Water permanganate index detection device

Abstract

The invention relates to the technical field of water body detection, and discloses a water body permanganate index detection device, which comprises a light beam output module, a reference light path, a measurement light path and a control module, the light beam output module outputs two paths of reference light and incident light with the same light intensity, the reference light path transmits the reference light to a first light intensity acquisition unit, and the measurement light path transmits the incident light to a second light intensity acquisition unit; the measuring light path inputs incident light into the reaction chamber and transmits emergent light of the reaction chamber to the second light intensity acquisition unit, the control module comprises a first light intensity acquisition unit, the second light intensity acquisition unit and a controller, and first light intensity of reference light and second light intensity of the emergent light are obtained through the first light intensity acquisition unit and the second light intensity acquisition unit; the titration end point of the potassium permanganate standard solution is determined based on the absorbance, so that the titration end point is judged by utilizing a method for measuring the optical absorbance, and the measurement accuracy is further improved.

Description

Technical Field

[0001] This invention relates to the field of water body detection technology, and in particular to a device for detecting the permanganate index of water. Background Technology

[0002] The permanganate index (IMN) of water bodies is a comprehensive indicator reflecting the pollution of surface water bodies by organic matter and inorganic oxidizable substances. It determines the overall pollution level of the water body by characterizing the content of reducing substances in the water. It is defined as the amount of potassium permanganate consumed by the oxidation of certain organic matter and inorganic reducing substances in a water sample in an acidic or alkaline medium, expressed in mg / L of oxygen.

[0003] Currently, the method for detecting the permanganate index is as follows: A known amount of potassium permanganate and sulfuric acid are added to the sample solution, and the solution is heated in a boiling water bath for 30 minutes. The potassium permanganate oxidizes certain organic and inorganic reducing substances in the sample. After the reaction, excess sodium oxalate is added to reduce the remaining potassium permanganate until the solution becomes colorless. Then, excess sodium oxalate is back-titrated with a potassium permanganate standard solution until the solution just turns pink and remains pink for 30 seconds. The volume of potassium permanganate standard solution consumed at this point is recorded, and the permanganate index in the sample solution is calculated based on the volume of potassium permanganate standard solution consumed. However, in related techniques, judging whether the potassium permanganate standard solution has reached the titration endpoint by visually observing the solution color introduces judgment errors, leading to inaccurate measurement results. Summary of the Invention

[0004] In view of this, the present invention provides a water permanganate index detection device to solve or partially solve the technical problem that the measurement results of existing water permanganate index detection are not accurate enough.

[0005] The technical solution proposed in this invention is as follows: This invention provides a water permanganate index detection device, comprising: The beam output module is used to output two beams of equal intensity: a reference beam and an incident beam. The reference optical path is used to transmit the reference light to the first optical intensity acquisition unit; The measurement optical path is used to input incident light into the reaction chamber and transmit the outgoing light from the reaction chamber to the second light intensity acquisition unit, wherein the incident light is transmitted through the reaction chamber to obtain the outgoing light; The control module includes a first light intensity acquisition unit, a second light intensity acquisition unit, and a controller. The controller acquires the first light intensity of the reference light and the second light intensity of the emitted light through the first and second light intensity acquisition units, respectively. It calculates the absorbance of the reaction chamber based on the first and second light intensities, determines the titration endpoint of the potassium permanganate standard solution based on the absorbance, and calculates the permanganate index of the sample solution by the titration volume of the potassium permanganate standard solution added when the titration endpoint is reached.

[0006] In some alternative implementations, the beam output module includes: A light source is used to generate an initial beam and input the initial beam into a splitting fiber; The beam splitter includes an optical fiber body, one end of which is connected to a first branch optical fiber and a second branch optical fiber, respectively. It is used to split the initial beam into two paths of reference light and incident light with equal intensity. The reference light is output through the first branch optical fiber, and the incident light is output through the second branch optical fiber.

[0007] In some alternative implementations, the reference optical path includes a reference optical fiber, one end of which is connected to a first branch optical fiber to receive reference light, and the other end of which is used to transmit the reference light to a first optical intensity acquisition unit. The measurement optical path includes an incident optical fiber and an outgoing optical fiber. One end of the incident optical fiber is connected to the second branch optical fiber to receive the incident light, and the other end of the incident optical fiber is connected to the beam inlet of the reaction chamber to output the incident light to the reaction chamber. One end of the outgoing optical fiber is connected to the beam outlet of the reaction chamber to receive the outgoing light, and the other end of the outgoing optical fiber is used to transmit the outgoing light to the second light intensity acquisition unit. The axes of the two close sections of the outgoing and incident optical fibers coincide, and the axes pass through the sample liquid in the reaction chamber.

[0008] In some alternative embodiments, both the beam exit port and the beam exit port are transparent windows disposed on the reaction chamber.

[0009] In some alternative embodiments, the beam exit port and the beam exit port are respectively a first through hole and a second through hole provided on the reaction chamber, the incident optical fiber passes through the first through hole and is sealed to the reaction chamber, and the exit optical fiber passes through the second through hole and is sealed to the reaction chamber.

[0010] In some alternative embodiments, the water permanganate index detection device further includes an inlet channel connected to the inlet end of the reaction chamber. A first pump body is provided on the inlet channel, and a pump drive module is connected to the first pump body. The pump drive module controls the first pump body to push the sample liquid or target reagent into the reaction chamber through the inlet channel.

[0011] In some optional embodiments, the water permanganate index detection device further includes an outlet channel and a three-way valve. The outlet channel includes a first branch pipe, a second branch pipe, and a third branch pipe. One end of the first branch pipe is connected to the outlet end of the reaction chamber, and the other end of the first branch pipe is connected to the first end of the three-way valve. The second end of the three-way valve is connected to one end of the second branch pipe, and the third end of the three-way valve is connected to the waste liquid tank through the third branch pipe. A second pump body is provided on the second branch pipe, and the second pump body is connected to a pump drive module. After each addition of potassium permanganate standard solution, the pump drive module controls the second pump body to push external gas into the reaction chamber through the second branch pipe.

[0012] In some alternative embodiments, the first light intensity acquisition unit includes a first photodiode, the anode of the first photodiode is grounded, and the cathode of the first photodiode is connected to the controller in sequence through a transimpedance amplifier, an impedance matching circuit, a voltage follower and an analog-to-digital converter circuit connected in series. The structure of the second light intensity acquisition unit is the same as that of the first light intensity acquisition unit.

[0013] In some alternative embodiments, the transimpedance amplifier includes a feedback circuit and a first operational amplifier. The feedback circuit includes a gain resistor and a compensation capacitor connected in parallel. The cathode of the first photodiode is connected to the first end of the gain resistor, the first end of the compensation capacitor, and the inverting input of the first operational amplifier, respectively. The second end of the gain resistor and the second end of the compensation capacitor are connected to the output of the first operational amplifier, respectively. The non-inverting input of the first operational amplifier is grounded.

[0014] In some optional embodiments, the transimpedance amplifier further includes a controllable switch chip. Several feedback circuits are provided. The controllable switch chip includes an output connection terminal, several input connection terminals, and several control input terminals. The output connection terminal is connected to the output terminal of the first operational amplifier. Any input connection terminal is connected to the cathode of the first photodiode through a corresponding feedback circuit. The gain resistors in different feedback circuits have different resistance values. The control input terminal is connected to the controller to receive the switch control signal input by the controller. The controllable switch chip switches the input connection terminal connected to the output connection terminal according to the switch control signal.

[0015] As can be seen from the above technical solutions, the present invention has the following advantages: This invention provides a water permanganate index detection device. It outputs two beams of equal intensity—a reference beam and an incident beam—through a beam output module. The measurement beam path converts the incident beam into outgoing beam after passing through the sample solution in the reaction chamber. This outgoing beam is then collected by a second light intensity acquisition unit to obtain the second light intensity. The reference beam is directly collected by a first light intensity acquisition unit to obtain the first light intensity. The absorbance of the reaction chamber can then be calculated based on the first and second light intensities. When the titration endpoint is reached, the absorbance undergoes a sudden change, resulting in a more accurate titration endpoint. The permanganate index of the sample solution is calculated by the titration volume of the potassium permanganate standard solution added at the titration endpoint. This method utilizes optical absorbance measurement to determine the titration endpoint, thereby improving measurement accuracy. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a water permanganate index detection device in an embodiment of the present invention; Figure 2 This is a schematic diagram of another water permanganate index detection device in an embodiment of the present invention; Figure 3 This is a circuit diagram of the first light intensity acquisition unit in an embodiment of the present invention; Figure 4 This is a circuit diagram of the second light intensity acquisition unit in an embodiment of the present invention; Figure 5 This is a circuit diagram of the analog-to-digital conversion circuit in an embodiment of the present invention.

[0018] Figure label: 1-Reference optical path; 2-Measurement optical path; 21-Incident fiber; 22-Outgoing fiber; 3-Control module; 4-Beam output module; 41-Light source; 42-Bundle splitter fiber; 5-First pump body; 6-Second pump body; 7-First light intensity acquisition unit; 8-Second light intensity acquisition unit; C1-First capacitor; C2-Second capacitor; C3-Third capacitor; C4-Fourth capacitor; C5-Fifth capacitor; R1-First resistor; R2-Second resistor; R3-Third resistor; R4-Fourth resistor; R5-Fifth resistor; R6-Sixth resistor; R7-Seventh resistor; D1-First photodiode; D2-Second photodiode; U1-Controllable switch chip; U2-First operational amplifier; U3-Second operational amplifier; Analog-to-digital converter (ADC). Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0020] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; a connection within two components; a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The terms “coincident” and “equal” include the described situation and situations that are similar to the described situation, within an acceptable deviation range, which is determined by those skilled in the art taking into account the measurement under discussion and the error associated with the measurement of a particular quantity (i.e., the limitations of the measurement system). For example, “equal” includes absolute equality and approximate equality, where an acceptable deviation range for approximate equality may be, for example, a difference between the two equal items less than or equal to 5% of either one. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0021] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] This invention provides a water permanganate index detection device that can use optical methods to determine the titration endpoint and count the total amount of reagent added during the titration process. Thus, when the titration endpoint is reached, the concentration of permanganate in the sample solution can be calculated based on the amount of reagent added.

[0023] like Figure 1 As shown, this embodiment of the invention provides a water permanganate index detection device, comprising: Beam output module 4 is used to output two reference beams and incident beams with equal intensity.

[0024] The optical parameters of the reference light and the incident light should be kept as similar as possible to ensure that the change in the intensity of the incident light is caused by the change in the absorption of the sample liquid in the reaction chamber.

[0025] Specifically, the wavelengths of both the reference light and the incident light are 492nm-577nm. When using potassium permanganate standard solution to titrate the sample solution, the molar absorptivity of the light in this wavelength band is relatively large after the titration endpoint is reached, making it easy to detect whether the titration endpoint has been reached.

[0026] Reference optical path 1 is used to transmit reference light to the first light intensity acquisition unit 7.

[0027] The measuring optical path 2 is used to input incident light into the reaction chamber and transmit the outgoing light from the reaction chamber to the second light intensity acquisition unit 8, wherein the incident light is transmitted through the reaction chamber to obtain the outgoing light.

[0028] Specifically, the first light intensity acquisition unit 7 and the second light intensity acquisition unit 8 can use photodetectors of the same type or light intensity detection circuits of the same structure to avoid acquisition errors that may occur between different acquisition units.

[0029] The main difference between the reference optical path 1 and the measurement optical path 2 is that the incident light in the measurement optical path 2 needs to be absorbed by the sample liquid in the reaction chamber before being emitted and its intensity is collected by the first light intensity acquisition unit 7, while the reference optical path 1 directly transmits the light to the second light intensity acquisition unit 8 for acquisition. The light output from the reference optical path 1 and the measurement optical path 2 reaches the detection areas of the first light intensity acquisition unit 7 and the second light intensity acquisition unit 8, respectively, thereby acquiring the first light intensity of the emitted light and the second light intensity of the reference light.

[0030] The control module 3 includes a first light intensity acquisition unit 7, a second light intensity acquisition unit 8, and a controller. The controller acquires the first light intensity of the reference light and the second light intensity of the emitted light through the first light intensity acquisition unit 7 and the second light intensity acquisition unit 8, respectively. It calculates the absorbance of the reaction chamber based on the first light intensity and the second light intensity, determines the titration endpoint of the potassium permanganate standard solution based on the absorbance, and calculates the permanganate index of the sample solution by the titration volume of the potassium permanganate standard solution added when the titration endpoint is reached.

[0031] It should be understood that the reaction chamber is a reaction vessel for permanganate index detection. When performing permanganate index detection, the sample solution is first added to the reaction chamber, and then a certain amount of potassium permanganate and sulfuric acid are injected into the reaction chamber in a certain order and mixed. The mixture is heated and digested so that some organic and inorganic reducing substances in the sample solution are oxidized by potassium permanganate. After digestion, excess sodium oxalate is added as a reducing agent to react with the remaining potassium permanganate. Finally, the remaining sodium oxalate is back-titrated with potassium permanganate standard solution, and the permanganate index of the sample solution is calculated by the amount of back-titration.

[0032] During the back titration process, after each titration of a certain amount of potassium permanganate standard solution, the volume of the titrated potassium permanganate standard solution is recorded. The incident light in optical path 2 is measured as it passes through the sample solution in the reaction chamber during the titration process and is emitted as outgoing light. After each titration, the controller calculates the absorbance of the reaction chamber based on the first and second light intensities collected. The calculation formula is:

[0033] In the formula, Absorbance The highest light intensity, This is the second light intensity.

[0034] When the absorbance changes abruptly, that is, when the difference between the absorbance after the current titration and the absorbance after the previous titration is greater than the preset difference, the titration endpoint is determined to have been reached, and the permanganate index of the sample solution is calculated based on the titration volume of the potassium permanganate standard solution at this time.

[0035] The controller can be a microcontroller unit (MCU).

[0036] The water permanganate index detection device of this invention outputs two beams of equal intensity—a reference beam and an incident beam—through a beam output module 4. The measurement optical path 2 transforms the incident beam into an outgoing beam after passing through the sample liquid in the reaction chamber. The outgoing beam is then collected by a second light intensity acquisition unit 8 to obtain the second light intensity. The reference beam is directly collected by a first light intensity acquisition unit 7 to obtain the first light intensity. The absorbance of the reaction chamber can then be calculated based on the first and second light intensities. When the titration endpoint is reached, the absorbance undergoes a sudden change, thus obtaining a more accurate titration endpoint. The permanganate index of the sample liquid is calculated by the titration volume of the potassium permanganate standard solution added at the titration endpoint. This method of determining the titration endpoint by measuring optical absorbance improves measurement accuracy.

[0037] In some embodiments, the beam output module 4 includes a light source 41 and a beam splitter fiber 42.

[0038] Among them, the light source 41 is used to generate the initial beam and input the initial beam into the splitting fiber 42; The beam splitter 42 includes an optical fiber body, one end of which is connected to a first branch optical fiber and a second branch optical fiber, respectively, for splitting the initial beam into two paths of reference light and incident light with equal intensity. The reference light is output through the first branch optical fiber, and the incident light is output through the second branch optical fiber.

[0039] Specifically, the light source 41 is a monochromatic light-emitting diode or a laser light source 41. In one example, the light source 41 is a monochromatic light-emitting diode with an output wavelength of 492nm-577nm.

[0040] The light source 41 is located at the entrance end of the splitting fiber 42. The initial beam generated by the light source 41 is split into two paths of equal intensity, a reference beam and an incident beam, by the splitting fiber 42, and then output through the first branch fiber and the second branch fiber, respectively.

[0041] Further, the reference optical path 1 includes a reference optical fiber, one end of which is connected to the first branch optical fiber to receive reference light, and the other end of which is used to transmit the reference light to the first light intensity acquisition unit 7; the measurement optical path 2 includes an incident optical fiber 21 and an exit optical fiber 22, one end of the incident optical fiber 21 is connected to the second branch optical fiber to receive incident light, and the other end of the incident optical fiber 21 is connected to the beam inlet of the reaction chamber to output incident light to the reaction chamber, one end of the exit optical fiber 22 is connected to the beam outlet of the reaction chamber to receive exit light, and the other end of the exit optical fiber 22 is used to transmit the exit light to the second light intensity acquisition unit 8, the axes of the two close sections of the exit optical fiber 22 and the incident optical fiber 21 coincide, and the axes pass through the sample liquid in the reaction chamber.

[0042] Specifically, photodiodes are provided at the exit ends of both the output fiber 22 and the reference fiber, meaning that both the first light intensity acquisition unit 7 and the second light intensity acquisition module use photodiodes to detect light intensity. The initial beam generated by the light source 41 is split into reference light and incident light by the beam splitter fiber 42. The reference light is directly transmitted to the first light intensity acquisition unit 7 via the reference fiber, where the intensity of the reference light is detected. The incident light enters the reaction chamber through the incident fiber 21, and part of the incident light is absorbed by the permanganate in the reaction chamber. The outgoing light that has passed through the reaction chamber is transmitted to the second light intensity acquisition unit 8 via the output fiber 22, where the intensity of the outgoing light is detected.

[0043] To ensure that the beam emitted from the incident fiber 21 can enter the incident fiber 21 after passing through the sample liquid, the beam exit port and the beam exit port of the reaction chamber are located on the same horizontal plane and are set opposite to each other, so that the axes of the two close sections of the outgoing fiber 22 and the incident fiber 21 coincide, and the axes pass through the sample liquid in the reaction chamber.

[0044] In this embodiment of the invention, except for the optical path of the reaction chamber, the light beams in other optical paths propagate in optical fibers, which reduces light loss and interference during transmission, improves the accuracy of light intensity measurement, thereby improving the accuracy of absorbance calculation, and further improving the accuracy of permanganate index detection in water.

[0045] In some embodiments, both the beam exit port and the beam exit port are transparent windows disposed on the reaction chamber.

[0046] Specifically, both the beam exit port and the beam exit port utilize transparent windows, such as transparent glass or transparent plastic windows. The other parts of the reaction chamber sidewall can be made of either transparent or non-transparent materials. The two end faces of the incident fiber 21 and the exit fiber 22, which are close to each other, are fixedly connected to the outer surfaces of two opposing transparent windows.

[0047] In one example, the sidewalls of the reaction chamber are made entirely of transparent material for ease of manufacture.

[0048] In this embodiment, the connection and fixation of the incident fiber 21, the exit fiber 22 and the reaction chamber are relatively simple, which facilitates manufacturing and installation. At the same time, it can ensure that the light beam can smoothly enter and exit the reaction chamber, which is beneficial to improving the accuracy of light intensity measurement.

[0049] In some embodiments, the beam exit port and the beam exit port are respectively a first through hole and a second through hole provided on the reaction chamber, the incident optical fiber 21 passes through the first through hole and is sealed to the reaction chamber, and the exit optical fiber 22 passes through the second through hole and is sealed to the reaction chamber.

[0050] Specifically, the first through hole and the second through hole can be round holes, square holes, etc., that penetrate the side wall of the reaction chamber.

[0051] The optical fiber passes through the corresponding through hole and is sealed to the reaction chamber. Taking the incident optical fiber 21 as an example, the cross-sectional area of ​​its output end is slightly smaller than the area of ​​the first through hole. The incident optical fiber 21 enters the reaction chamber through the first through hole, and the connection between the input optical fiber and the reaction chamber is sealed by a sealing ring or sealing mold to prevent liquid leakage in the reaction chamber.

[0052] In this embodiment, the light beam between the incident fiber 21 and the outgoing fiber 22 does not need to pass through the side wall of the reaction chamber, which avoids the absorption of the light beam by the transparent window and thus improves the measurement accuracy of absorbance.

[0053] In some embodiments, such as Figure 2 As shown, the water permanganate index detection device also includes an inlet channel, which is connected to the inlet end of the reaction chamber. A first pump body 5 is provided on the inlet channel, and a pump drive module is connected to the first pump body 5. The pump drive module controls the first pump body 5 to push the sample liquid or target reagent into the reaction chamber through the inlet channel.

[0054] Specifically, the inlet of the reaction chamber is located on the upper side of the reaction chamber, and the first pump body 5 is a plunger pump.

[0055] The sample solution to be tested, along with reagents such as potassium permanganate, ammonium sulfate, and sodium oxalate, are added to the reaction chamber through the inlet channel, and the injection flow rate and amount are controlled by the first pump body 5.

[0056] The pump drive module can use a servo motor drive module or a stepper motor drive module to control the pump body.

[0057] By controlling the first pump body 5 to push the sample solution or reagent into the reaction chamber through the inlet channel, the automatic injection of sample solution and reagent is realized, which improves the automation level of detection, reduces manual operation, and improves detection efficiency and accuracy.

[0058] Furthermore, the water permanganate index detection device also includes an outlet channel and a three-way valve. The outlet channel includes a first branch pipe, a second branch pipe, and a third branch pipe. One end of the first branch pipe is connected to the outlet end of the reaction chamber, and the other end of the first branch pipe is connected to the first end of the three-way valve. The second end of the three-way valve is connected to one end of the second branch pipe, and the third end of the three-way valve is connected to the waste liquid tank through the third branch pipe. A second pump body 6 is provided on the second branch pipe, and the second pump body 6 is connected to the pump drive module. After each addition of potassium permanganate standard solution, the pump drive module controls the second pump body 6 to push external gas into the reaction chamber through the second branch pipe.

[0059] Specifically, the three-way valve is an electric three-way valve, and the opening and closing of each port of the three-way valve is controlled by a controller. The second pump body 6 is a peristaltic pump.

[0060] After each titration of a certain amount of potassium permanganate standard solution, the first and second branch pipes are connected by controlling the opening and closing of each port of the three-way valve. Air is then pumped into the reaction chamber through the second pump body 6, causing the potassium permanganate standard solution dropped into the reaction chamber to mix and react with the solution. After the liquid in the reaction chamber returns to a stable state, the intensity of the emitted light from the output optical fiber 22 is collected. After the detection is completed, the opening and closing of each port of the three-way valve is controlled to connect the first and third branch pipes, and the solution in the reaction chamber is discharged to the waste liquid pool by the second pump body 6.

[0061] In this embodiment, after each addition of potassium permanganate standard solution, the second pump 6 is controlled to push external gas into the reaction chamber through the second branch pipe. This allows for stirring or mixing of the reaction chamber after reagent addition, resulting in a more complete reaction. Additionally, the waste liquid can be discharged into the waste liquid pool after the detection is completed, improving the accuracy of the detection and the convenience of the device.

[0062] In some embodiments, such as Figure 3 As shown, the first light intensity acquisition unit 7 includes a first photodiode D1. The anode of the first photodiode D1 is grounded, and the cathode of the first photodiode D1 is connected to the controller in sequence through a transimpedance amplifier, an impedance matching circuit, a voltage follower, and an analog-to-digital converter circuit connected in series.

[0063] like Figure 4As shown, the structure of the second light intensity acquisition unit 8 is the same as that of the first light intensity acquisition unit 7, including a second photodiode D2 and a corresponding transimpedance amplifier, impedance matching circuit, voltage follower and analog-to-digital conversion circuit.

[0064] Specifically, the transimpedance amplifier includes a feedback circuit and a first operational amplifier U2. The feedback circuit includes a gain resistor and a compensation capacitor connected in parallel. The cathode of the first photodiode D1 is connected to the first end of the gain resistor, the first end of the compensation capacitor, and the inverting input of the first operational amplifier U2, respectively. The second end of the gain resistor and the second end of the compensation capacitor are connected to the output of the first operational amplifier U2, respectively. The non-inverting input of the first operational amplifier U2 is grounded.

[0065] The non-inverting input of the first operational amplifier U2 is grounded through the fifth resistor R5.

[0066] The impedance matching circuit includes a sixth resistor R6, a seventh resistor R7, and a fifth capacitor C5. The first terminal of the sixth resistor R6 is connected to the output terminal of the first operational amplifier U2. The second terminal of the sixth resistor R6 is connected to both the first terminal of the seventh resistor R7 and the first terminal of the fifth capacitor C5. The second terminal of the fifth capacitor C5 is grounded. The second terminal of the seventh resistor R7 is connected to the non-inverting input terminal of the voltage follower. The impedance matching circuit achieves input and output impedance matching.

[0067] The voltage follower mainly includes the second operational amplifier U3, which can maintain the stability of the output signal.

[0068] like Figure 5 As shown, the analog-to-digital conversion circuit mainly includes an analog-to-digital converter (ADC). The ADC converts the analog signal into a digital signal, which is then output to the controller to calculate the absorbance of the solution in the reaction chamber. The first light intensity acquisition unit 7 and the second light intensity acquisition unit 8 can share a single ADC. That is, the analog signals ADC_1 and ADC_2 obtained from the first and second light intensity acquisition units 7 and 8 are respectively output to the same ADC for analog-to-digital conversion, resulting in digital signals MCU_5 and MCU_6. These digital signals are then input to the controller, reducing the number of components used.

[0069] The working principle of the first light intensity acquisition unit 7 is as follows: When the first photodiode D1 is illuminated by reference light, it generates a current. The greater the light intensity, the greater the current. The current signal is converted into a voltage signal by a transimpedance amplifier, where the output voltage of the transimpedance amplifier and the output voltage of the first operational amplifier U2 are... for: ,in, The magnitude of the current generated by the first photodiode D1. This is the resistance value of the gain resistor. Output voltage. After passing through the impedance matching circuit, voltage follower, and analog-to-digital converter, the signal enters the controller, which then adjusts the output voltage accordingly. The size of the light intensity is obtained from the light intensity.

[0070] The working principle of the second light intensity acquisition unit 8 is the same as that of the first light intensity acquisition unit 7.

[0071] Furthermore, the transimpedance amplifier also includes a controllable switch chip U1. Several feedback circuits are provided. The controllable switch chip U1 includes an output connection terminal, several input connection terminals, and several control input terminals. The output connection terminal is connected to the output terminal of the first operational amplifier U2. Any input connection terminal is connected to the cathode of the first photodiode D1 through the corresponding feedback circuit. The resistance values ​​of the gain resistors in different feedback circuits are different. The control input terminal is connected to the controller to receive the switch control signal input by the controller. The controllable switch chip U1 switches the input connection terminal connected to the output connection terminal according to the switch control signal.

[0072] In one example, the controllable switch chip U1 includes four input terminals, namely the first input terminal 1Y0, the second input terminal 1Y1, the third input terminal 1Y2 and the fourth input terminal 1Y3, and the control input terminals include the first control input terminal S1 and the second control input terminal S2. The first control input terminal S1 and the second control input terminal S2 are respectively connected to the controller to receive the first switch control signal MCU_1 and the second switch control signal MCU_2. The controllable switch chip U1 determines the input connection terminal that is connected to the output connection terminal 1Z among the first input connection terminal 1Y0, the second input connection terminal 1Y1, the third input connection terminal 1Y2 and the fourth input connection terminal 1Y3, based on the first switch control signal MCU_1 and the second switch control signal MCU_2. For example, when the first switch control signal MCU_1 and the second switch control signal MCU_2 are both low, the first input connection terminal 1Y0 is connected to the output connection terminal 1Z; when the first switch control signal MCU_1 is high and the second switch control signal MCU_2 is low, the second input connection terminal 1Y1 is connected to the output connection terminal 1Z, and so on.

[0073] The gain resistors in the feedback circuit connected to the first input terminal 1Y0, the second input terminal 1Y1, the third input terminal 1Y2, and the fourth input terminal 1Y3 are, in order, resistor R1, resistor R2, resistor R3, and resistor R4. The compensation capacitors are, in order, capacitor C1, capacitor C2, capacitor C3, and capacitor C4. The resistance values ​​of the different gain resistors are different; for example, the resistance values ​​of resistors R1, R2, R3, and R4 increase sequentially. Thus, when different gain resistors are connected to the first operational amplifier U2, the output voltage of the first operational amplifier U2 varies. It is divided into different measurement levels to achieve accurate measurement of light intensity at different levels.

[0074] While exemplary embodiments and their advantages have been described in detail, those skilled in the art can make various changes, substitutions and modifications to these embodiments without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined herein.

Claims

1. A device for detecting the permanganate index of water, characterized in that, include: The beam output module is used to output two beams of equal intensity: a reference beam and an incident beam. A reference optical path is used to transmit the reference light to the first optical intensity acquisition unit; The measurement optical path is used to input the incident light into the reaction chamber and transmit the outgoing light from the reaction chamber to the second light intensity acquisition unit, wherein the incident light is transmitted through the reaction chamber to obtain the outgoing light; The control module includes a first light intensity acquisition unit, a second light intensity acquisition unit, and a controller. The controller acquires the first light intensity of the reference light and the second light intensity of the emitted light through the first light intensity acquisition unit and the second light intensity acquisition unit, respectively. It calculates the absorbance of the reaction chamber based on the first light intensity and the second light intensity, determines the titration endpoint of the potassium permanganate standard solution based on the absorbance, and calculates the permanganate index of the sample solution by the titration volume of the potassium permanganate standard solution added when the titration endpoint is reached.

2. The water permanganate index detection device according to claim 1, characterized in that, The beam output module includes: A light source is used to generate an initial beam and input the initial beam into a splitting fiber. The beam splitter includes an optical fiber body, one end of which is connected to a first branch optical fiber and a second branch optical fiber, respectively, for splitting the initial beam into two paths of equal intensity: a reference light and an incident light. The reference light is output through the first branch optical fiber, and the incident light is output through the second branch optical fiber.

3. The water permanganate index detection device according to claim 2, characterized in that, The reference optical path includes a reference optical fiber, one end of which is connected to the first branch optical fiber to receive the reference light, and the other end of which is used to transmit the reference light to the first light intensity acquisition unit. The measurement optical path includes an incident optical fiber and an outgoing optical fiber. One end of the incident optical fiber is connected to the second branch optical fiber to receive the incident light, and the other end of the incident optical fiber is connected to the beam inlet of the reaction chamber to output the incident light to the reaction chamber. One end of the outgoing optical fiber is connected to the beam outlet of the reaction chamber to receive the outgoing light, and the other end of the outgoing optical fiber is used to transmit the outgoing light to the second light intensity acquisition unit. The axes of two close sections of the outgoing optical fiber and the incident optical fiber coincide, and the axes pass through the sample liquid in the reaction chamber.

4. The water permanganate index detection device according to claim 3, characterized in that, Both the beam exit port and the beam exit port are transparent windows installed on the reaction chamber.

5. The water permanganate index detection device according to claim 3, characterized in that, The beam exit port and the beam exit port are respectively provided on the reaction chamber as a first through hole and a second through hole. The incident optical fiber passes through the first through hole and is sealed to the reaction chamber, and the outgoing optical fiber passes through the second through hole and is sealed to the reaction chamber.

6. The water permanganate index detection device according to claim 1, characterized in that, It also includes an inlet channel, which is connected to the inlet end of the reaction chamber. A first pump body is provided on the inlet channel, and a pump drive module is connected to the first pump body. The pump drive module controls the first pump body to push the sample liquid or target reagent into the reaction chamber through the inlet channel.

7. The water permanganate index detection device according to claim 6, characterized in that, It also includes an outlet flow channel and a three-way valve. The outlet flow channel includes a first branch pipe, a second branch pipe, and a third branch pipe. One end of the first branch pipe is connected to the outlet end of the reaction chamber, and the other end of the first branch pipe is connected to the first end of the three-way valve. The second end of the three-way valve is connected to one end of the second branch pipe, and the third end of the three-way valve is connected to the waste liquid tank through the third branch pipe. A second pump body is provided on the second branch pipe, and the second pump body is connected to the pump drive module. After each addition of potassium permanganate standard solution, the pump drive module controls the second pump body to push external gas into the reaction chamber through the second branch pipe.

8. The water permanganate index detection device according to claim 1, characterized in that, The first light intensity acquisition unit includes a first photodiode, the anode of the first photodiode is grounded, and the cathode of the first photodiode is connected to the controller in sequence through a transimpedance amplifier, an impedance matching circuit, a voltage follower and an analog-to-digital converter circuit connected in series. The structure of the second light intensity acquisition unit is the same as that of the first light intensity acquisition unit.

9. The water permanganate index detection device according to claim 8, characterized in that, The transimpedance amplifier includes a feedback circuit and a first operational amplifier. The feedback circuit includes a gain resistor and a compensation capacitor connected in parallel. The cathode of the first photodiode is connected to the first end of the gain resistor, the first end of the compensation capacitor, and the inverting input of the first operational amplifier, respectively. The second end of the gain resistor and the second end of the compensation capacitor are connected to the output of the first operational amplifier, respectively. The non-inverting input of the first operational amplifier is grounded.

10. The water permanganate index detection device according to claim 9, characterized in that, The transimpedance amplifier further includes a controllable switch chip. Several feedback circuits are provided. Each controllable switch chip includes an output connection terminal, several input connection terminals, and several control input terminals. The output connection terminal is connected to the output terminal of the first operational amplifier. Each input connection terminal is connected to the cathode of the first photodiode through a corresponding feedback circuit. The gain resistors in different feedback circuits have different resistance values. The control input terminals are connected to the controller to receive a switch control signal input from the controller. The controllable switch chip switches the input connection terminal connected to the output connection terminal according to the switch control signal.

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