Liquid flow detection system and method based on thin film thermistor

Abstract

The invention relates to a liquid flow detection system based on a thin film thermistor, and the system comprises a pipeline which is used for conveying to-be-detected liquid; the sensor body is mounted on the pipe wall of the pipeline; the inductive probe is arranged at the bottom of the sensor body and extends into a flow channel of the pipeline, the inductive probe comprises a heating resistor serving as a heating element and a temperature measuring resistor serving as a temperature measuring element, and the temperature measuring resistor is located at the downstream of the heating resistor; and the signal processing circuit board is arranged inside or outside the sensor body, is electrically connected with the heating resistor and the temperature measuring resistor, and is used for collecting and processing temperature signals. According to the invention, the MEMS film thermistor is utilized, the thermal capacity is small, the response is fast, and the fault of a traditional thermal sensor is broken through; according to the method, the thermal saturation bottleneck of a small flow area with the flow rate of 1 [mu] L / min is overcome, and a delta T / delta t composite algorithm model is introduced, so that the linearity and the sensitivity of the low flow area are effectively expanded, and the flow measurement with the precision of nL / min to [mu] L / min is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of liquid flow detection, and particularly relates to a liquid flow detection system and method based on a thin-film thermistor. BACKGROUND

[0002] With the explosive growth of demand for micro-flow measurement in microfluidic, biomedical, precision chemical analysis and other cutting-edge application scenarios, the limitations of traditional flow detection technology are increasingly prominent. Existing detection technologies mainly include the following:

[0003] 1. Mechanical flow meters represented by turbines, gears or volumetric structures rely on the direct contact of moving parts with the fluid to achieve measurement, but problems such as bearing wear, gear mesh surface scratches and seal aging may occur after long-term operation;

[0004] 2. Ultrasonic time difference method flow meters calculate flow rate by measuring the time difference of forward and reverse flow sound wave transmission. Although the non-contact feature avoids wear, the hardware cost is high and the medium purity is sensitive;

[0005] 3. Thermal sensors using bulk thermistors or metal heating wires may cause "thermal saturation" in the low flow area when the heating element has a large thermal diffusion depth, resulting in insufficient precision.

[0006] And when the flow is lower than 1 muL / min, i.e. in the micro-flow monitoring blind area, all traditional technologies will fail in principle, such as mechanical flow meters, which require the starting torque to overcome the static friction of the bearing, and cannot continue to rotate when the corresponding water flow driving force is too small. Therefore, a new type of detection machine and scheme is designed for low wear, low cost, micro-flow measurement, millisecond-level response and anti-interference. SUMMARY

[0007] To achieve the above-mentioned purpose, the application provides a liquid flow detection system based on a thin-film thermistor, comprising:

[0008] a pipeline for conveying the liquid to be measured;

[0009] a sensor body mounted on the pipe wall of the pipeline;

[0010] an inductive probe arranged at the bottom of the sensor body and extending into the flow channel of the pipeline, the inductive probe comprising a heating resistor as a heating element and a temperature measuring resistor as a temperature measuring element, the temperature measuring resistor being located downstream of the heating resistor;

[0011] a signal processing circuit board arranged inside or outside the sensor body and electrically connected with the heating resistor and the temperature measuring resistor, for collecting and processing temperature signals;

[0012] The data processing unit is communicatively connected to the signal processing circuit board and is used to calculate the instantaneous flow rate and / or cumulative flow rate of the liquid based on the temperature difference between the heating resistor and the temperature measuring resistor and the time of change of the temperature difference, combined with the thermal diffusion algorithm.

[0013] Preferably, both the heating resistor and the temperature measuring resistor are thin-film thermistors manufactured using MEMS technology, and they are arranged in parallel on the substrate of the sensing probe with a spacing of 1-3 mm.

[0014] Preferably, the signal processing circuit board integrates:

[0015] A constant current source circuit is used to provide a constant heating power of 0.3-1W to the heating resistor;

[0016] A high-precision operational amplifier is used to amplify the weak signal from the temperature sensing resistor;

[0017] A 24-bit analog-to-digital converter (ADC) is used to convert amplified analog signals into digital signals.

[0018] Preferably, the system further includes a temperature compensation module, which is configured to compensate for the measured values ​​of the heating resistor and / or the temperature measuring resistor by acquiring the ambient temperature or the initial temperature of the liquid, so as to eliminate the influence of ambient temperature fluctuations on the accuracy of flow measurement.

[0019] Preferably, the data processing unit internally stores a traffic calculation program, which executes the following calculation model:

[0020] Q = K × (ΔT / Δt) × (1 / ρCp)

[0021] Where Q is the volumetric flow rate, K is the sensor constant obtained through calibration, ΔT is the stable temperature difference between the heating resistor and the temperature measuring resistor, Δt is the time required to reach the stable temperature difference or the unit sampling time, ρ is the preset liquid density parameter, and Cp is the preset liquid specific heat capacity parameter.

[0022] Preferably, it also includes a display unit for locally displaying traffic data or transmitting traffic data to a host computer system.

[0023] A second aspect of the present invention provides a detection method based on the liquid flow detection system, comprising the following steps:

[0024] The S1 constant current source circuit drives the heating resistor with a constant power of 0.3-1W, so that the induction probe establishes a transient thermal diffusion field in the pipe channel.

[0025] The S2 temperature sensing resistor collects the temperature change caused by the liquid flow 1-3mm downstream of the heating resistor and outputs a weak resistance signal.

[0026] The S3 high-precision operational amplifier amplifies the weak resistance signal, and the 24-bit ADC converts the amplified analog signal into a digital temperature signal.

[0027] The S4 temperature compensation module synchronously acquires the ambient temperature or the initial temperature of the liquid and performs drift compensation on the digital temperature signal to obtain a compensated stable temperature difference ΔT.

[0028] The S5 data processing unit executes the thermal diffusion model Q=K×(ΔT / Δt)×(1 / ρCp) to calculate the instantaneous flow rate, and then integrates the instantaneous flow rate over time to obtain the cumulative flow rate;

[0029] The S6 display unit or communication interface outputs the instantaneous flow rate and / or cumulative flow rate to the local display and / or host computer system.

[0030] Preferably, in step S4, the temperature compensation module collects the ambient temperature or the initial temperature of the liquid in real time through a reference temperature sensor installed on the outer wall of the pipe or upstream of the liquid, and uses a digital filtering and mapping algorithm to dynamically correct ΔT, thereby eliminating the zero-point offset of the flow rate caused by fluctuations in ambient temperature.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] This invention utilizes MEMS thin-film thermistors, which have small thermal capacity and fast response, to overcome the "thermal saturation" bottleneck of traditional thermal sensors in the <1μL / min microflow range. Furthermore, by introducing a ΔT / Δt composite algorithm model, it effectively extends the linearity and sensitivity in the low flow range, achieving flow measurement accuracy in the nL / min to μL / min range.

[0033] The thin film structure in this invention has a short thermal diffusion path and a significantly shortened response time, which can capture rapid flow changes. Furthermore, the system can predict flow changes by observing the trend of Δt changes before the system can fully stabilize, thereby improving dynamic response capabilities.

[0034] This invention uses the ΔT / Δt ratio model to balance signal strength in the low flow rate region and linearity in the high flow rate region, avoiding the signal attenuation problem of traditional sensors in the high flow rate region. At the same time, through the coordinated work of a 24-bit ADC and a temperature compensation module, temperature drift is effectively suppressed, and long-term stability and repeatability are improved.

[0035] This invention incorporates a temperature compensation module that uses a reference temperature sensor to correct ΔT in real time, eliminating the impact of ambient temperature fluctuations on the zero point. It also supports preset input of different liquid parameters (ρ, Cp), adapting to various media such as water, oil, and chemical reagents, thus enhancing versatility. Attached Figure Description

[0036] Figure 1This is a schematic diagram of the structural design of the liquid flow detection system in this invention;

[0037] Figure 2 This is a diagram illustrating the operation of liquid flow detection according to the present invention;

[0038] Figure 3 This is a schematic diagram showing the installation of the two thin-film resistors in this invention;

[0039] Figure 4 This is a schematic diagram of the liquid flow detection system in this invention;

[0040] Figure 5 This is a flowchart of the liquid flow detection method in this invention.

[0041] The numbers in the diagram are: 1-pipe, 2-sensor body, 3-sensing probe, 301-heating resistor, 302-temperature sensing resistor, 4-signal processing circuit board, 401-constant current source circuit, 402-high precision operational amplifier, 403-24-bit analog-to-digital converter (ADC), 5-data processing unit, 6-temperature compensation module, 7-display unit. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1

[0044] like Figures 1 to 5 The structural design of a liquid flow detection system shown includes: a pipe 1 for conveying the liquid to be measured, with an inner diameter ranging from 4 to 10 mm, made of 316L stainless steel, and an inner wall roughness Ra≤0.4μm to reduce turbulence noise; and a sensor body 2 installed on the pipe wall of the pipe 1 in a fully enclosed manner, with the sensor body 2 and the pipe wall sealed by double fluororubber.

[0045] The sensor body 2 has an integrated sensing probe 3 at its bottom. The sensing probe 3 extends into the flow channel of the pipe 1. The sensing probe 3 includes a heating resistor 301 as a heating element and a temperature measuring resistor 302 as a temperature measuring element. The temperature measuring resistor 302 is installed downstream of the heating resistor 301. Both resistors are thin-film thermistors manufactured using MEMS technology and are arranged in parallel on the substrate of the sensing probe 3 at a spacing of 1–3 mm.

[0046] Specifically, the probe uses a 316 stainless steel shell with a diameter of 3mm, a length of 15mm, and a wall thickness of 0.2mm. The end is laser-welded and sealed, and the surface is electrolytically polished to Ra≤0.1μm to reduce the risk of adhesion and corrosion. Two thin-film thermistors are encapsulated inside the probe, with a spacing of 2mm, a film thickness of 1μm, and a line width of 20μm. They are made of platinum or nickel and fabricated on a 0.5mm thick alumina ceramic substrate through sputtering-photolithography-stripping processes. They are led out through 30AWG polyimide insulated leads and a glass-metal seal transition is used at the tail of the probe to ensure no leakage during long-term immersion.

[0047] The back of the substrate is etched with MEMS microchannels that are 50 μm deep and 200 μm wide, which maintains laminar flow in the Reynolds number Re range of 200–2000, reduces the interference of flow rate pulsation on temperature difference measurement, guides the liquid to flow closely to the heat-sensitive surface, improves heat exchange efficiency and reduces the response time to <50ms.

[0048] Example 2

[0049] like Figures 1 to 5 The liquid flow detection system shown includes a pipe 1 for conveying the liquid to be measured, and a sensor body 2 fully enclosed on the pipe wall. A sensing probe 3 at the bottom of the sensor body 2 extends directly into the flow channel. Two thin-film thermistors at the bottom of the probe contact the fluid and acquire thermal signals based on the "thermal diffusion principle": one acts as a heating resistor 301, establishing a small, controllable thermal field within the fluid; the other acts as a temperature sensing resistor 302, precisely positioned downstream of the heating element, monitoring the heat changes caused by fluid flow. When the fluid is stationary, heat slowly diffuses downstream, forming a stable temperature distribution. Once the fluid begins to flow, it carries heat, causing the temperature change sensed by the downstream temperature sensing resistor 302 to establish a precise correlation with the flow rate, achieving high-precision fluid detection.

[0050] Furthermore, a signal processing circuit board 4 is installed inside the sensor body 2, which is electrically connected to two thin-film resistors to provide stable energy excitation and digitally convert the resistance and voltage signals from the resistor feedback to provide data support for subsequent calculations.

[0051] The signal processing circuit board 4 is connected to the data processing unit 5, which uses an ARM Cortex-M4 core microcontroller to run the detection algorithm in real time and achieve powerful digital information processing. By analyzing the stable temperature difference between the heating point and the temperature measuring point, and integrating it, the instantaneous flow rate of the liquid can be quickly calculated. Moreover, this system can also perform time integration on the instantaneous flow rate to easily obtain the cumulative flow rate, which can be used to meet the needs of energy metering or total process statistics.

[0052] Furthermore, to adapt to different application scenarios, this embodiment can, on the one hand, display local values ​​through the integrated display unit 7 for convenient real-time reading by on-site personnel, and on the other hand, seamlessly upload formatted flow data (including instantaneous flow, cumulative flow, equipment status, etc.) to the central control room, data acquisition and monitoring control system, or cloud IoT platform through the standard communication interface to achieve remote monitoring and big data analysis.

[0053] Example 3

[0054] like Figures 1 to 5 The liquid flow detection system shown has a signal processing circuit board 4, which is electrically connected to two thin-film resistors to provide a stable drive motor and digitizes the resistance and voltage signals fed back by the resistors to provide data support for subsequent calculations.

[0055] Specifically, the signal processing circuit board 4 integrates:

[0056] This is used to provide a highly stable drive current to the thin-film resistor, which serves as the heating element, specifically a 50mA constant current source. In practical applications, fluctuations in the external power supply voltage and temperature changes in the heating resistor 301 will cause changes in resistance, leading to measurement errors. The use of the constant current source circuit 401 ensures that the current flowing through the heating resistor 301 remains constant, ensuring the repeatability and consistency of the thermal diffusion field establishment, avoiding measurement errors caused by fluctuations in heating power, and providing a stable and reliable physical basis for the entire measurement principle.

[0057] And a high-precision operational amplifier 402 for amplifying the weak signal from the temperature-sensing resistor 302. The downstream temperature-sensing thin-film resistor has extremely weak signal changes due to temperature variations, which are easily drowned out by circuit noise. The high-precision operational amplifier 402 is responsible for receiving and amplifying the weak voltage signal fed back by the temperature-sensing resistor 302. Through its own extremely low noise, low temperature drift and high input impedance, it effectively amplifies the useful signal while suppressing external interference and distortion introduced by itself to the maximum extent.

[0058] Next is the 24-bit analog-to-digital converter (ADC) 403, which converts the amplified analog signal into a digital signal. Specifically, it converts the continuous analog signal into a discrete digital signal that can be processed by the microprocessor. By using a 24-bit high-resolution ADC, the full-scale analog voltage signal is divided into more than 16 million discrete levels, thereby clearly distinguishing extremely small voltage changes in the amplified signal. At the same time, it provides a fast data acquisition speed with a sampling rate of 1kHz, fully capturing the rapid temperature fluctuations caused by changes in fluid flow rate, ensuring the system's excellent dynamic response capability.

[0059] Example 4

[0060] like Figures 1 to 5 The liquid flow detection system shown has a signal processing circuit board 4 that is communicatively connected to a data processing unit 5. The data processing unit 5 uses an ARM Cortex-M4 core microcontroller to run the detection algorithm in real time and achieve powerful digital information processing. In practical applications, the data processing unit 5, with the ARM Cortex-M4 core microcontroller as its core, uses its powerful real-time computing capabilities and digital signal processing efficiency to transform the raw data collected from the front end into accurate and reliable flow information.

[0061] The data processing unit 5 internally stores an optimized dedicated flow calculation program, which executes the following intelligent algorithm model based on the "thermal diffusion principle":

[0062] Q = K × (ΔT / Δt) × (1 / ρCp)

[0063] Where Q is the volumetric flow rate; K is the sensor constant obtained through calibration; ΔT is the stable temperature difference between the heating resistor 301 and the temperature measuring resistor 302, which reflects the fluid's ability to remove heat from the heating unit in a stable state and is a static characterization of the flow rate; Δt is the time required to reach a stable temperature difference or the unit sampling time, which captures the speed at which the system's thermal field reaches equilibrium from its initial state. The faster the flow rate, the faster the thermal equilibrium is established, and the shorter Δt is; ρ is the preset liquid density parameter, which allows the density and specific heat capacity parameters of the liquid being measured (such as water, oil, chemical reagents, etc.) to be pre-configured according to its physical properties. Through the ×(1 / ρCp) term, a preset interface is provided for liquids with different thermal properties. By modifying the ρ and Cp parameters, different liquids can be adapted, enhancing the system's versatility. Here, Cp is the preset liquid specific heat capacity parameter.

[0064] Specifically, in this embodiment, Δt is explicitly defined as "the time required for the system to establish a stable, calculable temperature difference ΔT between the heating resistor 301 and the downstream temperature measuring resistor 302 from the start of heating," thus capturing the dynamic entire process of the thermal diffusion field establishing itself in the fluid. Compared with traditional calculation models:

[0065]

[0066] In summary, this embodiment, by introducing and precisely defining the time parameter Δt, elevates the single temperature difference signal ΔT into a composite signal ΔT / Δt that includes both intensity and velocity information. This solves the problems of "saturation" and slow response in the low flow rate region, extends the lower limit of the measurement range, avoids signal attenuation in the high flow rate region, extends the upper limit of the measurement range, and provides better linearity across the entire range. Furthermore, the above calculation program works closely with the 24-bit ADC and the temperature compensation module 6. The 24-bit ADC ensures accurate measurement of both weak ΔT and rapid Δt, while the temperature compensation module 6 guarantees the accuracy of the ΔT reference. Together, these three components form a high-precision, high-stability measurement closed loop.

[0067] Example 5

[0068] like Figures 1 to 5 The liquid flow detection system shown also includes a temperature compensation module 6, which is configured to compensate for the measured values ​​of heating resistor 301 and / or temperature measuring resistor 302 by acquiring the ambient temperature or the initial temperature of the liquid, so as to eliminate the influence of ambient temperature fluctuations on the flow measurement accuracy.

[0069] Specifically, the temperature compensation module 6 continuously and synchronously collects one of two key temperatures through its built-in temperature sensor: one is used to sense the temperature of the installation environment, and the other is used to directly obtain the actual inlet temperature of the liquid being measured. The raw temperature signal collected is then smoothed to ensure the stability of the compensation benchmark. Based on the pre-stored information in the system, namely the inherent characteristics of the heating resistor 301 and the temperature measuring resistor 302 at different benchmark temperatures and the corresponding relationship of the parameters of the thermal diffusion model, the key parameters in the calculation model are dynamically adjusted by looking up tables or by real-time calculation. The corrected temperature signal is then sent into the calculation model to obtain an accurate flow rate value.

[0070] Example 6

[0071] like Figure 5 The operating method shown is based on a liquid flow detection system and includes the following steps:

[0072] S1 constant current source circuit 401 drives heating resistor 301 with a constant power of 0.3-1W, so that induction probe 3 establishes a transient thermal diffusion field in the flow channel of pipe 1.

[0073] The S2 temperature sensing resistor 302 collects the temperature change caused by the liquid flow 1-3mm downstream of the heating resistor 301 and outputs a weak resistance signal.

[0074] The S3 high-precision operational amplifier 402 amplifies the weak resistance signal, and the 24-bit ADC converts the amplified analog signal into a digital temperature signal.

[0075] The S4 temperature compensation module 6 synchronously acquires the ambient temperature or the initial temperature of the liquid and performs drift compensation on the digital temperature signal to obtain a compensated stable temperature difference ΔT.

[0076] S5 data processing unit 5 executes the thermal diffusion model Q=K×(ΔT / Δt)×(1 / ρCp), calculates the instantaneous flow rate, and integrates the instantaneous flow rate over time to obtain the cumulative flow rate;

[0077] The S6 display unit 7 or communication interface outputs the instantaneous flow rate and / or cumulative flow rate to the local display and / or host computer system.

[0078] Specifically, firstly, the constant current source circuit 401 drives the heating resistor 301 with a constant power of 0.3 to 1 watt, establishing an initial transient thermal diffusion field within the flow channel of pipe 1. Then, the temperature sensing resistor 302, located 1 to 3 millimeters downstream of the heating resistor 301, begins to collect the temperature changes caused by the liquid flow and converts them into a weak resistance signal. This weak signal then enters a high-precision signal processing link: it is amplified by a high-precision operational amplifier 402, and then converted into a high-resolution digital temperature signal by a 24-bit analog-to-digital converter (ADC) 403. Simultaneously, the temperature compensation module 6 acquires the temperature signal from a reference temperature sensor located on the outer wall of pipe 1 or upstream of the liquid. The system measures the ambient temperature or the initial temperature of the liquid and uses digital filtering and mapping algorithms to dynamically compensate for the drift of the digital temperature signal, ultimately outputting a corrected and stable temperature difference ΔT. The data processing unit 5 then uses this compensated ΔT to execute the core heat diffusion model Q=K×(ΔT / Δt)×(1 / ρCp) to accurately calculate the instantaneous flow rate of the liquid. Finally, the system outputs the processed instantaneous flow rate and cumulative flow rate data to the local display for on-site monitoring, or uploads them to the host computer system for remote data acquisition and system control, thereby completing a complete and closed-loop measurement task from physical sensing to data output.

[0079] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0080] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the spirit and scope of the technical solution of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A liquid flow detection system based on a thin-film thermistor, comprising: Pipes are used to transport the liquid to be tested. The sensor body is installed on the pipe wall of the pipeline; A sensing probe is disposed at the bottom of the sensor body and extends into the flow channel of the pipe. The sensing probe includes a heating resistor as a heating element and a temperature measuring resistor as a temperature measuring element, with the temperature measuring resistor located downstream of the heating resistor. A signal processing circuit board is disposed inside or outside the sensor body and is electrically connected to the heating resistor and the temperature measuring resistor for acquiring and processing temperature signals. The data processing unit is communicatively connected to the signal processing circuit board and is used to calculate the instantaneous flow rate and / or cumulative flow rate of the liquid based on the temperature difference between the heating resistor and the temperature measuring resistor and the time of change of the temperature difference, combined with the thermal diffusion algorithm.

2. The liquid flow detection system based on a thin-film thermistor according to claim 1, characterized in that, Both the heating resistor and the temperature measuring resistor are thin-film thermistors manufactured using MEMS technology, and they are arranged in parallel on the substrate of the sensing probe with a spacing of 1-3 mm.

3. The liquid flow detection system based on a thin-film thermistor according to claim 1, characterized in that, The signal processing circuit board integrates: A constant current source circuit is used to provide a constant heating power of 0.3-1W to the heating resistor; A high-precision operational amplifier is used to amplify the weak signal from the temperature sensing resistor; A 24-bit analog-to-digital converter (ADC) is used to convert amplified analog signals into digital signals.

4. The liquid flow detection system based on a thin-film thermistor according to claim 1, characterized in that, It also includes a temperature compensation module, which is configured to compensate for the measured values ​​of the heating resistor and / or the temperature measuring resistor by acquiring the ambient temperature or the initial temperature of the liquid, so as to eliminate the influence of ambient temperature fluctuations on the accuracy of flow measurement.

5. A liquid flow detection system based on a thin-film thermistor according to claim 1, characterized in that, The data processing unit internally stores a flow calculation program, which executes the following calculation model: Q = K × (ΔT / Δt) × (1 / ρCp) Where Q is the volumetric flow rate, K is the sensor constant obtained through calibration, ΔT is the stable temperature difference between the heating resistor and the temperature measuring resistor, Δt is the time required to reach the stable temperature difference or the unit sampling time, ρ is the preset liquid density parameter, and Cp is the preset liquid specific heat capacity parameter.

6. The liquid flow detection system based on a thin-film thermistor according to claim 1, characterized in that, It also includes a display unit for displaying traffic data locally or transmitting traffic data to a host computer system.

7. A detection method based on the liquid flow detection system according to any one of claims 1-6, characterized in that, Includes the following steps: The S1 constant current source circuit drives the heating resistor with a constant power of 0.3-1W, so that the induction probe establishes a transient thermal diffusion field in the pipe channel. The S2 temperature sensing resistor collects the temperature change caused by the liquid flow 1-3mm downstream of the heating resistor and outputs a weak resistance signal. The S3 high-precision operational amplifier amplifies the weak resistance signal, and the 24-bit ADC converts the amplified analog signal into a digital temperature signal. The S4 temperature compensation module synchronously acquires the ambient temperature or the initial temperature of the liquid and performs drift compensation on the digital temperature signal to obtain a compensated stable temperature difference ΔT. The S5 data processing unit executes the thermal diffusion model Q=K×(ΔT / Δt)×(1 / ρCp) to calculate the instantaneous flow rate, and then integrates the instantaneous flow rate over time to obtain the cumulative flow rate; The S6 display unit or communication interface outputs the instantaneous flow rate and / or cumulative flow rate to the local display and / or host computer system.

8. The liquid flow rate detection method according to claim 7, characterized in that, In step S4, the temperature compensation module collects the ambient temperature or the initial temperature of the liquid in real time through a reference temperature sensor installed on the outer wall of the pipe or upstream of the liquid, and uses a digital filtering and mapping algorithm to dynamically correct ΔT, thereby eliminating the zero-point offset of the flow rate caused by fluctuations in ambient temperature.

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