditions such that the chopper circuits 311 of the signal processing circuits 31 for processing the total electromotive force V1 from the first heat flux sensor 2a and the chopper circuits 311 of the signal processing circuits 31 for processing the total electromotive force V1 from the second heat flux sensor 2b modulate their respective total electromotive forces V1 based on the same modulation frequency fm. Thereby, by performing operations such as mutual subtraction on the respective modulation frequency fm components of the plurality of total electromotive forces V1, noise components can be more appropriately removed.

[0104] Next, with reference to Figures 8 to 10 An example of the state change of the electrical signal caused by signal processing in the measurement system 1b will be described. Here, for ease of explanation, the following case will be described: The arithmetic circuit 315 is a subtraction circuit, and the first total electromotive force V1a and the second total electromotive force V1b are respectively subjected to modulation such that a 180-degree phase difference appears between the first modulation signal V2a and the second modulation signal V2b.

[0105] Figure 8 It is a graph showing the time changes of the first total electromotive force V1a and the second total electromotive force V1b. Here, for ease of explanation, it is assumed that the true total electromotive force V1t included in the first total electromotive force V1a and the second total electromotive force V1b is constant. As Figure 7 shown, the true total electromotive force V1t output from the first heat flux sensor 2a and the true total electromotive force V1t output from the second heat flux sensor 2b have opposite signs. In addition, the first total electromotive force V1a and the second total electromotive force V1b are such that a common noise component N is superimposed on this true total electromotive force V1t.

[0106] Figure 9 It is a graph showing the time changes of the first modulation signal V2a and the second modulation signal V2b respectively. Note that the content regarding the first modulation signal V2a is the same as that Figure 6 described above, so the description is omitted. In the present embodiment, the total electromotive forces V1a and V1b are respectively input from the two heat flux sensors 2a and 2b, and are respectively chopped by the chopper circuit 311 with different phases (specifically, inverted phases). As a result, the second modulation signal V2b is modulated into a periodicity with the same modulation frequency fm in the same manner as the first modulation signal V2a. In addition, the sign of the signal intensity (i.e., voltage) of the second modulation signal V2b with respect to the first modulation signal V2a is reversed, and the phase is reversed. Note that when taking the difference between the first modulation signal V2a and the second modulation signal V2b, the arithmetic electrical signal is almost constant, having a peak of a frequency component with a frequency almost of 0, or a peak of a frequency component corresponding to the modulation frequency fm.

[0107] Figure 10 It means Figure 7 FIG. 3 is a diagram showing an example of a spectrum of an operational electrical signal V4 obtained by performing a subtraction operation on the first modulation signal V2a and the second modulation signal V2b using the operation circuit 315. Figure 10 As shown, the calculated electrical signal V4 has a peak in a frequency band where the frequency is almost zero. Therefore, by using a high-pass filter or the like as the filter circuit 313, the signal processing circuit 31 can reduce frequency components above the cutoff frequency fc and transmit frequency components below the cutoff frequency fc, thereby reducing the noise component N included in the noise frequency fN.

[0108] Note that when the operation circuit 315 is used as an adding circuit, the operation electrical signal V4 has the same Figure 6 In this case, by using the adder circuit, the modulation frequency fm component of the computational electrical signal becomes twice that of the modulation signal V2, achieving a signal amplification factor greater than that of the noise component N.

[0109] Signal processing circuit 31 can also be implemented as a digital circuit by signal processing device 4. For example, signal processing device 4 can directly acquire the modulated signal V2 modulated by chopper circuit 311 and perform a Fourier transform on it to extract the frequency components related to the modulation frequency fm. Furthermore, signal processing device 4 can independently perform the aforementioned signal processing on the modulated signal V2 caused by the total electromotive force V1 output by each of the multiple heat flow sensors 2, and output more reliable heat flow-related information by appropriately sampling the heat flow-related information obtained from each sensor.

[0110] 4. Regarding the Measurement System According to the Third Embodiment

[0111] This section describes a measurement system 1c according to a third embodiment (hereinafter referred to as measurement system 1c). Note that in the description of measurement system 1c, parts common to the aforementioned measurement system 1a or measurement system 1b may be omitted by assigning the same reference numerals.

[0112] 4.1. Example of the configuration of the measurement system 1c

[0113] Figure 11 1c is a diagram showing an example of the structure of the measurement system 1c. Figure 11 As shown, the measurement system 1c includes a heat flow sensor 2 and a signal processing system 3. The heat flow sensor 2 is the same as the heat flow sensor 2 of the measurement system 1a.

[0114] Instead of (or in addition to) the signal processing circuit 31, the signal processing system 3 of the measurement system 1c includes a signal processing circuit 5. The signal processing circuit 5 includes an oscillator 51, a magnet controller 52, a magnetic field application unit 53, an amplifier unit 54, and a lock-in detector 55 as an extraction unit. In addition, similar to the measurement systems 1a and 1b, the signal processing system 3 of the measurement system 1c includes a signal processing device 4. The hardware configuration of the signal processing device 4 is the same as described above.

[0115] The oscillator 51 is configured to output a signal with a modulation frequency fm. For example, the oscillator 51 generates a continuous periodic signal (e.g., a sine wave signal) oscillating at the modulation frequency fm. Note that the oscillator 51 may be provided outside the signal processing circuit 5 or even outside the signal processing system 3. In addition, the oscillation frequency of the oscillator 51 can be configured to be controllable by the signal processing device 4. With this configuration, by setting an appropriate modulation frequency fm according to the frequency band of the noise, more types of noise can be reduced.

[0116] The magnet controller 52 is configured to generate an input signal for driving the magnetic field application unit 53 described later based on the signal from the oscillator 51. The driving form of the magnet controller 52 can be controlled by the signal processing device 4. For example, the magnet controller 52 can be controlled by the signal processing device 4 to determine whether to output the input signal.

[0117] The magnetic field application unit 53 is configured to apply an external magnetic field H to the heat flux sensor 2 (specifically, the thermoelectric conversion unit 22). For example, the magnetic field application unit 53 applies the external magnetic field H in a form that can reverse the magnetization direction of the magnetic domains of the thermoelectric conversion unit 22. In other words, the magnetic field application unit 53 can be configured to apply an external magnetic field to the thermoelectric conversion unit 22 to reverse the sign of the component of the thermoelectric tensor of the thermoelectric conversion unit 22 based on the anomalous Nernst effect using the external magnetic field H. With this configuration, since the component of the thermoelectric tensor is reversed by the external magnetic field H, the signal intensity in the modulation frequency fm band of the electrical signal (total electromotive force V1) output from the heat flux sensor 2 can be amplified. For example, the magnetic field application unit 53 can be arranged relative to the thermoelectric conversion unit 22 to inductively apply the external magnetic field H in the in-plane direction, i.e., the x-axis direction, to the thermoelectric conversion unit. With this configuration, since it is easy to apply modulation to the magnetic domains by inducing a small in-plane magnetic field in the thin film, the signal intensity in the modulation band can be further amplified. In the present embodiment, the magnetic field application unit 53 is configured to apply the external magnetic field H in the x-axis direction, which is the magnetization direction of the magnetic domains of the thermoelectric conversion unit 22.

[0118] In addition, the magnetic field application unit 53 is configured to indirectly obtain a signal from the oscillator 51 via the magnet controller 52, and apply the external magnetic field H based on the input signal output from the magnet controller 52. Thus, the magnetic field application unit 53 is configured to apply an external magnetic field H including the modulation frequency fm to the thermoelectric conversion unit. With this configuration, since interference can be introduced into the thermoelectric conversion unit non-contactingly, the possibility of superimposing contact-type noise such as contact resistance on the electric signal can be reduced. More specifically, as the magnetic field application unit 53, any configuration such as a permanent magnet, an electromagnet, or a coil that can electrically or mechanically control the polarity of the external magnetic field H can be adopted.

[0119] The amplifier unit 54 is configured to amplify the signal output from the output unit 24. The specific configuration of the amplifier unit 54 is the same as that of the amplifier unit 314.

[0120] The lock-in detector 55 is configured to obtain the electric signal output from the heat flux sensor 2 and amplified by the amplifier unit 54, and extract the signal component of the modulation frequency fm from this electric signal by a lock-in method based on the signal from the oscillator 51. The extracted signal is sent to the signal processing device 4, and the signal processing device 4 outputs information about the heat flux based on this signal.

[0121] The magnetic field application unit 53 applies an external magnetic field H that oscillates periodically according to the modulation frequency fm to the heat flux sensor 2, so that the thermoelectric tensor of the thermoelectric conversion unit 22 is modulated at a period corresponding to the modulation frequency fm. As a result, the thermoelectromotive force itself of the thermoelectric conversion unit 22 with respect to the heat flux is modulated at a period corresponding to the modulation frequency fm, and the total electromotive force V1 itself is output as a modulation signal V2 into which modulation by the external magnetic field H is introduced. The output modulation signal V2 is amplified by the amplifier unit 314. In this way, the lock-in detector 55 is configured to extract the signal component of the modulation frequency fm from the modulation signal V2 by a lock-in method based on the signal from the oscillator 51. With this configuration, the synchronization accuracy of the signal can be improved, and the noise component can be further reduced.

[0122] The signal processing circuit 5 may further include a filter circuit 56. The filter circuit 56 is configured to selectively pass the components in the frequency band of the modulation frequency fm in the output signal V3 extracted from the lock-in detector 55. The filter circuit 56 can be appropriately designed as a low-pass filter, a high-pass filter, a band-pass filter, etc. according to the relationship between the modulation frequency fm and the frequency of the noise component N.

[0123] 4.2. Examples of the magnetic field application unit

[0124] In this section, examples of the magnetic field application unit 53 included in the measurement system 1c described in the previous section will be described. The magnetic field application unit 53 in the present embodiment is built in the heat flux sensor 2. Figure 12It is a top view of the heat flux sensor 2 with the magnetic field applying unit 53 built therein, observed from the z-axis direction. Figure 13 It is a top view of the magnetic field applying unit 53 built in the heat flux sensor 2, observed from the z-axis direction. Figure 14 It shows Figure 12 A cross-sectional view of the heat flux sensor 2 shown, including the plane containing the z-axis direction.

[0125] As Figures 12 to 14 shown, the magnetic field applying unit 53 is disposed on the connection surface 211 of the substrate 21. Since the substrate 21 is made of an insulator, the magnetic field applying unit 53 is electrically insulated from the thermoelectric conversion unit 22 disposed on the measurement surface 212. The magnetic field applying unit 53 of the present embodiment is formed as a laminate laminated on the connection surface 211. As Figure 13 shown, the magnetic field applying unit 53 includes a first coil 531 as a first magnetic field generating element and a second coil 532 as a second magnetic field generating element. The first coil 531 and the second coil 532 are respectively mounted on the connection surface 211 as coil patterns laminated in a square spiral shape along the z-axis direction. The first coil 531 and the second coil 532 are configured to apply a magnetic field in the z-axis direction by respectively passing currents therethrough. They are arranged along the x-axis direction, which is the magnetization direction of the thermoelectric conversion unit 22.

[0126] Here, when the polarities of the first coil 531 and the second coil 532 are opposite, the magnetic force lines extending from the N pole of the first coil 531 are directed toward the S pole of the second coil 532, and the magnetic force lines generated from the N pole of the second coil 532 are directed toward the N pole of the first coil 531. As a result, an annular external magnetic field H centered on the y-axis direction is formed. Thereby, at least a part of the external magnetic field H is induced with respect to the thermoelectric conversion unit 22 along the in-plane direction of the thin-film thermoelectric conversion unit 22, that is, the x-axis direction. Such a positional relationship of the first coil 531 and the second coil 532 is defined, and their polarities are set accordingly, which is an example of generating a magnetic field by an input signal having a phase difference corresponding to the positional relationship between the first coil 531 and the second coil 532. According to this configuration, a more compact signal processing system integrated with the thermoelectric conversion unit 22 can be realized. Note that the first coil 531 and the second coil 532 can be configured to have opposite chiralities. In this case, the first coil 531 and the second coil 532 can be connected in series. According to this configuration, since the current flowing through the first coil 531 is transmitted to the second coil 532, the polarities of the first coil 531 and the second coil 532 can be reversed, so that the control of the first coil 531 and the second coil 532 can be simplified.

[0127] In addition, the magnetic field application unit 53 may be configured such that when viewed from above the substrate 21 in the z-axis direction, its outer edge surrounds the connection surface 211. With this configuration, it becomes easier to apply an external magnetic field H to the entire thermoelectric conversion unit 22 disposed on the measurement surface 212. Further, the first coil 531 and the second coil 532 may be arranged at intervals in the x-axis direction. With this configuration, it is possible to easily apply an external magnetic field H in the y-axis direction to the thermoelectric conversion unit 22.

[0128] As Figure 14 shown, in addition to the substrate 21, the thermoelectric conversion unit 22, the wiring 23, and the output unit 24, the heat flux sensor 2 may further include an insulating layer 25 and a heat sink 26. The insulating layer 25 is an electrical insulator laminated on the connection surface 211 of the substrate 21 via the magnetic field application unit 53. The insulating layer 25 preferably has thermal conductivity. The heat sink 26 is laminated on the connection surface 211 via the insulating layer 25. The heat sink 26 is connected to a heat bath (not shown) and is configured to have a temperature within a predetermined range. The temperature of the heat sink 26 is transmitted to the measurement surface 212 via the insulating layer 25, the magnetic field application unit 53, and the substrate 21. Thus, the region of the thermoelectric conversion unit 22 in contact with the measurement surface 212 is almost equal to the temperature of the heat sink 26 in a steady state. In this way, since the temperature that defines the temperature gradient in the z-axis direction of the thermoelectric conversion unit 22 is stable, it is easy to evaluate the temperature near the thermoelectric conversion unit 22 from the temperature gradient of the thermoelectric conversion unit 22 and the heat flux flowing through the thermoelectric conversion unit 22. Note that the heat sink 26 is not limited to the case of the measurement system 1c, and can be similarly applied to the above-described measurement systems 1a and 1b.

[0129] 4.3. Example of signal processing performed by the measurement system 1c

[0130] In this section, an example of the signal processing performed by the measurement system 1c described in Sections 4.1. and 4.2. will be described. Figure 15 is an activity diagram showing an example of the signal processing performed by the measurement system 1c.

[0131] [Activity A11]

[0132] First, in Activity A11, the processor 43 acquires the drive conditions of the coils 531 and 532 included in the magnetic field application unit 53 (hereinafter, for convenience of explanation, referred to as coil drive conditions). The coil drive conditions may include any information regarding the parameters that define the external magnetic field H, such as the amplitude, direction, modulation frequency fm, etc. of the external magnetic field H. The coil drive conditions may be conditions input by the user through the input unit 45, or may be conditions automatically set by the processor 43 or the like.

[0133] [Activity A12]

[0134] Next, in activity A12, the processor 43 sends instructions to the oscillator 51 and the magnet controller 52 based on the acquired coil driving conditions. Thereby, the oscillator 51 generates a periodic signal oscillating at the modulation frequency fm included in the coil driving conditions. The magnet controller 52 determines the parameters of the input signals flowing to the first coil 531 and the second coil 532 based on the periodic signal generated in the oscillator 51 and the instructions sent from the processor 43, and outputs an alternating current as the input signal to the first coil 531 and the second coil 532 respectively based on the determined parameters. Such parameters may include, for example, the amplitude of the alternating current output to the first coil 531 and the second coil 532 (in other words, the amplitude of the external magnetic field H), waveform, frequency (modulation frequency fm), the phase difference between the current flowing through the first coil 531 and the current flowing through the second coil 532, etc. In the present embodiment, the magnet controller 52 outputs an alternating current with a sine wave waveform of the modulation frequency fm synchronized with the periodic signal of the oscillator 51 as the input signal.

[0135] [Activity A13]

[0136] Next, in activity A13, the magnetic field application unit 53 applies an external magnetic field H to the heat flux sensor 2 based on the input signal output from the magnet controller 52. Thereby, magnetic modulation of the modulation frequency fm is introduced into each thermoelectric conversion unit 22 of the heat flux sensor 2. In other words, when the processor 43 executes the magnetic field modulation step, the external magnetic field including the modulation frequency can be applied to the thermoelectric conversion unit 22 using the magnetic field application unit 53, thereby introducing modulation. According to this configuration, since interference can be introduced into the thermoelectric conversion unit 22 non - contactlessly, the possibility of superimposing contact - type noises such as contact resistance on the electrical signal can be reduced. The processor 43 can use the magnetic field application unit 53 to apply an external magnetic field H having an amplitude capable of reversing the magnetization direction of the magnetic domains of the thermoelectric conversion unit 22. In other words, the processor 43 can use the magnetic field application unit 53 to apply an external magnetic field H having an amplitude higher than the coercive force of the thermoelectric conversion unit 22. Thereby, the sign of the component based on the anomalous Nernst effect in the thermoelectric tensor of the thermoelectric conversion unit 22 can be reversed. In other words, the processor 43 can control the magnetic field application unit 53 to reverse the sign of the component based on the anomalous Nernst effect in the thermoelectric tensor of the thermoelectric conversion unit 22 by using the external magnetic field H, thereby introducing modulation. According to this configuration, since the component of the thermoelectric tensor is reversed by the external magnetic field H, the signal intensity in the modulation frequency fm band of the electrical signal can be amplified. In addition, the processor 43 can use the magnetic field application unit 53 to induce an external magnetic field H in the in - plane direction (for example, the x - axis direction) of the thermoelectric conversion unit 22, thereby introducing modulation. According to this configuration, since modulation can be easily applied to the magnetic domains by inducing a small in - plane magnetic field in the thin film, the signal intensity in the modulation frequency fm band can be further amplified.

[0137] The heat flux sensor 2 generates a total electromotive force V1 based on the heat flux in the z-axis direction. Here, each thermoelectric conversion unit 22 generates an electromotive force based on the heat flux in the z-axis direction while being modulated by the modulation frequency fm introduced by the external magnetic field H. Thus, modulation is directly introduced into the electromotive force itself output from the thermoelectric conversion unit 22. Therefore, the heat flux sensor 2 outputs a modulation signal V2 obtained by modulating the total electromotive force V1 from the output unit 24. The output of the output unit 24 is amplified by the amplifier unit 54 and then transmitted to the lock-in detector 55.

[0138] [Activity A14]

[0139] Next, in activity A14, the lock-in detector 55 acquires the modulation signal V2 output from the heat flux sensor 2 (specifically, the modulation signal V2 further amplified by the amplifier unit 54) and the periodic signal output from the oscillator 51.

[0140] [Activity A15]

[0141] Then, in activity A15, the lock-in detector 55 extracts the signal of the modulation frequency fm from the acquired modulation signal V2 by a lock-in method based on the signal from the oscillator. With this configuration, the synchronization accuracy of the signal can be improved and the noise component can be further reduced. The lock-in detector 55 outputs the extracted signal to the signal processing device 4 as the output signal V3 via the filter circuit 56. Note that the extraction of the signal by the lock-in method can also be performed by the processor 43. In other words, the processor 43 can function as an extraction unit.

[0142] [Activity A16]

[0143] The processor 43 acquires the output signal V3 output from the lock-in detector 55 and calculates information about the heat flux flowing through the heat flux sensor 2 based on the output signal V3. The specific form of this process is the same as that of the process in activity A5. Then, while repeating this signal processing, the signal processing system 3 ends this signal processing according to the user's operation.

[0144] [Other]

[0145] The forms of the above-described measurement systems 1a, 1b, 1c and the signal processing system 3 are only examples and are not limited thereto. The above-described measurement systems 1a, 1b, 1c can be appropriately combined within a range where there is no technical contradiction with each other. In addition, the above-described measurement systems 1a, 1b, 1c can also be modified as follows.

[0146] In the measurement system 1c, the magnetic field application unit 53 can also be installed as a component separate from the heat flux sensor 2. Figure 16 is a diagram showing another example of the magnetic field application unit 53. As Figure 16As shown, the first coil 531 and the second coil 532 can be arranged at positions spaced apart from the heat flux sensor 2 in the x-axis direction and are configured to have polarities in the x-axis direction. In addition, the number of coils as magnetic field applying elements included in the magnetic field applying unit 53 is arbitrary and can be multiple or single.

[0147] In the measurement system 1c, the positional relationship between the first coil 531 and the second coil 532 is not limited to being arranged side by side in the x-axis direction and can be arbitrary. For example, the first coil 531 can be arranged at a position away from one of the thermoelectric conversion units 22 along the x-axis direction, and the second coil 532 can be arranged at a position away from one of the thermoelectric conversion units 22 along the y-axis direction. In this case, by configuring the polarities of the first coil 531 and the second coil 532 to reverse with a phase difference of 90 degrees, an external magnetic field H in the x-axis direction can be applied to at least a part of the thermoelectric conversion unit 22. In addition, the number of magnetic field applying elements included in the magnetic field applying unit 53 is not limited to two and can be arbitrary. In other words, it is configured to induce at least a part of the external magnetic field H in the x-axis direction, which is the in-plane direction of the thermoelectric conversion unit 22 in the form of a thin film, for the thermoelectric conversion unit 22 by generating a magnetic field based on an input signal having a phase difference corresponding to the positional relationship between the first coil 531 and the second coil 532.

[0148] In the above-described embodiment, although the signal processing system 3 is described as being included in each of the measurement systems 1a, 1b, and 1c, these distinctions are assumed. That is, each of the measurement systems 1a, 1b, and 1c itself can also constitute the signal processing system 3. In other words, the signal processing system 3 can also include the heat flux sensor 2.

[0149] In the above-described embodiment, although various storages or controls are performed by the signal processing device 4, multiple external devices can be used instead of the signal processing device 4. That is, various information or programs can also be distributed and stored in multiple external devices using blockchain technology or the like.

[0150] The signal processing system 3 includes at least one processor 43 that can execute a program to implement each part of the signal processing method. In addition, the form of the above-described embodiment can also be a signal processing method. This signal processing method includes each part of the same signal processing system. In addition, the form of the above-described embodiment can also be a program. This program causes at least one computer to execute each step of the signal processing method.

[0151] The signal processing system 3 may not include the amplifying unit 314. Similarly, the signal processing circuit 5 may not include the amplifying unit 54. The signal processing system 3 can include both the signal processing circuit 31 and the signal processing circuit 5 at the same time.

[0152] In addition, it can also be provided in various forms described below.

[0153] (1) A signal processing method in a measurement system, wherein the measurement system includes a thermoelectric conversion unit configured to convert a temperature gradient generated by heat exchange with a measurement object into an electric signal based on the anomalous Nernst effect, and the signal processing method includes the following steps: In a modulation step, modulation including a predetermined modulation frequency is introduced into the electric signal output from the thermoelectric conversion unit to generate a modulation signal, where the modulation frequency is a frequency different from the frequency band of the thermoelectric conversion unit; and in an extraction step, a signal of the component of the modulation frequency is extracted from the modulation signal.

[0154] According to this configuration, since the modulation frequency component in the electric signal can be selectively extracted, the influence of noise in the measurement system can be reduced, and the heat flow detection accuracy by the thermoelectric conversion unit can be improved.

[0155] (2) The signal processing method according to (1) above, wherein the modulation step includes a magnetic field modulation step, and in the magnetic field modulation step, the modulation is introduced by applying an external magnetic field including the modulation frequency to the thermoelectric conversion unit.

[0156] According to this configuration, since interference can be introduced into the thermoelectric conversion unit non - contactlessly, the possibility of superimposing contact - type noises such as contact resistance on the electric signal can be reduced.

[0157] (3) The signal processing method according to (2) above, wherein in the magnetic field modulation step, the modulation is introduced by using the external magnetic field to reverse the sign of the component of the thermoelectric tensor of the thermoelectric conversion unit based on the anomalous Nernst effect.

[0158] According to this configuration, since the component of the thermoelectric tensor is reversed by the external magnetic field, the signal intensity in the modulation frequency band of the electric signal can be amplified.

[0159] (4) The signal processing method according to (2) or (3) above, wherein the thermoelectric conversion unit is formed in a thin - film shape and configured to be magnetized along the in - plane direction of the thin film, and in the magnetic field modulation step, the modulation is introduced by inducing the external magnetic field along the in - plane direction to the thermoelectric conversion unit.

[0160] According to this configuration, since modulation can be easily applied to the magnetic domains by inducing a small in - plane magnetic field to the thin film, the signal intensity in the modulation frequency band can be further amplified.

[0161] (5) The signal processing method according to any one of (1) to (4) above, wherein the modulation step further includes an electrical modulation step, in which the modulation is performed by changing the electrical characteristics of the circuit that transmits the electrical signal output from the thermoelectric conversion unit in synchronization with the modulation frequency.

[0162] With this configuration, it is possible to suppress an increase in the intrinsic noise induced in the thermoelectric conversion unit while extracting a signal that is not easily affected by noise.

[0163] (6) The signal processing method according to (5) above, wherein the circuit includes a switch capable of blocking the transmission of the electrical signal, and in the electrical modulation step, the modulation is performed by switching the on and off of the switch based on the modulation frequency.

[0164] With this configuration, it is possible to simplify the mechanism when modulating an electrical signal.

[0165] (7) A signal processing system in a measurement system, wherein the measurement system includes a thermoelectric conversion unit configured to convert a temperature gradient generated by heat exchange with a measurement object into an electrical signal based on the anomalous Nernst effect, the signal processing system includes a modulation unit and an extraction unit, the modulation unit is configured to introduce a modulation including a predetermined modulation frequency into the electrical signal output from the thermoelectric conversion unit to generate a modulation signal, where the modulation frequency is a frequency outside the frequency band of the thermoelectric conversion unit, and the extraction unit is configured to extract a signal of the component of the modulation frequency from the modulation signal.

[0166] With this configuration, since it is possible to selectively extract the modulation frequency component in the electrical signal, it is possible to reduce the influence of noise in the measurement system and improve the accuracy of heat flow detection performed by the thermoelectric conversion unit.

[0167] (8) The signal processing system according to (7) above, further including a magnetic field application unit configured to apply an external magnetic field including the modulation frequency to the thermoelectric conversion unit.

[0168] With this configuration, since it is possible to introduce interference into the thermoelectric conversion unit non - contactlessly, it is possible to reduce the possibility of superimposing contact - type noises such as contact resistance on the electrical signal.

[0169] (9) The signal processing system according to (8) above, wherein the magnetic field application unit applies the external magnetic field to the thermoelectric conversion unit to reverse the sign of the component of the thermoelectric tensor of the thermoelectric conversion unit based on the anomalous Nernst effect using the external magnetic field.

[0170] With this configuration, since the components of the thermoelectric tensor are inverted by an external magnetic field, the signal intensity in the modulation frequency band of the electrical signal can be amplified.

[0171] (10) The signal processing system according to any one of (8) or (9) above, wherein the thermoelectric conversion unit is formed in a thin film shape and includes magnetic domains configured to be magnetized in the in-plane direction of the thin film, and the magnetic field application unit is arranged with respect to the thermoelectric conversion unit to inductively apply the external magnetic field to the thermoelectric conversion unit in the in-plane direction.

[0172] With this configuration, since it is possible to easily apply modulation to the magnetic domains by inducting a minute in-plane magnetic field in the thin film, the signal intensity in the modulation frequency band can be further amplified.

[0173] (11) The signal processing system according to (10) above, further including the thermoelectric conversion unit and an insulating unit, the insulating unit being configured to have a first surface and a second surface that is in a relative position to the first surface in the thickness direction, the thermoelectric conversion unit being laminated on the first surface, the magnetic field application unit being arranged on the second surface to be electrically insulated from the thermoelectric conversion unit, and including a first magnetic field generating element and a second magnetic field generating element, the first magnetic field generating element and the second magnetic field generating element being configured to generate a magnetic field based on an input signal having a phase difference corresponding to the positional relationship between the first magnetic field generating element and the second magnetic field generating element, thereby inducting at least a part of the external magnetic field to the thermoelectric conversion unit in the in-plane direction of the thin-film thermoelectric conversion unit.

[0174] With this configuration, a more compact signal processing system integrated with the thermoelectric conversion unit can be realized.

[0175] (12) The signal processing system according to any one of (7) to (11) above, wherein the modulation unit further includes an electrical modulation unit configured to change the electrical characteristics of the transmission circuit that transmits the electrical signal from the thermoelectric conversion unit to the extraction unit in synchronization with the modulation frequency.

[0176] With this configuration, an increase in the intrinsic noise induced in the thermoelectric conversion unit can be suppressed while extracting a signal that is less susceptible to noise.

[0177] (13) The signal processing system according to (12) above, wherein the transmission circuit includes a switch capable of blocking the transmission of the electrical signal, and the electrical modulation unit is configured to switch the on and off of the switch based on the modulation frequency, thereby performing the modulation.

[0178] With this configuration, the mechanism for modulating the electrical signal can be simplified.

[0179] (14) The signal processing system according to any one of (7) to (13) above, wherein the extraction unit is configured to extract a signal of the modulation frequency from the modulation signal by a locking method based on a signal from an oscillator, and the oscillator is configured to output a signal of the modulation frequency.

[0180] With this configuration, the synchronization accuracy of the signal can be improved, and the noise component can be further reduced.

[0181] (15) A signal processing program product in a measurement system, wherein the measurement system includes a thermoelectric conversion unit configured to convert a temperature gradient generated by heat exchange with a measurement object into an electric signal based on the anomalous Nernst effect, and the signal processing program product is configured to cause at least one computer to perform the following steps: in a modulation step, introducing modulation including a predetermined modulation frequency into the electric signal output from the thermoelectric conversion unit to generate a modulation signal, where the modulation frequency is a frequency different from the frequency band of the thermoelectric conversion unit; and in an extraction step, extracting a signal of the modulation frequency component from the modulation signal.

[0182] With this configuration, since the modulation frequency component in the electric signal can be selectively extracted, the noise influence in the measurement system can be reduced, and the heat flow detection accuracy by the thermoelectric conversion unit can be improved.

[0183] Of course, it is not limited to this.

[0184] Finally, although various embodiments related to the present disclosure have been described, these are only presented as examples and are not intended to limit the scope of the invention. The new embodiment can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalents. Description of reference numerals

[0185] 1: Measurement system

[0186] 1a: Measurement system

[0187] 1b: Measurement system

[0188] [[ID=2⑨]]1c: Measurement system

[0189] 2: Heat flow sensor

[0190] 2a: First heat flow sensor

[0191] 2b: Second heat flow sensor

[0192] 21: Substrate

[0193] 211: Connection surface,

[0194] 212: Measurement surface,

[0195] 22: Thermoelectric conversion section,

[0196] 23: Wiring,

[0197] 24: Output section,

[0198] 25: Insulation layer,

[0199] 26: Heat sink,

[0200] 3: Signal processing system,

[0201] 31: Signal processing circuit,

[0202] 311: Chopper circuit,

[0203] 312: Switch controller,

[0204] 313: Filter circuit,

[0205] 314: Amplification section,

[0206] 315: Arithmetic circuit,

[0207] 4: Signal processing device,

[0208] 40: Communication bus,

[0209] 41: Communication section,

[0210] 42: Storage section,

[0211] 43: Processor,

[0212] 44: Display section,

[0213] 45: Input section,

[0214] 5: Signal processing circuit,

[0215] 51: Oscillator,

[0216] 52: Magnet controller,

[0217] 53: Magnetic field application section,

[0218] 54: Amplification section,

[0219] 55: Lock-in detector,

[0220] 56: Filter circuit,

[0221] 531: First coil,

[0222] 532: Second coil,

[0223] H: External magnetic field,

[0224] M: Magnetization,

[0225] N: Noise component,

[0226] T: Period,

[0227] V1: Total electromotive force,

[0228] V1a: First total electromotive force,

[0229] V1b: Second total electromotive force,

[0230] V1t: True total electromotive force,

[0231] V2: Modulation signal,

[0232] V2a: First modulation signal, V2b: Second modulation signal, V3: Output signal, V4: Operational electrical signal, fN: Noise frequency, fc: Cut-off frequency, fm: Modulation frequency, fn: Noise frequency.

Claims

1. A signal processing method in a measurement system, wherein, the measurement system includes a thermoelectric conversion unit, the thermoelectric conversion unit is configured to convert a temperature gradient generated by heat exchange with a measurement object into an electric signal based on the anomalous Nernst effect, the signal processing method includes the following steps: In a modulation step, modulation including a predetermined modulation frequency is introduced into the electric signal output from the thermoelectric conversion unit, thereby generating a modulation signal. Here, the modulation frequency is a frequency different from the frequency band of the thermoelectric conversion unit; and In an extraction step, a signal of the component of the modulation frequency is extracted from the modulation signal.

2. The signal processing method according to claim 1, wherein, the modulation step includes a magnetic field modulation step, in the magnetic field modulation step, the modulation is introduced by applying an external magnetic field including the modulation frequency to the thermoelectric conversion unit.

3. The signal processing method according to claim 2, wherein, in the magnetic field modulation step, the modulation is introduced by using the external magnetic field to reverse the sign of the component based on the anomalous Nernst effect in the thermoelectric tensor of the thermoelectric conversion unit.

4. The signal processing method according to claim 2 or 3, wherein, the thermoelectric conversion unit is formed in a thin film shape and is configured to be magnetized along the in-plane direction of the thin film, in the magnetic field modulation step, the modulation is introduced by inducing the external magnetic field along the in-plane direction to the thermoelectric conversion unit.

5. The signal processing method according to any one of claims 1 to 4, wherein, the modulation step further includes an electric modulation step, in the electric modulation step, the modulation is performed by synchronously changing the electrical characteristics of a circuit that transmits the electric signal output from the thermoelectric conversion unit with the modulation frequency.

6. The signal processing method according to claim 5, wherein, the circuit includes a switch capable of blocking the transmission of the electric signal, in the electric modulation step, the modulation is performed by switching the on and off of the switch based on the modulation frequency.

7. A signal processing system in a measurement system, wherein, the measurement system includes a thermoelectric conversion unit, the thermoelectric conversion unit is configured to convert a temperature gradient generated by heat exchange with a measurement object into an electric signal based on the anomalous Nernst effect, the signal processing system includes a modulation unit and an extraction unit, the modulation unit is configured to introduce modulation including a predetermined modulation frequency into the electric signal output from the thermoelectric conversion unit, thereby generating a modulation signal. Here, the modulation frequency is outside the frequency band of the thermoelectric conversion unit, the extraction unit is configured to extract a signal of the component of the modulation frequency from the modulation signal.

8. The signal processing system according to claim 7, wherein, it further includes a magnetic field application unit, the magnetic field application unit is configured to apply an external magnetic field including the modulation frequency to the thermoelectric conversion unit.

9. The signal processing system according to claim 8, wherein, The magnetic field applying unit applies the external magnetic field to the thermoelectric conversion unit so as to reverse the sign of the component based on the anomalous Nernst effect in the thermoelectric tensor of the thermoelectric conversion unit by using the external magnetic field.

10. The signal processing system according to any one of claims 8 or 9, wherein, The thermoelectric conversion unit is formed in a thin film shape and includes magnetic domains configured to be magnetized in the in-plane direction of the thin film, The magnetic field applying unit is disposed relative to the thermoelectric conversion unit to inductively apply the external magnetic field to the thermoelectric conversion unit in the in-plane direction.

11. The signal processing system according to claim 10, wherein, The thermoelectric conversion unit and an insulating unit are further provided, The insulating unit is configured to have a first surface and a second surface that is in a relative position to the first surface in the thickness direction, The thermoelectric conversion unit is laminated on the first surface, The magnetic field applying unit is disposed on the second surface to be electrically insulated from the thermoelectric conversion unit and includes a first magnetic field generating element and a second magnetic field generating element, The first magnetic field generating element and the second magnetic field generating element are configured to generate a magnetic field based on an input signal having a phase difference corresponding to the positional relationship between the first magnetic field generating element and the second magnetic field generating element, thereby inductively applying at least a part of the external magnetic field to the thermoelectric conversion unit in the in-plane direction of the thin film-shaped thermoelectric conversion unit.

12. The signal processing system according to any one of claims 7 to 11, wherein, The modulation unit further includes an electrical modulation unit, The electrical modulation unit is configured to change the electrical characteristics of a transfer circuit that transfers the electrical signal from the thermoelectric conversion unit to the extraction unit in synchronization with the modulation frequency for the electrical signal output from the thermoelectric conversion unit.

13. The signal processing system according to claim 12, wherein, The transfer circuit includes a switch capable of blocking the transfer of the electrical signal, The electrical modulation unit is configured to switch the on and off of the switch based on the modulation frequency, thereby performing the modulation.

14. The signal processing system according to any one of claims 7 to 13, wherein, The extraction unit is configured to extract a signal of the modulation frequency from the modulation signal by a locking method based on a signal from an oscillator, and the oscillator is configured to output a signal of the modulation frequency.

15. A signal processing program product in a measurement system, wherein, The measurement system includes a thermoelectric conversion unit, The thermoelectric conversion unit is configured to convert a temperature gradient generated by heat exchange with a measurement object into an electrical signal based on the anomalous Nernst effect, The signal processing program product is configured to cause at least one computer to execute the following steps: In a modulation step, modulation including a predetermined modulation frequency is introduced into the electrical signal output from the thermoelectric conversion unit, thereby generating a modulation signal. Here, the modulation frequency is a frequency different from the frequency band of the thermoelectric conversion unit; and In an extraction step, a signal of the modulation frequency component is extracted from the modulation signal.

Images