DPD residual chlorine detection device with anti-interference function and detection method

Abstract

The invention discloses a DPD residual chlorine detection device with an anti-interference function and a detection method.The device comprises a shell and a developing pool, a cover body is arranged at the top of the shell, a reagent inlet and an exhaust hole are formed in the cover body, the reagent inlet is connected with a reagent bottle through a reagent pipe, a reagent pump is arranged on the reagent pipe, the exhaust hole is connected with an exhaust pipe, and the reagent bottle is connected with the developing pool. An exhaust pump is arranged on the exhaust pipe, a hanging brush motor is arranged in the cover body and connected with a hanging brush, a water inlet channel is arranged at the bottom of the developing pool, a water inlet electromagnetic valve is arranged on the water inlet channel, a water outlet channel is arranged at the top of the developing pool, and a water outlet electromagnetic valve is arranged on the water outlet channel; a light-emitting diode, a reference photodiode and a measurement photodiode are arranged in the shell, a stirring motor is arranged at the bottom in the shell, the stirring motor is connected with a first magnetic stirring terminal, and a second magnetic stirring terminal is arranged at the bottom in the developing pool. The system is high in anti-interference capability, high in detection precision, good in use effect and convenient to popularize and use.

Description

Technical Field

[0001] This invention belongs to the field of water quality monitoring technology, specifically relating to a DPD residual chlorine detection device and detection method with anti-interference function. Background Technology

[0002] DPD residual chlorine detection refers to the detection of residual chlorine content in water using the DPD reagent method (N,N-diethyl-p-phenylenediamine spectrophotometry). It is widely used in drinking water, wastewater treatment, and aquaculture, and is one of the core methods for monitoring water disinfection effectiveness and microbial safety. Its core value lies in rapidly and accurately quantifying the residual chlorine with disinfecting activity in water, avoiding health risks caused by excessive residual chlorine (such as skin irritation and the production of disinfection byproducts) or microbial contamination caused by insufficient residual chlorine. The main testing method in existing technologies is spectrophotometry, which uses a spectrophotometer or an integrated DPD residual chlorine detector to measure the absorbance of the chromogenic solution at a wavelength of 510 nm (the maximum absorption wavelength of the pink compound). The accurate residual chlorine concentration is calculated using an "absorbance-concentration standard curve," suitable for laboratory or online monitoring.

[0003] However, existing technologies for DPD residual chlorine detection suffer from numerous interfering factors. For example, the solution in the colorimetric cell is easily affected by air bubbles, leading to inaccurate measurement values; during long-term titration of the colored colorimetric reagent, some of the reagent adheres to the wall and forms scale, resulting in inaccurate measurement values; and the 510nm emission light source experiences energy decay over long-term emission, also leading to inaccurate measurement values. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a DPD residual chlorine detection device and detection method with anti-interference function to address the shortcomings of the prior art. The detection device has a simple structure, reasonable design, and is easy to implement. Combined with the detection method, it can be effectively applied to the detection of residual chlorine content in water bodies. It has strong anti-interference ability, high detection accuracy, good use effect, and is easy to promote and use.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a DPD residual chlorine detection device with anti-interference function, comprising a shell and a colorimetric cell located inside the shell. A cover is provided on the top of the shell, and a reagent inlet and an exhaust port are provided on the cover. The reagent inlet is connected to a reagent bottle via a reagent tube, and a reagent pump is provided on the reagent tube. The exhaust port is connected to an exhaust pipe, and an exhaust pump is provided on the exhaust pipe. A brush motor is provided inside the cover, and a brush extending into the colorimetric cell is connected to the output shaft of the brush motor. A water inlet channel extending out of the shell is provided at the bottom of the colorimetric cell, and a water inlet electromagnetic inlet is provided on the water inlet channel. The color development tank has a water outlet channel extending out of the housing at its top, and a water outlet solenoid valve is installed on the water outlet channel. Inside the housing are a light-emitting diode (LED), a reference photodiode, and a measuring photodiode. The LED and the reference photodiode are located on the same side of the color development tank, with the reference photodiode facing the LED. The measuring photodiode is located on the other side of the color development tank and faces the LED. A stirring motor is installed at the bottom of the housing, and a first magnetic stirring terminal is connected to the output shaft of the stirring motor. A second magnetic stirring terminal, driven to rotate by the magnetic force of the first magnetic stirring terminal, is also installed at the bottom of the color development tank.

[0006] The aforementioned DPD residual chlorine detection device with anti-interference function also includes a control system. The control system includes a controller and an emission light source circuit. The input terminal of the controller is connected to a reference signal acquisition circuit and a measurement signal circuit. The emission light source circuit, reagent pump, exhaust pump, brush motor, inlet solenoid valve, outlet solenoid valve, and stirring motor are all connected to the output terminal of the controller. The light-emitting diode is connected to the emission light source circuit, the reference photodiode is connected to the reference signal acquisition circuit, and the measurement photodiode is connected to the measurement signal circuit.

[0007] The aforementioned DPD residual chlorine detection device with anti-interference function includes an emission light source circuit comprising an analog switch U1, an operational amplifier U2, a MOSFET Q1, a non-polar capacitor C1, resistors R1 and R2. Pins 1 and 6 of the analog switch U1 are connected to the signal output pins of the controller. Pin 5 of the analog switch U1 is connected to the power supply VCC. Pins 2 and 3 of the analog switch U1 are grounded. Pin 3 of the operational amplifier U2 is connected to pin 4 of the analog switch U1 via resistor R1 and is grounded via the non-polar capacitor C1. Pin 2 of the operational amplifier U2 is connected to the source of the MOSFET Q1 and is grounded via resistor R2. Pin 1 of the operational amplifier U2 is connected to the gate of the MOSFET Q1. The drain of the MOSFET Q1 is connected to the cathode of the light-emitting diode (LED), and the anode of the LED is connected to the power supply VCC.

[0008] The aforementioned DPD residual chlorine detection device with anti-interference function includes a reference signal acquisition circuit comprising operational amplifier U3, operational amplifier U4, non-polar capacitor C2, non-polar capacitor C3, resistor R3, and resistor R5. The second pin of operational amplifier U3, one end of resistor R3, and one end of non-polar capacitor C2 are all connected to the cathode of the reference photodiode. The first pin of operational amplifier U3, the other end of resistor R3, and the other end of non-polar capacitor C2 are all connected to the third pin of operational amplifier U4. The third pin of operational amplifier U3 and the anode of the reference photodiode are both grounded. The second and first pins of operational amplifier U4 are both connected to one end of resistor R5. The other end of resistor R5 is connected to the signal input pin of the controller and grounded through non-polar capacitor C3.

[0009] The aforementioned DPD residual chlorine detection device with anti-interference function includes a measurement signal circuit comprising operational amplifier U5, operational amplifier U6, non-polar capacitors C4, C5, C6, C7, and C8, resistors R6, R7, R8, R9, R10, and R11. Pin 2 of operational amplifier U5, one end of resistor R6, and one end of non-polar capacitor C4 are all connected to the cathode of the measuring photodiode. Pin 1 of operational amplifier U5, the other end of resistor R6, and the other end of non-polar capacitor C4 are all connected to one end of non-polar capacitor C5. Pin 3 of operational amplifier U5 and... The anodes of the photodiodes are all grounded. One end of resistor R8 is connected to the other end of non-polarized capacitor C5 and grounded through resistor R7. The third pin of operational amplifier U6 is connected to the other end of resistor R8 and grounded through non-polarized capacitor C6. The second pin of operational amplifier U6, one end of resistor R10, and one end of non-polarized capacitor C7 are all connected to one end of resistor R9, and the other end of resistor R9 is grounded. The first pin of operational amplifier U6, the other end of resistor R10, and the other end of non-polarized capacitor C7 are all connected to one end of resistor R11. The other end of resistor R11 is connected to the signal input pin of the controller and grounded through non-polarized capacitor C8.

[0010] The aforementioned DPD residual chlorine detection device with anti-interference function uses a transparent glass colorimetric cell.

[0011] In the aforementioned DPD residual chlorine detection device with anti-interference function, the reagent tube extends into the colorimetric cell through the reagent inlet.

[0012] The aforementioned DPD residual chlorine detection device with anti-interference function includes a brush used to clean the dirt on the inner wall of the colorimetric tank.

[0013] In the aforementioned DPD residual chlorine detection device with anti-interference function, the reference photodiode is used to monitor the attenuation of the light emission intensity of the light-emitting diode.

[0014] This invention also discloses a method for detecting residual chlorine in DPD with anti-interference function, using the above-mentioned detection device, and the detection method includes the following steps: Step 1: Open the inlet solenoid valve and the outlet solenoid valve. The water sample to be tested enters the colorimetric cell through the inlet channel and overflows through the outlet channel. Step 2: Turn on the brush motor. The brush motor drives the brush to clean the inner wall of the color developing tank for a preset time. Step 3: Turn off the brush motor. The brush motor will drive the brush back to a position that will not affect the propagation of the optical signal. Step 4: Close the inlet solenoid valve and the outlet solenoid valve to complete the sampling of the water sample to be tested in the colorimetric cell; Step 5: Turn on the reagent pump, exhaust pump, and stirring motor. Under the action of the reagent pump, the DPD reagent in the reagent bottle enters the colorimetric cell through the reagent tube; the stirring motor drives the first magnetic stirring terminal to rotate, and the first magnetic stirring terminal drives the second magnetic stirring terminal to rotate, so that the DPD reagent and the water sample to be tested are fully mixed and reacted to form a mixture; at the same time, under the action of the exhaust pump, the air bubbles in the water sample to be tested and the air in the colorimetric cell are discharged through the exhaust pipe; the reagent pump is turned off after running for a preset time. Step 6: Turn on the LED and measure the light signal transmitted through the mixture by the photodiode; simultaneously, the reference photodiode monitors the initial light signal of the LED. Step 7: Obtain the residual chlorine concentration by measuring the absorbance of the mixed solution, thus realizing DPD residual chlorine detection; Step 8: After the test is completed, turn off the exhaust pump, stirring motor, and LED; Step 9: Open the inlet solenoid valve and the outlet solenoid valve. The water sample to be tested will rinse the colorimetric cell and complete the sample replacement, ready for the next round of testing.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The detection device of the present invention has a simple structure, reasonable design, and is easy to implement.

[0016] 2. This invention uses a brush motor to drive a brush to clean the scale on the inner wall of the colorimetric tank in a timely manner, avoiding scale buildup of colorimetric reagent that could lead to inaccurate measurement values.

[0017] 3. The present invention uses a stirring motor to drive the first magnetic stirring terminal and the second magnetic stirring terminal to rotate, so as to fully mix the DPD reagent and the water sample to be tested; at the same time, the air pressure in the colorimetric cell is reduced by the exhaust pump and exhaust pipe, so that the air bubbles in the mixture are discharged, avoiding the influence of air bubbles that may cause inaccurate measurement values.

[0018] 4. This invention uses a reference photodiode to collect a reference signal, which can promptly detect the energy decay of the light-emitting diode. At the same time, by changing the working mode of the light-emitting diode, the light-emitting diode is only turned on to emit pulsed light after the DPD reagent and the water sample to be tested are fully mixed and defoamed, and is turned off immediately after the test is completed. This can extend the service life of the light-emitting diode and avoid inaccurate measurement values ​​caused by energy decay due to long-term emission of the light source.

[0019] 5. This invention can be effectively applied to the detection of residual chlorine content in water bodies. It has strong anti-interference ability, high detection accuracy, good performance, and is easy to promote and use.

[0020] In summary, the detection device of the present invention has a simple structure, reasonable design, and convenient implementation. Combined with the detection method, it can be effectively applied to the detection of residual chlorine content in water bodies. It has strong anti-interference ability, high detection accuracy, good performance, and is easy to promote and use. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the detection device of the present invention.

[0022] Figure 2 This is a schematic diagram of the control system of the present invention.

[0023] Figure 3 This is a schematic diagram of the emission light source circuit of the present invention.

[0024] Figure 4 This is a schematic diagram of the reference signal acquisition circuit of the present invention.

[0025] Figure 5 This is a schematic diagram of the signal measurement circuit of the present invention.

[0026] Figure 6 This is a flowchart of the detection method of the present invention.

[0027] Explanation of reference numerals in the attached figures: 1—Shell; 2—Developing cell; 3—Lid; 4—Reagent inlet; 5—Vent vent; 6—Reagent tube; 7—Reagent bottle; 8—Reagent pump; 9—Exhaust pipe; 10—Exhaust pump; 11—Hanging brush motor; 12—Hanging brush; 13—Water inlet channel; 14—Water inlet solenoid valve; 15—Water outlet channel; 16—Water outlet solenoid valve; 17—Light emission diode; 18—Reference photodiode; 19—Measuring photodiode; 20—Stirring motor; 21—First magnetic stirring terminal; 22—Second magnetic stirring terminal; 23—Controller; 24—Emitting light source circuit; 25—Reference signal acquisition circuit; 26—Measurement signal circuit. Detailed Implementation

[0028] like Figure 1 As shown, the DPD residual chlorine detection device with anti-interference function of the present invention includes a housing 1 and a colorimetric cell 2 located inside the housing 1. A cover 3 is provided on the top of the housing 1. A reagent inlet 4 and an exhaust port 5 are provided on the cover 3. The reagent inlet 4 is connected to a reagent bottle 7 through a reagent tube 6. A reagent pump 8 is provided on the reagent tube 6. An exhaust pipe 9 is connected to the exhaust port 5. An exhaust pump 10 is provided on the exhaust pipe 9. A brush motor 11 is provided inside the cover 3. A brush 12 extending into the colorimetric cell 2 is connected to the output shaft of the brush motor 11. A water inlet channel 13 extending out of the housing 1 is provided at the bottom of the colorimetric cell 2. A water inlet solenoid valve 14 is provided on the water inlet channel 13. A water inlet solenoid valve 14 is provided on the top of the colorimetric cell 2. A water outlet channel 15 extends out of the housing 1, and a water outlet solenoid valve 16 is installed on the water outlet channel 15. A light-emitting diode 17, a reference photodiode 18, and a measuring photodiode 19 are installed inside the housing 1. The light-emitting diode 17 and the reference photodiode 18 are located on the same side of the color development cell 2, and the reference photodiode 18 is directly opposite the light-emitting diode 17. The measuring photodiode 19 is located on the other side of the color development cell 2 and is directly opposite the light-emitting diode 17. A stirring motor 20 is installed at the bottom inside the housing 1. A first magnetic stirring terminal 21 is connected to the output shaft of the stirring motor 20. A second magnetic stirring terminal 22 is installed at the bottom inside the color development cell 2 and is driven to rotate by the magnetic force of the first magnetic stirring terminal 21.

[0029] This embodiment also includes a control system, such as... Figure 2 As shown, the control system includes a controller 23 and a light source circuit 24. The input terminal of the controller 23 is connected to a reference signal acquisition circuit 25 and a measurement signal circuit 26. The light source circuit 24, reagent pump 8, exhaust pump 10, brush motor 11, water inlet solenoid valve 14, water outlet solenoid valve 16, and stirring motor 20 are all connected to the output terminal of the controller 23. The light-emitting diode 17 is connected to the light source circuit 24, the reference photodiode 18 is connected to the reference signal acquisition circuit 25, and the measurement photodiode 19 is connected to the measurement signal circuit 26.

[0030] In this embodiment, as Figure 3 As shown, the emitting light source circuit 24 includes an analog switch U1, an operational amplifier U2, a MOSFET Q1, a non-polar capacitor C1, resistors R1 and R2. The first and sixth pins of the analog switch U1 are connected to the signal output pins of the controller 23. The fifth pin of the analog switch U1 is connected to the power supply VCC. The second and third pins of the analog switch U1 are grounded. The third pin of the operational amplifier U2 is connected to the fourth pin of the analog switch U1 through resistor R1 and grounded through the non-polar capacitor C1. The second pin of the operational amplifier U2 is connected to the source of the MOSFET Q1 and grounded through resistor R2. The first pin of the operational amplifier U2 is connected to the gate of the MOSFET Q1. The drain of the MOSFET Q1 is connected to the cathode of the light-emitting diode 17. The anode of the light-emitting diode 17 is connected to the power supply VCC.

[0031] In specific implementation, the light source circuit 24 is the driving circuit for the light-emitting diode 17. The analog switch U1 is powered by the power supply VCC. The first pin (NO) of the analog switch U1 is connected to the DAC inside the controller 23. The DAC can output a voltage value between 0 and VCC. In order to improve the overall service life of the instrument, the light-emitting diode 17 is driven by a pulse signal. The pulse signal waveform can be generated by controlling the high and low levels of IO1 of the controller 23. When IO1 is high, COM is connected to the DAC. When IO1 is low, COM is connected to GND and outputs a low level. The COM pin, connected to resistor R1 and non-polarized capacitor C1, forms a low-pass filter to remove spikes and glitches from the pulse waveform, ensuring signal stability. This filter is then connected to pin 3 (positive input) of operational amplifier U2. Pin 2 (negative input) of operational amplifier U2 is connected to resistor R2 and then to GND. Pin 1 (output) of operational amplifier U2 is connected to the gate of MOSFET Q1 and then to resistor R2. The drain of MOSFET Q1 is connected to an LED and then to VCC. This circuit is a constant current source circuit. When IO1=1, COM is connected to the DAC. At this point, the voltage at the positive input terminal of operational amplifier U2 is DAC. Operational amplifier U2 introduces negative feedback, meaning the voltage at the inverting input terminal equals the voltage at the positive input terminal. That is, the voltage across resistor R2 is DAC, and the current flowing through resistor R2 is I1 = DAC / R2. Since the current flowing through LED 17 is the same as that through resistor R2, the current when LED 17 is emitting light is also I1. When IO1 is low, COM is connected to GND, and the voltage at the positive input terminal of operational amplifier U2 is 0V. By analogy, the current flowing through resistor R2 is 0, and LED 17 is off. Thus, the LED flashes. When testing different concentrations, only the value of DAC needs to be adjusted to meet the detection requirements of each range.

[0032] In this embodiment, as Figure 4 As shown, the reference signal acquisition circuit 25 includes operational amplifier U3, operational amplifier U4, non-polar capacitor C2, non-polar capacitor C3, resistor R3, and resistor R5. The second pin of operational amplifier U3, one end of resistor R3, and one end of non-polar capacitor C2 are all connected to the cathode of reference photodiode 18. The first pin of operational amplifier U3, the other end of resistor R3, and the other end of non-polar capacitor C2 are all connected to the third pin of operational amplifier U4. The third pin of operational amplifier U3 and the anode of reference photodiode 18 are both grounded. The second pin and the first pin of operational amplifier U4 are both connected to one end of resistor R5. The other end of resistor R5 is connected to the signal input pin of controller 23 and grounded through non-polar capacitor C3.

[0033] In practical implementation, the reference signal acquisition circuit 25 detects the luminous intensity of the light-emitting diode 17. The reference photodiode 18 is connected to pin 2 (negative input) of operational amplifier U3, and then connected to a non-polar capacitor C2 and a resistor R3. Pin 3 (positive input) of operational amplifier U3 is connected to GND, forming a current sampling circuit. Resistor R3 is the sampling resistor, and non-polar capacitor C2 is the filter capacitor. Let the induced current be I2, which is the voltage at pin 1 (output) of operational amplifier U3. Then connect pin 3 (positive input) of operational amplifier U4, and pin 2 (negative input) of operational amplifier U4 to pin 1 (output) to form a voltage follower, which transmits V1 to the output of operational amplifier U4. Then connect resistor R5 and non-polar capacitor C3 to filter the signal and then collect the signal to ADC2 of controller 23.

[0034] In this embodiment, as Figure 5As shown, the measurement signal circuit 26 includes operational amplifier U5, operational amplifier U6, non-polar capacitors C4, C5, C6, C7, and C8, resistors R6, R7, R8, R9, R10, and R11. The second pin of operational amplifier U5, one end of resistor R6, and one end of non-polar capacitor C4 are all connected to the cathode of the measurement photodiode 19. The first pin of operational amplifier U5, the other end of resistor R6, and the other end of non-polar capacitor C4 are all connected to one end of non-polar capacitor C5. The third pin of operational amplifier U5 is connected to the measurement photodiode 19. The anodes of all components are grounded. One end of resistor R8 is connected to the other end of non-polar capacitor C5 and grounded through resistor R7. The third pin of operational amplifier U6 is connected to the other end of resistor R8 and grounded through non-polar capacitor C6. The second pin of operational amplifier U6, one end of resistor R10, and one end of non-polar capacitor C7 are all connected to one end of resistor R9, and the other end of resistor R9 is grounded. The first pin of operational amplifier U6, the other end of resistor R10, and the other end of non-polar capacitor C7 are all connected to one end of resistor R11. The other end of resistor R11 is connected to the signal input pin of controller 23 and grounded through non-polar capacitor C8.

[0035] In practice, photodiode 19 is connected to pin 2 (negative input) of operational amplifier U5, then a non-polar capacitor C4 and resistor R6 are connected. Pin 3 (positive input) of operational amplifier U5 is connected to GND, forming a current sampling circuit. Resistor R6 is the sampling resistor, and non-polar capacitor C4 is the filter capacitor. Let the induced current be I3, which is the voltage at pin 1 (output) of operational amplifier U5. The induced current measured at this time includes the dark current I0 inherent in the photodiode itself, which is the current signal inherent in the photodiode in absolute darkness. Since the dark current is a DC signal and the driving signal is an AC signal, a high-pass filter composed of a non-polar capacitor C5 and a resistor R7, and a low-pass filter composed of a resistor R8 and a non-polar capacitor C6 are designed at the output of operational amplifier U5. By using the filtering and frequency selection method, the DC dark current interference inside the photodiode is removed. Then, pin 3 (positive input) of operational amplifier U6 is connected, and pin 2 (negative input) of operational amplifier U6 is connected to resistor R9, resistor R10, and non-polar capacitor C7 to form a signal amplification circuit with an amplification factor of 1 + R10 / R9. Finally, pin 1 (output) of operational amplifier U6 is connected to resistor R11 and non-polar capacitor C8 for filtering, and the measured signal is acquired to ADC1 of controller 23.

[0036] The above-described signal-driven method can extend the lifespan of the detection device. In signal acquisition, the illumination condition at the driving end is monitored by comparing the reference signal acquisition. The aging limit of the light source is set in the controller to ensure measurement accuracy. When the illumination intensity decays beyond the limit, recalibration is required, and a new initial illumination intensity is updated. At the measurement signal end, the interference of DC dark current is removed, and the signal frequency selection is designed according to the driving frequency of the emitted light, which improves the anti-interference ability and detection accuracy of the detection device.

[0037] In this embodiment, the color development tank 2 is made of transparent glass.

[0038] In this embodiment, the reagent tube 6 extends into the colorimetric cell 2 through the reagent inlet 4.

[0039] In this embodiment, the brush 12 is used to clean the dirt on the inner wall of the color development tank 2.

[0040] In this embodiment, the reference photodiode 18 is used to monitor the attenuation of the luminous intensity of the light-emitting diode 17.

[0041] like Figure 6 As shown, the DPD residual chlorine detection method with anti-interference function of the present invention includes the following steps: Step 1: Open the inlet solenoid valve 14 and the outlet solenoid valve 16. The water sample to be tested enters the colorimetric cell 2 through the inlet channel 13 and overflows through the outlet channel 15. Step 2: Turn on the brush motor 11. The brush motor 11 drives the brush 12 to clean the inner wall of the color development tank 2 for a preset time. In practice, the preset duration is set to 10 seconds. The brush motor 11 drives the brush 12 to clean the scale on the inner wall of the colorimetric tank 2 in a timely manner, so as to avoid the colorimetric reagent from being partially stuck on the wall and causing inaccurate measurement values.

[0042] Step 3: Turn off the brush motor 11. The brush motor 11 drives the brush 12 to reset to a position that does not affect the propagation of the optical signal. Step 4: Close the inlet solenoid valve 14 and the outlet solenoid valve 16 to complete the sampling of the water sample to be tested in the colorimetric cell 2. Step 5: Turn on the reagent pump 8, exhaust pump 10, and stirring motor 20. Under the action of reagent pump 8, the DPD reagent in reagent bottle 7 enters the colorimetric cell 2 through reagent tube 6. Stirring motor 20 drives the first magnetic stirring terminal 21 to rotate, and the first magnetic stirring terminal 21 drives the second magnetic stirring terminal 22 to rotate, so that the DPD reagent and the water sample to be tested are fully mixed and reacted to form a mixture. At the same time, under the action of exhaust pump 10, air bubbles in the water sample to be tested and air in the colorimetric cell 2 are discharged through exhaust pipe 9. The reagent pump 8 is turned off after running for a preset time. In practice, the reagent pump 8 operates for a preset time to ensure that the DPD reagent reacts completely with the water sample to be tested, but not excessively, otherwise it will lead to an excessive amount of DPD reagent, thereby shortening the maintenance cycle of the detection device. The DPD reagent and the water sample to be tested are thoroughly stirred by rotating the second magnetic stirring terminal 22; at the same time, the air pressure in the colorimetric cell 2 is reduced by the exhaust pump 10 to expel air bubbles in the mixture, avoiding inaccurate measurement values ​​due to the influence of air bubbles.

[0043] Step 6: Turn on the light-emitting diode 17, and measure the light signal transmitted through the mixture by the photodiode 19; at the same time, the reference photodiode 18 monitors the initial light signal of the light-emitting diode 17. In practice, since the light-emitting diode 17 experiences signal attenuation after prolonged use, the light intensity attenuation is deduced from the reference signal value of the reference photodiode 18 during each measurement. If the attenuation exceeds the measurement accuracy, recalibration is required. This is to avoid inaccurate measurement values ​​caused by energy attenuation due to prolonged illumination of the light-emitting diode 17.

[0044] Step 7: Obtain the residual chlorine concentration by measuring the absorbance of the mixed solution, thus realizing DPD residual chlorine detection; Step 8: After the test is completed, turn off the exhaust pump 10, the stirring motor 20 and the light-emitting diode 17; Step 9: Open the inlet solenoid valve 14 and the outlet solenoid valve 16. The water sample to be tested will rinse the colorimetric cell 2 and complete the sample replacement, ready for the next round of testing.

[0045] In practice, the opening or closing of the light source circuit 24, reagent pump 8, exhaust pump 10, brush motor 11, water inlet solenoid valve 14, water outlet solenoid valve 16, and stirring motor 20 are all controlled by controller 23.

[0046] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A DPD residual chlorine detection device with anti-interference function, characterized in that: The device includes a housing (1) and a colorimetric cell (2) located inside the housing (1). A cover (3) is provided on the top of the housing (1). A reagent inlet (4) and an exhaust port (5) are provided on the cover (3). A reagent bottle (7) is connected to the reagent inlet (4) through a reagent tube (6). A reagent pump (8) is provided on the reagent tube (6). An exhaust pipe (9) is connected to the exhaust port (5). An exhaust pump (10) is provided on the exhaust pipe (9). A brush motor (11) is provided inside the cover (3). A brush (12) that extends into the colorimetric cell (2) is connected to the output shaft of the brush motor (11). A water inlet channel (13) extending out of the housing (1) is provided at the bottom of the colorimetric cell (2). A water inlet solenoid valve (14) is provided on the water inlet channel (13). An exhaust port extending out of the housing (1) is provided at the top of the colorimetric cell (2). The water outlet channel (15) outside the housing (1) is provided with a water outlet solenoid valve (16). The housing (1) is provided with a light-emitting diode (17), a reference photodiode (18) and a measuring photodiode (19). The light-emitting diode (17) and the reference photodiode (18) are located on the same side of the color development cell (2), and the reference photodiode (18) is directly opposite the light-emitting diode (17). The measuring photodiode (19) is located on the other side of the color development cell (2) and is directly opposite the light-emitting diode (17). The bottom of the housing (1) is provided with a stirring motor (20). The output shaft of the stirring motor (20) is connected to a first magnetic stirring terminal (21). The bottom of the color development cell (2) is provided with a second magnetic stirring terminal (22) that is driven to rotate by the magnetic force of the first magnetic stirring terminal (21).

2. The DPD residual chlorine detection device with anti-interference function according to claim 1, characterized in that: It also includes a control system, which includes a controller (23) and a light source circuit (24). The input terminal of the controller (23) is connected to a reference signal acquisition circuit (25) and a measurement signal circuit (26). The light source circuit (24), reagent pump (8), exhaust pump (10), brush motor (11), water inlet solenoid valve (14), water outlet solenoid valve (16) and stirring motor (20) are all connected to the output terminal of the controller (23). The light-emitting diode (17) is connected to the light source circuit (24). The reference photodiode (18) is connected to the reference signal acquisition circuit (25). The measurement photodiode (19) is connected to the measurement signal circuit (26).

3. The DPD residual chlorine detection device with anti-interference function according to claim 2, characterized in that: The light source circuit (24) includes an analog switch U1, an operational amplifier U2, a MOS transistor Q1, a non-polar capacitor C1, a resistor R1, and a resistor R2. The first and sixth pins of the analog switch U1 are connected to the signal output pins of the controller (23). The fifth pin of the analog switch U1 is connected to the power supply VCC. The second and third pins of the analog switch U1 are grounded. The third pin of the operational amplifier U2 is connected to the fourth pin of the analog switch U1 through the resistor R1 and grounded through the non-polar capacitor C1. The second pin of the operational amplifier U2 is connected to the source of the MOS transistor Q1 and grounded through the resistor R2. The first pin of the operational amplifier U2 is connected to the gate of the MOS transistor Q1. The drain of the MOS transistor Q1 is connected to the cathode of the light-emitting diode (17). The anode of the light-emitting diode (17) is connected to the power supply VCC.

4. The DPD residual chlorine detection device with anti-interference function according to claim 2, characterized in that: The reference signal acquisition circuit (25) includes an operational amplifier U3, an operational amplifier U4, a non-polar capacitor C2, a non-polar capacitor C3, a resistor R3, and a resistor R5. The second pin of the operational amplifier U3, one end of the resistor R3, and one end of the non-polar capacitor C2 are all connected to the cathode of the reference photodiode (18). The first pin of the operational amplifier U3, the other end of the resistor R3, and the other end of the non-polar capacitor C2 are all connected to the third pin of the operational amplifier U4. The third pin of the operational amplifier U3 and the anode of the reference photodiode (18) are both grounded. The second pin and the first pin of the operational amplifier U4 are both connected to one end of the resistor R5. The other end of the resistor R5 is connected to the signal input pin of the controller (23) and is grounded through the non-polar capacitor C3.

5. The DPD residual chlorine detection device with anti-interference function according to claim 2, characterized in that: The measurement signal circuit (26) includes operational amplifier U5, operational amplifier U6, non-polar capacitors C4, C5, C6, C7, and C8, resistors R6, R7, R8, R9, R10, and R11. The second pin of operational amplifier U5, one end of resistor R6, and one end of non-polar capacitor C4 are all connected to the cathode of the measurement photodiode (19). The first pin of operational amplifier U5, the other end of resistor R6, and the other end of non-polar capacitor C4 are all connected to one end of non-polar capacitor C5. The third pin of operational amplifier U5 is connected to the measurement photodiode (19). The anodes of all are grounded. One end of the resistor R8 is connected to the other end of the non-polar capacitor C5 and grounded through the resistor R7. The third pin of the operational amplifier U6 is connected to the other end of the resistor R8 and grounded through the non-polar capacitor C6. The second pin of the operational amplifier U6, one end of the resistor R10, and one end of the non-polar capacitor C7 are all connected to one end of the resistor R9. The other end of the resistor R9 is grounded. The first pin of the operational amplifier U6, the other end of the resistor R10, and the other end of the non-polar capacitor C7 are all connected to one end of the resistor R11. The other end of the resistor R11 is connected to the signal input pin of the controller (23) and grounded through the non-polar capacitor C8.

6. The DPD residual chlorine detection device with anti-interference function according to claim 1, characterized in that: The color development tank (2) is made of transparent glass.

7. The DPD residual chlorine detection device with anti-interference function according to claim 1, characterized in that: The reagent tube (6) extends into the colorimetric cell (2) through the reagent inlet (4).

8. The DPD residual chlorine detection device with anti-interference function according to claim 1, characterized in that: The brush (12) is used to clean the dirt on the inner wall of the color developing tank (2).

9. The DPD residual chlorine detection device with anti-interference function according to claim 1, characterized in that: The reference photodiode (18) is used to monitor the luminous intensity decay of the light-emitting diode (17).

10. A method for detecting residual chlorine in DPD with anti-interference function, characterized in that, Using the detection device as described in claim 1, the detection method includes the following steps: Step 1: Open the inlet solenoid valve (14) and outlet solenoid valve (16). The water sample to be tested enters the colorimetric cell (2) through the inlet channel (13) and overflows through the outlet channel (15). Step 2: Turn on the brush motor (11), and the brush motor (11) drives the brush (12) to clean the inner wall of the color development tank (2) for a preset time. Step 3: Turn off the brush motor (11). The brush motor (11) drives the brush (12) to reset to a position that does not affect the propagation of the optical signal. Step 4: Close the inlet solenoid valve (14) and outlet solenoid valve (16) to complete the sampling of the water sample to be tested in the colorimetric cell (2); Step 5: Turn on the reagent pump (8), exhaust pump (10) and stirring motor (20). Under the action of the reagent pump (8), the DPD reagent in the reagent bottle (7) enters the colorimetric cell (2) through the reagent tube (6). The stirring motor (20) drives the first magnetic stirring terminal (21) to rotate, and the first magnetic stirring terminal (21) drives the second magnetic stirring terminal (22) to rotate, so that the DPD reagent and the water sample to be tested are fully mixed and reacted to form a mixture. At the same time, under the action of the exhaust pump (10), the air bubbles in the water sample to be tested and the air in the colorimetric cell (2) are discharged through the exhaust pipe (9). The reagent pump (8) is turned off after running for a preset time. Step 6: Turn on the light-emitting diode (17), and measure the light signal transmitted through the mixture by the photodiode (19); at the same time, the reference photodiode (18) monitors the initial light signal of the light-emitting diode (17); Step 7: Obtain the residual chlorine concentration by measuring the absorbance of the mixed solution, thus realizing DPD residual chlorine detection; Step 8: After the test is completed, turn off the exhaust pump (10), stirring motor (20) and light-emitting diode (17). Step 9: Open the inlet solenoid valve (14) and outlet solenoid valve (16) to rinse the colorimetric cell (2) with the water sample to be tested and complete the sample replacement, ready for the next round of testing.

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