阅读说明：本技术 一种低电压可调励磁电流的电磁流量计转换器 (Low-voltage adjustable exciting current electromagnetic flowmeter converter ) 是由 张兆兆 朱帅意 于 2020-05-26 设计创作，主要内容包括：本发明公开了一种低电压可调励磁电流的电磁流量计转换器,涉及电磁流量计的技术领域,包括CPU、励磁模块、恒流源模块和电源模块,CPU通过输出PWM的脉宽控制恒流源模块输出不同的励磁电流,励磁模块采用电机驱动芯片替代了复杂的桥电路,使电路简单化,可靠性好,调试维修方便,成本低,通过软件配置实现励磁电流可调,使励磁电压低至3V,实现内置锂电池供电,较小体积,节约成本；CPU控制励磁模块产生励磁方波,同步检测励磁电流反馈值,用于对流量参数进行修正,提高测量精度。(The invention discloses an electromagnetic flowmeter converter with low-voltage adjustable exciting current, which relates to the technical field of electromagnetic flowmeters and comprises a CPU (central processing unit), an exciting module, a constant current source module and a power supply module, wherein the CPU controls the constant current source module to output different exciting currents by outputting pulse width of PWM (pulse width modulation), the exciting module adopts a motor driving chip to replace a complex bridge circuit, so that the circuit is simplified, the reliability is good, the debugging and the maintenance are convenient, the cost is low, the exciting current is adjustable through software configuration, the exciting voltage is reduced to 3V, the power supply of a built-in lithium battery is realized, the size is small, and the cost is saved; the CPU controls the excitation module to generate excitation square waves, synchronously detects an excitation current feedback value, and is used for correcting the flow parameter and improving the measurement precision.)

1. The utility model provides an adjustable exciting current's of low-voltage electromagnetic flow meter converter which characterized in that: the excitation constant-current source device comprises a CPU (1), an excitation module (2), a constant-current source module (3) and a power module (4), wherein the CPU (1), the excitation module (2), the constant-current source module (3) and the power module (4) are electrically connected with each other.

2. A low voltage, adjustable field current electromagnetic flowmeter converter as claimed in claim 1 wherein: the CPU (1) outputs the PWM pulse width through the pin to control the current of the constant current source module (3), changes the PWM pulse width through programming, controls the constant current source module (3) to output different constant current sources according to different pulse widths, and the constant current sources provide power for the excitation module (2), thereby obtaining different excitation currents.

3. A low voltage, adjustable field current electromagnetic flowmeter converter as claimed in claim 2 wherein: the excitation voltage of the excitation module (2) can be as low as 3V, and the excitation voltage is boosted by the constant current source module (3) so as to output a constant current source meeting the condition.

4. A low voltage, adjustable field current electromagnetic flowmeter converter as claimed in claim 1 wherein: the CPU (1) controls the excitation module (2) to generate excitation square waves, synchronously detects an excitation current feedback value, and compares the excitation current feedback value with a set excitation current, so that the flow parameter is corrected.

5. A low voltage, adjustable field current electromagnetic flowmeter converter as claimed in claim 1 wherein: the CPU (1) is a singlechip.

6. A low voltage, adjustable field current electromagnetic flowmeter converter as claimed in claim 1 wherein: the excitation module (2) is composed of a motor driving chip, a wiring terminal J100 and a sampling resistor R103.

7. A low voltage, adjustable field current electromagnetic flowmeter converter as claimed in claim 6 wherein: the sampling resistor R103 needs to adopt a resistor with low temperature drift, high precision and small resistance, and the power is not less than 0.5W.

8. A low voltage, adjustable field current electromagnetic flowmeter converter as claimed in claim 1 wherein: the constant current source module (3) is composed of a driving chip and an external circuit.

Technical Field

The invention relates to the technical field of door locks, in particular to a low-voltage electromagnetic flowmeter converter with adjustable exciting current.

Background

The measuring principle of the electromagnetic flowmeter is based on Faraday's law of electromagnetic induction-when the conductive liquid cuts magnetic lines of force and moves in a magnetic field, induced potential is generated in the conductor, the induced potential E is KBVD, K is an instrument coefficient in the formula, B is magnetic induction intensity, V is the average flow velocity in the section of the measuring pipeline, D is the inner diameter of the section of the measuring pipeline, and the E is in direct proportion to V when K, B, D is fixed. When the flow is measured, the conductive liquid flows through a magnetic field vertical to the flow direction at a flow velocity V, the flow of the conductive liquid induces a voltage which is in direct proportion to the average flow velocity on a measuring electrode, an induced voltage signal is detected by a pair of electrodes which are directly contacted with the liquid, and the induced voltage signal is processed by filtering, amplification and the like and then sent to a singlechip for analysis and calculation to obtain a required flow value. The electromagnetic flowmeter comprises two parts of a sensor and a converter, and K, D in the formula of E-KBVD is fixed after the sensor is produced. In manufacturing the electromagnetic flowmeter, in order to enable the electromagnetic flowmeter to measure a smaller flow velocity V, the magnetic induction intensity is ideally larger as better; because B is K1NI, (N is the number of turns of the field coil, I is the field current, and K1 is a coefficient, depending on the shape of the two field coils, the installation distance, the internal core, and so on, and also depending on the manufacturing process). When K1 is fixed, the magnetic induction B is proportional to the number of turns of the exciting coil, and theoretically, the more the number of turns of the exciting coil is, the better the exciting coil is, but the more the number of turns of the exciting coil is, the more the enameled wire is used, the higher the cost is, the higher the resistance is, and the more the heat is generated. Therefore, the magnetic induction B cannot be increased by adding the exciting coil N infinitely. Under the condition that the excitation coil N is fixed, the larger the excitation current I is, the better the excitation current I is, the higher the power consumption of the excitation current I is, the more expensive the used components are, and the higher the production cost is, so that a manufacturer divides the excitation current into several grades for production, but the mode of adjusting the excitation current through hardware is extremely inconvenient for the electromagnetic flowmeter manufacturer; in addition, the flow meter usually adopts external power supply (220V or 24V), and in reality, a short-time power loss situation (temporary power failure) occurs due to various reasons, and the electromagnetic flow meter cannot work due to power loss in the period of time, so that the metering loss is caused, so that a standby battery is particularly needed, and the power is supplied to the meter after the external power supply is temporarily powered off, so that the normal metering is ensured. The common rechargeable lithium battery for the mobile phone is economical and practical, but the common rechargeable lithium battery for the mobile phone cannot be used by an electromagnetic flowmeter due to low voltage, the main reason is that the excitation voltage of the electromagnetic flowmeter is high (generally 24V), a built-in standby battery for the magnetic flowmeter for the household appliance is not available at home so far, and if an external mode is adopted, 2 12V/12AH storage batteries are required to be equipped as a standby power supply, so that the size is large, the cost is high, and the use is inconvenient due to the external mode.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a low-voltage adjustable exciting current electromagnetic flowmeter converter, which solves the problems in the background art.

In order to achieve the purpose, the invention is realized by the following technical scheme: the low-voltage electromagnetic flowmeter converter with the adjustable exciting current comprises a CPU, an exciting module, a constant current source module and a power supply module, wherein the CPU, the exciting module, the constant current source module and the power supply module are electrically connected with each other.

Preferably, the CPU outputs the pulse width of the PWM through the pin to control the current of the constant current source module, changes the pulse width of the PWM through programming, controls the constant current source module to output different constant current sources according to different pulse widths, and the constant current sources provide power to the excitation module, thereby obtaining different excitation currents.

Preferably, the excitation voltage of the excitation module may be as low as 3V, and the excitation voltage is boosted by the constant current source module to output a constant current source satisfying the condition.

Preferably, the CPU controls the excitation module to generate an excitation square wave, synchronously detects an excitation current feedback value, and compares the excitation current feedback value with a set excitation current, thereby correcting the flow parameter.

Preferably, the CPU (1) is a single chip microcomputer.

Preferably, the excitation module is composed of a motor driving chip U103, a connection terminal J100 and a sampling resistor R103.

Preferably, the sampling resistor R103 is a resistor with low temperature drift, high precision and small resistance, and the power is not less than 0.5W.

Preferably, the constant current source module (3) is composed of a driving chip and an external circuit.

The invention provides a low-voltage adjustable exciting current electromagnetic flowmeter converter, which has the following beneficial effects:

(1) the CPU outputs the current of the PWM pulse width control constant current source module through the pin, the PWM pulse width is changed through programming, the constant current source module is controlled to output different constant current sources according to different pulse widths, the constant current source supplies power to the excitation module, so different excitation currents are obtained, the excitation voltage of the excitation module can be reduced to 3V, the voltage can be boosted through the constant current source module, the constant current sources meeting the conditions are output, the 3V low voltage enables the power supply of a 3.7V lithium battery to be possible, the lithium battery can be built in the electromagnetic flowmeter, the size is small, the cost is low, when the external power supply is cut off, the lithium battery supplies power, the use of the flowmeter is guaranteed, when the external power supply is recovered, the lithium battery can be charged, the consumed electric quantity is supplemented, the purpose of continuous use is achieved;

(2) the exciting current can be adjusted through software configuration, and is not required to be adjusted through hardware, so that the production is convenient;

(3) the CPU controls the excitation module to generate excitation square waves, and synchronously detects an excitation current feedback value for correcting the flow parameter and improving the measurement precision;

(4) the excitation module is composed of a motor drive chip U103, a wiring terminal J100 and a sampling resistor R103, and the excitation module adopts the motor drive chip to replace a complex bridge circuit, so that the circuit is simplified, the reliability is good, the debugging and the maintenance are convenient, and the cost is low.

Drawings

FIG. 1 is a schematic structural view of the present invention;

fig. 2 is a schematic circuit diagram of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

As shown in fig. 1, the low-voltage electromagnetic flowmeter converter with adjustable exciting current comprises a CPU1, an exciting module 2, a constant current source module 3 and a power module 4, wherein the CPU1, the exciting module 2, the constant current source module 3 and the power module 4 are electrically connected with each other.

As shown in fig. 2, the CPU1 selects a single chip microcomputer (U101) with a model number of C8051F 350. The single chip microcomputer is internally provided with a 24AD converter, the amplification factor can be selected from 1 time, 2 times, 4 times, 8 times, 16 times, 32 times, 64 times and 128 times, a measurement channel can be automatically calibrated, system errors are eliminated, and very high measurement precision can be obtained.

The excitation module (2) selects a chip (U103) with the model of RZ7899, the RZ7899 is a DC bidirectional motor driving circuit, and two logic input terminals are used for controlling the motor to advance, retreat and brake; the circuit has good anti-interference performance, small standby current (less than 2uA) and lower output internal resistance; meanwhile, the high-voltage DC power supply also comprises a built-in diode which can release reverse impact current of an inductive load, and the working voltage range is wide from 3.0V to 25V. The excitation object of the electromagnetic flowmeter is just two series-connected inductive coils, and the excitation current is just low-frequency square wave which is continuously turned in the forward direction and the reverse direction as the characteristic of the motor; the voltage is generally between 8 and 20V, and is completely consistent with the characteristics of the chip. The use of a single RZ7899 chip instead of a complex bridge circuit makes the complex excitation circuit very simple. The circuit has good reliability, convenient debugging and maintenance and very low cost. The chip also has overheat protection, overcurrent current embedding and short-circuit protection.

The constant current source module 3 selects a drive chip (U102) with the model number of BP1808LED, and the chip can output a constant current within 1A by using 3.0-60V voltage; the output constant current can be controlled in a PWM mode, and in addition, the BP1808LED has multiple protection functions, including overcurrent protection, input undervoltage protection, output overvoltage protection, chip overheating regulation and the like.