Electromagnetic flowmeter, spraying device and unmanned equipment

Abstract

According to the electromagnetic flowmeter, the spraying device and the unmanned equipment provided by the embodiment of the invention, the electromagnetic flowmeter comprises a first measurement module, a second measurement module, a differential amplification circuit and a first interference elimination module, and the first positive input end of the differential amplification circuit is electrically connected with the first measurement module; a second positive input end of the differential amplification circuit is electrically connected with the second measurement module; one end of the first interference elimination module is electrically connected with the first negative input end of the differential amplification circuit, and the other end of the first interference elimination module is electrically connected with the second negative input end of the differential amplification circuit through the magnetic field area. By adding the first interference elimination module in the electromagnetic flowmeter, the magnetic field interference between the first negative input end and the second negative input end of the differential amplification circuit can be eliminated, so that a connecting line of the differential amplification circuit does not need to be completely symmetrical with the magnetic field distribution, the requirement of the differential amplification circuit and the magnetic field distribution on symmetry is reduced, and the electromagnetic flowmeter is more stable in performance. Therefore, the accuracy of the electromagnetic flowmeter can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flow measurement, and in particular to an electromagnetic flowmeter, a spraying device and unmanned equipment. Background Art

[0002] Electromagnetic flowmeter is a measuring device used in measuring parameters of industrial and agricultural production processes. It applies the principle of electromagnetic induction and measures flow rate based on the electromotive force induced when a conductive fluid passes through an external magnetic field. Differential circuits are often used in electromagnetic flowmeters to sample the measuring electrodes.

[0003] In the prior art, the differential circuit of the electromagnetic flowmeter is connected to the measuring electrodes, which are distributed on both sides of the measuring pipe. When the signals of the measuring electrodes on both sides are merged through the connecting line of the differential circuit, they will inevitably pass through the strong magnetic field area. If the connecting line is slightly asymmetric with the magnetic field distribution, it will cause serious interference, thereby affecting the accuracy of the electromagnetic flowmeter. Summary of the invention

[0004] In view of this, an object of the present invention is to provide an electromagnetic flowmeter, a spraying device and unmanned equipment to improve the accuracy of the electromagnetic flowmeter.

[0005] In a first aspect, the present invention provides an electromagnetic flowmeter, the electromagnetic flowmeter comprising a first measuring module, a second measuring module, a differential amplifier circuit and a first interference elimination module; the first measuring module and the second measuring module are used to measure the induced electromotive force signal generated by the measured fluid in the pipeline passing through the magnetic field region;

[0006] The first positive input terminal of the differential amplifier circuit is electrically connected to the first measurement module, and the second positive input terminal of the differential amplifier circuit is electrically connected to the second measurement module; one end of the first interference elimination module is electrically connected to the first negative input terminal of the differential amplifier circuit, and the other end of the first interference elimination module is electrically connected to the second negative input terminal of the differential amplifier circuit through the magnetic field region;

[0007] The differential amplifier circuit is used to perform differential amplification processing according to the induced electromotive force signals input by the first measurement module and the second measurement module, and output a differential amplified signal; the differential amplified signal is used to generate a flow measurement result;

[0008] The first interference elimination module is used to eliminate the magnetic field interference between the first negative input terminal and the second negative input terminal of the differential amplifier circuit.

[0009] In an optional implementation, the first interference elimination module includes a first connecting line, a second connecting line, a first transformer, and a second transformer;

[0010] The first transformer is electrically connected to a first negative input terminal of the differential amplifier circuit, the second transformer is electrically connected to a second negative input terminal of the differential amplifier circuit, the first connecting wire and the second connecting wire are connected between the first transformer and the second transformer, and the first connecting wire and the second connecting wire are arranged in the magnetic field region; wherein the induced electromotive forces on the first connecting wire and the second connecting wire are equal in magnitude and opposite in direction.

[0011] In an optional implementation manner, the first interference elimination module further includes a first resistor, a second resistor, a third resistor and a fourth resistor;

[0012] One end of the first resistor is electrically connected to the opposite-name end of the first winding of the first transformer, and the other end of the first resistor is electrically connected to the first negative input end of the differential amplifier circuit; one end of the second resistor is electrically connected to the same-name end of the first winding of the second transformer, and the other end of the second resistor is electrically connected to the second negative input end of the differential amplifier circuit; one end of the third resistor is electrically connected to the same-name end of the second winding of the first transformer, and the other end of the third resistor is grounded; one end of the fourth resistor is electrically connected to the opposite-name end of the second winding of the second transformer, and the other end of the fourth resistor is grounded;

[0013] The first connecting line is connected between the same-name end of the first winding of the first transformer and the opposite-name end of the first winding of the second transformer, and the second connecting line is connected between the opposite-name end of the second winding of the first transformer and the same-name end of the second winding of the second transformer.

[0014] In an optional implementation, the differential amplifier circuit includes a first operational amplifier and a second operational amplifier;

[0015] The negative input terminal of the first operational amplifier is electrically connected to the opposite-name terminal of the first winding of the first transformer through the first resistor, and the positive input terminal of the first operational amplifier is electrically connected to the first measurement module;

[0016] The negative input terminal of the second operational amplifier is electrically connected to the same-name terminal of the first winding of the second transformer through the second resistor, and the positive input terminal of the second operational amplifier is electrically connected to the second measuring module.

[0017] In an optional embodiment, the differential amplifier circuit further includes a secondary amplifier module and a second interference elimination module, one end of the second interference elimination module is electrically connected to the first input end of the secondary amplifier module, the other end of the second interference elimination module is electrically connected to the output end of the second operational amplifier through the magnetic field region, and the second input end of the secondary amplifier module is electrically connected to the output end of the first operational amplifier;

[0018] The second interference elimination module is used to eliminate the magnetic field interference between the output end of the second operational amplifier and the first input end of the secondary amplification module.

[0019] In an optional implementation, the second interference elimination module includes a third connecting line, a fourth connecting line and a third transformer;

[0020] The third transformer is electrically connected to the first input end of the secondary amplification module, the third connecting line is connected between the third transformer and the output end of the second operational amplifier, one end of the fourth connecting line is electrically connected to the third transformer, and the other end of the fourth connecting line is grounded; the third connecting line and the fourth connecting line are arranged in the magnetic field region; wherein the induced electromotive forces on the third connecting line and the fourth connecting line are equal in magnitude and opposite in direction.

[0021] In an optional implementation, the second interference elimination module further includes a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor;

[0022] One end of the fifth resistor is electrically connected to the output end of the second operational amplifier, and the other end of the fifth resistor is electrically connected to the same-name end of the first winding of the third transformer through the third connecting line; the sixth resistor is electrically connected between the opposite-name end of the first winding of the third transformer and the first input end of the secondary amplification module;

[0023] One end of the seventh resistor is electrically connected to the opposite-name end of the second winding of the third transformer through the fourth connecting line, and the other end of the seventh resistor is grounded; one end of the eighth resistor is electrically connected to the same-name end of the second winding of the third transformer, and the other end of the eighth resistor is grounded.

[0024] In an optional embodiment, the electromagnetic flowmeter further includes an excitation circuit and an excitation coil, the excitation circuit includes a switching power supply, a constant current circuit, an H-bridge circuit and a voltage comparison circuit; the switching power supply is electrically connected to the constant current circuit, the constant current circuit is electrically connected to the H-bridge circuit and the voltage comparison circuit, the H-bridge circuit is electrically connected to the excitation coil, and the voltage comparison circuit is electrically connected to the switching power supply; the excitation coil is used to generate the magnetic field region;

[0025] The H-bridge circuit is used to provide an excitation current for the excitation coil;

[0026] The constant current circuit is used to sample the excitation current provided by the H-bridge circuit to obtain a sampling voltage, and adjust the current output to the H-bridge circuit according to the sampling voltage so that the output current of the constant current circuit is constant;

[0027] The voltage comparison circuit is used to adjust the output voltage of the switching power supply according to the sampled voltage.

[0028] In an optional embodiment, the voltage comparison circuit includes a power supply chip and a voltage feedback circuit, the feedback pin of the power supply chip is electrically connected to the output end of the voltage feedback circuit, the switch pin of the power supply chip is electrically connected to the switching power supply; the input end of the voltage feedback circuit is electrically connected to the constant current circuit;

[0029] The voltage feedback circuit is used to output a feedback voltage to a feedback pin of the power chip according to a comparison result between the sampled voltage and the set voltage;

[0030] The power chip is used to adjust the output voltage of the switch pin according to the feedback voltage, and further adjust the output voltage of the switching power supply through the output voltage of the switch pin.

[0031] In an optional implementation, the voltage feedback circuit includes a reference power supply, a comparator, a field effect transistor, a ninth resistor, a tenth resistor, and an eleventh resistor;

[0032] One end of the ninth resistor and the tenth resistor connected in series is electrically connected between the switch pin of the power chip and the switching power supply, and the other end of the ninth resistor and the tenth resistor connected in series is grounded; one end of the eleventh resistor is electrically connected between the ninth resistor and the tenth resistor, the other end of the eleventh resistor is electrically connected to the source of the field effect tube, the gate of the field effect tube is electrically connected to the output end of the comparator, and the drain of the field effect tube is grounded;

[0033] The positive input terminal of the comparator is electrically connected to the reference power supply, and the negative input terminal of the comparator is electrically connected to the constant current circuit; the feedback pin of the power chip is electrically connected between the ninth resistor and the tenth resistor.

[0034] In a second aspect, the present invention provides a spraying device, comprising the electromagnetic flowmeter described in any one of the aforementioned embodiments.

[0035] In a third aspect, the present invention provides an unmanned equipment, comprising the spraying device of the aforementioned embodiment.

[0036] The electromagnetic flowmeter, spraying device and unmanned equipment provided by the embodiments of the present invention include a first measuring module, a second measuring module, a differential amplifier circuit and a first interference elimination module. The first measuring module and the second measuring module are used to measure the induced electromotive force signal generated by the measured fluid in the pipeline passing through the magnetic field area; the first positive input terminal of the differential amplifier circuit is electrically connected to the first measuring module, and the second positive input terminal of the differential amplifier circuit is electrically connected to the second measuring module; one end of the first interference elimination module is electrically connected to the first negative input terminal of the differential amplifier circuit, and the other end of the first interference elimination module is electrically connected to the second negative input terminal of the differential amplifier circuit through the magnetic field area; the differential amplifier circuit is used to perform differential amplification processing according to the induced electromotive force signal input by the first measuring module and the second measuring module, and output a differential amplification signal; the differential amplification signal is used to generate a flow measurement result; the first interference elimination module is used to eliminate the magnetic field interference between the first negative input terminal and the second negative input terminal of the differential amplifier circuit. By adding a first interference elimination module to the electromagnetic flowmeter and electrically connecting the first interference elimination module to the first negative input terminal of the differential circuit and the second negative input terminal of the differential circuit through the magnetic field region, the magnetic field interference between the first negative input terminal and the second negative input terminal of the differential amplifier circuit can be eliminated. In this way, there is no need for the connecting wires of the differential amplifier circuit to be completely symmetrical with the magnetic field distribution, thereby reducing the symmetry requirements of the connecting wires of the differential amplifier circuit and the magnetic field distribution, and thus the accuracy of the electromagnetic flowmeter can be effectively improved.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 A schematic diagram of the structure of an electromagnetic flowmeter in the prior art is shown;

[0040] Figure 2 A schematic diagram of a circuit block diagram of an electromagnetic flowmeter provided by an embodiment of the present invention is shown;

[0041] Figure 3 A structural block diagram of a first interference elimination module of an electromagnetic flowmeter provided by an embodiment of the present invention is shown;

[0042] Figure 4A schematic diagram of a circuit structure of a first interference elimination module of an electromagnetic flowmeter provided by an embodiment of the present invention is shown;

[0043] Figure 5 A circuit structure schematic diagram of a differential amplifier circuit of an electromagnetic flowmeter provided in an embodiment of the present invention is shown;

[0044] Figure 6 Another circuit structure schematic diagram of a differential amplifier circuit of an electromagnetic flowmeter provided in an embodiment of the present invention is shown;

[0045] Figure 7 Another circuit structure schematic diagram of a differential amplifier circuit of an electromagnetic flowmeter provided in an embodiment of the present invention is shown;

[0046] Figure 8 Another circuit structure schematic diagram of a differential amplifier circuit of an electromagnetic flowmeter provided in an embodiment of the present invention is shown;

[0047] Fig. 9 Another circuit structure schematic diagram of a differential amplifier circuit of an electromagnetic flowmeter provided in an embodiment of the present invention is shown;

[0048] Fig.10 Another circuit block diagram of an electromagnetic flowmeter provided by an embodiment of the present invention is shown;

[0049] Fig.11 A schematic diagram of a circuit block diagram of a constant current circuit of an electromagnetic flowmeter provided in an embodiment of the present invention is shown;

[0050] Fig.12 A schematic diagram showing the voltage output by the constant voltage power supply of the excitation circuit and the current output by the constant current circuit of the electromagnetic flowmeter provided in an embodiment of the present invention is shown;

[0051] Fig.13 A schematic diagram of a circuit structure of an electromagnetic flowmeter provided by an embodiment of the present invention is shown;

[0052] Fig.14 Another circuit structure schematic diagram of a voltage comparison circuit of an electromagnetic flowmeter provided in an embodiment of the present invention is shown.

[0053] Description of the main component symbols: 111-first measurement module; 112-second measurement module; 120-differential amplifier circuit; 130-first interference elimination module; 122-second interference elimination module; A1-first positive input terminal; A2-second positive input terminal; B1-first negative input terminal; B2-second negative input terminal; C1-first input terminal; C2-second input terminal; Net1-first connecting wire; Net2-second connecting wire; Net3-third connecting wire; Net4-fourth connecting wire; R1-first resistor; R2-second resistor; R3-third resistor; R4-fourth resistor; R5-fifth resistor; R6-sixth resistor; R7-seventh resistor; R8-eighth resistor; R9-ninth resistor; R10-tenth resistor; R11-tenth A resistor; R12-the twelfth resistor; R13-the thirteenth resistor; R14-the fourteenth resistor; R15-the fifteenth resistor; R16-the sixteenth resistor; R17-the seventeenth resistor; R18-the eighteenth resistor; R19-the nineteenth resistor; T1-the first transformer; T2-the second transformer; T3-the first transformer; U1-the first operational amplifier; U2-the second operational amplifier; U3-the third operational amplifier; U4-the fourth operational amplifier; U5-comparator; 210-switching power supply; 220-constant current circuit; 221-current limiting circuit; 222-current error amplifier circuit; 223-current sampling circuit; 230-H bridge circuit; 240-voltage comparison circuit; 241-power chip; 242-voltage feedback circuit; 250-excitation coil. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0055] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as just or implying relative importance.

[0057] In the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] Electromagnetic flowmeter is a measuring instrument used in industrial and agricultural production process parameter measurement. It is widely used and has great effects. Existing electromagnetic flowmeters have the advantages of simple structure, no parts that hinder fluid flow, large range ratio, large measurement range, and small error.

[0059] However, in the prior art, the differential circuit of the electromagnetic flowmeter is connected to the measuring electrodes, and the measuring electrodes are distributed on both sides of the measuring pipe. When the signals of the measuring electrodes on both sides are merged through the connecting line of the differential circuit, it will inevitably pass through the strong magnetic field area. If the connecting line and the magnetic field distribution are slightly asymmetric, it will cause serious interference, thereby affecting the accuracy of the electromagnetic flowmeter.

[0060] like Figure 1 As shown, the measuring electrodes of the electromagnetic flowmeter are distributed on both sides of the measuring pipeline, and the differential circuit is set on the circuit boards on both sides (circuit board A and circuit board B). When performing differential sampling, the measurement signals on both sides need to be merged and differentially amplified. The wiring (connecting wire) connecting the two circuit boards will inevitably pass through the strong magnetic field generated by the coil. If the wiring is symmetrical, the induced voltages generated on both sides are exactly the same in magnitude and opposite in direction, and there will be no induced voltage as a whole. If the wiring is slightly skewed, the magnetic flux changes brought about by the magnetic field changes on both sides of the wiring will be different. The induced voltages generated by the wiring from both sides will not be the same. From the overall point of view, there will be induced voltage on the wiring, and this induced voltage will be regarded as a useful signal, which will have a serious impact on the measurement results.

[0061] In view of the above problems, the inventors have discovered after long-term research and proposed the electromagnetic flowmeter, spraying device and unmanned equipment provided in the embodiments of the present invention. By adding a first interference elimination module in the electromagnetic flowmeter and electrically connecting the first interference elimination module to the first negative input terminal of the differential circuit and the second negative input terminal of the differential circuit through the magnetic field area, the magnetic field interference between the first negative input terminal and the second negative input terminal of the differential amplifier circuit can be eliminated. In this way, there is no need for the connecting wires of the differential amplifier circuit to be completely symmetrical with the magnetic field distribution, thereby reducing the symmetry requirements of the connecting wires of the differential amplifier circuit and the magnetic field distribution, and can effectively improve the accuracy of the electromagnetic flowmeter.

[0062] See also Figure 2 , Figure 2 A circuit block diagram of an electromagnetic flowmeter provided by an embodiment of the present invention is shown. The electromagnetic flowmeter includes a first measuring module 111, a second measuring module 112, a differential amplifier circuit 120, and a first interference elimination module 130. The first measuring module 111 and the second measuring module 112 are used to measure the induced electromotive force signal generated by the measured fluid in the pipeline passing through the magnetic field area.

[0063] The first positive input terminal A1 of the differential amplifier circuit 120 is electrically connected to the first measurement module 111, the second positive input terminal A2 of the differential amplifier circuit 120 is electrically connected to the second measurement module 112, one end of the first interference elimination module 130 is electrically connected to the first negative input terminal B1 of the differential amplifier circuit 120, and the other end of the first interference elimination module 160 passes through the magnetic field area ( Figure 2 The voltage (not shown in the figure, which may be generated by a coil) is electrically connected to the second negative input terminal B2 of the differential amplifier circuit 120.

[0064] The first interference elimination module 130 is used to eliminate the magnetic field interference between the first negative input terminal B1 and the second negative input terminal B2 of the differential amplifier circuit 120 .

[0065] As an embodiment, the first measurement module 111 can be a measurement positive electrode, which is electrically connected to the first positive input terminal of the differential amplifier circuit 120; the second measurement module 112 can be a measurement negative electrode, which is electrically connected to the second positive input terminal A2 of the differential amplifier circuit 120.

[0066] The differential amplifier circuit 120 is used to perform differential amplification processing according to the induced electromotive force signals input by the first measurement module 111 and the second measurement module 112, and output a differential amplified signal, and the differential amplified signal is used to generate a flow measurement result.

[0067] In some embodiments, the electromagnetic flowmeter may further include an ADC sampling module, which may process the differential amplified signal output by the differential amplifier circuit 120 to generate a flow measurement result. The ADC sampling module may include a single-ended ADC sampling module and a dual-ended ADC sampling module.

[0068] As an implementation mode, the ADC sampling module is a single-ended ADC sampling module. If the output of the differential amplifier circuit 120 is dual-ended, a single-ended conversion module can be added to convert the output of the differential amplifier circuit 120 from a dual-ended output to a single-ended output, and then the differential amplified signal is output from the single-ended output to the single-ended ADC sampling module to generate a flow measurement result; if the output of the differential amplifier circuit 120 is single-ended, the differential amplifier circuit 120 can directly output the differential amplified signal to the single-ended ADC sampling module to generate a flow measurement result.

[0069] It can be seen that the electromagnetic flowmeter provided by the embodiment of the present invention includes a first measuring module, a second measuring module, a differential amplifier circuit and a first interference elimination module. The first positive input terminal of the differential amplifier circuit is electrically connected to the first measuring module, and the second positive input terminal of the differential amplifier circuit is electrically connected to the second measuring module; one end of the first interference elimination module is electrically connected to the first negative input terminal of the differential amplifier circuit, and the other end of the first interference elimination module is electrically connected to the second negative input terminal of the differential amplifier circuit through the magnetic field region. By adding the first interference elimination module to the electromagnetic flowmeter, the magnetic field interference between the first negative input terminal and the second negative input terminal of the differential amplifier circuit can be eliminated. In this way, it is not necessary for the connection line of the differential amplifier circuit to be completely symmetrical with the magnetic field distribution, which reduces the requirements on the symmetry between the differential amplifier circuit and the magnetic field distribution, so the accuracy of the electromagnetic flowmeter can be effectively improved.

[0070] See also Figure 3 , Figure 3 The structure block diagram of the first interference elimination module of the electromagnetic flowmeter provided by the embodiment of the present invention is shown. The first interference elimination module 130 includes a first connecting line Net1, a second connecting line Net2, a first transformer T1 and a second transformer T2.

[0071] The first transformer T1 is electrically connected to the first negative input terminal B1 of the differential amplifier circuit 120, the second transformer T2 is electrically connected to the second negative input terminal B2 of the differential amplifier circuit, the first connecting wire Net1 and the second connecting wire Net2 are connected between the first transformer T1 and the second transformer T2, and the first connecting wire Net1 and the second connecting wire Net2 are arranged in the magnetic field region; wherein the induced electromotive forces on the first connecting wire Net1 and the second connecting wire Net2 are equal in magnitude and opposite in direction.

[0072] Since the first interference elimination module 130 can generate an induced electromotive force on the second connection line Net2 that is equal in magnitude and opposite in direction to that on the first connection line Net1, the interference signals generated on the first connection line Net1 and the second connection line Net2 due to passing through the magnetic field area can cancel each other, thereby eliminating the magnetic field interference between the first negative input terminal B1 and the second negative input terminal B2 of the differential amplifier circuit 120.

[0073] In one embodiment, see Figure 4 , Figure 4 A schematic diagram of a circuit structure of a first interference elimination module of an electromagnetic flowmeter provided in an embodiment of the present invention is shown. The first interference elimination module 130 further includes a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4.

[0074] One end of the first resistor R1 is electrically connected to the opposite-name end of the first winding of the first transformer T1, and the other end of the first resistor R1 is electrically connected to the first negative input terminal B1 of the differential amplifier circuit 120; one end of the second resistor R2 is electrically connected to the same-name end of the first winding of the second transformer T2, and the other end of the second resistor R2 is electrically connected to the second negative input terminal B2 of the differential amplifier circuit 120; one end of the third resistor R3 is electrically connected to the same-name end of the second winding of the first transformer T1, and the other end of the third resistor R3 is grounded; one end of the fourth resistor R4 is electrically connected to the opposite-name end of the second winding of the second transformer T2, and the other end of the fourth resistor R4 is grounded.

[0075] The first connection line Net1 is connected between the same-name end of the first winding of the first transformer T1 and the opposite-name end of the first winding of the second transformer T2, and the second connection line Net2 is connected between the opposite-name end of the second winding of the first transformer T1 and the same-name end of the second winding of the second transformer T2.

[0076] In some embodiments, the first connection line Net1 and the second connection line Net2 can be wired together, the number of turns of the primary of the first winding of the first transformer T1 is the same as the number of turns of the secondary of the second winding of the first transformer T1, and the number of turns of the primary of the first winding of the second transformer T2 is the same as the number of turns of the secondary of the second winding of the second transformer T2. As an embodiment, the first transformer T1 can be replaced with a first common mode voltage, and the second transformer T2 can be replaced with a second common mode voltage. It should be noted that when the number of turns of the first winding of the transformer is the same as the number of turns of the second winding, the transformer is equivalent to the common mode voltage.

[0077] In some embodiments, in order to maintain the induced electromotive force and current on the first connection line Net1 and the second connection line Net2 to be equal, a third resistor R3 and a fourth resistor R4 are set, wherein the resistance value of the first resistor R1 is equal to the resistance value of the third resistor R3, and the resistance value of the second resistor R2 is equal to the resistance value of the fourth resistor R4.

[0078] As an implementation manner, the resistance value of the first resistor R1 may be equal to or different from the resistance value of the second resistor R2; correspondingly, the resistance value of the third resistor R3 may be equal to or different from the resistance value of the fourth resistor R4.

[0079] Since the resistance of the first resistor R1 is equal to the resistance of the third resistor R3, the resistance of the second resistor R2 is equal to the resistance of the fourth resistor R4, and the number of turns of the first winding of the first transformer T1 and the second winding of the first transformer T1 is equal, the induced electromotive force on the first connecting wire Net1 and the second connecting wire Net2 is equal; at the same time, since the first connecting wire Net1 is electrically connected between the same-name end of the first winding of the first transformer T1 and the opposite-name end of the first winding of the second transformer T2, and the second connecting wire Net2 is electrically connected between the opposite-name end of the second winding of the first transformer T1 and the same-name end of the second winding of the second transformer T2, the induced electromotive force on the first connecting wire Net1 is opposite in direction to the induced electromotive force on the second connecting wire Net2. Therefore, the first interference elimination module 130 can generate an induced electromotive force on the second connecting wire Net2 that is equal in size and opposite in direction to that on the first connecting wire Net1, thereby eliminating the magnetic field interference between the first negative input terminal B1 and the second negative input terminal B2 of the differential amplifier circuit 120.

[0080] See also Figure 5 , Figure 5 A circuit structure diagram of a differential amplifier circuit of an electromagnetic flowmeter provided by an embodiment of the present invention is shown. The differential amplifier circuit 120 includes a first operational amplifier U1, a second operational amplifier U2, a twelfth resistor R12, and a thirteenth resistor R13. The first negative input terminal B1 of the differential amplifier circuit is the negative input terminal of the first operational amplifier U1, and the second negative input terminal B2 of the differential amplifier circuit is the negative input terminal of the second operational amplifier U2; the first positive input terminal A1 of the differential amplifier circuit is the positive input terminal of the first operational amplifier U1, and the second positive input terminal A2 of the differential amplifier circuit is the positive input terminal of the second operational amplifier U2.

[0081] The negative input terminal of the first operational amplifier U1 is electrically connected to the opposite-name end of the first winding of the first transformer T1 through the first resistor R1, and the positive input terminal of the first operational amplifier U1 is electrically connected to the first measuring module 111; one end of the twelfth resistor R12 is electrically connected between the negative input terminal of the first operational amplifier U1 and the first resistor R1, and the other end of the twelfth resistor R12 is electrically connected to the output terminal of the first operational amplifier U1.

[0082] The negative input terminal of the second operational amplifier U2 is electrically connected to the same-name terminal of the first winding of the second transformer T2 through the second resistor R2, the positive input terminal of the second operational amplifier U2 is electrically connected to the second measuring module 112, one end of the thirteenth resistor R13 is electrically connected between the negative input terminal of the second operational amplifier U2 and the second resistor R2, and the other end of the thirteenth resistor R13 is electrically connected to the output terminal of the second operational amplifier U2.

[0083] It can be understood that the induced electromotive force signals detected by the first measuring module 111 and the second measuring module 112 are input to the first operational amplifier U1 and the second operational amplifier U2, and are differentially amplified by the first operational amplifier U1 and the second operational amplifier U2, and the differential amplified signals are output through the output ends of the first operational amplifier U1 and the second operational amplifier U2.

[0084] It can be seen that by adding two transformers at both ends of the connecting line (first connecting line Net1) between the negative input terminals of the first operational amplifier U1 and the second operational amplifier U2, and forming induced electromotive forces of equal magnitude and opposite directions on the second connecting line Net2 between the two transformers and the first connecting line Net1, the opposite induced electromotive forces will cancel each other out. In this way, there will be no interference signal on the first connecting line Net1 passing through the magnetic field area, and further, no magnetic field interference signal will be induced on the negative input terminals of the first operational amplifier U1 and the second operational amplifier U2, thereby improving the measurement accuracy.

[0085] In practical applications, in order to ensure the signal amplification effect of the differential amplifier circuit and thus improve the accuracy of the flow measurement results, a secondary amplifier module will be added to the differential amplifier circuit, and the connecting line between the output end of the second operational amplifier and the secondary amplifier module will still pass through the magnetic field area, and the generated interference signal will also affect the measurement accuracy. Based on this, the embodiment of the present invention adds a second interference elimination module to the electromagnetic flowmeter, and the magnetic field interference is eliminated by the second interference elimination module.

[0086] See also Figure 6 , Figure 6 Another circuit structure diagram of the differential amplifier circuit of the electromagnetic flowmeter provided by the embodiment of the present invention is shown. The differential amplifier circuit 120 further includes a secondary amplifier module 121 and a second interference elimination module 122 .

[0087] One end of the second interference elimination module 122 is electrically connected to the first input end C1 of the secondary amplification module 121, and the other end of the second interference elimination module 122 is electrically connected to the output end of the second operational amplifier U2 through the magnetic field area. The second input end C2 of the secondary amplification module 121 is electrically connected to the output end of the first operational amplifier U1.

[0088] The second interference elimination module 122 is used to eliminate the magnetic field interference between the output terminal of the second operational amplifier and the first input terminal C1 of the secondary amplification module.

[0089] It can be understood that in this embodiment, the induced electromotive force signal input into the differential amplifier circuit 120 by the first measurement module and the second measurement module is first differentially amplified by the first operational amplifier U1 and the second operational amplifier U2, and then secondary amplified by the secondary amplifier module 121 to obtain the final differential amplified signal. Finally, the differential amplified signal output by the secondary amplifier module 121 is processed by the ADC sampling module to generate a flow measurement result.

[0090] It can be seen that when the differential amplifier circuit 120 includes a secondary amplifier module 121, by setting a second interference elimination module 122 in the electromagnetic flowmeter, the magnetic field interference between the output end of the second operational amplifier U2 and the first input end C1 of the secondary amplifier module 121 can be eliminated, thereby further improving the accuracy of the electromagnetic flowmeter.

[0091] See also Figure 7 , Figure 7 Another circuit structure diagram of the differential amplifier circuit of the electromagnetic flowmeter provided by the embodiment of the present invention is shown. The second interference elimination module 122 includes a third connecting line Net3, a fourth connecting line Net4 and a third transformer T3.

[0092] The third transformer T3 is electrically connected to the first input terminal C1 of the secondary amplification module 121, the third connection line Net3 is connected between the third transformer T3 and the output terminal of the second operational amplifier U2, one end of the fourth connection line Net4 is electrically connected to the third transformer T3, the other end of the fourth connection line Net4 is grounded, and the third connection line and the fourth connection line are arranged in the magnetic field region. The induced electromotive force on the third connection line Net3 and the fourth connection line Net4 is equal in magnitude and opposite in direction.

[0093] Since the second interference elimination module 122 can generate an induced electromotive force on the fourth connection line Net4 that is equal in magnitude and opposite in direction to that on the third connection line Net3, the interference signals generated on the third connection line Net3 and the fourth connection line Net4 due to passing through the magnetic field area can cancel each other out, thereby eliminating the magnetic field interference between the output end of the second operational amplifier U2 and the first input end C1 of the secondary amplification module 121.

[0094] In one embodiment, see Figure 8 , Figure 8 FIG. 1 is a schematic diagram showing another circuit structure of a differential amplifier circuit of an electromagnetic flowmeter provided in an embodiment of the present invention. The second interference elimination module 122 may further include a fifth resistor R5, a sixth resistor R6, a seventh resistor R7 and an eighth resistor R8.

[0095] One end of the fifth resistor R5 is electrically connected to the output end of the second operational amplifier U2, and the other end of the fifth resistor R5 is electrically connected to the same-name end of the first winding of the third transformer T3 through the third connecting line Net3; the sixth resistor R6 is electrically connected between the opposite-name end of the first winding of the third transformer T3 and the first input end C1 of the secondary amplification module 121; one end of the seventh resistor R7 is electrically connected to the opposite-name end of the second winding of the third transformer T3 through the fourth connecting line Net4, and the other end of the seventh resistor R7 is grounded; one end of the eighth resistor R8 is electrically connected to the same-name end of the second winding of the third transformer T3, and the other end of the eighth resistor R8 is grounded.

[0096] That is, the third connection line Net3 is connected between the fifth resistor R5 and the same-name end of the first winding of the third transformer T3, and the fourth connection line Net4 is connected between the seventh resistor R7 and the opposite-name end of the second winding of the third transformer.

[0097] In some embodiments, the third connecting line Net3 and the fourth connecting line Net4 are wired as close together as possible, and the number of turns of the primary of the first winding of the third transformer T3 is the same as the number of turns of the secondary of the second winding of the first transformer T3. As an implementation method, the third transformer T3 can be replaced by a third common mode voltage. It should be noted that when the number of turns of the first winding of the transformer is the same as the number of turns of the second winding, the transformer is equivalent to the common mode voltage.

[0098] In some embodiments, in order to maintain the induced electromotive force and current on the third connection line Net3 and the fourth connection line Net4 to be equal, a seventh resistor R7 and an eighth resistor R8 are set, wherein the resistance value of the fifth resistor R5 is equal to the resistance value of the seventh resistor R7, and the resistance value of the sixth resistor R6 is equal to the resistance value of the eighth resistor R8.

[0099] As an implementation manner, the resistance value of the fifth resistor R5 may be equal to or different from the resistance value of the sixth resistor R6; correspondingly, the resistance value of the seventh resistor R7 may be equal to or different from the resistance value of the eighth resistor R8.

[0100] Since the resistance of the seventh resistor R7 is equal to the resistance of the fifth resistor R5, the resistance of the sixth resistor R6 is equal to the resistance of the eighth resistor R8, and the number of turns of the first winding of the third transformer T3 and the second winding of the third transformer T3 are equal, the induced electromotive force on the third connecting wire Net3 and the fourth connecting wire Net4 are equal in magnitude; at the same time, since one end of the third connecting wire Net3 is electrically connected to the same-name end of the first winding of the third transformer T3, and one end of the fourth connecting wire Net4 is electrically connected to the opposite-name end of the second winding of the third transformer T3, the induced electromotive force on the third connecting wire Net3 and the fourth connecting wire Net4 are opposite in direction. Therefore, the second interference elimination module 122 can generate an induced electromotive force on the fourth connecting wire Net4 that is equal in magnitude and opposite in direction to that on the third connecting wire Net3, thereby eliminating the magnetic field interference between the output end of the second operational amplifier and the first input end C1 of the secondary amplification module.

[0101] See also Fig. 9 , Fig. 9 Another circuit structure diagram of the electromagnetic flowmeter provided by an embodiment of the present invention is shown. The secondary amplification module 121 may include a third operational amplifier U3, a fourth operational amplifier U4, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16 and a seventeenth resistor R17, the second input terminal C2 of the secondary amplification module 121 is the positive input terminal of the third operational amplifier U3, and the first input terminal C1 of the secondary amplification module 121 is the positive input terminal of the fourth operational amplifier U4.

[0102] The fifteenth resistor R15 is electrically connected between the negative input terminal of the fourth operational amplifier U4 and the ground. The sixteenth resistor R16 is electrically connected between the negative input terminal of the third operational amplifier U3 and the ground.

[0103] The positive input terminal of the fourth operational amplifier U4 is connected to the sixth resistor R6, one end of the fourteenth resistor R14 is electrically connected between the negative input terminal of the fourth operational amplifier U4 and the fifteenth resistor R15, and the other end of the fourteenth resistor R14 is electrically connected to the output terminal of the fourth operational amplifier U4.

[0104] One end of the seventeenth resistor R17 is electrically connected between the negative input terminal of the third operational amplifier U3 and the sixteenth resistor R16, the other end of the seventeenth resistor R17 is electrically connected to the output terminal of the third operational amplifier U3, the positive input terminal of the third operational amplifier U3 is electrically connected to one end of the eighteenth resistor R18, and the other end of the eighteenth resistor R18 is connected to the output terminal of the first operational amplifier U1 through the nineteenth resistor R19.

[0105] It can be seen that the electromagnetic flowmeter inputs the induced electromotive force signal to the first operational amplifier U1 and the second operational amplifier U2 for the first differential amplification process through the first measuring module 111 and the second measuring module 112, and then inputs the signal after the first differential amplification to the third operational amplifier U3 and the fourth operational amplifier U4 for the second differential amplification process, outputs the differential amplification signal after the second amplification, and generates the flow measurement result according to the differential amplification signal after the second amplification. By amplifying the induced electromotive force signal twice, the generated flow measurement result can be made more accurate, thereby improving the accuracy of the electromagnetic flowmeter.

[0106] In practical applications, electromagnetic flowmeters usually apply a magnetic field to the measured fluid through an excitation coil, and measure the flow rate by detecting the induced electromotive force signal generated by the measured fluid passing through the magnetic field area. In the prior art, most electromagnetic flowmeters use a constant voltage current limiting circuit to drive the excitation coil. If the voltage output by the constant voltage power supply is too low, the time for the excitation coil to reach the preset current will be too long. If the voltage output by the constant voltage power supply is too high, the voltage across the coil is low after the circuit enters the current limiting mode, resulting in energy being mainly consumed in the constant current circuit, which increases the power consumption of the constant current circuit, and thus causes the power consumption of the entire circuit to be too high.

[0107] To solve the problem of high power consumption of the circuit, refer to Fig.10 , Fig.10 Another circuit block diagram of an electromagnetic flowmeter provided in an embodiment of the present invention is shown. The electromagnetic flowmeter also includes an excitation circuit and an excitation coil 250, and the excitation coil 250 is used to generate the magnetic field region. The excitation circuit includes a switching power supply 210, a constant current circuit 220, an H-bridge circuit 230, and a voltage comparison circuit 240; the switching power supply 210 is electrically connected to the constant current circuit 220, the constant current circuit 220 is electrically connected to the H-bridge circuit 230 and the voltage comparison circuit 240, the H-bridge circuit 230 is electrically connected to the excitation coil 110, and the voltage comparison circuit 240 is electrically connected to the switching power supply 210.

[0108] The H-bridge circuit 230 can be used to provide an excitation current for the excitation coil 110, the constant current circuit 220 is used to sample the excitation current provided by the H-bridge circuit 230, obtain a sampling voltage, and adjust the current output to the H-bridge circuit 230 according to the sampling voltage, so that the output current of the constant current circuit 230 is constant, and the voltage comparison circuit 230 is used to adjust the output voltage of the switching power supply 210 according to the sampling voltage. Among them, the switching power supply 210 can be a DC-DC switching power supply, which is not limited here.

[0109] In some embodiments, see Fig.11 , Fig.11The circuit block diagram of the constant current circuit of the electromagnetic flowmeter provided in an embodiment of the present invention is shown. The constant current circuit 220 may include a current limiting circuit 221, a current error amplifier circuit 222, and a current sampling circuit 223. The switching power supply 210 is electrically connected to the current limiting circuit 221, the current limiting circuit 221 is electrically connected to the H-bridge circuit 230, the H-bridge circuit 230 is electrically connected to the current sampling circuit 223, the current sampling circuit 223 is electrically connected to the current error amplifier circuit 222 and the voltage comparison circuit 240, respectively, and the current error amplifier circuit 222 is electrically connected to the current limiting circuit 221.

[0110] The current sampling circuit samples the current output by the H-bridge circuit 230 to obtain a sampling voltage, and inputs the sampling voltage into the current error amplifier circuit 222 and the voltage comparison circuit 230 respectively. The voltage comparison circuit 230 adjusts the output voltage of the switching power supply 210 according to the sampling voltage. The current error amplifier circuit 222 amplifies the sampling voltage and inputs the amplified sampling voltage into the current limiting circuit 221. The current limiting circuit 221 adjusts the output current according to the amplified sampling voltage, thereby providing a constant current for the H-bridge circuit 230.

[0111] See also Fig.12 , Fig.12 The schematic diagram of the voltage output by the switching power supply of the excitation circuit of the electromagnetic flowmeter provided by the embodiment of the present invention and the current output by the constant current circuit is shown. The voltage comparison circuit 240 is used to make the switching power supply output a higher voltage when the sampling voltage is small, and output a lower voltage when the sampling voltage is large, so as to reduce the voltage drop generated on the constant current circuit, and finally achieve the purpose of reducing power consumption.

[0112] In some embodiments, the voltage comparison circuit may be equivalent to the switch of the switching power supply 220. When the sampled voltage is higher than the preset voltage, the voltage comparison circuit outputs a low level, and the switching power supply 210 is adjusted to output at a constant low voltage; when the sampled voltage is lower than the preset voltage, the voltage comparison circuit outputs a high level, and the switching power supply 210 is adjusted to output at a constant high voltage. For example, assuming that the set high voltage is 10v and the set low voltage is 5v, when the sampled voltage is higher than the preset voltage, the voltage comparison circuit outputs a low level, and the switching power supply 210 is adjusted to output at a constant voltage of 5v; when the sampled voltage is lower than the preset voltage, the voltage comparison circuit outputs a high level, and the switching power supply 210 is adjusted to output at a constant voltage of 10v.

[0113] Therefore, the output voltage of the switching power supply can be adjusted according to the sampling voltage through the voltage comparison circuit. When the sampling voltage is higher than the preset voltage, the output voltage of the switching power supply is reduced. When the sampling voltage is lower than the preset voltage, the output voltage of the switching power supply is increased, thereby realizing automatic control of the output voltage of the switching power supply and ensuring that the excitation circuit can quickly reach the set current while reducing the power consumption of the constant current circuit.

[0114] It can be seen that the electromagnetic flowmeter provided in the embodiment of the present invention, by adding a voltage comparison circuit in the excitation circuit, the voltage comparison circuit can control the output voltage of the switching power supply according to the comparison result between the sampled voltage and the preset voltage, thereby preventing the voltage in the excitation circuit from being too high after the excitation circuit enters the constant current mode, thereby effectively avoiding excessive power consumption in the excitation circuit.

[0115] See also Fig.13 , Fig.13 A circuit structure diagram of a voltage comparison circuit of an electromagnetic flowmeter provided in an embodiment of the present invention is shown. The voltage comparison circuit 240 includes a power chip 241 and a voltage feedback circuit 242, the feedback pin FB of the power chip 241 is electrically connected to the output end of the voltage feedback circuit 242, the switch pin SW of the power chip 241 is electrically connected to the switching power supply 210, and the input end of the voltage feedback circuit 242 is electrically connected to the constant current circuit 210.

[0116] In some implementations, the power chip 241 may be a DCDC power chip, which is not limited herein.

[0117] The voltage feedback circuit 242 is used to output a feedback voltage to the feedback pin FB of the power chip 241 according to the comparison result between the sampled voltage and the set voltage. The power chip 241 is used to adjust the output voltage of the switch pin SW according to the feedback voltage, and further adjust the output voltage of the switching power supply 210 through the output voltage of the switch pin SW.

[0118] It should be noted that a voltage comparator is internally connected to the feedback pin FB of the power chip 241. The power chip 241 can compare the voltage of the feedback pin FB with the reference voltage inside the power chip 241, and adjust the switch duty cycle inside the power chip 241 according to the comparison result, so as to adjust the output voltage of the switch pin SW, and then adjust the output voltage of the switching power supply through the output voltage of the switch pin SW.

[0119] See also Fig.14 , Fig.14 Another circuit structure diagram of the voltage comparison circuit of the electromagnetic flowmeter provided by the embodiment of the present invention is shown. The voltage feedback circuit 242 includes a reference power supply 2421, a comparator U5, a field effect transistor Q1, a ninth resistor R9, a tenth resistor R10 and an eleventh resistor R11.

[0120] One end of the ninth resistor R9 and the tenth resistor R10 connected in series is electrically connected between the switch pin SW of the power chip 241 and the switch power supply 210, and the other end of the ninth resistor R9 and the tenth resistor R10 connected in series is grounded; one end of the eleventh resistor R11 is electrically connected between the ninth resistor R9 and the tenth resistor R10, and the other end of the eleventh resistor R11 is electrically connected to the source of the field effect transistor Q1, the gate of the field effect transistor Q1 is electrically connected to the output end of the comparator U5, the drain of the field effect transistor Q1 is grounded, the positive input end of the comparator U5 is electrically connected to the reference power supply 2421, and the negative input end of the comparator U5 is electrically connected to the constant current circuit 220; the feedback pin FB of the power chip 241 is electrically connected between the ninth resistor R9 and the tenth resistor R10. Among them, the reference power supply 2421 outputs a preset voltage V1.

[0121] In some embodiments, the voltage feedback circuit 242 may further include a first capacitor C1, an inductor L1, and a second capacitor C2. One end of the inductor L1 is electrically connected to the switch pin SW of the power chip 241, the other end of the inductor L1 is electrically connected to the switch power supply, one end of the first capacitor C1 is electrically connected to the other end of the inductor L1, and the other end of the first capacitor C1 is grounded. The second capacitor C2 is electrically connected to the compensation pin COMP of the power chip 241.

[0122] When the sampling voltage Is is greater than the preset voltage V1, the comparator U5 outputs a low level, so that the field effect tube Q1 is disconnected, the eleventh resistor R11 is disconnected, and the output voltage of the switch pin SW of the power chip 241 is Wherein, VDD represents the output voltage of the switch pin of the power chip 241, FB represents the feedback voltage output by the voltage feedback circuit 242, R9 represents the resistance value of the ninth resistor, and R10 represents the resistance value of the tenth resistor; when the sampling voltage Is is less than the preset voltage V1, the comparator U5 outputs a high level, so that the field effect tube Q1 is turned on, and the eleventh resistor R11 is grounded through Q1, and the output voltage of the switch pin SW of the power chip 241 is Wherein, VDD represents the output voltage of the switch pin of the power chip 241, FB represents the feedback voltage output by the voltage feedback circuit 242, R represents the resistance of the tenth resistor and the eleventh resistor in parallel, and R9 represents the resistance of the ninth resistor.

[0123] It can be understood that when the sampling voltage Is is greater than the preset voltage V1, the field effect tube Q1 is turned on, so that the feedback voltage output by the voltage feedback circuit 242 becomes smaller, and the switch pin SW of the power chip 241 outputs a low level, and the switching power supply 210 is adjusted to output a constant low voltage; when the sampling voltage Is is less than the preset voltage V1, the field effect tube Q1 is disconnected, so that the feedback voltage output by the voltage feedback circuit 242 becomes larger, and the switch pin SW of the power chip 241 outputs a high level, and the switching power supply 210 is adjusted to output a constant high voltage.

[0124] Based on the above embodiments, the present invention also provides a spraying device, which may include the above electromagnetic flowmeter. The spraying device uses the electromagnetic flowmeter to accurately detect the spraying dosage during the spraying operation, thereby improving the spraying effect.

[0125] In addition, an embodiment of the present invention further provides an unmanned device, which may include a device body and the above-mentioned spraying device disposed on the device body, and the spraying device is mounted on the unmanned device. The unmanned device can spray the external environment, such as plant irrigation, spraying of medicine, etc., by using the unmanned device mounted thereon.

[0126] In some embodiments, the unmanned equipment may be a drone, an unmanned vehicle, etc., such as a plant protection drone, a pesticide spraying vehicle, etc.

[0127] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can still modify the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or perform equivalent replacements on some of the technical features thereof; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. They should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An electromagnetic flowmeter, characterized in that: The electromagnetic flowmeter comprises a first measuring module, a second measuring module, a differential amplifier circuit and a first interference elimination module; the first measuring module and the second measuring module are used to measure the induced electromotive force signal generated by the measured fluid in the pipeline passing through the magnetic field area; The first positive input terminal of the differential amplifier circuit is electrically connected to the first measurement module, and the second positive input terminal of the differential amplifier circuit is electrically connected to the second measurement module; one end of the first interference elimination module is electrically connected to the first negative input terminal of the differential amplifier circuit, and the other end of the first interference elimination module is electrically connected to the second negative input terminal of the differential amplifier circuit through the magnetic field region; The differential amplifier circuit is used to perform differential amplification processing according to the induced electromotive force signals input by the first measurement module and the second measurement module, and output a differential amplified signal; the differential amplified signal is used to generate a flow measurement result; The first interference elimination module is used to eliminate the magnetic field interference between the first negative input terminal and the second negative input terminal of the differential amplifier circuit.

2. The electromagnetic flowmeter according to claim 1, characterized in that: The first interference elimination module includes a first connecting line, a second connecting line, a first transformer and a second transformer; The first transformer is electrically connected to a first negative input terminal of the differential amplifier circuit, the second transformer is electrically connected to a second negative input terminal of the differential amplifier circuit, the first connecting wire and the second connecting wire are connected between the first transformer and the second transformer, and the first connecting wire and the second connecting wire are arranged in the magnetic field region; wherein the induced electromotive forces on the first connecting wire and the second connecting wire are equal in magnitude and opposite in direction.

3. The electromagnetic flowmeter according to claim 2, characterized in that: The first interference elimination module also includes a first resistor, a second resistor, a third resistor and a fourth resistor; One end of the first resistor is electrically connected to the opposite-name end of the first winding of the first transformer, and the other end of the first resistor is electrically connected to the first negative input end of the differential amplifier circuit; one end of the second resistor is electrically connected to the same-name end of the first winding of the second transformer, and the other end of the second resistor is electrically connected to the second negative input end of the differential amplifier circuit; one end of the third resistor is electrically connected to the same-name end of the second winding of the first transformer, and the other end of the third resistor is grounded; one end of the fourth resistor is electrically connected to the opposite-name end of the second winding of the second transformer, and the other end of the fourth resistor is grounded; The first connecting line is connected between the same-name end of the first winding of the first transformer and the opposite-name end of the first winding of the second transformer, and the second connecting line is connected between the opposite-name end of the second winding of the first transformer and the same-name end of the second winding of the second transformer.

4. The electromagnetic flowmeter according to claim 3, characterized in that: The differential amplifier circuit includes a first operational amplifier and a second operational amplifier; The negative input terminal of the first operational amplifier is electrically connected to the opposite-name terminal of the first winding of the first transformer through the first resistor, and the positive input terminal of the first operational amplifier is electrically connected to the first measurement module; The negative input terminal of the second operational amplifier is electrically connected to the same-name terminal of the first winding of the second transformer through the second resistor, and the positive input terminal of the second operational amplifier is electrically connected to the second measuring module.

5. The electromagnetic flowmeter according to claim 4, characterized in that: The differential amplifier circuit further includes a secondary amplifier module and a second interference elimination module, one end of the second interference elimination module is electrically connected to the first input end of the secondary amplifier module, the other end of the second interference elimination module is electrically connected to the output end of the second operational amplifier through the magnetic field region, and the second input end of the secondary amplifier module is electrically connected to the output end of the first operational amplifier; The second interference elimination module is used to eliminate the magnetic field interference between the output end of the second operational amplifier and the first input end of the secondary amplification module.

6. The electromagnetic flowmeter according to claim 5, characterized in that: The second interference elimination module includes a third connecting line, a fourth connecting line and a third transformer; The third transformer is electrically connected to the first input end of the secondary amplification module, the third connecting line is connected between the third transformer and the output end of the second operational amplifier, one end of the fourth connecting line is electrically connected to the third transformer, and the other end of the fourth connecting line is grounded; the third connecting line and the fourth connecting line are arranged in the magnetic field region; wherein the induced electromotive forces on the third connecting line and the fourth connecting line are equal in magnitude and opposite in direction.

7. The electromagnetic flowmeter according to claim 6, characterized in that: The second interference elimination module further includes a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor; One end of the fifth resistor is electrically connected to the output end of the second operational amplifier, and the other end of the fifth resistor is electrically connected to the same-name end of the first winding of the third transformer through the third connecting line; the sixth resistor is electrically connected between the opposite-name end of the first winding of the third transformer and the first input end of the secondary amplification module; One end of the seventh resistor is electrically connected to the opposite-name end of the second winding of the third transformer through the fourth connecting line, and the other end of the seventh resistor is grounded; one end of the eighth resistor is electrically connected to the same-name end of the second winding of the third transformer, and the other end of the eighth resistor is grounded.

8. The electromagnetic flowmeter according to claim 1, characterized in that: The electromagnetic flowmeter further comprises an excitation circuit and an excitation coil, wherein the excitation circuit comprises a switching power supply, a constant current circuit, an H-bridge circuit and a voltage comparison circuit; the switching power supply is electrically connected to the constant current circuit, the constant current circuit is electrically connected to the H-bridge circuit and the voltage comparison circuit, the H-bridge circuit is electrically connected to the excitation coil, and the voltage comparison circuit is electrically connected to the switching power supply; the excitation coil is used to generate the magnetic field region; The H-bridge circuit is used to provide an excitation current for the excitation coil; The constant current circuit is used to sample the excitation current provided by the H-bridge circuit to obtain a sampling voltage, and adjust the current output to the H-bridge circuit according to the sampling voltage so that the output current of the constant current circuit is constant; The voltage comparison circuit is used to adjust the output voltage of the switching power supply according to the sampled voltage.

9. The electromagnetic flowmeter according to claim 8, characterized in that: The voltage comparison circuit includes a power chip and a voltage feedback circuit, wherein a feedback pin of the power chip is electrically connected to an output end of the voltage feedback circuit, and a switch pin of the power chip is electrically connected to the switch power supply; an input end of the voltage feedback circuit is electrically connected to the constant current circuit; The voltage feedback circuit is used to output a feedback voltage to a feedback pin of the power chip according to a comparison result between the sampled voltage and the set voltage; The power chip is used to adjust the output voltage of the switch pin according to the feedback voltage, and further adjust the output voltage of the switching power supply through the output voltage of the switch pin.

10. The electromagnetic flowmeter according to claim 9, characterized in that: The voltage feedback circuit includes a reference power supply, a comparator, a field effect transistor, a ninth resistor, a tenth resistor and an eleventh resistor; One end of the ninth resistor and the tenth resistor connected in series is electrically connected between the switch pin of the power chip and the switching power supply, and the other end of the ninth resistor and the tenth resistor connected in series is grounded; one end of the eleventh resistor is electrically connected between the ninth resistor and the tenth resistor, the other end of the eleventh resistor is electrically connected to the source of the field effect tube, the gate of the field effect tube is electrically connected to the output end of the comparator, and the drain of the field effect tube is grounded; The positive input terminal of the comparator is electrically connected to the reference power supply, and the negative input terminal of the comparator is electrically connected to the constant current circuit; the feedback pin of the power chip is electrically connected between the ninth resistor and the tenth resistor.

11. A spraying device, characterized in that: The electromagnetic flowmeter comprises the electromagnetic flowmeter described in any one of claims 1-10.

12. An unmanned device, characterized in that: A spray device comprising the spray device of claim 11.

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