Large aperture electromagnetic water meter constant current source control circuit and method

Abstract

The application is suitable for the technical field of electromagnetic water meter, and relates to a large-diameter electromagnetic water meter constant current source control circuit and method, which comprises: an excitation power supply module, an excitation conversion module, a constant current control module, an excitation coil, an excitation coil voltage detection module, a digital potentiometer control module and an MCU main control module; the excitation power supply module, the excitation conversion module, the constant current control module, the excitation coil and the excitation coil voltage detection module are sequentially connected in communication, the MCU main control module is connected in communication with the excitation power supply module, the excitation conversion module, the digital potentiometer control module and the excitation coil end voltage detection module respectively, and the constant current control module is connected in communication with the digital potentiometer control module. The application has simple structure and convenient operation, and effectively guarantees the stability and accuracy of long-term work of the large-diameter electromagnetic water meter.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic water meters, and in particular relates to a constant current source control circuit and method for a large-caliber electromagnetic water meter. Background Art

[0002] Large-diameter electromagnetic water meters typically operate in humid or even submerged environments. Humid environments can easily cause the excitation coil inside the electromagnetic water meter to age, leading to fundamental changes in the induced electromotive force generated by the same excitation current before and after aging, directly affecting the accuracy of measurement. Large-diameter electromagnetic water meters are generally battery-powered, and the constant current source is basically a specific value. Generally, considering power consumption, the excitation current is generally between 15 mA and 20 mA. However, when driven by this excitation current, the induced electromotive force of large-diameter electromagnetic water meters is only tens of microvolts, and the signal is extremely small. After the excitation coil ages, the induced electromotive force is even smaller, and the noise does not decrease. After conditioning, the metering signal still cannot be detected, resulting in inaccurate measurement or even no measurement.

[0003] Patent publication number CN113566911B provides an excitation control method, device, and storage medium for an electromagnetic water meter. The electromagnetic water meter is equipped with a coil. The control method includes inputting excitation currents of different excitation cycles into the coil and collecting the induced voltage signal generated by the input current to the coil in real time; calculating the water flow rate corresponding to the electromagnetic water meter under multiple different excitation cycles based on the collected induced voltage signal, comparing the water flow rates of the multiple different excitation cycles, and switching to the corresponding excitation cycle based on the comparison results. Although this patent involves a control method for an electromagnetic water meter, its purpose is to reduce power consumption. It does not provide a relevant technical solution for how to overcome the defect of aging of the excitation coil affecting the measurement accuracy of the electromagnetic water meter.

[0004] Therefore, how to ensure the long-term stability and accuracy of large-caliber electromagnetic water meters is an urgent problem to be solved by people in this technical field. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a constant current source control circuit for a large-caliber electromagnetic water meter to solve the problem in the existing technology that the stability and accuracy of electromagnetic water meters cannot be guaranteed during long-term operation; in addition, the present invention also provides a constant current source control method for a large-caliber electromagnetic water meter.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a constant current source control circuit for a large-caliber electromagnetic water meter, comprising:

[0008] Excitation power supply module, excitation conversion module, constant current control module, excitation coil, excitation coil voltage detection module, digital potentiometer control module and MCU main control module; the excitation power supply module, excitation conversion module, constant current control module, excitation coil, excitation coil voltage detection module are communicatively connected in sequence, the MCU main control module is communicatively connected with the excitation power supply module, excitation conversion module, digital potentiometer control module, and excitation coil voltage detection module respectively, and the constant current control module is communicatively connected with the digital potentiometer control module.

[0009] Furthermore, the circuit of the excitation power supply module includes a chip U4, and the MCU main control module is connected to the fourth pin of the chip U4 to control the on and off of the power supply.

[0010] Furthermore, the circuit of the excitation conversion module includes a MOS transistor V2, a MOS transistor V3, a MOS transistor V4, a MOS transistor V5, a switch L1, and a switch L2. One end of the switch L1 is connected to the third pin of the MOS transistor V2 and the third pin of the MOS transistor V4, respectively. The other end of the switch L1 is connected to the first pin of the excitation coil. One end of the switch L2 is connected to the third pin of the MOS transistor V3 and the third pin of the MOS transistor V5, respectively. The other end of the switch L2 is connected to the second pin of the excitation coil. The second pin of the MOS transistor V2 is connected to the second pin of the MOS transistor V3. The second pin of the MOS transistor V4 is connected to the second pin of the MOS transistor V5.

[0011] Furthermore, the circuit of the constant current control module includes a chip U1, an amplifier U2, a resistor R1, a resistor R2 and a MOS tube V1. The 8th pin of the chip U1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to one end of the resistor R2 and the 3rd pin of the amplifier U2, respectively. The 4th pin of the amplifier U2 is connected to the 2nd pin of the MOS tube V1, and the 1st pin of the amplifier U2 is connected to the 1st pin of the MOS tube V1.

[0012] Furthermore, the circuit of the digital potentiometer module includes a chip U3, and the sixth pin of the chip U3 is connected to the fourth pin of the amplifier U2 and is also connected to the second pin of the MOS tube V1.

[0013] Furthermore, the circuit of the excitation coil voltage detection module includes a transistor V9, a transistor V10, a transistor V11 and a transistor V12, the third pin of the transistor V9 is connected to the first pin of the transistor V10, the switch L1 is connected to the second pin of the transistor V10, the third pin of the transistor V11 is connected to the first pin of the transistor V12, and the switch L2 is connected to the second pin of the transistor V12.

[0014] In a second aspect, the present invention further provides a method for controlling a constant current source of a large-caliber electromagnetic water meter, comprising the following steps:

[0015] S10, the MCU main control module periodically controls the excitation power supply module to turn on the power, and then enters step S20;

[0016] S20, the MCU main control module controls the excitation conversion module to form a periodic positive and negative switching voltage signal, and then enters step S30;

[0017] S30, the MCU main control module controls the digital potentiometer module through the I2C interface, and enters step S40;

[0018] S40, the constant current control module performs constant voltage control according to the resistance of the digital potentiometer module to obtain a constant current;

[0019] S50, the excitation coil starts working, the MCU main control module collects the voltage at both ends of the excitation coil, calculates the voltage difference on the excitation coil, and calculates the voltage difference according to the excitation coil. The current that needs to be adjusted is determined, and the process returns to step S10.

[0020] Furthermore, in step S40, the constant current is initially 15 mA.

[0021] Compared with the prior art, the large-caliber electromagnetic water meter constant current source control circuit and method provided by the present invention have at least the following beneficial effects:

[0022] In the prior art, large-caliber electromagnetic water meters are basically powered by batteries, and the constant current source is basically a specific value. Generally, considering power consumption, the excitation current is generally between 15 mA and 20 mA. When driven by this excitation current, the induced electromotive force of the large-caliber electromagnetic water meter is only tens of microvolts, and the signal is particularly small. After the excitation coil ages, the induced electromotive force is even smaller, and the noise does not decrease. After conditioning, the metering signal still cannot be detected, resulting in inaccurate metering or even no metering. The present invention has a simple structure and is easy to operate. According to the law of conservation of energy and the principle that the sum of the energy consumed by the excitation coil and the energy converted into magnetic energy remains unchanged, the excitation current is adaptively adjusted. When the signal is detected to be in an extremely small range, the excitation current is adaptively increased so that the extremely weak signal can be detected and the magnetic field remains stable. The induced electromotive force generated will not be missed or ignored under the same flow rate due to coil aging, thereby achieving the purpose of normal flow rate after the excitation coil ages, and improving the stability and accuracy of the electromagnetic water meter in long-term operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the scheme of the present invention, a brief introduction is given below to the figures required for use in the description of the embodiments. Obviously, the figures described below are some embodiments of the present invention. For ordinary technicians in this field, other figures can be obtained based on these figures without paying any creative work.

[0024] Figure 1 A block diagram of a constant current source control circuit for a large-caliber electromagnetic water meter provided by an embodiment of the present invention;

[0025] Figure 2 A partial circuit diagram of a constant current source control circuit for a large-caliber electromagnetic water meter provided by an embodiment of the present invention;

[0026] Figure 3 A circuit diagram of an excitation power supply module in a constant current source control circuit of a large-caliber electromagnetic water meter provided by an embodiment of the present invention;

[0027] Figure 4 A circuit diagram of an excitation coil voltage detection module in a constant current source control circuit of a large-caliber electromagnetic water meter provided by an embodiment of the present invention;

[0028] Figure 5 This is a flow chart of a method for controlling a constant current source of a large-caliber electromagnetic water meter provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the present invention pertains; the terms used in the specification herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention; for example, the directions or positions indicated by the terms "length", "width", "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the accompanying drawings and are for ease of description only and should not be construed as limiting the present technical solution.

[0030] The terms "including" and "having," as well as any variations thereof, in the specification and claims of the present invention and the accompanying drawings are intended to cover non-exclusive inclusions; the terms "first," "second," and the like in the specification and claims of the present invention and the accompanying drawings are used to distinguish between different objects, rather than to describe a specific order. In the specification and claims of the present invention and the accompanying drawings, when an element is referred to as being "fixed to," "mounted on," "disposed on," or "connected to" another element, it may be directly or indirectly located on the other element. For example, when an element is referred to as being "connected to" another element, it may be directly or indirectly connected to the other element.

[0031] Furthermore, references herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0032] The present invention provides a constant current source control circuit for a large-caliber electromagnetic water meter, which is used to solve the problem of inaccurate measurement caused by long-term operation of a large-caliber electromagnetic water meter. The constant current source control circuit for a large-caliber electromagnetic water meter includes:

[0033] Excitation power supply module, excitation conversion module, constant current control module, excitation coil, excitation coil terminal voltage detection module, digital potentiometer control module and MCU main control module; the excitation power supply module, excitation conversion module, constant current control module, excitation coil, excitation coil terminal voltage detection module are communicatively connected in sequence, the MCU main control module is communicatively connected with the excitation power supply module, excitation conversion module, digital potentiometer control module, and excitation coil terminal voltage detection module respectively, and the constant current control module is communicatively connected with the digital potentiometer control module.

[0034] The present invention has a simple structure and is easy to operate, and effectively ensures the long-term working stability and accuracy of a large-caliber electromagnetic water meter.

[0035] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0036] The present invention provides a constant current source control circuit for a large-caliber electromagnetic water meter, which is used to solve the problem of inaccurate measurement caused by long-term operation of large-caliber electromagnetic water meters. The principle of the embodiment of the present invention is based on the principle of conservation of energy. As the excitation coil ages or oxidizes, the internal resistance will increase. Under the condition of the same excitation current, the voltage difference consumed by the internal resistance of the excitation coil increases, and the converted magnetic energy decreases.

[0037] Specifically, the excitation supply voltage U is constant, and the voltage difference of the excitation coil I1 under the constant excitation current before aging is △U1, so the energy converted into magnetic energy is Q1=(U-△U1)I1;

[0038] The supply voltage U is constant after aging, and the voltage difference of the excitation coil I2 under constant excitation current before aging is △U2, so the energy that can be converted into magnetic energy is Q2=(U-△U2)I2;

[0039] To maintain the stability of flow, Q1=Q2 is required;

[0040] Therefore, the internal resistance of the excitation coil becomes larger after aging, △U2 becomes larger, and I2 becomes larger. This is the principle of adaptive regulation.

[0041] like Figure 1 As shown, in this embodiment, the large-caliber electromagnetic water meter constant current source control circuit includes:

[0042] Excitation power supply module, excitation conversion module, constant current control module, excitation coil, excitation coil end voltage detection module, digital potentiometer control module and MCU main control module; the excitation power supply module, excitation conversion module, constant current control module, excitation coil, excitation coil end voltage detection module are communicated and connected in sequence, the MCU main control module is communicated and connected with the excitation power supply module, excitation conversion module, digital potentiometer control module, excitation coil end voltage detection module respectively, the constant current control module is communicated and connected with the digital potentiometer control module, the excitation power supply module is responsible for supplying power to the excitation conversion module, the excitation conversion module is responsible for forming a periodic positive and negative switching voltage signal, the constant current control module adopts the voltage-controlled flow method, and is responsible for providing stable current, the excitation coil voltage detection module is responsible for converting the voltage into a signal that can be collected by the MCU, and the MCU main control module is responsible for controlling and calling each module.

[0043] Furthermore, in this embodiment, the circuit of the excitation power supply module includes a chip U4, and the MCU main control module is connected to the fourth pin of the chip U4 to control the on and off of the power supply.

[0044] Specifically, the circuit of the excitation power supply module adopts a boost circuit, in which EVCC is the excitation voltage, and the main control MCU controls the on and off of the power supply by controlling EN.

[0045] Furthermore, in this embodiment, the circuit of the excitation conversion module includes a MOS transistor V2, a MOS transistor V3, a MOS transistor V4, a MOS transistor V5, a switch L1, and a switch L2. One end of the switch L1 is connected to the third pin of the MOS transistor V2 and the third pin of the MOS transistor V4, respectively. The other end of the switch L1 is connected to the first pin of the excitation coil. One end of the switch L2 is connected to the third pin of the MOS transistor V3 and the third pin of the MOS transistor V5, respectively. The other end of the switch L2 is connected to the second pin of the excitation coil. The second pin of the MOS transistor V2 is connected to the second pin of the MOS transistor V3. The second pin of the MOS transistor V4 is connected to the second pin of the MOS transistor V5.

[0046] Specifically, MOS transistors V2, V3, V4, and V5 form an H-bridge circuit, which is controlled on and off by the main control MCU. MOS transistors V4 and V3 form a pair and are switched on and off simultaneously, as are MOS transistors V5 and V2. Switches L1 and L2 are connected to the excitation coil. During operation, current first flows from MOS transistor V4 to switch L1, passes through the excitation coil to switch L2, and then to MOS transistor V3 to form a path. The current then periodically switches to flow from MOS transistor V5 to switch L2, passes through the excitation coil to switch L1, and then to MOS transistor V2, thereby achieving forward and reverse excitation conversion of the coil.

[0047] Furthermore, in this embodiment, the circuit of the constant current control module includes a chip U1, an amplifier U2, a resistor R1, a resistor R2 and a MOS tube V1. The 8th pin of the chip U1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to one end of the resistor R2 and the 3rd pin of the amplifier U2, respectively. The 4th pin of the amplifier U2 is connected to the 2nd pin of the MOS tube V1, and the 1st pin of the amplifier U2 is connected to the 1st pin of the MOS tube V1.

[0048] Specifically, the constant current control module forms a stable voltage by chip U1. Chip U1 is a voltage regulator. The voltage regulator is divided by resistors R1 and R2. Resistors R1 and R2 are high-precision resistors. The stable voltage formed is assumed to be U'. The resistor R' of the voltage-controlled current amplifier U2, MOS tube V1 and digital potentiometer control module is assumed to form a constant current. The current of the constant current source is I'=U' / R'. Generally, considering the power consumption, the initial current value of the constant current source is about 15mA.

[0049] Furthermore, in this embodiment, the circuit of the digital potentiometer module includes a chip U3 , wherein the sixth pin of the chip U3 is connected to the fourth pin of the amplifier U2 and is also connected to the second pin of the MOS tube V1 .

[0050] Specifically, chip U3 uses a digital potentiometer chip, an I2C interface, a 10-bit resolution, and a maximum resistance of 1K. The resistance can be adjusted to 1K / 1024=0.9766 ohms, which can be precisely adjusted.

[0051] Furthermore, in this embodiment, the circuit of the excitation coil voltage detection module includes a transistor V9, a transistor V10, a transistor V11 and a transistor V12, the third pin of the transistor V9 is connected to the first pin of the transistor V10, the switch L1 is connected to the second pin of the transistor V10, the third pin of the transistor V11 is connected to the first pin of the transistor V12, and the switch L2 is connected to the second pin of the transistor V12.

[0052] Specifically, the MCU main control module controls L-EN, transistors V9, V10, V11, and V12 are turned on, and the voltages at both ends of the excitation coil, switch L1, and switch L2 are converted to the ADC inside the main control MCU through resistor divider, and then processed by the main control MCU.

[0053] The present invention also provides a method applied to the above circuit, such as Figure 5 As shown, in this embodiment, the method includes the following steps:

[0054] S10, the MCU main control module periodically controls the excitation power supply module to turn on the power, and enters step S20

[0055] S20, the MCU main control module controls the excitation conversion module to form a periodic positive and negative switching voltage signal, and enters step S30,

[0056] S30, the MCU main control module controls the digital potentiometer module through the I2C interface, and enters step S40;

[0057] S40, the constant current control module performs constant voltage control according to the resistance of the digital potentiometer module to obtain a constant current, and the initial constant current is 15mA;

[0058] S50, the excitation coil starts working, the MCU main control module collects the voltage at both ends of the excitation coil, calculates the voltage difference on the excitation coil, and calculates the voltage difference according to the excitation coil. The current that needs to be adjusted is determined, and the process returns to step S10.

[0059] The large-caliber electromagnetic water meter constant current source control circuit and method described in the above embodiment are compared with the prior art. In the prior art, large-caliber electromagnetic water meters are basically battery-powered, and the constant current source is basically a specific value. Generally, considering power consumption, the excitation current is generally between 15 mA and 20 mA. Under the drive of the excitation current, the induced electromotive force of the large-caliber electromagnetic water meter is only tens of microvolts, and the signal is particularly small. After the excitation coil ages, the induced electromotive force is even smaller, and the noise does not decrease. After conditioning, the metering signal cannot be detected, resulting in inaccurate measurement or even no measurement. The present invention has a simple structure and convenient operation. According to the law of conservation of energy and the principle that the sum of the energy consumed by the excitation coil and the converted magnetic energy remains unchanged, the excitation current is adaptively adjusted. When the signal is detected to be in an extremely small range, the excitation current is adaptively increased to allow the extremely weak signal to be detected and the magnetic field to remain stable. As a result, the induced electromotive force generated will not be missed or ignored under the same flow rate due to coil aging, achieving the purpose of maintaining normal flow rate after excitation coil aging, thereby improving the long-term stability and accuracy of the electromagnetic water meter.

[0060] Obviously, the embodiments described above are only preferred embodiments of the present invention, rather than all embodiments. The preferred embodiments of the present invention are given in the accompanying drawings, but they do not limit the patent scope of the present invention. The present invention can be implemented in many different forms. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. Although the present invention has been described in detail with reference to the aforementioned embodiments, for those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned specific embodiments, or to make equivalent replacements for some of the technical features therein. Any equivalent structure made using the contents of the present invention specification and drawings, directly or indirectly used in other related technical fields, is also within the scope of patent protection of the present invention.

Claims

1. A constant current source control circuit for a large-caliber electromagnetic water meter, characterized in that: include: An excitation power supply module, an excitation conversion module, a constant current control module, an excitation coil, an excitation coil voltage detection module, a digital potentiometer control module and an MCU main control module; the excitation power supply module, the excitation conversion module, the constant current control module, the excitation coil and the excitation coil voltage detection module are communicatively connected in sequence, the MCU main control module is communicatively connected with the excitation power supply module, the excitation conversion module, the digital potentiometer control module and the excitation coil voltage detection module respectively, and the constant current control module is communicatively connected with the digital potentiometer control module; the circuit of the excitation conversion module includes MOS transistors V2, V3, V4, V5, switches L1 and L2; the circuit of the excitation coil voltage detection module includes transistors V9, V10, V11 and V12; The control method of the large-caliber electromagnetic water meter constant current source control circuit comprises the following steps: S10, the MCU main control module periodically controls the excitation power supply module to turn on the power, and then enters step S20; S20, the MCU main control module controls the excitation conversion module to form a periodic positive and negative switching voltage signal, and then enters step S30; S30, the MCU main control module controls the digital potentiometer module through the I2C interface, and enters step S40; S40, the constant current control module performs constant voltage control according to the resistance of the digital potentiometer module to obtain a constant current; S50, the excitation coil starts working, the MCU main control module collects the voltage at both ends of the excitation coil, calculates the voltage difference on the excitation coil, and calculates the voltage difference according to the excitation coil. Determine the current that needs to be adjusted, and return to step S10; In step S50, the excitation supply voltage U is constant, and the voltage difference of the excitation coil I1 under the constant excitation current before aging is △U1, so the energy converted into magnetic energy is Q1=(U-△U1)I1; the supply voltage U is constant after aging, and the voltage difference of the excitation coil I2 under the constant excitation current before aging is △U2, so the energy that can be converted into magnetic energy is Q2=(U-△U2)I2; in order to maintain the stability of the flow, Q1=Q2 is required.

2. A large-caliber electromagnetic water meter constant current source control circuit according to claim 1, characterized in that: The circuit of the excitation power supply module includes a chip U4, and the MCU main control module is connected to the fourth pin of the chip U4 to control the on and off of the power supply.

3. A constant current source control circuit for a large-caliber electromagnetic water meter according to claim 1, characterized in that: One end of the switch L1 is connected to the third pin of the MOS transistor V2 and the third pin of the MOS transistor V4, respectively. The other end of the switch L1 is connected to the first pin of the excitation coil. One end of the switch L2 is connected to the third pin of the MOS transistor V3 and the third pin of the MOS transistor V5, respectively. The other end of the switch L2 is connected to the second pin of the excitation coil. The second pin of the MOS transistor V2 is connected to the second pin of the MOS transistor V3. The second pin of the MOS transistor V4 is connected to the second pin of the MOS transistor V5.

4. A constant current source control circuit for a large-caliber electromagnetic water meter according to claim 1, characterized in that: The circuit of the constant current control module includes a chip U1, an amplifier U2, a resistor R1, a resistor R2 and a MOS tube V1. The 8th pin of the chip U1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to one end of the resistor R2 and the 3rd pin of the amplifier U2, respectively. The 4th pin of the amplifier U2 is connected to the 2nd pin of the MOS tube V1, and the 1st pin of the amplifier U2 is connected to the 1st pin of the MOS tube V1.

5. A constant current source control circuit for a large-caliber electromagnetic water meter according to claim 4, characterized in that: The circuit of the digital potentiometer module includes a chip U3 , wherein the sixth pin of the chip U3 is connected to the fourth pin of the amplifier U2 and is also connected to the second pin of the MOS tube V1 .

6. A constant current source control circuit for a large-caliber electromagnetic water meter according to claim 3, characterized in that: The third pin of the transistor V9 is connected to the first pin of the transistor V10, the switch L1 is connected to the second pin of the transistor V10, the third pin of the transistor V11 is connected to the first pin of the transistor V12, and the switch L2 is connected to the second pin of the transistor V12.

7. A constant current source control circuit for a large-caliber electromagnetic water meter according to claim 1, characterized in that: In step S40 , the constant current is initially 15 mA.

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