Temperature measurement device

Abstract

A temperature measurement device includes: a signal transmission and reception unit (1) including a first antenna (8) and a signal processing unit (3); and a sensor unit (2) including a second antenna (5) and a temperature detection element (4). The temperature detection element (4) has a resonance characteristic in which the resonance frequency (x*(Θ)) changes according to the temperature (Θ) of a measurement object, and transmits response radio waves, reflecting the resonance frequency (x*(Θ)), via the second antenna (5) while receiving, via the second antenna (5), transmission radio waves transmitted from the first antenna (8). The signal processing unit (3) receives the response radio waves via the first antenna (8) while generating the transmission radio waves, calculates an estimated value of the resonance frequency (x*(Θ)) of the temperature detection element (4) on the basis of the signal strength (Ai) of the response radio waves for each of the transmission radio waves of at least two different transmission frequencies (xi-xi-1), and controls the transmission frequency (xi+1) on the basis of the estimated value of the resonance frequency (x*(Θ)).

Description

Temperature measurement device

[0001] The present disclosure relates to a temperature measurement device.

[0002] A temperature measurement device has been proposed that includes a sensor unit placed on a measurement target and a signal transmitting / receiving unit placed away from the sensor unit (see, for example, Patent Document 1). This signal transmitting / receiving unit transmits an excitation signal (transmission radio wave) consisting of a burst wave of a predetermined frequency to the sensor unit during a transmission period, receives a reception signal from the sensor unit during a reception period after the transmission period, detects a resonance reverberation signal generated by the excitation signal from the reception signal, detects temperature as a physical quantity from the resonance frequency of the resonance reverberation signal, and reduces the signal strength of the excitation signal when the signal strength of the resonance reverberation signal is higher than a threshold.

[0003] International Publication No. 2014 / 129071

[0004] However, in the above-mentioned conventional temperature measurement device, an excitation signal is transmitted during a transmission period, a reception signal is received during a reception period, and a resonance reverberation signal is detected from the reception signal, which requires that the transmission period and the reception period be separated, making it impossible to accurately measure the temperature of a measurement object whose temperature fluctuates in a short period of time.

[0005] An object of the present disclosure is to provide a temperature measuring device that can accurately measure the temperature of a measurement target.

[0006] The temperature measuring device disclosed herein comprises a signal transmitting / receiving unit having a first antenna and a signal processing unit, and a sensor unit having a second antenna and a temperature measuring element, wherein the temperature measuring element has a resonance characteristic in which the resonance frequency changes depending on the temperature of the object to be measured, and receives a transmission radio wave transmitted from the first antenna via the second antenna while transmitting a response radio wave reflecting the resonance frequency via the second antenna, and the signal processing unit receives the response radio wave via the first antenna while generating the transmission radio wave, calculates an estimate of the resonance frequency of the temperature measuring element based on the signal strength of the response radio wave for each of the transmission radio waves of two or more different transmission frequencies, and controls the transmission frequency based on the estimate of the resonance frequency.

[0007] According to the device of the present disclosure, the temperature of the measurement object can be accurately measured.

[0008] 7 is a functional block diagram showing the configuration of a temperature measurement device according to an embodiment. FIG. 8 is a diagram showing an example of the hardware configuration of a signal transmitting and receiving unit of a temperature measurement device according to an embodiment. FIG. 9 is a diagram showing that the resonance characteristics of a sensor unit change depending on the temperature. (A) is a diagram showing an example of the temperature characteristic of the resonance frequency of a temperature measuring element of a sensor unit, and (B) is a diagram showing that the temperature conversion unit of the signal transmitting and receiving unit can estimate the temperature of a measurement target by calculating the temperature from an estimated value of the resonance frequency of the sensor unit. (A) and (B) are diagrams showing the operation of a temperature measurement device of a comparative example. (A) and (B) are diagrams showing the operation of a temperature measurement device according to an embodiment. (A) is a flowchart showing the operation of a temperature measurement device according to an embodiment. (A) is a diagram showing the processing of steps S1 to S3 of FIG. 7. (A) and (B) are diagrams showing an example of a method for calculating an estimated value of a resonance frequency. (A) and (B) are diagrams showing the processing of step S5 of FIG. 7. (A) to (C) are diagrams showing another example of a method for estimating a resonance frequency. (A) is a diagram showing an example of a calculation of a differential characteristic of the resonance characteristics. (B) is a diagram showing another example of a calculation of a differential characteristic of the resonance characteristics. 8A and 8B are diagrams showing an example of setting the frequency of the transmission radio wave in step S7 of Fig. 7. 8A to 8C are diagrams showing another example of setting the frequency of the transmission radio wave in step S7 of Fig. 7. 8A to 8C are diagrams showing another example of setting the frequency of the transmission radio wave in step S7 of Fig. 7.

[0009] Hereinafter, a temperature measuring device according to an embodiment will be described with reference to the drawings. The following embodiments are merely examples, and each embodiment can be modified as appropriate.

[0010] 1 is a functional block diagram showing the configuration of a temperature measuring device according to an embodiment. The temperature measuring device according to the embodiment is composed of a signal transmitting / receiving unit 1 having a first antenna 8 and a signal processing unit 3, and a sensor unit 2 having a second antenna 5 and a temperature measuring element 4. The temperature measuring element 4 is, for example, a quartz crystal oscillator. The signal transmitting / receiving unit 1 is disposed apart from the sensor unit 2. The signal transmitting / receiving unit 1 transmits a transmission radio wave to the sensor unit 2, receives a response radio wave from the sensor unit 2, and converts (calculates) the temperature Θ of the object to be measured based on the response radio wave.

[0011] The sensor unit 2 is placed on or inside the object to be measured. The sensor unit 2 (particularly the temperature measuring element 4) is placed in contact with the device whose temperature is to be measured, for example. The device to be measured is, for example, a moving device, a device in which temperature changes occur in a short period of time, or a device that requires instantaneous measurement of temperature changes. A specific example of the device to be measured is the rotor of a motor.

[0012] The temperature measuring element 4 has a resonant frequency x according to the temperature Θ of the object to be measured. ＊ The temperature measuring element 4 has a resonance characteristic in which the resonance frequency x (Θ) changes while receiving the transmission radio wave (excitation signal) transmitted from the first antenna 8 of the signal transmitting / receiving unit 1 via the second antenna 5. ＊ The response radio wave reflecting the resonance frequency x (Θ) is transmitted via the second antenna 5. The signal strength distribution of the response radio wave is ＊ Since the peak value is at (Θ), the response radio wave has a resonant frequency x ＊ (Θ) is reflected.

[0013] The signal processing unit 3 has a frequency control unit 6, a transmission unit 7, a reception unit 9, a storage unit 10, a resonance frequency estimation unit 11, and a temperature conversion unit 12. In the signal processing unit 3, the transmission unit 7 generates a transmission radio wave, while the reception unit 9 receives a response radio wave via a first antenna 8. In the signal processing unit 3, the resonance frequency estimation unit 11 estimates two or more different transmission frequencies (for example, x ｉ , x ｉ－１ ) the signal strength (for example, A ｉ , A ｉ－１) based on which the resonance frequency x of the temperature measuring element 4 is calculated. ＊ Estimated (i.e., calculated) value of (Θ) Calculate.

[0014] In this application, the resonant frequency x ＊ Estimate of (Θ) to "x ＊～ ｉ " is also written.

[0015] The frequency control unit 6 controls the resonant frequency x ＊ The estimated value of (Θ) "x ＊～ ｉ ", the transmission frequency x of the next transmission wave to be transmitted ｉ＋１ The temperature conversion unit 12 controls the estimated value of the resonant frequency "x ＊～ ｉ ” and calculate the measured temperature.

[0016] The frequency control unit 6, the transmitting unit 7, the receiving unit 9, the memory unit 10, the resonant frequency estimation unit 11, and the temperature conversion unit 12 that constitute the signal processing unit 3 are functional blocks that represent the respective functions of the signal processing unit 3, and these functional blocks may be configured by a common processing circuit.

[0017] The signal transmitting / receiving unit 1 operates, for example, as follows: The signal transmitting / receiving unit 1 operates at a resonant frequency x ＊ A first frequency x less than (Θ) ｉ The transmitted radio wave and the resonant frequency x ＊ (Θ) a second frequency x greater than ｉ－１ and a transmission radio wave of the first frequency x ｉ The first signal strength A of the response radio wave from the sensor unit 2 in response to the transmitted radio wave ｉ and a second signal strength A of a response radio wave from the sensor unit 2 in response to the transmitted radio wave of the second frequency. ｉ－１ and determining a resonant frequency x based on the first frequency, the second frequency, the first signal strength, and the second signal strength. ＊ The estimated value of (Θ) "x ＊～ ｉ " and calculate the estimated value "x ＊～ ｉ " based on the first frequency x ｉ is the resonant frequency x＊ (Θ) and the second frequency x ｉ－１ is the resonant frequency x ＊ (Θ), and follow the temperature change of the measurement target, and the transmission frequency x ｉ＋１ Change it sequentially.

[0018] In addition, the signal transmission / reception unit 1 may periodically alternately transmit transmission radio waves of a first frequency and transmission radio waves of a second frequency, store the signal strength of the response radio waves of the sensor unit 2 to each of the transmission radio waves of the first frequency and the transmission radio waves of the second frequency, and calculate an estimated value of the resonant frequency of the temperature measuring element for each measurement by referring to the measurement results of the first frequency or the second frequency and the measurement results recorded in the memory unit 10.

[0019] In addition, the signal transmitting / receiving unit 1 may transmit a transmission radio wave of a first frequency lower than the resonant frequency, measure the first signal strength of the response radio wave from the sensor unit 2, estimate the difference between the first transmission frequency and the resonant frequency from the first signal strength based on the resonant characteristics of the temperature measuring element 4, and use the difference to calculate an estimated value of the resonant frequency.

[0020] In addition, the signal transmitting / receiving unit 1 may transmit a transmission radio wave of a second frequency greater than the resonant frequency, measure the second signal strength of the response radio wave from the sensor unit 2, estimate the difference between the second transmission frequency and the resonant frequency from the second signal strength based on the resonant characteristics of the temperature measuring element 4, and use the difference to calculate an estimated value of the resonant frequency.

[0021] In addition, the signal transmitting / receiving unit 1 may transmit a transmission radio wave of a first frequency to measure a first signal strength of the response radio wave of the sensor unit 2, transmit a transmission radio wave of a second frequency to measure a second signal strength of the response radio wave of the sensor unit 2, calculate the frequency difference between the first frequency and the second frequency and the signal strength difference between the first signal strength and the second signal strength, and calculate an estimated value of the resonant frequency by estimating the frequency difference between the first frequency or the second frequency or the center frequency of the first frequency and the second frequency and the resonant frequency from the signal strength difference based on the differential characteristics of the resonant characteristics of the temperature measuring element.

[0022] The signal transmitting / receiving unit 1 may transmit a transmission radio wave of a first frequency lower than the resonant frequency to measure a first signal strength of the response radio wave of the sensor unit 2, transmit a transmission radio wave of a second frequency higher than the resonant frequency to measure a second signal strength of the response radio wave of the sensor unit 2, calculate a first derivative from the frequency difference between the first frequency and the second frequency and the signal strength difference between the first signal strength and the second signal strength, and calculate an estimated value of the resonant frequency by estimating the frequency difference between the first frequency, the second frequency, or the center frequency of the first frequency and the second frequency from the first derivative based on the first derivative characteristic of the resonant characteristic of the temperature measuring element.

[0023] The signal transmitting / receiving unit 1 can change the first frequency to a value that is smaller than the estimated resonant frequency by a predetermined frequency based on the estimated resonant frequency of the temperature measuring element. Also, the signal transmitting / receiving unit 1 can change the second frequency to a value that is larger than the estimated resonant frequency by a predetermined frequency based on the estimated resonant frequency.

[0024] The signal transmitting / receiving unit 1 may operate to compare the estimated value of the resonant frequency with an average frequency, which is the average value of the first frequency and the second frequency, based on the estimated value of the resonant frequency, and if the estimated value is smaller than the average frequency, to decrease the first frequency or the second frequency by a predetermined frequency, or if the estimated value is larger than the average frequency, to increase the first frequency or the second frequency by the predetermined frequency.

[0025] The signal transmitting / receiving unit 1 may convert the resonant frequency into temperature using a conversion table or conversion formula prepared in advance and stored in the memory unit 10, record the temperature data in chronological order, perform a smoothing process using a low-pass filter, and output the smoothed temperature data.

[0026] The signal transmission / reception unit 1 may receive information regarding the heating and cooling of the object to be measured as a control input, predict the amount of temperature change in the object to be measured, and predict the range of the amount of frequency change, thereby controlling the change in the frequency update amount of the transmitted radio waves.

[0027] The signal transmitting / receiving unit 1 may have a function to send an alert to the outside using sound, light, display screen, etc. when the calculated temperature is equal to or higher than a predetermined first threshold, or equal to or lower than a predetermined second threshold, or when the temperature is equal to or higher than the predetermined first threshold and equal to or lower than the predetermined second threshold.

[0028] 2 is a diagram showing an example of the hardware configuration of a signal transmitting and receiving unit 1 of a temperature measuring device according to an embodiment. The signal transmitting and receiving unit 1 includes a processor 101 such as a CPU (Central Processing Unit) that executes a program, a memory 102 as a storage device, a non-volatile storage device 103, a transmitter 7, and a receiver 9. The signal transmitting and receiving unit 1 may also be configured with a processing circuit such as a single circuit, a composite circuit, or an FPGA (Field Programmable Gate Array). When the signal transmitting and receiving unit 1 is configured with a processing circuit, the processing circuit may include the processor 101 and a memory 102 that stores the program executed by the processor 101.

[0029] The storage device 103 is a storage such as a hard disk drive (HDD) or a solid state drive (SSD), etc. The memory 102 is a semiconductor memory such as a random access memory (RAM).

[0030] 3 is a diagram showing that the resonance characteristics of the sensor unit 2 change depending on the temperature Θ of the temperature measuring element 4 (i.e., the temperature of the object to be measured). The temperature measuring element 4 of the sensor unit 2 changes in resonance frequency x ＊ (Θ) has the property of changing.

[0031] When a transmission radio wave is transmitted from the first antenna 8 of the signal transmitting / receiving unit 1 to the second antenna 5 of the sensor unit 2, a response radio wave is reflected from the sensor unit 2. The response radio wave has a signal strength distribution with resonance characteristics according to the temperature Θ of the measurement object. In the signal transmitting / receiving unit 1, the receiver 9 receives the response radio wave from the sensor unit 2 via the first antenna 8 and calculates the signal strength or quadrature phase amplitude.

[0032] Figure 3 shows the temperature of the object to be measured.１ The resonance characteristics of the sensor unit 2 when ＊ (Θ １ ) and the temperature Θ is Θ ２ The resonance characteristics of the sensor unit 2 when ＊ (Θ ２ ) ). Here, the resonance characteristic refers to the distribution of signal strength [a.u.] when a transmission radio wave of each frequency is transmitted from the signal transmitting / receiving unit 1 and a response radio wave reflected from the sensor unit 2 is received by the signal transmitting / receiving unit 1. As shown in FIG. 3, the resonance frequency x of the sensor unit 2 changes depending on the temperature Θ of the measurement object. ＊ (Θ) changes. In each figure, a.u. indicates arbitrary unit.

[0033] FIG. 4A shows the resonance frequency x of the temperature measuring element 4 of the sensor unit 2. ＊ 4A is a diagram showing an example of the temperature characteristic of the temperature Θ. １ The resonant frequency when ＊ (Θ １ ) and the temperature Θ is Θ ２ When the resonant frequency rises to x ＊ (Θ ２ )

[0034] FIG. 4B shows the temperature conversion unit 12 of the signal transmitting / receiving unit 1 estimating the resonance frequency of the sensor unit 2, “x ＊～ " to temperature (i.e., temperature conversion value) 10 is a diagram showing that the temperature of the measurement object to which the sensor unit 2 is attached can be estimated by calculating

[0035] In this application: , "Θ ～ " is also written.

[0036] 5A and 5B are diagrams showing the operation of the comparative temperature measuring device disclosed in Patent Document 1. In the comparative temperature measuring device, a transmission signal is transmitted from the signal transmitting / receiving unit to the sensor unit between time 0 and time T, and the signal transmitting / receiving unit calculates the resonant frequency x based on the intensity of the reverberation signal, which is a response radio wave from the sensor unit, between time T and time 2T. ＊ Subsequently, between times 2T and 3T, the signal transmitting / receiving unit transmits a transmission signal to the sensor unit, and between times 3T and 4T, the signal transmitting / receiving unit estimates the resonant frequency x based on the intensity of the reverberation signal, which is a response radio wave from the sensor unit. ＊ The estimated value x ＊～ In this way, in the comparative example, the transmission period and the reception period are set separately, so the resonant frequency x is calculated at an interval of 2T, which is the total time of the transmission period and the reception period. ＊ Estimate.

[0037] 6A and 6B are diagrams illustrating the operation of the temperature measuring device according to the embodiment. In the temperature measuring device according to the embodiment, a transmission signal is transmitted from the signal transmitting / receiving unit 1 to the sensor unit 2 between times 0 and T, and the signal transmitting / receiving unit 1 calculates the resonant frequency x based on the intensity of the response radio wave from the sensor unit 2 between times T and 2T. ＊ The estimated value of "x ＊～ １ Then, between time T and 2T, the signal transmitting / receiving unit 1 transmits a transmission signal to the sensor unit 2, and between time 2T and 3T, the signal transmitting / receiving unit 1 calculates the resonance frequency x ＊ The estimated value "x ＊～ ２ Then, between times 2T and 3T, the signal transmitting / receiving unit transmits a transmission signal to the sensor unit, and between times 3T and 4T, the signal transmitting / receiving unit calculates the resonant frequency x ＊ The estimated value "x ＊～ ３ In this way, in the temperature measuring device according to the embodiment, the resonant frequency x ＊In addition, the resonant frequency of the temperature measuring device according to the embodiment is estimated using a transient response signal rather than a reverberation signal of the sensor unit 2.

[0038] 7 is a flowchart showing the operation of the temperature measuring device according to the embodiment. In step S1, the signal processing unit 3 of the signal transmitting / receiving unit 1 first sets the variable i representing the measurement number to 0, and then sets the frequency x of the transmitted radio wave. ｉ The predetermined initial value frequency x ０ , x １ Set.

[0039] In step S2, the signal processing unit 3 of the signal transmitting / receiving unit 1 receives the frequency x ０ , x １ The signal strength A of the response radio wave from the sensor unit 2 in response to the transmitted radio wave ０ , A １ Measure.

[0040] In step S3, the signal processing unit 3 of the signal transmitting / receiving unit 1 sets the frequency of the transmission radio wave to frequency x １ Set.

[0041] In loop L1 (start), the signal processing unit 3 of the signal transmitting / receiving unit 1 increments the variable i by 1 (i←i+1) and executes steps S4 to S7.

[0042] In step S4, the signal processing unit 3 of the signal transmitting / receiving unit 1 receives the transmission frequency x ｉ The signal strength A of the response radio wave from the sensor unit 2 in response to the transmitted radio wave ｉ Measure.

[0043] In step S5, the signal processing unit 3 of the signal transmitting / receiving unit 1 calculates the current measurement result (x ｉ , A ｉ ) and the previous measurement result (x ｉ－１ , A ｉ－１ ) and the estimated value "x ＊～ ｉ ”Calculate.

[0044] In step S6, the signal processing unit 3 of the signal transmitting / receiving unit 1 calculates the estimated value “x＊～ ｉ "Temperature In this application, the temperature is "Θ ～ ｉ " is also written.

[0045] In step S7, the signal processing unit 3 of the signal transmitting / receiving unit 1 calculates the estimated value of the resonant frequency “x ＊～ ｉ " and the frequency of the transmitted radio wave x ｉ and x ｉ－１ So, the frequency of the next transmission radio wave is x ｉ＋１ Thereafter, the process returns to loop L1 (start), and steps S4 to S7, which are the process of loop L1, are repeated until an end command is received.

[0046] 8 is a diagram showing the processing of steps S1 to S3 in FIG. 7. First, the signal processing unit 3 sweeps the frequency x of the transmission radio wave in the frequency control unit 6, measures the resonance characteristic A(x) of the signal strength of the response radio wave, and calculates the resonance peak value A(x) which is the peak value of the strength distribution of the response signal. ＊ and half width at half maximum σ.

[0047] In step S1 of FIG. 7, the signal processing unit 3 of the signal transmitting / receiving unit 1 calculates an initial estimated value of the resonant frequency Based on this, the initial value x of the transmission frequency is set so that the first frequency is lower than the resonance frequency and the second frequency is higher than the resonance frequency. ０ and x １ In this application, the initial estimated value of the resonant frequency is determined. is "x ＊～ ０ " is also written.

[0048] The initial estimate of the resonant frequency, x ＊～ ０ " is, for example, the ambient temperature Θ measured by another temperature sensor. Ｅ The following resonance frequency calculated from the temperature characteristic of the resonance frequency of the sensor unit 2 (FIG. 4A) may be used:

[0049] Alternatively, the initial estimate of the resonant frequency "x ＊～ ０" may be the following resonance frequency calculated from the resonance characteristic A(x) obtained in advance.

[0050] Alternatively, if the resonance characteristic is a minimum characteristic, the initial estimated value of the resonance frequency "x ＊～ ０ " may be the following resonance frequency calculated from the resonance characteristic A(x) obtained in advance.

[0051] Furthermore, the signal processing unit 3 sets the initial value x of the transmission frequency ０ , x １ For example, the resonant frequency x ＊ Using (Θ) and the half width at half maximum of the resonance characteristic σ, it can be set as follows: x ０ = x ＊ (Θ)-σ x １ = x ＊ (Θ) + σ

[0052] The temperature Θ of the object to be measured changes over time, and the resonant frequency x ＊ (Θ) is also thought to change over time.

[0053] Therefore, the signal processing unit 3 calculates the estimated value of the resonant frequency "x ＊～ ｉ In order to accurately calculate ", the value of the transmission frequency is set in the region where the slope of the resonance characteristic is steep, that is, two frequencies (x ＊ +σ) and (x ＊ The frequency control unit 6 updates the first frequency and the second frequency so that they become values ​​close to (−σ) (step S4 and subsequent steps). In a region where the slope of the resonance characteristics is steep, the change in signal strength is large relative to the change in frequency, so it is easy to estimate the change in frequency from the change in measured signal strength.

[0054] 9A and 9B show the estimated value of the resonant frequency "x" in step S5 of FIG. ＊～ ｉ 9A is a diagram showing an example of a method for calculating the estimated value "x" of the resonant frequency from the first frequency. ＊～ ｉ 9B shows an example of calculating the resonant frequency estimate "x" from the second frequency. ＊～ｉ 9A and 9B show an example of calculating the resonance characteristic of the maximum value.

[0055] In FIG. 9A, x ｉ <x ｉ－１ and x ｉ is the first frequency, and the resonant frequency x ＊ Since it is set to be sufficiently smaller than (Θ), the signal processing unit 3 ｉ ≦x ＊ (Θ), the estimated value of the resonant frequency "x ＊～ ｉ The signal processing unit 3 calculates the resonant frequency x ＊ (Θ) Based on the resonance characteristics on the lower frequency side, signal strength A ｉ From x ＊ (Θ) and x ｉ The frequency difference Δx<0 is calculated.

[0056] In FIG. 9B, x ｉ－１ <x ｉ and x ｉ is the second frequency, and the resonant frequency x ＊ Since the value is set to be sufficiently larger than (Θ), the signal processing unit 3 ＊ (Θ)≦x ｉ Assuming that the resonant frequency is estimated as "x ＊～ ｉ The signal processing unit 3 calculates the resonant frequency x ＊ (Θ) Based on the resonance characteristics on the higher frequency side, signal strength A ｉ From x ＊ (Θ) and x ｉ The frequency difference Δx>0 is calculated.

[0057] The estimated value of the resonant frequency "x ＊～ ｉ " is expressed by the following equation using the frequency difference Δx:

[0058] The following method can be used to calculate Δx. For example, if the resonance characteristic of the temperature measuring element 4 is a Lorentz function, the resonance characteristic can be calculated using the following formula: If we put it like this, A(x ＊ +Δx) = A ｉ The solution Δx is given by the following equation:

[0059] In this equation, x shown in FIG. ｉ <x ｉ－１ In the case of x, a negative solution is used, as shown in FIG. ｉ－１ <x ｉ If , use the positive answer.

[0060] 10A and 10B show the estimated value of the resonant frequency "x" in step S5 of FIG. ＊～ ｉ 10A shows an example of calculating an estimated value of the resonance frequency from a first frequency, and FIG. 10B shows an example of calculating an estimated value of the resonance frequency from a second frequency. FIGS. 10A and 10B show the case where the resonance characteristic is a minimum characteristic. FIGS. 10A and 10B are the same as FIGS. 9A and 9B, which show the case where the resonance characteristic is a maximum characteristic, except that they show the case where the resonance characteristic is a minimum characteristic.

[0061] 11A to 11C are diagrams showing another example of a method for estimating a resonant frequency, where Fig. 11A shows signal strength measurement, Fig. 11B shows differential characteristics of the resonant characteristics, and Fig. 11C shows estimation of the resonant frequency.

[0062] As shown in FIG. 11A, the signal processing unit 3 outputs the (i-1)th measurement result (x ｉ－１ , A ｉ－１ ) and the i-th measurement result (x ｉ , A ｉ The signal processing unit 3 obtains the frequency difference w and the signal strength difference ΔA ｉ and are calculated respectively. w indicates the half width of the frequency difference, and is calculated by the following formula:

[0063]

[0064] The signal strength difference ΔA is calculated by the following formula: ｉ = A ｉ -A ｉ－1

[0065] FIG. 11B shows an example of calculating the frequency difference Δx from the differential characteristic B(x; w) of the resonance characteristics.

[0066] FIG. 11(C) shows the calculated Δx and average frequency. From this, the resonance frequency is estimated using the following formula:

[0067]

[0068] 12 is a diagram showing an example of calculation of the difference characteristic B(x; w) of the resonance characteristic. If the resonance characteristic previously obtained in step S1 is denoted by A(x), when the resonance characteristic is a Lorentz function, the resonance characteristic is expressed by the following equation.

[0069]

[0070] As a differential characteristic, the detuning ξ is expressed by the following equation: ξ=x−x ＊

[0071] The differential characteristic B(x; w) is defined as follows using the detuning ξ:

[0072] The following formula Solving this, we obtain the solution ξ=Δx.

[0073] 13 is a diagram showing another example of the calculation of the differential characteristic of the resonance characteristic. As an approximate calculation method of Δx, there is a method of linearizing the differential characteristic at the origin (resonance point). If the slope of B(ξ; w) at the origin is "a", the following equation is established.

[0074]

[0075] Also, and solve the linearly approximated equation to get the solution Δx may be calculated approximately as follows:

[0076] In addition, as a solution using differential coefficients, the following equation Using The solution ξ=Δx may be calculated by solving an equation that approximates the first derivative.

[0077] 14A and 14B are diagrams showing an example of setting the frequency of the transmission radio wave in step S7 of FIG. 7. FIGS. 14A and 14B show the case where the resonance characteristic is a maximum characteristic. ｉ <x ｉ－１ , and FIG. 14B shows the case of x ｉ－１ <x ｉ This shows the case.

[0078] In step S7 of FIG. 7, the estimated value of the resonant frequency and the frequency of the transmitted radio wave x ｉ , x ｉ－１ From the relationship, the frequency of the next transmission radio wave x ｉ＋１ Set.

[0079] When δ is a predetermined frequency update amount, x ｉ <x ｉ－１ Then, the frequency of the transmitted radio wave x is as follows: ｉ＋１ Set.

[0080]

[0081] When δ is a predetermined frequency update amount, x ｉ－１ <x ｉ Then, the frequency of the transmitted radio wave x is as follows: ｉ＋１ Set.

[0082]

[0083] Figures 15(A) to (C) and Figures 16(A) to (C) are diagrams showing other examples of setting the frequency of the transmission radio wave in step S7 of Figure 7. Figures 15(A) to (C) and Figures 16(A) to (C) show the case where the resonance characteristic is a maximum characteristic.

[0084] Estimated resonant frequency and the frequency of the transmitted radio wave x ｉ , x ｉ－１ From the relationship, the frequency of the next transmission radio wave x ｉ＋１ Let δ be a predetermined frequency update amount, x ｉ , x ｉ－１ When the average frequency is , the average value is expressed by the following formula.

[0085]

[0086] Then, x ｉ＋１ = x ｉ－１ It is −δ.

[0087] Then, x ｉ＋１ = x ｉ－１ is.

[0088] Then, x ｉ＋１ = x ｉ－１ +δ.

[0089] In this method, the transmitted radio wave is updated in δ steps, which simplifies the configuration of the transmitter 7. For example, the predetermined frequency update amount δ may be set to δ=σ / 10.

[0090] As described above, the temperature measurement device according to the embodiment can measure the transient temperature response of an object. Furthermore, since the time required for one temperature estimation can be shortened, it is possible to measure the transient temperature response of an object whose temperature changes over time in a short period of time.

[0091] Furthermore, even if the resonant frequency of the temperature measuring element 4 changes due to a change in the temperature of the object to be measured, the resonant frequency at the current time can be estimated.

[0092] Furthermore, since the resonant frequency is estimated from the difference between the two signal strengths, it is possible to cancel out fluctuations in the signal strength offset (low frequency noise) of the receiving unit, improving the accuracy of estimating the resonant frequency.

[0093] Furthermore, since the transmission frequency is successively changed to a value suitable for estimating the resonance frequency, the accuracy of temperature measurement is improved.

[0094] REFERENCE SIGNS LIST 1 signal transmitting / receiving unit, 2 sensor unit, 3 signal processing unit, 4 temperature measuring element, 5 second antenna, 6 frequency control unit, 7 transmitting unit, 8 first antenna, 9 receiving unit, 10 storage unit, 11 resonance frequency estimation unit, 12 temperature conversion unit, Θ temperature, x ＊ (Θ) Resonant frequency.

Claims

1. A temperature measuring device comprising: a signal transmitting / receiving unit having a first antenna and a signal processing unit; and a sensor unit having a second antenna and a temperature measuring element, wherein the temperature measuring element has a resonance characteristic in which the resonance frequency changes depending on the temperature of the object to be measured, and while receiving a transmission radio wave transmitted from the first antenna via the second antenna, transmits a response radio wave reflecting the resonance frequency via the second antenna, and the signal processing unit receives the response radio wave via the first antenna while generating the transmission radio wave, calculates an estimate of the resonance frequency of the temperature measuring element based on the signal strength of the response radio wave for each of the transmission radio waves of two or more different transmission frequencies, and controls the transmission frequency based on the estimate of the resonance frequency.

2. The temperature measuring device according to claim 1, wherein the signal transmitting / receiving unit: transmits a transmission radio wave of a first frequency lower than the resonant frequency and a transmission radio wave of a second frequency higher than the resonant frequency; measures a first signal strength of a response radio wave from the sensor unit to the transmission radio wave of the first frequency and a second signal strength of a response radio wave from the sensor unit to the transmission radio wave of the second frequency; calculates the estimated value of the resonant frequency based on the first frequency, the second frequency, the first signal strength, and the second signal strength; sets the first frequency to be lower than the resonant frequency and the second frequency to be higher than the resonant frequency based on the estimated value; and sequentially changes the transmission frequency in accordance with temperature changes of the object to be measured.

3. The temperature measuring device described in claim 2, characterized in that the signal transmitting / receiving unit periodically alternately transmits radio waves of the first frequency and radio waves of the second frequency, stores the signal strength of the response radio waves from the sensor unit for each of the transmitted radio waves of the first frequency and the transmitted radio waves of the second frequency, and calculates an estimate of the resonant frequency of the temperature measuring element for each measurement by referring to the measurement results of the first frequency or the second frequency and the measurement results recorded in the memory unit.

4. The temperature measuring device described in claim 1, characterized in that the signal transmitting / receiving unit transmits a transmission radio wave of a first frequency lower than the resonant frequency, measures a first signal strength of a response radio wave from the sensor unit, estimates a difference between the first transmission frequency and the resonant frequency from the first signal strength based on the resonance characteristics of the temperature measuring element, and calculates the estimated value of the resonant frequency using the difference.

5. The temperature measuring device described in claim 1, characterized in that the signal transmitting / receiving unit transmits a transmission radio wave of a second frequency higher than the resonant frequency, measures a second signal strength of the response radio wave from the sensor unit, estimates the difference between the second transmission frequency and the resonant frequency from the second signal strength based on the resonance characteristics of the temperature measuring element, and calculates the estimated value of the resonant frequency using the difference.

6. The temperature measuring device according to claim 2, characterized in that the signal transmitting / receiving unit: transmits a transmission radio wave of the first frequency to measure a first signal strength of a response radio wave from the sensor unit; transmits a transmission radio wave of the second frequency to measure a second signal strength of the response radio wave from the sensor unit; calculates a frequency difference between the first frequency and the second frequency and a signal strength difference between the first signal strength and the second signal strength; and calculates the estimated value of the resonant frequency by estimating a frequency difference between the resonant frequency and the center frequency of the first frequency or the second frequency or the first frequency and the second frequency from the signal strength difference based on the differential characteristic of the resonant characteristic of the temperature measuring element.

7. The temperature measuring device according to claim 2, characterized in that the signal transmitting / receiving unit: transmits a transmission radio wave of a first frequency lower than the resonant frequency to measure a first signal strength of a response radio wave of the sensor unit; transmits a transmission radio wave of a second frequency higher than the resonant frequency to measure a second signal strength of the response radio wave of the sensor unit; calculates a first differential coefficient from the frequency difference between the first frequency and the second frequency and the signal strength difference between the first signal strength and the second signal strength; and calculates an estimate of the resonant frequency by estimating a frequency difference between the first frequency, the second frequency, or a center frequency of the first frequency and the second frequency from the first differential coefficient based on the first differential characteristic of the resonant characteristic of the temperature measuring element.

8. The temperature measuring device according to claim 2, characterized in that the signal transmitting / receiving unit changes the first frequency to a value that is a predetermined frequency smaller than the estimated value of the resonant frequency of the temperature measuring element based on the estimated value of the resonant frequency of the temperature measuring element.

9. The temperature measuring device according to claim 2, characterized in that the signal transmitting / receiving unit changes the second frequency to a value that is a predetermined frequency greater than the estimated value of the resonant frequency based on the estimated value of the resonant frequency.

10. The temperature measuring device described in claim 2, characterized in that the signal transmitting / receiving unit compares an average frequency, which is an average value of the first frequency and the second frequency, with the estimated value of the resonant frequency based on the estimated value of the resonant frequency, and if the estimated value is smaller than the average frequency, reduces the first frequency or the second frequency by a predetermined frequency, and if the estimated value is larger than the average frequency, increases the first frequency or the second frequency by a predetermined frequency.

11. The temperature measuring device according to claim 1, characterized in that the signal transmitting / receiving unit converts the resonant frequency into temperature using a conversion table or formula prepared in advance, records the temperature data in a time series, and smoothes the temperature data using a low-pass filter.

12. The temperature measuring device according to claim 8 or 9, characterized in that the signal transmitting / receiving unit receives information regarding heating / cooling of the object to be measured as a control input, predicts the amount of temperature change in the object to be measured, and predicts the range of the amount of change in frequency, thereby changing the amount of frequency update of the transmitted radio waves.

13. The temperature measuring device according to claim 1, characterized in that the signal transmitting / receiving unit transmits an alert to the outside when the calculated temperature is equal to or higher than a predetermined first threshold, or when the calculated temperature is equal to or lower than a predetermined second threshold, or when both the calculated temperature is equal to or higher than the predetermined first threshold and the calculated temperature is equal to or lower than a predetermined second threshold.

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