High-precision conductivity measurement system and method based on multi-layer sensor and temperature and pressure cooperative compensation

Abstract

The invention relates to the technical field of industrial measurement and sensing, in particular to a high-precision conductivity measurement system and method based on multi-layer sensors and temperature and pressure cooperative compensation, and adopts a differentiated path of'weak signal layer + strong signal layer 'to realize full-layer signal precise adaptation; a temperature and pressure interaction item and a quadratic item are introduced to construct a coupling model, and a dual-core architecture of main controller algorithm customization and secondary controller compensation execution is matched, so that the problems of temperature and pressure coupling drift and real-time performance are solved. Meanwhile, a 0.01% 1PPM precision impedance conversion module and dynamic gain conditioning are adopted, so that high-precision impedance matching between the sensor and a rear-end circuit is realized, and signal distortion is reduced; 2-6 signals of a coverage layer are polled through an analog switch period, an interlayer correction coefficient is introduced to adapt to interlayer differences, and the measurement consistency of the whole layer is improved; and finally, the device has the functions of fault self-diagnosis, sliding average filtering window adjustment, polling mode self-definition and the like, and the flexibility and reliability of the device are enhanced.

Description

Technical Field

[0001] This invention relates to the field of industrial measurement and sensing technology, specifically a high-precision conductivity measurement system and method based on multi-layer sensors and temperature and pressure collaborative compensation. Background Technology

[0002] In the field of conductivity measurement, multilayer sensors are widely used due to their advantage of covering multi-dimensional media characteristics. However, existing technologies have significant drawbacks: First, the signal processing path uses a single amplification mechanism, which is difficult to adapt to the signal strength differences between different sensor layers, leading to weak signal distortion; second, temperature and pressure drift compensation relies on a single controller, lacking a collaborative feedback link, resulting in insufficient real-time compensation; third, the impedance matching accuracy between the sensor and the back-end circuit is low (typically only 1%), causing signal distortion; fourth, without multi-path preprocessing of multilayer signals, the measurement repeatability error is as high as ±3% or more. Furthermore, traditional separate temperature and pressure compensation cannot effectively counteract coupling effects, further limiting measurement accuracy.

[0003] Therefore, there is an urgent need for a conductivity measurement solution that is compatible with multi-layer sensors, has dual-controller collaborative compensation, and high impedance matching accuracy. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing conductivity measurement technologies, such as large plate-level offset and insufficient accuracy due to the influence of temperature and pressure. It provides a high-precision conductivity measurement system and method with high hardware integration, effective compensation algorithm, and full signal chain temperature and pressure compensation.

[0005] To achieve the above objectives, the technical solution specifically adopted by the present invention is as follows: A high-precision conductivity measurement system based on multi-layer sensors and temperature-pressure co-compensation includes: Multilayer conductivity sensor: contains at least 7 detection units, with layers 1 and 7 connected to reference ground, and layers 2-6 outputting electrical signals and receiving square wave excitation signals from the excitation current module; The signal preprocessing module includes a parallel-connected capacitor DC blocking unit, a differential amplification unit, and an instrumentation amplification unit. The capacitor DC blocking module has two inputs connected to the outputs of layers 2-3 and 5-6 of the multilayer conductivity sensor to suppress DC interference. The differential amplification module also has two inputs connected to the outputs of the two capacitor DC blocking modules to amplify weak electrical signals. The differential instrumentation amplification module has one input connected to the output of layer 4 of the multilayer conductivity sensor to directly amplify the core layer signal. Multi-channel gating module: a three-channel analog switch, with its input terminals connected to the output terminals of two differential amplifier modules and a differential instrument amplifier module, respectively, for gating target signals; Data acquisition module: ADC module, the input terminal is connected to the output terminal of a three-channel analog switch, used to convert analog signals into digital signals; Dual-core control module: includes a main controller and a secondary controller with interconnected communication; the main controller (STM32L0) has its input connected to the output of the ADC module and is connected to the secondary controller through a communication interface, used to run the temperature and pressure compensation algorithm, control analog switches, and upload data; the secondary controller (STM32L0) has its input connected to the main controller and its output connected to the DAC module, used to collaboratively execute compensation instructions; Temperature and pressure sensing module: It adopts an on-board temperature and pressure sensing unit (BMP280), and the output is connected to the spare input of a three-channel analog switch for synchronous acquisition of ambient temperature T and pressure P; The dynamic compensation execution module includes a DAC unit, a signal conditioning unit, and a high-precision impedance transformation unit connected in sequence, with the output terminal fed back to the sensor; wherein, the DAC module has its input terminal connected to the secondary controller; the signal conditioning module has its input terminal connected to the output terminal of the DAC module. Impedance transformation module (accuracy 0.01% 1PPM): The input terminal is connected to the output terminal of the signal conditioning module, and the output terminal is connected to the multilayer conductivity sensor for dynamic adjustment of sensor impedance matching. Power supply module: Provides stable operating voltage for each functional module.

[0006] This invention also provides a high-precision conductivity measurement method based on multilayer sensors and temperature-pressure co-compensation, comprising the following steps: S1: Hardware Initialization and Coefficient Calibration 1.1 Configure the communication interface of the master / secondary controller, the sampling frequency of the ADC, the output range of the DAC, and calibrate the gating logic of the analog switch; 1.2 In a standard thermobaric chamber, multiple sets of standard conductivity σ_std and original sampled value σ0_cal under temperature and pressure (T_cal, P_cal) are collected by multi-layer conductivity sensors. The drift Δσ_cal=σ_std-σ0_cal is calculated. The coefficients of the temperature-pressure coupling compensation model Δσ=aT+bP+cTP+dT²+eP² are obtained by fitting with the least squares method. S2: Real-time signal acquisition and preprocessing 2.1 The excitation current module outputs a square wave excitation signal to the multilayer conductivity sensor; 2.2 The output signal of the multilayer conductivity sensor is blocked by capacitor and amplified by differential / instrumentation. Then, the target signal is selected by a three-channel analog switch, and the T and P signals of the temperature and pressure sensing unit on the board are collected synchronously. 2.3 The ADC module converts the selected signal into a digital signal and transmits it to the main controller; 2.4 Perform a 5-point moving average filter on the collected σ0, T, and P to obtain σ0', T', and P'; S3: Temperature and Pressure Co-compensation Calculation 3.1 The main controller calls the pre-stored compensation coefficients and substitutes them into the model to calculate the drift compensation amount Δσ=aT'+bP'+cT'P'+d(T')²+e(P')²; 3.2 Calculate the compensated conductivity σ = σ0' + Δσ; S4: Compensation Execution and Data Output 4.1 The main controller sends a compensation command to the secondary controller, and the secondary controller drives the DAC module to output the corresponding voltage signal; 4.2 After the voltage signal is processed by the signal conditioning module, it is input to the impedance transformation module to dynamically adjust the impedance matching of the multilayer conductivity sensor; 4.3 The main controller uploads the compensated σ, T', and P' to the host computer; S5: Fault Diagnosis: Real-time monitoring of the operating status of ADC, DAC and analog switches, triggering an alarm when abnormalities occur.

[0007] This invention has the following characteristics and beneficial effects: 1) Multi-layer signal adaptation: Multi-path preprocessing improves the amplification accuracy of signals from different layers by 20%; 2) Compensation Real-time Performance: The dual controllers work together to ensure that the sampling-compensation delay is ≤1ms; 3) Impedance matching accuracy: 0.01% impedance transformation per 1PPM results in a signal distortion rate ≤0.1%; 4) Measurement accuracy: After temperature and pressure co-compensation, the error is ≤ ±0.5%, which is 6 to 10 times higher than the traditional solution. Attached Figure Description

[0008] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a block diagram of a high-precision conductivity measurement system based on multi-layer sensors and temperature and pressure synergistic compensation, according to an embodiment of the present invention.

[0009] Figure 2 This is a flowchart of a high-precision conductivity measurement method based on multi-layer sensors and temperature and pressure synergistic compensation, according to an embodiment of the present invention. Detailed Implementation

[0010] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0011] The first aspect of this invention is to provide a high-precision conductivity measurement system based on multi-layer sensors and temperature-pressure co-compensation, comprising: Multilayer conductivity sensor: contains at least 7 detection units, with layers 1 and 7 connected to reference ground, and layers 2-6 outputting electrical signals and receiving square wave excitation signals from the excitation current module; The signal preprocessing module includes a parallel-connected capacitor DC blocking unit, a differential amplification unit, and an instrumentation amplification unit. The capacitor DC blocking module has two inputs connected to the outputs of layers 2-3 and 5-6 of the multilayer conductivity sensor to suppress DC interference. The differential amplification module also has two inputs connected to the outputs of the two capacitor DC blocking modules to amplify weak electrical signals. The differential instrumentation amplification module has one input connected to the output of layer 4 of the multilayer conductivity sensor to directly amplify the core layer signal. Multi-channel gating module: a three-channel analog switch, with its input terminals connected to the output terminals of two differential amplifier modules and a differential instrument amplifier module, respectively, for gating target signals; Data acquisition module: ADC module, the input terminal is connected to the output terminal of a three-channel analog switch, used to convert analog signals into digital signals; Dual-core control module: includes a main controller and a secondary controller with interconnected communication; the main controller (STM32L0) has its input connected to the output of the ADC module and is connected to the secondary controller through a communication interface, used to run the temperature and pressure compensation algorithm, control analog switches, and upload data; the secondary controller (STM32L0) has its input connected to the main controller and its output connected to the DAC module, used to collaboratively execute compensation instructions; Temperature and pressure sensing module: It adopts an on-board temperature and pressure sensing unit (BMP280), and the output is connected to the spare input of a three-channel analog switch for synchronous acquisition of ambient temperature T and pressure P; The dynamic compensation execution module includes a DAC unit, a signal conditioning unit, and a high-precision impedance transformation unit connected in sequence, with the output terminal fed back to the sensor; wherein, the DAC module has its input terminal connected to the secondary controller; the signal conditioning module has its input terminal connected to the output terminal of the DAC module. Impedance transformation module (accuracy 0.01% 1PPM): The input terminal is connected to the output terminal of the signal conditioning module, and the output terminal is connected to the multilayer conductivity sensor for dynamic adjustment of sensor impedance matching. Power supply module: Provides stable operating voltage for each functional module.

[0012] Figure 1This invention presents a high-precision measurement and temperature-pressure coordinated compensation system for a multilayer conductivity sensor. The core logic of this system is a closed-loop chain of "signal acquisition - preprocessing - conversion - control - compensation". The functions and processes of each module are as follows: 1. Signal Acquisition and Preprocessing: On the left is a 7-layer conductivity sensor (layers 1 and 7 are grounded) that receives square wave excitation current; the signals of layers 2-3 and 5-6 are preprocessed by “capacitor DC blocking (filtering out DC interference) + differential amplification (enhancing weak signals)”, and the signal of layer 4 is preprocessed by “differential instrument amplification (adapting strong signals)” to achieve differentiated adaptation of multi-layer signals.

[0013] 2. Signal selection and conversion: The three-channel analog switch switches the above three pre-processed signals and simultaneously connects the environmental parameter signals from the "onboard temperature and pressure sensor", which are then sent to the ADC to complete analog-to-digital conversion (converting analog signals into digital signals).

[0014] 3. Control and Compensation: The main controller (STM32L0) receives ADC data and uploads the conductivity result to the host computer. On the other hand, it sends compensation commands to the secondary controller (same model STM32L0) through the communication link. The secondary controller drives the DAC output signal, which is then fed back to the sensor after "signal conditioning (filtering / gain adjustment) + high-precision impedance transformation (0.01% 1PPM, matching the sensor and circuit impedance)" to achieve hardware-level compensation for temperature and pressure drift.

[0015] A second aspect of this invention is to provide a high-precision conductivity measurement method based on multilayer sensors and temperature-pressure co-compensation, such as... Figure 2 As shown, it includes the following steps: S1: Hardware Initialization and Coefficient Calibration 1.1 Configure the communication interface of the master / secondary controller, the sampling frequency of the ADC, the output range of the DAC, and calibrate the gating logic of the analog switch; 1.2 In a standard thermobaric chamber, multiple sets of standard conductivity σ_std and original sampled value σ0_cal under temperature and pressure (T_cal, P_cal) are collected by multi-layer conductivity sensors. The drift Δσ_cal=σ_std-σ0_cal is calculated. The coefficients of the temperature-pressure coupling compensation model Δσ=aT+bP+cTP+dT²+eP² are obtained by fitting with the least squares method. S2: Real-time signal acquisition and preprocessing 2.1 The excitation current module outputs a square wave excitation signal to the multilayer conductivity sensor; 2.2 The output signal of the multilayer conductivity sensor is blocked by capacitor and amplified by differential / instrumentation. Then, the target signal is selected by a three-channel analog switch, and the T and P signals of the temperature and pressure sensing unit on the board are collected synchronously. 2.3 The ADC module converts the selected signal into a digital signal and transmits it to the main controller; 2.4 Perform a 5-point moving average filter on the collected σ0, T, and P to obtain σ0', T', and P'; S3: Temperature and Pressure Co-compensation Calculation 3.1 The main controller calls the pre-stored compensation coefficients and substitutes them into the model to calculate the drift compensation amount Δσ=aT'+bP'+cT'P'+d(T')²+e(P')²; 3.2 Calculate the compensated conductivity σ = σ0' + Δσ; S4: Compensation Execution and Data Output 4.1 The main controller sends a compensation command to the secondary controller, and the secondary controller drives the DAC module to output the corresponding voltage signal; 4.2 After the voltage signal is processed by the signal conditioning module, it is input to the impedance transformation module to dynamically adjust the impedance matching of the multilayer conductivity sensor; 4.3 The main controller uploads the compensated σ, T', and P' to the host computer; S5: Fault Diagnosis: Real-time monitoring of the operating status of ADC, DAC and analog switches, triggering an alarm when abnormalities occur.

[0016] In summary, this invention addresses the signal strength differences between layers of a multi-layer sensor by designing a differentiated path: a "weak signal layer (capacitive DC blocking + 100x differential amplification) + a strong signal layer (50x differential instrumentation amplification)," achieving precise signal adaptation across all layers. It introduces a temperature-pressure interaction term (TP) and quadratic terms (T², P²) to construct a coupling model, coupled with a dual-core architecture of customized main controller algorithm and compensated execution by secondary controller, solving the problems of temperature-pressure coupling drift and real-time performance. Simultaneously, a high-precision impedance feedback link employs a 0.01% 1PPM precision impedance transformation module and dynamic gain conditioning to achieve high-precision impedance matching between the sensor and the back-end circuit, reducing signal distortion. By periodically polling the signals of layers 2-6 using analog switches, inter-layer correction coefficients are introduced to adapt to inter-layer differences, improving measurement consistency across all layers. Finally, it includes functions such as fault self-diagnosis (ADC / DAC / analog switch status monitoring), adjustable moving average filter window (3-11 points), and customizable polling mode, enhancing the device's flexibility and reliability.

[0017] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-precision conductivity measurement system based on multi-layer sensors and temperature-pressure synergistic compensation, characterized in that, include: The multilayer conductivity sensor contains at least 7 detection units, with layers 1 and 7 connected to the reference ground, and layers 2-6 outputting electrical signals and receiving square wave excitation signals output by the excitation current module. The split-path signal preprocessing module includes a parallel-connected capacitor DC blocking unit, differential amplifier unit, and instrument amplifier unit; The multi-channel gating module uses a three-channel analog switch, with its input terminals connected to the output terminals of two differential amplifier modules and a differential instrument amplifier module, respectively, to select the target signal. The data acquisition module includes an ADC unit, whose input is connected to the output of a three-channel analog switch, used to convert analog signals into digital signals. The dual-core control module includes a main controller and a secondary controller that are interconnected. The main controller receives ADC data and runs a temperature and pressure co-compensation algorithm, controls analog switches and uploads data, while the secondary controller executes dynamic compensation commands. The temperature and pressure sensing module has its output connected to the spare input of a three-channel analog switch for synchronous acquisition of ambient temperature T and pressure P. The dynamic compensation execution module includes a DAC unit, a signal conditioning unit, and a high-precision impedance transformation unit connected in sequence, and its output is fed back to the sensor. The impedance transformation module has its input end connected to the output end of the signal conditioning module, and its output end connected to a multilayer conductivity sensor for dynamically adjusting the sensor impedance matching. The power supply module provides a stable operating voltage for each functional module.

2. The high-precision conductivity measurement system based on multi-layer sensors and temperature-pressure synergistic compensation as described in claim 1, characterized in that, The path splitting signal preprocessing module includes: Two-channel capacitor DC blocking module: The input terminals are connected to the output terminals of layers 2-3 and 5-6 of the multilayer conductivity sensor, respectively, to suppress DC interference; Two-channel differential amplifier module: The input terminal is connected to the output terminal of two-channel capacitor DC blocking module to enhance weak electrical signals; Differential instrument amplification module: The input end is connected to the layer 4 output end of the multilayer conductivity sensor, which is used to directly amplify the core layer signal.

3. The high-precision conductivity measurement system based on multi-layer sensors and temperature-pressure synergistic compensation as described in claim 1, characterized in that, The temperature and pressure sensing module uses an on-board temperature and pressure sensing unit BMP280.

4. A high-precision conductivity measurement method based on multi-layer sensors and temperature-pressure synergistic compensation, characterized in that, Includes the following steps: S1: Hardware Initialization and Coefficient Calibration S1.1 Configure the communication interface of the master / secondary controller, the sampling frequency of the ADC, the output range of the DAC, and calibrate the gating logic of the analog switch; S1.2 In a standard thermobaric chamber, multiple sets of standard conductivity and original sampled values ​​under temperature and pressure are collected by multi-layer conductivity sensors. The drift is calculated, and the coefficients of the temperature-pressure coupling compensation model are obtained by fitting using the least squares method. S2: Real-time signal acquisition and preprocessing The S2.1 excitation current module outputs a square wave excitation signal to the multilayer conductivity sensor; The output signal of the S2.2 multilayer conductivity sensor is blocked by capacitor and amplified by differential / instrumentation. Then, the target signal is selected by a three-channel analog switch, and the T and P signals of the temperature and pressure sensing unit on the board are collected simultaneously. The S2.3ADC module converts the selected signal into a digital signal and transmits it to the main controller; S2.4 performs a 5-point moving average filter on the collected σ0, T, and P to obtain σ0', T', and P'; S3: Temperature and Pressure Co-compensation Calculation S3.1 The main controller calls the pre-stored compensation coefficients and substitutes them into the model to calculate the drift compensation amount Δσ=aT'+bP'+cT'P'+d(T')²+e(P')²; S3.2 Calculate the compensated conductivity σ = σ0' + Δσ; S4: Compensation Execution and Data Output The S4.1 master controller sends a compensation command to the secondary controller, and the secondary controller drives the DAC module to output the corresponding voltage signal. After the voltage signal of S4.2 is processed by the signal conditioning module, it is input to the impedance transformation module to dynamically adjust the impedance matching of the multilayer conductivity sensor. The S4.3 main controller uploads the compensated σ, T', and P' to the host computer; S5: Fault Diagnosis: Real-time monitoring of the operating status of ADC, DAC and analog switches, triggering an alarm when abnormalities occur.

5. The high-precision conductivity measurement method based on multi-layer sensors and temperature-pressure synergistic compensation as described in claim 4, characterized in that, In step S2, within a standard thermobaric chamber, multiple sets of standard conductivity σ_std and original sampled values ​​σ0_cal under temperature and pressure (T_cal, P_cal) are collected using multi-layer conductivity sensors. The drift amount Δσ_cal = σ_std - σ0_cal is calculated, and the coefficients of the thermobaric coupling compensation model Δσ = aT + bP + cTP + dT² + eP² are obtained by fitting using the least squares method.

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