High-precision flow detection system

Abstract

This invention provides a high-precision flow detection system comprising: a throttling device, a driving unit, a conditioning unit, a filtering unit, and an analog-to-digital conversion unit. The throttling device is used to throttle the fluid to be measured and create a pressure difference. The driving unit includes a differential pressure flow sensor and a constant current source circuit. The differential pressure flow sensor is used to acquire the differential pressure signal flowing through the throttling device, and the constant current source circuit is used to drive the differential pressure flow sensor. The conditioning unit includes a differential amplifier circuit, which is used to amplify the differential pressure signal acquired by the differential pressure flow sensor. The filtering unit is a second-order low-pass filter used to filter interference signals. The analog-to-digital conversion unit includes an analog-to-digital converter and a processor. The analog-to-digital converter is used to convert the analog signal into a digital signal; the processor is used to receive the digital signal and convert the digital signal into flow data. The flow detection system provided by this invention has a fast response time, high resolution, and strong anti-interference capability.

Description

Technical Field

[0001] This invention relates to the field of flow detection technology, and more specifically to a high-precision differential pressure flow detection system. Background Technology

[0002] Flow measurement technology is a routine testing method in industrial measurement and is now frequently used in the medical device field. For example, pulmonary function testing is an essential examination method for respiratory diseases, primarily used to detect airway patency and lung capacity. It has significant clinical value in the early detection of lung and airway lesions, assessing disease severity and prognosis, and evaluating tolerance to surgery or physical exertion. All these testing methods are determined by measuring a patient's respiratory status, specifically by measuring respiratory flow. Unlike flow measurement in industrial measurement, flow measurement in medical devices typically needs to meet certain accuracy requirements.

[0003] The flow sensors in existing medical device flow detection systems are usually digital pressure sensors, which can directly read pressure signals, but have drawbacks such as slow response time, low resolution, and weak anti-interference ability. Summary of the Invention

[0004] Based on this, the present invention provides a high-precision flow detection system, which solves the problems of low detection accuracy and slow response time of existing flow detection systems for medical devices.

[0005] This invention provides a high-precision flow detection system, comprising: a throttling device, a driving unit, a conditioning unit, a filtering unit, and an analog-to-digital conversion unit. The throttling device is used to throttle the fluid to be measured and create a pressure difference. The driving unit includes a differential pressure flow sensor and a constant current source circuit. The differential pressure flow sensor is used to acquire the differential pressure signal flowing through the throttling device, and the constant current source circuit is used to drive the differential pressure flow sensor. The conditioning unit includes a differential amplifier circuit, which is used to amplify the differential pressure signal acquired by the differential pressure flow sensor. The filtering unit is a second-order low-pass filter used to filter interference signals. The analog-to-digital conversion unit includes an analog-to-digital converter and a processor. The analog-to-digital converter is used to convert analog signals into digital signals, and the processor is used to receive the digital signals and convert them into flow data.

[0006] Furthermore, the flow detection system also includes a power supply unit for supplying power to the circuit components in the flow detection system. The power supply unit includes a power connection terminal, a switching regulator, a linear regulator, and a series reference voltage source. The power connection terminal is used to connect to a power supply, which receives a supply voltage of 15V to 24V. The switching regulator is used to adjust the supply voltage to ±12.5V. The linear regulator is connected to the output terminal of the switching regulator and is used to adjust the supply voltage to ±12V. The series reference voltage source is connected to the +12V current output terminal of the linear regulator and is used to adjust the +12V supply voltage to +10V.

[0007] Furthermore, the power supply unit is an external power supply or a built-in power supply.

[0008] Furthermore, the flow detection system also includes a compensation unit, which comprises a temperature compensation circuit and a voltage compensation circuit. The temperature compensation circuit is used to acquire a temperature compensation signal, which is an error signal generated by the temperature rise of circuit components. The voltage compensation circuit is used to acquire a voltage compensation signal, which is a temperature drift and zero drift error signal. The conditioning unit also includes an inverting adder circuit, which is used to superimpose the temperature compensation signal and the voltage compensation signal from the flow detection system onto the differential pressure signal output by the differential pressure flow sensor.

[0009] Furthermore, the differential pressure flow sensor is an analog output differential pressure flow sensor.

[0010] Furthermore, the differential pressure flow sensor includes input pin 1, input pin 3, output pin 2, and output pin 4; the constant current source circuit includes a resistor R1 and an operational amplifier U2A, one end of the resistor R1 is connected to the output terminal of the series reference voltage source U1, and the other end is connected to the inverting input terminal of the operational amplifier U2A and the input pin 1 of the differential pressure flow sensor; the output terminal of the operational amplifier U2A is connected to the input pin 3 of the differential pressure flow sensor, and the non-inverting input terminal is connected to GND;

[0011] The differential amplifier circuit includes a differential operational amplifier U3. The two input phases of the differential operational amplifier U3 are respectively connected to the output pin 2 and the output pin 4 of the differential pressure flow sensor. The REF reference terminal is connected to GND, and the output terminal is connected to the inverting adder circuit through resistor R10.

[0012] Furthermore, the inverting adder circuit includes an operational amplifier U4, a capacitor C8, resistors R11, R12, R13, and R14. The inverting input terminal of the operational amplifier U4 is connected to the output terminal of the differential operational amplifier U3 through resistor R10, and connected to its output terminal through resistor R14. Its output terminal is connected to the compensation unit through resistors R11, R12, and R13, respectively, and its non-inverting input terminal is connected to GND. The capacitor C8 is connected in parallel across the resistor R14.

[0013] Further, the temperature compensation circuit includes a temperature sensor Temp, operational amplifiers U3A and U3B, capacitors C5 and C6, resistors R1, R2, R3, R4, R5, R8, and R9. The input terminal of the temperature sensor Temp is connected to the output terminal of the series reference voltage source U1 via resistor R, and connected to the inverting input terminal of operational amplifier U3A and one end of resistor R5 via R4. One end of resistor R2 is connected to the output terminal of the series reference voltage source U1, and the other end is connected to the non-inverting input terminal of operational amplifier U3A. One end of resistor R3 is connected to resistor R2 and the non-inverting input terminal of operational amplifier U3A, and the other end is connected to GND. One end of resistor R5 is connected to resistor R4 and the inverting input of operational amplifier U3A, and the other end is connected to the output of operational amplifier U3A; capacitor C5 is connected in parallel across resistor R5; the output of operational amplifier U3A is connected to the inverting adder circuit through resistor R12; one end of resistor R8 is connected to the output of operational amplifier U3A, and the other end is connected to the inverting input of operational amplifier U3B; one end of resistor R9 is connected to resistor R8 and the inverting input of operational amplifier U3B, and the other end is connected to the output of operational amplifier U3B; capacitor C6 is connected in parallel across resistor R9; the non-inverting input of operational amplifier U3B is connected to GND, and the output is connected to the inverting adder circuit through resistor R11.

[0014] The voltage compensation circuit includes an operational amplifier U2B, a capacitor C7, a resistor R6, and a resistor R7. One end of the resistor R6 is connected to the output of the series reference voltage source U1, and the other end is connected to the inverting input of the operational amplifier U2B. One end of the resistor R7 is connected to the resistor R6 and the inverting input of the operational amplifier U2B, and the other end is connected to the output of the operational amplifier U2B. The capacitor C7 is connected in parallel across the resistor R7. The non-inverting input of the operational amplifier U2B is connected to GND, and the output is connected to the inverting adder circuit through a resistor R13.

[0015] Further, the filtering unit includes operational amplifiers U5A and U5B, resistors R15, R16, R17, and R18, and capacitors C1, C2, C3, and C4. One end of resistor R15 is connected to the output terminal of operational amplifier U4 in the inverting adder circuit, and the other end is connected to resistor R16 and capacitor C1. The end of resistor R16 opposite to the connection of resistor R15 is connected to the inverting input terminal of operational amplifier U5A and one end of capacitor C2. The other end of capacitor C2 is connected to GND. The connection between capacitor C1 and resistor R15 is... One end of the resistor R17 is connected to the output of operational amplifier U5A; the non-inverting input of operational amplifier U5A is connected to its output; one end of resistor R17 is connected to the output of operational amplifier U5A, and the other end is connected to resistor R18 and capacitor C3; the opposite ends of resistor R18 and resistor R17 are connected to the inverting input of operational amplifier U5B and one end of capacitor C4, respectively; the other end of capacitor C4 is connected to GND; the opposite end of capacitor C3 and resistor R17 is connected to the output of operational amplifier U5A; the non-inverting input of operational amplifier U5B is connected to its output.

[0016] Furthermore, the input terminal of the analog-to-digital converter (ADC) is connected to the output terminal of the operational amplifier U5B.

[0017] This invention uses a differential pressure flow sensor with analog output for flow detection, which has fast response time, high resolution, and strong anti-interference ability; driven by a constant current source circuit, it can reduce the temperature difference caused by the heating of circuit components; and by setting a compensation unit, it can further improve the accuracy of flow detection. Attached Figure Description

[0018] Figure 1 This is a block diagram of the flow detection system in the first embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the flow detection system in the first embodiment of the present invention.

[0020] Figure 3 This is a schematic block diagram of the power supply unit in the first embodiment of the present invention.

[0021] Figure 4 This is a circuit diagram of a portion of the flow detection system in the first embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The accompanying drawings show preferred embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0024] refer to Figure 1 , Figure 2 The present invention provides a flow detection system, including a throttling device, a power supply unit, a drive unit, a conditioning unit, a compensation unit, a filtering unit, and an analog-to-digital conversion unit.

[0025] The throttling device is located in the flow channel of the fluid being measured, and is used to throttle the fluid and create a pressure difference. The flow detection system of this invention is applicable to various throttling devices, including but not limited to standard orifice plates, nozzles, venturi tubes, and flow-limiting orifice plates.

[0026] The power supply unit is used to power the electronic components in the flow detection system. Specifically, refer to... Figure 3 In the first embodiment of the present invention, the power supply unit includes a power connection terminal, a switching regulator, a linear regulator, and a series reference voltage source. The power connection terminal is used to connect to a power supply, through which a power supply voltage of 15V to 24V is input. The switching regulator is used to adjust the power supply voltage to ±12.5V. The linear regulator is connected to the current output terminal of the switching regulator and is used to adjust the voltage flowing out of the switching regulator to ±12V. The series reference voltage source is connected to the +12V current output terminal of the linear regulator and is used to adjust the +12V power supply voltage to +10V. In this scheme, the ±12V power supply can power the various operational amplifiers in the circuit; the +10V power supply can power the sensor and analog-to-digital converter (ADC), etc.

[0027] In this invention, the power supply can be an external power source, an internal battery, or a rechargeable power source, etc.

[0028] The driving unit includes a differential pressure flow sensor and a constant current source circuit. The differential pressure flow sensor is used to acquire the differential pressure signal flowing through the throttling device. The input terminal of the constant current source circuit is connected to the series reference voltage source to drive the differential pressure flow sensor to acquire the differential pressure signal. This invention employs a constant current source driving scheme, which can eliminate or significantly reduce the influence of temperature changes on the resistance value in the circuit, thereby improving the accuracy of flow detection.

[0029] refer to Figure 4 The constant current source circuit includes a resistor R1 and an operational amplifier U2A. One end of the resistor R1 is connected to the output terminal of the series reference voltage source U1, and the other end is connected to the inverting input terminal of the operational amplifier U2A and pin 1 of the differential pressure flow sensor. The output terminal of the operational amplifier U2A is connected to pin 3 of the differential pressure flow sensor, and the non-inverting input terminal is connected to GND.

[0030] The conditioning unit includes a differential amplifier circuit and an inverting adder circuit. The differential amplifier circuit is connected to the output terminal of the differential pressure flow sensor and is used to amplify the differential pressure signal collected by the differential pressure flow sensor. The inverting adder circuit is used to superimpose the compensation signal in the flow detection system onto the signal output by the differential pressure flow sensor.

[0031] refer to Figure 4 The differential amplifier circuit includes a differential operational amplifier U3. The two input phases of the differential operational amplifier U3 are respectively connected to the output terminals pin 2 and pin 4 of the differential pressure flow sensor. The REF reference terminal is connected to GND, and the output terminal is connected to the inverting adder circuit through resistor R10.

[0032] The inverting adder circuit includes an operational amplifier U4, a capacitor C8, resistors R11, R12, R13, and R14. The inverting input of the operational amplifier U4 is connected to the output of the differential operational amplifier U3 through resistor R10, and connected to its output through resistor R14. Its output is connected to the compensation unit through resistors R11, R12, and R13, respectively, and its non-inverting input is connected to GND. The capacitor C8 is connected in parallel across the resistor R14.

[0033] The compensation unit includes a temperature compensation circuit and a voltage compensation circuit. The temperature compensation circuit compensates for errors caused by temperature increases in circuit components; the voltage compensation circuit reduces temperature drift and zero drift errors. By incorporating a compensation unit into the flow detection system, errors can be further eliminated or reduced, improving the accuracy and precision of flow detection.

[0034] Furthermore, the temperature compensation circuit includes a temperature sensor (Temp), an operational amplifier U3A, a capacitor C5, resistors R1, R2, R3, R4, and R5. The input terminal of the temperature sensor (Temp) is connected to the output terminal of the series reference voltage source U1 via resistor R, and connected to the inverting input terminal of the operational amplifier U3A and one end of resistor R5 via R4. One end of resistor R2 is connected to the output terminal of the series reference voltage source U1, and the other end is connected to the non-inverting input terminal of the operational amplifier U3A. One end of resistor R3 is connected to resistor R2 and the non-inverting input terminal of the operational amplifier U3A, and the other end is connected to GND. One end of resistor R5 is connected to resistor R4 and the inverting input terminal of the operational amplifier U3A, and the other end is connected to the output terminal of the operational amplifier U3A. Capacitor C5 is connected in parallel across resistor R5. The output terminal of the operational amplifier U3A is connected to an inverting adder circuit via resistor R12. This scheme forms a proportional amplifier circuit to perform preliminary modulation of the voltage signal output by the temperature sensor.

[0035] Furthermore, the temperature compensation circuit also includes an operational amplifier U3B, a capacitor C6, resistors R8 and R9. One end of resistor R8 is connected to the output of operational amplifier U3A, and the other end is connected to the inverting input of operational amplifier U3B. One end of resistor R9 is connected to resistor R8 and the inverting input of operational amplifier U3B, and the other end is connected to the output of operational amplifier U3B. Capacitor C6 is connected in parallel across resistor R9. The non-inverting input of operational amplifier U3B is connected to GND, and its output is connected to an inverting adder circuit via resistor R11. This design amplifies the voltage signal output from the temperature sensor again before connecting it to the inverting adder circuit, enabling more accurate temperature compensation.

[0036] The voltage compensation circuit includes an operational amplifier U2B, a capacitor C7, resistors R6 and R7. One end of resistor R6 is connected to the output of the series reference voltage source U1, and the other end is connected to the inverting input of operational amplifier U2B. One end of resistor R7 is connected to resistor R6 and the inverting input of operational amplifier U2B, and the other end is connected to the output of operational amplifier U2B. Capacitor C7 is connected in parallel across resistor R7. The non-inverting input of operational amplifier U2B is connected to GND, and its output is connected to an inverting adder circuit through resistor R13. The voltage compensation circuit provided by this solution amplifies the voltage inversely before inputting it to the inverting adder circuit, thereby reducing temperature drift and zero drift errors and improving flow detection accuracy.

[0037] The filtering unit is a second-order low-pass filter used to filter interference signals. It includes an analog filtering circuit comprising an operational amplifier U5A, resistors R15 and R16, and capacitors C1 and C2. One end of resistor R15 is connected to the output of the operational amplifier U4 in the inverting adder circuit, and the other end is connected to both resistor R16 and capacitor C1. The end of resistor R16 opposite to the end connected to resistor R15 is connected to the inverting input of operational amplifier U5A and one end of capacitor C2. The other end of capacitor C2 is connected to GND. The end of capacitor C1 opposite to the end connected to resistor R15 is connected to the output of operational amplifier U5A. The non-inverting input of operational amplifier U5A is connected to its output. This design constitutes a second-order low-pass filter, which can effectively filter high-frequency noise and interference.

[0038] Furthermore, the analog filter circuit also includes an operational amplifier U5B, resistors R17 and R18, and capacitors C3 and C4. One end of resistor R17 is connected to the output of operational amplifier U5A, and the other end is connected to resistor R18 and capacitor C3. The ends of resistor R18 opposite to the connection of resistor R17 are connected to the inverting input of operational amplifier U5B and one end of capacitor C4, respectively. The other end of capacitor C4 is connected to GND. The end of capacitor C3 opposite to the connection of resistor R17 is connected to the output of operational amplifier U5A. The non-inverting input of operational amplifier U5B is connected to its output. The dual second-order low-pass filter constructed in this scheme further improves the signal's anti-interference capability.

[0039] The analog-to-digital conversion unit includes an analog-to-digital converter (ADC) and a processor (MCU). The ADC is used to convert analog signals into digital signals. The MCU is used to receive the digital signals from the ADC and convert the digital signals into readable flow data.

[0040] The input terminal of the analog-to-digital converter (ADC) is connected to the output terminal of the operational amplifier U5B.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-precision flow detection system, characterized in that, include: The system comprises a throttling device, a driving unit, a conditioning unit, a filtering unit, and an analog-to-digital conversion unit. The throttling device is used to throttle the fluid being measured and create a pressure differential. The driving unit includes a differential pressure flow sensor and a constant current source circuit. The differential pressure flow sensor is used to acquire the differential pressure signal flowing through the throttling device, and the constant current source circuit is used to drive the differential pressure flow sensor. The conditioning unit includes a differential amplifier circuit, which amplifies the differential pressure signal acquired by the differential pressure flow sensor. The filtering unit is a second-order low-pass filter used to filter interference signals. The analog-to-digital conversion unit includes an analog-to-digital converter and a processor. The analog-to-digital converter is used to convert analog signals into digital signals, and the processor is used to receive the digital signals and convert them into flow data. The flow detection system further includes a compensation unit, which comprises a temperature compensation circuit and a voltage compensation circuit. The temperature compensation circuit is used to acquire a temperature compensation signal, which is an error signal generated due to the temperature rise of circuit components. The voltage compensation circuit is used to acquire a voltage compensation signal, which is a temperature drift and zero drift error signal. The conditioning unit further includes an inverting adder circuit, which is used to superimpose the temperature compensation signal and the voltage compensation signal from the flow detection system onto the differential pressure signal output by the differential pressure flow sensor. Both the temperature compensation signal and the voltage compensation signal are voltage signals. The flow detection system also includes a power supply unit, which is used to supply power to the circuit components in the flow detection system; The power supply unit includes a series reference voltage source U1; The temperature compensation circuit includes a temperature sensor Temp, operational amplifiers U3A and U3B, capacitors C5 and C6, resistors R1, R2, R3, R4, R5, R8, and R9. The input terminal of the temperature sensor Temp is connected to the output terminal of the series reference voltage source U1 via resistor R, and connected to the inverting input terminal of operational amplifier U3A and one end of resistor R5 via R4. One end of resistor R2 is connected to the output terminal of the series reference voltage source U1, and the other end is connected to the non-inverting input terminal of operational amplifier U3A. One end of resistor R3 is connected to resistor R2 and the non-inverting input terminal of operational amplifier U3A, and the other end is connected to GND.

5. One end of resistor R4 is connected to the inverting input terminal of operational amplifier U3A, and the other end is connected to the output terminal of operational amplifier U3A; capacitor C5 is connected in parallel across resistor R5; the output terminal of operational amplifier U3A is connected to the inverting adder circuit through resistor R12; one end of resistor R8 is connected to the output terminal of operational amplifier U3A, and the other end is connected to the inverting input terminal of operational amplifier U3B; one end of resistor R9 is connected to resistor R8 and the inverting input terminal of operational amplifier U3B, and the other end is connected to the output terminal of operational amplifier U3B; capacitor C6 is connected in parallel across resistor R9; the non-inverting input terminal of operational amplifier U3B is connected to GND, and the output terminal is connected to the inverting adder circuit through resistor R11; The voltage compensation circuit includes an operational amplifier U2B, a capacitor C7, a resistor R6, and a resistor R7. One end of the resistor R6 is connected to the output of the series reference voltage source U1, and the other end is connected to the inverting input of the operational amplifier U2B. One end of the resistor R7 is connected to the resistor R6 and the inverting input of the operational amplifier U2B, and the other end is connected to the output of the operational amplifier U2B. The capacitor C7 is connected in parallel across the resistor R7. The non-inverting input of the operational amplifier U2B is connected to GND, and the output is connected to the inverting adder circuit through a resistor R13.

2. The high-precision flow detection system according to claim 1, characterized in that, The power supply unit further includes a power connection terminal, a switching regulator, and a linear regulator. The power connection terminal is used to connect to a power supply, through which a supply voltage of +15V to +24V is input. The switching regulator is used to adjust the supply voltage to ±12.5V. The linear regulator is connected to the output terminal of the switching regulator and is used to adjust the supply voltage to ±12V. The series reference voltage source U1 is connected to the +12V current output terminal of the linear regulator and is used to adjust the +12V supply voltage to +10V.

3. The high-precision flow detection system according to claim 2, characterized in that, The power supply unit is either an external power source or a built-in power source.

4. The high-precision flow detection system according to claim 1, characterized in that, The differential pressure flow sensor is an analog output differential pressure flow sensor.

5. The high-precision flow detection system according to claim 1, characterized in that, The differential pressure flow sensor includes input pin 1, input pin 3, output pin 2, and output pin 4; the constant current source circuit includes resistor R1 and operational amplifier U2A. One end of resistor R1 is connected to the output of the series reference voltage source U1, and the other end is connected to the inverting input of operational amplifier U2A and input pin 1 of the differential pressure flow sensor; the output of operational amplifier U2A is connected to input pin 3 of the differential pressure flow sensor, and the non-inverting input is connected to GND. The differential amplifier circuit includes a differential operational amplifier U3. The two input phases of the differential operational amplifier U3 are respectively connected to the output pin 2 and the output pin 4 of the differential pressure flow sensor. The REF reference terminal is connected to GND, and the output terminal is connected to the inverting adder circuit through resistor R10.

6. The high-precision flow detection system according to claim 5, characterized in that, The inverting adder circuit includes an operational amplifier U4, a capacitor C8, resistors R11, R12, R13, and R14. The inverting input of the operational amplifier U4 is connected to the output of the differential operational amplifier U3 through resistor R10, and connected to its output through resistor R14. Its output is connected to the compensation unit through resistors R11, R12, and R13, respectively, and its non-inverting input is connected to GND. The capacitor C8 is connected in parallel across the resistor R14.

7. The high-precision flow detection system according to claim 1, characterized in that, The filtering unit includes operational amplifiers U5A and U5B, resistors R15, R16, R17, and R18, and capacitors C1, C2, C3, and C4. One end of resistor R15 is connected to the output terminal of operational amplifier U4 in the inverting adder circuit, and the other end is connected to resistor R16 and capacitor C1. The end of resistor R16 opposite to the connection of resistor R15 is connected to the inverting input terminal of operational amplifier U5A and one end of capacitor C2. The other end of capacitor C2 is connected to GND. The end of capacitor C1 opposite to the connection of resistor R15... One end of resistor R17 is connected to the output of operational amplifier U5A; the non-inverting input of operational amplifier U5A is connected to its output; one end of resistor R17 is connected to the output of operational amplifier U5A, and the other end is connected to resistor R18 and capacitor C3; the ends of resistor R18 and resistor R17 opposite to each other are connected to the inverting input of operational amplifier U5B and one end of capacitor C4, respectively; the other end of capacitor C4 is connected to GND; the end of capacitor C3 opposite to the end of resistor R17 is connected to the output of operational amplifier U5A; the non-inverting input of operational amplifier U5B is connected to its output.

8. The high-precision flow detection system according to claim 7, characterized in that, The input terminal of the analog-to-digital converter (ADC) is connected to the output terminal of the operational amplifier U5B.

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