A soil multi-parameter composite in-situ measuring sensor device

Abstract

The utility model belongs to the technical field of soil monitoring, more specifically, relate to a kind of soil multi-parameter composite in-situ measurement sensor device, comprising: multifunctional probe main part, thermal pulse excitation circuit, dielectricity / hydration measurement circuit, temperature and conductivity detection circuit, signal processing circuit and protective packaging shell;The multifunctional probe main part is respectively thermal pulse emission probe A, multifunctional measurement probe B and dielectric spectrum emission probe C from left to right, wherein: thermal pulse emission probe A is embedded with nichrome heating wire inside;Multifunctional measurement probe B upper portion is integrated thermocouple array, and terminal is equipped with dielectric spectrum receiving module;Dielectric spectrum emission probe C bottom is equipped with sweep-frequency high-frequency signal excitation module, and with probe B to form non-common point capacitance coupling path.The utility model can synchronously collect the following seven soil parameters: volume moisture content, temperature, thermal diffusivity, conductivity, bulk density, porosity and texture classification information.

Description

Technical Field

[0001] This utility model belongs to the technical field of soil monitoring, and more specifically, relates to a soil multi-parameter composite in-situ measurement sensor device. Background Technology

[0002] In agricultural production and greenhouse management, the demand for real-time monitoring of multiple physical and chemical parameters such as soil moisture, temperature, salinity, electrical conductivity, bulk density, porosity, and texture is increasing. However, most existing soil sensing technologies can only measure a single parameter, making it difficult to simultaneously acquire multiple core soil condition information at the same location. Currently, there are sensors on the market that integrate soil moisture content, electrical conductivity, and temperature measurement (such as Campbell Scientific's SoilVUE™10), but these are mainly imported, have high costs, and cannot simultaneously acquire deeper physical information such as soil thermal properties and structural parameters. Especially in precision agriculture scenarios, soil bulk density, porosity, and texture are directly related to root growth and water and fertilizer regulation, but existing sensing methods still rely on indirect estimation or offline measurement for these parameters, resulting in significant monitoring errors. Therefore, developing an in-situ sensing device that can integrate the measurement of seven core indicators—soil moisture, temperature, thermal properties, electrical conductivity, bulk density, porosity, and texture classification—is of significant practical importance. Utility Model Content

[0003] This invention aims to overcome at least one of the defects of the prior art and provide a multi-parameter composite in-situ measurement sensor device for soil, so as to solve the problem that existing sensors cannot acquire multiple soil parameters at the same time. It can simultaneously collect the following seven soil parameters: volumetric water content, temperature, thermal diffusivity, electrical conductivity, bulk density, porosity and texture classification information.

[0004] The detailed technical solution of this utility model is as follows: A multi-parameter composite in-situ measurement sensor device for soil includes: a multi-functional probe body, a main control circuit board, and a protective encapsulation shell. The main control circuit board is embedded inside the protective encapsulation shell and is wired and connected to the multi-functional probe body. The multifunctional probe body consists of three metal probes of equal length arranged side by side, from left to right: thermal pulse emission probe A, multifunctional measurement probe B, and dielectric spectrum emission probe C, which are vertically arranged inside the protective encapsulation shell. The thermal pulse emission probe A has a nickel-chromium alloy heating wire embedded inside; The multifunctional measurement probe B integrates a thermocouple array in the upper part and has a dielectric spectrum receiving module at the end. The bottom of the dielectric spectrum emission probe C is equipped with a sweep frequency high-frequency signal excitation module, which forms a non-common point capacitive coupling path with probe B; The main control circuit board includes a thermal pulse excitation circuit, a dielectric / water content measurement circuit, a temperature and conductivity detection circuit, and a signal processing circuit.

[0005] Preferably, the distance between probe A and probe B is 5–10 mm, and the distance between probe B and probe C is 15–30 mm.

[0006] Preferably, the protective enclosure is made of high-strength ABS material, with a corrosion-resistant coating sprayed on the surface and epoxy resin potting inside.

[0007] Preferably, the thermal pulse excitation circuit adopts a constant current source control method, with standard pulse parameters set to 2A current and 1.5-second pulse width, and the pulse amplitude and time are adjusted by MCU digital control.

[0008] Preferably, the dielectric / water content measurement circuit consists of a high-frequency oscillator, a drive stage, a response acquisition stage, and a signal demodulation unit; the high-frequency oscillator outputs a sweep excitation signal with a center frequency of 40MHz, and the frequency range is set to 10MHz–80MHz.

[0009] Preferably, the temperature and conductivity detection circuit includes a high-impedance differential amplifier for acquiring the signal output by the thermocouple array in electrode B and constructing a temperature-time curve, with a temperature acquisition accuracy better than ±0.2℃.

[0010] Preferably, electrode B and electrode C constitute a four-electrode conductivity detection circuit, which applies a low-frequency AC signal with a fixed amplitude, collects the response voltage amplitude, and calculates the conductivity of the soil aqueous solution.

[0011] Preferably, the signal processing circuit uses a 24-bit high-resolution ADC for sampling, has a built-in temperature compensation model, and supports RS485 and SDI-12 protocols.

[0012] Preferably, the signal processing circuit can be an FPGA module to implement multi-channel parallel filtering and data stream scheduling.

[0013] Compared with the prior art, the beneficial effects of this utility model are as follows: (1) The present invention has a high degree of parameter integration: it adopts a three-probe structure to achieve in-situ synchronous measurement of seven core indicators such as soil moisture, temperature, thermal diffusivity, electrical conductivity, bulk density, porosity and texture type at a single probe point. It can obtain a variety of soil characteristics by relying only on two physical measurement principles: dielectric spectrum and thermal pulse, thus avoiding spatial conflicts and data asynchrony caused by the deployment of multiple sensors.

[0014] (2) The present utility model has strong structural innovation: three electrodes are arranged side by side, and perform the tasks of thermal excitation, multi-function reception and dielectric excitation respectively. Through functional decoupling and path separation, the problems of signal interference and functional overlap in traditional multi-parameter sensors are eliminated. The longitudinal thermocouple array in the probe B is combined with the bottom dielectric receiving module, which supports obtaining soil thermal response and dielectric spectrum data along the depth dimension, and enhances the longitudinal resolution and data accuracy.

[0015] (3) The present utility model is convenient to install with little disturbance: the whole sensor adopts a slender inserted design, which is suitable for portable field deployment or long-term fixed installation in greenhouses. The probe has a compact, firm and reliable structure, which causes minimal disturbance to undisturbed soil when inserted into the soil, and is suitable for long-term operation in root zone or substrate environment.

[0016] (4) The present utility model has high measurement accuracy and stability: based on the dual sampling mechanism of frequency-sweeping dielectric measurement and thermal pulse method, combined with multi-point thermocouple array temperature measurement and filter isolation circuit, accurate measurement and real-time temperature drift compensation in different soil environments are realized. Through the optimization of experimental calibration algorithm, the data stability and credibility in high salinity and high temperature scenarios are significantly enhanced. Description of Drawings

[0017] Figure 1 is a structural diagram of the composite in-situ measurement sensor device for soil multiple parameters according to the present utility model; In the figure: 1, main control circuit board; 2, nichrome heating wire; 3, thermocouple array; 4, dielectric spectrum receiving module; 5, frequency-sweeping high-frequency signal excitation module. Detailed Description of Embodiments

[0018] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0019] Embodiment 1, referring to Figure 1 , the present embodiment provides a composite in-situ measurement sensor device for soil multiple parameters, comprising: a multi-functional probe main body, a main control circuit board 1 and a protective packaging housing, wherein the main control circuit board 1 is embedded inside the protective packaging housing and connected to the multi-functional probe main body through wiring, forming an integrated sensing system with compact structure and integrated functions; said multi-functional probe main body is composed of three metal probes of equal length arranged side by side, which are respectively a heat pulse emitting probe A, a multi-functional measuring probe B and a dielectric spectrum emitting probe C from left to right, and are vertically arranged inside the protective packaging housing, wherein: a nichrome heating wire 2 is embedded inside the heat pulse emitting probe A, which is used for applying short-time high-current pulses to provide thermal excitation to the soil; The upper part of the multifunctional measurement probe B integrates multiple thermocouple arrays 3 to collect temperature-time response at different distances and invert soil thermal diffusivity; the end is equipped with a dielectric spectrum receiving module 4 to receive the transmission response of high-frequency excitation signals in the soil and invert dielectric properties and related physical parameters. The bottom of the dielectric spectrum emission probe C is equipped with a frequency sweeping high-frequency signal excitation module 5, which forms a non-common point capacitive coupling path with the probe B, and is used to inject electromagnetic waves into the soil to trigger the dielectric response. The distance between probe A and probe B: see Figure 1 D1 in the equation controls the thermal pulse path length, typically around 5–10 mm, to ensure that the thermal excitation forms a measurable conduction gradient in the soil, while avoiding excessive heat diffusion that could lead to response attenuation. The distance between probes B and C: see D2 in the structural diagram. It forms a dielectric excitation-receiving path. The typical value is about 15–30 mm, which facilitates the propagation of the dielectric field in a sufficient volume of soil, thereby improving the measurement uniformity and response amplitude.

[0020] The main control circuit board 1 includes a thermal pulse excitation circuit, a dielectric / water content measurement circuit, a temperature and conductivity detection circuit, and a signal processing circuit, wherein: The thermal pulse excitation circuit applies a fixed amplitude current pulse to the nickel-chromium alloy heating wire 2 inside probe A through a constant current source. The standard pulse parameters are set to 2A current and 1.5-second pulse width to achieve short-time thermal excitation. The pulse parameters are determined based on the typical soil thermal diffusion characteristics and thermal inertia time constant, which can form an observable heat conduction gradient without damaging the soil structure, while avoiding interference caused by overheating. At the same time, the thermal pulse excitation circuit allows the pulse amplitude and time to be adjusted by MCU digital control according to the set sampling period, so as to achieve adaptive excitation intensity adjustment under soil environments with different heat capacities. The dielectric / water content measurement circuit consists of a high-frequency oscillator, a drive stage, a response acquisition stage, and a signal demodulation unit. The high-frequency oscillator outputs a sweep excitation signal with a center frequency of 40 MHz, and the frequency range is set to 10 MHz–80 MHz. This frequency band has been experimentally selected to have a good soil moisture content spectrum response and minimal impact on non-target factors such as salinity and temperature. The sweep excitation signal is injected into the soil medium by the sweep high-frequency signal excitation module 5 of electrode C. The response signal is formed through the equivalent capacitance of the soil. After being received by the dielectric spectrum receiving module 4 of electrode B, the response amplitude and phase information are demodulated by the lock-in amplifier. The equivalent relative permittivity is further calculated, and the volumetric water content is inverted. The measurement algorithm adopts the "dispersion frequency fitting" model, which effectively improves the measurement robustness under high salinity and temperature change conditions. The temperature and conductivity detection circuit acquires the signal output from the thermocouple array 3 in electrode B through a high-impedance differential amplifier, constructs a temperature-time curve, and calculates the soil thermal diffusivity. The temperature acquisition accuracy is better than ±0.2℃. At the same time, electrode B and electrode C form a quadrupole conductivity detection circuit, apply a fixed amplitude low-frequency AC signal (1 kHz, 50 mVpp), and acquire the response voltage amplitude to calculate the conductivity of the soil aqueous solution. This design avoids electrode polarization and improves accuracy and stability in the low conductivity range.

[0021] The signal processing circuit is used to preprocess all sensing signals through a low-noise operational amplifier, sample them by a 24-bit high-resolution ADC, and then integrate the data into the central control MCU. It also has a built-in temperature compensation model to correct the dielectric constant measurement value in real time based on the ambient temperature measured by the thermocouple. The signal processing circuit can optionally use an FPGA module to realize multi-channel parallel filtering and data stream scheduling, support real-time output of processing results, and the communication interface supports RS485 and SDI-12 protocols.

[0022] The protective enclosure is made of high-strength ABS material, with a corrosion-resistant coating sprayed on the surface and epoxy resin potting inside, providing good mechanical strength and protection capabilities, suitable for long-term buried monitoring scenarios in the field.

[0023] The method for collecting multiple soil parameters using sensor devices is as follows: This device employs a three-probe parallel structure, where probe A is a thermal pulse transmitting probe, probe B is a multifunctional receiving probe, and probe C is a dielectric spectrum transmitting probe. The three probes are physically spaced and electrically isolated to effectively separate the thermal pulse and high-frequency signal paths, avoiding signal coupling interference problems found in traditional two-electrode structures. Multiple thermocouple nodes are embedded longitudinally within probe B, forming a high-density temperature receiving array for simultaneously measuring temperature changes at multiple soil depths, obtaining the complete heat diffusion path. Simultaneously, a dielectric spectrum receiving module is integrated at the probe's end to respond to the sweep frequency excitation signal emitted from probe C.

[0024] In the actual measurement process, a thermal pulse signal is injected into the soil from probe A, conducts heat to probe B, and a thermocouple array records the temperature rise curve and temperature gradient, thus retrieving the soil's thermal diffusivity and temperature distribution. A high-frequency excitation signal is emitted from probe C, and the spectral response is received at the end of probe B to obtain the soil's dielectric properties and retrieve relevant parameters. The two excitation signals operate at significantly different frequency bands (DC / low frequency vs. high frequency), and are uniformly scheduled by the controller, supporting parallel operation within the same measurement cycle. The measurement cycle does not exceed 3 seconds, and all signal channels are equipped with filtering, shielding, and isolation measures to ensure data accuracy and spatiotemporal consistency.

Claims

1. A soil multi-parameter composite in-situ measurement sensor device, characterized in that, include: The multi-functional probe body, the main control circuit board (1) and the protective encapsulation shell are embedded inside the protective encapsulation shell and connected to the multi-functional probe body. The multifunctional probe body consists of three metal probes of equal length arranged side by side, from left to right: thermal pulse emission probe A, multifunctional measurement probe B, and dielectric spectrum emission probe C, which are vertically arranged inside the protective encapsulation shell. The thermal pulse emission probe A has a nickel-chromium alloy heating wire embedded inside (2); The upper part of the multifunctional measurement probe B integrates a thermocouple array (3), and the end is equipped with a dielectric spectrum receiving module (4). The bottom of the dielectric spectrum emission probe C is provided with a sweep frequency high-frequency signal excitation module (5), which forms a non-common point capacitive coupling path with probe B; The main control circuit board (1) includes a thermal pulse excitation circuit, a dielectric / water content measurement circuit, a temperature and conductivity detection circuit, and a signal processing circuit.

2. The soil multi-parameter composite in-situ measurement sensor device according to claim 1, characterized in that, The distance between probe A and probe B is 5–10 mm, and the distance between probe B and probe C is 15–30 mm.

3. The soil multi-parameter composite in-situ measurement sensor device according to claim 1, characterized in that, The protective enclosure is made of high-strength ABS material, with a corrosion-resistant coating sprayed on the surface and epoxy resin potting inside.

4. The soil multi-parameter composite in-situ measurement sensor device according to claim 1, characterized in that, The thermal pulse excitation circuit adopts a constant current source control method, with standard pulse parameters set to 2A current and 1.5-second pulse width. The pulse amplitude and time are adjusted by MCU digital control.

5. The soil multi-parameter composite in-situ measurement sensor device according to claim 1, characterized in that, The dielectric / water content measurement circuit consists of a high-frequency oscillator, a driver stage, a response acquisition stage, and a signal demodulation unit; the high-frequency oscillator outputs a sweep excitation signal with a center frequency of 40MHz, and the frequency range is set to 10MHz–80MHz.

6. The soil multi-parameter composite in-situ measurement sensor device according to claim 1, characterized in that, The temperature and conductivity detection circuit includes a high-impedance differential amplifier, which is used to acquire the signal output by the thermocouple array in electrode B and construct a temperature-time curve. The temperature acquisition accuracy is better than ±0.2℃.

7. The soil multi-parameter composite in-situ measurement sensor device according to claim 6, characterized in that, Electrode B and electrode C constitute a four-electrode conductivity detection circuit, which applies a low-frequency AC signal with a fixed amplitude, collects the response voltage amplitude, and calculates the conductivity of the soil aqueous solution.

8. The soil multi-parameter composite in-situ measurement sensor device according to claim 1, characterized in that, The signal processing circuit uses a 24-bit high-resolution ADC for sampling, has a built-in temperature compensation model, and supports RS485 and SDI-12 protocols.

9. The soil multi-parameter composite in-situ measurement sensor device according to claim 1, characterized in that, The signal processing circuit uses an FPGA module to implement multi-channel parallel filtering and data stream scheduling.

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