Self-adaptive range multi-mode liquid conductivity detection circuit

Abstract

The utility model relates to a self-adaptive range multi-mode liquid conductivity detection circuit. The self-adaptive range multi-mode liquid conductivity detection circuit comprises a micro-control unit MCU, a metal induction sheet A and a metal induction sheet B, the metal induction sheet A is connected with a first input / output port of the micro-control unit MCU; the metal induction sheet B is respectively connected with one ends of a plurality of access resistors with different resistance values, and the other ends of the access resistors are respectively connected with a plurality of second input and output ports, corresponding to the access resistors in number, in the MCU; the metal induction sheet A and the metal induction sheet B are used for containing liquid to be measured, and the micro-control unit MCU controls the open-drain output state or the push-pull output state of each second input and output port so as to switch the metal induction sheet B to be connected with the micro-control unit MCU through a certain access resistor, so that the measurement of the conductivity in the liquid is realized.

Description

Technical Field

[0001] The utility model relates to an adaptive range multi-mode liquid conductivity detection circuit and liquid conductivity detection technology. Background Art

[0002] In the field of liquid conductivity measurement technology, with the development of science and technology and the deepening of industrial applications, higher requirements are put forward for the accuracy, range and flexibility of conductivity measurement. Traditional conductivity measurement circuits often have problems such as fixed range, limited measurement range, and insufficient accuracy, making it difficult to meet the detection requirements of complex and changeable liquid environments. Especially in emerging fields such as water quality detection, agricultural irrigation, metal material process control, wine identification, salt content detection, and drug extraction, the requirements for conductivity measurement equipment are more stringent.

[0003] Traditional conductivity measurement circuits mostly adopt a single-range design and cannot automatically adjust the measurement range according to the conductivity of the liquid to be measured, resulting in limited measurement accuracy in low-conductivity or high-conductivity liquids. In addition, the fixed-range measurement method is also prone to introducing measurement errors due to improper range selection, affecting the accuracy of the results. Factors such as impurities, bubbles in the liquid, and the equivalent capacitance of the conductivity cell itself may introduce noise and interfere with the accuracy of the measurement signal. At the same time, the stability and reliability of the circuit are also important factors affecting the measurement results. Summary of the Utility Model

[0004] In order to solve the problems existing in the above-mentioned prior art, the utility model proposes an adaptive range multi-mode liquid conductivity detection circuit.

[0005] The technical solution of the utility model is as follows:

[0006] The utility model provides an adaptive range multi-mode liquid conductivity detection circuit, including a microcontroller unit MCU, a metal induction sheet A, and a metal induction sheet B;

[0007] The metal induction sheet A is connected to the first input / output port of the microcontroller unit MCU;

[0008] The metal induction sheet B is respectively connected to one end of a plurality of access resistors with different resistances, and the other end of each access resistor is respectively connected to a plurality of second input / output ports corresponding to the number of access resistors in the microcontroller unit MCU;

[0009] The metal induction sheet A and the metal induction sheet B are used to be placed in the liquid to be measured, and the microcontroller unit MCU controls the open-drain output state or push-pull output state of each second input / output port to switch the connection of the metal induction sheet B to the microcontroller unit MCU through a certain access resistor.

[0010] As a preferred embodiment of the present utility model, it further includes a thermistor RT;

[0011] One end of the thermistor RT is connected to a power supply, the other end of the thermistor RT is connected to the third input / output port of the micro-control unit MCU, and the other end of the thermistor RT is grounded through a resistor;

[0012] The thermistor RT is used to be placed in the liquid to be measured.

[0013] As a preferred embodiment of the present utility model, it further includes a control button S1;

[0014] One end of the control button S1 is connected to the fourth input / output port of the micro-control unit MCU, and the other end of the control button S1 is grounded;

[0015] The control button S1 is used to switch the measurement mode.

[0016] As a preferred embodiment of the present utility model, the metal induction sheet A and the metal induction sheet B are strip-shaped sheets.

[0017] The present utility model has the following beneficial effects:

[0018] 1. The present utility model can automatically adjust the measurement range according to the conductivity range of different liquids, avoiding the measurement error caused by the fixed range of traditional test pens, and improving the measurement accuracy and reliability.

[0019] 2. By designing multiple measurement modes, the user can conveniently switch between the conductivity, TDS, and temperature measurement modes to meet different test requirements and make the use more flexible. Description of the Drawings

[0020] Figure 1 It is a circuit schematic diagram of the present utility model. Specific Embodiments

[0021] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0022] It should be understood that the step numbers used in the text are only for convenient description and do not limit the execution order of the steps.

[0023] It should be understood that the terms used in the specification of the present utility model are only for the purpose of describing specific embodiments and are not intended to limit the present utility model. As used in the specification of the present utility model and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0024] The terms "comprising" and "including" indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their combinations.

[0025] The term "and / or" refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0026] Embodiment 1:

[0027] See Figure 1 , an adaptive range multi-mode liquid conductivity detection circuit, comprising a micro control unit MCU, a metal induction sheet A and a metal induction sheet B;

[0028] The metal induction sheet A is connected to the first input / output port of the micro control unit MCU;

[0029] The metal induction sheet B is respectively connected to one end of a plurality of access resistors with different resistance values, and the other ends of the respective access resistors are respectively connected to a plurality of second input / output ports corresponding to the number of access resistors in the micro control unit MCU;

[0030] The metal induction sheet A and the metal induction sheet B are used to be placed in the liquid to be measured, and the micro control unit MCU controls the open-drain output state or push-pull output state of each second input / output port to switch the connection of the metal induction sheet B to the micro control unit MCU through a certain access resistor.

[0031] As a preferred embodiment of the present utility model, it further includes a thermistor RT;

[0032] One end of the thermistor RT is connected to the power supply, the other end of the thermistor RT is connected to the third input / output port of the micro control unit MCU, and the other end of the thermistor RT is grounded through a resistor;

[0033] The thermistor RT is used to be placed in the liquid to be measured.

[0034] As a preferred embodiment of the present utility model, it further includes a control button S1;

[0035] One end of the control button S1 is connected to the fourth input / output port of the micro control unit MCU, and the other end of the control button S1 is grounded;

[0036] The control button S1 is used to switch the measurement mode.

[0037] As a preferred embodiment of the present invention, the metal induction sheets A and B are strip-shaped sheets. Increasing the areas of the metal induction sheets A and B can increase the measurement sensitivity.

[0038] The first input / output port is the general-purpose input / output pin P0;

[0039] The second input / output port is the general-purpose input / output pins P1, P2, P3, P4, and P5;

[0040] The third input / output port is the general-purpose input / output pin P6;

[0041] The fourth input / output port is the general-purpose input / output pin P7;

[0042] The access resistors are resistors R1, R2, R3, and R4;

[0043] The metal induction sheet A is connected to the general-purpose input / output pin P0 of the microcontroller unit MCU;

[0044] The metal induction sheet B is respectively connected to one end of resistor R1, one end of resistor R2, one end of resistor R3, one end of resistor R4, and the general-purpose input / output pin P5 of the microcontroller unit MCU; the other end of resistor R1 is connected to the general-purpose input / output pin P1 of the microcontroller unit MCU, the other end of resistor R2 is connected to the general-purpose input / output pin P2 of the microcontroller unit MCU, the other end of resistor R3 is connected to the general-purpose input / output pin P3 of the microcontroller unit MCU, and the other end of resistor R4 is connected to the general-purpose input / output pin P4 of the microcontroller unit MCU;

[0045] One end of the thermistor RT is connected to the positive pole of the power supply, the other end of the thermistor RT is respectively connected to one end of resistor R5 and the general-purpose input / output pin P6 of the microcontroller unit MCU, and the other end of resistor R5 is grounded;

[0046] One end of the control button S1 is connected to the general-purpose input / output pin P7 of the microcontroller unit MCU, and the other end of the control button S1 is grounded.

[0047] In at least one embodiment, the model of the microcontroller unit MCU is STM8S003F3.

[0048] In at least one embodiment, the resistance value of resistor R1 is 1 MΩ.

[0049] In at least one embodiment, the resistance value of the resistor R2 is 100 KΩ.

[0050] In at least one embodiment, the resistance value of the resistor R3 is 10 KΩ.

[0051] In at least one embodiment, the resistance value of the resistor R4 is 1 kΩ.

[0052] In at least one embodiment, the resistance value of the resistor R5 is 10 KΩ.

[0053] In at least one embodiment, the ambient temperature is 25 °C, and the resistance value of the resistor RT is 10 KΩ.

[0054] Embodiment 2:

[0055] When the metal induction sheet A and the metal induction sheet B are placed in the liquid to be detected for conductivity detection, the microcontroller unit MCU first sets the general-purpose input / output pin P1 to the push-pull output state, and sets the general-purpose input / output pins P2, P3, and P4 to the open-drain output state, that is, the high-impedance state. At this time, the circuits where the general-purpose input / output pins P2, P3, and P4 are located do not work.

[0056] The microcontroller unit MCU controls the general-purpose input / output pins P0 and P1 to output a 10 kHz continuous square wave simultaneously, and the waveforms are complementary, that is, if one port is at a high level, the other port must be at a low level.

[0057] The liquid to be detected is equivalent to a resistor between the metal induction sheet A and the metal induction sheet B. The microcontroller unit reads the voltage of the general-purpose input / output pin P5 every 100 ms, and the voltage division of the liquid to be detected and the reference resistor R1 of 1 MΩ can be obtained.

[0058] The equivalent resistance of the liquid to be detected can be calculated through the voltage division value and the value of the resistor R1.

[0059] When the read voltage is too large, due to the voltage division relationship, it indicates that the resistance of the liquid to be detected is small. At this time, the error of the calculated equivalent resistance is large and cannot be directly used.

[0060] At this time, the microcontroller unit MCU restores the general-purpose input / output pin P1 to the open-drain output state, sets the general-purpose input / output pin P2 to the push-pull output state, and keeps the general-purpose input / output pins P3 and P4 in the open-drain output state unchanged. At this time, the circuits where the general-purpose input / output pins P1, P3, and P4 are located do not work.

[0061] The microcontroller unit MCU controls the general-purpose input / output pins P0 and P2 to output a continuous square wave of 10 kHz simultaneously, and the waveforms are complementary.

[0062] The microcontroller unit MCU reads the voltage of the general-purpose input / output pin P5 every 100 ms, and then the voltage division of the measured liquid and the reference resistor R2 of 100 kΩ can be obtained.

[0063] Based on the voltage division value and the value of resistor R2, the equivalent resistance of the measured liquid can be calculated.

[0064] When the read voltage is still relatively large, this process is repeated, using R3 and R4 as the reference resistors in turn until the appropriate range is switched, and the equivalent resistance of the measured liquid is calculated.

[0065] The conductivity is equal to the reciprocal of the resistance, and thus the conductivity of the liquid is obtained.

[0066] Since the conductivity is greatly affected by temperature, it is also necessary to read the voltage of the general-purpose input / output pin P6 to calculate the current temperature of the measured liquid. Then, through the preset conductivity-temperature function relationship, the corrected conductivity of the measured liquid is obtained.

[0067] Through the preset conductivity-TDS function relationship, the TDS value of the measured liquid is obtained.

[0068] Through the control button S1, the display modes of conductivity, TDS, and temperature can be switched.

[0069] The above embodiments are only for illustrating the present invention. Those of ordinary skill in the art can make various transformations or changes without departing from the spirit and scope of the present invention. This includes but is not limited to changing the shape of the induction metal sheet to a rod shape or other shapes. This includes but is not limited to slightly changing the number and resistance values of the multi-stage voltage division resistors. This includes but is not limited to changing the frequency and duration of the square wave signal.

[0070] In the embodiments of this application, "at least one" means one or more, and "a plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent the situation of A existing alone, A and B existing simultaneously, and B existing alone. Among them, A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and back associated objects. "At least one of the following" and its similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0071] The above are only embodiments of the present utility model, and do not thereby limit the patent scope of the present utility model. Any equivalent structural or equivalent process transformations made by using the content of the specification and drawings of the present utility model, or directly or indirectly applied in other related technical fields, are similarly included within the patent protection scope of the present utility model.

Claims

1. An adaptive range multi-mode liquid conductivity detection circuit, characterized in that: It includes a micro control unit MCU, a metal sensing sheet A and a metal sensing sheet B; The metal sensor sheet A is connected to a first input / output port of a microcontroller unit MCU; The metal sensing sheet B is respectively connected to one end of a plurality of access resistors with different resistance values, and the other end of each access resistor is respectively connected to a plurality of second input and output ports in the microcontroller unit MCU corresponding to the number of the access resistors; The metal sensing sheet A and the metal sensing sheet B are used to put the liquid to be tested, and the microcontroller unit MCU controls the open-drain output state or the push-pull output state of each second input and output port to switch the metal sensing sheet B to be connected to the microcontroller unit MCU through a certain access resistor.

2. The adaptive range multi-mode liquid conductivity detection circuit according to claim 1, characterized in that: Also includes thermistor RT; One end of the thermistor RT is connected to a power supply, the other end of the thermistor RT is connected to a third input / output port of the microcontroller unit MCU, and the other end of the thermistor RT is grounded through a resistor; The thermistor RT is used to be placed in the liquid to be measured.

3. The adaptive range multi-mode liquid conductivity detection circuit according to claim 1, characterized in that: Also includes control button S1; One end of the control button S1 is connected to the fourth input / output port of the microcontroller unit MCU, and the other end of the control button S1 is grounded; The control button S1 is used to switch the measurement mode.

4. The adaptive range multi-mode liquid conductivity detection circuit according to claim 1, characterized in that: The metal sensing sheet A and the metal sensing sheet B are in the shape of strip sheets.

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