Flow anomaly detection method and circuit for a phase difference type ultrasonic flowmeter

Abstract

The present invention discloses a flow detection method for a phase difference type ultrasonic flowmeter, comprising: obtaining a received signal; comparing the phase difference between the obtained received signal and a reference signal; and judging whether the flow velocity of the ultrasonic wave is abnormal according to the comparison result. In the present invention, an abnormal flow velocity detection circuit is provided to detect the abnormal flow velocity. The real-time detection of the ultrasonic flow velocity is carried out. By detection, the phase difference between the reference signal and the received signal is compared and detected to realize the real-time monitoring of the abnormal flow velocity, and timely feedback is carried out through a control circuit, thus avoiding the problem that the flow velocity of the gas changes greatly during the measurement process.

Description

Technical Field

[0001] The present invention relates to an ultrasonic flowmeter device, and particularly to a method and circuit for detecting abnormal flow of a phase difference type ultrasonic flowmeter. Background Art

[0002] At present, the mainstream ultrasonic flowmeters on the market mostly measure by utilizing the influence of fluid (liquid, air) on the ultrasonic propagation speed. By respectively measuring the ultrasonic propagation time in the downstream and upstream directions once, the time difference Δt between the two measurements is obtained, and then according to the sound velocity c, the distance L between the ultrasonic transducers, and the included angle θ between the ultrasonic transducers and the pipeline, the flow velocity of the fluid in the pipeline can be calculated as:

[0003]

[0004] The flow velocity can be directly obtained by measuring the time difference Δt, or can be measured by converting the time difference into a phase difference. For example, in a phase difference type ultrasonic flowmeter metering device described in the patent application No. 201020580382.7, the flowmeter calculates Δt and the fluid velocity by comparing the phase difference between the signals received by the ultrasonic transducers and a reference signal, and through an F / V conversion circuit and an analog-to-digital converter.

[0005] However, there is a problem with the above-mentioned phase difference type ultrasonic flowmeter, that is, the signal needs to be stable during the phase difference detection process. Once the flow velocity of the gas changes greatly during the measurement, the obtained measurement result will be incorrect and needs to be excluded and re-measured.

[0006] Based on the above existing technical problems, the present invention provides a technical solution to solve the above technical problems. Summary of the Invention

[0007] The object of the present invention is to provide a method and circuit for detecting abnormal flow of a phase difference type ultrasonic flowmeter, which realizes the detection of abnormal flow velocity by setting up a flow velocity abnormal detection circuit, and makes a timely feedback through a control circuit, avoiding the occurrence of obtaining incorrect information.

[0008] The technical solution provided by the present invention is as follows:

[0009] A method for detecting abnormal flow of a phase difference type ultrasonic flowmeter, including: acquiring a received signal; comparing the phase difference between the acquired received signal and a reference signal; and judging whether the flow velocity of the ultrasonic wave is abnormal according to the comparison result.

[0010] Further preferably, it includes: counting the number of rising edges or falling edges of the received signal and comparing it with the number of rising edges of the reference signal within a set time period, and comparing the counted number of rising edges of the received signal and the reference signal; when the number of rising edges of the received signal is not equal to the number of rising edges of the corresponding reference signal, it is determined that the received signal is abnormal.

[0011] Further preferably, it includes: counting the number of falling edges of the received signal and the reference signal within a set time period; comparing the number of falling edges of the received signal with the number of falling edges of the corresponding reference signal; when the number of falling edges of the received signal is not equal to the number of falling edges of the corresponding reference signal, it is determined that the received signal is abnormal.

[0012] Further preferably, it includes: obtaining the duration of the rising edge between two adjacent pulses in the received signal and the reference signal respectively within a set time period; comparing the obtained durations of the rising edge between two adjacent pulses in the received signal and the reference signal; when the durations of the rising edge between two adjacent pulses in the received signal and the reference signal are not equal, it is determined that the received signal is abnormal.

[0013] Further preferably, it includes: obtaining the duration of the falling edge between two adjacent pulses in the received signal and the reference signal respectively within a set time period; comparing the obtained durations of the falling edge between two adjacent pulses in the received signal and the reference signal; when the durations of the falling edge between two adjacent pulses in the received signal and the reference signal are not equal, it is determined that the received signal is abnormal.

[0014] A flow anomaly detection circuit for a phase difference type ultrasonic flowmeter, which can execute the flow anomaly detection method of the above-mentioned phase difference type ultrasonic flowmeter, further includes: a first transducer for transmitting ultrasonic signals, a second transducer for receiving ultrasonic signals, a signal processing circuit, a phase difference detection circuit, a flow velocity anomaly detection circuit, and a control circuit; the first transducer transmits ultrasonic signals to the second transducer; the second transducer transmits the received ultrasonic signals to the signal processing circuit; after the signal processing circuit processes the received ultrasonic signals, it compares them with a reference signal through the phase difference detection circuit, and the comparison result is simultaneously sent to the control circuit and the flow velocity anomaly detection circuit; the flow velocity anomaly detection circuit calculates the phase difference, and the control circuit further determines whether the flow velocity of the ultrasonic wave is abnormal according to the comparison result.

[0015] Further preferably, the flow rate anomaly detection circuit includes: a first counter U10 and a second counter U11; the 1CK terminal of the first pin of the first counter U10 is communicatively connected to the signal processing circuit; the 1QA terminal of the third pin of the first counter U10 is communicatively connected to the 1CK terminal of the first pin of the second counter U11; the 2QA terminal of the eleventh pin of the first counter U10 is communicatively connected to the 1CLK terminal of the second pin and the 2CLR terminal of the twelfth pin of the second counter U11 respectively; the 2CK terminal of the thirteenth pin of the first counter U10 is communicatively connected to the phase difference detection circuit and the control circuit; the 1QA terminal of the third pin of the second counter U11, the 1QB terminal of the fourth pin of the second counter U11, the 2QB terminal of the tenth pin of the second counter U11, and the 2QA terminal of the eleventh pin of the second counter U11 are all communicatively connected to the input end of the control circuit correspondingly.

[0016] Further preferably, the signal processing circuit includes: a first operational amplifier U6 and a second operational amplifier U7; the first inverting input terminal of the first operational amplifier U6 is communicatively connected to the signal switching circuit; the first output terminal of the first operational amplifier U6 is communicatively connected to the second output terminal of the first operational amplifier U6, the second inverting input terminal of the first operational amplifier U6, and the PV terminal of the third pin of the second operational amplifier U7 through an RC circuit composed of a capacitor C7 and a resistor R8; the Q terminal of the first pin of the second operational amplifier U7 is communicatively connected to the input end of the phase difference detection circuit.

[0017] Further preferably, the phase difference detection circuit includes: a frequency discriminator and phase detector U8 and a third operational amplifier U9; the signal input terminal of the fifth pin of the frequency discriminator and phase detector U8 is communicatively connected to the signal processing circuit; the signal output terminal of the tenth pin of the frequency discriminator and phase detector U8 is communicatively connected to the non-inverting input terminal of the third pin of the third operational amplifier U9 through a current limiting resistor R11; the signal output terminal of the sixth pin of the third operational amplifier U9 is communicatively connected to the control circuit and the flow rate anomaly detection circuit respectively.

[0018] Further preferably, it further includes a signal switching circuit: the signal switching circuit is communicatively connected to the first transducer and the second transducer respectively; 4 switch chips are provided in the signal switching circuit, which are: switch chip U1, switch chip U2, switch chip U3, and switch chip U4; the first switch terminals (S) of the switch chip U1 and the switch chip U2 are communicatively connected and grounded through a capacitor C1; the first switch terminals (S) of the switch chip U3 and the switch chip U4 are communicatively connected and grounded through a capacitor C2; the second switch terminals (D) of the switch chip U1 and the switch chip U3 are communicatively connected and communicatively connected to the transmission driving circuit; the second switch terminals (D) of the switch chip U2 and the switch chip U4 are communicatively connected and communicatively connected to the signal processing circuit.

[0019] A flow anomaly detection method and circuit for a phase-difference type ultrasonic flowmeter provided by the present invention at least bring the following beneficial effects:

[0020] In the present invention, an abnormal flow velocity detection circuit is provided to detect abnormal flow velocities. Specifically, the real-time detection of the ultrasonic flow velocity is carried out, and by comparing and detecting the phase difference between the reference signal and the received signal, the real-time monitoring of abnormal flow velocities is realized, and timely feedback is carried out through the control circuit, avoiding the problem of incorrect detection information when the flow velocity of the gas changes greatly during the measurement process.

[0021] In the present invention, by setting the abnormal flow velocity detection circuit to detect the stable state of the signal in real time during the phase difference detection process, once the flow velocity of the gas changes greatly during the measurement process, the problem of being excluded and re-measured is avoided, thus causing the problem of low work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above characteristics, technical features, advantages and their implementation manners of a flow anomaly detection method for a phase-difference type ultrasonic flowmeter will be further described below in a clear and understandable manner in combination with the drawings of the preferred embodiments.

[0023] Figure 1 is a structural diagram of an embodiment of a flow anomaly detection method for a phase-difference type ultrasonic flowmeter of the present invention;

[0024] Figure 2 is a circuit diagram of another embodiment of a flow anomaly detection method for a phase-difference type ultrasonic flowmeter of the present invention;

[0025] Figure 3 is a circuit diagram of another embodiment of a flow anomaly detection method for a phase-difference type ultrasonic flowmeter of the present invention;

[0026] Figure 4 is a circuit diagram of another embodiment of a flow anomaly detection method for a phase-difference type ultrasonic flowmeter of the present invention;

[0027] Figure 5 is a circuit diagram of another embodiment of a flow anomaly detection method for a phase-difference type ultrasonic flowmeter of the present invention;

[0028] Figure 6 is a circuit diagram of another embodiment of a flow anomaly detection method for a phase-difference type ultrasonic flowmeter of the present invention;

[0029] Figure 7 is a circuit diagram of another embodiment of a flow anomaly detection method for a phase-difference type ultrasonic flowmeter of the present invention;

[0030] Figure 8 It is a circuit diagram of another embodiment of the flow anomaly detection method of a phase difference type ultrasonic flowmeter according to the present invention. Detailed implementation manners

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will describe the specific implementation manners of the present invention with reference to the accompanying drawings. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings, and other implementation manners can also be obtained.

[0032] For the sake of simplicity of the drawings, only the parts related to the present invention are schematically shown in each figure, and they do not represent their actual structures as products.

[0033] The present invention provides a flow detection method for a phase difference type ultrasonic flowmeter, as shown in Figure 1 the following; including: step S100 of acquiring a received signal; step S200 of comparing the phase difference between the acquired received signal and a reference signal; step S300 of judging whether the flow velocity of the ultrasonic wave is abnormal according to the comparison result.

[0034] Specifically, in this embodiment, it is mainly used to realize the flow velocity detection of the ultrasonic flowmeter, to judge whether the flow velocity is stable, and to accurately judge the occurrence of anomalies in a timely manner; the specific detection process is as follows: transducer 1 sends a signal, transducer 2 receives the signal, the control circuit drives transducer 1 with a periodic signal and sends ultrasonic waves, after a set periodic time, the ultrasonic waves reach transducer 2, and transducer 2 starts to receive the signal, which is the received signal; then a certain stable waveform is intercepted from the received signal, detected, the phase difference between the reference signal and the received signal is compared and detected, and at the same time the flow velocity anomaly detection circuit detects the received signal to judge whether the flow is stable during the phase difference detection process.

[0035] In the present invention, the detection of abnormal flow velocity is realized by setting a flow velocity anomaly detection circuit. Specifically, the real-time detection of the ultrasonic flow velocity is carried out, the phase difference between the reference signal and the received signal is compared and detected, the real-time monitoring of abnormal flow velocity is realized, and timely feedback is carried out through the control circuit, avoiding the problem that the flow velocity of the gas changes greatly during the measurement process.

[0036] The present invention also provides an embodiment for the detection of abnormal flow velocity, as shown in Figure 2As shown in the figure; it includes: counting the number of rising edges or falling edges of the received signal within a set time period corresponding to the number of rising edges of the reference signal, and comparing them; when the number of rising edges of the received signal is not equal to the number of rising edges of the corresponding reference signal, it is determined that the received signal is abnormal.

[0037] Preferably, it includes: counting the number of falling edges of the received signal and the reference signal within a set time period; comparing the number of falling edges of the received signal with the number of falling edges of the corresponding reference signal; when the number of falling edges of the received signal is not equal to the number of falling edges of the corresponding reference signal, it is determined that the received signal is abnormal.

[0038] Specifically, in this embodiment, the detection method is: through Figure 2 As shown in the figure; assume that the phase difference is detected in 5 cycles. Generally, after the received signal is stable, the phase difference measurement circuit detects the phase difference between the received signal and the reference signal. At the same time, the flow rate anomaly detection circuit starts to work, and counts the rising edges or falling edges of the reference signal and the received signal respectively. If the flow rate does not change during the measurement, at the end of the measurement, Figure 6 As shown in the figure; the values of counter 1 and counter 2 should be equal, and the number of rising edges collected is 5. If there is a sudden change in the flow rate during the measurement, such as caused by the opening or closing of a valve, the phase of the received signal will be disordered at this time, and it may be advanced or delayed, resulting in unequal values of counter 1 and 2 after the measurement. If this situation is detected, it can be determined that the measurement result is invalid this time, avoiding incorrect data from being included in the flow rate reading, and the control circuit issues a control command for re-detection.

[0039] The present invention also provides another embodiment for abnormal flow rate detection. Refer to Figure 3 As shown in the figure; it includes: obtaining the duration of the rising edges of two adjacent pulses in the received signal and the reference signal respectively within a set time period; comparing the duration of the rising edges of two adjacent pulses in the obtained received signal and the reference signal; when the duration of the rising edges of two adjacent pulses in the received signal and the reference signal is not equal, it is determined that the received signal is abnormal.

[0040] Preferably, it includes: obtaining the duration of the falling edges of two adjacent pulses in the received signal and the reference signal respectively within a set time period; comparing the duration of the falling edges of two adjacent pulses in the obtained received signal and the reference signal; when the duration of the falling edges of two adjacent pulses in the received signal and the reference signal is not equal, it is determined that the received signal is abnormal.

[0041] Specifically, in this embodiment, when the measurement accuracy requirement is relatively high, it may take hundreds of cycle times to perform phase difference detection. In this case, the situation shown in Figure 3 may occur, that is, the flow rate mutates several times during the measurement process, but the values of the two counters are equal after the measurement ends. To solve this problem, the circuit shown in Figure 4 can be adopted; this circuit consists of two 2-bit counters. Among them, the counter counts the rising edge or falling edge of the clk pin. The RST terminal is reset on the rising edge or falling edge, and D is the output. Figure 5 To specifically generate waveform changes, when the received signal increases at the rising edge during a flow rate mutation, counter 1 will be greater than 1. When the rising edge decreases, counter 2 will be greater than 1. Once the system detects that either counter is greater than 1, it means that the flow rate has mutated. It is equivalent to the time of the two rising edges or falling edges at the corresponding positions of each waveform being unequal. If they are unequal, an abnormality occurs.

[0042] The present invention also provides a flow rate abnormality detection circuit for a phase difference type ultrasonic flowmeter, which can execute the embodiments of the flow rate abnormality detection method of the phase difference type ultrasonic flowmeter, as shown in reference to Figure 7 ; it further includes: a first transducer 1 for transmitting ultrasonic signals, a second transducer 2 for receiving ultrasonic signals, a signal processing circuit 400, a phase difference detection circuit 600, a flow velocity abnormality detection circuit 500, and a control circuit 100; the first transducer 1 transmits ultrasonic signals to the second transducer; the second transducer 2 sends the received ultrasonic signals to the signal processing circuit; after the signal processing circuit processes the received ultrasonic signals, it is compared with a reference signal through the phase difference detection circuit, and the comparison result is sent to the control circuit and the flow velocity abnormality detection circuit at the same time; the flow velocity abnormality detection circuit calculates the phase difference, and the control circuit further determines whether the flow velocity of the ultrasonic wave is abnormal according to the comparison result.

[0043] Specifically, as shown in reference to Figure 7 ; the present invention further includes a transmission driving circuit 200, which is used to receive the driving command sent by the control circuit 100 to the signal switching circuit to control which one is set as the transmitting end and which one is the receiving end, so as to control the two transducers to send signals; the signal processing circuit is used to filter and amplify the received information and then input it to the phase difference detection circuit and the flow velocity abnormality detection circuit; the phase difference detection circuit is used to calculate the phase difference of the received signal and determine whether the flow velocity is stable according to the phase difference; at the same time, the abnormal flow velocity detection circuit intercepts whether the received signal within the set period is abnormal. If the signal within the set period is abnormal, it is discarded, and the control circuit will send a command to intercept again and perform judgment and measurement again.

[0044] In the present invention, by providing a flow rate anomaly detection circuit, it is possible to determine whether the received signal intercepted in a set period is normal. If it is normal, the phase difference under stable conditions can be calculated, and further the stable flow rate can be calculated, making the flow rate calculation more accurate and reliable.

[0045] The present invention also provides an embodiment, as shown in Figure 7-8 The flow rate anomaly detection circuit includes: a first counter U10 and a second counter U11; the models of U10 and U11 are: 74VHC393FT; the 1CK terminal of the 1st pin of the first counter U10 is communicatively connected to the signal processing circuit; the 1QA terminal of the 3rd pin of the first counter U10 is communicatively connected to the 1CK terminal of the 1st pin of the second counter U11; the 2QA terminal of the 11th pin of the first counter U10 is respectively communicatively connected to the 1CLK terminal of the 2nd pin and the 2CLR terminal of the 12th pin of the second counter U11; the 2CK terminal of the 13th pin of the first counter U10 is communicatively connected to the phase difference detection circuit and the control circuit; the 1QA terminal of the 3rd pin, the 1QB terminal of the 4th pin, the 2QB terminal of the 10th pin, and the 2QA terminal of the 11th pin of the second counter U11 are respectively communicatively connected to the input end of the control circuit.

[0046] Specifically, the two counters in U10 respectively divide the received signal generated by the 1st pin of U7 and the reference signal provided by the CPU by two, and the generated signals are SIG and REF respectively. Then, as shown in Figure 6 The signals are respectively connected to the counting CK terminals and the reset CLR terminals of the two counters in U11. The CPU determines whether a flow rate mutation occurs during the phase difference measurement according to the output of U11.

[0047] The present invention also provides an embodiment, as shown in Figure 7-8 The signal processing circuit includes: a first operational amplifier U6, model: AD8652; a second operational amplifier U7, model: ADCMP600; the first inverting input terminal of the first operational amplifier U6 is communicatively connected to the signal switching circuit; the first output terminal of the first operational amplifier U6 is communicatively connected to the second output terminal of the first operational amplifier U6, the second inverting input terminal of the first operational amplifier U6, and the PV terminal of the 3rd pin of the second operational amplifier U7 through an RC circuit composed of a capacitor C7 and a resistor R8; the Q terminal of the 1st pin of the second operational amplifier U7 is communicatively connected to the input end of the phase difference detection circuit.

[0048] Specifically, the first operational amplifier U6 is used to filter the received signal. After the processing is completed, it is further amplified by the second operational amplifier U7, and the amplified recognizable signal is sent to the phase difference detection circuit; the Q terminal of the 1st pin of the second operational amplifier U7 is connected to the VOCIN terminal of the drip pin of the frequency discriminator and phase detector U8 in the phase difference detection circuit; thus, the processing of the received signal is realized.

[0049] In the present invention, after the signal processing circuit filters and amplifies the received signal, the received signal becomes more reliable and recognizable.

[0050] Preferably, the phase difference detection circuit includes: a frequency discriminator and phase detector U8, and a third operational amplifier U9; the signal input terminal of the 5th pin of the frequency discriminator and phase detector U8 is communicatively connected to the signal processing circuit; the signal output terminal of the 10th pin of the frequency discriminator and phase detector U8 is communicatively connected to the non-inverting input terminal of the 3rd pin of the third operational amplifier U9 through a current-limiting resistor R11; the signal output terminal of the 6th pin of the third operational amplifier U9 is communicatively connected to the control circuit and the flow rate anomaly detection circuit respectively.

[0051] Specifically, the frequency discriminator and phase detector U8 is used to identify and calculate the phase difference between the received signal and the reference signal. After being processed by the low-pass filter composed of R11, R12 and C8, this phase difference will generate a corresponding DC level. The third operational amplifier U9 is used to buffer and drive this level and send it to the control circuit, and the control circuit calculates the flow rate according to the value of this DC level;

[0052] The present invention also provides an embodiment, refer to Figure 7-8 as shown; preferably, it further includes a signal switching circuit: the signal switching circuit is communicatively connected to the first transducer and the second transducer respectively; 4 switch chips are provided in the signal switching circuit, which are: switch chip U1, switch chip U2, switch chip U3, switch chip U4; the first switch terminals (S) of switch chip U1 and switch chip U2 are communicatively connected and grounded through a capacitor C1; the first switch terminals (S) of switch chip U3 and switch chip U4 are communicatively connected and grounded through a capacitor C2; the second switch terminals (D) of switch chip U1 and switch chip U3 are communicatively connected and connected to the transmission driving circuit; the second switch terminals (D) of switch chip U2 and switch chip U4 are communicatively connected and connected to the signal processing circuit.

[0053] Specifically, 4 single-pole switches are provided in this embodiment to control the transducers. The IN terminals of the 4th pins provided in switch chip U1, switch chip U2, switch chip U3 and switch chip U4 are connected to the control circuit 100 to realize the switching of the two transducers. Therefore, the present invention can realize the flexible switching of the transducers in the corresponding flowmeter and realize various control methods.

[0054] In the present invention, a control chip is provided in the control circuit, which can be of the ARM series, 51 series, PIC series, etc.; at the same time, each component in each circuit diagram can be replaced under the condition of meeting the performance parameters.

[0055] It should be noted that the above embodiments can be freely combined as needed. The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for detecting abnormal flow of a phase difference type ultrasonic flowmeter, characterized in that, Including: Obtain the received signal; Compare the phase difference between the obtained received signal and the reference signal; Judge whether the flow rate of the ultrasonic wave is abnormal according to the comparison result; Including: When the number of rising edges of the received signal is equal to the number of rising edges of the corresponding reference signal, obtain the duration of the rising edges of two adjacent pulses in the received signal and the reference signal respectively within a set time period; Compare the duration of the rising edges of two adjacent pulses in the obtained received signal and the reference signal; When the duration of the rising edges of two adjacent pulses in the received signal and the reference signal is not equal, it is judged that the received signal is abnormal; When the rising edge increases during the flow rate mutation of the received signal, counter 1 will be greater than 1. When the rising edge decreases, counter 2 will be greater than 1. When it is detected that any one of the counters is greater than 1, it indicates that the flow rate has mutated; Transducer 1 sends a signal, and transducer 2 receives the signal. The control circuit drives transducer 1 with a periodic signal to send ultrasonic waves. After a set period of time, the ultrasonic waves reach transducer 2, and transducer 2 starts to receive the signal, which is the received signal. Then, intercept a certain stable waveform from the received signal, detect it, compare and detect the phase difference between the reference signal and the received signal. At the same time, the flow rate anomaly detection circuit detects the received signal to judge whether the flow rate is stable during the phase difference detection process.

2. The flow anomaly detection method of the phase difference type ultrasonic flowmeter according to claim 1, characterized in that Including: Count the number of rising edges of the received signal and the reference signal within a set time period corresponding to the number of rising edges of the rising edge or falling edge of the received signal; Conduct a comparison; When the number of rising edges of the received signal is not equal to the number of rising edges of the corresponding reference signal, it is judged that the received signal is abnormal.

3. The flow anomaly detection method of the phase difference type ultrasonic flowmeter according to claim 1, wherein, Including: Count the number of falling edges of the received signal and the reference signal within a set time period; Compare the number of falling edges of the received signal with the number of falling edges of the reference signal correspondingly; When the number of falling edges of the received signal is not equal to the number of falling edges of the corresponding reference signal, it is judged that the received signal is abnormal.

4. The flow anomaly detection method of the phase difference type ultrasonic flowmeter according to claim 1, wherein Including: Obtain the duration of the falling edges of two adjacent pulses in the received signal and the reference signal respectively within a set time period; Compare the duration of the falling edges of two adjacent pulses in the obtained received signal and the reference signal; When the duration of the falling edges of two adjacent pulses in the received signal and the reference signal is not equal, it is judged that the received signal is abnormal.

5. A flow anomaly detection circuit for a phase difference type ultrasonic flowmeter, characterized in that, The flow rate anomaly detection method of the phase difference type ultrasonic flowmeter according to claim 1-4 can be executed. It is characterized in that it further includes: a first transducer for sending ultrasonic signals, a second transducer for receiving ultrasonic signals, a signal processing circuit, a phase difference detection circuit, a flow rate anomaly detection circuit, and a control circuit; The first transducer sends ultrasonic signals to the second transducer; The second transducer sends the received ultrasonic signal to the signal processing circuit; After the signal processing circuit processes the received ultrasonic signal, it is compared with the reference signal through the phase difference detection circuit. The comparison result is sent to the control circuit and the flow rate anomaly detection circuit simultaneously; The flow rate anomaly detection circuit includes: a first counter U10 and a second counter U11; The 1CK terminal of the first pin of the first counter U10 is communicatively connected to the signal processing circuit; The 1QA terminal of the third pin of the first counter U10 is communicatively connected to the 1CK terminal of the first pin of the second counter U11; The 2QA terminal of the eleventh pin of the first counter U10 is communicatively connected to the 1CLK terminal of the second pin and the 2CLR terminal of the twelfth pin of the second counter U11 respectively; The 2CK terminal of the thirteenth pin of the first counter U10 is communicatively connected to the phase difference detection circuit and the control circuit; The 1QA terminal of the third pin of the second counter U11, the 1QB terminal of the fourth pin of the second counter U11, the 2QB terminal of the tenth pin of the second counter U11, and the 2QA terminal of the eleventh pin of the second counter U11 are communicatively connected to the input end of the control circuit correspondingly; When the number of rising edges of the received signal is equal to the number of rising edges of the corresponding reference signal, the duration of the rising edges of two adjacent pulses in the received signal and the reference signal are obtained respectively within a set time period; Compare the duration of the rising edges of two adjacent pulses in the obtained received signal and reference signal; When the duration of the rising edges of two adjacent pulses in the received signal and the reference signal is not equal, it is determined that the received signal is abnormal; When the rising edge increases during a sudden change in flow rate of the received signal, counter 1 will be greater than 1. When the rising edge decreases, counter 2 will be greater than 1. When it is detected that any one of the counters is greater than 1, it indicates that the flow rate has changed suddenly.

6. The flow anomaly detection circuit of a phase difference type ultrasonic flowmeter according to claim 5, characterized in that The signal processing circuit includes: a first operational amplifier U6 and a second operational amplifier U7; The first inverting input terminal of the first operational amplifier U6 is communicatively connected to the signal switching circuit; The first output terminal of the first operational amplifier U6 is communicatively connected to the second output terminal of the first operational amplifier U6, the second inverting input terminal of the first operational amplifier U6, and the PV terminal of the third pin of the second operational amplifier U7 through an RC circuit composed of a capacitor C7 and a resistor R8; The Q terminal of the first pin of the second operational amplifier U7 is communicatively connected to the input end of the phase difference detection circuit.

7. The flow anomaly detection circuit of a phase difference type ultrasonic flowmeter according to claim 5, characterized in that The phase difference detection circuit includes: a frequency discriminator and phase detector U8 and a third operational amplifier U9; The signal input terminal of the fifth pin of the frequency discriminator and phase detector U8 is communicatively connected to the signal processing circuit; The signal output terminal of the tenth pin of the frequency discriminator and phase detector U8 is communicatively connected to the non-inverting input terminal of the third pin of the third operational amplifier U9 through a current limiting resistor R11; The signal output terminal of the sixth pin of the third operational amplifier U9 is communicatively connected to the control circuit and the flow rate anomaly detection circuit respectively; 8. The flow anomaly detection circuit of a phase difference type ultrasonic flowmeter according to claim 5, characterized in that, It further includes a signal switching circuit: The signal switching circuit is communicatively connected to the first transducer and the second transducer respectively; There are 4 switch chips in the signal switching circuit, namely: switch chip U1, switch chip U2, switch chip U3, and switch chip U4; The first switch terminals (S) of switch chip U1 and switch chip U2 are communicatively connected and grounded through capacitor C1; The first switch terminals (S) of switch chip U3 and switch chip U4 are communicatively connected and grounded through capacitor C2; The second switch terminals (D) of switch chip U1 and switch chip U3 are communicatively connected and communicatively connected to the transmission driving circuit; The second switch terminals (D) of switch chip U2 and switch chip U4 are communicatively connected and communicatively connected to the signal processing circuit.

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