JP2021067572A - Ultrasonic flowmeter and method for measuring flow rate - Google Patents

Abstract

To allow a measurement that can keep a predetermined accuracy to be done without doing another measurement if information of a zero-cross point cannot be obtained partially.SOLUTION: A missing part detection unit 106 detects a missing part in a zero-cross time in a time arrangement stored in a measurement unit 105. An interpolation unit 107 determines interpolation data obtained by using the zero-cross time stored in a storage position of the time arrangement immediately before or immediately after a missing part detected by the missing part detection unit 106 as the zero-cross time of the missing part.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ultrasonic flow meter and a flow rate measuring method.

Generally, in an ultrasonic flowmeter, two ultrasonic transmitters / receivers are arranged facing each other so as to cross a flow of fluid, and ultrasonic signals are transmitted / received in each of the forward and reverse directions to be transmitted between the two ultrasonic transmitters / receivers. The ultrasonic wave propagation time is measured, and the flow rate of the fluid is obtained based on the difference in the ultrasonic wave propagation time in the forward and reverse directions. The ultrasonic propagation time is measured by the so-called zero-cross method, in which the ultrasonic propagation time is obtained based on the zero-cross time at the zero-cross point where the voltage (AC voltage) of the received ultrasonic signal intersects with the zero voltage (0V). Is used (Patent Document 1).

In this zero-cross method, when determining the propagation time, it is necessary to always use the same pulse and the corresponding zero-cross point among the plurality of pulses included in the received wave. In the general zero-cross method, in order to detect the target zero-cross point corresponding to the same peak in the voltage (measured voltage) of the signal indicating the received ultrasonic signal, the point where the received ultrasonic signal exceeds a predetermined voltage level. The propagation time is calculated using the zero crossing points corresponding to the same pulse at all times, such as by starting recording for the zero crossing points after that.

Here, when a noise component is superimposed on the received wave and waveform distortion occurs, the time position of the zero cross point at which the ultrasonic signal exceeds a predetermined voltage level and recording is started is one ultrasonic period on the front side or the rear side. It may be misaligned. When such a deviation of the zero cross point occurs, the ultrasonic wave propagation time changes accordingly, which causes a flow rate measurement error. In order to deal with such a shift of the zero cross point, the time so that the zero cross time stored in the same storage position between adjacent time arrays becomes the zero cross time corresponding to the same pulse of each received wave. A technique has been proposed in which a shift process is performed to shift the storage position of the zero cross time in each of the arrays.

In the shift process described above, for example, as shown in FIGS. 10A and 10B, the column positions are shifted in row units with respect to the results of a plurality of propagation time measurements, and the zero cross information corresponding to the same zero cross point is obtained in the same column. They are lined up and reconnected.

In FIGS. 10A and 10B, an example is shown in which the number of zero cross points measured for each measurement voltage Vin # i is 5 (H = 5), and each zero cross time of these zero cross points is the storage position at the time of detection. At least two offsets (H-3) are provided in the front-rear direction. This offset is for shifting the zero cross time stored from the storage position K (K = H-2) at the time of detection back and forth without loss. As a result, there are at least nine storage positions in total.

First, the preset matching storage position to be matched, here, the zero cross time D # 1 [5] = "180000" (nsec) at the fifth storage position from the beginning of the time array is selected as the matching zero cross time. To do.

Next, the time difference between each zero cross time and the matched zero cross time is obtained for each D # j (integer of j = 2 to X) other than D # 1, and the zero cross time with the smallest time difference is the matched storage position. The storage position of each zero cross time of D # j is shifted so as to be.

As shown in FIG. 10A, for example, in the case of D # 2, the matching zero cross time D # 1 [5] and the zero cross time D # 2 [7] = "180022" at the seventh storage position of D # 2 The time difference "22" is the smallest as compared with, for example, the time difference "19969" from D # 2 [5] = "160031". Therefore, each zero cross time of D # 2 is shifted to the left by two toward the paper surface of FIG. 10A so that D # 2 [7] becomes the consistent storage position (left shift × 2).

In the case of the next D # 3, the time difference "11" between the zero cross time D # 3 [5] = "18001" at the fifth storage position of D # 1 [5] and D # 3 is the smallest. Each zero cross time of D # 3 is not shifted (no shift).

Further, in the case of D # 5, the time difference “5” between D # 1 [5] and the zero cross time D # 5 [3] = “18055” at the third storage position of D # 5 is the smallest. Therefore, each zero cross time of D # 5 is shifted to the right by two toward the paper surface of FIG. 10A so that D # 5 [3] becomes the consistent storage position (right shift × 2).

By the above shift processing, as shown in FIG. 10B, the zero cross time stored in the same storage position of each D # i becomes the zero cross time corresponding to the same pulse of each received wave.

Japanese Unexamined Patent Publication No. 2011-180076

By the way, some zero crossing point information may not be properly acquired due to noise generated during flow rate measurement. In this case, in the shift process as described above, there may be a case where the shift process cannot be performed because there is no data (zero cross time) to be shifted in the left-right direction of the paper in the figure. In addition, as described above, if a part of the data is missing, it is determined in the process of obtaining the representative value of the zero cross point (representative value extracted by removing random fluctuations) from the numerical values in each column. Digital filtering based on the number of data data cannot be applied, and the columns that can be used for calculation may be limited.

When a defect occurs, the data at the measurement time when the defect occurred cannot be used, so the data at this time is discarded and remeasured. However, in this case, the output of the flow rate data is delayed due to the remeasurement. In addition, problems such as an increase in power due to remeasurement will occur.

The present invention has been made to solve the above problems, and even when some zero cross point information cannot be obtained, a predetermined accuracy is maintained without remeasurement. The purpose is to enable the measurement.

In the ultrasonic flowmeter according to the present invention, a measurement step of transmitting and receiving an ultrasonic signal in both directions via a fluid to be measured flowing in a pipe is performed a plurality of times between a pair of ultrasonic transmitters and receivers, and these measurements are performed. An ultrasonic flowmeter that measures the flow rate of a fluid based on the difference in propagation time in the forward and reverse directions of the ultrasonic signal measured by the process, and is a measurement voltage that indicates the received wave of the ultrasonic signal for each measurement process. And the preset threshold voltage are compared, and after the measured voltage exceeds the threshold voltage, the zero cross time at which the measured voltage crosses zero is measured multiple times, and the measured multiple zero cross times are set in the time array corresponding to the measurement process. Of these, the zero cross time stored in the same storage position between the measurement unit configured to store in order from a preset specific storage position and the adjacent time array is the same for each received wave. A shift processing unit configured to shift the storage position of the zero-cross time in each of the time arrays so that the zero-cross time corresponds to the pulse, and a zero-cross time in the time array stored by the measurement unit. The interpolated data obtained by using the defect detection unit configured to detect the defect and the zero cross time stored in the storage position of the time array immediately before and after the defect location detected by the defect detection unit is deleted. The target storage position used for calculating the propagation time is specified from the interpolation unit configured to be the zero-cross time of the location and the storage position, and is obtained from the target zero-cross time stored in the target storage position of each time array. It is provided with a flow rate calculation unit configured to measure the flow rate of the fluid based on the propagation time.

In the above ultrasonic flow meter configuration example, it is configured to determine whether or not the defect portion detected by the defect detection unit is a continuous abnormality exceeding the set upper limit value for each measurement process. The determination unit is further provided with an abnormality processing unit configured to perform an abnormality process when the determination unit determines that the abnormality is abnormal.

In the above ultrasonic flow meter configuration example, a calculation unit configured to obtain the ratio of the number interpolated by the interpolation unit to the number of zero cross times in the time array stored by the measurement unit, and the calculation unit calculated. It further includes a determination unit configured to determine whether or not the ratio exceeds a set upper limit value, and an abnormality processing unit configured to perform an abnormality process when the determination unit determines that an abnormality is made.

In the above ultrasonic flow meter configuration example, the abnormality processing unit performs either processing of stopping the measurement of the fluid flow rate or recalculating the fluid flow rate.

In the above ultrasonic flow meter configuration example, the abnormality processing unit excludes a plurality of zero cross times stored by the measurement unit when the determination unit determines that the abnormality is abnormal.

In the flow rate measurement method according to the present invention, a measurement step of transmitting and receiving an ultrasonic signal in both directions is performed a plurality of times between a pair of ultrasonic transmitters and receivers via a fluid to be measured flowing in a pipe, and these measurement steps are performed. It is a flow rate measurement method that measures the flow rate of fluid based on the difference in propagation time in the forward and reverse directions of the ultrasonic signal obtained for each measurement process, and is a measurement voltage that indicates the received wave of the ultrasonic signal for each measurement process. And the preset threshold voltage are compared, and after the measured voltage exceeds the threshold voltage, the zero cross time at which the measured voltage crosses zero is measured multiple times, and the measured multiple zero cross times are set in the time array corresponding to the measurement process. Of these, the measurement step for storing in order from a specific storage position set in advance and the zero-cross time stored in the same storage position between the time arrays are the zero-cross times corresponding to the same pulse of each received wave. A shift processing step that shifts the storage position of the zero-cross time in each time array, and a defect detection configured to detect a loss of the zero-cross time in the time array stored in the measurement step. The interpolation data obtained by using the step and the zero-cross time stored in the storage position of the time array immediately before and after the defect detected in the defect detection step is configured to be the zero-cross time of the defect. The target storage position used for calculating the propagation time is specified from the interpolation step and the storage position, and the flow rate of the fluid is calculated based on the propagation time obtained from the target zero cross time stored in the target storage position of each time array. It is provided with a flow rate measurement step for measurement.

In one configuration example of the above flow rate measurement method, it is configured to determine whether or not the defect portion detected in the defect detection step exceeds the set upper limit value and is continuous in each measurement process. A determination step that has been performed, and an abnormality processing step that performs an abnormality process when it is determined to be abnormal in the determination step are further provided.

In one configuration example of the flow rate measurement method, the calculation step configured to obtain the ratio of the number interpolated in the interpolation step to the number of zero cross times in the time array stored in the measurement step, and the calculation step It further includes a determination step configured to determine whether or not the calculated ratio exceeds a set upper limit value, and an abnormality processing step that performs an abnormality process when the determination step determines that the abnormality is abnormal.

In one configuration example of the flow rate measurement method, the abnormality handling step performs either processing of stopping the measurement of the fluid flow rate or recalculating the fluid flow rate.

In one configuration example of the flow rate measurement method, the abnormality processing step excludes a plurality of zero cross times stored in the measurement step from the calculation target when an abnormality is determined in the determination step.

As described above, according to the present invention, the interpolated data obtained by using the zero-cross time stored in the storage position of the time array immediately before and after the missing part of the zero-cross time in the time array can be obtained. Since the zero cross time of the missing part is set, even if the information of a part of the zero cross points cannot be acquired, the measurement can be performed with the predetermined accuracy without remeasurement.

FIG. 1 is a configuration diagram showing a configuration of an ultrasonic flowmeter according to a first embodiment of the present invention. FIG. 2A is a signal waveform diagram showing the relationship between the detected voltage and the zero crossing point. FIG. 2B is an explanatory diagram showing the time interval and fluctuation with respect to the zero crossing point. FIG. 3A is an explanatory diagram for explaining an example of shift processing of the shift processing unit 108. FIG. 3B is an explanatory diagram for explaining an example of shift processing of the shift processing unit 108. FIG. 4 is a flowchart for explaining the flow rate measuring method according to the first embodiment of the present invention. FIG. 5 is a block diagram showing the configuration of the ultrasonic flowmeter according to the second embodiment of the present invention. FIG. 6 is a flowchart for explaining the flow rate measuring method according to the second embodiment of the present invention. FIG. 7 is a block diagram showing the configuration of the ultrasonic flowmeter according to the third embodiment of the present invention. FIG. 8 is a flowchart for explaining the flow rate measuring method according to the third embodiment of the present invention. FIG. 9 is a configuration diagram showing a hardware configuration of a flow rate calculation device for an ultrasonic flow meter according to an embodiment of the present invention. FIG. 10A is an explanatory diagram for explaining a shift process for the result of a plurality of propagation time measurements. FIG. 10B is an explanatory diagram for explaining a shift process for the result of a plurality of propagation time measurements.

Hereinafter, the ultrasonic flowmeter according to the embodiment of the present invention will be described.

[Embodiment 1]
First, the ultrasonic flowmeter according to the first embodiment of the present invention will be described with reference to FIG. This ultrasonic flowmeter performs a measurement step of transmitting and receiving an ultrasonic signal in both directions between a pair of ultrasonic transmitters / receivers 101 and an ultrasonic transmitter / receiver 102 via a fluid 104 to be measured flowing in a pipe 103. (N is an integer of 2 or more) is performed, and the flow rate of the fluid 104 is measured by the flow rate calculation device 100 based on the difference in the propagation time of the ultrasonic signals measured by these measurement steps.

The ultrasonic transmitter / receiver 101 transmits an ultrasonic signal U1 toward the inside of the pipe 103 in response to an ultrasonic drive signal from the flow rate calculation device 100 connected via wiring. Similarly, the ultrasonic transmitter / receiver 102 transmits the ultrasonic signal U2 into the pipe 103 in response to the ultrasonic drive signal from the flow rate calculation device 100 connected via the wiring. The ultrasonic transmitter / receiver 102 (ultrasonic transmitter / receiver 101) receives the ultrasonic signal U1 (U2) from the ultrasonic transmitter / receiver 101 (ultrasonic transmitter / receiver 102) that has passed through the fluid flowing in the pipe 103, and receives the ultrasonic signal U1 (U2). The measurement signal indicating the reception result is output to the flow rate calculation device 100 via the wiring.

At this time, the propagation times t1 and t2 of the ultrasonic signals U1 and U2 exchanged with the ultrasonic transmitters and receivers 101 and 102 are affected by the flow of the fluid 104 differently, and therefore correspond to the flow rate Q of the fluid 104. A difference, that is, a propagation time difference Δt, occurs between the propagation time t1 and the propagation time t2 by the amount. The ultrasonic flow meter derives the flow rate Q based on this Δt. As the calculation method for obtaining the flow rate Q from the propagation time difference Δt used in the flow rate calculation device 100 according to the present embodiment, a known calculation formula used in a general ultrasonic flow meter may be used. The detailed description in is omitted.

The flow rate calculation device 100 includes a measurement unit 105, a defect detection unit 106, an interpolation unit 107, a shift processing unit 108, a flow rate calculation unit 109, an output unit 110, a control unit 112, an input / output I / F unit 113, and a storage unit 114. Be prepared.

The measurement unit 105 compares the measurement voltage indicating the received wave of the ultrasonic signal with the preset threshold voltage for each measurement process, and sets a plurality of zero cross times at which the measurement voltage zero-crosses after the measurement voltage exceeds the threshold voltage. The measurement is performed once, and the plurality of measured zero-cross times are stored in order from a specific storage position set in advance in the time array corresponding to the measurement process.

The defect detection unit 106 detects a defect at the zero cross time in the time array stored by the measurement unit 105. For example, the defect detection unit 106 detects a defect at the zero cross time in the time array stored by the measurement unit 105 and subjected to the shift processing by the shift processing unit. The interpolation unit 107 uses the interpolation data obtained by using the zero-cross time stored in the storage position of the time array immediately before and after the defect detected by the defect detection unit 106 as the zero-cross time of the defect. For example, the interpolation unit 107 linearly interpolates the values between adjacent rows in the same column as the missing portion in the time array to obtain the interpolation data. It is also possible to interpolate by exfoliating from the value in the previous row in the same column. Further, the same value as the value in the previous row in the same column can be used as the interpolation data.

If there is data in a column near the same row as the missing part, the interpolation unit 107 subtracts the time according to the period of the received wave from the data (single or multiple averages) existing in the same row. It is also possible to obtain the added (added) value and use it as interpolated data. It is also possible to obtain the interpolated data by linearly interpolating the values before and after the same column. It is also possible to obtain the interpolated data by exfoliating from the immediately preceding value. Further, the same value as the immediately preceding value can be used as the interpolation data.

The distance between the measured zero cross points is determined by the period of the received ultrasonic waves. Therefore, the time of the missing zero crossing point can be estimated by adding a corresponding period from the nearby zero crossing point, and it can be used for interpolation of data loss.

The shift processing unit 108 sets the zero-cross time in each of the time arrays so that the zero-cross time stored in the same storage position between the adjacent time arrays becomes the zero-cross time corresponding to the same pulse of each received wave. Performs a shift process that shifts each storage position.

The flow rate calculation unit 109 specifies the target storage position used for calculating the propagation time from the storage positions, and based on the propagation time obtained from the target zero cross time stored in the target storage position of each time array, the fluid Measure the flow rate. For example, the flow rate calculation unit 109 specifies a target storage position to be used for calculating the propagation time from the storage positions based on the processing result of the shift processing by the shift processing unit 108 and the processing result of the interpolation processing by the interpolation unit 107. , The flow rate of the fluid is measured based on the propagation time obtained from the target zero cross time stored in the target storage position of each time array after the shift processing and the interpolation processing.

The output unit 110 connects to a higher-level device (not shown) via the communication network 121, acquires the flow rate Q from the storage unit 114 periodically or in response to an output instruction from the higher-level device, and outputs the flow rate Q to the higher-level device. ..

The input / output I / F unit 113 is connected to the ultrasonic transmitter / receiver 101 and the ultrasonic transmitter / receiver 102 via wiring, and transmits various signals used for measurement between the ultrasonic transmitter / receiver 101 and the ultrasonic transmitter / receiver 102. Communicate. The storage unit 114 is composed of a storage device such as a semiconductor memory or a hard disk, and stores various processing data and programs used for the flow rate measurement operation in the flow rate calculation device 100.

The control unit 112 receives ultrasonic waves from the input / output I / F unit 113 in response to the arrival of a preset periodic measurement timing or an instruction from an operator or a higher-level device (not shown) at an arbitrary timing. An ultrasonic drive signal is output to the transmitter / receiver 101 and the ultrasonic transmitter / receiver 102, and the ultrasonic signals U1 and U2 are transmitted between the ultrasonic transmitter / receiver 101 and the ultrasonic transmitter / receiver 102 via the fluid 104 to be measured in both directions. The measurement process of alternately transmitting and receiving is repeated.

Next, the principle of shift processing will be described with reference to FIG. 2A. As shown in FIG. 2A, the measurement voltage Vin indicating the measurement signal input from the ultrasonic transmitters / receivers 101 and 102 to the flow rate calculation device 100 is composed of a plurality of sinusoidal AC pulses whose amplitudes increase / decrease along the time axis.

Similar to the zero cross method described above, the flow rate calculation device 100 measures the time when the target zero cross point is detected from the plurality of zero cross points where Vin intersects the zero voltage Vz (0V), and measures the target zero cross point. Is specified as the reception time of the ultrasonic signal U1 (U2) corresponding to Vin, and the propagation time t1 (t2) of U1 (U2) and the propagation time difference Δt are calculated from the obtained reception time. The flow rate Q is derived.

When specifying the target zero crossing point from a plurality of zero crossing points, the flow rate calculation device 100 measures a trigger point in which the Vin exceeds a preset threshold voltage Vs, thereby causing a plurality of positive sides (negative) included in the Vin. Of the side) pulses, the M (M is an integer of 2 or more) th pulse from the beginning is specified as the target pulse. Further, the flow rate calculation device 100 is the N1 and N2 (N1, N2 are integers of 1 to H) th from the beginning among the H (H is an integer of 3 or more) zero cross points measured after the specified trigger point. Is specified as the target zero cross point.

In each measurement process, the trigger point is often measured at the correct timing, that is, at the target pulse. However, when the amplitude change of Vin occurs due to the superimposition of a noise component on Vin, the trigger point may be shifted back and forth by one ultrasonic period and measured. In FIG. 2A, the case of M = 3, H = 5, N1 = 2, N2 = 3 is shown as an example. In FIG. 2A, of the 3 (M = 3) waves from the beginning of Vin, that is, the zero cross points Z3 to Z7 of 5 (H = 5) after the pulse P3, 2, 3 (N1 = 2, N2 = 3) from the beginning. An example is shown in which the) th zero cross points Z4 and Z5 are specified as the target zero cross points.

In this case, in order to compare Vin and Vs and measure the trigger point with the pulse P3, the voltage value of Vs is empirical so that the amplitude of the previous pulse P2 does not exceed Vs and exceeds Vs for the first time at P3. Is set to. Therefore, as shown in FIG. 2A, when Vin is Vin # 1, since Vin # 1 of P3 exceeds Vs at the time Ts1, the trigger point is correctly measured by the target pulse. As a result, the measurement of the zero cross point is started at Ts1, and as a result, the second and third zero cross points Z4 and Z5 measured from Ts1 are measured as the target zero cross points.

On the other hand, when the amplitude of Vin increases due to the superposition of noise components and the Vin changes like Vin # 2, as shown in FIG. 2A, Vin # 2 of P2 before P3 changes to Vs at time Ts2. Will be exceeded, and the trigger point will be measured one ultrasonic cycle earlier than the target pulse. In this case, the measurement of the zero cross point is started at Ts2 before Ts1, and as a result, the second and third zero cross points Z2 and Z3 measured from Ts2 are measured as the target zero cross points. ..

Therefore, when the zero cross time of each zero cross point is stored in the time array D # i corresponding to the measurement step i, the zero cross points Z3, Z4, Z5, Z6 measured after the time Ts1 when Vin # 1 exceeds Vs. , Z7 The zero cross times T3, T4, T5, T6, T7 corresponding to Z7 are stored in the time array D # 1. Further, the zero cross time T1, T2, T3, T4, T5 corresponding to the zero cross points Z1, Z2, Z3, Z4, Z5 measured after the time Ts2 when Vin # 2 exceeds Vs is added to the time array D # 2. On the other hand, it will be stored.

Therefore, in the example of FIG. 2A, the measurement time of the first zero cross point measured after Ts1 in the case of Vin # 1 and the third zero cross point measured after Ts2 in the case of Vin # 2 is Z3. It becomes almost equal to the time T3 of. In the case of Vin # 1, the measurement time of the third zero cross point from the beginning measured after Ts1 and the measurement time of the fifth zero cross point measured after Ts2 in the case of Vin # 2 are the time T5 of Z5. Is almost equal to.

On the other hand, there is a certain relationship between the time interval and the fluctuation regarding the zero crossing point. FIG. 2B is an explanatory diagram showing the time interval and fluctuation with respect to the zero crossing point. In FIG. 2B, the measurement time of each zero cross point is plotted on the time axis for each Vin # i (i is an integer of 1 to X).

When observing the measurement time of each zero cross point, as shown in FIG. 2B, the measurement time of the zero cross point fluctuates due to the influence of Vin noise and pulsation, but the fluctuation range is limited and the actual measurement is performed. It is known that the value is about ± 400 nsec with respect to the true value. On the other hand, the pulse width of Vin is substantially constant depending on the signal frequencies fu of the ultrasonic signals U1 and U2. For example, when the pulse width of Vin is fu = 500 kHz, the half wavelengths of U1 and U2 are 1000 nsec, and the time interval of the zero cross point is 1000 nsec, which is almost the same.

Therefore, when the measurement is repeated a plurality of times at short time intervals, the propagation time of the ultrasonic signals U1 and U2 changes continuously, so that between two adjacent measurements (for example, Vin # 1 and Vin #). Focusing on 2), it was found that the measurement time of the zero cross point corresponding to the same pulse is unlikely to fluctuate beyond the time interval of 1000 nsec of the zero cross point. The time interval between the plus-zero cross points where the voltage passes from minus to zero and between the minus-zero cross points where the voltage passes from plus to zero is approximately 2000 nsec.

The shift processing unit 108 pays attention to the relationship between the time interval and the fluctuation of the zero cross point as described above, and measures in the measurement step i (integer of i = 1 to X) in which the ultrasonic signals U1 and U2 are repeatedly transmitted and received. Each time the voltage Vin # i is input, the zero cross times of a plurality of zero cross points measured after Vin # i exceeds Vs are stored in the time array D # i, and the time difference between the zero cross times at the same storage position is stored. A shift process is performed to shift the storage position of the zero cross time in each time array D # i so as to be the minimum. Further, the shift processing unit 108 extracts the zero cross time stored in the preset target storage position from the time array after the shift process, and statistically processes these zero cross times based on the reception time obtained. , U1, U2 propagation time t1, t2 is calculated.

Next, an example of the shift processing of the shift processing unit 108 will be described with reference to FIGS. 3A and 3B. Here, similarly to the target zero cross point of FIG. 2A described above, the 3 (M = 3) th pulse from the beginning of Vin is measured, and the 5 (H = 5) zero cross points measured after that are measured. An example will be described in which the second and third (N1 = 2, N2 = 3) th items from the beginning are measured as the target zero cross point. It should be noted that the present invention is not limited to this, and different numbers may be used as M, H, and N. Further, the case where the target zero cross time used for the calculation of the propagation time is two (N1, N2) will be described as an example, but it is sufficient that at least one target zero cross time is specified.

The shift process shifts the storage position of the zero cross time in each time array so that the time difference of the zero cross time stored in the same storage position in the time array D # i is minimized. The time array D # i is stored in the storage unit 12 for each measurement voltage Vin # i measured in each measurement step i by the measurement unit 105. In this example, an example is shown in which the number of zero cross points measured for each Vin # i is 5 (H = 5), and each zero cross time of these zero cross points is at least before and after the storage position at the time of measurement. Two offsets (H-3) are provided. This offset is for shifting the zero cross time stored from the storage position K (K = H-2) at the time of measurement back and forth without loss. As a result, there are at least nine storage positions in total.

First, the shift processing unit 108 is set in a preset matching storage position to be matched, in which the zero cross time D # 1 [5] = "180000" (nsec) at the fifth storage position from the beginning of the time array. Is selected as the matched zero cross time. At this time, the consistent storage position can be a target storage position set in advance as a design value. It is also possible to empirically select a storage position with a high storage frequency and set it as a consistent storage position.

Next, the shift processing unit 108 obtains the time difference between each zero cross time and the matched zero cross time for each D # j (integer of j = 2 to X) other than D # 1, and the time difference is the smallest. The storage position of each zero cross time of D # j is shifted so that the zero cross time becomes the consistent storage position.

For example, in the case of D # 2, the time difference “22” between the matched zero cross time D # 1 [5] and the zero cross time D # 2 [7] = “180022” at the seventh storage position of D # 2 is For example, it is the smallest as compared with the time difference "19969" from D # 2 [5] = "160031". Therefore, a shift pattern of "shifting by two to the left" (left shift x 2) is applied to each zero cross time of D # 2 so that D # 2 [7] becomes the consistent storage position. Will be done. In the case of the next D # 3, the time difference "11" between the zero cross time D # 3 [5] = "18001" at the fifth storage position of D # 1 [5] and D # 3 is the smallest. A shift pattern of "no shift" (no shift) is applied to each zero cross time of D # 3.

Further, in the case of D # 5, the time difference “5” between D # 1 [5] and the zero cross time D # 5 [3] = “18055” at the third storage position of D # 5 is the smallest. Therefore, a shift pattern of "shifting by two to the right" (right shift x 2) is applied to each zero cross time of D # 5 so that D # 5 [3] becomes the consistent storage position. Will be done.

As a result, the zero-cross time stored in the same storage position of each D # i becomes the zero-cross time corresponding to the same pulse of each received wave. Therefore, the flow rate calculation unit 109 specifies the target zero cross time of each D # i after these shift processes, obtains the propagation time t1 (t2) of the ultrasonic signal U1 (U2), and further obtains the propagation time difference Δt, and the fluid. Flow rate Q will be calculated.

In the above description, the shift pattern of D # j is based on the time difference between the matched zero cross time in D # 1 of the first measurement step 1 and each zero cross time in D # j other than D # 1. The case of determining is described as an example. The time difference is not limited to this. For example, the shift pattern of D # j is set based on the time difference between the matched zero cross time in D # i and the time difference between the next measurement step j (j = i + 1) of D # i and each zero cross time of the adjacent D # j. It is determined, and it can be repeatedly executed in order from i = 1.

Here, when there is no data to be shifted (zero cross time) (a part of the data is missing), a time array in which no data exists at a specific storage position occurs after the shift process is performed. This data defect is detected by the defect detection unit 106, and the interpolation unit 107 obtains the interpolation data using the zero cross time stored in the storage position of the time array immediately before and after the defect location, and zero cross of the defect location. Let it be the time. Since the propagation time is measured a plurality of times at intervals of several msec, it has been found that the time at which the zero cross point derived from the same pulse is recorded tends to change continuously. By utilizing this and compensating for the missing data, interpolation with less error can be performed.

As a result, the flow rate calculation unit 109 calculates the flow rate of the fluid based on the propagation time obtained from the target zero cross time stored in the target storage position of each time array after the shift process without data loss. Can be measured.

Next, the operation of the flow rate calculation device 100 according to the first embodiment will be described with reference to FIG. The measurement unit 105, the defect detection unit 106, the interpolation unit 107, the shift processing unit 108, and the flow rate calculation unit 109 of the flow rate calculation device 100 execute the flow rate measurement process of FIG. 4 for each measurement process by the control unit 112.

Here, the number of measurement voltage Vins measured in a series of measurement steps is set to X in each of the forward and reverse directions of the ultrasonic signal, and the third pulse (M = 3) from the beginning of the measured Vins. When measuring P3, measuring 5 (H = 5) zero crossing points after P3, and selecting the 2nd and 3rd (N1 = 2, N2 = 3) th from the beginning as the target zero crossing point, any of them. One direction will be described as an example. It is assumed that Vs is empirically set to a voltage value higher than the amplitude of the second pulse P2 from the beginning and lower than the amplitude of P3.

First, in step S101, the measurement unit 105 newly acquires the measurement voltage Vin # i converted to A / D by the input / output I / F unit 113 in the measurement step i (integer of i = 1 to X), and steps. In S102, Vin # i and the threshold voltage Vs are compared. Here, in the case of Vin # i ≦ Vs (no in step S102), the zero cross measurement is not started and the process returns to step S101. On the other hand, when Vin # i> Vs and the trigger point is measured (yes in step S102), the measurement unit 105 starts the measurement of the zero cross point.

Next, in step S103, the measurement unit 105 initializes the storage position k of the time array D # i to the preset K (K = H-2) th, and then in step S104, the input / output I / O / The measured voltage Vin # i converted to A / D is newly acquired in the F unit 11, and in step S105, it is confirmed whether or not it is the zero cross point depending on the presence or absence of the polarity change of Vin # i. Here, if there is no change in the polarity of Vin # i and it is not the zero crossing point (no in step S105), the process returns to step S104.

On the other hand, when there is a change in the polarity of Vin # i and the zero cross point is measured (yes in step S105), the time of Vin # i whose zero cross point is measured is acquired as the zero cross time Tz in step S106, and in step S107, Tz is stored in the storage position k of the time array D # i.

After that, in step S108, the measurement unit 105 confirms the completion of the zero-cross measurement by incrementing the storage position k (k = k + 1) and comparing k with K + M. If k ≦ K + M and the zero cross measurement is not completed (no in step S108), the process returns to step S104.

On the other hand, when k> K + M and the measurement of M zero cross points is completed (yes in step S108), in step S109, the measurement unit 105 increments the measurement process number i (i = i + 1) and then X. Confirm the completion of the measurement process by comparing with. If i ≦ X and the measurement process is not completed (no in step S109), the process returns to step S101. As described above, M × X zero cross times are measured for the forward ultrasonic signal U1 and M × X zero cross times are measured for U2 in the same manner. Subsequent processing is performed for each of the U1 zero cross time and the U2 zero cross time.

On the other hand, when i> X and all the measurement steps are completed (yes in step S109), in step S111, the shift processing unit 108 refers to the X time arrays D # i stored in the storage unit 114. Then, it is determined whether or not the zero cross time stored in the adjacent storage position K can be acquired correctly (whether or not it is an abnormal value). For example, the above-mentioned determination can be made based on the periodicity of ultrasonic waves.

As is well known, if the zero cross time by the ultrasonic received wave is correctly acquired, the period for acquiring the adjacent zero cross time is determined by the frequency of the ultrasonic wave and is almost constant. For example, in the case of a received wave of 500 kHz, it is around 1000 nsec. Therefore, if the difference from the zero-cross time before and after is significantly different from the value assumed from the ultrasonic frequency, it can be determined that the zero-cross time has not been acquired correctly.

If it is determined that the acquisition is not correct (yes in step S111), the abnormal value processing is performed in step S112. For example, as an outlier processing, the zero cross time determined not to be acquired correctly is set as an outlier and is in a missing state. In addition, as outlier processing, the zero cross time determined to be not acquired correctly can be changed to the value (zero cross time) expected from the previous and next zero cross times and the ultrasonic frequency in the same time array. it can.
After performing the above-mentioned abnormal value processing, or when it is determined that there is no abnormal value (no in step S111), the shift processing unit 108 is stored in the storage unit 114 in step S113 without performing the abnormal value processing. A shift that shifts the storage position of the zero-cross time in the time array D # i so that the time difference between the zero-cross times stored in the same storage position is minimized by referring to the X time arrays D # i. Execute processing (shift processing step).

Next, in step S114, the defect detection unit 106 detects the defect of the zero cross time in the time array stored in the measurement unit 105 (defect detection step). Next, in step S115, it is determined whether or not a defect is detected. When a defect is detected (yes in step S115), in step S116, the interpolation unit 107 uses the zero cross time stored in the storage position of the time array immediately before and after the defect detected by the defect detection unit 106. The interpolated data obtained is set as the zero cross time of the missing part (interpolation step).

On the other hand, when no defect is detected (no in step S115), in step S117, the flow rate calculation unit 109 sets the target zero cross time stored in the preset target storage position for each time array D # i. The flow rate Q of the fluid is calculated based on the propagation time t1 (t2) of U1 (U2) calculated by specifying it as the reception time tr of the corresponding Vin # i and using the reception time tr (flow rate measurement step). The generated flow rate Q is stored in the storage unit 114, and a series of flow rate measurement processes is completed.

[Embodiment 2]
Next, the ultrasonic flowmeter according to the second embodiment of the present invention will be described with reference to FIG. Hereinafter, the flow rate calculation device 100a of the ultrasonic flow meter according to the second embodiment will be described. Other configurations are the same as those in the first embodiment described above.

The flow rate calculation device 100a includes a measurement unit 105, a defect detection unit 106, an interpolation unit 107, a shift processing unit 108, a flow rate calculation unit 109, an output unit 110, a determination unit 111, an abnormality processing unit 115, a control unit 112, and an input / output I / O. The F unit 113 and the storage unit 114 are provided.

The determination unit 111 determines whether or not the defect portion detected by the defect detection unit exceeds the set upper limit value and is continuous for each measurement process. When the determination unit 111 determines that the abnormality is abnormal, the abnormality processing unit 115 performs the abnormality processing. The abnormality processing unit 115 stops the measurement of the flow rate of the fluid in the flow rate calculation device 100a as the abnormality processing. Further, the abnormality processing unit 115 processes the flow rate of the fluid to be recalculated by the measurement unit 105, the defect detection unit 106, the interpolation unit 107, the shift processing unit 108, the flow rate calculation unit 109, etc. of the flow rate calculation device 100a as the abnormality processing. To be carried out. Further, the abnormality processing unit 115 can exclude a plurality of zero cross times stored by the measurement unit 105 when the determination unit 111 determines that the abnormality is abnormal.

Next, the operation of the flow rate calculation device 100a according to the second embodiment will be described with reference to FIG. First, in step S110, the measuring unit 105 compares the measured voltage indicating the received wave of the ultrasonic signal with the preset threshold voltage for each measurement process, and after the measured voltage exceeds the threshold voltage, the measured voltage is changed. The zero-crossing zero-crossing time is measured a plurality of times, and the plurality of measured zero-crossing times are stored in order from a specific storage position set in advance in the time array corresponding to the measurement process (measurement step). Step S110 is the same as step S101 to step S109 of the first embodiment described above.

Next, the shift process is performed in steps S111 to S113 in the same manner as in the first embodiment described above. Next, in step S114, the defect detection unit 106 detects the defect of the zero cross time in the time array stored in the measurement unit 105 (defect detection step). Next, in step S115, it is determined whether or not a defect is detected. When a defect is detected (yes in step S115), the process proceeds to step S121 below. On the other hand, if no defect is detected (no in step S115), the process proceeds to step S117, which will be described later.

In step S121, the determination unit 111 determines whether or not the defect portion detected by the defect detection unit 106 exceeds the set upper limit value and is continuous for each measurement process (determination step). .. When the defect locations detected by the defect detection unit 106 exceed the set upper limit value and are continuous for each measurement process, the time array of this set of X cannot guarantee the accuracy required for the flow rate calculation. It can be judged, and it can be judged as abnormal.

When the detected defect locations exceed the upper limit value and are continuous (yes in step S121), in step S122, the abnormality processing unit 115 stops the measurement of the fluid flow rate as an abnormality process (abnormal processing step). ). Next, in step S123, the abnormality processing unit 115 notifies the operator or the host device that an abnormality has occurred in the measurement of the ultrasonic flow meter, and ends. If the determination unit 111 determines in step S121 that the defect locations detected by the defect detection unit 106 exceed the set upper limit value and are continuous for each measurement process, the process returns to step S110. , The measurement can be performed again. In this case, it is possible to exclude a plurality of zero cross times stored by the measuring unit 105, which have been determined to be abnormal, from the calculation target. Further, in this case, the set value such as the threshold value can be updated.

On the other hand, when the detected defect locations do not exceed the upper limit and are not continuous (no in step S121), in step S116, the interpolation unit 107 immediately before and immediately after the defect location detected by the defect detection unit 106. The interpolated data obtained by using the zero-cross time stored in the storage position of the time array is defined as the zero-cross time of the missing part.

Finally, in step S117, the flow rate calculation unit 109 specifies the target zero cross time stored in the preset target storage position for each time array D # i as the reception time tr of the corresponding Vin # i. Then, the flow rate Q of the fluid is calculated based on the propagation time t1 (t2) of U1 (U2) calculated using the reception time tr, the obtained flow rate Q is stored in the storage unit 114, and a series of flow rate measurements are performed. End the process.

[Embodiment 3]
Next, the ultrasonic flowmeter according to the third embodiment of the present invention will be described with reference to FIG. 7. Hereinafter, the flow rate calculation device 100b of the ultrasonic flow meter according to the third embodiment will be described. Other configurations are the same as those in the first embodiment described above.

The flow rate calculation device 100b includes a measurement unit 105, a defect detection unit 106, an interpolation unit 107, a shift processing unit 108, a flow rate calculation unit 109, an output unit 110, a determination unit 111a, a calculation unit 116, an abnormality processing unit 115, and a control unit 112. It includes an input / output I / F unit 113 and a storage unit 114.

The calculation unit 116 obtains the ratio of the number interpolated by the interpolation unit to the number of zero cross times in the time array stored by the measurement unit 105. For example, the calculation unit 116 interpolates the total number of data (the number of rows from D # 1 to # n × the number of multiple zero cross columns) to be used for the representative value calculation in the time array stored by the measurement unit 105. The ratio of the number of data generated is calculated as the interpolation rate. The determination unit 111a determines whether or not the ratio calculated by the calculation unit 116 exceeds the set upper limit value. When the determination unit 111a determines that the abnormality processing unit 115 is abnormal, the abnormality processing unit 115 stops the measurement of the fluid flow rate.

If the ratio (interpolation rate) exceeds a predetermined ratio, the accuracy of the flow rate measurement result cannot be guaranteed. In this case, as, the use of data by interpolation is stopped. In addition, an abnormality flag is set for the entire measurement data. For example, if all the data can be acquired normally, the number is 30, and if there is 8 data that needs to be interpolated, the interpolation rate is 8/30 = 0.27. Decide whether to use the whole or discard the whole data as an anomalous measurement.

Next, the operation of the flow rate calculation device 100b according to the third embodiment will be described with reference to FIG. First, in step S110, the measuring unit 105 compares the measured voltage indicating the received wave of the ultrasonic signal with the preset threshold voltage for each measurement process, and after the measured voltage exceeds the threshold voltage, the measured voltage is changed. The zero-crossing zero-crossing time is measured a plurality of times, and the plurality of measured zero-crossing times are stored in order from a specific storage position set in advance in the time array corresponding to the measurement process (measurement step). Step S110 is the same as step S101 to step S109 of the first embodiment described above.

Next, the shift process is performed in steps S111 to S113 in the same manner as in the first and second embodiments described above. Next, in step S114, the defect detection unit 106 detects the defect of the zero cross time in the time array stored in the measurement unit 105 (defect detection step). Next, in step S115, it is determined whether or not a defect is detected. When a defect is detected (yes in step S115), in step S116, the interpolation unit 107 uses the zero cross time stored in the storage position of the time array immediately before and after the defect detected by the defect detection unit 106. Let the interpolated data obtained by the above be the zero cross time of the missing part. On the other hand, if no defect is detected (no in step S115), the process proceeds to step S117, which will be described later.

Next, following step S116, in step S131, the calculation unit 116 obtains the ratio of the interpolated number to the number of zero cross times in the time array stored by the measurement unit 105 (calculation step). Next, in step S132, the determination unit 111a determines whether or not the ratio calculated by the calculation unit 116 exceeds the set upper limit value (determination step). When the ratio calculated by the calculation unit 116 exceeds the set upper limit value, it can be determined that the time array of this X group cannot guarantee the accuracy required for the flow rate calculation, and it is determined to be abnormal. be able to.

When the calculated ratio exceeds the set upper limit value (yes in step S132), in step S122, the abnormality handling unit 115 stops the measurement of the fluid flow rate as an abnormality processing (abnormal processing step). Next, in step S123, the abnormality handling unit 115 notifies the operator that an abnormality has occurred in the measurement of the ultrasonic flow meter, and ends. If the determination unit 111a determines in step S132 that the ratio calculated by the calculation unit 116 exceeds the set upper limit value, the process can return to step S110 and the measurement can be performed again. In this case, it is possible to exclude a plurality of zero cross times stored by the measuring unit 105, which have been determined to be abnormal, from the calculation target. Further, in this case, the set value such as the threshold value can be updated.

On the other hand, when the calculated ratio does not exceed the upper limit value (no in step S132), or when no defect is detected (no in step S113), in step S117, the flow rate calculation unit 109 performs the shift process. For each time array D # i, the target zero cross time stored in the preset target storage position is specified as the reception time tr of the corresponding Vin # i, and U1 (U2) calculated using the reception time tr. ), The flow rate Q of the fluid is calculated based on the propagation time t1 (t2), the obtained flow rate Q is stored in the storage unit 114, and a series of flow rate measurement processes are completed.

As shown in FIG. 9, the flow calculation device of the ultrasonic flow meter according to the above-described embodiment is a CPU (Central Processing Unit) 301, a main storage device 302, an external storage device 303, and a network. As a computer device equipped with a connection device 304 and the like, the CPU 301 operates (executes the program) by the program deployed in the main storage device 302, so that each of the above-mentioned functions (flow rate measurement method) can be realized. You can also do it. The above program is a program for a computer to execute the flow rate measuring method shown in the above-described embodiment. The network connection device 304 connects to the network 305. In addition, each function can be distributed to a plurality of computer devices.

As described above, according to the present invention, the interpolated data obtained by using the zero-cross time stored in the storage position of the time array immediately before and after the missing part of the zero-cross time in the time array can be obtained. Since the zero cross time of the missing part is set, even if the information of a part of the zero cross points cannot be acquired, the measurement can be performed with the predetermined accuracy without remeasurement.

The present invention is not limited to the embodiments described above, and many modifications and combinations can be carried out by a person having ordinary knowledge in the art within the technical idea of the present invention. That is clear.

100 ... Flow rate calculation device, 101, 102 ... Ultrasonic transmitter / receiver, 103 ... Piping, 104 ... Fluid, 105 ... Measurement unit, 106 ... Defect detection unit, 107 ... Interpolation unit, 108 ... Shift processing unit, 109 ... Flow rate calculation unit , 110 ... Output unit, 112 ... Control unit, 113 ... Input / output I / F unit, 114 ... Storage unit, 121 ... Communication network.

Claims (10)

A measurement process of transmitting and receiving an ultrasonic signal in both directions via a fluid to be measured flowing in a pipe between a pair of ultrasonic transmitters and receivers is performed a plurality of times, and the order of the ultrasonic signals measured by these measurement steps is performed. An ultrasonic flowmeter that measures the flow rate of the fluid based on the difference in propagation time in the opposite direction.
For each measurement step, the measurement voltage indicating the received wave of the ultrasonic signal is compared with a preset threshold voltage, and after the measurement voltage exceeds the threshold voltage, a plurality of zero cross times at which the measurement voltage crosses zero are set. A measurement unit configured to measure multiple times and store a plurality of measured zero-cross times in order from a preset specific storage position in the time array corresponding to the measurement process.
The storage position of the zero-cross time in each of the time arrays is shifted so that the zero-cross time stored in the same storage position becomes the zero-cross time corresponding to the same pulse of each received wave between adjacent time arrays. A shift processing unit configured to perform shift processing, and
A defect detection unit configured to detect a zero-cross time defect in the time array stored by the measurement unit, and a defect detection unit.
An interpolation unit configured to use the interpolation data obtained by using the zero-cross time stored in the storage position of the time array immediately before and after the defect detected by the defect detection unit as the zero-cross time of the defect. When,
The target storage position used for calculating the propagation time is specified from the storage positions, and the flow rate of the fluid is based on the propagation time obtained from the target zero cross time stored in the target storage position of each time array. An ultrasonic flowmeter with a flow rate calculator configured to measure. In the ultrasonic flow meter according to claim 1,
A determination unit configured to determine whether or not the defect portion detected by the defect detection unit is a continuous abnormality exceeding a set upper limit value for each measurement process.
An ultrasonic flowmeter characterized by further including an abnormality handling unit configured to perform an abnormality processing when the determination unit determines that the abnormality is determined. In the ultrasonic flow meter according to claim 1,
A calculation unit configured to obtain the ratio of the number interpolated by the interpolation unit to the number of zero-cross times in the time array stored by the measurement unit.
A determination unit configured to determine whether or not the ratio calculated by the calculation unit exceeds a set upper limit value, and a determination unit.
An ultrasonic flowmeter characterized by further including an abnormality handling unit configured to perform an abnormality processing when the determination unit determines that the abnormality is determined. In the ultrasonic flow meter according to claim 2 or 3.
The abnormality processing unit is an ultrasonic flow meter characterized in that the measurement of the flow rate of the fluid is stopped or the recalculation of the flow rate of the fluid is performed. In the ultrasonic flow meter according to claim 2 or 3.
The abnormality processing unit is an ultrasonic flowmeter that excludes a plurality of zero cross times stored by the measuring unit when the determination unit determines that the abnormality is abnormal. A measurement process of transmitting and receiving an ultrasonic signal in both directions via a fluid to be measured flowing in a pipe between a pair of ultrasonic transmitters and receivers is performed a plurality of times, and the ultrasonic signal obtained in each of these measurement steps is performed. It is a flow rate measurement method that measures the flow rate of the fluid based on the difference in propagation time in the forward and reverse directions of.
For each measurement step, the measurement voltage indicating the received wave of the ultrasonic signal is compared with a preset threshold voltage, and after the measurement voltage exceeds the threshold voltage, a plurality of zero cross times at which the measurement voltage crosses zero are set. A measurement step in which a plurality of measured zero-cross times are measured in order from a preset specific storage position in a time array corresponding to the measurement process.
A shift that shifts the storage position of the zero cross time in each time array so that the zero cross time stored in the same storage position becomes the zero cross time corresponding to the same pulse of each received wave between adjacent time arrays. The shift processing step to perform the processing and
A defect detection step configured to detect a zero-cross time defect in the time array stored in the measurement step, and a defect detection step.
Interpolation configured to use the interpolation data obtained by using the zero-cross time stored in the storage position of the time array immediately before and after the defect detected in the defect detection step as the zero-cross time of the defect. Steps and
The target storage position used for calculating the propagation time is specified from the storage positions, and the flow rate of the fluid is based on the propagation time obtained from the target zero cross time stored in the target storage position of each time array. A flow measurement method that includes a flow measurement step to measure. In the flow rate measuring method according to claim 6,
A determination step configured to determine whether or not the defect portion detected in the defect detection step exceeds the set upper limit value and is continuous in each measurement process.
A flow rate measuring method comprising further including an abnormality handling step in which an abnormality processing is performed when an abnormality is determined in the determination step. In the flow rate measuring method according to claim 7,
A calculation step configured to obtain the ratio of the number interpolated by the interpolation step to the number of zero cross times in the time array stored in the measurement step.
A determination step configured to determine whether or not the ratio calculated in the calculation step exceeds the set upper limit value, and
A flow rate measuring method comprising further including an abnormality handling step in which an abnormality processing is performed when the determination step is determined to be abnormal. In the flow rate measuring method according to claim 7 or 8.
The abnormal processing step is a flow rate measuring method comprising either stopping the measurement of the flow rate of the fluid or recalculating the flow rate of the fluid. In the flow rate measuring method according to claim 7 or 8.
The abnormality processing step is a flow rate measuring method characterized in that a plurality of zero cross times stored in the measurement step when it is determined to be abnormal in the determination step are excluded from the calculation target.

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