JP2022126455A - Physical quantity derivation device, physical quantity derivation system, physical quantity derivation method, and program - Google Patents

Abstract

To further suppress deterioration in the accuracy of physical quantity measurement using a surface acoustic wave sensor.SOLUTION: A physical quantity derivation device may include an acquisition unit that acquires time information indicating time from transmitting a drive signal via a communication unit to receiving via the communication unit a response signal to the drive signal transmitted from a surface acoustic wave sensor that is driven by receiving the drive signal. The physical quantity derivation device may include a derivation unit that derives a physical quantity of an object based on the time information when a time change rate indicated by the time information falls within a predetermined change rate range.SELECTED DRAWING: Figure 6

Description

The present invention relates to a physical quantity derivation device, a physical quantity derivation system, a physical quantity derivation method, and a program.

Patent Literature 1 discloses a pressure sensor using surface acoustic waves and a pressure measuring device provided with the pressure sensor. Patent Document 2 discloses a surface acoustic wave sensor that detects physical quantities using surface acoustic waves. Patent Literature 3 discloses a property measuring device provided with a surface acoustic wave sensor. Patent Document 4 discloses a wireless temperature measurement system that measures temperature by wireless communication using surface acoustic waves.
[Prior art documents]
[Patent Literature]
[Patent Document 1] Japanese Patent No. 5101356 [Patent Document 2] Japanese Patent No. 5333538 [Patent Document 3] Japanese Unexamined Patent Publication No. 2019-120581 [Patent Document 4] Japanese Unexamined Patent Publication No. 2020-46257

It is desired to further suppress the deterioration of the accuracy of physical quantity measurement using a surface acoustic wave sensor.

In the physical quantity derivation device according to one aspect of the present invention, after the drive signal is transmitted via the communication unit, the response signal to the drive signal transmitted from the surface acoustic wave sensor driven by receiving the drive signal is transmitted from the communication unit. may be provided with an acquisition unit that acquires time information indicating the time until the data is received via the . The physical quantity derivation device may include a derivation unit that derives the physical quantity of the object based on the time information when the rate of change of time indicated by the time information is within a predetermined rate of change range.

The deriving unit derives the physical quantity of the object based on the time information when the time change rate indicated by the time information is within a predetermined change rate range and the SN ratio of the response signal is greater than the first SN ratio. You can

The derivation unit determines that the rate of change in time indicated by the time information is within a predetermined rate of change range, the SN ratio of the response signal is greater than a first SN ratio, and the time indicated by the time information is in the predetermined time range. , the physical quantity of the object may be derived based on the time information.

The acquisition unit may further acquire phase difference information indicating a phase difference between the drive signal and the response signal. The derivation unit determines that the rate of change of the time indicated by the time information is within a predetermined rate of change range, the SN ratio of the response signal is greater than a first SN ratio, and the time indicated by the time information is within the predetermined time range. Yes, and if the phase difference indicated by the phase difference information is within a predetermined phase difference range, the physical quantity of the object may be derived based on the time information and the phase difference information.

Even when the time indicated by the time information is not within the predetermined time range, the derivation unit determines that the rate of change of the time indicated by the time information is within the predetermined rate of change range, and the SN ratio of the response signal is the first SN If the phase difference indicated by the phase difference information indicating the phase difference between the drive signal and the response signal is within a predetermined phase difference range, based on the phase difference information, the object can be derived.

Even when the phase difference indicated by the phase difference information is not within the predetermined phase difference range, the derivation unit determines that the time change rate indicated by the time information is within the predetermined change rate range, and the SN ratio of the response signal is greater than the second SN ratio, which is greater than the first SN ratio, and the time indicated by the time information is within a predetermined time range, the physical quantity of the object may be derived based on the time information.

The deriving unit derives the physical quantity of the object based on the time information, and if the change rate of the physical quantity of the object based on the time information is within a predetermined change rate range, the change rate of the time indicated by the time information is set in advance. It may be determined that the rate of change is within a specified range.

A physical quantity derivation system according to an aspect of the present invention may include the physical quantity derivation device described above and a surface acoustic wave sensor.

In a physical quantity derivation method according to an aspect of the present invention, after a drive signal is transmitted via a communication unit, a response signal to the drive signal transmitted from the surface acoustic wave sensor driven by receiving the drive signal is transmitted from the communication unit. obtaining time information indicative of a time until it is received via the . The physical quantity derivation method may include the step of deriving the physical quantity of the object based on the time information when the time change rate indicated by the time information is within a predetermined range.

A program according to an aspect of the present invention transmits a response signal to a drive signal transmitted from a surface acoustic wave sensor driven by receiving the drive signal through the communication unit after the drive signal is transmitted through the communication unit. may cause the computer to perform the step of obtaining time information indicative of the time until the time it was received. The program may cause the computer to derive the physical quantity of the object based on the time information when the time change rate indicated by the time information is within a predetermined range.

It should be noted that the above summary of the invention does not list all the features of the invention. Subcombinations of these feature groups can also be inventions.

It is a figure which shows the whole structure of a temperature measurement system. 1 is a schematic diagram showing the configuration of a surface acoustic wave device; FIG. FIG. 4 is a diagram showing an example of time-series data showing the relationship between reception intensity and noise intensity obtained by signal processing on a differential signal, and delay time; FIG. 4 is a characteristic diagram showing an example of the relationship between the temperature in the SAW sensor and the propagation time information and propagation phase information; 4 is a flow chart showing an example of a procedure for a calculation circuit to calculate the temperature of an object based on propagation time information and propagation phase information; 4 is a flow chart showing an example of a procedure for temperature measurement by a master device; 9 is a flow chart showing another example of the temperature measurement procedure by the master device; It is a figure which shows an example of a hardware configuration.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution of the invention.

A computer-readable medium may include any tangible device capable of storing instructions for execution by a suitable device. As a result, a computer-readable medium having instructions stored thereon provides an article of manufacture that includes instructions that can be executed to create means for performing the operations specified in the flowchart or block diagram. Examples of computer-readable media may include electronic storage media, magnetic storage media, optical storage media, electromagnetic storage media, semiconductor storage media, and the like. More specific examples of computer readable media include floppy disks, diskettes, hard disks, random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM or flash memory), Electrically Erasable Programmable Read Only Memory (EEPROM), Static Random Access Memory (SRAM), Compact Disc Read Only Memory (CD-ROM), Digital Versatile Disc (DVD), Blu-ray (RTM) Disc, Memory Stick, Integration Circuit cards and the like may be included.

The computer readable instructions may comprise either source code or object code written in any combination of one or more programming languages. Source code or object code includes conventional procedural programming languages. Traditional procedural programming languages include assembler instructions, Instruction Set Architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state setting data, or Smalltalk, JAVA, C++. etc., and the "C" programming language or similar programming languages. Computer readable instructions may be transferred to a processor or programmable circuitry of a general purpose computer, special purpose computer, or other programmable data processing apparatus, either locally or over a wide area network (WAN), such as a local area network (LAN), the Internet, or the like. ) may be provided via A processor or programmable circuit may execute computer readable instructions to produce means for performing the operations specified in the flowcharts or block diagrams. Examples of processors include computer processors, processing units, microprocessors, digital signal processors, controllers, microcontrollers, and the like.

2. Description of the Related Art Conventionally, various sensors and measuring devices for measuring physical quantities such as temperature and pressure have been provided, taking advantage of changes in the propagation characteristics of surface acoustic waves (SAWs) due to physical quantities such as temperature and pressure.

For example, the pressure sensor and pressure measuring device described in Patent Document 1 are driven from a computer as a master device via a reading device and an antenna to a pressure sensor that is a wireless parasitic sensor installed on a detection target. A signal is transmitted wirelessly, a reading device receives a response signal from the pressure sensor, and a computer detects the gas pressure (air pressure) applied to the object to be detected.

In the above pressure sensor, the comb-teeth electrode in the pressure sensor receives a drive signal from a computer and excites a surface acoustic wave. The comb electrode converts the signal from the reflective electrode into a response signal and sends it back to the computer via the antenna and reader.

Here, when the pressure applied to the object to be sensed changes, the propagation velocity of the surface acoustic wave in the pressure sensor changes, and this appears as a phase change in the response signal. The pressure applied to the object to be detected can be detected based on the time difference).

Further, the surface acoustic wave sensors described in Patent Documents 2 and 3 use the same principle as that of Patent Document 1 to detect the strain, temperature, or liquid of the object to be detected by utilizing the change in the phase of the surface acoustic wave. Used to detect concentration.

Since the sensors disclosed in Patent Documents 1, 2, and 3 all measure the physical quantity by detecting changes in phase, the signal processing method is the drive signal transmitted from the master device to the sensor. and the response signal from the sensor to analyze the phase or frequency.

By the way, when receiving response signals from sensors wirelessly, depending on the communication environment, outliers that closely resemble normal signals, such as multipath fading or fading, may be obtained, reducing the measurement accuracy of physical quantities. sometimes.

Therefore, the present embodiment provides a physical quantity derivation system capable of excluding outliers even if outliers are acquired due to changes in the external environment such as reception of unknown radio waves or fading.

FIG. 1 is a diagram showing the overall configuration of a temperature measurement system 100 according to this embodiment. The temperature measurement system 100 uses the surface acoustic wave device 22 to measure the temperature as a physical quantity of an object. A temperature measurement system is an example of a physical quantity derivation system. The physical quantity derivation system may derive physical quantities other than the temperature, such as distortion of the object, pressure of the object, concentration of the liquid of the object, etc., as the physical quantity of the object.

A temperature measurement system 100 comprises a master device 10 and a SAW sensor 20 . The master device 10 is composed of a microcomputer or the like. The master device 10 has an antenna 11 for wireless communication with the SAW sensor 20 . Antenna 11 is an example of a communication unit. The SAW sensor 20 is a wireless parasitic sensor for temperature measurement. The SAW sensor 20 has an antenna 21 for wireless communication with the master device 10 . The SAW sensor 20 has a surface acoustic wave element 22 . The SAW sensor 20 may be installed near an object whose temperature is to be detected.

The master device 10 comprises a drive circuit 12, an amplifier circuit 13, and a calculation circuit 14. FIG. The drive circuit 12 oscillates a drive signal with a predetermined frequency. The drive signal may be a high frequency signal such as 2.5 GHz. SAW sensor 20 is driven by receiving a drive signal transmitted via antenna 11 via antenna 21 . The surface acoustic wave element 22 receives the driving signal oscillated from the driving circuit 12 via the antennas 11 and 21 . The surface acoustic wave element 22 oscillates a response signal to the drive signal.

The master device 10 receives the response signal oscillated from the surface acoustic wave element 22 via the antennas 11 and 21 . The amplifier circuit 13 amplifies a difference signal indicating the difference between the drive signal and the response signal, and outputs it to the calculation circuit 14 .

The calculation circuit 14 measures the temperature of the object based on the input amplified differential signal. The differential signal reflects the propagation characteristics of surface acoustic waves generated by the surface acoustic wave element 22 . Since this propagation-specific change depends on the temperature change of the object, the temperature of the object can be derived from the propagation characteristics of the differential signal. Note that the temperature of the object may be derived from propagation characteristics such as speed, phase, frequency, or delay time, in addition to the difference signal between the drive signal and the response signal.

Various operations in the drive circuit 12, the amplifier circuit 13, and the calculation circuit 14 may be performed by the processor executing a program stored in the memory. The memory is composed of one or more recording media such as ROM (Read Only Memory), RAM (Random Access Memory), etc., depending on the application. These memories may store, as a database, various parameters indicating the propagation characteristics that serve as a reference when calculating the propagation characteristics of the response signal, the correspondence relationship between the propagation characteristics of the response signal and the temperature of the object, and the like.

FIG. 2 is a schematic diagram showing the structure of the surface acoustic wave element 22 shown in FIG. The surface acoustic wave element 22 includes a piezoelectric substrate 221 , an IDT (Inter Digital Transducers) electrode 222 and a reflective electrode 223 . The IDT electrode 222 and the reflective electrode 223 are arranged at predetermined intervals on the surface of the piezoelectric substrate 221 capable of propagating surface acoustic waves. As the piezoelectric substrate 221, a piezoelectric substrate that generates a Rayleigh wave vibrating perpendicularly to the substrate surface as a surface acoustic wave may be used. As the piezoelectric substrate 221, a piezoelectric substrate that generates an SH wave or plate wave vibrating parallel to the substrate surface and perpendicular to the traveling direction as a surface acoustic wave may be used.

The piezoelectric substrate 221 may be composed of materials such as lithium compounds such as lithium tantalate (LiTaO3), lithium niobate (LiNbO3), lithium tetraborate (Li2B4O7), crystal, or langasite, for example. The piezoelectric substrate 221 may be configured by combining aluminum nitride (AlN) having a piezoelectric function and sapphire as a substrate holding a thin film.

The IDT electrode 222 has a pair of comb-teeth electrodes 222a and 222b. The pair of comb-teeth electrodes 222a and 222b are arranged to face each other such that the electrode piece of the other comb-teeth electrode 222b is arranged between the electrode pieces of one comb-teeth electrode 222a. One comb-teeth electrode 222a is connected to the antenna 21, and the other comb-teeth electrode 222b is grounded. The IDT electrodes 222 may be composed of materials such as aluminum, titanium, chromium, gold, platinum, and the like, for example.

The number and width of the individual electrode pieces of the comb electrodes 222a and 222b, the pitch between the electrode pieces, and the like are not particularly limited, and can be appropriately changed in consideration of the excitation efficiency. When a drive signal from the master device 10 is input to the IDT electrodes 222 via the antenna 21 , surface acoustic waves are excited at the IDT electrodes 222 .

The reflective electrode 223 has a plurality of electrode strips arranged parallel to the electrode strips of the comb-teeth electrodes 222a and 222b. The reflective electrode 223 has a function of reflecting the surface acoustic wave propagating from the IDT electrode 222 through the surface of the piezoelectric substrate 221 toward the IDT electrode 222 . During the propagation of the surface acoustic wave, the propagation characteristics such as the propagation speed of the surface acoustic wave change according to the state of the object, for example, the temperature, and the surface acoustic wave reflected by the reflective electrode 223 is input to the IDT electrode 222. Thus, a response signal to be transmitted from the SAW sensor 20 to the master device 10 is generated.

The number and width of the individual electrode pieces of the reflective electrode 223, the pitch between the electrode pieces, and the like are not particularly limited, and can be appropriately changed in consideration of the reflection efficiency. However, in order to take advantage of the features of this embodiment, it is desirable to arrange three or more reflective electrodes 223 . The reflective electrode 223 may be made of the same material as the IDT electrode 222 .

The amplifier circuit 13 receives, via the antenna 11, a response signal to the drive signal transmitted from the SAW sensor 20. FIG. Antenna 11 is an example of a communication unit.

The amplifier circuit 13 amplifies the differential signal between the drive signal and the response signal. Calculation circuit 14 converts the amplified difference signal into a signal including analog-to-digital signal conversion (AD conversion) processing and discrete Fourier transform (DFT) or fast Fourier transform (FFT) processing at a predetermined sampling frequency. Acquire the measurement signal by executing the process.

The calculation circuit 14 performs signal processing on the difference signal to indicate the time from when the drive signal is transmitted via the antenna 11 until when the response signal from the SAW sensor 20 is received via the antenna 11. Propagation time information and propagation phase information indicating the phase difference between the drive signal and the response signal are obtained. The calculation circuit 14 derives the temperature of the object as a physical quantity of the object based on at least one of the propagation time information and the phase difference information. The calculation circuit 14 is an example of an acquisition unit and a derivation unit.

The configurations of the temperature measurement system 100 and the surface acoustic wave element 22 are not limited to the configurations described above, and can be changed as appropriate without departing from the scope of the present invention.

FIG. 3 shows an example of time-series data showing the relationship between the reception intensity and noise intensity obtained by signal processing of the difference signal by the calculation circuit 14 and the delay time. The calculation circuit 14 acquires, as propagation time information, information indicating the delay time corresponding to the peak value of the reception intensity in the time-series data as shown in FIG. The calculation circuit 14 acquires, as propagation phase information, information indicating the phase value at the delay time corresponding to the peak value of the reception intensity.

FIG. 4 is a characteristic diagram showing an example of the relationship between the temperature in the SAW sensor 20 and the propagation time information t and the propagation phase information p. A measurement signal obtained by signal processing of the difference signal by the calculation circuit 14 includes propagation time information t and propagation phase information p.

As shown in FIG. 4, when the temperature of the SAW sensor 20 is increased, the propagation time information t varies substantially linearly with respect to the temperature, but there are large variations. When this variation is converted to temperature, it corresponds to several tens of degrees [°C]. On the other hand, the propagation phase information p decreases while appearing discontinuous points when changing from -π [rad] to π [rad]. However, the variation in temperature calculated from the propagation phase information p is 0.1 [° C.] or less, which is highly accurate.

In other words, the propagation time information t varies substantially linearly but has large variations, and the propagation phase information p has discontinuities but has small variations. Therefore, in order to know the absolute temperature value of the object and to measure the temperature with high accuracy in a wide temperature range, the discontinuity point of the propagation phase information p is determined by using the propagation time information t for calculating the temperature. A method of correction is effective.

FIG. 5 is a flow chart showing an example of a procedure by which the calculation circuit 14 calculates the temperature of the object based on the propagation time information t and the propagation phase information p.

The calculation circuit 14 acquires propagation time information t and propagation phase information p by executing signal processing including AD conversion and DFT or FFT processing on the difference signal (S10). Next, the calculation circuit 14 calculates the time calculation temperature Tt corresponding to the propagation time information t based on the relationship between the propagation time information t, the propagation phase information p, and the temperature T as shown in FIG. A phase calculation temperature Tp corresponding to the phase information p is calculated. At the same time, the temperature range Tr per phase 2π [rad] is calculated based on the temperature calculation coefficient obtained in advance from the actual measurement (step S12).

Next, a correction coefficient a that minimizes |α| is derived from Equation 1 below regarding the difference between the time calculation temperature Tt and the phase calculation temperature Tp (step S14).
[Formula 1]
Tt−Tp=a×Tr+α

Then, the phase calculation temperature Tpopt after correction is derived as the absolute value temperature of the object by the following Equation 2 (step S16).
[Formula 2]
Tpopt=Tp+a×Tr

As described above, the absolute temperature of the object can be measured with higher accuracy using the propagation time information t and the propagation phase information p.

However, due to the reception of unknown radio waves or changes in the external environment such as fading, an outlier that closely resembles a normal response signal may be obtained, and the propagation time information t or the propagation phase information p may not be derived accurately. If a physical quantity such as absolute temperature is measured using such propagation time information t or propagation phase information p, the measurement accuracy may be lowered.

Therefore, the calculation circuit 14 determines whether or not the time change rate indicated by the propagation time information t is within a predetermined change rate range. If the change rate is not within the predetermined change rate range, the calculation circuit 14 determines that the change in time is extreme, that is, the change in temperature is extreme, and the propagation time information t is an outlier, the propagation time information t derived this time is not used. In this case, the calculation circuit 14 may determine that the temperature cannot be measured. Alternatively, the calculation circuit 14 may derive the current absolute value temperature using the propagation time information t derived last time. On the other hand, if the time change rate indicated by the propagation time information t is within a predetermined change rate range, the calculation circuit 14 derives the absolute temperature of the object based on the propagation time information t.

The calculation circuit 14 may derive the time change rate based on the time indicated by the propagation time information t and the sampling time. The calculation circuit 14 may derive the time change rate by dividing the difference between the current propagation time and the previous propagation time by the sampling time. The calculation circuit 14 may derive the time rate of change based on the moving average value of each time indicated by the propagation time information t and the sampling time. The calculation circuit 14 may derive the time change rate by dividing the difference between the moving average value of the current propagation time and the moving average value of the previous propagation time by the sampling time.

After calculating the time calculation temperature Tt corresponding to the propagation time information t, the calculation circuit 14 determines whether or not the change rate of the time calculation temperature Tt is within a predetermined change rate range. It may be determined whether or not the change rate of the time indicated by t is within a predetermined change rate range. The calculation circuit 14 may derive the temperature change rate [° C./min] by dividing the difference between the previous time-calculated temperature Tt and the current time-calculated temperature Tt by the sampling time. The calculation circuit 14 divides the difference between the temperature moving average value derived from the previous propagation time information t and the temperature moving average value derived from the current propagation time information t by the sampling time. A temperature change rate [°C/min] may be derived.

Moreover, when noise is included in the response signal, the SN ratio of the response signal is lowered, and the SN ratio of the measurement signal as shown in FIG. 3 may also be lowered. If the SN ratio is low, it may not be possible to accurately derive the propagation time information t or the propagation phase information p. Therefore, when the time change rate indicated by the propagation time information t is within a predetermined change rate range and the SN ratio of the response signal is greater than the predetermined SN ratio, the calculation circuit 14 calculates the propagation time information t. , the absolute temperature of the object may be derived. If the time change rate indicated by the propagation time information t is not within a predetermined change rate range, or if the SN ratio of the response signal is equal to or less than a predetermined SN ratio, the calculation circuit 14 calculates the propagation time information t as Based on this, the absolute temperature of the object is not derived. If the change rate of the time indicated by the propagation time information t is not within a predetermined change rate range or the SN ratio of the response signal is equal to or less than the predetermined SN ratio, the calculation circuit 14 calculates the currently derived propagation The propagation time information t derived this time is not used because the time information t is an outlier. In this case, the calculation circuit 14 may determine that the temperature cannot be measured. Alternatively, the calculation circuit 14 may derive the current absolute value temperature using the propagation time information t derived last time.

Furthermore, when noise is included in the response signal, the time indicated by the propagation time information t may not be included in the predetermined time range. That is, there are cases where the temperature derived based on the propagation time information t is not within the temperature range expected to be measured by the SAW sensor 20 . In this case, the propagation time information t may be an outlier. Therefore, the calculation circuit 14 determines that the time change rate indicated by the propagation time information t is within a predetermined change rate range, the SN ratio of the response signal is greater than the first predetermined SN ratio, and the propagation time information t is within a predetermined time range, the absolute temperature of the object is derived based on the propagation time information t. On the other hand, the calculation circuit 14 determines that the time change rate indicated by the propagation time information t is not within the predetermined change rate range, that the SN ratio of the response signal is equal to or less than a predetermined first SN ratio, or that the propagation time information t If the indicated time is not within the predetermined time range, no absolute temperature of the object is derived based on the propagation time information t. In this case, the calculation circuit 14 may determine that the temperature cannot be measured. Alternatively, the calculation circuit 14 may derive the current absolute value temperature using the propagation time information t derived last time. If the temperature derived based on the propagation time information t is not within the predetermined temperature range, the calculation circuit 14 may determine that the time indicated by the propagation time information t is not within the predetermined time range. .

In addition, when noise is included in the response signal, the phase difference indicated by the propagation phase information p may not be included in the predetermined phase difference range. That is, the temperature derived based on the propagation phase information p may not fall within the temperature range that is assumed to be measured by the SAW sensor 20 . In this case, the propagation phase information p may be an outlier. Therefore, the calculation circuit 14 determines that the time change rate indicated by the propagation time information is within a predetermined change rate range, the SN ratio of the response signal is greater than the first predetermined SN ratio, and the propagation time information t indicates If the time is within a predetermined time range and the phase difference indicated by the propagation phase information p is within the predetermined phase difference range, based on the propagation time information t and the propagation phase information p, the object Absolute temperature may be derived.

On the other hand, the calculation circuit 14 determines that the SN ratio of the response signal is less than or equal to the predetermined first SN ratio when the change rate of the time indicated by the propagation time information t is not within the predetermined change rate range, and If the time is not within the predetermined time range, or the phase difference indicated by the propagation phase information p is not within the predetermined phase difference range, based on the propagation time information t and the propagation phase information p, the object Do not derive absolute temperature. In this case, the calculation circuit 14 may determine that the temperature cannot be measured. Alternatively, the calculation circuit 14 may derive the current absolute value temperature using the propagation time information t and the propagation phase information p derived last time. When the temperature derived based on the propagation phase information p is not within the predetermined temperature range, the calculation circuit 14 determines that the phase difference indicated by the propagation phase information p is not within the predetermined phase difference range. you can

Note that the predetermined first SN ratio, the predetermined temperature range, the predetermined time range, and the predetermined phase difference range may be determined based on the performance of the SAW sensor 20. The predetermined first SN ratio, the predetermined temperature range, the predetermined time range, and the predetermined phase difference range are determined based on actual measurement results using the SAW sensor 20. good. The predetermined first SN ratio may be determined as a value that can guarantee the measurement accuracy of the SAW sensor 20 . The predetermined temperature range, the predetermined time range, and the predetermined phase difference range are determined based on the temperature range assumed to be measured by SAW sensor 20 and the responsiveness of SAW sensor 20. you can

FIG. 6 is a flow chart showing an example of a temperature measurement procedure by the master device 10. As shown in FIG. The calculation circuit 14 performs analog/digital signal conversion (AD conversion) processing and discrete Fourier transform (DFT) or fast Fourier transform (FFT) on the differential signal amplified by the amplifier circuit 13 at a predetermined sampling frequency. Processing is executed to acquire propagation time information t and propagation phase information p (S100).

The calculation circuit 14 determines whether or not the SN ratio of the measurement signal obtained by executing the AD conversion process and the DFT or FFT process is greater than the threshold tha corresponding to the first SN ratio (S102). If the SN ratio of the measurement signal is equal to or less than the threshold tha, the calculation circuit 14 determines that the temperature cannot be measured, or applies the previous absolute value temperature to the current absolute value temperature (S112).

On the other hand, when the SN ratio of the measurement signal is greater than the threshold tha, the calculation circuit 14 determines whether or not the change rate of the propagation time indicated by the propagation time information t is within a predetermined change rate range (S104). . The calculation circuit 14 determines whether or not the change rate of the time-calculated temperature Tt corresponding to the propagation time information t is within a predetermined change rate range. It may be determined whether or not it is within a defined rate of change range.

If the rate of change of the propagation time indicated by the propagation time information t is not within the predetermined rate of change range, the calculation circuit 14 determines that the temperature cannot be measured, or applies the previous absolute temperature to the current absolute temperature. (S112).

On the other hand, when the rate of change of the propagation time indicated by the propagation time information t is within the predetermined rate of change range, the calculation circuit 14 determines whether the propagation time indicated by the propagation time information t is within the predetermined time range. It is determined whether or not (S104). The calculation circuit 14 determines whether or not the time calculation temperature Tt corresponding to the propagation time information t is within the predetermined temperature range, so that the propagation time indicated by the propagation time information t is within the predetermined time range. It may be determined whether or not there is

If the propagation time indicated by the propagation time information t is not within the predetermined time range, the calculation circuit 14 determines that the temperature cannot be measured, or applies the previous absolute temperature to the current absolute temperature (S112). .

On the other hand, if the propagation time indicated by the propagation time information t is within the predetermined time range, the calculation circuit 14 determines whether the phase difference indicated by the propagation phase information p is within the predetermined phase difference range. Determine (S108). The calculation circuit 14 determines whether or not the phase calculation temperature Tp corresponding to the propagation phase information p is within a predetermined temperature range. It may be determined whether it is in range.

If the phase difference indicated by the propagation phase information p is not within the predetermined phase difference range, the calculation circuit 14 determines that the temperature cannot be measured, or applies the previous absolute temperature to the current absolute temperature (S112 ).

On the other hand, when the phase difference indicated by the propagation phase information p is within the predetermined phase difference range, the calculation circuit 14 determines that the propagation time information t and the propagation phase information p are not outliers, and determines that the propagation time information t And based on the propagation phase information p, the absolute temperature of the object is derived (S110). The calculation circuit 14 may derive the corrected temperature Tpopt as the absolute temperature of the object according to the procedure shown in FIG.

As described above, according to the temperature measurement system 100 according to the present embodiment, when there is a possibility that the propagation time information t and the propagation phase information p are outliers, the calculation circuit 14 determines that the response signal received from the SAW sensor 20 has noise. It is determined that it is a mixed signal. The calculation circuit 14 does not derive the absolute temperature of the object using the propagation time information t and the propagation phase information p based on the response signal. The calculation circuit 14 uses the propagation time information t and the propagation phase information p based on the response signal containing little noise to derive the absolute temperature of the object. Therefore, deterioration in measurement accuracy of the temperature measurement system 100 can be suppressed.

Here, even if the time indicated by the propagation time information t is not within the predetermined time range, if the SN ratio of the response signal (measurement signal) is relatively large, the phase difference indicated by the phase difference information is predetermined. Within the phase difference range, the calculation circuit 14 can derive the physical quantity of the object based on the phase difference information with a certain degree of accuracy.

Further, even when the phase difference indicated by the propagation phase information p is not within the predetermined phase difference range, if the SN ratio of the response signal (measurement signal) is relatively large, the time indicated by the propagation time information is predetermined. Within this time range, the calculation circuit 14 can derive the physical quantity of the object based on the propagation time information with a certain degree of accuracy.

Therefore, even if the time indicated by the propagation time information t is not within the predetermined time range, or the phase difference indicated by the propagation phase information p is not within the predetermined phase difference range, the calculation circuit 14 can respond When the SN ratio of the signal (measurement signal) is larger than the threshold thb corresponding to the second SN ratio larger than the threshold tha, if the other conditions are satisfied, the propagation phase information p or the propagation time information t satisfying the conditions is used. may be used to derive the physical quantity of the object. Here, the threshold tha may be, for example, 10 dB, and the threshold thb may be, for example, 20 dB.

FIG. 7 is a flow chart showing another example of the procedure of temperature measurement by the master device 10. As shown in FIG. The calculation circuit 14 performs analog/digital signal conversion (AD conversion) processing and discrete Fourier transform (DFT) or fast Fourier transform (FFT) on the differential signal amplified by the amplifier circuit 13 at a predetermined sampling frequency. Processing is executed to acquire propagation time information t and propagation phase information p (S200).

The calculation circuit 14 determines whether or not the SN ratio of the measurement signal obtained by executing the AD conversion process and the DFT or FFT process is greater than the threshold tha (S202). If the SN ratio of the measurement signal is equal to or less than the threshold tha, the calculation circuit 14 determines that the temperature cannot be measured, or applies the previous absolute temperature to the current absolute temperature (S212).

On the other hand, when the SN ratio of the measurement signal is greater than the threshold tha, the calculation circuit 14 determines whether or not the change rate of the propagation time indicated by the propagation time information t is within a predetermined change rate range (S204). . If the rate of change of the propagation time indicated by the propagation time information t is not within the predetermined rate of change range, the calculation circuit 14 determines that the temperature cannot be measured, or applies the previous absolute temperature to the current absolute temperature. (S212).

On the other hand, when the rate of change of the propagation time indicated by the propagation time information t is within the predetermined rate of change range, the calculation circuit 14 determines whether the propagation time indicated by the propagation time information t is within the predetermined time range. It is determined whether or not (S206). If the propagation time indicated by the propagation time information t is not within the predetermined time range, the calculation circuit 14 determines whether the SN ratio of the response signal is greater than a predetermined threshold thb (threshold thb>threshold tha). Determine (S214).

If the SN ratio of the response signal is equal to or less than the predetermined threshold thb, the calculation circuit 14 determines that the temperature cannot be measured, or applies the previous absolute temperature to the current absolute temperature (S212).

On the other hand, if the SN ratio of the response signal is greater than the predetermined threshold thb, the calculation circuit 14 determines whether the phase difference indicated by the propagation phase information p is within the predetermined phase difference range (S216). ). If the phase difference indicated by the propagation phase information p is not within the predetermined phase difference range, the calculation circuit 14 determines that the temperature cannot be measured, or applies the previous absolute temperature to the current absolute temperature (S212 ).

On the other hand, when the phase difference indicated by the propagation phase information p is within the predetermined phase difference range, the calculation circuit 14 derives the absolute value temperature based on the propagation phase information p (S218). The calculation circuit 14 may derive the phase calculation temperature Tp corresponding to the propagation phase information p as an absolute value temperature.

If it is determined in step S206 that the propagation time indicated by the propagation time information t is within the predetermined time range, the calculation circuit 14 determines that the phase difference indicated by the propagation phase information p is within the predetermined phase difference range. (S208).

If the phase difference indicated by the propagation phase information p is within the predetermined phase difference range, the calculation circuit 14 derives the absolute temperature of the object based on the propagation time information t and the propagation phase information p (S210 ). The calculation circuit 14 may derive the corrected temperature Tpopt as the absolute temperature of the object according to the procedure shown in FIG.

On the other hand, when the phase difference indicated by the propagation phase information p is not within the predetermined phase difference range, the calculation circuit 14 determines whether or not the SN ratio of the response signal is greater than the predetermined threshold thb (S220). ).

If the SN ratio of the response signal is equal to or less than the predetermined threshold thb, the calculation circuit 14 determines that the temperature cannot be measured, or applies the previous absolute temperature to the current absolute temperature (S212).

On the other hand, when the SN ratio of the response signal is greater than the predetermined threshold thb, the calculation circuit 14 derives the absolute temperature based on the propagation time information t (S222). The calculation circuit 14 may calculate the time calculation temperature Tt corresponding to the propagation time information t as the absolute temperature of the object.

As described above, according to the temperature measurement system 100 according to the present embodiment, it is possible to prevent the propagation time information t and the propagation phase information p from being judged as outliers as much as possible while suppressing deterioration in the measurement accuracy of the temperature measurement system 100 .

FIG. 8 illustrates an example computer 1200 in which aspects of the invention may be implemented in whole or in part. Programs installed on computer 1200 may cause computer 1200 to act as one or more "parts" of or operations associated with apparatus according to embodiments of the present invention. Alternatively, the program may cause computer 1200 to perform the operation or the one or more "parts." The program may cause the computer 1200 to perform a process or steps of the process according to embodiments of the invention. Such programs may be executed by CPU 1212 to cause computer 1200 to perform certain operations associated with some or all of the blocks in the flowcharts and block diagrams described herein.

Computer 1200 according to this embodiment includes CPU 1212 and RAM 1214 , which are interconnected by host controller 1210 . Computer 1200 also includes a communication interface 1222 and an input/output unit, which are connected to host controller 1210 via input/output controller 1220 . Computer 1200 also includes ROM 1230 . The CPU 1212 operates according to programs stored in the ROM 1230 and RAM 1214, thereby controlling each unit.

Communication interface 1222 communicates with other electronic devices over a network. A hard disk drive may store programs and data used by CPU 1212 in computer 1200 . ROM 1230 stores therein programs that are dependent on the hardware of computer 1200, such as a boot program that is executed by computer 1200 upon activation. The program is provided via a computer-readable recording medium such as CR-ROM, USB memory or IC card or network. The program is installed in RAM 1214 or ROM 1230 , which are also examples of computer-readable recording media, and executed by CPU 1212 . The information processing described within these programs is read by computer 1200 to provide coordination between the programs and the various types of hardware resources described above. An apparatus or method may be configured by implementing information operations or processing according to the use of computer 1200 .

For example, when communication is performed between the computer 1200 and an external device, the CPU 1212 executes a communication program loaded into the RAM 1214 and sends communication processing to the communication interface 1222 based on the processing described in the communication program. you can command. The communication interface 1222, under the control of the CPU 1212, reads the transmission data stored in the transmission buffer area provided in the RAM 1214 or a recording medium such as a USB memory, transmits the read transmission data to the network, or Received data received from a network is written in a receive buffer area or the like provided on a recording medium.

The CPU 1212 also causes the RAM 1214 to read all or a necessary portion of a file or database stored in an external storage medium such as a USB memory, and performs various types of processing on the data on the RAM 1214. good. CPU 1212 may then write back the processed data to an external recording medium.

Various types of information, such as various types of programs, data, tables, and databases, may be stored on recording media and subjected to information processing. CPU 1212 performs various types of operations on data read from RAM 1214, information processing, conditional decisions, conditional branching, unconditional branching, and information retrieval, which are described throughout this disclosure and are specified by instruction sequences of programs. Various types of processing may be performed, including /replace, etc., and the results written back to RAM 1214 . In addition, the CPU 1212 may search for information in a file in a recording medium, a database, or the like. For example, if a plurality of entries each having an attribute value of a first attribute associated with an attribute value of a second attribute are stored in the recording medium, the CPU 1212 determines that the attribute value of the first attribute is specified. search the plurality of entries for an entry that matches the condition, read the attribute value of the second attribute stored in the entry, and thereby associate it with the first attribute that satisfies the predetermined condition. an attribute value of the second attribute obtained.

The programs or software modules described above may be stored in a computer-readable storage medium on or near computer 1200 . Also, a recording medium such as a hard disk or RAM provided in a server system connected to a dedicated communication network or the Internet can be used as a computer-readable storage medium, whereby the program can be transferred to the computer 1200 via the network. offer.

The execution order of each process such as actions, procedures, steps, and stages in the devices, systems, programs, and methods shown in the claims, the specification, and the drawings is etc., and it should be noted that they can be implemented in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the specification, and the drawings, even if the description is made using "first," "next," etc. for convenience, it means that it is essential to carry out in this order. not a thing

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the description of the scope of claims that forms with such modifications or improvements can also be included in the technical scope of the present invention.

10 Master Devices 11, 21 Antenna 12 Drive Circuit 13 Amplifier Circuit 14 Calculation Circuit 20 SAW Sensor 22 Surface Acoustic Wave Element 100 Temperature Measurement System 221 Piezoelectric Substrate 222 IDT Electrodes 222a, 222b Comb-toothed Electrode 223 Reflective Electrode 1200 Computer 1210 Host Controller 1212 CPU
1214 RAM
1220 input/output controller 1222 communication interface 1230 ROM

Claims (10)

The time from when the drive signal is transmitted via the communication unit until when the response signal to the drive signal transmitted from the surface acoustic wave sensor driven by receiving the drive signal is received via the communication unit. an acquisition unit that acquires time information indicating
A physical quantity derivation device, comprising: a derivation unit for deriving a physical quantity of an object based on the time information when a rate of change of time indicated by the time information is within a predetermined rate of change range. The derivation unit is
When the time change rate indicated by the time information is within a predetermined change rate range and the SN ratio of the response signal is greater than a first SN ratio, the physical quantity of the object is derived based on the time information. The physical quantity derivation device according to claim 1, wherein The derivation unit is
a change rate of time indicated by the time information is within a predetermined change rate range, an SN ratio of the response signal is greater than a first SN ratio, and the time indicated by the time information is within the predetermined time range 2. The physical quantity derivation device according to claim 1, wherein if there is, the physical quantity of said object is derived based on said time information. The acquisition unit
further acquiring phase difference information indicating a phase difference between the drive signal and the response signal;
The derivation unit is
The time change rate indicated by the time information is within a predetermined change rate range, the SN ratio of the response signal is greater than a first SN ratio, and the time indicated by the time information is within the predetermined time range. 2. The physical quantity according to claim 1, wherein the physical quantity of the object is derived based on the time information and the phase difference information when the phase difference indicated by the phase difference information is within a predetermined phase difference range. Derivation device. The derivation unit is
Even if the time indicated by the time information is not within the predetermined time range, the rate of change of the time indicated by the time information is within the predetermined rate of change range, and the SN ratio of the response signal is the first. when the phase difference indicated by the phase difference information indicating the phase difference between the drive signal and the response signal is within a predetermined phase difference range, based on the phase difference information 5. The physical quantity derivation device according to claim 4, wherein the physical quantity of the object is derived by using the physical quantity. The derivation unit is
Even if the phase difference indicated by the phase difference information is not within the predetermined phase difference range, the time change rate indicated by the time information is within the predetermined change rate range, and the SN ratio of the response signal is greater than a second SN ratio that is greater than the first SN ratio, and the time indicated by the time information is within a predetermined time range, the physical quantity of the object is derived based on the time information. 5. The physical quantity derivation device according to 4. The derivation unit is
A physical quantity of the object is derived based on the time information, and when a rate of change of the physical quantity of the object based on the time information is within a predetermined rate of change range, the rate of change of the time indicated by the time information is 7. The physical quantity derivation device according to any one of claims 1 to 6, which determines that the change rate is within a predetermined change rate range. a physical quantity derivation device according to any one of claims 1 to 7;
A physical quantity derivation system comprising the surface acoustic wave sensor. The time from when the drive signal is transmitted via the communication unit until when the response signal to the drive signal transmitted from the surface acoustic wave sensor driven by receiving the drive signal is received via the communication unit. obtaining time information indicative of
and deriving a physical quantity of an object based on the time information when the time change rate indicated by the time information is within a predetermined range. The time from when the drive signal is transmitted via the communication unit until when the response signal to the drive signal transmitted from the surface acoustic wave sensor driven by receiving the drive signal is received via the communication unit. obtaining time information indicative of
and deriving a physical quantity of an object based on the time information when the time change rate indicated by the time information is within a predetermined range.

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