CN214372691U

CN214372691U - Signal receiving and transmitting device of gas ultrasonic flowmeter

Info

Publication number: CN214372691U
Application number: CN202023080288.8U
Authority: CN
Inventors: 于江豪
Original assignee: Goldcard Smart Group Co Ltd
Current assignee: Goldcard Smart Group Co Ltd
Priority date: 2020-12-17
Filing date: 2020-12-17
Publication date: 2021-10-08
Anticipated expiration: 2030-12-17

Abstract

The utility model discloses a gaseous ultrasonic flowmeter signal transceiver, include: the low-voltage transmitting circuit comprises a plurality of matching resistors, generates excitation signals for different transducers and sends the excitation signals to the first analog switch; the first analog switch switches on the transducer according to a channel control signal sent by the microcontroller, and sends an excitation signal to the switched-on transducer or receives an electric signal from the transducer and sends the electric signal to the receiving circuit; the transducer generates ultrasonic waves according to the excitation signals or generates electric signals according to the received ultrasonic signals; the receiving circuit comprises a high-impedance amplifying sub-circuit which amplifies the received electric signal and then sends the amplified electric signal to the low-voltage transmitting circuit according to the gain control signal sent by the microcontroller. The low-voltage transmitting circuit has low power consumption and high safety; the matching resistor can reduce zero drift, thereby reducing errors and improving the measurement precision. The receiving circuit can adjust the amplification gain according to the received signals, adapts to the conditions of different calibers and flow rates, and is high in flexibility.

Description

Signal receiving and transmitting device of gas ultrasonic flowmeter

Technical Field

The utility model relates to a gaseous ultrasonic flowmeter field especially relates to a gaseous ultrasonic flowmeter signal transceiver.

Background

With the technological progress, the gas chemical engineering is rapidly developed, and the gas ultrasonic flowmeter has the advantages of no pressure loss, large range ratio, high measurement precision, insensitivity to vortex and the like, is widely applied to a plurality of fields of chemical industry, metallurgy, petroleum, natural gas trade and the like, is particularly suitable for large-caliber natural gas measurement, and plays an important role in aspects of west-east gas transportation, energy conservation and emission reduction.

The measurement principle of the ultrasonic flowmeter mainly comprises a time difference method, a phase difference method, a frequency difference method and a Doppler method. Among them, the time difference method is most applied and has the best effect. When the gas ultrasonic flowmeter based on the time difference method measures the flow, firstly, an excitation signal is needed to drive the transmitting transducer to send out an ultrasonic signal, then, the receiving transducer converts the received ultrasonic signal into an echo signal, and the system finds a stable characteristic point according to the echo signal to determine the forward and backward flow propagation time so as to calculate the gas flow. However, when the ultrasonic signal of the gas ultrasonic flowmeter propagates in the gas, the energy attenuation is serious, the amplitude of the obtained echo signal is small, the signal-to-noise ratio is low, the influence of noise, flow fluctuation and the like is easy, and the echo signal is distorted due to the increase of the gas flow velocity, so that the signal processing of the gas ultrasonic flowmeter is difficult.

In the traditional time difference method, in order to increase the amplitude of a received signal, an excitation voltage is increased to hundreds of volts by a transformer to excite a transmitting transducer to generate a stronger ultrasonic signal so as to increase the amplitude of the received signal, and an ultrasonic signal receiving circuit adopts a charge amplifier to amplify an echo signal of the receiving ultrasonic transducer. This method can improve the accuracy of ultrasonic flow measurement, but has high power consumption and low safety. In addition, in order to meet the explosion-proof requirement, a plurality of current-limiting and voltage-limiting elements need to be added, so that the power consumption is further increased, the service life of the battery is shortened, and the stability is reduced.

In view of the above, it is desirable to provide a signal transceiver for a gas ultrasonic flow meter, which is low in power consumption, high in measurement accuracy, safe and stable.

SUMMERY OF THE UTILITY MODEL

In order to reduce cost, improve reliability and output precision, the utility model provides a gaseous ultrasonic flowmeter signal transceiver, include: the system comprises a microcontroller, a low-voltage transmitting circuit, a receiving circuit, a first analog switch and a plurality of transducers;

the first analog switch is connected with the low-voltage transmitting circuit, the receiving circuit, the controller and the plurality of transducers;

the low-voltage transmitting circuit comprises a plurality of matched resistors; the low-voltage transmitting circuit is used for sequentially generating excitation signals for different transducers in a time-sharing manner and transmitting the excitation signals to the first analog switch;

the first analog switch is used for switching on a transducer according to a channel control signal sent by the microcontroller, sending the excitation signal to the switched-on transducer, or receiving an electric signal from the transducer and sending the electric signal to the receiving circuit;

a plurality of said transducers for generating ultrasonic waves from said excitation signal or generating electrical signals from received ultrasonic signals;

the receiving circuit comprises a high-impedance amplifying sub-circuit, and the receiving circuit is used for amplifying the received electric signal and then sending the amplified electric signal to the low-voltage transmitting circuit according to the gain control signal sent by the microcontroller.

Preferably, the receiving circuit further includes: a second analog switch and a low-pass filter sub-circuit;

the gating pin of the second analog switch is connected with the input/output pin of the first analog switch, the high-impedance amplification sub-circuit and the microcontroller;

the high-impedance amplifying sub-circuit is connected with the low-pass filtering sub-circuit and the microcontroller;

the low-pass filter sub-circuit is connected with the low-voltage transmitting circuit.

Preferably, the high impedance amplification sub-circuit comprises: the high-impedance amplifier, the third analog switch and a plurality of feedback resistors;

a positive phase input pin of the high-impedance amplifier is connected with the output end of the second analog switch, a negative phase input pin of the high-impedance amplifier is connected with the third analog switch, and the output end of the high-impedance amplifier is connected with the low-pass filter sub-circuit and the plurality of feedback resistors;

the number of the feedback resistors is the same as that of gating pins of the third analog switch, and each feedback resistor is connected with one gating pin;

and a control pin of the third analog switch is connected with the microcontroller.

Preferably, the low voltage transmitting circuit includes: the circuit comprises a low-voltage timing chip, a power supply filter sub-circuit, a first crystal oscillator sub-circuit, a second crystal oscillator circuit, a first matching resistor and a second matching resistor;

a first pulse generation pin of the low-voltage timing chip is connected with one input/output pin of the first analog switch through the first matching resistor, a second pulse generation pin is connected with the other input/output pin of the first analog switch through the second matching resistor, and a 1.8V output pin of the low-voltage timing chip is connected with a 1.8V input pin of the low-voltage timing chip through the power supply filter sub-circuit;

and the first crystal oscillator sub-circuit and the second crystal oscillator circuit are both connected with the low-voltage timing chip.

Preferably, the first crystal oscillator sub-circuit includes: a ceramic crystal oscillator and a first resistor.

Preferably, the second crystal oscillator circuit includes: the low-frequency crystal oscillator comprises a low-frequency crystal oscillator, a second resistor, a first capacitor and a second capacitor.

Preferably, the receiving circuit and the low voltage transmitting circuit each comprise a load switch;

the load switch of the low-voltage transmitting circuit is connected with the microcontroller and the second analog switch;

and a load switch of the low-voltage transmitting circuit is connected with the microcontroller and the low-voltage timing chip.

Preferably, the first analog switch is an 8-way analog switch.

Preferably, the second analog switch is a 2-way analog switch.

Preferably, the third analog switch is a 16-way analog switch.

The utility model has the advantages that: the low-voltage transmitting circuit can generate ultrasonic excitation signals with the amplitude of 15V and the frequency of 200kHz, and is low in power consumption and high in safety; the excitation voltage of the transducer can be increased, so that the transmitted ultrasonic signal is stronger; the matching resistor in the first transmitting circuit can reduce zero drift, thereby reducing errors and improving the measurement precision. The high-impedance amplification sub-circuit in the receiving circuit can adjust the amplification gain according to the received signal, so that the receiving circuit can adapt to the adjustment of the amplification gain of the received signal under the conditions of different calibers and flow rates, has strong flexibility, reduces high power consumption caused by single amplification gain, and prolongs the service life of a battery.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to denote like parts throughout the drawings.

In the drawings:

fig. 1 is a schematic diagram of a signal transceiver of a gas ultrasonic flowmeter according to the present invention;

fig. 2 is a schematic diagram of a low-voltage transmitting circuit of a signal transceiver of a gas ultrasonic flowmeter according to the present invention;

fig. 3 is a schematic diagram of a receiving circuit of a signal transceiver of a gas ultrasonic flowmeter according to the present invention;

fig. 4 is a schematic diagram of a load switch of a signal transceiver of a gas ultrasonic flowmeter according to the present invention;

fig. 5 is an equivalent model schematic diagram of a receiving circuit of a signal transceiver of a gas ultrasonic flowmeter according to the present invention;

fig. 6 is an equivalent model schematic diagram of a low-voltage transmitting circuit of another signal transceiver of a gas ultrasonic flow meter according to the present invention.

Description of the reference numerals

100 microcontroller 200 low voltage transmitting circuit

300 receiving circuit U1 first analog switch

First crystal oscillator subcircuit of S energy converter 201

202 second crystal oscillator circuit 203 low-voltage timing chip

204 power filter sub-circuit 301 high impedance amplifier sub-circuit

302 low pass filter sub-circuit U2 second analog switch

U3 third analog switch A1 high impedance amplifier

U4 load switch Y1 ceramic crystal oscillator

Y2 low frequency crystal oscillator Rm matching resistor

Rm1 first matching resistance Rm2 second matching resistance

S1 first transducer S2 second transducer

S3 third transducer S4 fourth transducer

S5 fifth transducer S6 sixth transducer

R1 first resistor R2 second resistor

R3 third resistor R4 fourth resistor

R5 fifth resistor R6 sixth resistor

R7 seventh resistance Rf feedback resistance

Rf1 first feedback resistance Rf2 second feedback resistance

Rf3 third feedback resistor Rf4 fourth feedback resistor

Rf5 fifth feedback resistor Rf6 sixth feedback resistor

Rf7 seventh feedback resistor Rf8 eighth feedback resistor

Rf9 ninth feedback resistor Rf10 tenth feedback resistor

Rf11 eleventh feedback resistor Rf12 twelfth feedback resistor

Rf13 thirteenth feedback resistor Rf14 fourteenth feedback resistor

Rf15 fifteenth feedback resistor Rf16 sixteenth feedback resistor

C1 first capacitance C2 second capacitance

C3 third capacitance C4 fourth capacitance

C5 fifth capacitance C6 sixth capacitance

C7 seventh capacitance C8 eighth capacitance

C9 ninth capacitance C10 tenth capacitance

C11 eleventh capacitor C12 twelfth capacitor

C13 thirteenth capacitor C14 fourteenth capacitor

C15 fifteenth capacitor C16 sixteenth capacitor

CG1 first parallel capacitance group CG2 second parallel capacitance group

CG3 third parallel capacitor group

Detailed Description

Exemplary embodiments of the present invention will be further described with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The utility model provides a gaseous ultrasonic flowmeter signal transceiver, as shown in figure 1, include: microcontroller 100, low voltage transmit circuit 200, receive circuit 300, first analog switch U1, and a plurality of transducers S.

The first analog switch U1 is connected to the low voltage transmit circuit 200, the receive circuit 300, the controller 100, and the plurality of transducers S. The low voltage transmitting circuit 200 includes a plurality of matching resistors. The low-voltage transmitting circuit 200 is used for sequentially generating excitation signals for different transducers S in a time-sharing manner, and transmitting the excitation signals to the first analog switch U1. The first analog switch U1 is used to turn on the transducer S according to the channel control signal sent by the microcontroller 100, send an excitation signal to the turned on transducer S, or receive an electrical signal from the transducer S to send to the receiving circuit 300. A plurality of transducers S for generating ultrasonic waves from the excitation signal or generating electrical signals from the received ultrasonic signals. The receiving circuit 300 includes a high impedance amplification sub-circuit 301. The receiving circuit 300 is configured to amplify the received electrical signal according to the gain control signal sent by the microcontroller 100 and send the amplified electrical signal to the low voltage transmitting circuit 200.

As shown in fig. 2, the receiving circuit 300 includes, in addition to the high-impedance amplifying sub-circuit 301: a second analog switch U2 and a low pass filter sub-circuit 302. The gating pin of the second analog switch U2 is connected to the input/output pin of the first analog switch U1, the high impedance amplifier sub-circuit 301 and the microcontroller 100, the high impedance amplifier sub-circuit 301 is connected to the low pass filter sub-circuit 302 and the microcontroller 100, and the low pass filter sub-circuit 302 is connected to the low voltage transmitting circuit 200.

As shown in fig. 2, the high impedance amplifier sub-circuit 301 includes: a high impedance amplifier a1, a third analog switch U3, and a plurality of feedback resistors Rf. The non-inverting input pin of the high impedance amplifier a1 is connected to the output terminal (COM pin) of the second analog switch U2, the inverting input pin is connected to the pin 6(D) of the third analog switch U3, and the output terminal is connected to the low pass filter sub-circuit 302 and the plurality of feedback resistors Rf. The number of the feedback resistors Rf is the same as the number of the gate pins of the third analog switch U3, and each feedback resistor Rf is connected to one gate pin. The control pin of the third analog switch U3 is connected to the microcontroller 100. The control pins of the third analog switch U3 include pin 10(A3), pin 11(a2), pin 14(a1), and pin 15(a 0). Pin 1(S16) of the third analog switch U3 is connected to the first feedback resistor Rf1, pin 2(S15) is connected to the second feedback resistor Rf2, pin 3(S14) is connected to the third feedback resistor Rf3, pin 4 (S3) is connected to the fourth feedback resistor Rf3, pin 5 (S3) is connected to the fifth feedback resistor Rf3, pin 6 (S3) is connected to the sixth feedback resistor Rf3, pin 7 (S3) is connected to the seventh feedback resistor Rf3, pin 8 (S3) is connected to the eighth feedback resistor Rf3, pin 17 (S3) is connected to the ninth feedback resistor Rf3, pin 18 (S3) is connected to the tenth feedback resistor Rf3, pin 19(S3) is connected to the eleventh feedback resistor Rf3, pin 20 (S3) is connected to the twelfth feedback resistor Rf3, pin 21 (S3) is connected to the thirteenth feedback resistor Rf3, pin 19(S3) is connected to the fourteenth feedback resistor Rf3, and pin fifteen (S3) is connected to the fourteenth feedback resistor Rf 3623, the pin 24(S8) is connected to the sixteenth feedback resistor Rf 16. The inverting input pin of the high impedance amplifier a1 is further connected to one end of a fourth resistor R4, the positive power supply pin (Vs +) is connected to a seventh capacitor C7, and the other end of the seventh capacitor C7, the other end of the fourth resistor R4 and the negative power supply pin (Vs-) of the high impedance amplifier a1 are all grounded to GND. The enable pin (EN) of the third analog switch U3, the power supply voltage pin (VDD), the positive power supply pin (Vs +) of the high impedance amplifier and the positive power supply pin (V +) of the second analog switch U2 are all applied with a circuit voltage VCC _ RX, one end of the eighth capacitor C8 and one end of the third capacitor C3 are both connected with the power supply voltage pin (VDD) of the third analog switch U3, the other end of the eighth capacitor C8 and the other end of the third capacitor C3 are both grounded GND, the positive power supply pin (V +) of the second analog switch U2 is also connected with one end of the fourth capacitor C4, and the other end of the fourth capacitor C4 is grounded.

The low-pass filtering sub-circuit 302 includes: a fifth resistor R5 and a fifth capacitor C5. One end of the fifth resistor R5 is connected to one end of the fifth capacitor C5, and the pin 8(RECEIVE _ UP) and the pin 10(RECEIVE _ DOWN) of the low-voltage timing chip 203, the other end of the fifth resistor R5 is connected to the output terminal of the high-impedance amplifier a1, and the other end of the fifth capacitor C5 is grounded to GND.

As shown in fig. 2, pin 1 of the second analog switch U2 is connected to the microcontroller 100, pin 3 is connected to ground, pin 4(NC) is connected to pin 8(DA) of the first analog switch U1, and pin 6(NO) is connected to pin 9(DB) of the first analog switch U1.

As shown in fig. 3, the low voltage transmitting circuit 200 includes: the low-voltage timing chip 203, the power filter sub-circuit 204, the first crystal oscillator sub-circuit 201, the second crystal oscillator circuit 202, the first matching resistor Rm1 and the second matching resistor Rm 2. A first pulse generation pin (FIRE _ UP) of the low-voltage timing chip 203 is connected with one input/output pin (DB) of the first analog switch U1 through a first matching resistor Rm1, a second pulse generation pin (FIRE _ DOWN) is connected with the other input/output pin (DA) of the first analog switch U1 through a second matching resistor Rm2, and a 1.8V output pin (VDD18_ OUT) of the low-voltage timing chip 203 is connected with a 1.8V input pin (VDD18_ IN) of the low-voltage timing chip through a power filter sub-circuit 204. The first crystal oscillator sub-circuit 201 and the second crystal oscillator circuit 202 are both connected to a low-voltage timer chip 203.

As shown in fig. 3, the power supply filtering sub-circuit 204 is configured to reduce a voltage ripple of the output voltage VCC, and the power supply filtering sub-circuit 204 includes: a third resistor R3 and a sixth capacitor C6. The 1.8V output pin (VDD18_ OUT) of the low voltage timing chip 203 is connected to one end of a third resistor R3, the other end of the third resistor R3 outputs a 1.8V voltage VCC, and the other end of the third resistor is further connected to one end of a sixth capacitor C6 and the 1.8V input pin (VDD18_ IN) of the low voltage timing chip for use by an internal logic circuit of the low voltage timing chip 203; the other terminal of the sixth capacitor C6 is connected to ground GND.

In order to maintain the normal operation of the basic logic circuit inside the low-voltage timing chip 203, a low-frequency crystal oscillator Y with a lower frequency is connected to the pin 23 and the pin, and the frequency of the low-frequency crystal oscillator Y2 is 32.768 kHz. Because the generated ultrasonic excitation signal has high excitation frequency and works discontinuously during the ultrasonic excitation signal, in order to reduce power consumption, a ceramic crystal oscillator Y1 with a high oscillation starting speed of 8MHz is connected to the pin 34 and the pin 35 of the low-voltage timing chip 203, and a frequency divider inside the low-voltage timing chip 203 divides the frequency of the clock signal 40 of 8MHz to generate a square wave signal of 200 kHz. However, since the amplitude of the signal is small, in order to increase the amplitude, a ninth capacitor C9 of 22uF is connected between pin 2 and pin 3 of the low voltage timing chip 203, an eleventh capacitor C11 of 22uF is connected between pin 1 and pin 48, and a tenth capacitor C10 of 22uF is connected between pin 4 and pin 5, and an ultrasonic excitation signal with an amplitude of 15V and a frequency of 200kHz is generated by switching the internal switches of the low voltage timing chip 203. And then the excitation voltage of the transducer is effectively improved, so that the transmitted ultrasonic signal is stronger. And the circuit is simple, the stability is high, and the volume is less.

As shown in fig. 3, the first crystal oscillator sub-circuit 201 includes: a ceramic crystal oscillator Y1 and a first resistor R1. Pin 1 of the ceramic crystal Y1 is connected to one end of the first resistor R1 and pin 34(XIN _4MHz) of the low voltage timer chip 203, pin 3 of the ceramic crystal Y1 is connected to the other end of the first resistor R1 and pin 35(XOUT _4MHz) of the low voltage timer chip 203, and pin 2 of the ceramic crystal Y1 is grounded to GND.

As shown in fig. 3, the second crystal oscillator circuit 202 includes: the low-frequency crystal oscillator Y2R2, the first capacitor C1 and the second capacitor C2. Pin 1 of the low-frequency crystal oscillator Y2 is connected to one end of a second resistor R2, one end of a second capacitor C2, and pin 23(XIN _32KHz) of the low-voltage timing chip 203, pin 3 of the low-frequency crystal oscillator Y2 is connected to the other end of the second resistor R2, one end of a first capacitor C1, and pin 24(XOUT _32KHz) of the low-voltage timing chip 203, and pin 2 of the low-frequency crystal oscillator Y2, the other end of the first capacitor C1, and the other end of the second capacitor C2 are all grounded to GND.

As shown in fig. 3, the low voltage transmitting circuit 200 further includes: the capacitor comprises a first parallel capacitor group CG1, a second parallel capacitor group CG2, a third parallel capacitor group CG3, a twelfth capacitor C12, a thirteenth capacitor C13, a fourteenth capacitor C14, a fifteenth capacitor C15, a sixteenth capacitor C16 and a sixth resistor R6. The first parallel capacitor bank CG2 includes 3 parallel capacitors, 22uF and 0.1uF respectively. Node C of the first parallel capacitor group CG1 is connected to pin 6(VCC _ CHP) of the low-voltage timing chip 203, and node D is connected to GND. The second parallel capacitor group CG2 includes 3 parallel capacitors, 1uF, 680mF and 0.1uF respectively. Node E of the second parallel capacitor group CG2 is connected to pin 15(US _ VREF) of the low voltage timing chip 203 and the 0.7V reference voltage VREF, and node F is connected to GND. The third parallel capacitor bank CG3 comprises 2 parallel capacitors, 22pF and 0.1uF respectively. Node G of the third parallel capacitor group CG3 is connected to pin 33(VDD _18IN) of the low-voltage timing chip 203 and the 1.8V voltage VCC, and node H is connected to GND. One end of the twelfth capacitor C12 is connected to the 3V VCC and the pin 12(VCC) of the low-voltage timing chip 203, and the other end is grounded to GND. One end of the thirteenth capacitor C13 is connected to the 3V VCC and the pin 19(VCC) of the low-voltage timing chip 203, and the other end is grounded to GND. One end of the fourteenth capacitor C14 is connected to the 3V VCC and the pin 36(VCC) of the low-voltage timing chip 203, and the other end is grounded to GND. One end of the sixteenth capacitor C16 is connected to the 3V VCC and the pin 47(VCC) of the low-voltage timing chip 203, and the other end is grounded to GND. One end of the fifteenth capacitor C15 is connected to the pin 40(TPI _ CLOAD) of the low voltage clock chip 203, one end of the sixth resistor R6 is connected to the pin 37(TPI _ REF) of the low voltage clock chip 203, and the other ends of the fifteenth capacitor C15 and the sixth resistor R6 are both grounded to GND. Pin 9(GND _ HV) and pin 49(PAD) of the low voltage timing chip 203 are both grounded to GND.

The receiving circuit 300 and the low-voltage transmitting circuit 200 both comprise a load switch U4, the load switch U4 of the receiving circuit 300 is connected with the microcontroller 100 and the second analog switch U2, and the load switch U4 of the low-voltage transmitting circuit 200 is connected with the microcontroller 100 and the low-voltage timing chip 203.

As shown in fig. 4, is a load switch U4 of the receiving circuit 300. Pin 1(Vout) of the load switch U4 outputs a power supply VCC _ RX, pin 2 is grounded GND, pin 4 and pin 5 are both connected to a 3.6V voltage Vin, and pin 6 is connected to the microcontroller 100. Since the receiving circuit does not need to be operated all the time, a load switch circuit composed of U4 is designed in the circuit in order to reduce power consumption. When the receive circuit 300 is not required to operate, the microcontroller 100 pulls pin 6 of the U4 load switch low. The power supply VCC _ RX of the receiving circuit 300 is cut off. When the receiving circuit 300 needs to operate, the microcontroller 100 pulls pin 6 of the load switch U4 high in advance, turning on the power supply VCC _ RX of the receiving circuit 300. The power consumption of the receiving circuit 300 is effectively reduced, and the service life of the battery is prolonged.

As shown in fig. 2, the pin 1 and the pin 16 of the first analog switch U1 are connected to the microcontroller 100, the pin 3, the pin 7, the pin 10 and the pin 15 are all grounded GND, the pin 2(EN) is connected to one end of a seventh resistor R7, the other end of the seventh resistor R7 is connected to an output power VCC _ RX, the pin 14 is connected to a power voltage VDD, the pin 13 is connected to the pin 1 of the first transducer S1, the pin 12 is connected to the pin 1 of the second transducer S2, the pin 11 is connected to the pin 1 of the third transducer S3, the pin 4 is connected to the pin 1 of the fourth transducer S4, the pin 5 is connected to the pin 1 of the fifth transducer S5, and the pin 6 is connected to the pin 1 of the sixth transducer S6.

Pins

2 and 3 of the first transducer S1, the second transducer S2, the third transducer S3, the fourth transducer S4, the fifth transducer S5 and the sixth transducer S6 are all grounded to GND.

The first analog switch U1 is an 8-way analog switch, the second analog switch U2 is a 2-way analog switch, and the third analog switch U3 is a 16-way analog switch. The microcontroller 100 includes a single chip microcomputer and the like.

For the receiving circuit 300, when pin 6(Rx _ sig _ UP) is used for transmission and pin 4(Rx _ sig _ DOWN) is used for reception, in order to isolate the transmission signal path from the reception signal path, the microcontroller 100 pulls pin 1 of the second analog switch U2 low, pin 5 of the second analog switch U2 is turned on with pin 4, and pin 5 and pin 6 are turned off, thereby removing the mutual interference between these pins. When pin 4(Rx _ sig _ DOWN) of the receiver circuit 300 is transmitting and pin 6(Rx _ sig _ UP) is receiving, to isolate the transmit signal path from the receive signal path, the microcontroller 100 pulls pin 1 of the second analog switch U2 high and pin 5 of the second analog switch U2 turns on with pin 5 and pin 4 off. Mutual interference between the pins is relieved. When the aperture is large and the flow rate is fast, the attenuation of the ultrasonic signal transmitted by the transmitting transducer S is large, which causes the ultrasonic signal received by the receiving transducer S to be weak, and the high-impedance amplifying sub-circuit 301 needs to have large gain to amplify the signal to be higher than the voltage required by the low-voltage timing chip 203. When the aperture is small and the flow rate is slow, the attenuation of the ultrasonic signal emitted by the emitting transducer S is small, so that the ultrasonic signal received by the receiving transducer S is strong, and the signal can be amplified to a voltage higher than the voltage required by the low-voltage timing chip 203 by the high-impedance amplification sub-circuit 301 with a small gain. In order to adapt to the adjustment of the amplification gain of the received signal under the conditions of different calibers and flow rates, the adjustment is realized by a voltage feedback operational amplifier (a high impedance amplifier A1) with extremely low noise, offset voltage and extremely high input impedance and a third analog switch U3 with an extremely low on-resistance 16 channel. When the receiving transducer S is used as a signal source, the internal resistance is higher, and according to the resistance voltage division principle, the adopted high-input-impedance operational high-impedance amplifier (high-impedance amplifier A1) can absorb the signal generated by the receiving transducer S to the greatest extent, so that the load effect on the signal source is reduced. Meanwhile, the high-impedance amplifier A1 has extremely low noise, so that the noise caused by the operational amplifier can be reduced while the signal is amplified, and the signal-to-noise ratio of the received signal is effectively improved. The non-inverting input pin 3 of the high impedance amplifier a1 is connected to the pin 5 of the second analog switch U2 for receiving the ultrasonic signal generated by the ultrasonic transducer S. A fourth resistor R4 is connected in series between the inverting input pin 4 of the high impedance amplifier a1 and the ground GND, and the fourth resistor R4 and the feedback resistors Rf1, Rf2, Rf3, Rf4, Rf5, Rf6, Rf7, Rf8, Rf9, Rf10, Rf11, Rf12, Rf13, Rf14, Rf15 and Rf16 jointly determine the gain of the high impedance amplifier a 1. Approximately equal to the ratio of the resistance of the feedback resistor Rf to the resistance of the fourth resistor R4. The connection (internal connection) of the pin 29 of the third analog switch U3 to the

pins

1, 2, 3, 4, 5, 6, 7, 8, 17, 18, 19, 20, 21, 22, 23, 24 thereof is realized by the microcontroller 100 controlling the level of the switch switching pins 10, 11, 14, 15 of the third analog switch U3 to be high or low. The 29 pin of the third analog switch U3 is connected to the inverting input pin 4 of the high impedance amplifier a1, and feedback resistors Rf1, Rf2, Rf3, Rf4, Rf5, Rf6, Rf7, Rf8, Rf9, Rf10, Rf11, Rf12, Rf13, Rf14, Rf15, and Rf16 with different resistances are respectively connected between the

pins

1, 2, 3, 4, 5, 6, 7, 8, 17, 18, 19, 20, 21, 22, 23, 24 of the third analog switch U3 and the output pin 1 of the high impedance amplifier a1, so that the gain of the high impedance amplification sub-circuit 301 is adjusted, and the amplification processing of signals at different calibers and flow rates is adapted. The amplified ultrasonic signal is output from pin 1 of the high impedance amplifier a 1. However, the amplified ultrasonic signal contains high frequency noise, and a low pass filter sub-circuit 302 is added to filter the high frequency noise.

For the low-voltage timing chip 203, the ultrasonic excitation signal of 200kHz output from the pin 7 and the pin 11 passes through the first matching resistor Rm1 and the second matching resistor Rm2 and is then input to the pin 8 and the pin 9 of the first analog switch U1. When the microcontroller 100 pulls both pin 1 and pin 16 of the first analog switch U1 low, pin 8 and pin 4 of the first analog switch U1 are conductive and pin 9 and pin 13 are conductive. When the microcontroller 100 pulls pin 1 of the first analog switch U1 high and pin 16 low, pins 8 and 5 of the first analog switch U1 are turned on and

pins

9 and 12 are turned on. When the microcontroller 100 pulls down the pin 1 and pulls up the pin 16 of the first analog switch U1, the pin 8 and the pin 6 of the first analog switch U1 are turned on, and the pin 9 and the pin 11 are turned on, so that the transducers S of different channels are sequentially excited in a time-sharing manner. Pin 2 of the first analog switch U1 is a power enable pin, and when the low voltage transmit circuit 200 needs to operate, the microcontroller 100 pulls pin 2 of the first analog switch U1 high, and when the low voltage transmit circuit 200 does not need to operate, the microcontroller 100 pulls this pin low. The power consumption of the low-voltage transmitting circuit 200 is effectively reduced, and the service life of the battery is prolonged. The Low voltage timing chip 203 is powered by 3V and has a Low Dropout Regulator (LDO) therein, which generates 1.8V and outputs it through the pin 46(VDD18_ OUT).

The impedance characteristic of the transducer S changes with the change of temperature, so that the null shift of the low-voltage transmitting circuit 200 and the receiving circuit 300 of the ultrasonic signal is large, and the flow metering error is large. This error is even greater when the output impedance of the low voltage transmit circuit 200 and the input impedance of the receive circuit 300 do not match. In order to reduce the matching degree of the low voltage transmitting circuit 200 and the receiving circuit 300, matching resistors Rm1 and Rm2 are added to the low voltage transmitting circuit 200. The receiving circuit 300 selects the high impedance amplifier a1 with a large input impedance. When transmitting ultrasonic signals, ultrasonic excitation signals of 200kHz output by the pin 7 of the low-voltage timing chip 203 enter the pin 9 of the first analog switch U1 through the matching resistor Rm18, and then the ultrasonic excitation signals are loaded on the transducer S3 to enable the transducer to transmit ultrasonic signals, and since the output impedance of the pin 7 of the low-voltage timing chip 203 is low and is equivalent to ground, an equivalent model of the low-voltage transmitting circuit 200 is shown in FIG. 5. When receiving ultrasonic signals, the pin 11 of the low-voltage timing chip 203 pulls the receiving transducer S7 to 0.7V through the resistor Rm2, which is equivalent to a short circuit to ground due to the extremely small power supply impedance, and the high-impedance amplifier a1 adopts an operational high-impedance amplifier with extremely large input impedance, which is equivalent to an open circuit, and the equivalent model of the receiving circuit 300 is shown in fig. 6. Therefore, the equivalent model of the transmitting system is the same as that of the receiving system, the influence of a peripheral circuit on the impedance characteristic of the transducer is eliminated, the null shift of a signal receiving and transmitting system of the ultrasonic flowmeter is greatly reduced, and the metering error of the ultrasonic flowmeter is reduced.

According to the embodiment of the application, the highest 15V ultrasonic excitation signal is generated by adopting the high-precision low-voltage timing chip 203 with the boosting charge pump integrated inside in the existing ultrasonic signal low-voltage transmitting circuit, and a transformer with large volume, heaviness, poor consistency, low power conversion rate, large power consumption and large radiation interference for boosting in the traditional circuit is replaced. The ultrasonic signal low-voltage transmitting circuit 200 effectively reduces the circuit area, the number of components and parts, improves the power utilization efficiency, reduces the power consumption, reduces the interference on a receiving circuit, improves the stability and consistency of the circuit, and improves the assembly efficiency. In the conventional ultrasonic receiving circuit, a voltage feedback type operational high impedance amplifier a1 having low input noise, low offset voltage, low temperature drift voltage, and high input impedance is used to amplify the received ultrasonic signal. The charge amplifier that adopts in traditional design is the electric capacity negative feedback, and needs a very big resistance among the feedback circuit, leads to receiving easily including various noise influences including the cable, and charge amplifier's null shift is very big, produces great error at the output, and resistance self can also bring great thermal noise, has reduced the SNR of received signal, and because the influence that receives parasitic capacitance and temperature easily leads to gain error to change great.

The ultrasonic signal receiving circuit 300 in the application is composed of the voltage feedback type operational high-impedance amplifier A1 with the third analog switch U3 with the extremely low input noise, low offset voltage, low temperature drift voltage and high input impedance, and the third analog switch U3 with the 16 channels, because the feedback circuit adopts resistance feedback, the influence of temperature and parasitic capacitance is small, the resistance value of the used resistor is small, the noise caused by the resistor is small, the signal-to-noise ratio of the received signal is effectively improved, the stability of the circuit is improved, and the third analog switch U3 with the 16 channels is adopted to realize 16-level adjustment of gain.

A first-stage filter circuit (low-pass filter sub-circuit 302) is added at the output end of the high-impedance amplification sub-circuit 301 for receiving signals, so that high-frequency interference signals can be effectively filtered. The signal-to-noise ratio of the received signal is improved, and meanwhile, the anti-interference capacity of the circuit is improved.

The load switch U4 is added in the signal low-voltage transmitting circuit and the signal receiving circuit, and the power supply of the whole circuit is cut off when the ultrasonic signal is not required to be transmitted and received through the control of an I/O port of the microcontroller 100, so that the purpose of reducing the power consumption is achieved. The load switch U4 of the application adopts TPS22860 to form a power supply circuit. When the low-voltage transmitting circuit 200 needs to work and the receiving circuit 300 does not need to work, the total power supply of the low-voltage transmitting circuit 200 is turned on, and the total power supply of the receiving circuit 300 is turned off; when the low-voltage transmitting circuit 200 does not need to work and the receiving circuit 300 needs to work, the total power supply of the low-voltage transmitting circuit 200 is turned off, and the total power supply of the receiving circuit 300 is turned on, so that the power consumption is effectively reduced.

Two matching resistors Rm1 and Rm2 are arranged in the signal low-voltage transmitting circuit 200 to form an impedance matching circuit, so that the null drift of a transmitting and receiving system is greatly reduced, and the metering error of the ultrasonic flowmeter is reduced.

The low-voltage transmitting circuit has the advantages that the low-voltage transmitting circuit can generate ultrasonic excitation signals with the amplitude of 15V and the frequency of 200kHz, the power consumption is low, and the safety is high; the excitation voltage of the transducer can be increased, so that the transmitted ultrasonic signal is stronger; the matching resistor in the first transmitting circuit can reduce zero drift, thereby reducing errors and improving the measurement precision. The high-impedance amplification sub-circuit in the receiving circuit can adjust the amplification gain according to the received signal, so that the receiving circuit can adapt to the adjustment of the amplification gain of the received signal under the conditions of different calibers and flow rates, has strong flexibility, reduces high power consumption caused by single amplification gain, and prolongs the service life of a battery. The ultrasonic signal low-voltage transmitting circuit adopts an excitation generating chip (low-voltage timing chip) of an integrated charge pump to replace the traditional transformer boosting scheme, so that the excitation signal is boosted, the power utilization rate is improved, the power consumption is reduced, and the interference of the low-voltage transmitting circuit on a receiving circuit is also reduced. The ultrasonic signal low-voltage transmitting circuit and the ultrasonic signal receiving circuit are both provided with load switch modules, and the low-voltage transmitting circuit or the ultrasonic signal receiving circuit is controlled by an IO port of the microcontroller, so that the low-voltage transmitting circuit or the ultrasonic signal receiving circuit is not required to be powered off when working, and the purpose of reducing power consumption is achieved. The ultrasonic signal receiving circuit adopts a voltage feedback type operational high-impedance amplifier with low offset, low temperature drift, low noise and high input impedance to combine with a 16-channel third analog switch, so that the ultrasonic signal receiving circuit is suitable for conveniently and quickly adjusting signals with different amplitudes, the signal-to-noise ratio of the received signals is improved, and the influence of the receiving circuit on temperature change is reduced. The low-pass filter sub-circuit is arranged at the output end of the high-impedance amplification sub-circuit in the receiving circuit for receiving signals and serves as a post-stage filter circuit, so that the interference of high-frequency noise is effectively filtered, the signal-to-noise ratio of the received signals is improved, and the capability of the circuit for resisting the interference of external signals is enhanced.

The above description in this specification is merely illustrative of the present invention. Those skilled in the art can make various modifications or additions to the described embodiments or substitute them in a similar manner without departing from the scope of the present invention as defined in the following claims.

Claims

1. A gas ultrasonic flow meter signal transceiver device, comprising: the system comprises a microcontroller, a low-voltage transmitting circuit, a receiving circuit, a first analog switch and a plurality of transducers;

2. The gas ultrasonic flowmeter signal transceiver of claim 1, wherein the receive circuit further comprises: a second analog switch and a low-pass filter sub-circuit;

3. A gas ultrasonic flow meter signal transceiver according to claim 2, wherein the high impedance amplification sub-circuit comprises: the high-impedance amplifier, the third analog switch and a plurality of feedback resistors;

4. A gas ultrasonic flow meter signal transceiver according to claim 3, wherein the low voltage transmit circuit comprises: the circuit comprises a low-voltage timing chip, a power supply filter sub-circuit, a first crystal oscillator sub-circuit, a second crystal oscillator circuit, a first matching resistor and a second matching resistor;

5. A gas ultrasonic flow meter signal transceiver according to claim 4, wherein the first crystal oscillator sub-circuit comprises: a ceramic crystal oscillator and a first resistor.

6. A gas ultrasonic flow meter signal transceiver according to claim 4, wherein the second crystal oscillator circuit comprises: the low-frequency crystal oscillator comprises a low-frequency crystal oscillator, a second resistor, a first capacitor and a second capacitor.

7. A gas ultrasonic flow meter signal transceiving apparatus according to claim 4, wherein the receive circuitry and low voltage transmit circuitry each comprise a load switch;

the load switch of the receiving circuit is connected with the microcontroller and the second analog switch;

8. The gas ultrasonic flowmeter signal transceiver of claim 1, wherein the first analog switch is an 8-way analog switch.

9. A gas ultrasonic flow meter signal transceiving apparatus according to claim 2, wherein the second analogue switch is a 2-way analogue switch.

10. A gas ultrasonic flow meter signal transceiving apparatus according to claim 3, wherein the third analogue switch is a 16-way analogue switch.