Constant voltage electrochemical residual chlorine water quality sensor

Abstract

The utility model belongs to sensor technical field, concretely is a kind of constant voltage electrochemical residual chlorine water quality sensor, including power supply circuit, constant voltage circuit, signal conditioning circuit, communication isolation circuit, communication circuit and central processing unit, power supply circuit is used to the internal working power supply of external power supply regulated output, and the working power supply that other circuit provides with external electrical isolation is provided after isolation conversion;The output end of constant voltage circuit is connected with auxiliary electrode CE, the input end of signal conditioning circuit is connected with working electrode WE, and working electrode WE and auxiliary electrode CE form current loop, and the concentration of current and the measured solution in chlorine is proportional relationship;The utility model uses the constant potential probe of three electrodes, eliminates water sample resistance, oxidation-reduction potential etc. interference by constant potential control, forms linear current-concentration relationship, and measurement result is fast, accurate and reliable;Power supply and communication circuit all use electrical isolation circuit, isolate external interference, improve measurement accuracy and stability.

Description

Technical Field

[0001] This utility model belongs to the field of sensor technology, specifically a constant voltage electrochemical residual chlorine water quality sensor. Background Technology

[0002] Residual chlorine disinfection is currently the most widely used disinfection method in the world. Its function is to ensure continuous sterilization and prevent water from being re-contaminated. However, if the residual chlorine level exceeds the standard, it may exacerbate the odor produced by phenols and other organic matter in the water, and may also generate organochlorine compounds such as chloroform, which have mutagenic, teratogenic, and carcinogenic effects. The sterilization and disinfection indicators are closely related to the residual chlorine content, making residual chlorine detection in water extremely important. However, currently used residual chlorine detection devices are inconvenient to carry, thus reducing the practicality of water quality testing devices. Furthermore, they are cumbersome to install and have poor detection efficiency.

[0003] A residual chlorine electrode is an online residual chlorine sensor, used in conjunction with a corresponding residual chlorine detector to form an online residual chlorine monitoring system. Residual chlorine electrodes are also called residual chlorine sensors or residual chlorine probes. Common residual chlorine sensors generally employ a diaphragm polarographic sensor, consisting of a cathode, anode, electrolyte, and a gas-permeable thin film covering the cathode. Residual chlorine in the test solution diffuses through the diaphragm to the cathode. An appropriate polarization voltage between the cathode and anode can reduce the residual chlorine at the cathode. These chemical reactions generate a current proportional to the residual chlorine in the measured solution.

[0004] In existing technologies, although membrane sensors reduce interference from external impurities through separation, they may still be affected by interference in complex environments (such as high salinity, high turbidity, etc.) and thus affect measurement accuracy. In environments with high concentrations of residual chlorine, membrane sensors may result in inaccurate measurement results due to membrane saturation or decreased separation efficiency, requiring more complex calibration and maintenance. Utility Model Content

[0005] To address the problems existing in the background technology, this utility model proposes a constant voltage electrochemical residual chlorine water quality sensor.

[0006] To achieve the above objectives, this utility model provides the following technical solution:

[0007] A constant voltage electrochemical residual chlorine water quality sensor includes an outer housing and an internal circuit structure. The housing has a communication connector and a detection terminal at both ends. The circuit includes a power supply circuit, a constant voltage circuit, a signal conditioning circuit, a communication isolation circuit, a communication circuit, and a central processing unit.

[0008] The power supply circuit is used to regulate the external power supply and output it as the internal working power supply. After isolation and transformation, it provides other circuits with working power that is electrically isolated from the outside.

[0009] The output terminal of the constant voltage circuit is connected to the auxiliary electrode CE, and the input terminal of the signal conditioning circuit is connected to the working electrode WE. The working electrode WE and the auxiliary electrode CE form a current loop, and the current is proportional to the concentration of chlorine in the solution being measured.

[0010] The output of the signal conditioning circuit is connected to the input of the analog-to-digital converter circuit, and the output of the analog-to-digital converter circuit is connected to the central processing unit.

[0011] The constant voltage circuit and signal conditioning circuit are connected to the central processing unit and are controlled by the central processing unit.

[0012] The communication circuit is connected to the central processing unit via a communication isolation circuit.

[0013] Preferably, the present invention also includes a temperature compensation circuit, with the input end connected to a temperature sensing element via interface H1 and the output end connected to a central processing unit, used to perform specific compensation on the collected chlorine value data based on the temperature data.

[0014] Preferably, the constant voltage circuit includes chip U3, amplifier U4, amplifier U19, and amplifier U20. The positive input terminal of amplifier U19 is connected to the central processing unit pin PB4 and grounded via capacitor C47. The inverting input terminal is connected to the reference electrode RE via series resistor R17. The output terminal of amplifier U19 is connected to the positive input terminal of amplifier U20 via series resistor R52. Resistor R51 and capacitor C42 are connected in parallel between the inverting input and output terminals of amplifier U19, and both resistor R51 and capacitor C42 are connected in series with resistor R52. The inverting input and output terminals of amplifier U20 are connected to the positive input terminal of amplifier U4 via resistor R53. The output of amplifier U4... The amplifier U4 is connected to the auxiliary electrode CE. A capacitor C5 and a resistor R25 are connected in parallel between the inverting input and output terminals of the amplifier U4. The inverting input terminal of the amplifier U4 is connected to the non-inverting input terminal after being connected in series with resistors R11, R10, R8, R9, and R12. One end of resistor R12 is connected to resistor R23 and then grounded. One end of resistor R25 is connected to the common terminal of resistors R10 and R11. One end of capacitor C5 is connected to the common terminal of resistor R11 and the inverting input terminal of amplifier U4. The portion between resistors R10 and R8 is connected to chip U3. The portion between resistors R9 and R12 is connected in parallel with capacitor C7 and a polarized capacitor C8.

[0015] Preferably, the signal conditioning circuit includes amplifier U9, amplifier U7, and chip U8. The inverting input terminal of amplifier U9 is connected to the working electrode WE after series with resistor R20, and the non-inverting input terminal is grounded after capacitor C18. Resistor R16 and capacitor C11 are connected in parallel between the inverting input terminal and the output terminal of amplifier U9. The output terminal of amplifier U9 is connected to the non-inverting input terminal of amplifier U7 after series with resistor R21. The inverting input terminal and the output terminal of amplifier U7 are both connected to pin 2 of chip U8. Resistor R1 is connected between pins 1 and 8 of chip U8. The common terminal of pin 1 of chip U8 and resistor R18 is connected to the central processing unit pin PB5. Pin 6 of chip U8 is connected to the analog-to-digital converter circuit after series with resistor R22.

[0016] Preferably, the analog-to-digital conversion circuit includes a chip U5. The VIN+ pin of the chip U5 is connected to the signal conditioning circuit. A resistor R13 is connected between the VIN+ and VIN- pins of the chip U5. The SDA pin of the chip U5 is connected to the +5V power supply after being connected in series with a resistor R14. The SCL pin of the U5 is connected to the +5V power supply after being connected in series with a resistor R15. The SDA pin is connected to the central processing unit pin PB12, and the SCL pin is connected to the central processing unit pin PB13.

[0017] Preferably, the communication circuit includes a chip U11 and a transistor Q1;

[0018] The communication isolation circuit includes chip U29;

[0019] Pin RO of chip U11 is connected to pin VIA of chip U29. The collector of the transistor is connected to pins DE and #RE of chip U11. The emitter is grounded. The base is connected to pin VOB of chip U29 after series resistor R30. Pin 6 of chip U11 is connected to RS485 interface A after series resistor R32. Pin 7 of chip U11 is connected to RS485 interface B after series resistor R31. Resistor R33 is connected between the pins of resistors R31 and R32 that are furthest from chip U11.

[0020] Pin VOA of chip U29 is connected to pin PD1 / OSC_OUT of central processing unit, and pin VIB of chip U29 is connected to pin PD0 / OSC_IN of central processing unit.

[0021] Preferably, the temperature compensation circuit includes an amplifier U1 and a temperature sensing element interface H1. A resistor R3 is connected in series between the inverting input terminal of the amplifier U1 and pin 1 of the temperature sensing element interface H1. A resistor R4 is connected in series between the non-inverting input terminal of the amplifier U1 and pin 2 of the temperature sensing element interface H1. The output terminal of the amplifier U1 is connected to the central processing unit pin PA12. A resistor R1 is connected in parallel between the inverting input terminal and the output terminal of the amplifier U1.

[0022] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0023] A three-electrode constant potential probe is used to eliminate interference from water sample resistance, redox potential, etc. through constant potential control, forming a linear current-concentration relationship, and the measurement results are fast, accurate and reliable;

[0024] Both the power supply and communication circuits employ electrical isolation circuits to isolate external interference and improve measurement accuracy and stability. Attached Figure Description

[0025] Figure 1 This is the power supply circuit diagram of this utility model;

[0026] Figure 2 This is the constant voltage circuit diagram of this utility model;

[0027] Figure 3 This is a circuit diagram of the signal conditioning circuit of this utility model;

[0028] Figure 4 This is the temperature compensation circuit diagram of this utility model;

[0029] Figure 5 This is the circuit diagram for the analog-to-digital converter of this utility model;

[0030] Figure 6 This is the communication circuit diagram of this utility model;

[0031] Figure 7 This is a circuit diagram of the communication isolation circuit of this utility model;

[0032] Figure 8 This is the circuit diagram of the central processing unit of this utility model;

[0033] Figure 9 This is the external interface circuit diagram of this utility model;

[0034] Figure 10 This is a schematic diagram of the external shell structure of this utility model. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The constant voltage measurement method maintains a stable potential at the electrode measuring terminals, under which different analytes generate different current intensities. It consists of a microcurrent measurement system composed of two platinum electrodes and a reference electrode. The constant voltage measurement method uses a secondary instrument to continuously and dynamically control the potential between the measuring electrodes, eliminating the influence of the inherent resistance and redox potential of the water sample. This results in a good linear relationship between the electrode measuring current signal and the concentration of the water sample, exhibiting highly stable zero-point performance and ensuring accurate and reliable measurements. The constant voltage residual chlorine sensor employs the constant voltage measurement principle.

[0037] refer to Figures 1 to 10 A constant voltage electrochemical residual chlorine water quality sensor includes an outer housing 1 and an internal circuit structure. The two ends of the housing are respectively provided with a communication connector 100 and a detection terminal 200. The circuit includes a power supply circuit, a constant voltage circuit, a signal conditioning circuit, a communication isolation circuit, a communication circuit, and a central processing unit.

[0038] The power supply circuit is used to regulate the output of the external power supply as the internal working power supply. After isolation and transformation, it provides working power that is electrically isolated from the external environment for other circuits. The output terminal of the constant voltage circuit is connected to the auxiliary electrode CE. The input terminal of the signal conditioning circuit is connected to the working electrode WE. The working electrode WE and the auxiliary electrode CE form a current loop. The current is proportional to the concentration of chlorine in the solution being tested. The output terminal of the signal conditioning circuit is connected to the input terminal of the analog-to-digital converter circuit. The output terminal of the analog-to-digital converter circuit is connected to the central processing unit. The constant voltage circuit and the signal conditioning circuit are connected to the central processing unit and are controlled by the signal from the central processing unit. The communication circuit is connected to the central processing unit through a communication isolation circuit.

[0039] refer to Figure 4This invention also includes a temperature compensation circuit. The input terminal is connected to a temperature sensing element via interface H1, and the output terminal is connected to a central processing unit (CPU). This circuit is used to perform specific compensation on the collected chlorine value data based on temperature data. Specifically, the temperature compensation circuit includes an amplifier U1 and a temperature sensing element interface H1. A resistor R3 is connected in series between the inverting input terminal of amplifier U1 and pin 1 of the temperature sensing element interface H1. A resistor R4 is connected in series between the non-inverting input terminal of amplifier U1 and pin 2 of the temperature sensing element interface H1. The output terminal of amplifier U1 is connected to the CPU pin PA12. A resistor R1 is connected in parallel between the inverting input terminal and the output terminal of amplifier U1. Resistor R4 and the non-inverting input terminal of amplifier U1 are grounded through resistor R7. The power supply pin of amplifier U1 is connected to a +5V power supply and grounded via capacitor C1, with its ground pin also grounded.

[0040] refer to Figure 2 , Figure 8 The constant voltage circuit includes chip U3, amplifier U4, amplifier U19, and amplifier U20. The positive input terminal of amplifier U19 is connected to the central processing unit pin PB4 and grounded via capacitor C47. Its inverting input terminal is connected to the reference electrode RE via resistor R17 in series. The output terminal of amplifier U19 is connected to the positive input terminal of amplifier U20 via resistor R52 in series. Resistor R51 and capacitor C42 are connected in parallel between the inverting input and output terminals of amplifier U19, and both resistor R51 and capacitor C42 are connected in series with resistor R52. The inverting input and output terminals of amplifier U20 are connected to the positive input terminal of amplifier U4 via resistor R53. The output terminal of amplifier U4... Connect the auxiliary electrode CE. Connect capacitor C5 and resistor R25 in parallel between the inverting input and output terminals of amplifier U4. Connect the inverting input terminal of amplifier U4 to its non-inverting input terminal by connecting resistors R11, R10, R8, R9, and R12 in series. Connect one end of resistor R12 to resistor R23 and then to ground. Connect one end of resistor R25 to the common terminal of resistors R10 and R11. Connect one end of capacitor C5 to the common terminal of resistor R11 and the inverting input terminal of amplifier U4. Connect the portion between resistors R10 and R8 to chip U3. Connect capacitor C7 and polarized capacitor C8 in parallel between resistors R9 and R12.

[0041] It should be noted that the ground pins of amplifiers U19, U4, and U20 are all connected to a -5V power supply, and the power supply pins are all connected to a +5V power supply and then grounded through a capacitor. The specific circuit diagram is shown below. Figure 2 As shown, it will not be elaborated upon here.

[0042] refer to Figure 3 , Figure 8The signal conditioning circuit includes amplifier U9, amplifier U7, and chip U8. The inverting input terminal of amplifier U9 is connected to the working electrode WE after series with resistor R20, and the non-inverting input terminal is grounded after capacitor C18. Resistor R16 and capacitor C11 are connected in parallel between the inverting input terminal and the output terminal of amplifier U9. The output terminal of amplifier U9 is connected to the non-inverting input terminal of amplifier U7 after series with resistor R21. The inverting input terminal and the output terminal of amplifier U7 are connected to pin 2 of chip U8. Resistor R1 is connected between pins 1 and 8 of chip U8. The common terminal of pin 1 of chip U8 and resistor R18 is connected to the central processing unit pin PB5. Pin 6 of chip U8 is connected to the analog-to-digital converter circuit after series with resistor R22.

[0043] It should be noted that pin 3 of U8 is connected to ground via resistor R26, and resistor R27 is connected to the connection point between resistor R26 and pin 3 of U8. One end of resistor R27 is connected to resistors R37 and R38, with resistor R37 connected to the +5V power supply and resistor R38 connected to the -5V power supply. The specific circuit structure is as follows. Figure 3 As shown, it will not be elaborated upon here.

[0044] refer to Figure 5 , Figure 8 The analog-to-digital conversion circuit includes a chip U5. The VIN+ pin of the chip U5 is connected to the signal conditioning circuit. A resistor R13 is connected between the VIN+ and VIN- pins of the chip U5. The SDA pin of the chip U5 is connected to the +5V power supply after being connected in series with a resistor R14. The SCL pin of the U5 is connected to the +5V power supply after being connected in series with a resistor R15. The SDA pin is connected to the central processing unit pin PB12, and the SCL pin is connected to the central processing unit pin PB13.

[0045] refer to Figure 6 The communication circuit includes chip U11 and transistor Q1;

[0046] The communication isolation circuit includes chip U29;

[0047] Pin RO of chip U11 is connected to pin VIA of chip U29. The collector of the transistor is connected to pins DE and #RE of chip U11, the emitter is grounded, and the base is connected to pin VOB of chip U29 via series resistor R30. Pin 6 of chip U11 is connected to RS485 interface A via series resistor R32, and pin 7 of chip U11 is connected to RS485 interface B via series resistor R31. Resistor R33 is connected between the pins of resistors R31 and R32 furthest from chip U11. Figure 9 The external interface circuit structure is used to connect external devices.

[0048] refer to Figure 7 , Figure 8 The VOA pin of the chip U29 is connected to the central processing unit pin PD1 / OSC_OUT, and the VIB pin of the chip U29 is connected to the central processing unit pin PD0 / OSC_IN.

[0049] In terms of working principle, in the power supply circuit, U10 regulates the external power supply to output a 5V internal operating power supply. This power supply is then isolated and transformed by U31, providing a completely electrically isolated operating power supply for the constant voltage circuit, signal processing circuit, and central processing unit. This ensures that these circuits are electrically isolated from external power sources and interference sources, fundamentally guaranteeing that the signals collected by the sensor are not affected by external interference, resulting in accurate values ​​and reliable operation. U2 provides a -5V power supply to the signal processing circuit, and U18 provides a +3.3V operating power supply to the central processing unit.

[0050] The constant voltage circuit consists of U3, U4, U19, U20, etc. Its output terminal is connected to the auxiliary electrode (also known as the counter electrode) CE. The working electrode WE and the auxiliary electrode CE form a current loop. This current is proportional to the concentration of chlorine in the measured solution. The current signal flowing through the working electrode WE is converted into a voltage signal at U9. After passing through the follower U7, it is sent to the variable gain amplifier U8 to adjust the signal amplitude. Then it is sent to the high-precision AD converter U5 for AD conversion. The converted data is read by the central processing unit (CPU) U12. At the same time, the reference electrode RE also senses the signal from the auxiliary electrode CE. This signal is conditioned by U19 and U20 and controlled by the central processing unit. The controlled voltage signal is fed back to U4 to adjust the output of the auxiliary electrode, eliminate interference from water sample resistance, redox potential, etc., and form a linear current-concentration relationship to ensure accurate and reliable measurement results. Meanwhile, to further improve detection accuracy, the sensor also has a temperature correction function. The temperature sensing element is connected through the H1 interface, amplified by U1 and read by the CPU. The collected chlorine value data is compensated based on the temperature data, which further improves the accuracy and stability of the measurement data. U29 is a communication isolation circuit that electrically isolates the signal from the external 485 communication (U11) from the internal TTL signal, also to isolate external interference sources and improve measurement accuracy.

Claims

1. A constant voltage electrochemical residual chlorine water quality sensor, comprising an outer housing (1) and a circuit structure disposed inside the housing, wherein the two ends of the housing (1) are respectively provided with a communication connector (100) and a detection terminal (200), characterized in that, The circuit includes a power supply circuit, a constant voltage circuit, a signal conditioning circuit, a communication isolation circuit, a communication circuit, and a central processing unit, wherein: the power supply circuit is used to regulate the output of the external power supply as the internal working power supply, and after isolation transformation, it provides other circuits with working power supply that is electrically isolated from the external environment. The output terminal of the constant voltage circuit is connected to the auxiliary electrode CE, and the input terminal of the signal conditioning circuit is connected to the working electrode WE. The working electrode WE and the auxiliary electrode CE form a current loop, and the current is proportional to the concentration of chlorine in the solution being measured. The output of the signal conditioning circuit is connected to the input of the analog-to-digital converter circuit, and the output of the analog-to-digital converter circuit is connected to the central processing unit. The constant voltage circuit and signal conditioning circuit are connected to the central processing unit and are controlled by the central processing unit to perform signal conversion; the communication circuit is connected to the central processing unit via a communication isolation circuit.

2. The constant voltage electrochemical residual chlorine water quality sensor according to claim 1, characterized in that, It also includes a temperature compensation circuit, with the input end connected to the temperature sensing element via interface H1 and the output end connected to the central processing unit, used to perform specific compensation on the collected chlorine value data based on the temperature data.

3. The constant voltage electrochemical residual chlorine water quality sensor according to claim 1, characterized in that, The constant voltage circuit includes chip U3, amplifier U4, amplifier U19, and amplifier U20. The positive input terminal of amplifier U19 is connected to the central processing unit pin PB4 and grounded via capacitor C47. Its inverting input terminal is connected to the reference electrode RE via resistor R17 in series. The output terminal of amplifier U19 is connected to the positive input terminal of amplifier U20 via resistor R52 in series. Resistor R51 and capacitor C42 are connected in parallel between the inverting input and output terminals of amplifier U19, and both resistor R51 and capacitor C42 are connected in series with resistor R52. The inverting input and output terminals of amplifier U20 are connected to the positive input terminal of amplifier U4 via resistor R53. The output terminal of amplifier U4 is connected to the auxiliary electrode CE. Capacitor C5 and resistor R25 are connected in parallel between the inverting input and output terminals of amplifier U4. Resistors R11, R10, R8, R9, and R12 are connected in series with the inverting input terminal of amplifier U4 in sequence. It is then connected to its positive input terminal, and one end of resistor R12 is connected to resistor R23 and then grounded. One end of resistor R25 is connected to the common terminal of resistors R10 and R11. One end of capacitor C5 is connected to the common terminal of resistor R11 and amplifier U4. The part between resistors R10 and R8 is connected to chip U3. The part between resistors R9 and R12 is connected in parallel with capacitor C7 and polarized capacitor C8.

4. The constant voltage electrochemical residual chlorine water quality sensor according to claim 1, characterized in that, The signal conditioning circuit includes amplifier U9, amplifier U7, and chip U8. The inverting input terminal of amplifier U9 is connected to the working electrode WE via a series resistor R20, and the non-inverting input terminal is grounded via a capacitor C18. A resistor R16 and a capacitor C11 are connected in parallel between the inverting input terminal and the output terminal of amplifier U9. The output terminal of amplifier U9 is connected to the non-inverting input terminal of amplifier U7 via a series resistor R21. The inverting input terminal and the output terminal of amplifier U7 are both connected to pin 2 of chip U8. A resistor R1 is connected between pins 1 and 8 of chip U8. The common terminal of pin 1 of chip U8 and resistor R18 is connected to the central processing unit pin PB5. Pin 6 of chip U8 is connected to the analog-to-digital converter circuit via a series resistor R22.

5. A constant voltage electrochemical residual chlorine water quality sensor according to claim 1, characterized in that, The analog-to-digital conversion circuit includes a chip U5. The VIN+ pin of the chip U5 is connected to the signal conditioning circuit. A resistor R13 is connected between the VIN+ and VIN- pins of the chip U5. The SDA pin of the chip U5 is connected to the +5V power supply after being connected in series with a resistor R14. The SCL pin of the U5 is connected to the +5V power supply after being connected in series with a resistor R15. The SDA pin is connected to the CPU pin PB12, and the SCL pin is connected to the CPU pin PB13.

6. The constant voltage electrochemical residual chlorine water quality sensor according to claim 1, characterized in that, The communication circuit includes chip U11 and transistor Q1; The communication isolation circuit includes chip U29; Pin RO of chip U11 is connected to pin VIA of chip U29. The collector of the transistor is connected to pins DE and #RE of chip U11. The emitter is grounded. The base is connected to pin VOB of chip U29 after series resistor R30. Pin 6 of chip U11 is connected to RS485 interface A after series resistor R32. Pin 7 of chip U11 is connected to RS485 interface B after series resistor R31. Resistor R33 is connected between the pins of resistors R31 and R32 away from chip U11. Pin VOA of chip U29 is connected to the central processing unit pin PD1 / OSC_OUT, and pin VIB of chip U29 is connected to the central processing unit pin PD0 / OSC_IN.

7. A constant voltage electrochemical residual chlorine water quality sensor according to claim 2, characterized in that, The temperature compensation circuit includes an amplifier U1 and a temperature sensing element interface H1. A resistor R3 is connected in series between the inverting input terminal of the amplifier U1 and pin 1 of the temperature sensing element interface H1. A resistor R4 is connected in series between the non-inverting input terminal of the amplifier U1 and pin 2 of the temperature sensing element interface H1. The output terminal of the amplifier U1 is connected to the central processing unit pin PA12. A resistor R1 is connected in parallel between the inverting input terminal and the output terminal of the amplifier U1.

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