Differential driving method of ultrasonic transducer

Abstract

The invention provides a differential driving method of an ultrasonic transducer, which relates to the technical field of ultrasonic transducers, and comprises the following steps: S1, circuit connection: connecting circuit elements, arranging six control pins on a control chip, and respectively connecting each control pin to a corresponding position in a circuit; and the UT2 is used as a receiving end for transmitting and receiving ultrasonic waves. According to the differential driving method of the ultrasonic transducer, negative pulses are given through fire1n and fire2n, differential driving is carried out on the transducer, the amplitude of received electric signals is increased, and stronger electric signals can be received under the conditions that the working voltage is low and signal attenuation in media is large, so that the differential driving method is suitable for flow velocity measurement of more media, and the application range is wide. The added differential drive does not cause the voltage at the two ends of the transducer to change suddenly, and in application, the two ends of the transducer are grounded during dormancy, so that the transducer does not pressurize for a long time, and the service life of the system is prevented from being shortened due to the newly added function.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic transducers, and in particular to a differential driving method for ultrasonic transducers. Background Art

[0002] With the rapid development of the Internet of Things, sensors as core components of environmental perception are becoming more and more important. Among them, ultrasonic sensing has the advantages of low cost and relatively easy application. It is widely used in short-distance ranging and flow rate measurement of gas and fluid. Ultrasonic sensing requires the use of ultrasonic transducers. When working, the transducer at the transmitting end converts electrical signals into mechanical vibrations, thereby promoting the vibration of the medium (gas or fluid), and then generating ultrasonic waves. The transducer at the receiving end waits for the echo of the ultrasonic wave, and the mechanical vibration generated by the echo is converted back into an electrical signal. As long as the sound speed of the medium is known, the propagation distance can be simply obtained through the obtained TOF time. Furthermore, if you want to measure the flow rate of gas or fluid, two transducers are required to send and receive to each other to obtain the two-way TOF time between the two transducers. The time difference between these two time periods will be proportional to the flow rate of the gas or liquid in the pipeline.

[0003] Figure 2 The figure shows the distance measurement implementation structure of the prior art solution. The negative ends of the two transducers are grounded, UT1 is used as the transmitting end, and UT2 is used as the receiving end. The positive pulse whose transmitting frequency is the resonant frequency of the transducer is connected to the positive end of UT1 after passing through R1. The receiving end resistor R2 serves as the load of UT2. After receiving the echo, the cone-shaped sinusoidal electrical signal is coupled to stop2 through C2 and transmitted back to the chip for processing. By timing the time from fire1 sending the wave to stop2 receiving the echo, the TOF time can be obtained, and then calculated with the sound speed in the medium to obtain the distance from UT1 to UT2. Figure 3 The structure of the flow velocity measurement implementation of the prior art solution is shown. The transmission and reception of the transducer are interchangeable. In the flow velocity measurement system, the distance between UT1 and UT2 is fixed, and the sound speed of the medium is fixed. Therefore, the TOF time from UT1 to UT2 and the TOF time from UT2 to UT1 are only related to the flow velocity of the medium. After two TOF time measurements of mutual transmission and reception, the time difference obtained can be converted to obtain the medium flow velocity.

[0004] In the flow velocity measurement of some media, due to the large attenuation of the medium, the received echo-converted electrical signal is difficult to be recognized by the system, which limits the application of the system in the flow velocity measurement of some media with large attenuation. The purpose of the present invention is to increase the driving amplitude of the transmitting transducer through simple modifications, thereby increasing the vibration amplitude of the transducer and doubling the amplitude of the received echo-converted electrical signal, thereby being suitable for flow velocity measurement of more media. Summary of the invention

[0005] The purpose of the invention provided by the present invention is to differentially drive the transducer by giving negative pulses through fire1_n and fire2_n, thereby increasing the amplitude of the received electrical signal. When the working voltage is low and the signal attenuation in the medium is large, a stronger electrical signal can be received, thereby being suitable for flow velocity measurement of more media. The increased differential drive will not cause a rapid mutation in the voltage across the transducer. In application, the two ends of the transducer are grounded during sleep, so that the transducer will not be pressurized for a long time, thereby avoiding a decrease in the service life of the system due to the addition of new functions.

[0006] In order to achieve the above-mentioned effect, the present invention provides the following technical solution: a differential driving method of an ultrasonic transducer, comprising the following steps:

[0007] Step 1: Circuit connection: connect circuit components, set six control pins on the control chip, and connect each control pin to the corresponding position in the circuit.

[0008] Step 2: Use UT1 as the transmitter and UT2 as the receiver to transmit and receive ultrasonic waves.

[0009] Step 3: Use ultrasonic sensors UT1 and UT2 to measure the flow rate of the medium.

[0010] Step 4: Derive the impedance-matched load resistor and the transfer function of the signal from the transmitting pin to the receiving pin.

[0011] Furthermore, in the step 2, the circuit elements include two ultrasonic transducers UT1 and UT2, two resistors R1 and R2, and two capacitors C1 and C2.

[0012] Furthermore, in step 2, the control pins are stop1, fire1, fire1_n, stop2, fire2 and fire2_n respectively.

[0013] Furthermore, in the step 2, when UT1 is used as the transmitting end and UT2 is used as the receiving end, the Stop1 pin is in a high impedance state, so the capacitor C1 can be ignored, and the fire1 and fire1_n pins respectively give positive pulses and negative pulses with a frequency equal to the resonant frequency of the transducer, and the fire2 and fire2_n pins on the receiving end are grounded. At this time, if the impedance of the transducer UT2 and the resistor R2 is matched, after the transducer receives the echo with a frequency equal to the resonant frequency, it generates an electrical signal of a conical sine wave, which is coupled to stop2 through the capacitor C2 and is thus received by the chip.

[0014] Furthermore, in the step 2, fire1 is connected to the upper plate of the transducer after passing through the resistor R1, and fire1_n is directly connected to the lower plate of the transducer.

[0015] Furthermore, in step three, the step of measuring the flow rate of the medium is:

[0016] S301: In the dormant state, the four pins fire1, fire1_n, fire2, and fire2_n are all grounded to ensure that the voltage across the transducer is 0;

[0017] S302: When UT1 transmits and UT2 receives, fire1_n is set to 1 first. After all modules of the system are ready, fire1 and fire1_n transmit positive pulses and negative pulses with the resonant frequency of the transducer respectively. At the same time, the system starts timing, waits for stop2 to receive the echo, stops timing, and records the TOF time.

[0018] S303: After the first TOF time measurement is completed, fire1_n is set to 0, and a period of time is waited to allow the ultrasonic wave in the medium to fully decay, so as to avoid incorrect measurement in the next measurement;

[0019] S304: The second TOF time measurement, let UT2 transmit, when UT1 receives, fire2_n is set to 1 first, and when all modules of the system are ready, fire2 and fire2_n transmit positive pulses and negative pulses with the frequency of the transducer resonance frequency respectively, and the system starts timing at the same time, and stops timing after stop1 receives the echo, and records the TOF time;

[0020] S305: After completing two TOF time measurements, fire2_n is set to 0, and the system returns to sleep mode;

[0021] S306: Calculate the medium flow rate.

[0022] Furthermore, in step S306, the medium flow rate can be simply converted by using the time difference between the two tested TOF times, the known distance between UT1 and UT2, and the known sound velocity in the medium.

[0023] Furthermore, in the step 4, deduction is performed based on the equivalent circuit during ranging and the equivalent circuit during transducer resonance.

[0024] The present invention provides a differential driving method for an ultrasonic transducer, which has the following beneficial effects: by giving negative pulses through fire1_n and fire2_n, the transducer is differentially driven, the amplitude of the received electrical signal is increased, and a stronger electrical signal can be received when the working voltage is low and the signal attenuation in the medium is large, so that it is suitable for flow velocity measurement of more media, and the increased differential driving will not cause a rapid mutation of the voltage at both ends of the transducer. In application, both ends of the transducer are grounded during sleep, so that the transducer will not be pressurized for a long time, thereby avoiding a decrease in the service life of the system due to the addition of new functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of a differential driving method for an ultrasonic transducer according to the present invention;

[0026] Figure 2 A distance measurement structure diagram of a prior art solution of a differential driving method of an ultrasonic transducer of the present invention;

[0027] Figure 3 A flow velocity measurement structure diagram of a prior art solution of a differential driving method of an ultrasonic transducer of the present invention;

[0028] Figure 4 A structural diagram of a differential driving method for an ultrasonic transducer according to the present invention;

[0029] Figure 5 A distance measurement structure diagram of a differential driving method of an ultrasonic transducer of the present invention;

[0030] Figure 6 A working waveform diagram of a differential driving method for an ultrasonic transducer of the present invention;

[0031] Figure 7 An equivalent circuit diagram of a differential driving method of an ultrasonic transducer during distance measurement according to the present invention;

[0032] Figure 8 The present invention is an equivalent circuit diagram of a differential driving method for an ultrasonic transducer when the transducer is in resonance. DETAILED DESCRIPTION

[0033] See also Figure 1-8 The present invention provides a technical solution: a differential driving method of an ultrasonic transducer, comprising the following steps:

[0034] Step 1: Circuit connection: connect circuit components, set six control pins on the control chip, and connect each control pin to the corresponding position in the circuit.

[0035] Step 2: Use UT1 as the transmitter and UT2 as the receiver to transmit and receive ultrasonic waves.

[0036] Step 3: Use ultrasonic sensors UT1 and UT2 to measure the flow rate of the medium.

[0037] Step 4: Derive the impedance-matched load resistor and the transfer function of the signal from the transmitting pin to the receiving pin.

[0038] Specifically, in step 2, the circuit elements include two ultrasonic transducers UT1 and UT2, two resistors R1 and R2, and two capacitors C1 and C2. The two ultrasonic transducers are used to transmit or receive ultrasonic waves. In a speed measurement process, UT1 is required to be used as the transmitting end and UT2 is required to be used as the receiving end to perform a TOF time measurement. Then the state is switched, UT2 is used as the transmitting end, and UT1 is used as the receiving end to perform a TOF time measurement. Since the distance is fixed and the sound speed in the medium is the same, the TOF time difference is only proportional to the flow rate of the medium. The two resistors R1 and R2 mainly match the impedance of the transducer at the resonant frequency, so that the system can achieve the optimal energy transfer efficiency, thereby generating a larger swing when receiving. At the same time, at the transmitting end, the resistor plays a filtering role, so that the voltage at the positive and negative ends of the transducer will not have too fast mutations, which helps to avoid the rapid decline of the service life of the transducer. The two capacitors are used to couple the electrical signal generated by the transducer to stop1 or stop2 and transmit it back to the inside of the chip. At the transmitting end, the other end of the capacitor, stop1 or stop2, is in a high impedance state, so the capacitor does not affect the behavior of the transmitting end.

[0039] Specifically, in step 2, the control pins are stop1, fire1, fire1_n, stop2, fire2 and fire2_n.

[0040] Specifically, in step 2, when UT1 is used as the transmitter and UT2 is used as the receiver, the Stop1 pin is in high impedance state, so the capacitor C1 can be ignored, and the fire1 and fire1_n pins respectively give positive pulses and negative pulses with a frequency equal to the resonant frequency of the transducer, and the fire2 and fire2_n pins on the receiving end are grounded. At this time, if the impedance of the transducer UT2 and the resistor R2 are matched, after the transducer receives the echo with a frequency equal to the resonant frequency, it generates an electrical signal of a conical sine wave, which is coupled to stop2 through capacitor C2 and is received by the chip. By adding the fire1_n and fire2_n pins, the anti-phase pulses given to fire1 and fire2 when transmitting the wave increase the vibration amplitude of the transducer, thereby enhancing the electrical signal generated by the echo, and the signal received by stop1 or stop2 is increased. The amplitude of the electrical signal is doubled. When the working voltage is low and the signal attenuation in the medium is large, a stronger electrical signal can be received, which is suitable for flow velocity measurement of more media. The Fire1 and fire2 pins are connected to the positive end of the transducer through a resistor. The resistor and the internal capacitor of the transducer will form a filter. Even if the fire1_n and fire2_n pins are added to give negative pulses, the filter still exists, and the voltage across the ultrasonic transducer will not change rapidly. This can avoid the reduction of the service life caused by the rapid mutation of the voltage across the transducer. It is more suitable for application scenarios that require ultra-long working time. In the dormant stage, the four pins of fire1, fire1_n, fire2, and fire2_n are grounded to ensure that the voltage across the transducer is 0 most of the time, avoiding the reduction of the service life caused by long-term pressure.

[0041] Specifically, in step 2, fire1 is connected to the upper plate of the transducer after passing through resistor R1, and fire1_n is directly connected to the lower plate of the transducer.

[0042] Specifically, in step 3, the steps for measuring the flow rate of the medium are:

[0043] S301: In the dormant state, the four pins fire1, fire1_n, fire2, and fire2_n are all grounded to ensure that the voltage across the transducer is 0;

[0044] S302: When UT1 transmits and UT2 receives, fire1_n is set to 1 first. After all modules of the system are ready, fire1 and fire1_n transmit positive pulses and negative pulses with the resonant frequency of the transducer respectively. At the same time, the system starts timing, waits for stop2 to receive the echo, stops timing, and records the TOF time.

[0045] S303: After the first TOF time measurement is completed, fire1_n is set to 0, and a period of time is waited to allow the ultrasonic wave in the medium to fully decay, so as to avoid incorrect measurement in the next measurement;

[0046] S304: The second TOF time measurement, let UT2 transmit, when UT1 receives, fire2_n is set to 1 first, and when all modules of the system are ready, fire2 and fire2_n transmit positive pulses and negative pulses with the frequency of the transducer resonance frequency respectively, and the system starts timing at the same time, and stops timing after stop1 receives the echo, and records the TOF time;

[0047] S305: After completing two TOF time measurements, fire2_n is set to 0, and the system returns to sleep mode;

[0048] S306: Calculate the medium flow rate.

[0049] Specifically, in step S306, the medium flow rate can be simply converted by using the time difference between the two tested TOF times, the known distance between UT1 and UT2, and the known sound velocity in the medium.

[0050] Specifically, in step 4, deduction is performed based on the equivalent circuit during ranging and the equivalent circuit during transducer resonance.

[0051] The derivation process of the impedance matching load resistor is:

[0052] like Figure 7 As shown, the transducer UT1 can be equivalent to a static capacitor C e0 and a series path, which is connected in parallel by resistor R e1 , capacitor C e1 and inductor L e1 Similarly, the transducer UT2 can be equivalent to a static capacitor C e3 and a series path, which is connected in parallel by resistor R e2 , capacitor C e2 and inductor L e2 Composition, in the application, the transducers UT1 and UT2 are of the same model, so the resistance, capacitance and inductance values ​​of the equivalent model are equal.

[0053]

[0054] When the input frequency satisfies the above formula, it is equal to the resonant frequency f z When the inductance and capacitance of the transducer series path are connected, they will cancel each other out.

[0055] like Figure 8 As shown, when the transducer resonates, the impedance Z of the transducer UT1 is the resistance R e1 and capacitor C e0 The parallel connection is shown in the formula.

[0056]

[0057] After derivation, the impedance Z UT1 It is transformed into the form of R+jX, as shown in the following formula, where the real part represents resistance and the imaginary part represents reactance.

[0058]

[0059] Since this solution uses resistors for impedance matching, the imaginary part is ignored and the load resistance should be equal to the impedance Z UT1 The real part of is shown in the following formula.

[0060]

[0061] Next, V fire1 To V stop2 The transfer function is derived as:

[0062]

[0063] V fire1 Converted into electrical power P on the transducer UT1 t As shown in the formula above.

[0064] P t =P s T s

[0065] The above formula shows that the transmitted electric power P s Converted into emitted sound power P t , where T s is the acoustic-to-electric conversion efficiency at the transmitting end.

[0066] P r =P t L=P t e -αd

[0067] Where P r is the acoustic power at the receiving end, L is the attenuation coefficient of the medium, α is the attenuation constant of the medium, and d is the distance from the transmitting end to the receiving end.

[0068] P e =P r T r

[0069] Received sound power P r Converted into received electrical power P e , where T r is the acoustic-to-electric conversion efficiency at the receiving end.

[0070]

[0071] The open-loop voltage of the transducer is shown in the above formula

[0072]

[0073] When the value of C2 is large enough and the stop2 pin has high impedance, it can be considered that V stop2 Equal to the voltage drop across the load resistor R2, and then according to the voltage division formula, V stop2 .

[0074] Combining the above formula, we can get

[0075]

[0076] When R1=R2、Z UT1 =Z UT2 When , it can be simplified to

[0077]

[0078] According to the above formula, since T s 、T r , α, and Z UT1 They are all determined by physical properties. fire1 Under the condition of no change, the closer R1 is to Z UT1 , V stop2 The stronger the signal, the greater the difference between R1 and Z. UT1 The real part of the impedance can be matched to achieve the highest transmission efficiency.

[0079] At the same time, according to the above formula, it can be seen that through differential drive, V fire1 The signal is doubled, which can bring V stop2 Doubling of the signal.

[0080] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A differential driving method for an ultrasonic transducer, characterized in that: The following steps are involved: S1. Circuit connection: connect circuit components, set six control pins on the control chip, and connect each control pin to the corresponding position in the circuit; S2, use UT1 as the transmitter and UT2 as the receiver to transmit and receive ultrasonic waves; S3, using ultrasonic sensors UT1 and UT2 to measure the flow rate of the medium; S4. Derive the impedance-matched load resistor and the transfer function of the signal from the transmitting pin to the receiving pin.

2. The differential driving method of an ultrasonic transducer according to claim 1, characterized in that: In the step S2, the circuit elements include two ultrasonic transducers UT1, UT2, two resistors R1, R2 and two capacitors C1, C2.

3. The differential driving method of an ultrasonic transducer according to claim 2, characterized in that: In step S2, the control pins are stop1, fire1, fire1_n, stop2, fire2 and fire2_n respectively.

4. The differential driving method of an ultrasonic transducer according to claim 3, characterized in that: In step S2, when UT1 is used as a transmitter and UT2 is used as a receiver, the Stop1 pin is in a high impedance state, so the capacitor C1 can be ignored, the fire1 and fire1_n pins respectively give positive pulses and negative pulses with a frequency equal to the resonant frequency of the transducer, and the fire2 and fire2_n pins on the receiving end are grounded. At this time, if the impedance of the transducer UT2 and the resistor R2 is matched, after the transducer receives the echo with a frequency equal to the resonant frequency, it generates an electrical signal of a conical sine wave, which is coupled to stop2 through the capacitor C2 and is thus received by the chip.

5. The differential driving method of an ultrasonic transducer according to claim 4, characterized in that: In the step S2, fire1 is connected to the upper plate of the transducer after passing through the resistor R1, and fire1_n is directly connected to the lower plate of the transducer.

6. The differential driving method of an ultrasonic transducer according to claim 5, characterized in that: In step S3, the step of measuring the flow rate of the medium is: S301: In the dormant state, the four pins fire1, fire1_n, fire2, and fire2_n are all grounded to ensure that the voltage across the transducer is 0; S302: When UT1 transmits and UT2 receives, fire1_n is set to 1 first. After all modules of the system are ready, fire1 and fire1_n transmit positive pulses and negative pulses with the resonant frequency of the transducer respectively. At the same time, the system starts timing, waits for stop2 to receive the echo, stops timing, and records the TOF time. S303: After the first TOF time measurement is completed, fire1_n is set to 0, and a period of time is waited to allow the ultrasonic wave in the medium to fully decay, so as to avoid incorrect measurement in the next measurement; S304: The second TOF time measurement, let UT2 transmit, when UT1 receives, fire2_n is set to 1 first, and when all modules of the system are ready, fire2 and fire2_n transmit positive pulses and negative pulses with the frequency of the transducer resonance frequency respectively, and the system starts timing at the same time, and stops timing after stop1 receives the echo, and records the TOF time; S305: After completing two TOF time measurements, fire2_n is set to 0, and the system returns to sleep mode; S306: Calculate the medium flow rate.

7. The differential driving method of an ultrasonic transducer according to claim 6, characterized in that: In step S306, the medium flow rate can be simply converted by using the time difference between the two tested TOF times, the known distance between UT1 and UT2, and the known sound velocity in the medium.

8. The differential driving method of an ultrasonic transducer according to claim 7, characterized in that: In the step S4, deduction is performed based on the equivalent circuit during distance measurement and the equivalent circuit during transducer resonance.

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