A self-calibrating electromagnetic flowmeter with current output

Abstract

This invention relates to a self-calibrating electromagnetic flowmeter with current output, comprising a microcontroller circuit, a memory circuit, a power isolation circuit, an optocoupler isolation circuit, a current output circuit, and a current detection circuit. The microcontroller circuit calculates the current value corresponding to the current flow rate of the electromagnetic flowmeter, corrects the actual output value by reading parameters from the memory circuit, and uses a timer function to output a PWM signal with a fixed frequency and adjustable duty cycle. The current output circuit converts the PWM signal into a 4-20mA current signal. The current detection circuit detects the actual output current and feeds the result back to the microcontroller, enabling a current output from 4mA to 20mA from the zero point of the clean water flow to full scale. The output current can self-calibrate within the range of load variations and in situations with changes in ambient temperature and humidity, ensuring that the accuracy of the output current is not affected by external factors.

Description

Technical Field

[0001] This utility model relates to a technology for self-calibrating current output, and particularly to an electromagnetic flowmeter for self-calibrating current output. Background Technology

[0002] The output current of an electromagnetic flowmeter is one of its core functional parameters, directly affecting the transmission of the measurement signal and the system integration effect. Currently, the mainstream output current standard for electromagnetic flowmeters is 4-20mA, a range widely used in industrial automation due to its advantages such as strong anti-interference capability, long transmission distance, and high signal resolution accuracy. However, the accuracy of the direct output current cannot be guaranteed due to factors such as ambient temperature, humidity, power frequency interference, lightning surges, transmission distance, and load size. Therefore, a self-calibrating electromagnetic flowmeter with current output was designed. While outputting current, the flowmeter detects the output current and feeds it back to the microcontroller to complete closed-loop regulation and self-calibration, ensuring the linearity of the output current. Summary of the Invention

[0003] This invention provides an electromagnetic flowmeter with self-calibrating current output, enabling current output from 4mA to 20mA from the zero point of the clean water flow to full scale. The output current can self-calibrate within the range of load variations and in situations with changes in ambient temperature and humidity, ensuring that the accuracy of the output current is not affected by external factors.

[0004] To achieve the above objectives, the technical solution of this utility model is as follows: An electromagnetic flowmeter with self-calibrating current output includes a microcontroller circuit, a memory circuit, a power isolation circuit, an optocoupler isolation circuit, a current output circuit, and a current detection circuit, characterized in that: The microcontroller circuit calculates the current value corresponding to the current flow rate of the electromagnetic flowmeter, corrects the actual output value by reading the parameters of the memory circuit, and uses the timer function to output a PWM signal with a fixed frequency and adjustable duty cycle. The memory circuit is used to save the correction parameters calculated after current feedback for easy output in the next time. The power isolation circuit is used to isolate the power supply and current output power of the microcontroller. The optocoupler isolation circuit is used to isolate the microcontroller's PWM signal to ensure signal integrity. The current detection circuit detects the actual output current and feeds the result back to the microcontroller. The current output circuit is used to convert the PWM signal into a 4-20mA current signal.

[0005] The beneficial effects of this utility model are: (1) The measurement accuracy of this utility model is more stable, and the self-calibration can correct the current output deviation in real time, avoiding errors caused by zero drift and signal attenuation during long-term use.

[0006] (2) The operation and maintenance costs of this utility model are significantly reduced. It does not require frequent disassembly of equipment or external standard instrument calibration, thus reducing downtime and labor input.

[0007] (3) This utility model has a wider range of applicable scenarios and can adapt to complex working conditions such as medium fluctuations and changes in ambient temperature. Its self-calibration function can dynamically compensate for external influences.

[0008] (4) This utility model is more convenient to operate, requires no professional calibration knowledge, and the equipment automatically completes the calibration process, reducing the risk of human error. Attached Figure Description

[0009] Appendix Figure 1 This is a schematic diagram of the electromagnetic flowmeter module with self-calibrating current output of this utility model. Appendix Figure 2 This invention relates to a microcontroller circuit.

[0010] Appendix Figure 3 This invention relates to a memory circuit.

[0011] Appendix Figure 4 This invention relates to a power isolation circuit.

[0012] Appendix Figure 5 This invention relates to an optocoupler isolation circuit.

[0013] Appendix Figure 6 This invention relates to a current output circuit.

[0014] Appendix Figure 7 This invention relates to a current detection circuit. Detailed Implementation

[0015] The technical solution of this utility model will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0016] As attached Figure 1 This invention discloses a self-calibrating electromagnetic flowmeter with current output, comprising a microcontroller circuit, a memory circuit, a power isolation circuit, an optocoupler isolation circuit, a current output circuit, and a current detection circuit. The microcontroller calculates the required current output and outputs a signal. Upon receiving the signal, the current output circuit outputs the actual current. The current detection circuit measures the actual current and feeds it back to the microcontroller. The microcontroller calculates the actual output current and the theoretical current, sets calibration parameters, stores these parameters, and adjusts the output signal, thus achieving self-calibration of the current output.

[0017] As attached Figure 2The diagram shows the microcontroller circuit. The MCU microcontroller uses Fudan Micro FM33LG048, and the peripheral circuit is the circuit required for the minimum working system of the microprocessor. Pin 60 of the MCU microcontroller chip U3 is connected to one end of the passive crystal oscillator Y1 and one end of capacitor C9. The other end of capacitor C9 is connected to ground GND. Pin 61 of the MCU microcontroller chip U3 is connected to the other end of the passive crystal oscillator Y1 and one end of capacitor C10. The other end of capacitor C10 is connected to ground GND. The microcontroller obtains the current flow rate, calculates the current output magnitude corresponding to the current flow rate according to the range, reads the correction coefficient in the memory, calculates the duty cycle of the PWM signal, and outputs this PWM signal using the timer function.

[0018] As attached Figure 3 As shown: The memory circuit is used to save the correction parameters calculated after current feedback for easy output in the next cycle. The memory uses FM25V02. The chip select terminal CS is connected to pin PC6 of the MCU microcontroller chip, the SDO1 terminal is connected to pin PC5 of the microprocessor, the WP1 terminal is connected to pin PC4 of the microprocessor, the SCLK terminal is connected to pin PC3 of the microprocessor, and the SDI terminal is connected to pin PC2 of the microprocessor. Pins 7 and 8 of the FLASH memory chip U4 are connected to the power supply VCC, one end of capacitor CM2, and the positive terminal of capacitor CM1. The negative terminal of capacitor CM2 and the other end of capacitor CM1 are connected to ground GND. As attached Figure 4 As shown: The power isolation circuit is used to isolate the power supply of the microcontroller and the power supply of the current output. In industrial sites, the current signal output by the electromagnetic flowmeter may be subject to external interference. In order to avoid the external interference affecting the metering function, the power isolation circuit is used to isolate the 24V power supply of the main circuit and supply it separately to the optocoupler isolation circuit and the current output circuit, so as to ensure the anti-interference performance of the electromagnetic flowmeter.

[0019] As attached Figure 5 As shown: The optocoupler isolation circuit is used to isolate the PWM of the microcontroller to ensure signal integrity. Specifically, the PC14 terminal of the microprocessor is connected to the input terminal of the N-type MOSFET, the drain terminal of the MOSFET is connected to the input terminal of the optocoupler, and the output terminal of the optocoupler is connected to the current output circuit. The PWM signal cannot be directly transmitted to the current output circuit. The optocoupler isolation circuit is used to isolate the PWM output of the microcontroller circuit to the current output circuit to form signal isolation.

[0020] As attached Figure 6As shown: The current output circuit converts the PWM signal into a 4-20mA current signal. The GP8101 PWM signal-to-analog signal converter receives the PWM signal and, based on its duty cycle, outputs the analog signal via a DAC. Through a high-precision resistor, the current is output. The PWM signal is then converted into a 4-20mA current signal and output to the current detection circuit.

[0021] As attached Figure 7 As shown: The current detection circuit detects the actual output current and feeds the result back to the microcontroller. Specifically, it uses the INA199 current sensing amplifier chip and its peripheral circuitry. The V+ terminal is connected to the power supply VDD, and the GND terminal is grounded. The OUT terminal of the front-end current output circuit is connected to the IN+ and IN- terminals of the INA199 chip via a MOSFET and a voltage divider resistor. The OUT terminal of the INA199 chip provides an analog signal input to the PC9 terminal of the microprocessor, senses the voltage drop across the sampling resistor, and outputs an analog signal to the microcontroller. After acquiring the signal, the microcontroller compares it with the theoretical current and calculates a new correction factor.

Claims

1. A current output self-calibrating electromagnetic flowmeter, comprising a microcontroller circuit, a memory circuit, a power isolation circuit, an optocoupler isolation circuit, a current output circuit, and a current detection circuit, characterized in that: The microcontroller circuit calculates the current value corresponding to the current flow rate of the electromagnetic flowmeter, corrects the actual output value by reading the parameters of the memory circuit, and uses the timer function to output a PWM signal with a fixed frequency and adjustable duty cycle. The memory circuit is used to save the correction parameters calculated after current feedback for easy output in the next time. The power isolation circuit is used to isolate the power supply and current output power of the microcontroller. The optocoupler isolation circuit is used to isolate the microcontroller's PWM signal to ensure signal integrity. The current detection circuit detects the actual output current and feeds the result back to the microcontroller. The current output circuit is used to convert the PWM signal into a 4-20mA current signal.

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