Soil acid and alkali content detection device

Abstract

The utility model provides a soil acid and alkali content detection device. The soil acid-base content detection device comprises a soil PH value detection module, a soil humidity detection module and a controller, wherein the output end of the soil PH value detection module and the output end of the soil humidity detection module are both connected with the controller; the soil humidity detection module comprises a signal source, a coaxial cable, a detection electrode, a first peak detection circuit, a second peak detection circuit and a first subtraction circuit, the signal source is used for outputting periodic signal waves, and the first peak detection circuit is used for detecting voltage signals at the first end of the coaxial cable; the second peak detection circuit is used for detecting a voltage signal of the second end of the coaxial cable. The output end of the first peak detection circuit and the output end of the second peak detection circuit are connected to the two input ends of the first subtraction circuit respectively. The soil acidity and alkalinity detection precision can be improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of environmental detection, and in particular to a soil acid-base content detection device. Background Art

[0002] Soil testing is used to analyze and evaluate the quality and characteristics of soil. Soil testing can help us evaluate the pollution status of soil, such as the content of heavy metals and organic pollutants, which plays an important role in environmental protection and pollution control. Through soil testing, we can also understand the moisture content, nutrient content, pH value and other information of the soil, and guide agricultural production accordingly.

[0003] Among them, soil pH detection can be achieved using a soil pH detector. Currently, the detection accuracy of the soil pH detector needs to be improved. Utility Model Content

[0004] The disclosed embodiment provides a soil acid-base content detection device to solve the problem of low detection accuracy of existing soil acid-base detection instruments.

[0005] The present disclosure provides a soil acid-base content detection device, comprising:

[0006] Soil pH value detection module, used to detect soil acidity and alkalinity;

[0007] Soil moisture detection module, used to detect soil moisture;

[0008] A controller, the output end of the soil pH value detection module and the output end of the soil moisture detection module are both connected to the controller;

[0009] The soil moisture detection module includes a signal source, a coaxial cable, a detection electrode, a first peak detection circuit, a second peak detection circuit and a first subtraction circuit. The signal source is used to output a periodic signal. The first end of the coaxial cable is used to connect the signal source, and the second end of the coaxial cable is used to connect the detection electrode. The first peak detection circuit is used to detect the voltage signal at the first end of the coaxial cable, and the second peak detection circuit is used to detect the voltage signal at the second end of the coaxial cable. The output end of the first peak detection circuit is connected to the first end of the first subtraction circuit, and the output end of the second peak detection circuit is connected to the second end of the first subtraction circuit. The output end of the first subtraction circuit is the output end of the soil moisture detection module.

[0010] In an exemplary embodiment of the present disclosure, the first peak detection circuit includes a diode D1, a capacitor C1 and a resistor R3.

[0011] The anode of the diode D1 is connected to the first end of the coaxial cable, the cathode of the diode D1 is connected to the first end of the capacitor C1, the second end of the capacitor C1 is grounded, the resistor R3 is connected in parallel to both ends of the capacitor C1, and one end of the capacitor C1 is the output end of the peak detection circuit.

[0012] In an exemplary embodiment of the present disclosure, a first amplifying circuit is disposed between the first end of the coaxial cable and the first peak detection circuit.

[0013] In an exemplary embodiment of the present disclosure, a voltage follower is provided between the output end of the first peak detection circuit and the first subtraction circuit.

[0014] In an exemplary embodiment of the present disclosure, the soil acid-base content detection device further includes a soil temperature detection module, wherein the soil temperature detection module includes a thermistor, an operational amplifier U3B and a second subtraction circuit.

[0015] The non-inverting input terminal of the operational amplifier U3B is connected to the reference voltage, the inverting input terminal of the operational amplifier U3B is grounded through a resistor R14, and the output terminal of the operational amplifier U3B is connected to the inverting input terminal of the operational amplifier U3B through a thermistor feedback.

[0016] Two ends of the thermistor are respectively connected to two input ends of the second subtraction circuit, and an output end of the second subtraction circuit is connected to a controller.

[0017] In an exemplary embodiment of the present disclosure, the soil temperature detection module further includes a reference voltage module, and the reference voltage module is used to provide a reference voltage for the non-inverting input terminal of the operational amplifier U3B.

[0018] The present disclosure provides a soil acid-base content detection device, and its working principle and beneficial effects are as follows:

[0019] The disclosed embodiment takes into account that the detection accuracy of soil acidity and alkalinity may be affected by soil moisture. In addition to setting up a soil pH value detection module, a soil moisture detection module is also set up. Before detecting the soil pH value, the soil moisture can be detected first, and the soil moisture can be compared with a set range. If it exceeds the set range, the soil pH value detection will not be performed, and a prompt will be given that the soil moisture is unqualified, requiring the detection personnel to add water or dry the soil before testing; if the soil moisture is within the set range, the soil pH value detection will be performed, and the soil pH value detection result will be compensated according to the soil moisture, thereby ensuring the accuracy of the soil pH value detection result.

[0020] Among them, the signal source in the soil moisture detection module is used to emit a periodic signal wave, and the periodic signal wave is transmitted to the detection electrode via a coaxial cable. Due to impedance mismatch, the periodic signal wave is reflected back to the transmitting end by the detection electrode, and superimposed with the emitted periodic signal wave to form a standing wave, resulting in a change in the potential at both ends of the coaxial cable. The change in potential is proportional to the impedance of the detection electrode, and the impedance of the detection electrode is proportional to the soil moisture. Therefore, the soil moisture can be obtained by detecting the change in potential at both ends of the coaxial cable. Accordingly, this embodiment sets a first peak detection circuit to detect the voltage peak at the first end of the coaxial cable, and sets a second peak detection circuit to detect the voltage peak at the second end of the coaxial cable. The difference between the two voltage peaks is calculated by a subtraction circuit to obtain the change in potential at both ends of the coaxial cable. The change in potential at both ends of the coaxial cable is input to the controller, and the controller can obtain soil moisture according to the change in potential at both ends of the coaxial cable. The cost of components required for the detection process is low, which is conducive to reducing the detection cost on the basis of ensuring the detection accuracy.

[0021] From the above analysis, it can be seen that the embodiment of the present disclosure achieves accurate detection of soil pH value at a low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0023] Figure 1 is a circuit schematic diagram of a soil moisture detection module provided in an embodiment of the present disclosure;

[0024] Figure 2 4 is a circuit diagram of a soil temperature detection module provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0025] In order to enable people in the technical field to better understand the present solution, the technical solution in the embodiment of the present solution will be clearly described below in conjunction with the drawings in the embodiment of the present solution. Obviously, the described embodiment is an embodiment of a part of the present solution, not all of the embodiments. Based on the embodiments in the present solution, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present solution.

[0026] The term "including" and any other variations in the specification and claims of this solution and the above drawings mean "including but not limited to", and is intended to cover non-exclusive inclusions and is not limited to the examples listed in the text. In addition, the terms "first" and "second" are used to distinguish different objects, not to describe a specific order.

[0027] The following is a detailed description of the implementation of the present disclosure in conjunction with the specific drawings:

[0028] Figure 1 This is a principle block diagram of a soil acid-base content detection device provided by an embodiment of the present disclosure. Figure 1 , the soil acid-base content detection device comprises:

[0029] Soil pH value detection module, used to detect soil acidity and alkalinity;

[0030] Soil moisture detection module, used to detect soil moisture;

[0031] The controller, the output end of the soil pH value detection module and the output end of the soil moisture detection module are both connected to the controller;

[0032] The soil moisture detection module includes a signal source, a coaxial cable, a detection electrode, a first peak detection circuit, a second peak detection circuit and a first subtraction circuit. The signal source is used to output a periodic signal. The first end of the coaxial cable is used to connect the signal source, and the second end of the coaxial cable is used to connect the detection electrode. The first peak detection circuit is used to detect the voltage signal at the first end of the coaxial cable, and the second peak detection circuit is used to detect the voltage signal at the second end of the coaxial cable. The output end of the first peak detection circuit is connected to the first end of the first subtraction circuit, and the output end of the second peak detection circuit is connected to the second end of the first subtraction circuit. The output end of the first subtraction circuit is the output end of the soil moisture detection module.

[0033] The disclosed embodiment takes into account that the detection accuracy of soil acidity and alkalinity may be affected by soil moisture. In addition to setting up a soil pH value detection module, a soil moisture detection module is also set up. Before detecting the soil pH value, the soil moisture can be detected first, and the soil moisture can be compared with a set range. If it exceeds the set range, the soil pH value detection will not be performed, and a prompt will be given that the soil moisture is unqualified, requiring the detection personnel to add water or dry the soil before testing; if the soil moisture is within the set range, the soil pH value detection will be performed, and the soil pH value detection result will be compensated according to the soil moisture, thereby ensuring the accuracy of the soil pH value detection result.

[0034] Among them, the signal source in the soil moisture detection module is used to emit a periodic signal wave, and the periodic signal wave is transmitted to the detection electrode via a coaxial cable. Due to impedance mismatch, the periodic signal wave is reflected back to the transmitting end by the detection electrode, and superimposed with the emitted periodic signal wave to form a standing wave, resulting in a change in the potential at both ends of the coaxial cable. The change in potential is proportional to the impedance of the detection electrode, and the impedance of the detection electrode is proportional to the soil moisture. Therefore, the soil moisture can be obtained by detecting the change in potential at both ends of the coaxial cable. Accordingly, this embodiment sets a first peak detection circuit to detect the voltage peak at the first end of the coaxial cable, and sets a second peak detection circuit to detect the voltage peak at the second end of the coaxial cable. The difference between the two voltage peaks is calculated by the subtraction circuit composed of the operational amplifier U3A to obtain the change in potential at both ends of the coaxial cable. The change in potential at both ends of the coaxial cable is input to the controller, and the controller can obtain soil moisture according to the change in potential at both ends of the coaxial cable. The cost of components required for the detection process is low, which is conducive to reducing the detection cost on the basis of ensuring the detection accuracy.

[0035] It should be noted that the pH value detection results under multiple soil moisture conditions can be obtained in advance through multiple tests, and the corresponding relationship between soil moisture and the compensation amount of the pH value detection result can be calculated based on this. In this way, when performing soil pH value detection, the corresponding compensation amount can be calculated according to the soil moisture, and the soil pH value detection result can be corrected according to the compensation amount.

[0036] From the above analysis, it can be seen that the embodiment of the present disclosure achieves accurate detection of soil pH value at a low cost.

[0037] In an exemplary embodiment of the present disclosure, the first peak detection circuit includes a diode D1, a capacitor C1 and a resistor R3.

[0038] The anode of the diode D1 is connected to the first end of the coaxial cable, the cathode of the diode D1 is connected to the first end of the capacitor C1, the second end of the capacitor C1 is grounded, the resistor R3 is connected in parallel across the capacitor C1, and one end of the capacitor C1 is the output end of the peak detection circuit.

[0039] In this embodiment, the periodic signal wave can be a high-frequency sine wave signal or a triangular wave signal. Taking a high-frequency sine wave signal as an example, in the positive half cycle of the periodic signal wave signal, the diode D1 is turned on, the output end of the signal source charges the capacitor C1, and the terminal voltage of the capacitor C1 increases. When it rises to the peak voltage of the periodic signal wave, the terminal voltage of the capacitor C1 remains unchanged; in the negative half cycle of the periodic signal wave signal, the diode D1 is turned off, and the capacitor C1 is discharged through the resistor R3 to prepare for the charging of the next cycle. Through the above process analysis, it can be seen that the terminal voltage of the capacitor C1 can change with the change of the peak voltage of the periodic signal wave, that is, the terminal voltage of the capacitor C1 is the peak voltage of the periodic signal wave.

[0040] It should be noted that the circuit structure of the second peak detection circuit is the same as the circuit structure of the first peak detection circuit, which will not be described in detail here.

[0041] In an exemplary embodiment of the present disclosure, a first amplification circuit is disposed between the first end of the coaxial cable and the first peak detection circuit.

[0042] In this embodiment, the operational amplifier U1A constitutes a first amplifying circuit for converting the voltage level of the signal output from the first end of the coaxial cable, which is beneficial to accurate identification of the first peak detection circuit, thereby facilitating improved detection accuracy of the voltage peak.

[0043] Similarly, a second amplifying circuit consisting of an operational amplifier U2A is provided between the second end of the coaxial cable and the second peak detection circuit.

[0044] In an exemplary embodiment of the present disclosure, a voltage follower is provided between the output terminal of the first peak detection circuit and the first subtraction circuit.

[0045] In this embodiment, the operational amplifier U1B forms a voltage follower with a large input impedance, which prevents the input impedance of the rear stage of the first peak detection circuit from being too small and causing excessive discharge of the capacitor C1, thereby further ensuring the detection accuracy of the first peak detection circuit.

[0046] Similarly, a voltage follower consisting of an operational amplifier U2B is provided between the output end of the second peak detection circuit and the first subtraction circuit.

[0047] In an exemplary embodiment of the present disclosure, a soil temperature detection module is also included, and the soil temperature detection module includes a thermistor, an operational amplifier U3B and a second subtraction circuit.

[0048] The non-inverting input terminal of the operational amplifier U3B is connected to the reference voltage, the inverting input terminal of the operational amplifier U3B is grounded through the resistor R14, and the output terminal of the operational amplifier U3B is connected to the inverting input terminal of the operational amplifier U3B through thermistor feedback.

[0049] Two ends of the thermistor are respectively connected to two input ends of the second subtraction circuit, and the output end of the second subtraction circuit is connected to the controller.

[0050] In this embodiment, considering that soil temperature will also affect the detection accuracy of soil pH value, a soil temperature detection module is provided, and the output of the soil temperature detection module is connected to the controller. The controller can compensate for the detection accuracy of soil pH value according to the real-time detected soil temperature.

[0051] Among them, the resistance of the thermistor in the soil temperature detection module changes with the change of temperature. The two ends of the thermistor are connected to the controller through connecting wires. The controller can obtain the change of temperature by detecting the change of the resistance of the thermistor, thereby realizing the temperature detection. Considering that the change of the resistance of the thermistor is slight, when the connecting wire is too long, the impedance of the connecting wire cannot be ignored, which will affect the resistance detection of the thermistor. In this embodiment, a constant current source circuit is set to provide a constant current for the thermistor, so that the change of the resistance of the thermistor is amplified into the change of the voltage at both ends of the thermistor. The controller can obtain the soil temperature by detecting the voltage at both ends of the thermistor.

[0052] Specifically, Figure 2 As shown, according to the "virtual short" characteristic of the op amp, the voltage U- at the inverting input terminal of the op amp U3B is equal to the reference voltage REF-2.5V. According to the "virtual open" characteristic of the op amp, the current flowing through the thermistor (connected through terminal P3) is equal to the current flowing through resistor R14, that is, the current flowing through the thermistor is equal to REF-2.5V / R14. The op amp U4A constitutes the second subtraction circuit. The two ends of the thermistor are respectively connected to the two input ends of the second subtraction circuit. The output voltage of the second subtraction circuit is the voltage across the thermistor. The voltage across the thermistor is connected to the controller. The controller can obtain the soil temperature by detecting the voltage across the thermistor.

[0053] In an exemplary embodiment of the present disclosure, the soil temperature detection module further includes a reference voltage module U5, and the reference voltage module U5 is used to provide a reference voltage for the non-inverting input terminal of the operational amplifier U3B.

[0054] In this embodiment, the reference voltage module U5 provides a constant 2.5V voltage to the non-inverting input terminal of the operational amplifier U3B, and then provides a constant current to the thermistor through the operational amplifier U3B.

[0055] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A soil acid-base content detection device, characterized in that: include: Soil pH value detection module, used to detect soil acidity and alkalinity; Soil moisture detection module, used to detect soil moisture; A controller, the output end of the soil pH value detection module and the output end of the soil moisture detection module are both connected to the controller; The soil moisture detection module includes a signal source, a coaxial cable, a detection electrode, a first peak detection circuit, a second peak detection circuit and a first subtraction circuit. The signal source is used to output a periodic signal. The first end of the coaxial cable is used to connect the signal source, and the second end of the coaxial cable is used to connect the detection electrode. The first peak detection circuit is used to detect the voltage signal at the first end of the coaxial cable, and the second peak detection circuit is used to detect the voltage signal at the second end of the coaxial cable. The output end of the first peak detection circuit is connected to the first end of the first subtraction circuit, and the output end of the second peak detection circuit is connected to the second end of the first subtraction circuit. The output end of the first subtraction circuit is the output end of the soil moisture detection module.

2. A soil acid-base content detection device as claimed in claim 1, characterized in that: The first peak detection circuit includes a diode D1, a capacitor C1 and a resistor R3. The anode of the diode D1 is connected to the first end of the coaxial cable, the cathode of the diode D1 is connected to the first end of the capacitor C1, the second end of the capacitor C1 is grounded, the resistor R3 is connected in parallel to both ends of the capacitor C1, and one end of the capacitor C1 is the output end of the peak detection circuit.

3. A soil acid-base content detection device as claimed in claim 1, characterized in that: A first amplifying circuit is arranged between the first end of the coaxial cable and the first peak detecting circuit.

4. A soil acid-base content detection device as claimed in claim 1, characterized in that: A voltage follower is provided between the output end of the first peak detection circuit and the first subtraction circuit.

5. A soil acid-base content detection device as claimed in claim 1, characterized in that: It also includes a soil temperature detection module, which includes a thermistor, an operational amplifier U3B and a second subtraction circuit. The non-inverting input terminal of the operational amplifier U3B is connected to the reference voltage, the inverting input terminal of the operational amplifier U3B is grounded through a resistor R14, and the output terminal of the operational amplifier U3B is connected to the inverting input terminal of the operational amplifier U3B through a thermistor feedback. Two ends of the thermistor are respectively connected to two input ends of the second subtraction circuit, and an output end of the second subtraction circuit is connected to a controller.

6. A soil acid-base content detection device as claimed in claim 5, characterized in that: It also includes a reference voltage module, which is used to provide a reference voltage for the in-phase input terminal of the operational amplifier U3B.

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