Large-caliber electromagnetic water meter constant current source control circuit and method

Abstract

The invention is suitable for the technical field of electromagnetic water meters, and relates to a large-caliber electromagnetic water meter constant current source control circuit and method, and the circuit 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 source power supply module, the excitation conversion module, the constant current control module, the excitation coil and the excitation coil voltage detection module are in communication connection in sequence, and the MCU main control module is in communication connection with the excitation source power supply module, the excitation conversion module, the digital potentiometer control module and the excitation coil terminal voltage detection module. And the constant current control module is in communication connection with the digital potentiometer control module. The large-diameter electromagnetic water meter is simple in structure and convenient to operate, and the stability and accuracy of long-term working of the large-diameter electromagnetic water meter are effectively guaranteed.

Description

Technical Field

[0001] The 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-caliber electromagnetic water meters generally work in humid or even water-soaked environments. Humid environments can easily cause aging of the excitation coil inside the electromagnetic water meter, resulting in fundamental changes in the induced electromotive force generated by the same excitation current before and after aging, which directly affects the accuracy of measurement. 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. When driven by this excitation current, the induced electromotive force of large-caliber electromagnetic water meters is only tens of microvolts, and the signal is particularly small. After aging of the excitation coil, the induced electromotive force is even smaller, and the noise does not decrease. The metering signal cannot be detected after conditioning, resulting in inaccurate measurement or even no measurement.

[0003] The patent with announcement number CN113566911B provides an excitation control method, device and storage medium for an electromagnetic water meter. The electromagnetic water meter is provided with a coil, and the control method includes inputting excitation currents of different excitation cycles to the coil, and collecting the induced voltage signal generated when the coil inputs the current 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, and comparing the water flow rates of 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 that the aging of the excitation coil affects 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 personnel in this technical field. Summary of the invention

[0005] In view of the deficiencies in the prior art, 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 prior art that the stability and accuracy of the electromagnetic water meter 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 large-caliber electromagnetic water meter constant current source control circuit, comprising:

[0008] 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.

[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 tube V2, a MOS tube V3, a MOS tube V4, a MOS tube V5, a switch L1 and a switch L2, one end of the switch L1 is connected to the third pin of the MOS tube V2 and the third pin of the MOS tube 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 tube V3 and the third pin of the MOS tube 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 tube V2 is connected to the second pin of the MOS tube V3, and the second pin of the MOS tube V4 is connected to the second pin of the MOS tube 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 transistor V9, transistor V10, transistor V11 and 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 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 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 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 the power consumption, the excitation current is generally between 15 mA and 20 mA. When the large-caliber electromagnetic water meter is driven by the excitation current, the induced electromotive force 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. The metering signal cannot be detected after conditioning, resulting in inaccurate metering or even no metering. The present invention has a simple structure and convenient operation. According to the law of conservation of energy and the principle that the energy consumed by the excitation coil itself and the sum of the converted magnetic energy remain unchanged, the excitation current is adaptively adjusted. When the signal is detected to be in a very 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 the aging of the coil, so that the flow rate is still normal after the excitation coil ages, and the stability and accuracy of the long-term operation of the electromagnetic water meter are improved. 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 module 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 A flow chart of a method for controlling a constant current source of a large-caliber electromagnetic water meter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field of the present invention; the terms used in this specification are only for the purpose of describing specific embodiments 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 drawings, which are only for the convenience of description and should not be understood as limitations on the present technical solution.

[0030] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions; the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order. In the specification and claims of the present invention and the above-mentioned drawings, when an element is referred to as being "fixed to" or "mounted on" or "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] In addition, reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood 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 applied 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 in conjunction with the accompanying drawings.

[0036] The present invention provides a constant current source control circuit for a large-caliber electromagnetic water meter, which is applied to solve the problem of inaccurate measurement caused by long-term operation of a large-caliber electromagnetic water meter. 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 increases. Under the condition of the same excitation current, the voltage difference consumed on 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 the 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 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, the constant current control module is communicatively 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 a voltage-controlled flow method, and is responsible for providing a 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 the present embodiment, the circuit of the excitation conversion module includes a MOS tube V2, a MOS tube V3, a MOS tube V4, a MOS tube V5, a switch L1 and a switch L2, one end of the switch L1 is connected to the third pin of the MOS tube V2 and the third pin of the MOS tube 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 tube V3 and the third pin of the MOS tube 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 tube V2 is connected to the second pin of the MOS tube V3, and the second pin of the MOS tube V4 is connected to the second pin of the MOS tube V5.

[0046] Specifically, MOS tube V2, MOS tube V3, MOS tube V4, and MOS tube V5 form an H-bridge circuit, which is controlled by the main control MCU. Among them, MOS tube V4 and MOS tube V3 are a pair and are switched at the same time, and MOS tube V5 and MOS tube V2 are also the same. Switch L1 and switch L2 are connected to the excitation coil. When working, the current first flows from MOS tube V4 to switch L1, passes through the excitation coil to switch L2, and then to MOS tube V3 to form a path, and then periodically switches to the current from MOS tube V5 to switch L2, flows through the excitation coil to switch L1, and then to MOS tube V2, thereby realizing the 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, and chip U1 is a voltage regulator. The voltage regulator is divided by resistors R1 and R2, where resistors R1 and R2 are high-precision resistors. The stable voltage formed by the control 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 value of the current of the constant current source is about 15mA.

[0049] Furthermore, in this embodiment, 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.

[0050] Specifically, chip U3 uses a digital potentiometer chip, an I2C interface, a 10-bit resolution, a maximum resistance of 1K, and 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 transistor V9, transistor V10, transistor V11 and 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, the voltage across the excitation coil, switch L1, and the voltage of switch L2 are converted to the ADC inside the main control MCU through resistor divider, and the main control MCU processes it.

[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 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, the large-caliber electromagnetic water meter is basically powered by a battery, and the constant current source is basically a specific value. Generally, considering the power consumption, the excitation current is generally 15 mA to 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. The induced electromotive force is smaller after the excitation coil ages, and the noise does not decrease. The metering signal cannot be detected after conditioning, resulting in inaccurate metering or even no metering. The present invention has a simple structure and convenient operation. According to the law of conservation of energy and the principle that the energy consumed by the excitation coil itself and the sum of the converted magnetic energy remain unchanged, the excitation current is adaptively adjusted. When the signal is detected to be in a very 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 under the same flow rate will not be missed or ignored due to the aging of the coil, so that the flow rate is still normal after the excitation coil ages, and the stability and accuracy of the long-term operation of the electromagnetic water meter are improved.

[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 shown 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 recorded in the aforementioned specific embodiments, or to perform equivalent replacements for some of the technical features therein. Any equivalent structure made using the contents of the specification and drawings of the present invention, 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.

2. A constant current source control circuit for a large-caliber electromagnetic water meter 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: The circuit of the excitation conversion module includes a MOS tube V2, a MOS tube V3, a MOS tube V4, a MOS tube V5, a switch L1 and a switch L2. One end of the switch L1 is connected to the third pin of the MOS tube V2 and the third pin of the MOS tube V4 respectively, and 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 tube V3 and the third pin of the MOS tube V5 respectively, and the other end of the switch L2 is connected to the second pin of the excitation coil. The second pin of the MOS tube V2 is connected to the second pin of the MOS tube V3, and the second pin of the MOS tube V4 is connected to the second pin of the MOS tube 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, 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.

6. A constant current source control circuit for a large-caliber electromagnetic water meter according to claim 3, characterized in that: The circuit of the excitation coil voltage detection module includes transistor V9, transistor V10, transistor V11 and 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.

7. A method applied to the circuit according to any one of claims 1 to 6, characterized in that: The following steps are involved: S10, the MCU main control module periodically controls the excitation power supply module to turn on the power, and 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 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 The current that needs to be adjusted is determined, and the process returns to step S10.

8. The method according to claim 7, characterized in that In step S40, the constant current is initially 15 mA.

Images