Offset Estimation Device and Offset Estimation Method

Abstract

To allow estimation of an offset of a propagation time difference of an ultrasonic wave more easily than before.SOLUTION: An offset estimation device includes: a prediction model acquisition unit 201 for acquiring a prediction model of each plural temperatures; an impedance feature point acquisition unit 202 for acquiring an impedance feature point in a pair of ultrasonic sensors 102 and 103 as offset estimation targets for the temperatures; and an offset calculation unit 203 for calculating the offset of the propagation time difference of ultrasonic waves in the ultrasonic sensors 102 and 103 for the temperatures by assigning the impedance feature point acquired by the impedance feature point acquisition unit 202 into a prediction model acquired by the prediction model acquisition unit 201.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an offset estimation device and an offset estimation method for estimating an offset of a propagation time difference of ultrasonic waves in an ultrasonic flowmeter.

Background Art

[0002] Conventionally, an ultrasonic flowmeter that measures the flow rate of a fluid to be measured based on the propagation time difference of ultrasonic waves transmitted and received by a pair of ultrasonic sensors is known (see, for example, Patent Document 1). In such an ultrasonic flowmeter, it is generally known that the propagation time difference (offset) when the flow rate is 0 is displaced from 0 due to the characteristic difference between a pair of ultrasonic sensors. In particular, the characteristics of a pair of ultrasonic sensors change due to temperature changes, and the propagation time difference also changes accordingly. Therefore, in order to correct the flow rate error associated with this characteristic change, it is necessary to measure the offset for each temperature and use the value for flow rate correction (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, conventionally, correction has been performed using the actually measured value of the offset for each temperature of the ultrasonic sensor. However, this operation requires a long time for correction because it is necessary to measure the offset when the temperature changes for each ultrasonic flowmeter.

[0005] As another method, there is a method of pairing two ultrasonic sensors so that their impedance characteristics match (the degree of matching is a correlation coefficient of 0.975 or more). By making the individual differences between the two ultrasonic sensors zero within the operating temperature range, changes in temperature characteristics will not occur either. However, regarding the pairing method to eliminate characteristic differences, the number of sensor pairs with impedance characteristics that match at all temperatures is limited, and not all ultrasonic sensors can be paired. Thus, in the production of ultrasonic flowmeters, many costs are incurred due to the yield.

[0006] This invention is made to solve the above problems, and an object thereof is to provide an offset estimation device that can simply estimate the offset of the propagation time difference of ultrasonic waves in an ultrasonic flowmeter compared to the prior art.

Means for Solving the Problems

[0007] The offset estimation device according to this invention Estimate the offset of the propagation time difference of ultrasonic waves in the pair of ultrasonic sensors from the impedance characteristic points in the pair of ultrasonic sensors is provided with a prediction model acquisition unit that acquires a prediction model, an impedance feature point acquisition unit that acquires impedance feature points of a pair of ultrasonic sensors whose offset is to be estimated for each temperature, and an offset calculation unit that calculates the offset of the propagation time difference of ultrasonic waves in a pair of ultrasonic sensors for each temperature by substituting the impedance feature points acquired by the impedance feature point acquisition unit into the prediction model acquired by the prediction model acquisition unit. for each of a plurality of temperatures for each temperature for each temperature

Advantages of the Invention

[0008] According to this invention, since it is configured as described above, it is possible to simply estimate the offset of the propagation time difference of ultrasonic waves in an ultrasonic flowmeter compared to the prior art.

Brief Description of the Drawings

[0009]

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Best Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Embodiment 1. FIG. 1 is a diagram showing a configuration example of the ultrasonic flowmeter 1 according to Embodiment 1. First, an example of the ultrasonic flowmeter 1 whose offset is estimated by the offset estimation device 2 will be described with reference to FIG. 1.

[0011] The ultrasonic flowmeter 1 measures a fluid using ultrasonic waves. As shown in FIG. 1, the ultrasonic flowmeter 1 includes a measurement tube 101, an ultrasonic sensor 102, an ultrasonic sensor 103, and an arithmetic unit 104.

[0012] The measurement tube 101 is a cylindrical member through which the fluid to be measured flows inside.

[0013] The ultrasonic sensor 102 is an ultrasonic transducer that is attached to the upstream side of the side wall of the measurement pipe 101 and transmits and receives ultrasonic waves with the ultrasonic sensor 103 within the measurement pipe 101. That is, the ultrasonic sensor 102 transmits ultrasonic waves to the downstream side (ultrasonic sensor 103) within the measurement pipe 101 and receives the ultrasonic waves from the downstream side (ultrasonic sensor 103) as a received signal.

[0014] The ultrasonic sensor 103 is an ultrasonic transducer that is attached to the downstream side of the side wall of the measurement pipe 101 and transmits and receives ultrasonic waves with the ultrasonic sensor 102 within the measurement pipe 101. That is, the ultrasonic sensor 103 transmits ultrasonic waves to the upstream side (ultrasonic sensor 102) within the measurement pipe 101 and receives the ultrasonic waves from the upstream side (ultrasonic sensor 102) as a received signal.

[0015] Note that the positional relationship between the ultrasonic sensor 102 and the ultrasonic sensor 103 is designed according to the propagation path of the ultrasonic waves used by the ultrasonic sensor 102 and the ultrasonic sensor 103.

[0016] The calculation unit 104 calculates the flow rate of the fluid within the measurement pipe 101 based on the transmission and reception results by the ultrasonic sensor 102 and the transmission and reception results by the ultrasonic sensor 103. At this time, the calculation unit 104 corrects the propagation time difference of the ultrasonic waves based on the offset estimated by the offset estimation device 2 and then calculates the flow rate of the fluid. The operating principle of the calculation unit 104 can adopt the principle of conventional flow rate calculation, and its explanation is omitted.

[0017] Note that the calculation unit 104 is realized by a processing circuit such as an IC (Integrated Circuit) or a system LSI (Large Scale Integration), or a CPU (Central Processing Unit) that executes a program stored in a memory or the like.

[0018] Next, a configuration example of the offset estimation device 2 will be described with reference to FIG. The offset estimation device 2 estimates the offset of the propagation time difference of ultrasonic waves in the ultrasonic flowmeter 1 (pair of ultrasonic sensors 102, 103). As shown in FIG. 2, this offset estimation device 2 includes a prediction model acquisition unit 201, an impedance feature point acquisition unit 202, and an offset calculation unit 203.

[0019] Note that the offset estimation device 2 is realized by a processing circuit such as a system LSI or a CPU that executes a program stored in a memory or the like.

[0020] The prediction model acquisition unit 201 acquires a prediction model for each of a plurality of temperatures. The prediction model is a model capable of estimating the offset of the propagation time difference of ultrasonic waves in the pair of ultrasonic sensors 102, 103 from the impedance feature points in the pair of ultrasonic sensors 102, 103. The impedance feature points in the pair of ultrasonic sensors 102, 103 are feature points obtained from the impedance characteristics (Z) in the pair of ultrasonic sensors 102, 103.

[0021] Note that the prediction model acquisition unit 201 may acquire data indicating a prediction model from an external device, or may acquire it by creating a prediction model by the prediction model acquisition unit 201. When the prediction model acquisition unit 201 creates a prediction model, the prediction model acquisition unit 201 creates a prediction model based on the impedance feature points in the pair of ultrasonic sensors 102, 103 and the measured values of the offsets of the propagation time differences of ultrasonic waves in the pair of ultrasonic sensors 102, 103 for each of the above temperatures. Note that the acquisition temperature of the above measured values is a part of the temperature range in which the pair of ultrasonic sensors 102, 103 are used.

[0022] The impedance feature point acquisition unit 202 acquires impedance feature points in a pair of ultrasonic sensors 102 and 103 for which offset is to be estimated, for each of the above temperatures. At this time, the impedance feature point acquisition unit 202 acquires impedance feature points at the same temperature as the temperature at which the measured values used in the creation of the prediction model acquired by the prediction model acquisition unit 201 were measured.

[0023] The offset calculation unit 203 substitutes the impedance feature points acquired by the impedance feature point acquisition unit 202 into the prediction model acquired by the prediction model acquisition unit 201, and calculates the offset of the propagation time difference of ultrasonic waves in the pair of ultrasonic sensors 102 and 103 for each of the above temperatures.

[0024] Further, the offset calculation unit 203 may estimate the offset in the operating temperature range of the pair of ultrasonic sensors 102 and 103 based on the calculated offset for each of the above temperatures. At this time, for example, the offset calculation unit 203 estimates the offset in the operating temperature range of the pair of ultrasonic sensors 102 and 103 by performing linear interpolation on the calculated offset for each of the above temperatures.

[0025] Next, an operation example of the offset estimation device 2 according to Embodiment 1 shown in FIG. 2 will be described with reference to FIG. 3. Hereinafter, a case where the prediction model acquisition unit 201 creates a prediction model and the offset calculation unit 203 estimates the offset in the operating temperature range of the pair of ultrasonic sensors 102 and 103 will be described.

[0026] In the operation example of the offset estimation device 2 according to Embodiment 1 shown in FIG. 2, as shown in FIG. 3, first, the prediction model acquisition unit 201 creates a prediction model for each of a plurality of temperatures (step ST301). At this time, the prediction model acquisition unit 201 creates a prediction model based on the impedance feature points in the pair of ultrasonic sensors 102 and 103 and the measured values of the offsets of the ultrasonic propagation time differences in the pair of ultrasonic sensors 102 and 103 for each of the above temperatures. Hereinafter, the creation of the prediction model by the prediction model acquisition unit 201 will be described more specifically.

[0027] First, the prediction model acquisition unit 201 determines, as impedance feature points, a part of the impedance characteristics in the ultrasonic sensors 102 and 103 necessary for acquiring the prediction model, or characteristic values obtained therefrom. For example, as shown in FIG. 4, the prediction model acquisition unit 201 acquires, as impedance feature points in the pair of ultrasonic sensors 102 and 103 (denoted as sensor 1 and sensor 2 in FIG. 4), the frequencies, impedance magnitudes, and phases at the four resonance frequencies (primary resonance frequency, primary anti-resonance frequency, secondary resonance frequency, and secondary anti-resonance frequency) in the pair of ultrasonic sensors 102 and 103, and the frequencies, impedance magnitudes, and phases at the three intermediate points among the four resonance frequencies. These impedance feature points can be obtained by measuring the impedance characteristics in the pair of ultrasonic sensors 102 and 103. Note that the measurement of the impedance characteristics is performed for each of any plurality of temperatures (measurement temperatures).

[0028] In addition, the prediction model acquisition unit 201 acquires the offset of the ultrasonic propagation time difference in the pair of ultrasonic sensors 102 and 103 measured at the same temperature as the measurement temperature.

[0029] Next, for each measured temperature, the prediction model acquisition unit 201 performs multiple regression analysis using the impedance feature points as explanatory variables (X) and the offset as the objective variable (Y) with the multiple regression analysis model shown in the following formula (1). At this time, the prediction model acquisition unit 201 performs multiple regression analysis using a sufficient number of data points to create a model, and obtains the regression coefficients a i (i = 0, 1, 2, ···), respectively. In the above example, for each measured temperature, the prediction model acquisition unit 201 substitutes the frequency, impedance magnitude, and phase (a total of 21 points) at the seven feature points, which are the impedance feature points, into the explanatory variable, which is the X term, and substitutes the offset into the objective variable, which is the Y term. TIFF0007716914000001.tif13166

[0030] Next, for each measured temperature, the prediction model acquisition unit 201 creates a prediction model shown in the following formula (2) based on multiple regression analysis. Then, by substituting the impedance feature points in the pair of ultrasonic sensors 102 and 103 to be estimated into this prediction model, the offset (offset estimated value) for the pair of ultrasonic sensors 102 and 103 can be calculated. In formula (2), the upstream ultrasonic sensor represents ultrasonic sensor 102, and the downstream ultrasonic sensor represents ultrasonic sensor 103. TIFF0007716914000002.tif21166

[0031] Note that the prediction model acquired by the prediction model acquisition unit 201 is not limited to the above. That is, the prediction model acquired by the prediction model acquisition unit 201 may be any model that can estimate the offset of the ultrasonic propagation time difference in the pair of ultrasonic sensors 102 and 103 based on the impedance feature points in the pair of ultrasonic sensors 102 and 103. The total number of impedance feature points used for the estimation, or the impedance feature points when various physical property values obtained from the impedance such as admittance are changed, the numerical values representing the graph shape, or the type of regression analysis used for creating the model formula may be different from the above.

[0032] Next, the impedance feature point acquisition unit 202 acquires impedance feature points in a pair of ultrasonic sensors 102 and 103 that are the estimation targets of the offset for each of the above temperatures (step ST302). At this time, the impedance feature point acquisition unit 202 acquires impedance feature points at the same temperature as the temperature at which the measured values used in the creation of the prediction model acquired by the prediction model acquisition unit 201 were measured.

[0033] Next, the offset calculation unit 203 substitutes the impedance feature points acquired by the impedance feature point acquisition unit 202 into the prediction model acquired by the prediction model acquisition unit 201, and calculates the offset of the propagation time difference of ultrasonic waves in the pair of ultrasonic sensors 102 and 103 for each of the above temperatures (step ST303).

[0034] Next, the offset calculation unit 203 estimates the offset in the operating temperature range of the pair of ultrasonic sensors 102 and 103 based on the calculated offset for each of the above temperatures (step ST304). At this time, for example, the offset calculation unit 203 estimates the offset in the operating temperature range of the pair of ultrasonic sensors 102 and 103 by performing linear interpolation on the calculated offset for each of the above temperatures.

[0035] Next, a specific example of the operation of the offset estimation device 2 according to Embodiment 1 shown in FIG. 2 will be described. For example, first, the prediction model acquisition unit 201 creates prediction models at -30°C, 25°C, and 60°C respectively based on the measured values of impedance feature points and offsets at -30°C, 25°C, and 60°C. Next, the impedance feature point acquisition unit 202 acquires impedance feature points in a pair of ultrasonic sensors 102 and 103 that are the estimation targets at -30°C, 25°C, and 60°C. Next, the offset calculation unit 203 substitutes the impedance feature points acquired by the impedance feature point acquisition unit 202 into the prediction model acquired by the prediction model acquisition unit 201, and calculates the offset of the propagation time difference at -30°C, 25°C, and 60°C. Then, the offset calculation unit 203 estimates the offset in the operating temperature range of the pair of ultrasonic sensors 102 and 103 by, for example, performing linear interpolation on the calculated offsets at -30°C, 25°C, and 60°C.

[0036] The data indicating the offset in the operating temperature range of the pair of ultrasonic sensors 102 and 103 is stored in the ultrasonic flowmeter 1 and used in actual flow measurement. That is, the ultrasonic flowmeter 1 extracts the offset corresponding to the temperature at the time of actual ultrasonic transmission and reception from the offsets in the operating temperature range of the pair of ultrasonic sensors 102 and 103, and corrects the propagation time difference. Thereby, the ultrasonic flowmeter 1 can obtain an ultrasonic flowmeter 1 that does not cause a flow rate error due to the temperature dependence of the offset without measuring the offsets in the operating temperature range of the pair of ultrasonic sensors 102 and 103, respectively.

[0037] Conventionally, the offsets in the operating temperature range of the pair of ultrasonic sensors 102 and 103 are each actually measured, and the values are used for correction. On the other hand, in the offset estimation device 2 according to the first embodiment, the offset is calculated from impedance characteristic points at any plurality of temperatures using a prediction model, and the offset in the operating temperature range of the pair of ultrasonic sensors 102 and 103 can be estimated from the calculated offset. Thereby, the offset estimation device 2 according to the first embodiment can estimate the offset more simply than in the prior art.

[0038] FIG. 5 shows the offset (estimated value) in the operating temperature range of the pair of ultrasonic sensors 102 and 103 obtained by the offset estimation device 2 according to the first embodiment. In FIG. 5, reference numeral 51 indicates the offset (estimated value), and reference numeral 52 indicates the offset after correction using the offset (estimated value).

[0039] As described above, according to the first embodiment, the offset estimation device 2 includes a prediction model acquisition unit 201 that acquires a prediction model for each of a plurality of temperatures, an impedance feature point acquisition unit 202 that acquires impedance feature points in a pair of ultrasonic sensors 102 and 103 whose offset is to be estimated for each of the temperatures, and an offset calculation unit 203 that calculates an offset of the propagation time difference of ultrasonic waves in the pair of ultrasonic sensors 102 and 103 for each of the temperatures by substituting the impedance feature points acquired by the impedance feature point acquisition unit 202 into the prediction model acquired by the prediction model acquisition unit 201. As a result, the offset estimation device 2 according to the first embodiment can easily estimate the offset of the ultrasonic wave propagation time difference as compared with the prior art.

[0040] Second Embodiment. In the offset estimation device 2 according to the first embodiment, after calculating the offsets at any plurality of temperatures, the case of estimating the offset in the operating temperature range of the pair of ultrasonic sensors 102 and 103 from those offsets was shown. On the other hand, in the offset estimation device 2 according to the second embodiment, after calculating the offsets at any plurality of temperatures, the case of detecting a pair of ultrasonic sensors 102 and 103 in which the offset does not depend on the temperature from those offsets is shown.

[0041] FIG. 6 is a diagram showing a configuration example of the offset estimation device 2 according to the second embodiment. In the offset estimation device 2 according to the second embodiment shown in this FIG. 6, the offset calculation unit 203 is changed to an offset calculation unit 203b with respect to the offset estimation device 2 according to the first embodiment shown in FIG. 2. Other configuration examples of the offset estimation device 2 according to the second embodiment shown in FIG. 6 are the same as those of the offset estimation device 2 according to the first embodiment shown in FIG. 2, and only the different parts are described with the same reference numerals.

[0042] Note that the impedance feature point acquisition unit 202 in the second embodiment acquires impedance feature points for each of the above temperatures (measurement temperatures) in a plurality of pairs of ultrasonic sensors 102 and 103 to be paired.

[0043] Similar to the offset calculation unit 203 in Embodiment 1, the offset calculation unit 203b substitutes the impedance feature points acquired by the impedance feature point acquisition unit 202 into the prediction model acquired by the prediction model acquisition unit 201, thereby calculating the offset of the propagation time difference of ultrasonic waves in the pair of ultrasonic sensors 102 and 103 for each of the above temperatures.

[0044] Further, the offset calculation unit 203b may determine whether the ultrasonic sensors 102 and 103 to be paired are ultrasonic sensors 102 and 103 that can be paired based on the calculated offset for each of the above temperatures. At this time, for example, the offset calculation unit 203b determines whether the variation range of the calculated offset for each of the above temperatures is within the allowable error range. The variation range of the offset is the difference between the maximum value and the minimum value of the offset. The allowable error range is a range that can be tolerated assuming that the offset does not change with temperature, and is set in advance. Then, when the offset calculation unit 203b determines that the variation range of the calculated offset for each of the above temperatures is within the allowable error range, it determines that the pair of ultrasonic sensors 102 and 103 from which the offset was obtained are ultrasonic sensors 102 and 103 that can be paired.

[0045] Next, an operation example of the offset estimation device 2 according to Embodiment 2 shown in FIG. 6 will be described with reference to FIG. 7. Hereinafter, a case where the prediction model acquisition unit 201 creates a prediction model and the offset calculation unit 203b determines whether the ultrasonic sensors 102 and 103 to be paired are ultrasonic sensors 102 and 103 that can be paired will be described. Among the operation examples of the offset estimation device 2 according to Embodiment 2 shown in FIG. 7, the processes of steps ST701 and 702 are the same as the processes of steps ST301 and 302 in the offset estimation device 2 in Embodiment 1 shown in FIG. 3, and the description thereof will be omitted.

[0046] In the operation example of the offset estimation device 2 according to the second embodiment shown in FIG. 6, as shown in FIG. 7, the offset calculation unit 203b substitutes the impedance feature points acquired by the impedance feature point acquisition unit 202 into the prediction model acquired by the prediction model acquisition unit 201, and calculates the offset of the propagation time difference of ultrasonic waves in the pair of ultrasonic sensors 102 and 103 for each of the above temperatures (measured temperatures) (step ST703).

[0047] Next, the offset calculation unit 203b determines whether the ultrasonic sensors 102 and 103 that are pairing targets are pairable ultrasonic sensors 102 and 103 based on the offsets calculated for each of the above temperatures (step ST704). At this time, for example, the offset calculation unit 203b determines whether the variation range of the offsets calculated for each of the above temperatures is within the allowable error range. Then, when the offset calculation unit 203b determines that the variation range of the offsets calculated for each of the above temperatures is within the allowable error range, it determines that the pair of ultrasonic sensors 102 and 103 from which the offset was obtained are pairable ultrasonic sensors 102 and 103.

[0048] Next, a specific example of the operation of the offset estimation device 2 according to the second embodiment shown in FIG. 6 will be described. For example, first, the prediction model acquisition unit 201 creates prediction models at -30°C, 25°C, and 60°C based on the measured values of impedance feature points and offsets at -30°C, 25°C, and 60°C respectively. Next, the impedance feature point acquisition unit 202 acquires the impedance feature points in the pair of ultrasonic sensors 102 and 103 that are pairing targets at -30°C, 25°C, and 60°C. Note that there are multiple pairs of ultrasonic sensors 102 and 103 that are pairing targets, and the impedance feature point acquisition unit 202 acquires the above impedance feature points for each pair. Next, the offset calculation unit 203b substitutes the impedance feature points acquired by the impedance feature point acquisition unit 202 into the prediction model acquired by the prediction model acquisition unit 201 to calculate the offsets of the propagation time differences at -30°C, 25°C, and 60°C. The offset calculation unit 203 calculates the above offsets for each pair of ultrasonic sensors 102 and 103 in each group. Then, for each group, the offset calculation unit 203b determines whether the variation ranges of the calculated offsets at -30°C, 25°C, and 60°C are within the allowable error range. And when the offset calculation unit 203b determines that the variation ranges of the offsets at -30°C, 25°C, and 60°C are within the allowable error range, it determines that the pair of ultrasonic sensors 102 and 103 from which the offset was obtained are pairable ultrasonic sensors 102 and 103.

[0049] Then, the operator designs the ultrasonic flowmeter 1 using the ultrasonic sensors 102 and 103 determined to be pairable by the offset calculation unit 203b. Also, the data indicating the offsets calculated by the offset calculation unit 203b is stored in the ultrasonic flowmeter 1 and used in actual flow measurement. That is, the ultrasonic flowmeter 1 corrects the propagation time difference using the offset at an arbitrary temperature (for example, 25° corresponding to room temperature) among the offsets calculated by the offset calculation unit 203. Thereby, with the ultrasonic flowmeter 1, an ultrasonic flowmeter 1 in which the offset does not change even when the temperature changes can be obtained.

[0050] Conventionally, by performing pairing such that the offsets of the propagation time differences become 0 at multiple temperatures, the temperature characteristics of the propagation time differences are made close to 0. In contrast, in the offset estimation device 2 according to the second embodiment, an offset is calculated from impedance feature points at any plurality of temperatures using a prediction model, and a pair of ultrasonic sensors 102 and 103 whose variation range of the offset at the plurality of temperatures is within the allowable error range is selected as a pairing target. As a result, in the offset estimation device 2 according to the second embodiment, even without pairing the temperature characteristics of the two ultrasonic sensors 102 and 103 to make the offset of the propagation time difference zero at each temperature, if offset correction is performed at one arbitrary temperature (for example, room temperature), an ultrasonic flowmeter 1 that does not require correction even when the temperature changes can be manufactured.

[0051] FIG. 8 shows the offsets (estimated values) at the pairable ultrasonic sensors 102 and 103 obtained by the offset estimation device 2 according to the second embodiment. In FIG. 8, reference numeral 81 indicates the offset (estimated value), reference numeral 82 indicates the offset (measured value), reference numeral 83 indicates the variation range of the offset (the difference between the maximum value and the minimum value of the offset for each temperature calculated by the offset calculation unit 203b), and reference numeral 84 indicates the offset (measured value) at a pair of ultrasonic sensors paired using the conventional method. In FIG. 8, for example, the allowable error range is set to 0.6 ns, and since the variation range of the offset indicated by reference numeral 81 is about 0.2 ns, the offset calculation unit 203b determines that pairing is possible.

[0052] Note that within the scope of the present invention, free combinations of the respective embodiments, modifications of any constituent elements of the respective embodiments, or omissions of any constituent elements in the respective embodiments are possible.

Description of Reference Numerals

[0053] 1 Ultrasonic flowmeter 2 Offset estimation device 101 Measurement pipe 102 Ultrasonic sensor 103 Ultrasonic sensor 104 Calculation unit 201 Prediction model acquisition unit 202 Impedance Feature Point Acquisition Unit 203, 203b Offset Calculation Unit

Claims

A prediction model acquisition unit that acquires, for each of a plurality of temperatures, a prediction model for estimating an offset of the ultrasonic propagation time difference in a pair of ultrasonic sensors from impedance characteristic points in the pair of ultrasonic sensors; an impedance characteristic point acquisition unit that acquires, for each of the temperatures, impedance characteristic points in a pair of ultrasonic sensors that are the objects of offset estimation; an offset calculation unit that calculates, for each of the temperatures, an offset of the ultrasonic propagation time difference in the pair of ultrasonic sensors by substituting the impedance characteristic points for each of the temperatures acquired by the impedance characteristic point acquisition unit into the prediction model for each of the temperatures acquired by the prediction model acquisition unit; An offset estimation device comprising:

2. Based on the calculated offset for each temperature, the offset calculation unit estimates the offset in the operating temperature range of the pair of ultrasonic sensors. The offset estimation device according to claim 1, characterized in that.

3. When the offset calculation unit determines that the fluctuation range of the calculated offset for each temperature is within the allowable error range, the offset calculation unit determines that the pair of ultrasonic sensors from which the offset is obtained are pairable ultrasonic sensors. The offset estimation device according to claim 1, characterized in that.

4. The prediction model acquisition unit creates a prediction model based on the impedance characteristic points in a pair of ultrasonic sensors and the measured values of the offset of the ultrasonic propagation time difference in the pair of ultrasonic sensors for each of the temperatures. The offset estimation device according to any one of claims 1 to 3, characterized in that.

5. A step in which a prediction model acquisition unit acquires, for each of a plurality of temperatures, a prediction model for estimating an offset of the ultrasonic propagation time difference in a pair of ultrasonic sensors from impedance characteristic points in the pair of ultrasonic sensors; a step in which, for each of the temperatures, an impedance characteristic point acquisition unit acquires impedance characteristic points in a pair of ultrasonic sensors that are the objects of offset estimation; a step in which an offset calculation unit calculates, for each of the temperatures, an offset of the ultrasonic propagation time difference in the pair of ultrasonic sensors by substituting the impedance characteristic points for each of the temperatures acquired by the impedance characteristic point acquisition unit into the prediction model for each of the temperatures acquired by the prediction model acquisition unit; An offset estimation method comprising:

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