TWI846492B - Hybrid ultrasonic flowmeter and its measurement method - Google Patents

Abstract

A hybrid ultrasonic flowmeter and a measurement method for the hybrid ultrasonic flowmeter are provided. The hybrid ultrasonic flowmeter includes a first sensor, a second sensor, and a processing circuit. The processing circuit is configured to compute a combination of signals of different TOF frequencies and signals of different PWD frequencies to generate a plurality of testing modes and operate at least one of a plurality of testing modes to decide an operation mode from the plurality of testing modes; and control the first sensor and the second sensor to operate one of TOF measurement and PWD measurement to measure a flow of liquid.

Description

Hybrid ultrasonic flowmeter and measurement method

This case is about a flow meter and a measurement method, in particular, about a mixed wave ultrasonic flow meter and a measurement and application method of a mixed wave ultrasonic flow meter.

Existing ultrasonic flow meters can use the time difference method or the Doppler method to measure the flow velocity and flow rate of liquids. Although both the time difference method and the Doppler method can be used to measure the flow velocity and flow rate of liquids, if the ultrasonic flow meter uses the time difference method to measure liquids with bubbles or particles, the measured flow velocity and flow rate of the liquid will be inaccurate. Similarly, if the ultrasonic flow meter uses the Doppler method to measure liquids without bubbles or particles, the measured flow velocity will be inaccurate.

Existing ultrasonic flowmeters cannot be dynamically applied to the measurement of flow rate and flow rate of liquids of various properties, and there is a need for improvement.

According to an embodiment of the present invention, a hybrid ultrasonic flowmeter is disclosed, which is suitable for measuring the flow rate of a liquid. The hybrid ultrasonic flowmeter includes a first sensor, a second sensor, a switch, and a processing circuit. The first sensor and the second sensor are configured to send a signal of a TOF frequency and receive a TOF signal in a time difference method (TOF) measurement and to send a signal of a PWD frequency and receive a PWD signal in a Doppler method (PWD) measurement. The switch is coupled to the first sensor and the second sensor, and is configured to switch the first sensor and the second sensor between the TOF measurement and the PWD measurement. The processing circuit is coupled to the switch and is configured to: when operating in a verification phase, utilize a plurality of TOF signals with different TOF frequencies and a plurality of PWD signals with different PWD frequencies to form a plurality of measurement modes, and execute at least one of the plurality of measurement modes through the first sensor and the second sensor to determine an operation mode and a usage frequency corresponding to the TOF signal or the PWD signal from the measurement modes; and in the operation mode of the measurement phase, control the first sensor and the second sensor to emit one of the TOF signal with the TOF frequency and the PWD signal with the PWD frequency, and execute at least one of the corresponding TOF measurement and PWD measurement to measure the flow rate of the liquid.

According to an embodiment of the present case, a measurement method for an ultrasonic flow meter to measure a liquid flow rate is disclosed, wherein the ultrasonic flow meter includes a first sensor, a second sensor and a processing circuit, the first sensor and the second sensor send a signal of a TOF frequency and receive a TOF signal in a time difference method (TOF) measurement, and send a signal of a PWD frequency and receive a PWD signal in a Doppler method (PWD) measurement. The measurement method includes: when the ultrasonic flowmeter operates in a verification phase, a plurality of TOF signals with different TOF frequencies and a plurality of PWD signals with different PWD frequencies are arranged and combined into a plurality of measurement modes, and at least one of the plurality of measurement modes is executed to determine an operation mode and a usage frequency corresponding to the TOF signal or the PWD signal from the measurement modes; and a processing circuit is used to control the first sensor and the second sensor to emit one of the TOF signal with the TOF frequency and the PWD signal with the PWD frequency in the operation mode of the measurement phase, and at least one of the corresponding TOF measurement and PWD measurement is executed to measure the flow rate of the liquid.

110: Pipeline

121, 131, 141: Sensors

125, 135, 143, 145: Signals

165: Flow direction

300: Hybrid ultrasonic flowmeter

311: First sensor

321: Second sensor

330:Signal sending module

331: First transmission circuit

333: Second transmission circuit

340:Signal receiving module

341: First receiving circuit

343: Second receiving circuit

350: Processing circuit

355: Control signal

360:Switch

915: Dead Zone

S410~S460: Steps

T1: First time interval

T2: Second time interval

L1, L2: curve

BD-L1: First threshold value

BD-L2: Second threshold value

Figure 1 is a schematic diagram of the flow meter setting that uses the time difference method to measure the flow rate of the liquid.

Figure 2 is a schematic diagram of the flow meter setting for measuring liquid flow rate using the Doppler method.

FIG3 is a circuit block diagram of a hybrid ultrasonic flowmeter according to an embodiment of the present invention.

FIG4 is a flow chart of a flow meter according to an embodiment of the present invention for determining an operating mode in a verification phase to use the operating mode to measure the flow rate of a liquid.

Figure 5 is a signal timing diagram of the first measurement mode according to an embodiment of the present invention.

Figure 6 is a signal timing diagram of the second measurement mode according to an embodiment of the present invention.

FIG7 is a signal timing diagram of the third measurement mode according to an embodiment of the present invention.

FIG8 is a signal timing diagram of the fourth measurement mode according to an embodiment of the present invention.

Figure 9 is a graph showing the relationship between the flow rate of the liquid and the density of impurities in the liquid according to an embodiment of the present invention.

The following further describes the present invention in combination with the drawings and embodiments, so that relevant personnel in the technical field to which the present invention belongs can better understand the present invention and implement it accordingly, but the embodiments are not intended to limit the present invention.

As used herein, terms such as "first", "second", "third", "fourth", and "fifth" describe various elements, components, regions, layers, and/or parts, which should not be limited by these terms. These terms may only be used to distinguish one element, component, region, layer, or part from another. Unless the context clearly indicates otherwise, the terms such as "first", "second", "third", "fourth", and "fifth" used herein do not imply a sequence or order.

The measurement technologies of ultrasonic flowmeters include Time of Flight (TOF) and Pulsed Wave Doppler (PWD). Each of these two measurement technologies has its own suitable application field. In detail, the Time of Flight is suitable for measuring the flow rate of liquids without impurities (such as bubbles or particles), and the Doppler method is suitable for measuring the flow rate of liquids with impurities (such as bubbles or particles). It is worth mentioning that after the flowmeter calculates the flow rate, the flow rate of the liquid can be further calculated. This case does not limit the formulas designed based on the principles of the Time of Flight and Doppler methods for calculating the flow rate and flow rate of liquids.

To facilitate understanding of this case, the flow velocity measurement principles of the time difference method and the Doppler method are explained below.

Please refer to FIG. 1, which is a schematic diagram of the setting of a flow meter that uses the time difference method (TOF) to measure the flow rate of a liquid. As shown in FIG. 1, the liquid flows in the pipe 110, and has a flow direction 165, for example, from left to right. Sensors (transducers) 121 and 131 are set on the pipe 110. The sensors 121 and 131 can respectively transmit a signal (ultrasonic signal) of a frequency, and can respectively receive a signal (ultrasonic signal) transmitted by another sensor.

Specifically, sensors 121 and 131 simultaneously emit signals of the same frequency (e.g., 3 MHz). The signal emitted by sensor 121 propagates in pipe 110, and after a period of time, sensor 131 receives the signal emitted by sensor 121. Similarly, sensor 121 also receives the signal emitted by sensor 131 after a period of time. Since the flow speed and flow direction of the liquid are in the same direction as the propagation direction of signal 125 emitted by sensor 121 (e.g., both are toward the right side of pipe 110), sensor 131 receives signal 125 earlier than sensor 121 receives signal 135. In contrast, the flow speed and flow direction of the liquid are in the opposite direction to the propagation direction of the signal 135 emitted by the sensor 131, so the time when the sensor 121 receives the signal 135 is later than the time when the sensor 131 receives the signal 125.

In the calculation of the time difference method, the computing device (not shown) calculates the flow velocity and flow rate of the liquid in the pipeline 110 (i.e., the measurement value obtained by the flow meter using a frequency of 3MHz) based on the time difference between the sensors 121 and 131 receiving the signals 125 and 135 respectively. It is worth mentioning that this case does not limit the formula for calculating the flow velocity and flow rate designed based on the principle of the time difference method.

It should be noted that the arrangement of the flow meter shown in FIG. 1 is only an example. The two sensors 121 and 131 are arranged on opposite sides of the outer wall of the pipe 110, so that the signal emitted by the sensor 121 propagates in the liquid without being reflected by the pipe 110. In another embodiment, the two sensors are arranged on the outer wall of the pipe 110, and the signal emitted by one of the sensors is reflected by the wall of the pipe 110, while the other sensor receives the reflected signal. In other words, the present case does not limit the position of the sensors 121 and 131 in FIG. 1 to be arranged on the pipe 110.

Please refer to FIG. 2, which is a schematic diagram of the setting of a flow meter that uses the Doppler method (Pulsed Wave Doppler, PWD) to measure the flow rate of a liquid. As shown in FIG. 2, the liquid flows in the pipe 110, and has a flow direction 165, for example, flowing from left to right. A sensor 141 is set on the pipe 110. The sensor 141 can transmit a signal (ultrasonic signal) and receive a signal (ultrasonic signal).

Specifically, the sensor 141 emits a signal 143 with a frequency (e.g., 3.33MHz), and the signal 143 propagates in the pipe 110. If there are impurities in the liquid (bubbles, oil droplets, sand and gravel, foreign solids, etc., solid, gas, and liquid phases that are not fused in the measured "liquid"), the signal 143 will be reflected when it contacts the impurities and form a reflection signal 145. The sensor 141 will receive this reflection signal 145.

Impurities are mixed in the liquid and flow with the liquid. Since the volume of the impurities is extremely small (e.g., the diameter is about 0.3 mm), the movement speed of the impurities can be regarded as consistent with the flow rate of the liquid. Based on the Doppler effect, the frequency of the signal 143 emitted by the sensor 141 and the received reflected signal 145 will form a Doppler shift. Therefore, in the calculation of the Doppler method, the calculation device (not shown) calculates the flow rate of the liquid in the pipe 110 based on the frequency shift of the signal 143 emitted by the sensor 141 and the received reflected signal 145.

In some cases, the content of the liquid in the pipe 110 of FIG. 1 or FIG. 2 may change. For example, in the case where the liquid in the pipe 110 is free of impurities, the user generally selects the flow meter of FIG. 1 (suitable for measuring liquid without impurities) in combination with the time difference method to measure the flow rate of the liquid. After a period of time, if the liquid flowing through the pipe 110 gradually contains impurities, the result measured by the flow meter of FIG. 1 will be inaccurate. On the contrary, in the case where the liquid in the pipe 110 contains impurities, the user generally selects the flow meter of FIG. 2 (suitable for measuring liquid with impurities) in combination with the Doppler method to measure the flow rate of the liquid. After a period of time, if the liquid flowing through the pipe 110 gradually becomes free of impurities, the result measured by the flow meter in Figure 2 will be inaccurate.

This case proposes a flow meter suitable for measuring liquids with impurities (bubbles or particles) or without impurities, which can automatically switch to a suitable measurement mode (it is worth mentioning that "suitable measurement mode" refers to a mode that can measure the correct flow rate). Therefore, regardless of the nature of the liquid in the pipeline 110 (for example, whether there are impurities), the flow meter of this case can correctly measure the flow rate of the liquid.

To facilitate the description of the measurement method and frequency of use of the flow meter, the following technical terms used in this case are explained: the technical term "TOF measurement" refers to the measurement method of the flow meter as the time difference method (as shown in Figure 1); the technical term "PWD measurement" refers to the measurement method of the flow meter as the Doppler method (as shown in Figure 2); The technical terms "first TOF frequency", "second TOF frequency" and "third TOF frequency" refer to the different frequencies used by the flow meter in the time difference method; the technical terms "first PWD frequency", "second PWD frequency" and "third PWD frequency" refer to the different frequencies used by the flow meter in the time difference method. "The signal of the first TOF frequency", "the signal of the second TOF frequency" and "the signal of the third TOF frequency" refer to the different frequencies used by the flow meter in the Doppler method; the technical terms "the signal of the first TOF frequency", "the signal of the second TOF frequency" and "the signal of the third TOF frequency" refer to the flow meter in the time difference method, the sensor sends the first TOF frequency, the second TOF frequency and the third TOF frequency signals; the technical terms "the signal of the first PWD frequency", "the signal of the second PWD frequency" and "the signal of the third PWD frequency" refer to the flow meter in the Doppler method, the sensor sends the first PWD frequency, the second PWD frequency and the third PWD frequency signals. The technical terms "first TOF signal", "second TOF signal" and "third TOF signal" refer to TOF signals of the first TOF frequency, the second TOF frequency and the third TOF frequency received by the sensor of the flow meter in the time difference method; the technical terms "first PWD signal", "second PWD signal" and "third PWD signal" refer to PWD signals of the first PWD frequency, the second PWD frequency and the third PWD frequency received by the sensor of the flow meter in the Doppler method; The technical terms "first TOF measurement value", "second TOF measurement value" and "third TOF measurement value" refer to the measurement values calculated by the flow meter using different frequencies such as "first TOF frequency", "second TOF frequency" and "third TOF frequency" in the time difference method; the technical terms "first PWD measurement value", "second PWD measurement value" and "third PWD measurement value" refer to the measurement values calculated by the flow meter using different frequencies such as "first PWD frequency", "second PWD frequency" and "third PWD frequency" in the Doppler method.

Please refer to FIG. 3, which is a circuit block diagram of a hybrid ultrasonic flowmeter according to an embodiment of the present invention. The hybrid ultrasonic flowmeter 300 (hereinafter referred to as the flowmeter) includes a first sensor 311, a second sensor 321, a signal transmission module 330, a signal receiving module 340, a processing module 350 and a switch 360. The first sensor 311 and the second sensor 321 are coupled to the switch 360. The switch 360 is coupled to the signal transmission module 330, the signal receiving module 340 and the processing circuit 350. The signal transmission module 330 and the signal receiving module 340 are coupled to the processing circuit 350.

In one embodiment, the configuration of the flow meter 300 in FIG. 3 is as described in FIG. 1 , for example, the first sensor 311 is set at the position of the sensor 121 and the second sensor 321 is set at the position of the sensor 131. To simplify the content of the manual, it will not be repeated here.

In the TOF measurement, when transmitting the signal, the processing circuit 350 sends a control signal 355 to the switch 360 to switch the first sensor 311 and the second sensor 321 to the mode of transmitting the signal for TOF measurement. On the other hand, the processing circuit 350 controls the first sensor 311 and the second sensor 321 to simultaneously transmit the signal of the same TOF frequency through the first transmitting circuit 331 and the second transmitting circuit 333 of the signal transmitting module 330.

In TOF measurement, when receiving a signal, the processing circuit 350 sends a control signal 355 to the switch 360 to switch the first sensor 311 and the second sensor 321 to the mode of receiving the signal for TOF measurement. On the other hand, the processing circuit 350 controls the first sensor 311 and the second sensor 321 to receive the TOF signal respectively through the first receiving circuit 341 and the second receiving circuit 343 of the signal receiving module 340.

In one embodiment, the processing circuit 350 calculates the flow rate and flow rate of the liquid in the pipeline 110 based on the time difference between the two TOF signals received by the first sensor 311 and the second sensor 321.

In one embodiment, in PWD measurement, the flow meter 300 uses one of the first sensor 311 and the second sensor 321. To simplify the description, the first sensor 311 is used as an example below. Specifically, the configuration of the flow meter 300 in FIG. 3 is as shown in FIG. 2, for example, the first sensor 311 is set at the position of the sensor 141. To simplify the content of the manual, it will not be repeated here.

In PWD measurement, when transmitting a signal, the processing circuit 350 sends a control signal 355 to the switch 360 to switch the first sensor 311 to the mode of transmitting a signal for PWD measurement. On the other hand, the processing circuit 350 controls the first sensor 311 to send a signal of the PWD frequency through the first transmitting circuit 331 of the signal transmitting module 330.

In PWD measurement, when receiving a signal, the processing circuit 350 sends a control signal 355 to the switch 360 to switch the first sensor 311 to the mode of receiving the signal for PWD measurement. On the other hand, the processing circuit 350 controls the first sensor 311 to receive the PWD signal through the first receiving circuit 341 of the signal receiving module 340.

In one embodiment, the processing circuit 350 obtains the frequency shift of the two signals based on the PWD frequency signal emitted by the first sensor 311 and the received PWD signal to calculate the flow rate and flow rate of the liquid in the pipeline 110.

In one embodiment, the operation of the flow meter 300 includes a verification phase and a measurement phase.

During the verification phase, the flow meter 300 will execute multiple pre-designed measurement modes to obtain multiple measurement values, and then use the obtained multiple measurement values to determine which measurement mode to use as the operating mode. The details of the multiple measurement modes will be described later.

After determining the operating mode to be used, the flow meter 300 operates in the measurement phase. In the measurement phase, the flow meter 300 measures the flow rate and flow rate of the liquid in the pipeline 110 in the aforementioned determined operating mode.

In other words, the flow meter 300 uses multiple different measurement modes to evaluate which measurement is most suitable for the properties of the current liquid (i.e., it can correctly measure the flow rate and flow rate of the liquid) during the verification phase, and then uses the most suitable measurement mode as the operating mode during the measurement phase to measure the flow rate and flow rate of the liquid and output it for the user's reference.

In one embodiment, if the flow meter 300 determines that the measurement efficiency is poor (for example, the measurement value suddenly drops), it switches from the measurement phase to the verification phase to re-determine the operation mode.

In one embodiment, the flow meter 300 sequentially executes multiple measurement modes during the verification phase, each measurement mode including one or more TOF frequency tests and/or one or more PWD frequency tests. In one embodiment, the measurement mode is a mode formed by the arrangement and combination of multiple TOF signals with different TOF frequencies and multiple PWD signals with different PWD frequencies. To facilitate understanding of the content of this case, the detailed operations of the TOF frequency test and the PWD frequency test are described below.

For example, the measurement mode includes three TOF frequency tests and one PWD frequency test, which means that the flow meter 300 performs TOF measurement at the first TOF frequency, the second TOF frequency, and the third TOF frequency and performs PWD measurement at a PWD frequency in sequence, and obtains three TOF measurement values and one PWD measurement value respectively. TOF measurement and PWD measurement have been described above (as shown in Figures 1 and 2), and will not be repeated here.

In one embodiment, the first TOF frequency may be 2MHz, the second TOF frequency may be 3.125MHz, the third TOF frequency may be 3.84MHz; the PWD frequency may be 3.33MHz.

The verification phase of this case is illustrated by four measurement modes, but this case does not limit the number of measurement modes in the verification phase, and more or less than four measurement modes can be designed based on actual applications.

Please refer to Figure 4, which is a flow chart of a flow meter according to an embodiment of the present case, which determines the operating mode in the verification stage to use the operating mode to measure the liquid flow rate.

In step S410, the flow meter 300 performs a verification phase.

In one embodiment, when the flow meter 300 operates in the verification phase, multiple TOF signals with different TOF frequencies and multiple PWD signals with different PWD frequencies are arranged and combined into multiple measurement modes.

In one embodiment, the flow meter 300 can randomly select a measurement mode from the four measurement modes or execute in the order of the first measurement mode, the second measurement mode, etc.

To facilitate understanding of this case, the following description is based on the sequence of steps S421 to S424, but the measurement method used by the flow meter 300 in this case is not limited to this sequence.

In step S421, the flow meter 300 performs the first measurement mode in the verification phase.

In the first measurement mode, the flow meter 300 uses the maximum frequency and the minimum frequency in the TOF measurement, and then decides whether to further measure with PWD according to the calculated TOF measurement value, and finally decides the measurement method to be used in the measurement phase and the usage frequency for TOF measurement and PWD measurement. In one embodiment, the first measurement mode includes using a first TOF frequency and a second TOF frequency in the TOF measurement, wherein the first TOF frequency is the minimum frequency used by the flow meter 300, and the second TOF frequency is the maximum frequency used by the flow meter 300. For example, the TOF frequencies available for the flow meter 300 include 2MHz, 3.15MHz, 3.84MHz and 4.166MHz, of which the minimum frequency available for the flow meter 300 is 2MHz, and the maximum frequency available for the flow meter 300 is 4.166MHz.

In one embodiment, the first sensor 311 and the second sensor 321 simultaneously transmit signals according to a first transmission time interval, wherein the first sensor 311 and the second sensor 321 sequentially and repeatedly transmit signals of the first TOF frequency, the second TOF frequency, the first TOF frequency, and the second TOF frequency. The first sensor 311 and the second sensor 321 repeatedly transmit signals in the above-mentioned signal transmission pattern.

In one embodiment, the first transmission time interval is a pulse repetition interval (PRI). The first transmission time interval is, for example, 350 microseconds (μs).

For example, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the first TOF frequency. After an interval of 350 microseconds, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the second TOF frequency. After an interval of 350 microseconds, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the first TOF frequency, and so on.

In the above example, the first sensor 311 and the second sensor 321 receive multiple TOF signals such as the first TOF signal and the second TOF signal, respectively, wherein the TOF signal received by the first sensor 311 is sent by the second sensor 321, and the TOF signal received by the second sensor 321 is sent by the first sensor 311. The processing circuit 350 calculates the first TOF measurement value according to the time difference between the two first TOF signals received by the first sensor 311 and the second sensor 321, and calculates the second TOF measurement value according to the time difference between the two second TOF signals received by the first sensor 311 and the second sensor 321.

In one embodiment, the processing circuit 350 determines whether at least one of the multiple TOF measurement values meets a first threshold condition (e.g., greater than a preset threshold value). If at least one of these TOF measurement values meets the first threshold condition, there is no need to further perform PWD measurement in the first measurement mode of the verification phase.

For example, if the first TOF measurement value or the second TOF measurement value is greater than the preset threshold value, the processing circuit 350 does not need to further perform PWD measurement even if the other TOF measurement value is not greater than the preset threshold value.

In one embodiment, the processing circuit 350 sets the usage frequency of the operation mode from a plurality of TOF measurement values (e.g., a plurality of first TOF measurement values and a plurality of second TOF measurement values) according to a second threshold condition (e.g., selecting the maximum measurement value).

In the above example, if the first TOF measurement value (e.g., the average value of multiple first TOF measurement values calculated at different time points) is the maximum value among all calculated TOF measurement values, the processing circuit 350 will set the first TOF frequency as the usage frequency of the operation mode. At this time, the processing circuit 350 will not further perform PWD measurement.

In another embodiment, if the processing circuit 350 determines that multiple TOF measurement values do not meet the first threshold condition, it means that the TOF measurement values of the maximum frequency and the minimum frequency used by the flow meter 300 in the TOF measurement may be inaccurate (for example, the average value of the TOF measurement value is lower than the preset threshold value). In this embodiment, the processing circuit 350 further adds PWD measurement to the first measurement mode of the verification stage to determine whether to use TOF measurement or PWD measurement, so as to evaluate whether PWD measurement is more suitable than TOF measurement for measuring the current liquid in the current liquid properties, or whether TOF measurement is still a more suitable measurement method.

In this embodiment, the first measurement mode includes using the first TOF frequency and the second TOF frequency in TOF measurement and using the first PWD frequency in PWD measurement.

Please refer to Figure 5, which is a signal timing diagram of the first measurement mode drawn according to an embodiment of the present invention.

In one embodiment, the first sensor 311 and the second sensor 321 first send signals simultaneously according to the first transmission time interval T1, and then the first sensor 311 sends a signal alone according to the second transmission time interval T2. Specifically, the first sensor 311 and the second sensor 321 sequentially and repeatedly send signals of the first TOF frequency and the second TOF frequency based on the first transmission time interval T1, and then the first sensor 311 sends a signal of the first PWD frequency alone based on the second transmission time interval T2. The above is regarded as a loop, and the first sensor 311 and the second sensor 321 repeatedly send signals with the above signal transmission pattern (first TOF frequency, second TOF frequency and first PWD frequency).

The first PWD frequency is, for example, 3.33 MHz.

In one embodiment, the second transmission time interval T2 is a pulse repetition interval (PRI). The second transmission time interval is, for example, 70 microseconds.

For example, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the first TOF frequency. After an interval of 350 microseconds, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the second TOF frequency. After an interval of 70 microseconds, the first sensor 311 sends out a signal of the first PWD frequency. After an interval of 350 microseconds, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the first TOF frequency, and so on.

In the above example, the first sensor 311 and the second sensor 321 receive the first TOF signal and the second TOF signal respectively, wherein the first TOF signal and the second TOF signal received by the first sensor 311 are sent by the second sensor 321, and the first TOF signal and the second TOF signal received by the second sensor 321 are sent by the first sensor 311. The processing circuit 350 calculates the first TOF measurement value according to the time difference between the two first TOF signals received by the first sensor 311 and the second sensor 321 respectively, and calculates the second TOF measurement value according to the time difference between the two second TOF signals received by the first sensor 311 and the second sensor 321 respectively.

In the above example, after a period of time has passed since the first sensor 311 sent out a signal of the first PWD frequency, the first sensor 311 will receive the first PWD signal.

The processing circuit 350 calculates the first PWD measurement value based on the first PWD frequency signal sent by the first sensor 311 and the frequency shift of the received first PWD signal.

In one embodiment, the flow meter 300 determines whether at least one of the multiple TOF measurement values and PWD measurement values meets the first threshold condition (e.g., greater than a preset threshold value). If at least one of these TOF measurement values and PWD measurement values meets the first threshold condition, the processing circuit 350 does not need to change to other measurement modes in the verification phase to check whether there are other more suitable signal transmission patterns.

In one embodiment, the processing circuit 350 sets one of the TOF measurement and the PWD measurement as an operating mode according to the second threshold condition, and sets a usage frequency corresponding to the TOF signal and the PWD signal. For example, the processing circuit 350 selects the largest one from the TOF signal and the PWD signal according to the size of the signal, calculates the average value of multiple measurement values and selects the usage frequency according to the maximum value of the average value, or calculates the standard deviation of multiple measurement values and selects the usage frequency according to the minimum value in the standard deviation, etc. (detailed description below). In this embodiment, the second threshold condition is the largest signal, the maximum value of the average value, or the minimum value of the standard deviation, etc.

In one embodiment, the processing circuit 350 uses the maximum of the first TOF measurement value (e.g., the average value of multiple first TOF measurement values calculated at different time points as the first TOF measurement value for comparison), the second TOF measurement value (e.g., the average value of multiple second TOF measurement values calculated at different time points as the second TOF measurement value for comparison), and the first PWD measurement value (e.g., the average value of multiple first PWD measurement values calculated at different time points as the first PWD measurement value for comparison) as the usage frequency.

In the above example, if the first PWD measurement value is the maximum value among all the measurement values, the processing circuit 350 will use PWD measurement as the measurement method of the first measurement mode and set the first PWD frequency as the use frequency.

In another embodiment, the processing circuit 350 uses the smallest of the first TOF measurement value (e.g., the standard deviation of multiple first TOF measurement values calculated at different time points as the first TOF measurement value for comparison), the second TOF measurement value (e.g., the standard deviation of multiple second TOF measurement values calculated at different time points as the second TOF measurement value for comparison), and the first PWD measurement value (e.g., the standard deviation of multiple first PWD measurement values calculated at different time points as the first PWD measurement value for comparison) as the usage frequency.

In yet another embodiment, the flow meter 300 directly compares the magnitude of the TOF signal and the PWD signal to determine the usage frequency. For example, the flow meter 300 obtains the first TOF signal, the second TOF signal, and the first PWD signal in a time sequence, and the processing circuit 350 compares the signal magnitudes of the first TOF signal and the second TOF signal. If the second TOF signal is greater than the first TOF signal, the signal magnitudes of the second TOF signal and the first PWD signal are compared, and so on. If after a period of time, the second TOF signal currently obtained is the maximum value (greater than the first TOF signal and the first PWD signal), the processing circuit 350 sets the second TOF frequency as the usage frequency.

In the above example, if the second TOF measurement value is the maximum value among all the measurement values, the processing circuit 350 will use TOF measurement as the measurement method of the first measurement mode and set the second TOF frequency as the use frequency.

In the above example, if the first measurement mode is selected as the operation mode in the verification phase, the flow meter 300 will use the second TOF frequency to perform TOF measurement in the measurement phase to measure the flow rate and flow rate of the liquid in the pipeline 110.

It is worth mentioning that the design of the first measurement mode is to quickly evaluate whether the properties of the liquid are suitable for TOF measurement by testing the maximum TOF frequency and the minimum TOF frequency used by the first sensor 311 and the second sensor 321. If the TOF measurement is suitable for the current properties of the liquid, the PWD measurement is not further evaluated. If the TOF measurement is not suitable for the current properties of the liquid, the PWD measurement is further evaluated to confirm whether the Doppler measurement is a more suitable measurement method. Accordingly, the present case can be adjusted to the most suitable measurement method in real time and dynamically.

In another embodiment, if the processing circuit 350 determines that all TOF measurement values and PWD measurement values do not meet the first threshold condition (indicating that the first measurement mode is not suitable for measuring the current liquid), it is necessary to execute other measurement modes in the verification stage (step S430).

In step S422, the flow meter 300 performs the second measurement mode in the verification phase.

In the second measurement mode, the flow meter 300 alternately uses TOF measurement and PWD measurement (without changing the emission frequency of TOF measurement and PWD measurement), and then determines the measurement method and the frequency of use for TOF measurement and PWD measurement based on the calculated TOF measurement value and PWD measurement value.

In one embodiment, the second measurement mode includes using a third TOF frequency in TOF measurement and using a second PWD frequency in PWD measurement.

Please refer to Figure 6, which is a signal timing diagram of the second measurement mode drawn according to an embodiment of the present invention.

In one embodiment, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the third TOF frequency. After the second transmission time interval T2, the first sensor 311 sends out a signal of the second PWD frequency. After the first transmission time interval T1, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the third TOF frequency. The above is regarded as a loop, and the second sensor 321 and/or the first sensor 311 repeatedly send out signals with the above signal transmission pattern (third TOF frequency and second PWD frequency).

In the above example, the processing circuit 350 sequentially calculates the third TOF measurement value, the second PWD measurement value, the third TOF measurement value, and the second PWD measurement value, etc.

In one embodiment, the processing circuit 350 determines whether at least one of the third TOF measurement value and the second PWD satisfies a first threshold condition (e.g., greater than a preset threshold value). If at least one of the third TOF measurement value and the second PWD value satisfies the first threshold condition, the processing circuit 350 does not need to change to other measurement modes in the verification phase to check whether there are other more suitable signal transmission patterns.

In one embodiment, the processing circuit 350 sets one of the TOF measurement and the PWD measurement to an operating mode according to the second threshold value condition, and sets a usage frequency. Please refer to the above description for this embodiment, which will not be repeated here.

In one embodiment, the processing circuit 350 uses the maximum of the third TOF measurement value and the second PWD measurement value as the usage frequency. Please refer to the above description for the content of the second threshold condition, which will not be repeated here.

In the above example, after the flow meter 300 operates in the second measurement mode for a period of time, if the second PWD measurement value is greater than the third TOF measurement value, the processing circuit 350 will use PWD measurement as the measurement method of the second measurement mode and set the second PWD frequency as the use frequency.

Therefore, if the second measurement mode is selected as the operation mode during the verification phase, the flow meter 300 will use the second PWD frequency to perform PWD measurement during the measurement phase to measure the flow rate and flow rate of the liquid in the pipeline 110.

It is worth mentioning that the second measurement mode is designed to alternately use the time difference method and the Doppler method, and after a period of time, determine which of the time difference method and the Doppler method is most suitable for measuring liquids based on the measured value. Based on this, this case can be adjusted to the most suitable measurement method in real time and dynamically.

In another embodiment, if the processing circuit 350 determines that all TOF measurement values and PWD measurement values do not meet the first threshold condition (indicating that the second measurement mode is not suitable for measuring the current liquid), it is necessary to execute other measurement modes in the verification stage (step S430).

In step S423, the flow meter 300 performs the third measurement mode in the verification phase.

In the third measurement mode, the flow meter 300 uses TOF measurement at different frequencies in sequence, and then determines the frequency of TOF measurement based on the calculated TOF measurement value.

In one embodiment, the third measurement mode includes using multiple TOF frequencies in TOF measurement. The multiple TOF frequencies include a fourth TOF frequency, a fifth TOF frequency, and a sixth TOF frequency.

Please refer to Figure 7, which is a signal timing diagram of the third measurement mode drawn according to an embodiment of the present invention.

In one embodiment, the first sensor 311 and the second sensor 321 simultaneously send signals according to the first transmission time interval T1. Specifically, the first sensor 311 and the second sensor 321 sequentially and repeatedly send signals of the fourth TOF frequency, the fifth TOF frequency, the sixth TOF frequency, the fourth TOF frequency, and the fifth TOF frequency based on the first transmission time interval T1. The first sensor 311 and the second sensor 321 repeatedly send signals in the above signal transmission mode.

In the above example, the processing circuit 350 sequentially calculates the fourth TOF measurement value, the fifth TOF measurement value, and the sixth TOF measurement value, etc.

In one embodiment, the processing circuit 350 determines whether at least one of the fourth TOF measurement value, the fifth TOF measurement value, and the sixth TOF measurement value meets the first threshold condition (e.g., greater than a preset threshold value). If at least one of the fourth TOF measurement value, the fifth TOF measurement value, and the sixth TOF measurement value meets the first threshold condition, the processing circuit 350 does not need to change to other measurement modes in the verification phase to check whether there are other more suitable signal transmission patterns.

In one embodiment, the processing circuit 350 selects the third measurement mode as the operating mode and sets a usage frequency according to the second threshold condition.

In one embodiment, the processing circuit 350 uses the maximum of the fourth TOF measurement value, the fifth TOF measurement value, and the sixth TOF measurement value as the usage frequency. Please refer to the above description for the content of the second threshold condition, which will not be repeated here.

In the above example, if the sixth TOF measurement value is the maximum value among all the measurement values, the processing circuit 350 will set the sixth TOF frequency as the use frequency.

Therefore, in the above example, if the third measurement mode is selected as the operation mode in the verification phase, the flow meter 300 will use the sixth TOF frequency to perform TOF measurement in the measurement phase to measure the flow rate and flow rate of the liquid in the pipeline 110.

It is worth mentioning that the third test mode is designed to use multiple different frequencies in the time difference method measurement for evaluation, and select the frequency that can measure the most accurately for measurement. Based on this, this case can be adjusted to the most suitable measurement method in real time and dynamically.

In another embodiment, if the processing circuit 350 determines that all TOF measurement values do not meet the first threshold condition (indicating that the third measurement mode is not suitable for measuring the current liquid), other measurement modes need to be executed in the verification stage (step S430).

In step S424, the flow meter 300 performs the fourth measurement mode in the verification phase.

In the fourth measurement mode, the flow meter 300 sequentially uses TOF measurement and PWD measurement at different frequencies, and then determines the measurement method and the frequency of use for TOF measurement and PWD measurement based on the calculated statistics of TOF measurement values and PWD measurement values.

In one embodiment, the statistical value includes a mean, a standard deviation, a median, or other statistics.

In one embodiment, the fourth measurement mode includes using multiple TOF frequencies in TOF measurement and using the third PWD frequency in PWD measurement. The multiple TOF frequencies include the seventh TOF frequency, the eighth TOF frequency, and the ninth TOF frequency.

Please refer to Figure 8, which is a signal timing diagram of the fourth measurement mode drawn according to an embodiment of the present invention.

In one embodiment, the first sensor 311 and the second sensor 321 first send signals simultaneously according to the first transmission time interval T1, and then the first sensor 311 sends signals alone according to the second transmission time interval T2. Specifically, the first sensor 311 and the second sensor 321 sequentially and repeatedly send signals of the seventh TOF frequency, the eighth TOF frequency, and the ninth TOF frequency based on the first transmission time interval T1, and then the first sensor 311 sends a signal of the third PWD frequency based on the second transmission time interval T2. The above is used as a loop, and the first sensor 311 and the second sensor 321 repeatedly send signals in the above signal transmission pattern (the seventh TOF frequency, the eighth TOF frequency, the ninth TOF frequency and the third PWD frequency).

For example, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the seventh TOF frequency. After an interval of 350 microseconds, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the eighth TOF frequency. After an interval of 350 microseconds, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the ninth TOF frequency. After an interval of 70 microseconds, the first sensor 311 sends out a signal of the third PWD frequency. After another interval of 350 microseconds, the first sensor 311 and the second sensor 321 simultaneously send out a signal of the seventh TOF frequency, and so on.

In the above example, the first sensor 311 and the second sensor 321 receive the seventh TOF signal, the eighth TOF signal and the ninth TOF signal respectively. The processing circuit 350 calculates the seventh TOF measurement value according to the time difference between the two seventh TOF signals received by the first sensor 311 and the second sensor 321 respectively, calculates the eighth TOF measurement value according to the time difference between the two eighth TOF signals received by the first sensor 311 and the second sensor 321 respectively, and calculates the ninth TOF measurement value according to the time difference between the two ninth TOF signals received by the first sensor 311 and the second sensor 321 respectively.

In the above example, after a period of time has passed since the first sensor 311 sent out a signal of the third PWD frequency, the first sensor 311 will receive the third PWD signal.

The processing circuit 350 calculates the third PWD measurement value based on the third PWD frequency signal sent by the first sensor 311 and the frequency shift of the received third PWD signal.

In one embodiment, the flow meter 300 determines whether at least one of the multiple TOF measurement values and PWD measurement values meets the first threshold condition (e.g., greater than a preset threshold value). If at least one of these TOF measurement values and PWD measurement values meets the first threshold condition, the processing circuit 350 does not need to change to other measurement modes in the verification phase to check whether there are other more suitable signal transmission patterns.

In one embodiment, the processing circuit 350 sets one of the TOF measurement and the PWD measurement to an operating mode according to the second threshold value condition, and sets a usage frequency (step S440).

In one embodiment, the processing circuit 350 uses the largest of the seventh TOF measurement value, the eighth TOF measurement value, the ninth TOF measurement value, and the third PWD measurement value as the usage frequency. Please refer to the above description for this embodiment, which will not be repeated here.

In the above example, if the eighth TOF measurement value is the maximum value, the processing circuit 350 will use TOF measurement as the measurement method of the fourth measurement mode and set the eighth TOF frequency as the use frequency.

Therefore, if the fourth measurement mode is selected as the operating mode during the verification phase, the flow meter 300 will use the eighth TOF frequency to perform TOF measurement during the measurement phase to measure the flow rate and flow rate of the liquid in the pipeline 110.

In another embodiment, the flow meter 300 directly compares the size of the TOF signal or the PWD signal instead of comparing the size of the measured value to determine the frequency of use. For example, the flow meter 300 obtains the seventh TOF signal, the eighth TOF signal, the ninth TOF signal, etc. of the first sensor 311 and the second sensor 321 in a time sequence, and the processing circuit 350 compares the signal size of the eighth TOF signal with the seventh TOF signal (for example, compare the size of the two signals of the first sensor 311 and the size of the two signals of the second sensor 321, and then compare the size of the larger signal of the first sensor 311 and the second sensor 321, or compare the sizes of the four signals, but the present case is not limited to this). If the seventh TOF signal is greater than the eighth TOF signal, the ninth TOF signal is compared with the seventh TOF signal, and so on. If after a period of time, the ninth TOF signal currently obtained is the maximum value, the processing circuit 350 sets the ninth TOF frequency as the use frequency.

It is worth mentioning that the fourth measurement mode is designed to use all frequencies measured by the time difference method and the frequencies measured by the Doppler method to evaluate the measured values at the same time. Compared with the first measurement mode, the fourth measurement mode is suitable for the current properties of the liquid that cannot be directly evaluated and are suitable for time difference measurement or Doppler measurement. Based on this, this case can be adjusted to the most suitable measurement method in real time and dynamically.

In another embodiment, if the processing circuit 350 determines that all TOF measurement values and PWD measurement values do not meet the first threshold condition (indicating that the fourth measurement mode is not suitable for measuring the current liquid), it is necessary to execute other measurement modes in the verification stage (step S430).

In step S430, the flow meter 300 determines whether there is a measurement value that satisfies the first threshold condition.

In one embodiment, if the flow meter 300 determines that any one of the TOF measurement value and the PWD measurement value is greater than a preset threshold value, it is determined that there is a measurement value that satisfies the first threshold condition.

In one embodiment, if the flow meter 300 determines that all TOF measurement values and/or PWD measurement values are not greater than a preset threshold value, it is determined that there is no measurement value that meets the first threshold condition and returns to step S410 to select other measurement modes for verification.

If the flow meter 300 determines that there is a measurement value that meets the first threshold condition, step S440 is executed. Please refer to the above description and will not be repeated here.

In step S440, the flow meter 300 sets one of the TOF measurement and the PWD measurement as an operation mode according to the second threshold condition and sets a usage frequency. Please refer to the above description and will not repeat it here.

In one embodiment, the second threshold condition includes the maximum TOF measurement value at the same frequency, the maximum average value among the TOF measurement values at the same frequency, the minimum standard deviation among the TOF measurement values at the same frequency, the maximum PWD measurement value at the same frequency, the maximum average value among the PWD measurement values at the same frequency, and the minimum standard deviation among the PWD measurement values at the same frequency, etc.

In step S450, the flow meter 300 performs the measurement phase according to the set operation mode and usage frequency.

In the operation mode, the flow meter 300 controls the first sensor 311 and the second sensor 321 to emit a TOF signal having a TOF frequency of the use frequency and a PWD signal having a PWD frequency, and performs at least one of the corresponding TOF measurement and PWD measurement to measure the flow rate of the liquid in the measurement phase.

In step S460, the flow meter 300 determines whether the measured value calculated in the measurement phase meets the first threshold condition. If the flow meter 300 determines that the measured value does not meet the first threshold condition, it means that the properties of the liquid may change, and the current operating mode or usage frequency is no longer suitable for the liquid after the property change. At this time, the flow meter 300 automatically switches from the measurement phase to the verification phase to reselect a suitable measurement mode based on the above steps. If the flow meter 300 determines that the measured value meets the first threshold condition, the current operating mode and usage frequency are continuously used to measure the flow rate of the liquid. Please refer to the above description and will not be repeated here.

Please refer to Figure 9, which is a graph showing the relationship between the flow rate of the liquid and the density of impurities in the liquid according to an embodiment of the present invention. In one embodiment, the liquid flows in the pipe 110 at a stable flow rate. If the flow rate calculated by the flow meter 300 is the maximum value, then this maximum value is the correct flow rate.

In one embodiment, the flow meter 300 uses TOF measurement to calculate the flow rate of the liquid. When the density of impurities in the liquid is higher, the flow rate obtained by TOF measurement will be smaller (i.e., the measured flow rate will be less accurate), as shown by curve L1.

In one embodiment, the flow meter 300 uses PWD measurement to calculate the flow rate of the liquid. When the density of impurities in the liquid is higher, the flow rate obtained by PWD measurement will be greater (in line with the current flow rate, that is, the measured flow rate is more accurate), as shown by curve L2.

In TOF measurement, when the impurity density is equal to or greater than 0 and less than the first threshold value BD-L1, the accuracy of TOF measurement will reach a certain level of confidence, that is, the flow meter 300 can accurately measure the flow rate of the liquid using TOF measurement. When the impurity density is greater than or equal to the first threshold value BD-L1, the accuracy of TOF measurement will decrease as the impurity density increases.

In PWD measurement, when the impurity density is equal to or greater than 0 and less than the second threshold value BD-L2, the accuracy of PWD measurement will increase as the impurity density increases. When the impurity density is equal to or greater than the second threshold value BD-L2, the accuracy of PWD measurement will reach a certain level of confidence, that is, the flow meter 300 can accurately measure the flow rate of the liquid using PWD measurement.

Among them, the second threshold value BD-L2 is greater than the first threshold value BD-L1.

When the impurity density is equal to or greater than the first threshold value BD-L1 and less than the second threshold value BD-L2, that is, the impurity density falls in the dead band 915, the accuracy of the flow meter 300 using TOF measurement or PWD measurement will be lower than the confidence level, but the accuracy obtained by using the two methods is still different.

In one embodiment, the processing circuit 350 determines the sensitivity of switching from TOF measurement to PWD measurement or from PWD measurement to TOF measurement based on the width of the dead zone 915. The dead zone 915 is an interval that is equal to or greater than the first threshold value BD-L1 and less than the second threshold value BD-L2.

In one embodiment, during the verification phase of the flow meter 300, if the processing circuit 350 uses TOF measurement as the measurement method of the measurement mode and calculates that the maximum TOF measurement value is greater than the first threshold value BD-L1, the current measurement mode is switched to another measurement mode. For example, if the current measurement mode is the first measurement mode, the processing circuit 350 performs verification of the second measurement mode.

In another embodiment, during the verification phase of the flow meter 300, if the processing circuit 350 uses PWD measurement as the measurement method of the measurement mode and calculates that the maximum PWD measurement value is less than the second threshold value BD-L2, the current measurement mode is switched to another measurement mode. For example, if the current measurement mode is the fourth measurement mode, the processing circuit 350 performs verification of the first measurement mode.

In one embodiment, the order in which the processing circuit 350 re-executes verification may be the order of the first measurement mode, the second measurement mode, the third measurement mode, and the fourth measurement mode, but the present invention is not limited thereto.

In summary, the hybrid ultrasonic flowmeter and measurement method proposed in this case can dynamically switch between time difference measurement and Doppler measurement, and use different signal emission patterns to select the most suitable measurement for the current liquid properties, ensuring that accurate flow rate and flow rate can be measured at any time.

The above is only a specific example of this case, and does not limit the scope of the patent application of this case. Therefore, all equivalent changes made by applying the content of this case are also included in the scope of this case and should be stated.

S410~S460: Steps

Claims (12)

A hybrid ultrasonic flow meter, suitable for measuring the flow rate of a liquid, comprises: a first sensor and a second sensor, configured to send a signal of a time difference method (TOF) frequency and receive a TOF signal in a TOF measurement and to send a signal of a PWD frequency and receive a PWD signal in a PWD measurement; a switch, coupled to the first sensor and the second sensor, configured to switch the first sensor and the second sensor between the TOF measurement and the PWD measurement; and a processing circuit, coupled to the switch, configured to: when operating in a verification phase, utilize the arrangement of the TOF signal of multiple different TOF frequencies and the PWD signal of multiple different PWD frequencies The processing circuit is configured to combine a plurality of measurement modes, and execute at least one of the measurement modes through the first sensor and the second sensor to determine an operation mode and a usage frequency corresponding to the TOF signal or the PWD signal from the measurement modes; and in the operation mode, the first sensor and the second sensor are controlled to emit one of the TOF signal with the TOF frequency and the PWD signal with the PWD frequency, and execute at least one of the corresponding TOF measurement and the PWD measurement to measure the flow rate of the liquid in a measurement phase; wherein the processing circuit is configured to perform the following actions when executing a first measurement mode of the measurement modes: the first sensor and the second sensor are controlled to emit the TOF signal with the TOF frequency and the PWD signal with the PWD frequency having the usage frequency; A first TOF frequency and a second TOF frequency are used in the measurement; the first sensor and the second sensor are caused to sequentially and repeatedly send out the first TOF frequency signal and the second TOF frequency signal simultaneously based on a first transmission time interval, wherein the first TOF frequency is a maximum frequency used by the first sensor and the second sensor and the second TOF frequency is a minimum frequency used by the first sensor and the second sensor; a plurality of first TOF signals are received through the first sensor and the second sensor respectively, wherein the first TOF signals received by the first sensor are signals sent by the second sensor based on the first TOF frequency and the first TOF signals received by the second sensor are signals received by the second sensor based on the first TOF frequency. A signal emitted by a TOF frequency; a first TOF measurement value is calculated based on the first TOF signals; a plurality of second TOF signals are received through the first sensor and the second sensor respectively, wherein the second TOF signals received by the first sensor are emitted by the second sensor and the second TOF signals received by the second sensor are emitted by the second sensor; a second TOF measurement value is calculated based on the second TOF signals; and if at least one of the first TOF measurement value and the second TOF measurement value meets a first threshold condition, the first measurement mode is set as the operation mode and the frequency corresponding to the maximum value of the first TOF measurement value and the second TOF measurement value is set as the use frequency of the operation mode. A hybrid ultrasonic flow meter as described in claim 1, wherein the processing circuit is configured to perform the following actions when it is determined that both the first TOF measurement value and the second TOF measurement value do not meet the first threshold condition: causing the first sensor or the second sensor to use a first PWD frequency in the PWD measurement; causing the first sensor to emit a signal of the first PWD frequency based on a second emission time interval, and then causing the first sensor and the second sensor to sequentially and simultaneously emit the first TOF frequency signal and the second TOF frequency signal based on the first emission time interval, and repeatedly performing the above steps, wherein the second emission time interval is different from the first emission time interval. Transmitting time interval; Receive a first PWD signal through the first sensor or the second sensor, wherein the first PWD signal is a reflected signal of the signal of the first PWD frequency; calculate a first PWD measurement value according to the signal of the first PWD frequency and the frequency shift of the first PWD signal; and if at least one of the first TOF measurement value, the second TOF measurement value and the first PWD measurement value meets the first threshold condition, set the first measurement mode as the operating mode and set the frequency corresponding to the maximum value among the first TOF measurement value, the second TOF measurement value and the first PWD measurement value as the use frequency of the operating mode. A hybrid ultrasonic flow meter as described in claim 1, wherein the processing circuit is configured to perform the following actions when executing a second measurement mode of the measurement modes: causing the first sensor and the second sensor to use a third TOF frequency in the TOF measurement and causing the first sensor to use a second PWD frequency in the PWD measurement; causing the first sensor and the second sensor to simultaneously emit a signal of the third TOF frequency based on a first emission time interval, and causing the first sensor or the second sensor to emit a signal of the second PWD frequency based on a second emission time interval, and repeatedly performing the above operations; receiving a second PWD signal through the first sensor or the second sensor, wherein the second PWD signal is a reflected signal of the signal of the second PWD frequency; and transmitting the second PWD signal through the first sensor and the second sensor respectively. and the second sensor receives a plurality of third TOF signals, wherein the third TOF signals received by the first sensor are signals emitted by the second sensor based on the third TOF frequency and the third TOF signals received by the second sensor are signals emitted by the first sensor based on the third TOF frequency; a second PWD measurement value is calculated according to the signal of the second PWD frequency and the frequency shift of the second PWD signal and a third TOF measurement value is calculated based on the third TOF signals; and If at least one of the second PWD measurement value and the third TOF measurement value meets a first threshold condition, the second measurement mode is set as the operation mode and the frequency corresponding to the maximum value of the second PWD measurement value and the third TOF measurement value is set as the use frequency of the operation mode. A hybrid ultrasonic flow meter as described in claim 1, wherein the processing circuit is configured to perform the following actions when executing a third measurement mode of the measurement modes: causing the first sensor and the second sensor to use a fourth TOF frequency, a fifth TOF frequency, and a sixth TOF frequency in the TOF measurement; causing the first sensor and the second sensor to simultaneously and sequentially emit a signal of the fourth TOF frequency, simultaneously emit a signal of the fifth TOF frequency, and simultaneously emit a signal of the sixth TOF frequency based on a first emission time interval. and repeatedly executing the fourth TOF frequency, the fifth TOF frequency and the sixth TOF frequency, wherein the fourth TOF frequency, the fifth TOF frequency and the sixth TOF frequency are different from each other; receiving a plurality of fourth TOF signals, a plurality of fifth TOF signals and a plurality of sixth TOF signals through the first sensor and the second sensor respectively, wherein the fourth TOF signals received by the first sensor are signals emitted by the second sensor based on the fourth TOF frequency and the fourth TOF signals received by the second sensor are signals emitted by the first sensor based on the fourth TOF frequency, the The fifth TOF signals received by the first sensor are signals emitted by the second sensor based on the fifth TOF frequency, and the sixth TOF signals received by the first sensor are signals emitted by the second sensor based on the sixth TOF frequency, and the sixth TOF signals received by the second sensor are signals emitted by the first sensor based on the sixth TOF frequency; based on the fourth TOF signals The method further comprises: calculating a fourth TOF measurement value based on the fourth TOF measurement value, calculating a fifth TOF measurement value based on the fifth TOF signals, and calculating a sixth TOF measurement value based on the sixth TOF signals; and if at least one of the fourth TOF measurement value, the fifth TOF measurement value, and the sixth TOF measurement value meets a first threshold condition, setting the third measurement mode as the operation mode and setting the frequency corresponding to the maximum value among the fourth TOF measurement value, the fifth TOF measurement value, and the sixth TOF measurement value as the usage frequency of the operation mode. A hybrid ultrasonic flow meter as described in claim 1, wherein the processing circuit is configured to perform the following actions when executing a fourth measurement mode of the measurement modes: causing the first sensor and the second sensor to use a seventh TOF frequency, an eighth TOF frequency, and a ninth TOF frequency in the TOF measurement and causing the first sensor or the second sensor to use a third PWD frequency in the PWD measurement; causing the first sensor and the second sensor to respectively simultaneously and sequentially emit a signal of the seventh TOF frequency, simultaneously emit a signal of the eighth TOF frequency, and simultaneously emit a signal of the ninth TOF frequency based on a first emission time interval, and causing the first sensor or the second sensor to respectively and sequentially emit a signal of the seventh TOF frequency, simultaneously emit a signal of the eighth TOF frequency, and simultaneously emit a signal of the ninth TOF frequency based on a first emission time interval. The method comprises: transmitting a signal of the third PWD frequency at a second transmission time interval, and repeatedly performing the above steps, wherein the seventh TOF frequency, the eighth TOF frequency, the ninth TOF frequency and the third PWD frequency are different from each other and the second transmission time interval is different from the first transmission time interval; receiving a plurality of seventh TOF signals, a plurality of eighth TOF signals and a plurality of ninth TOF signals through the first sensor and the second sensor respectively, wherein the seventh TOF signals received by the first sensor are signals transmitted by the second sensor based on the seventh TOF frequency and the seventh TOF signals received by the second sensor are signals transmitted by the first sensor based on the seventh TOF frequency, and the first sensor The eighth TOF signals received by the second sensor are signals emitted by the second sensor based on the eighth TOF frequency, and the eighth TOF signals received by the second sensor are signals emitted by the first sensor based on the eighth TOF frequency, and the ninth TOF signals received by the first sensor are signals emitted by the second sensor based on the ninth TOF frequency, and the ninth TOF signals received by the second sensor are signals emitted by the first sensor based on the ninth TOF frequency; a seventh TOF measurement value is calculated based on the seventh TOF signals, an eighth TOF measurement value is calculated based on the eighth TOF signals, and a ninth TOF measurement value is calculated based on the ninth TOF signals. value; receive a third PWD signal through the first sensor or the second sensor, wherein the third PWD signal is a reflected signal of the signal of the third PWD frequency; calculate a third PWD measurement value according to the signal of the third PWD frequency and the frequency shift of the third PWD signal; and if at least one of the seventh TOF measurement value, the eighth TOF measurement value, the ninth TOF measurement value and the third PWD measurement value meets a first threshold condition, set the fourth measurement mode as the operation mode and set the frequency corresponding to the maximum value among the seventh TOF measurement value, the eighth TOF measurement value, the ninth TOF measurement value and the third PWD measurement value as the use frequency of the operation mode. The hybrid ultrasonic flowmeter as described in claim 1, wherein the processing circuit is configured to switch from the measurement phase to the verification phase to reselect the verification phase if a measured value of the operation mode is determined to not meet the first threshold condition during the measurement phase. A measurement method for measuring liquid flow rate using an ultrasonic flow meter, wherein the ultrasonic flow meter includes a first sensor, a second sensor and a processing circuit, wherein the first sensor and the second sensor send a signal with a TOF frequency and receive a TOF signal in a time difference method (TOF) measurement and send a signal with a PWD frequency and receive a PWD signal in a Doppler method (PWD) measurement, including: when the ultrasonic flow meter operates in a verification phase, the TOF signals with multiple different TOF frequencies and the PWD signals with multiple different PWD frequencies are arranged and combined into multiple measurement modes, and at least one of the measurement modes is executed , to determine an operation mode and a usage frequency corresponding to the TOF signal or the PWD signal from the measurement modes; and to control the first sensor and the second sensor to emit one of the TOF signal with the TOF frequency and the PWD signal with the PWD frequency in the operation mode of a measurement phase by the processing circuit, and to perform at least one of the corresponding TOF measurement and the PWD measurement to measure the flow rate of the liquid; The step of executing a first measurement mode of the measurement modes includes: using a first TOF frequency and a second TOF frequency in the TOF measurement; allowing the first sensor and the second sensor to measure the flow rate of the liquid based on A first transmission time interval is sequentially and repeatedly simultaneously transmitting a signal of the first TOF frequency and a signal of the second TOF frequency, wherein the first TOF frequency is a maximum frequency used by the first sensor and the second sensor and the second TOF frequency is a minimum frequency used by the first sensor and the second sensor; a plurality of first TOF signals are received through the first sensor and the second sensor respectively, wherein the first TOF signals received by the first sensor are signals emitted by the second sensor based on the first TOF frequency and the first TOF signals received by the second sensor are signals emitted by the second sensor based on the first TOF frequency; based on the first TOF signals A TOF signal is used to calculate a first TOF measurement value; a plurality of second TOF signals are received through the first sensor and the second sensor respectively, wherein the second TOF signals received by the first sensor are emitted by the second sensor and the second TOF signals received by the second sensor are emitted by the second sensor; a second TOF measurement value is calculated based on the second TOF signals; and if at least one of the first TOF measurement value and the second TOF measurement value meets a first threshold condition, the first measurement mode is set as the operation mode and the frequency of the maximum value of the first TOF measurement value and the second TOF measurement value is set as the use frequency of the operation mode. The measurement method as claimed in claim 7, wherein when the first measurement mode is executed, the step of the first TOF measurement value and the second TOF measurement value both failing to meet the first threshold condition comprises: using a first PWD frequency in the PWD measurement; causing the first sensor or the second sensor to emit a signal of the first PWD frequency based on a second transmission time interval, and then causing the first sensor and the second sensor to sequentially and simultaneously emit a signal of the first TOF frequency and a signal of the second TOF frequency based on the first transmission time interval, and repeatedly executing the above steps, wherein the second transmission time interval is different from the first transmission time interval; A first PWD signal is received through the first sensor or the second sensor, wherein the first PWD signal is a reflection signal of the signal of the first PWD frequency; a first PWD measurement value is calculated according to the signal of the first PWD frequency and the frequency shift of the first PWD signal; and if at least one of the first TOF measurement value, the second TOF measurement value and the first PWD measurement value meets the first threshold condition, the first measurement mode is set as the operation mode and the frequency corresponding to the maximum value among the first TOF measurement value, the second TOF measurement value and the first PWD measurement value is set as the use frequency of the operation mode. The measurement method as described in claim 7, wherein the step of executing a second measurement mode of the measurement modes includes: using a third TOF frequency in the TOF measurement and allowing the first sensor to use a second PWD frequency in the PWD measurement; allowing the first sensor and the second sensor to simultaneously emit a signal of the third TOF frequency based on a first emission time interval, and allowing the first sensor or the second sensor to emit a signal of the second PWD frequency based on a second emission time interval, and repeatedly executing the above steps; receiving a second PWD signal through the first sensor or the second sensor, wherein the second PWD signal is a reflection signal of the signal of the second PWD frequency; receiving a plurality of third TOF signals through the first sensor and the second sensor respectively. signal, wherein the third TOF signals received by the first sensor are signals emitted by the second sensor based on the third TOF frequency and the third TOF signals received by the second sensor are signals emitted by the first sensor based on the third TOF frequency; Calculate a second PWD measurement value according to the signal of the second PWD frequency and the frequency shift of the second PWD signal and calculate a third TOF measurement value based on the third TOF signals; and if at least one of the second PWD measurement value and the third TOF measurement value meets a first threshold condition, set the second measurement mode as the operation mode and set the frequency corresponding to the maximum value of the second PWD measurement value and the third TOF measurement value as the use frequency of the operation mode. The measurement method as described in claim 7, wherein the step of executing a third measurement mode of the measurement modes includes: allowing the first sensor and the second sensor to use a fourth TOF frequency, a fifth TOF frequency, and a sixth TOF frequency in the TOF measurement; allowing the first sensor and the second sensor to simultaneously and sequentially emit a signal of the fourth TOF frequency, simultaneously emit a signal of the fifth TOF frequency, and simultaneously emit a signal of the sixth TOF frequency based on a first emission time interval, and repeatedly execute the above steps. The fourth TOF frequency, the fifth TOF frequency and the sixth TOF frequency are different from each other; a plurality of fourth TOF signals, a plurality of fifth TOF signals and a plurality of sixth TOF signals are received through the first sensor and the second sensor respectively, wherein the fourth TOF signals received by the first sensor are signals emitted by the second sensor based on the fourth TOF frequency and the fourth TOF signals received by the second sensor are signals emitted by the first sensor based on the fourth TOF frequency, and the fourth TOF signals received by the first sensor are signals emitted by the second sensor based on the fourth TOF frequency. The fifth TOF signals are signals emitted by the second sensor based on the fifth TOF frequency, and the fifth TOF signals received by the second sensor are signals emitted by the first sensor based on the fifth TOF frequency, and the sixth TOF signals received by the first sensor are signals emitted by the second sensor based on the sixth TOF frequency, and the sixth TOF signals received by the second sensor are signals emitted by the first sensor based on the sixth TOF frequency; a calculation is performed based on the fourth TOF signals. a fourth TOF measurement value, a fifth TOF measurement value calculated based on the fifth TOF signals, and a sixth TOF measurement value calculated based on the sixth TOF signals; and If at least one of the fourth TOF measurement value, the fifth TOF measurement value, and the sixth TOF measurement value meets a first threshold condition, the third measurement mode is set as the operation mode and the frequency corresponding to the maximum value among the fourth TOF measurement value, the fifth TOF measurement value, and the sixth TOF measurement value is set as the usage frequency of the operation mode. The measurement method as described in claim 7, wherein the step of executing a fourth measurement mode of the measurement modes includes: allowing the first sensor and the second sensor to use a seventh TOF frequency, an eighth TOF frequency and a ninth TOF frequency in the TOF measurement and allowing the first sensor or the second sensor to use a third PWD frequency in the PWD measurement; allowing the first sensor and the second sensor to simultaneously and sequentially emit a signal of the seventh TOF frequency, a signal of the eighth TOF frequency and a signal of the ninth TOF frequency based on a first emission time interval, and allowing the first sensor or the second sensor to emit the signal of the eighth TOF frequency based on a second emission time interval. The method comprises: receiving a plurality of seventh TOF signals, a plurality of eighth TOF signals and a plurality of ninth TOF signals through the first sensor and the second sensor respectively, wherein the seventh TOF signals received by the first sensor are signals emitted by the second sensor based on the seventh TOF frequency, and the seventh TOF signals received by the second sensor are signals emitted by the first sensor based on the seventh TOF frequency, and the eighth TOF signals received by the second sensor are signals emitted by the first sensor based on the seventh TOF frequency, and the eighth TOF signals received by the first sensor are signals emitted by the second sensor based on the seventh TOF frequency. The TOF signal is a signal emitted by the second sensor based on the eighth TOF frequency, and the eighth TOF signals received by the second sensor are signals emitted by the first sensor based on the eighth TOF frequency, and the ninth TOF signals received by the first sensor are signals emitted by the second sensor based on the ninth TOF frequency, and the ninth TOF signals received by the second sensor are signals emitted by the first sensor based on the ninth TOF frequency; Calculate a seventh TOF measurement value based on the seventh TOF signals, calculate an eighth TOF measurement value based on the eighth TOF signals, and calculate a ninth TOF measurement value based on the ninth TOF signals; Receive a third PWD signal through the first sensor or the second sensor, wherein the third PWD signal is a reflection signal of the signal of the third PWD frequency; calculate a third PWD measurement value according to the signal of the third PWD frequency and the frequency shift of the third PWD signal; and if at least one of the seventh TOF measurement value, the eighth TOF measurement value, the ninth TOF measurement value and the third PWD measurement value meets a first threshold condition, set the fourth measurement mode as the operation mode and set the frequency corresponding to the maximum value among the seventh TOF measurement value, the eighth TOF measurement value, the ninth TOF measurement value and the third PWD measurement value as the use frequency of the operation mode. The measurement method as described in claim 7 further includes: if it is determined in the measurement phase that a measurement value of the operation mode does not meet the first threshold condition, switching from the measurement phase to the verification phase to reselect the verification phase.

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