Wireless rapid detection device and detection method for heavy metals in water

Abstract

The invention discloses a wireless rapid detection device and method for heavy metals in water, and belongs to the technical field of heavy metal detection. The system is composed of a heavy metal detection front end, an electrochemical detection circuit, a microcontroller minimum system and a heavy metal wireless detection terminal. The heavy metal detection front end is composed of a three-electrode system with a pre-enrichment-free nano modified electrode as a working electrode, a platinum sheet electrode as an auxiliary electrode and a saturated calomel electrode as a reference electrode. The electrochemical detection circuit consists of a signal generation circuit, a constant potential rectifier circuit, a signal conditioning circuit and a signal acquisition circuit; the microcontroller minimum system is composed of a main control chip, a CLK clock circuit, an SWD programming circuit, an RST reset circuit and a power supply circuit. The heavy metal wireless detection terminal consists of a detection terminal LoRa wireless communication module, a heavy metal detection upper computer program, communication configuration, test parameter configuration, data processing and data storage; the detection device can realize remote wireless rapid detection of the heavy metal concentration in the water body.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy metal detection, and in particular relates to a wireless rapid detection device and a detection method for heavy metals in water. Background Art

[0003] In recent years, with the continuous development of detection technology, heavy metal detection methods have been continuously improved and developed. For example, atomic absorption spectroscopy (AAS), inductively coupled plasma mass spectrometry (ICP-MS), energy dispersive X-ray fluorescence spectroscopy (XRF), ultraviolet-visible spectrophotometry (UV), etc. These detection methods have the advantages of high sensitivity and accurate results, and are often used as reference standards for detection results. However, there are problems such as long detection cycle, large instrument size, high price and the need for professional operation. In contrast, the electrochemical method is low-cost and environmentally friendly. It is a recognized trace, rapid, sensitive and accurate detection method with significant advantages such as rapid detection, portability, and easy operation by non-professionals. It is widely used in the field of heavy metal detection.

[0004] A Chinese patent with the authorization announcement number "CN107305194B" discloses a heavy metal detection electrolytic cell based on an electrochemical method, including a microcontroller, a constant voltage generator, a differential amplifier, an auxiliary electrode, a reference electrode, a working electrode and a conversion circuit. The microcontroller converts a digital signal into a voltage signal through a D / A converter to control the operation of the constant voltage generator. The differential amplifier converts the voltage signal into a digital signal through an A / D converter and sends it to the microcontroller. During the enrichment stage of the electrochemical detection, the conversion circuit outputs a constant voltage to the auxiliary electrode. During the dissolution stage of the electrochemical detection, the conversion circuit outputs a current to the working electrode, and the reference electrode inputs a variable voltage to the differential amplifier. The variable voltage forms a function with time. It can be inferred from the Nernst equation that the function has several constant voltage zones, and the time length of the constant voltage zone is proportional to the content of the metal dissolved at this constant voltage. The microcontroller can judge the content of this metal according to the time of dissolution of the metal in this constant voltage zone. This detection system has the characteristics of high dissolution volume and high precision. However, based on the traditional stripping voltammetry method, enrichment operation is required during the detection process. Heavy metal ions are reduced to zero valence through electrodeposition. Although the sensitivity of the detection is improved, the detection time and power consumption are increased. In addition, the data results of the detection system cannot be transmitted remotely, and there is a lack of supporting host computer software for operation and display, which makes the detection process complicated. Therefore, in heavy metal detection devices, how to reduce the detection time, increase the detection speed, and simplify the detection process are important issues that need to be solved in this field. Summary of the invention

[0005] In order to solve the problems of long detection time, high power consumption, complex detection process and inability to remotely transmit data in the existing heavy metal detection technology in water, the present invention provides a wireless heavy metal rapid detection device and detection method in water, which can wirelessly detect heavy metals in water at multiple locations, and analyze and calculate the concentration of heavy metals in water.

[0006] The wireless rapid detection device for heavy metals in water described in the present invention can be used for remote wireless detection of heavy metal concentrations in water, and is composed of a heavy metal detection front end 1, an electrochemical detection circuit 2, a microcontroller minimum system 3 and a heavy metal wireless detection terminal 4; the heavy metal detection front end 1 uses a nano-modified electrode without pre-enrichment as a working electrode (Work Electrode, WE), a platinum sheet electrode as an auxiliary electrode (Counter Electrode, CE), and a saturated calomel electrode as a reference electrode (Reference Electrode). Electrode, RE) is composed of a three-electrode system; the electrochemical detection circuit 2 is composed of a signal generating circuit 21, a constant potential instrument circuit 22, a signal conditioning circuit 23 and a signal acquisition circuit 24; the microcontroller minimum system 3 is composed of a detection device LoRa wireless communication module 31, a main control chip 32, a CLK clock circuit 33, a SWD burning circuit 34, a RST system reset circuit 35 and a power supply circuit 36; the heavy metal wireless detection terminal 4 is composed of a detection terminal LoRa wireless communication module 41, a heavy metal detection host computer program 42, a communication configuration 43, a test parameter configuration 44, a data processing 45, and a data storage 46; the reference electrode and the auxiliary electrode of the heavy metal detection front end 1 are connected to the constant potential instrument circuit 22, and the working electrode is connected The signal conditioning circuit 23 is connected, the signal generating circuit 21 is respectively connected to the constant potential instrument circuit 22 and the main control chip 32, the signal acquisition circuit 24 is respectively connected to the signal conditioning circuit 23 and the main control chip 32, and the power supply circuit 36 ​​is respectively connected to the signal generating circuit 21, the constant potential instrument circuit 22, the signal conditioning circuit 23, the signal acquisition circuit 24, the detection device LoRa wireless communication module 31, the main control chip 32 and the detection terminal LoRa wireless communication module 41; the detection terminal LoRa wireless module 41 is connected to the computer end through the serial port to USB interface, and the data is transmitted to the heavy metal detection host computer program 42 in the computer end; the wireless heavy metal rapid detection device in water uses a non-pre-enriched nano-modified electrode based on differential pulse stripping voltammetry (DPASV) to detect heavy metals in water.

[0007] The present invention uses nano-modified electrodes without pre-enrichment and detects heavy metals based on the differential pulse stripping voltammetry in the electrochemical method. It can continuously detect the heavy metal concentrations in multiple water bodies and can display the concentrations of heavy metals in the detected water bodies in real time on a host computer program. It can have a high response current and detection accuracy without the need for pre-enrichment operation, and has the characteristics of high detection accuracy, fast detection, simple process and low power consumption.

[0008] like Figure 2 As shown, the power supply circuit 36 ​​is composed of a power input circuit, a +3.3V power supply circuit, a +5V and -5V power supply circuit, a +5V_AVDD and a +5V_DVDD power supply circuit, and serves as the power supply for the signal generating circuit 21, the constant potential meter circuit 22, the signal conditioning circuit 23, the signal acquisition circuit 24, the detection device LoRa wireless communication module 31, the main control chip 32 and the detection terminal LoRa wireless communication module 41, and includes a total of 5 voltage levels of +3.3V, +5V, -5V, +5V_AVDD, and +5V_DVDD. Among them, the +3.3V voltage is used as the power supply for the detection device LoRa wireless communication module 31, the main control chip 32 and the detection terminal LoRa wireless communication module 41; the +5V voltage and the -5V voltage are used as the bipolar power supply of the operational amplifier in the constant potential meter circuit 22, the signal conditioning circuit 23 and other circuits; and the +5V_DVDD and +5V_AVDD are used as the power supply for the signal generating circuit 21 and the signal acquisition circuit 24.

[0009] like Figure 2As shown in (a), the power input circuit (VCC) is composed of a polymer lithium battery socket U23, a USB power socket USB1, a TP4056 charging protection chip U7, a PMOS tube Q1, a green light-emitting diode LED1, a red light-emitting diode LED2, a Schottky diode D5, a resistor and a capacitor. Pin 1 VBAT of the battery socket U23 is connected to the positive electrode of the polymer lithium battery, and pin 2 is connected to AGND and the negative electrode of the polymer lithium battery; pins 1 and 6 of the USB power socket USB1 are connected to AGND (analog ground), pins 2 and 5 are connected to VIN_5V, and pins 3 and 4 are connected to AGND through resistors R13 and R14 (both 5.1kΩ) respectively; Pins 1 and 3 of the TP4056 charging protection chip are directly connected to AGND, pin 2 is connected to AGND through resistor R11 (5kΩ), pins 4 and 8 are connected to VIN_5V through resistor R17 (0.4Ω), pins 4 and 8 are connected to AGND through parallel filter capacitors C32 (100nF) and capacitor C64 (10μF), pin 5 is connected to VBAT, and pin 5 is connected to AGND through filter capacitor C35 (1μF), pin 6 is connected to VIN_5V pin through resistor R19 (1kΩ), green light-emitting diode LED1 and resistor R17 (0.4Ω), and pin 7 is connected to VIN_5V pin through resistor R18 (1kΩ), red light-emitting diode LED2 and resistor R19 (0.4Ω). The diode LED2 and the resistor R17 (0.4Ω) are connected to the VIN_5V pin, and the pin 9 is left floating; the anode of the Schottky diode D5 is connected to VIN_5V, and the cathode is connected to VCC; the source D of the PMOS tube Q1 is connected to VBAT, the gate G is connected to AGND through the resistor R21 (2kΩ), the gate G is also connected to VIN_5V through the resistor R22 (100Ω), the source S is connected to VCC, and the source S is also connected to AGND through the parallel filter capacitors C33 (10μF) and C34 (100nF); according to the composition of the input circuit, the VCC voltage can be divided into three working conditions: (1) The USB power socket USB1 is connected to the external USB data cable, and the battery socket U23 is not connected External polymer lithium battery; at this time, the voltage of pins 2 and 5 of the power socket USB1 is the USB voltage, that is, the VIN_5V pin is the USB voltage (+5V). Since the battery socket U23 is not connected to the polymer lithium battery and is suspended, the VBAT voltage of pin 1 of the battery socket U23 is 0V. Since the VIN_5V pin is directly connected to the VCC pin through the Schottky diode D5, the VCC voltage is the USB voltage minus the voltage drop of the Schottky diode D5. Since the voltage drop of the Schottky diode D5 is very small, the VCC voltage is +5V. In this case, the gate G voltage of the PMOS tube Q1 is VIN_5V, which is obtained by dividing the resistor R22 (100Ω) and the resistor R21 (2kΩ), which is +4.8V; the source S voltage is VCC. Because the voltage difference between the gate G and the source S is greater than the on-voltage of the PMOS tube Q1 (-0.7V), the PMOS tube Q1 is turned off. However, since the No. 5 pin of the TP4056 charging protection chip is connected to the No. 1 pin VBAT of the battery socket U23 and the VBAT pin voltage is 0V, the TP4056 charging protection chip does not work; (2) The USB power socket USB1 is not connected to the external USB data cable, and the battery socket U23 is connected to the external polymer lithium battery; at this time, the No. 1 pin VAT voltage of the battery socket U23 is the polymer lithium battery voltage (3.7V~ 4.2V), since the USB power socket USB1 is not connected to an external USB data line, the voltages of pins 2 and 5 of the power socket USB1 are 0V, that is, the voltage of the VIN_5V pin is 0V. In this case, the gate G voltage of the PMOS tube Q1 is 0V, and the drain D voltage is the VBAT pin voltage (3.7V~4.2V). Therefore, the body diode of the PMOS tube is turned on, making the VCC voltage close to the VBAT voltage, and thus making the gate G and source S voltage difference smaller than the PMOS tube Q1 turn-on voltage (-0.7V), so the PMOS tube Q1 continues to be turned on, but due to TP4 The working voltage of pin 4 of the 056 charging protection chip is the VIN_5V pin connected through the resistor R17. Since VIN_5V is 0V at this time, the TP4056 battery protection chip still does not work at this time; (3) The USB power socket USB1 is connected to the external USB data cable, and the battery socket U23 is connected to the external polymer lithium battery; at this time, the voltage of pins 2 and 5 of the power socket USB1 is the USB voltage, that is, the VIN_5V pin is the USB voltage (+5V), and the voltage of pin 1 VAT of the battery socket U23 is the polymer lithium battery voltage (3.7V~4.2V); and the same as situation (1) The same, at this time the VCC pin voltage is the VIN_5V pin voltage minus the voltage drop of the Schottky diode D5. Since the voltage drop of the Schottky diode D5 is very small, VCC+5V, at this time the PMOS tube Q1 is turned off, and the difference from situation (1) is that at this time the working voltage of the TP4056 charging protection chip pin 4 is connected by the VIN_5V pin through the resistor R17, which is +5V, and the TP4056 charging protection chip pin 5 is also connected to the positive electrode of the polymer lithium battery through the No. 1 pin VBAT of the battery socket U23, so the TP4056 charging protection chip starts to work and charges the polymer lithium battery. During the charging process, the No. 6 pin of the TP4056 charging protection chip will output a high level, and the No. 7 pin will output a low level. Since the anode of the red light-emitting diode LED2 is connected through the pull-up resistor R17 (0.4Ω) is connected to VIN_5V, and the cathode is connected to pin 7 of the TP4056 charging protection chip through resistor R18 (1kΩ). Therefore, when charging, the red light-emitting diode LED2 is lit; after charging, pin 6 of the TP4056 charging protection chip will output a low level, and pin 7 will output a high level. Since the anode of the green light-emitting diode LED1 is connected to VIN_5V through a pull-up resistor R17 (0.4Ω), and the cathode is connected to pin 6 of the TP4056 charging protection chip through a resistor R19 (1kΩ), after charging, the green light-emitting diode LED1 is lit; the power input circuit is designed with two power supply modes: polymer lithium battery and USB power supply, and realizes the functions of two power supply switching and battery charging protection. Its output VCC is used as a. Figure 2 Power supply for subsequent circuits;

[0010] like Figure 2 As shown in (b), the +3.3V power supply circuit is composed of an RT9013-33GB voltage regulator chip U8, a resistor and a capacitor; Pin 1 of the RT9013-33GB voltage regulator chip U8 is connected to VCC, and Pin 1 is also connected to AGND through a resistor C65 (1μF), Pin 2 is connected to AGND, Pin 3 is connected to VCC, Pin 4 is left floating, Pin 5 is connected to AGND through a capacitor C66 (1μF) and a resistor RL2 (1kΩ) in parallel, and Pin 5 outputs a +3.3V voltage as the power supply for the detection device LoRa wireless communication module 31, the main control chip 32 and the detection terminal LoRa wireless communication module 41;

[0011] like Figure 2As shown in (c), the +5V and -5V power supply circuits are composed of MT3608L boost chip U22, TPS7A4901 voltage regulator chip U4, TPS7A3001 voltage regulator chip U21, inductors L1, L2, L3, Schottky diodes D1, D3, resistors and capacitors; Pin 1 of the MT3608L boost chip is connected to VCC through inductor L1 (4.7μH), and pin 1 is also connected to coupling capacitors C17 (10μF) and C63 (10μF), capacitor C63 is connected to AGND through inductor L2 (4.7μH), capacitor C63 is also connected to the anode of Schottky diode D1, and the cathode of Schottky diode D1 is connected to pin 3 through resistor R53 (180kΩ), and the cathode of Schottky diode D1 is also connected to the parallel filter capacitor C C15 (100nF) and C16 (22μF) are connected to AGND, and pin 3 is connected to AGND through resistor R54 (20kΩ); capacitor C17 is connected to AGND through Schottky diode D3, and capacitor C17 is connected to AGND through parallel filter capacitors C18 (100nF) and C19 (22μF) after passing through inductor L3 (4.7μH); pin 2 is connected to AGND, pins 4 and 5 are connected to VCC, pin 5 is connected to AGND through parallel filter capacitors C30 (22μF) and C31 (100nF), and pin 6 is connected to AGND, thereby forming a SEPIC+CUK power supply topology, and generating +6V and -6V output voltages at the cathode of Schottky diode D1 and the output end of inductor L3 respectively;

[0012] like Figure 2 As shown in (c), pin 2 of the TPS7A4901 voltage regulator chip is connected to AGND through a resistor R55 (6.2kΩ), and is connected to pin 1 through a parallel resistor R56 (20kΩ) and a capacitor C22 (10nF). Pins 3 and 7 are left floating, pin 4 is connected to AGND, pins 5 and 8 are connected to the +6V voltage output by the MT3608L boost chip, and a filter capacitor C21 (10μF) is connected between pin 8 and AGND; pin 6 of the TPS7A4901 voltage regulator chip is connected to AGND through a capacitor C20 (10nF), pin 9 is connected to AGND, and pin 1 is connected to AGND through a parallel resistor R57 (1kΩ) and a capacitor C23 (10μF), and a +5V voltage is output at pin 1;

[0013] like Figure 2As shown in (c), pin 2 of the TPS7A3001 voltage regulator chip is connected to AGND through resistor R60 (6.2kΩ), and is connected to pin 1 through parallel resistor R59 (20kΩ) and capacitor C26 (10nF). Pins 3 and 7 are left floating, pins 4 and 9 are connected to AGND, pins 5 and 8 are connected to the -6V voltage output by the MT3608L boost chip, and a filter capacitor C25 (10nF) is connected between pin 8 and AGND. 0μF); Pin 6 is connected to AGND through capacitor C24 (10nF), and pin 1 is connected to AGND through resistor R58 (1kΩ) and capacitor C27 (10μF) connected in parallel, and a -5V voltage is output at pin 1; the +5V voltage output from pin 1 of the TPS7A4901 voltage regulator chip and the -5V voltage output from pin 1 of the TPS7A3001 voltage regulator chip are used as bipolar power supplies for operational amplifiers in circuits such as the constant potential instrument circuit 22 and the signal conditioning circuit 23;

[0014] like Figure 2 As shown in (d), the +5V_DVDD and +5V_AVDD power supply circuits are composed of the TPS61071 boost chip U9, the TPS7A2050 voltage regulator chip U2, the inductor L5, the magnetic bead L6, the resistors and the capacitors; the pin 1 of the TPS61071 boost chip is connected to VCC through the inductor L5 (4.7μH), and the filter capacitor C71 (10μF) is connected between VCC and AGND, the pin 2 is connected to AGND, and the pins 3 and 6 are directly connected to VCC; the pin 4 is connected to DGND (digital ground) through the resistor R61 (180kΩ), and is connected to the pin 5 through the resistor R26 (1.8MΩ), and the pin 5 is connected to DGND through the parallel capacitors C72 (4.7μF) and C37 (4.7μF), and the +5.5V voltage is output at the pin 5;

[0015] like Figure 2As shown in (d), pins 1 and 3 of the TPS7A2050 voltage regulator chip are connected to the +5.5V voltage output of pin 5 of the TPS61071 boost chip U9, and a filter capacitor C38 (1μF) is connected between pin 1 and AGND, pins 2 and 4 are connected to DGND, and pin 5 is connected to DGND after passing through a filter capacitor C73 (1μF). Pin 5 outputs +5V_DVDD, and +5V_DVDD outputs +5V_ AVDD, +5V_AVDD and AGND are connected through filter capacitor C74 (1μF), capacitor C73, magnetic bead L6 and capacitor C74 form a πLC filter, and AGND and DGND are connected at a single point through resistor R27 (0Ω), which is beneficial to reduce the crosstalk between digital signals and analog signals and reduce noise. The +5V_DVDD and +5V_AVDD output by the TPS7A2050 voltage regulator chip are used as the power supply for the signal generating circuit 21 and the signal acquisition circuit 24.

[0016] like Figure 3 As shown, the electrochemical signal generating circuit 21 is connected between the main control chip 32 and the constant potential instrument circuit 22, and is composed of a DAC1220E chip and its driving circuit and two OPA2992 differential amplifier circuits. The main control chip 32 can configure the signal generating circuit 21 to output a differential pulse stripping voltammetry signal. Figure 3As shown in (a), the DAC1220E chip and its driving circuit are composed of a 2.4576MHz active crystal oscillator U10, a DAC1220E chip U11, a 2.5V voltage reference source ADR421 chip U12, a 100Ω resistor RN1, resistors and capacitors; the 1st, 3rd, 5th, 7th and 8th pins of the 2.5V voltage reference source ADR421 chip are left floating, the 2nd pin is connected to +5V_AVDD, the 4th pin is connected to AGND, and a filter capacitor C29 (100nF) is connected between the 2nd pin and AGND. Pin No. 1 is connected to AGND through capacitor C42 (100nF) and outputs a fixed 2.5V voltage reference source signal VREF_2.5V; Pin No. 1 of the 2.4576MHz active crystal oscillator U10 is left floating, Pin No. 2 is connected to DGND, Pin No. 3 is connected to Pin No. 3 of the DAC1220E chip U11, and Pin No. 4 is connected to +5_DVDD; Pin No. 1 of the DAC1220E chip U11 is connected to +5_DVDD and connected to DGND through capacitor C28 (4.7μF), Pin No. 2, 6, 7 and 8 are connected to +5_DVDD and +5_DVDD respectively. The pins are left floating, pin 3 is connected to pin 3 of the 2.4576MHz active crystal oscillator U10, pin 4 is connected to DGND, pin 5 is connected to +5V_AVDD and AGND through capacitor C43 (4.7μF), pin 9 is connected to VREF_2.5V output by the 2.5V voltage reference source ADR421 through capacitor C40 (10nF), pin 10 is connected to pin 11 through capacitor C39 (3.3nF), and pin 11 outputs an adjustable voltage VOUT_DAC1220 of 0 to 5V, 1 Pin 2 is connected to VREF_2.5V output by 2.5V voltage reference source ADR421, filter capacitor C41 (100nF) is connected between pin 12 and AGND, pin 13 is connected to AGND, pins 14, 15, and 16 are respectively connected to SPI pins PC9, PC10, and PC11 of the main control chip 32 through a 100Ω resistor RN1. The main control chip 32 can configure pin 11 of the DAC1220E chip to output an adjustable voltage value VOUT_DAC1220 in the range of 0 to 5V through the SPI pin;

[0017] like Figure 3As shown in (b), the differential amplifier circuit is composed of two OPA2992 operational amplifiers, a 1kΩ precision resistor and a 100nF capacitor, wherein the in-phase input terminal of the first operational amplifier OPA2992, i.e., pin 3 of the OPA2992 chip U14.1, is connected to AGND through a resistor R35 (1kΩ), and is also connected to the 0-5V adjustable voltage VOUT_DAC1220 output by pin 11 of the DAC1220E chip through a resistor R33 (1kΩ), and the inverting input terminal, i.e., pin 2, is connected to VREF_2.5V output by a 2.5V voltage reference source ADR421 through a resistor R31 (1kΩ), and pin 2 is also connected to the 0-5V adjustable voltage VOUT_DAC1220 output by a resistor R29 (1kΩ). ) is connected to pin 1; pin 4 of the OPA2992 chip U14.1 is connected to the -5V voltage output by pin 1 of the TPS7A3001 voltage regulator chip, and is connected to AGND through capacitor C47 (100nF). Pin 8 of the OPA2992 chip U14.1 is connected to the +5V voltage output by pin 1 of the TPS7A4901 voltage regulator chip, and is connected to AGND through capacitor C45 (100nF). Pin 1 outputs the VOUT1 voltage. The first operational amplifier OPA2992 chip U14.1, resistors R29, R31, R33, and R35 form a subtraction circuit, and its output voltage VOUT1 is equal to VOUT_DAC12 20V minus VREF_2.5V; the in-phase input of the second operational amplifier OPA2992, that is, pin 5 of the OPA2992 chip U14.2, is connected to the output VOUT1 of the first operational amplifier, and the inverting input, that is, pin 6 of the OPA2992 chip U14.2, is connected to AGND through a resistor R32 (1kΩ). A resistor R30 (1kΩ) and a capacitor C44 (100nF, used for filtering and phase compensation) are connected in parallel between pins 6 and 7. The output end, that is, pin 7 of the OPA2992 chip U14.2, outputs a VOUT_DAC voltage signal through a resistor R34 (1kΩ). ND is connected to capacitor C46 (100nF), resistor R34 (1kΩ) and capacitor C46 (100nF) form an RC low-pass filter to filter out high-frequency noise interference; the second operational amplifier OPA2992 chip U14.2, resistors R30, R32 and capacitor C44 form a common-mode proportional amplifier circuit, so the output VOUT_DAC voltage is equal to twice the VOUT1 voltage (i.e., VOUT_DAC1220 voltage minus VREF_2.5V voltage). Since the VOUT_DAC1220 voltage can be directly configured by the main control chip 32 through the SPI pin (adjustable voltage value in the range of 0 to 5V), and the VREF_2.5V voltage is a fixed value of 2.5V, so the VOUT_DAC1220 voltage can also be indirectly configured through the SPI of the main control chip 32, and the output voltage signal is an adjustable voltage value in the range of -5V to +5V, thereby realizing the main control chip 32 configuring the signal generating circuit 21 to output the differential pulse stripping voltammetry signal (the main parameters of the differential pulse stripping voltammetry method are: initial potential, termination potential, potential increment, amplitude, pulse width, sampling interval, pulse period, rest time, etc.). .

[0018] like Figure 4As shown, the constant potential meter circuit 22 is connected between the heavy metal detection front end 1 and the signal generating circuit 21; the differential pulse voltammetry signal is transmitted from the signal generating circuit 21 to the constant potential meter circuit 22, and the output of the constant potential meter circuit 22 is connected to the reference electrode and the auxiliary electrode of the heavy metal detection front end 1; the constant potential meter circuit 22 is composed of 3 operational amplifiers, a buffer BUF634, a resistor and a capacitor, the first operational amplifier, i.e., the No. 4 pin of the OPA4192 chip U1.1 is connected to the No. 1 pin of the TPS7A4901 voltage regulator chip in the above-mentioned power supply circuit 36 ​​to output a +5V voltage, and at the same time is connected to AGND through the filter capacitor C4 (100nF), and the No. 11 pin is connected to the No. 1 pin of the TPS7A3001 voltage regulator chip output -5V voltage, and at the same time connected to AGND through filter capacitor C8 (100nF), the in-phase input end, that is, pin 3 of the OPA4192 chip U1.1, is connected to the VOUT_DAC output end of the signal generating circuit 21, and the output end, that is, pin 1 of the OPA4192 chip U1.1, is directly connected to the inverting input end of the operational amplifier, that is, pin 2 of the OPA4192 chip U1.1, thereby forming a voltage follower, and using the characteristics of the voltage follower with infinite input impedance and very small output impedance for impedance matching, so that the output of pin 1 of the OPA4192 chip U1.1 is equivalent to the VOUT_DAC signal; pin 1 of the OPA4192 chip U1.1 is connected to the first pin through resistor R4 (10kΩ). The inverting input terminal of the second operational amplifier is pin 6 of the OPA4192 (U1.2) chip. The second operational amplifier is also connected to the +5V and -5V voltages output by the power supply circuit 36 ​​(connected to AGND through 100nF capacitors C106 and C107 respectively). The non-inverting input terminal, pin 5 of the OPA4192 chip U1.2, is connected to AGND. The output terminal, pin 7 of the OPA4192 chip U1.2, is connected to pin 3 of the buffer BUF634. Pin 4 of the buffer BUF634 is connected to the -5V voltage and is connected to AGND through the filter capacitor C6 (100nF). Pin 7 is connected to the +5V voltage and is connected to AGND through the filter capacitor C1 (100nF). , the output end of the buffer BUF634, i.e., pin 6, is connected to the auxiliary electrode CE of the front end of the heavy metal detection; the third operational amplifier is also connected to the +5V and -5V voltages output by the power supply circuit 36 ​​(connected to AGND through 100nF capacitors C108 and C109 respectively), the output end, i.e., pin 8 of the OPA4192 chip U1.3, is connected to the inverting input end of the operational amplifier, i.e., pin 9 of the OPA4192 chip U1.3 to form a voltage follower, and a resistor R6 (10kΩ) is connected between pin 8 and pin 6 of the second operational amplifier OPA4192 chip U1.2, and the same-direction input end, i.e., pin 10 of the OPA4192 chip U1.3, is connected to the reference electrode RE of the front end of the heavy metal detection.

[0019] like Figure 5As shown, the signal conditioning circuit 23 is connected between the heavy metal detection front end 1 and the signal acquisition circuit 24; the signal conditioning circuit 23 includes a current / voltage conversion circuit (I / V conversion circuit) composed of an OPA4192 operational amplifier U1.4 and an ADG1604 multiplexer U5 and a fourth-order Butterworth low-pass filter composed of OPA2192 operational amplifiers U6.1, U6.2, resistors and capacitors, and the operational amplifier is connected to the +5V and -5V voltages output by the power supply circuit 36 ​​(connected to AGND through 100nF capacitors C110 and C111 respectively); the in-phase input terminal of the first operational amplifier, i.e., pin 12 of the OPA4192 chip U1.4, is connected to AGND, and the inverting The input end, i.e., pin 13 of the OPA4192 chip U1.4, is connected to the working electrode WE of the heavy metal detection front end; at the same time, pin 13 is connected to pin 1 of the ADG1604 multiplexer U5 through a parallel resistor R1 (100kΩ) and a capacitor C2 (47pF), connected to pin 2 of the ADG1604 multiplexer U5 through a parallel resistor R2 (10kΩ) and a capacitor C3 (470pF), connected to pin 3 of the ADG1604 multiplexer U5 through a parallel resistor R3 (1kΩ) and a capacitor C5 (4.7nF), and connected to pin 4 of the ADG1604 multiplexer U5 through a parallel resistor R5 (100Ω) and a capacitor C7 (47nF). Pin 4, where the main functions of capacitors C2, C3, C5, and C7 are filtering and phase compensation; the output end of the operational amplifier, namely pin 14 of the OPA4192 chip (U1.4), is connected to pin 5 of the ADG1604 multiplexer to form an I / V conversion circuit, which is used to convert the response current signal related to the heavy metal concentration generated by the working electrode WE at the front end of the heavy metal detection into an analog voltage signal and output it from pin 14 as V_POTENTIAL; the conduction relationship of the ADG1604 multiplexer can be changed through the main control chip 32, thereby changing the resistance value of the access resistor to 100, 1k, 10k or 100k, that is, the signal after I / V conversion is the original 100, 1 k, 10k or 100k times; specifically, when channel 1 is turned on (the other channels are turned off), the response current signal generated by the working electrode WE is amplified 100k times by I / V conversion through resistor R1 (100kΩ) and capacitor C2 (47pF) and then outputs the signal V_POTENTIAL; when channel 2 is turned on (the other channels are turned off), the response current signal generated by the working electrode WE is amplified 10k times by I / V conversion through resistor R2 (10kΩ) and capacitor C3 (470pF) and then outputs the signal V_POTENTIAL; when channel 3 is turned on (the other channels are turned off), the response current signal generated by the working electrode WE is amplified 10k times by I / V conversion through resistor R3 (1kΩ) and capacitor C5 (4.7nF) is amplified 1k times by I / V conversion and then outputs signal V_POTENTIAL; when channel 4 is turned on (other channels are closed), the response current signal generated by the working electrode WE is amplified 100 times by I / V conversion through resistor R5 (100Ω) and capacitor C7 (47nF) and then outputs signal V_POTENTIAL; V_POTENTIAL is then connected to the in-phase input terminal of the second operational amplifier, that is, pin 3 of the OPA2192 chip U6.1, through resistors R7 (14.7kΩ) and R8 (14.7kΩ). .7kΩ) and R8 (14.7kΩ) are connected to the pin 1 of the OPA2192 chip U6.1 through the capacitor C13 (120nF). The pin 3 of the OPA2192 chip U6.1 is connected to AGND through the capacitor C10 (100nF). The pin 4 of the OPA2192 chip U6.1 is connected to the -5V voltage and connected to AGND through the filter capacitor C11 (100nF). The pin 8 is connected to the +5V voltage and connected to AGND through the filter capacitor C9 (100nF). The output of the operational amplifier The first pin of the OPA2192 chip U6.1 is connected to the inverting input of the operational amplifier, that is, the second pin of the OPA2192 chip U6.1. The first pin is also connected to the non-inverting input of the third operational amplifier, that is, the fifth pin of the OPA2192 chip U6.2, through resistors R9 (6.1kΩ) and R10 (6.1kΩ). The fifth pin of the OPA2192 chip U6.2 is also connected to AGND through capacitor C12 (100nF). The connection end of resistors R9 (6.1kΩ) and R10 (6.1kΩ) is connected to AGND through capacitor C 14 (680nF) and then connected to the No. 7 pin of the OPA2192 chip U6.2; the output end of the third operational amplifier OPA2192, namely the No. 7 pin of the OPA2192 chip U6.2, is connected to the inverting input end of the operational amplifier, namely the No. 6 pin of the OPA2192 chip U6.2, thereby forming a fourth-order Butterworth low-pass filter to filter out interference and noise in the V_POTENTIAL signal, and the No. 7 pin of the OPA2192 chip U6.2 outputs an analog voltage signal V_FILTER, which is collected by the signal acquisition circuit 24. .

[0020] like Figure 6As shown, the signal acquisition circuit 24 is connected between the signal conditioning circuit 23 and the main control chip 32. The signal acquisition circuit 24 is composed of an ADS8691 chip U13, a 4.096V voltage reference source REF5040 chip U16, a 51Ω resistor RN2, resistors and capacitors; pins 1, 3, 7 and 8 of the 4.096V voltage reference source REF5040 chip U16 are suspended, pin 2 is connected to +5V_AVDD, and pin 2 is connected to AGND through capacitors C55 (10μF) and C56 (100nF), pin 4 is connected to AGND, pin 5 is connected to AGND through capacitor C57 (1μF), and pin 6 is connected to AGND through resistor R42 ( 0.22Ω) and capacitor C58 (10μF) are connected to AGND, and pin 6 is connected to AGND through resistor R43 (0.47Ω) and capacitor C59 (10μF). Pin 6 outputs a fixed 4.096V voltage reference source signal VREF_4.096V; pin 1 of the ADS8691 chip U13 is connected to DGND, pin 2 is connected to +5V_AVDD, pin 2 is connected to AGND through parallel filter capacitors C49 (1μF) and C51 (100nF), pins 3 and 5 are connected to AGND, pin 4 is connected to the voltage reference source signal VREF_4.096V, and pin 6 is connected to DGND through resistor R39 (0.22Ω) and then connected to AGND through parallel filter capacitors C52 (1μF), C53 (10μF), and C54 (1μF). Pin 9 is connected to the PB13 pin of the main control chip 32 through the resistor RN2. Pin 9 is also connected to +5V_DVDD through the pull-up resistor R40 (10kΩ). Pins 10, 11, 12, and 13 of the ADS8691 chip U13 are SPI signal pins. Pins 10, 11, and 12 are connected to The PB15, PB11 and PB10 pins of the main control chip 32 are connected, the 13 pin is connected to +5V_DVDD through resistors R38 (51Ω) and R36 (10kΩ), the connection end of resistors R38 (51Ω) and R36 (10kΩ) is connected to the PB8 pin of the main control chip 32, the 14 pin is connected to +5V_DVDD through resistors R37 (51Ω) and R12 (10kΩ), the resistors R37 (51Ω) and R12 (10kΩ) are connected to the +5V_DVDD. ) outputs the SDO-1 signal from the connection end, the 15th pin of the ADS8691 chip U13 outputs the RVS signal, the 16th pin of the ADS8691 chip U13 is connected to +5V_DVDD, and the 16th pin is connected to AGND through the parallel filter capacitors C48 (1μF) and C50 (100nF); the 7th and 8th pins of the ADS8691 chip U13 are signal acquisition inputs, the 7th pin is connected to the analog voltage signal V_FILTER at the output end of the signal conditioning circuit 23, and the 8th pin is connected to AGND, so that the ADS8691 chip U13 can collect the analog signal through the 7th pin and convert it into a digital signal, and then transmit the collected data to the main control chip 32 through the 10th, 11th, 12th, and 13th pins of the ADS8691 chip U13, i.e., the SPI signal pins, and the main control chip 32 can control the acquisition voltage range and filtering functions of the signal acquisition circuit 24 to improve the accuracy of the acquisition, thereby improving the accuracy of the heavy metal concentration detection in water. .

[0021] The detection device LoRa wireless communication module 31 and the detection terminal LoRa wireless communication module 41 use LLCC68 scheme, working frequency band 410~493MHz (433MHz is selected in the embodiment), baud rate 115200bps, no check bit is used, air rate 19.2Kbps, transmission power 20dBm, and transparent transmission transmission mode is used. Through this technical solution, the detection device LoRa wireless communication module 31 can send the collected data to the detection terminal LoRa wireless communication module 41, and receive the detection instruction sent by the detection terminal LoRa wireless communication module 41. The parameters configured by the instruction are set by the test parameter configuration 44 function block. The wireless transmission distance can reach 3500m, and the data interaction between the microcontroller minimum system 3 and the heavy metal wireless detection terminal 4 can be realized.

[0022] like Figure 7As shown, the main control chip 32, the CLK clock circuit 33, the SWD burning circuit 34, and the RST reset circuit 35 are specifically introduced; in terms of the selection of the microcontroller of the main control chip 32, this embodiment adopts the STM324L431 series chip (model: STM32L431RCT6) produced by ST, which belongs to the STM32 ultra-low power series, which is based on the ARM Cortex-M4 core design, supports DSP and FPU floating-point operation units, and the clock frequency can reach up to 80MHz, with the advantages of high performance and low power consumption; the main control chip 32 is connected to the SPI signal pins of the DAC1220E chip in the signal generating circuit 21 through the PC9, PC10 and PC11 pins, that is, the 14, 15, and 16 pins of the DAC1220E chip, and the main control chip 32 is connected to the SPI signal pins of the ADS8691 chip in the signal acquisition circuit 24 through the PB15, PB11, PB10, and PB8 pins, that is, the 10, Pins 11, 12, and 13 are connected to realize the driving and control tasks of the signal generating circuit 21, the signal acquisition circuit 24, and the detection device LoRa wireless module 31, and the signal generating circuit 21 is configured to output a differential pulse stripping voltammetry signal (the main parameters of the differential pulse stripping voltammetry are: initial potential, termination potential, potential increment, amplitude, pulse width, sampling interval, pulse period, standing time, etc.), and the voltage signal data collected by the signal acquisition circuit 24 is sent to the detection terminal LoRa wireless communication module 41 of the heavy metal wireless detection terminal 4 through the detection device LoRa wireless communication module 31.The CLK clock circuit 33 is mainly composed of an 8MHz crystal oscillator X3, a 32.768KHz crystal oscillator X4 and a capacitor. Pin 1 of the 8MHz crystal oscillator X3 is connected to DGND through a capacitor C92 (22pF), and pin 1 is connected to the XIN pin (i.e., PH0) of the main control chip 32. Pins 2 and 4 are directly connected to DGND, and pin 3 is connected to DGND through a capacitor C91 (22pF), and pin 3 is connected to the XOUT pin (i.e., PH1) of the main control chip 32. The 8MHz crystal oscillator X3 serves as a high-speed external clock source to provide an 8MHz clock signal to the main control chip 32. Pin 1 of the 32.768KHz crystal oscillator X4 is connected to DGND through a capacitor C104 (22pF), and pin 1 is connected to the XOUT pin (i.e., PH1) of the main control chip 32. TXIN pin (i.e. PC14), pin 2 is connected to DGND through capacitor C103 (22pF), and pin 2 is connected to TXOUT pin (i.e. PC15) of main control chip 32. 32.768KHz crystal oscillator X4 is used as a low-speed external clock source to provide 32.768KHz clock signal to main control chip 32; the SWD burning circuit 34 is composed of socket H20, pin 1 of socket H20 is connected to +3.3V, pin 2 is connected to SWDIO pin (i.e. PA13) of main control chip 32, pin 3 is connected to SWCLK pin (i.e. PA14) of main control chip 32, and pin 4 is connected to DGND. The computer side can use STLINK and other devices to burn program or debug the main control chip 32 through SWD burning circuit 34. The RST reset circuit 35 is mainly composed of a button SW2, a resistor R74 (10kΩ) and a capacitor C102 (100nF). Pins 1 and 2 of the button SW2 are connected to DGND, pins 3 and 4 are connected to the NRST pin of the main control chip 32, pins 3 and 4 are connected to +3.3V through resistor R74 (10kΩ) at the same time, and pins 3 and 4 are connected to DGND through capacitor C102 (100nF) at the same time. When it is necessary to reset the rapid detection device for heavy metals in water of the present invention, pressing the button SW2 can restore the detection device to its initial state.

[0023] like Figure 8As shown, the heavy metal wireless detection terminal 4 is composed of a detection terminal LoRa wireless communication module 41, a heavy metal detection host computer program 42, a communication configuration 43, a test parameter configuration 44, a data processing 45, and a data storage 46; the heavy metal wireless detection terminal 4 exchanges data with the detection device LoRa wireless communication module 31 in the microcontroller minimum system 3 through the detection terminal LoRa wireless communication module 41, and can realize communication with multiple heavy metal detection terminals 4 in the heavy metal detection host computer program 42. The communication configuration 43 can configure the baud rate, working mode, transmission mode, air rate, communication address, communication channel and transmission power of LoRa data transmission, connect the heavy metal wireless rapid detection devices at different locations, and realize continuous detection of heavy metals in multiple places in water. The test parameter configuration 44 can configure the voltage signal generated by the signal generating circuit 21 for differential pulse stripping voltammetry, and its main parameters are: initial potential, termination potential, potential increment, amplitude, pulse width, sampling interval, pulse period, static time, etc. The data processing 45 can restore the received data to the response current, and then smooth and filter the data through the Savitzky-Golay algorithm. After the detection is completed, the peak value of the heavy metal response current is calculated using the peak-seeking algorithm based on local maximum screening, and the volt-ampere curve before and after smooth filtering is drawn (where the horizontal axis is voltage and the vertical axis is response current), and the heavy metal concentration in the water is calculated according to the electrode response current and the heavy metal concentration linear equation, and the concentration value is displayed in the heavy metal detection host computer program 42. The data storage 46 can save various types of data, images, etc. involved in the data processing 45 for data storage and backup.

[0024] By adopting the above technical solution, after the detection starts, the detection device LoRa wireless communication module 31 receives the detection instruction sent by the detection terminal LoRa wireless communication module 41 and sends the instruction to the main control chip 32. The main control chip 32 will control the DAC1220E chip in the signal generating circuit 21 through the SPI bus to output the corresponding voltage VOUT_DAC according to the differential pulse stripping voltammetry signal parameters set by the test parameter configuration 44, generate a differential pulse voltammetry signal, and transmit it to the constant potential instrument circuit 22. At the same time, the response current signal related to the heavy metal concentration generated by the working electrode WE in the heavy metal detection front end 1 is converted by I / V and filtered by a fourth-order low-pass filter through the signal conditioning circuit 23 to output an analog voltage signal V_FILTER, and then The analog voltage signal is converted into a digital signal through the signal acquisition circuit 24 and transmitted to the main control chip 32. The main control chip 32 transmits the data remotely and in real time to the detection terminal LoRa wireless communication module 41 through the detection device LoRa wireless communication module 31; the obtained data is first restored to the response current through the data processing 45 function, and then smoothed and filtered by the Savitzky-Golay algorithm, and the peak value of the response current is obtained by using the peak-finding algorithm based on local maximum screening. Finally, the volt-ampere curve before smoothing and filtering and the volt-ampere curve after smoothing and filtering are plotted (where the horizontal axis is voltage and the vertical axis is response current), and the heavy metal concentration in water is calculated according to the electrode response current and the heavy metal concentration linear equation, and the concentration value is displayed in the heavy metal detection host computer program 42.

[0025] In summary, the beneficial effects of the present invention are:

[0026] 1. The detection device can realize remote wireless rapid detection of heavy metal concentrations in water bodies. The maximum wireless communication distance is 3500m, and the heavy metal concentrations in multiple water bodies can be continuously detected.

[0027] 2. A variety of heavy metal sensitive electrodes can be used as working electrodes for detection, and the parameters of differential pulse stripping voltammetry signals can be configured;

[0028] 3. When using the differential pulse stripping voltammetry in the electrochemical method, due to the multivalent characteristics of the nano-modified electrode itself, it can have a high response current without pre-enrichment operation, with high detection accuracy and small relative error. The single detection time is within 3 minutes, which greatly reduces the detection time and power consumption, improves the detection speed, and is equipped with a host computer program to simplify the detection process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the overall structure of a wireless rapid detection device for heavy metals in water according to the present invention; Figure 1The sub-parts include: heavy metal detection front end 1, electrochemical detection circuit 2, microcontroller minimum system 3, heavy metal wireless detection terminal 4; signal generation circuit 21, constant potentiostat circuit 22, signal conditioning circuit 23, signal acquisition module 24; detection device LoRa wireless communication module 31, main control chip 32, CLK clock circuit 33, SWD burning circuit 34, RST system reset circuit 35, power supply circuit 36; detection terminal LoRa wireless communication module 41, heavy metal detection host computer program 42, communication configuration 43, test parameter configuration 44, data processing 45, data storage 46;

[0030] Figure 2 Schematic diagram of the power supply circuit 36 ​​of the present invention; Figure 2 (a) is the schematic diagram of the power input circuit (VCC). Figure 2 (b) is a schematic diagram of the +3.3V power supply circuit (VCC to +3.3V). Figure 2 (c) is a schematic diagram of the +5V and -5V power supply circuit (VCC to ±6V and ±5V); Figure 2 (d) is a schematic diagram of the +5V_AVDD and +5V_DVDD power supply circuit (VCC to +5V_AVDD and +5V_DVDD);

[0031] Figure 3 FIG. 2 is a schematic diagram of the scanning signal generating circuit 21 of the present invention; Figure 3 (a) is the DAC1220E chip and its driving circuit. Figure 3 (b) is the OPA2992 differential amplifier circuit;

[0032] Figure 4 It is a schematic diagram of the constant potential instrument circuit 22 of the present invention;

[0033] Figure 5 It is a schematic diagram of the signal conditioning circuit 23 of the present invention;

[0034] Figure 6 It is a schematic diagram of the signal acquisition circuit 24 of the present invention;

[0035] Figure 7 It is a schematic diagram of the main control chip 32, the CLK clock circuit 33, the SWD programming circuit 34 and the RST reset circuit 35 in the minimum system of the microcontroller of the present invention;

[0036] Figure 8 This is a user interface diagram of the heavy metal detection host computer program 42 of the present invention;

[0037] Fig. 9 In Example 1 of the present invention, nitrogen-doped tungsten oxide electrodes were used to generate Pb at different standard concentrations. 2+The differential pulse voltammetry test curve in acetate buffer solution (the specific values ​​of the concentration coordinates are 2μM, 3μM, 4μM, 5μM, 6μM, 7μM, 8μM, 9μM, and 10μM respectively);

[0038] Fig.10 The differential pulse voltammetry test curve of the nitrogen-doped tungsten oxide electrode in Example 1 of the present invention shows that the peak current of the stripping of Pb 2+ Standard curve of linear relationship of concentration change;

[0039] Fig.11 In Example 1 of the present invention, the nitrogen-doped tungsten oxide electrode was used to detect the Pb content in 2 μM water. 2+ Detection diagram of ions;

[0040] Fig.12 In Example 1 of the present invention, the nitrogen-doped tungsten oxide electrode was used to react 5 μM Pb in water. 2+ Detection diagram of ions;

[0041] Fig.13 In Example 2 of the present invention, a tungsten oxide electrode was used to measure the Pb content in 2 μM water. 2+ Detection diagram of ions;

[0042] Fig.14 In Example 2 of the present invention, a tungsten oxide electrode was used to measure the Pb content in 5 μM water. 2+ Detection diagram of ions;

[0043] Fig.15 In Example 3 of the present invention, a phosphorus-doped tungsten oxide electrode was used to detect Pb in 2 μM water. 2+ Detection diagram of ions;

[0044] Fig.16 In Example 3 of the present invention, a phosphorus-doped tungsten oxide electrode was used to detect Pb in 5 μM water. 2+ Detection diagram of ions. DETAILED DESCRIPTION

[0045] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, and the present invention will be further described in detail.

[0046] Example 1

[0047] In this embodiment, the detection steps are described by taking nitrogen-doped tungsten oxide nano-modified electrode as the working electrode to detect heavy metals in water at multiple concentrations.

[0048] The preparation steps of the nitrogen-doped tungsten oxide nano-modified electrode are as follows:

[0049] (1) The tungsten foil was appropriately cut to a size of 1.0 cm × 1.0 cm, and ultrasonically cleaned with toluene, acetone, and ethanol, respectively, and finally ultrasonically cleaned with deionized water. Each ultrasonic cleaning time was 10 minutes;

[0050] (2) preparing 50 mL of 0.05 M oxalic acid solution as the sedimentation solution;

[0051] (3) Using a two-electrode system, the tungsten foil processed in step (1) is used as the working electrode, and the platinum sheet (1.5 cm × 1.5 cm) is used as the counter electrode; the deposition is carried out by constant potential deposition method, the deposition voltage is 20 V, and the deposition time is 2 hours; the electrode after deposition is placed on a porcelain boat, placed in a tube furnace, and annealed at 500°C for 2 hours with nitrogen, and the heating rate is 5°C / min. After annealing, a nitrogen-doped tungsten oxide nano-modified electrode is obtained;

[0052] (4) The obtained nitrogen-doped tungsten oxide nano-modified electrode was used for electrochemical heavy metal ion detection using the wireless heavy metal rapid detection device in water of the present invention. A three-electrode system was used, i.e., the nitrogen-doped tungsten oxide nano-modified electrode was used as the working electrode, a platinum sheet (1.0 cm × 1.0 cm) was used as the counter electrode, and a saturated calomel electrode (SCE) was used as the reference electrode. 2+ A 0.1 M acetate buffer solution with a pH value of 5.0 was used as the electrolyte (soluble heavy metal salt lead nitrate was dissolved in the acetate buffer solution), and differential pulse voltammetry stripping was used for detection.

[0053] In the communication configuration 43, the microcontroller minimum system 3 and the electrochemical detection circuit 2 are connected; in the detection parameters 44, the test parameters for the nitrogen-doped tungsten oxide nano-modified electrode differential pulse stripping voltammetry for detecting heavy metals in water are set as follows: initial potential -1.0V, termination potential -0.45V, potential increment 0.005V, amplitude 0.025V, pulse width 0.15s, sampling interval 0.05s, pulse period 0.50s, and standing time 0.0s.

[0054] Then the detection is started. In each detection process, the detection data will be remotely sent to the detection terminal LoRa wireless communication module 41 through the detection device LoRa wireless communication module 31 in the microcontroller minimum system 3. After each detection, the acquired analog voltage signal data is first restored to the response current through the data processing 45 function, and then smoothed and filtered by the Savitzky-Golay algorithm, and the peak-finding algorithm based on local maximum screening is used to obtain the response current peak (i.e., dissolution peak current). Finally, the volt-ampere curve before smoothing and filtering and the volt-ampere curve image after smoothing and filtering are drawn (the horizontal axis is voltage, the vertical axis is response current, and the triangle mark is the response current peak), and the heavy metal concentration in the current sample is calculated and displayed according to the linear equation of electrode response current and heavy metal concentration.

[0055] The heavy metal rapid detection device was used to prepare nitrogen-doped tungsten oxide nano-modified electrode under different standard concentrations of Pb 2+ The differential pulse voltammetry test curve in acetate buffer solution (the specific values ​​of the concentration coordinates are 2μM, 3μM, 4μM, 5μM, 6μM, 7μM, 8μM, 9μM, and 10μM respectively) is as follows Fig. 9 As shown in the figure, the peak current of the test curve response (dissolution peak current) increases with the change of Pb 2+ The linear relationship standard curve of concentration change is as follows Fig.10 shown.

[0056] Using this linear relationship, the test results and relative errors of the heavy metal rapid detection device are calculated as shown in Table 1. 2+ The test results are taken as an example. The volt-ampere curves drawn by the heavy metal detection host computer program in the heavy metal wireless detection terminal are as follows: Fig.11 (2 μM Pb 2+ )and Fig.12 (5 μM Pb 2+ ), where Fig.11 and Fig.12 The left image is the voltammetric curve before smoothing by the Savitzky-Golay algorithm, and the right image is the voltammetric curve after smoothing by the Savitzky-Golay algorithm. The horizontal axis is voltage, the vertical axis is response current, and the triangle mark is the response current peak value (dissolution peak current). The peak currents of the voltammetric curve calculated by the peak algorithm are 194.4 and 260.2 μA cm -2 .

[0057] The above detection data show that the heavy metal rapid detection device used in this embodiment has high detection accuracy and small relative error when detecting heavy metals in water using the prepared nitrogen-doped tungsten oxide nano-modified electrode, and the heavy metal detection host computer used in this embodiment can efficiently process and display data, is easy to operate, and simplifies the detection process.

[0058] Table 1: Effect of nitrogen-doped tungsten oxide electrode on Pb in water with different concentrations in Example 1 2+ Ion detection data

[0059]

[0060]

[0061] Example 2

[0062] Using a tungsten oxide nano-modified electrode as a working electrode, the same detection device and detection method as in Example 1 were used to detect heavy metals in water at two concentrations;

[0063] The preparation steps of the tungsten oxide nano-modified electrode are as follows:

[0064] (1) The tungsten foil was appropriately cut to a size of 1.0 cm × 1.0 cm, and ultrasonically cleaned with toluene, acetone, and ethanol, respectively, and finally ultrasonically cleaned with deionized water. Each ultrasonic cleaning time was 10 minutes;

[0065] (2) preparing 50 mL of 0.05 M oxalic acid solution as the sedimentation solution;

[0066] (3) Using a two-electrode system, the tungsten foil processed in step (1) is used as the working electrode, and the platinum sheet (1.5 cm×1.5 cm) is used as the counter electrode; the deposition is carried out by constant potential deposition method, the deposition voltage is 20 V, and the deposition time is 2 hours; the electrode after deposition is placed on a porcelain boat, placed in a tube furnace, annealed at 500°C for 2 hours with argon gas, and the heating rate is 5°C / min. After annealing, a tungsten oxide nano-modified electrode is obtained;

[0067] As in Example 1, the test parameters for detecting heavy metals in water by differential pulse stripping voltammetry using tungsten oxide nano-modified electrodes were set in the detection parameters 44 as follows: initial potential -1.0 V, termination potential -0.45 V, potential increment 0.005 V, amplitude 0.025 V, pulse width 0.15 s, sampling interval 0.05 s, pulse period 0.50 s, and rest time 0.0 s. 2+ A 0.1 M acetate buffer solution with a pH value of 5.0 was used as the electrolyte (soluble heavy metal salt lead nitrate was dissolved in the acetate buffer solution), and differential pulse voltammetry stripping was used for detection.

[0068] The test results show that the tungsten oxide nano-modified electrode prepared in this example has a good 2+ The smoothed and filtered voltammetric curves are as follows: Fig.13 and Fig.14 As shown in the figure, the horizontal axis is voltage, the vertical axis is response current, and the triangle mark is the response current peak value (dissolution peak current). The calculated dissolution peak currents are 179.7 and 243.6 μA cm -2 .

[0069] Example 3

[0070] A phosphorus-doped tungsten oxide / carbon cloth (P-WOx / CC) nano-modified electrode was used as a working electrode, and the same detection device and detection method as in Example 1 were used to detect heavy metals in water with different concentration gradients;

[0071] The preparation steps of the phosphorus-doped tungsten oxide / carbon cloth (P-WOx / CC) nano-modified electrode are as follows:

[0072] (1) The carbon cloth was appropriately cut to a size of 1.0 cm × 1.0 cm, and ultrasonically cleaned twice in methyl sulfoxide, acetone, ethanol, and deionized water in sequence, and then ultrasonically cleaned twice in a 0.1 M hydrogen chloride (HCl) solution, and finally ultrasonically cleaned repeatedly in deionized water until the pH value was neutral. Each ultrasonic cleaning time was 10 minutes, and the cleaned carbon cloth was stored in deionized water for later use;

[0073] (2) Prepare 50 mL of sedimentation solution, in which the concentration of sodium tungstate is 0.005 M and the concentration of sulfuric acid is 0.5 M;

[0074] (3) A three-electrode system was used, with the carbon cloth treated in step (1) as the working electrode, a 1.5×1.5 cm platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode; cyclic voltammetry (CV) was used for electrochemical deposition, with a potential window of -0.3 V to 0.7 V, a scan rate of 50 mV / s, and 30 scans; the electrode after deposition was rinsed with deionized water and dried at 60°C, then the electrode was placed on a porcelain boat, and an aluminum boat containing 0.4 g of sodium dihydrogen phosphate was placed at a distance of 5 cm, and placed together in a tube furnace. In an argon atmosphere, the temperature was increased to 280°C at a rate of 2°C / min and kept constant for 1 hour. After cooling to room temperature, the electrode was taken out, washed with deionized water to remove residual phosphorus catalyst, and finally dried to obtain a phosphorus-doped tungsten oxide / carbon cloth (P-WOx / CC) nano-modified electrode.

[0075] What is different from Example 1 during detection is that before the detection starts, Example 3 needs to set the test parameters for differential pulse stripping voltammetry detection of heavy metals in water in the detection parameters 44 as follows: initial potential -1.0V, termination potential -0.2V, potential increment 0.005V, amplitude 0.025V, pulse width 0.05s, sampling interval 0.02s, pulse period 0.25s, and standing time 0.0s.

[0076] The test results show that the phosphorus-doped tungsten oxide / carbon cloth (P-WOx / CC) nano-modified electrode prepared in this example has a strong 2+ The smoothed and filtered voltammetric curves are as follows: Fig.15 and Fig.16 As shown, the horizontal axis is voltage, the vertical axis is response current, and the triangle mark is the response current peak value (dissolution peak current). The calculated dissolution peak currents are 196.6 and 290.9 μA cm -2 .

[0077] In summary, the wireless rapid detection device and detection method for heavy metals in water described in the present invention can detect heavy metals in water by wireless remote control of the detection device, the wireless data transmission distance is 3500m, and the host computer program can display the concentration of heavy metals in the detected water in real time, which simplifies the detection process; the heavy metal rapid detection device is based on differential pulse stripping voltammetry and can use a variety of different nano-modified electrodes to detect heavy metals in water. It can have a high current response without pre-enrichment operation, has high detection accuracy and small relative error, and the single detection time is within 3 minutes, which reduces the detection time and power consumption and improves the detection speed.

Claims

1. A wireless rapid detection device for heavy metals in water, characterized by: The invention is composed of a heavy metal detection front end (1), an electrochemical detection circuit (2), a microcontroller minimum system (3) and a heavy metal wireless detection terminal (4); the heavy metal detection front end (1) is composed of a three-electrode system with a non-pre-enriched nano-modified electrode as a working electrode, a platinum electrode as an auxiliary electrode and a saturated calomel electrode as a reference electrode; the electrochemical detection circuit (2) is composed of a signal generating circuit (21), a constant potential instrument circuit (22), a signal conditioning circuit (23) and a signal acquisition circuit (24); the microcontroller minimum system (3) is composed of a detection device LoRa wireless communication module (31), a main control chip (32), a CLK clock circuit (33), a SWD burning circuit (34), an RST system reset circuit (35) and a power supply circuit (36); the heavy metal wireless detection terminal (4) is composed of a detection terminal LoRa wireless communication module (41), a heavy metal detection host computer program (42), a communication configuration (43), a test parameter configuration (44), a data processing circuit (45), a data The invention relates to a memory (46); the reference electrode and the auxiliary electrode of the heavy metal detection front end (1) are connected to the constant potential instrument circuit (22), the working electrode is connected to the signal conditioning circuit (23), the signal generating circuit (21) is respectively connected to the constant potential instrument circuit (22) and the main control chip (32), and the signal acquisition circuit (24) is respectively connected to the signal conditioning circuit (23) and the main control chip (32); the power supply circuit (36) is respectively connected to the signal generating circuit (21), the constant potential instrument circuit (22), the signal conditioning circuit (23), the signal acquisition circuit (24), the detection device LoRa wireless communication module (31), the main control chip (32) and the detection terminal LoRa wireless communication module (41); the detection terminal LoRa wireless module (41) is connected to the computer terminal through the serial port to USB interface, and the data is transmitted to the heavy metal detection host computer program (42) in the computer terminal; the wireless heavy metal rapid detection device in water uses the non-pre-enriched nano-modified electrode based on differential pulse stripping voltammetry (DPASV) to detect heavy metals in water.

2. A wireless rapid detection device for heavy metals in water as claimed in claim 1, characterized in that: The power supply circuit (36) is composed of a power supply input circuit, a +3.3V power supply circuit, a +5V and -5V power supply circuit, a +5V_AVDD and a +5V_DVDD power supply circuit, and serves as a power supply for a signal generating circuit (21), a constant potential meter circuit (22), a signal conditioning circuit (23), a signal acquisition circuit (24), a detection device LoRa wireless communication module (31), a main control chip (32) and a detection terminal LoRa wireless communication module (41), including +3.3V, +5V, -5V, +5V _AVDD, +5V_DVDD, a total of 5 voltage levels; wherein the +3.3V voltage is used as the power supply for the LoRa wireless communication module (31) of the detection device, the main control chip (32) and the LoRa wireless communication module (41) of the detection terminal; the +5V voltage and the -5V voltage are used as the bipolar power supply for the operational amplifier in the constant potential instrument circuit (22) and the signal conditioning circuit (23); +5V_DVDD and +5V_AVDD are used as the power supply for the signal generation circuit (21) and the signal acquisition circuit (24); The power input circuit (VCC) consists of a polymer lithium battery socket (U23), a USB power socket (USB1), a TP4056 charging protection chip (U7), a PMOS tube (Q1), a green light-emitting diode (LED1), a red light-emitting diode (LED2), a Schottky diode (D5), a resistor and a capacitor. The VBAT pin 1 of the polymer lithium battery socket (U23) is connected to the positive electrode of the polymer lithium battery, and the pin 2 is connected to AGND and the negative electrode of the polymer lithium battery. The No. 1 and No. 6 pins of the USB socket (USB1) are connected to the analog ground AGND, the No. 2 and No. 5 pins are connected to VIN_5V, and the No. 3 and No. 4 pins are connected to AGND through resistors R13 (5.1kΩ) and R14 (5.1kΩ) respectively; the No. 1 and No. 3 pins of the TP4056 charging protection chip (U7) are directly connected to AGND, the No. 2 pin is connected to AGND through resistor R11 (5kΩ), and the No. 4 and No. 8 pins are connected to VIN_5V through resistor R17 (0.4Ω) , pins 4 and 8 are connected to AGND through parallel filter capacitors C32 (100nF) and C64 (10μF), pin 5 is connected to VBAT, pin 5 is connected to AGND through filter capacitor C35 (1μF), pin 6 is connected to VIN_5V through resistor R19 (1kΩ), green light-emitting diode (LED1) and resistor R17 (0.4Ω), pin 7 is connected to VIN_5V through resistor R18 (1kΩ), red light-emitting diode (LED2) and resistor R17 ( 0.4Ω) is connected to the VIN_5V pin, and pin 9 is left floating; the anode of the Schottky diode (D5) is connected to VIN_5V, and the cathode is connected to VCC; the source D of the PMOS tube (Q1) is connected to VBAT, the gate G is connected to AGND through the resistor R21 (2kΩ), the gate G is also connected to VIN_5V through the resistor R22 (100Ω), the source S is connected to VCC, and the source S is also connected to AGND through the parallel filter capacitors C33 (10μF) and C34 (100nF); The +3.3V power supply circuit is composed of an RT9013-33GB voltage regulator chip (U8), a resistor and a capacitor; pin 1 of the RT9013-33GB voltage regulator chip (U8) is connected to VCC, pin 1 is also connected to AGND via a resistor C65 (1 μF), pin 2 is connected to AGND, pin 3 is connected to VCC, pin 4 is left floating, pin 5 is connected to AGND via a capacitor C66 (1 μF) and a resistor RL2 (1 kΩ) connected in parallel, and pin 5 outputs a +3.3V voltage as a power supply for a LoRa wireless communication module (31) of a detection device, a main control chip (32) and a LoRa wireless communication module (41) of a detection terminal; The +5V and -5V power supply circuits are composed of the MT3608L boost chip (U22), the TPS7A4901 voltage regulator chip (U4), the TPS7A3001 voltage regulator chip (U21), inductors (L1, L2, L3), Schottky diodes (D1, D3), resistors and capacitors; Pin 1 of the MT3608L boost chip is connected to VCC through the inductor L1 (4.7μH), and pin 1 is also connected to coupling capacitors C17 (10μF) and C63 (10μF). Capacitor C63 is connected to AGND through the inductor L2 (4.7μH), and capacitor C63 is also connected to the Schottky diode D 1, the cathode of Schottky diode D1 is connected to pin 3 through resistor R53 (180kΩ), the cathode of Schottky diode D1 is connected to AGND through parallel filter capacitors C15 (100nF) and C16 (22μF), and pin 3 is connected to AGND through resistor R54 (20kΩ); capacitor C17 is connected to AGND through Schottky diode D3, and capacitor C17 is connected to AGND through parallel filter capacitors C18 (100nF) and C19 (22μF) through inductor L3 (4.7μH); pin 2 is connected to AGND, and pin 4 is connected to AGND. The pin 1 and pin 5 are connected to VCC, and pin 5 is connected to AGND through parallel filter capacitors C30 (22μF) and C31 (100nF), and pin 6 is connected to AGND, thereby forming a SEPIC+CUK power supply topology, generating +6V and -6V output voltages at the cathode of Schottky diode D1 and the output end of inductor L3 respectively; pin 2 of the TPS7A4901 voltage regulator chip (U4) is connected to AGND through resistor R55 (6.2kΩ), and is connected to pin 1 through parallel resistor R56 (20kΩ) and capacitor C22 (10nF), and pin 3 is connected to AGND. The pins 4 and 5 are connected to AGND, the pins 5 and 8 are connected to the +6V voltage output by the MT3608L boost chip, and the filter capacitor C21 (10μF) is connected between the pin 8 and AGND; the pin 6 of the TPS7A4901 voltage regulator chip is connected to AGND through the capacitor C20 (10nF), the pin 9 is connected to AGND, the pin 1 is connected to AGND through the parallel resistor R57 (1kΩ) and the capacitor C23 (10μF), and the +5V voltage is output at the pin 1; the pin 2 of the TPS7A3001 voltage regulator chip (U21) is connected to AGND through the resistor R60 (6.2kΩ) is connected to AGND, and connected to pin 1 through a parallel resistor R59 (20kΩ) and a capacitor C26 (10nF), pins 3 and 7 are left floating, pins 4 and 9 are connected to AGND, pins 5 and 8 are connected to the -6V voltage output by the MT3608L boost chip, and a filter capacitor C25 (10μF) is connected between pin 8 and AGND; pin 6 is connected to AGND through a capacitor C24 (10nF), pin 1 is connected to AGND through a parallel resistor R58 (1kΩ) and a capacitor C27 (10μF), and a -5V voltage is output at pin 1; the +5V voltage output from pin 1 of the TPS7A4901 voltage regulator chip and the -5V voltage output from pin 1 of the TPS7A3001 voltage regulator chip are used as bipolar power supplies for operational amplifiers in the potentiostat circuit (22) and the signal conditioning circuit (23); The +5V_DVDD and +5V_AVDD power supply circuits are composed of the TPS61071 boost chip (U9), the TPS7A2050 voltage regulator chip (U2), an inductor (L5), a magnetic bead (L6), a resistor and a capacitor. Pin 1 of the TPS61071 boost chip is connected to VCC through the inductor L5 (4.7μH), and a filter capacitor C71 (10μF) is connected between VCC and AGND. Pin 2 is connected to AGND. Pin 3 and pin 6 are directly connected to VCC; pin 4 is connected to digital ground DGND through resistor R61 (180kΩ), and is connected to pin 5 through resistor R26 (1.8MΩ). Pin 5 is connected to DGND through capacitors C72 (4.7μF) and C37 (4.7μF) in parallel, and a +5.5V voltage is output at pin 5; pins 1 and 3 of the TPS7A2050 voltage regulator chip are connected to the TPS610 The +5.5V voltage output of pin 5 of the 71 boost chip U9 is connected, and a filter capacitor C38 (1μF) is connected between pin 1 and AGND, pins 2 and 4 are connected to DGND, pin 5 is connected to DGND after passing through a filter capacitor C73 (1μF), pin 5 outputs +5V_DVDD, +5V_DVDD outputs +5V_AVDD after passing through a magnetic bead (L6), +5V_AVDD and AGND are connected through a filter capacitor C74 (1μF), capacitor C73, magnetic bead (L6) and capacitor C74 form a πLC filter, and AGND and DGND are connected at a single point through a resistor R27 (0Ω), which is beneficial to reducing the crosstalk between digital signals and analog signals and reducing noise. The +5V_DVDD and +5V_AVDD output by the TPS7A2050 voltage regulator chip are used as power supplies for the signal generation circuit (21) and the signal acquisition circuit (24).

3. A wireless rapid detection device for heavy metals in water as claimed in claim 1, characterized in that: The signal generating circuit (21) is connected between the main control chip (32) and the constant potential meter circuit (22), and is composed of a DAC1220E chip and its driving circuit and two OPA2992 differential amplifier circuits. The main control chip (32) is configured with the signal generating circuit (21) to output a differential pulse stripping voltammetry signal; the DAC1220E chip and its driving circuit are composed of a 2.4576MHz active crystal oscillator (U10), a DAC1220E chip (U11), a 2.5V voltage reference source ADR421 chip (U12), a 100Ω resistor RN1, resistors and capacitors; pins 1, 3, 5, 7 and 8 of the 2.5V voltage reference source ADR421 chip are left floating , pin 2 is connected to +5V_AVDD, pin 4 is connected to AGND, filter capacitor C29 (100nF) is connected between pin 2 and AGND, pin 6 is connected to AGND through capacitor C42 (100nF) and outputs a fixed 2.5V voltage reference source signal VREF_2.5V; pin 1 of the 2.4576MHz active crystal oscillator (U10) is left floating, pin 2 is connected to DGND, pin 3 is connected to pin 3 of the DAC1220E chip (U11), and pin 4 is connected to +5_DVDD; pin 1 of the DAC1220E chip (U11) is connected to +5_DVDD and is also connected to DGN through capacitor C28 (4.7μF) D, pins 2, 6, 7 and 8 are left floating, pin 3 is connected to pin 3 of the 2.4576MHz active crystal oscillator (U10), pin 4 is connected to DGND, pin 5 is connected to +5V_AVDD and connected to AGND through capacitor C43 (4.7μF), pin 9 is connected to VREF_2.5V output by the 2.5V voltage reference source ADR421 through capacitor C40 (10nF), pin 10 is connected to pin 11 through capacitor C39 (3.3nF), pin 11 outputs an adjustable voltage VOUT_DAC1220 of 0 to 5V, pin 12 is connected to VREF_2.5V output by the 2.5V voltage reference source ADR421, A filter capacitor C41 (100nF) is connected between pin No. 12 and AGND, pin No. 13 is connected to AGND, and pins 14, 15, and 16 are respectively connected to SPI pins PC9, PC10, and PC11 of a main control chip (32) through a 100Ω resistor RN1. The main control chip (32) configures pin No. 11 of a DAC1220E chip to output an adjustable voltage value VOUT_DAC1220 within a range of 0 to 5V through the SPI pin. The differential amplifier circuit is composed of two OPA2992 operational amplifiers, a 1kΩ precision resistor, and a 100nF capacitor, wherein the in-phase input end of the first operational amplifier OPA2992, i.e., the OPA2992 chip (U14.Pin 3 of 1) is connected to AGND through resistor R35 (1kΩ), and is connected to the 0-5V adjustable voltage VOUT_DAC1220 output by pin 11 of the DAC1220E chip through resistor R33 (1kΩ). The inverting input, i.e., pin 2, is connected to VREF_2.5V output by the 2.5V voltage reference source ADR421 through resistor R31 (1kΩ). Pin 2 is also connected to pin 1 through resistor R29 (1kΩ); pin 4 of the OPA2992 chip (U14.1) is connected to the output of pin 1 of the TPS7A3001 voltage regulator chip The -5V voltage is connected to AGND through capacitor C47 (100nF). Pin 8 of the OPA2992 chip (U14.1) is connected to the +5V voltage output by pin 1 of the TPS7A4901 voltage regulator chip, and is connected to AGND through capacitor C45 (100nF). Pin 1 outputs the VOUT1 voltage. The first operational amplifier OPA2992 chip (U14.1), resistors R29, R31, R33, and R35 form a subtraction circuit, and its output voltage VOUT1 is equal to the VOUT_DAC1220 voltage minus VRE. F_2.5V voltage; the in-phase input terminal of the second operational amplifier OPA2992, that is, pin 5 of the OPA2992 chip (U14.2), is connected to the output VOUT1 of the first operational amplifier, the inverting input terminal, that is, pin 6 of the OPA2992 chip (U14.2), is connected to AGND through a resistor R32 (1kΩ), a resistor R30 (1kΩ) and a capacitor C44 (100nF) are connected in parallel between pins 6 and 7, and the output terminal, that is, pin 7 of the OPA2992 chip (U14.2), outputs VOUT_DAC through a resistor R34 (1kΩ) Voltage signal, capacitor C46 (100nF), resistor R34 (1kΩ) and capacitor C46 (100nF) are connected to the VOUT_DAC voltage signal and AGND to form an RC low-pass filter for filtering high-frequency noise interference; the second operational amplifier OPA2992 chip (U14.2), resistors R30, R32 and capacitor C44 form a common-phase proportional amplifier circuit, and the output VOUT_DAC voltage is an adjustable voltage value within the range of -5V to +5V, thereby realizing the main control chip (32) configuring the signal generation circuit (21) to output the differential pulse stripping voltammetry signal. .

4. A wireless rapid detection device for heavy metals in water as claimed in claim 1, characterized in that: The constant potential meter circuit (22) is connected between the heavy metal detection front end (1) and the signal generating circuit (21); the differential pulse voltammetry signal is transmitted from the signal generating circuit (21) to the constant potential meter circuit (22), and the output of the constant potential meter circuit (22) is connected to the reference electrode and the auxiliary electrode of the heavy metal detection front end (1); the constant potential meter circuit (22) is composed of a three-way operational amplifier, a buffer BUF634, a resistor and a capacitor, the first operational amplifier, i.e., the No. 4 pin of the OPA4192 chip (U1.1) is connected to the +5V voltage outputted by the No. 1 pin of the TPS7A4901 voltage regulator chip in the power supply circuit (36), and is simultaneously connected to AGND through a filter capacitor C4 (100nF), 1 Pin 1 is connected to the -5V voltage outputted by pin 1 of the TPS7A3001 voltage regulator chip, and is simultaneously connected to AGND via a filter capacitor C8 (100nF). The in-phase input terminal, i.e., pin 3 of the OPA4192 chip (U1.1), is connected to the VOUT_DAC output terminal of the signal generating circuit (21). The output terminal, i.e., pin 1 of the OPA4192 chip (U1.1), is connected to the inverting input terminal of the operational amplifier, i.e., pin 2 of the OPA4192 chip (U1.1), thereby forming a voltage follower, so that the output of pin 1 of the OPA4192 chip (U1.1) is equal to the VOUT_DAC signal. Pin 1 of the OPA4192 chip (U1.1) The inverting input terminal of the second operational amplifier, namely, pin 6 of the OPA4192 (U1.2) chip, is connected to the inverting input terminal of the second operational amplifier through the resistor R4 (10kΩ). The second operational amplifier is also connected to the +5V and -5V voltages output by the power supply circuit (36). The non-inverting input terminal, namely, pin 5 of the OPA4192 chip (U1.2), is connected to AGND. The output terminal, namely, pin 7 of the OPA4192 chip (U1.2), is connected to pin 3 of the buffer BUF634. Pin 4 of the buffer BUF634 is connected to the -5V voltage and is connected to AGND through the filter capacitor C6 (100nF). Pin 7 is connected to the +5V voltage and is connected to Connected to AGND, the output end of the buffer BUF634, i.e., pin 6, is connected to the auxiliary electrode CE of the front end of the heavy metal detection; the third operational amplifier is also connected to the +5V and -5V voltages output by the power supply circuit (36), the output end, i.e., pin 8 of the OPA4192 chip (U1.3), is connected to the inverting input end of the operational amplifier, i.e., pin 9 of the OPA4192 chip (U1.3), to form a voltage follower, a resistor R6 (10kΩ) is connected between pin 8 and pin 6 of the second operational amplifier OPA4192 chip (U1.2), and the same-direction input end, i.e., pin 10 of the OPA4192 chip (U1.3), is connected to the reference electrode (RE) of the front end of the heavy metal detection.

5. A wireless rapid detection device for heavy metals in water as claimed in claim 1, characterized in that: The signal conditioning circuit (23) is connected between the heavy metal detection front end (1) and the signal acquisition circuit (24); the signal conditioning circuit (23) includes a current / voltage conversion circuit composed of an OPA4192 operational amplifier (U1.4) and an ADG1604 multiplexer (U5) and a fourth-order Butterworth low-pass filter composed of an OPA2192 operational amplifier (U6.1, U6.2), resistors and capacitors, and the operational amplifier is connected to the +5V and -5V voltages output by the power supply circuit (36); the in-phase input terminal of the first operational amplifier, i.e., pin No. 12 of the OPA4192 chip (U1.4), is connected to AGND, and the inverting input terminal, i.e., pin No. 12 of the OPA4192 chip (U1.4), is connected to AGND. Pin 13 of chip 2 (U1.4) is connected to the working electrode (WE) of the heavy metal detection front end; at the same time, pin 13 is connected to pin 1 of ADG1604 multiplexer (U5) through parallel resistor R1 (100kΩ) and capacitor C2 (47pF), connected to pin 2 of ADG1604 multiplexer (U5) through parallel resistor R2 (10kΩ) and capacitor C3 (470pF), connected to pin 3 of ADG1604 multiplexer (U5) through parallel resistor R3 (1kΩ) and capacitor C5 (4.7nF), connected to ADG through parallel resistor R5 (100Ω) and capacitor C7 (47nF). The output end of the operational amplifier, namely the pin 14 of the OPA4192 chip (U1.4), is connected to the pin 5 of the ADG1604 multiplexer (U5) to form an I / V conversion circuit, which is used to convert the response current signal related to the heavy metal concentration generated by the working electrode (WE) at the front end of the heavy metal detection into an analog voltage signal and output it from the pin 14 as V_POTENTIAL; the conduction relationship of the ADG1604 multiplexer is changed through the main control chip (32), thereby changing the resistance value of the access resistor to 100, 1k, 10k or 100k respectively, that is, the signal after I / V conversion is the original 100, 1k, 10k or 100k times; that is, when channel 1 is turned on and the other channels are closed, the response current signal generated by the working electrode WE is amplified 100k times by I / V conversion through resistor R1 (100kΩ) and capacitor C2 (47pF) and the output signal V_POTENTIAL is output; when channel 2 is turned on and the other channels are closed, the response current signal generated by the working electrode WE is amplified 10k times by I / V conversion through resistor R2 (10kΩ) and capacitor C3 (470pF) and the output signal V_POTENTIAL is output; when channel 3 is turned on and the other channels are closed, the response current signal generated by the working electrode WE is amplified 10k times by I / V conversion through resistor R3 (1kΩ) and capacitor C5 (4.7nF) is amplified 1k times by I / V conversion and then outputs signal V_POTENTIAL; when channel 4 is turned on and the other channels are closed, the response current signal generated by the working electrode WE is amplified 100 times by I / V conversion through resistor R5 (100Ω) and capacitor C7 (47nF) and then outputs signal V_POTENTIAL; V_POTENTIAL is then connected to the in-phase input terminal of the second operational amplifier, that is, pin 3 of the OPA2192 chip (U6.1), through resistors R7 (14.7kΩ) and R8 (14.7kΩ). The connection end of R8 (14.7kΩ) is connected to pin 1 of the OPA2192 chip (U6.1) through capacitor C13 (120nF). Pin 3 of the OPA2192 chip (U6.1) is connected to AGND through capacitor C10 (100nF). Pin 4 of the OPA2192 chip (U6.1) is connected to -5V voltage and connected to AGND through filter capacitor C11 (100nF). Pin 8 is connected to +5V voltage and connected to AGND through filter capacitor C9 (100nF). The output end of the operational amplifier is OPA2 Pin 1 of the 192 chip (U6.1) is connected to the inverting input terminal of the operational amplifier, that is, pin 2 of the OPA2192 chip (U6.1). Pin 1 is also connected to the non-inverting input terminal of the third operational amplifier, that is, pin 5 of the OPA2192 chip (U6.2) through resistors R9 (6.1kΩ) and R10 (6.1kΩ). Pin 5 of the OPA2192 chip (U6.2) is also connected to AGND through capacitor C12 (100nF). The connection end of resistors R9 (6.1kΩ) and R10 (6.1kΩ) is connected through capacitor C14 (6 80nF) and then connected to the No. 7 pin of the OPA2192 chip (U6.2); the output end of the third operational amplifier OPA2192, namely the No. 7 pin of the OPA2192 chip (U6.2), is connected to the inverting input end of the operational amplifier, namely the No. 6 pin of the OPA2192 chip (U6.2), thereby forming a fourth-order Butterworth low-pass filter to filter out interference and noise in the V_POTENTIAL signal, and the No. 7 pin of the OPA2192 chip (U6.2) outputs an analog voltage signal V_FILTER, which is collected by the signal acquisition circuit (24). .

6. A wireless rapid detection device for heavy metals in water as claimed in claim 1, characterized in that: The signal acquisition circuit (24) is connected between the signal conditioning circuit (23) and the main control chip (32). The signal acquisition circuit (24) is composed of an ADS8691 chip (U13), a 4.096V voltage reference source REF5040 chip (U16), a 51Ω resistor RN2, resistors and capacitors; pins 1, 3, 7 and 8 of the 4.096V voltage reference source REF5040 chip (U16) are suspended, pin 2 is connected to +5V_AVDD, and pin 2 is connected to AGND through capacitors C55 (10μF) and C56 (100nF), pin 4 is connected to AGND, pin 5 is connected to AGND through capacitor C57 (1μF), and pin 6 is connected to AGND through resistor R42 (0.22Ω) and capacitor C58 (10μF) are connected to AGND, and pin 6 is connected to AGND through resistor R43 (0.47Ω) and capacitor C59 (10μF). Pin 6 outputs a fixed 4.096V voltage reference source signal VREF_4.096V; pin 1 of the ADS8691 chip (U13) is connected to DGND, pin 2 is connected to +5V_AVDD, pin 2 is connected to AGND through parallel filter capacitors C49 (1μF) and C51 (100nF), pins 3 and 5 are connected to AGND, pin 4 is connected to the voltage reference source signal VREF_4.096V, and pin 6 is connected to DGND through resistor R39 (0.22Ω) and then connected to AGND through parallel filter capacitors C52 (1μF), C53 (10μF), and C54 (1μF). Pin 9 is connected to the PB13 pin of the main control chip 32 through the resistor RN2. Pin 9 is also connected to +5V_DVDD through the pull-up resistor R40 (10kΩ). Pins 10, 11, 12, and 13 of the ADS8691 chip (U13) are SPI signal pins. Pins 10, 11, and 12 are connected to the main control chip 32 through the resistor RN2. The PB15, PB11 and PB10 pins of the chip (32), the 13 pin is connected to +5V_DVDD through a resistor R38 (51Ω) and a resistor R36 (10kΩ), the connection end of the resistor R38 (51Ω) and the resistor R36 (10kΩ) is connected to the PB8 pin of the main control chip (32), the 14 pin is connected to +5V_DVDD through a resistor R37 (51Ω) and a resistor R12 (10kΩ), the connection end of the resistor R37 (51Ω) and the resistor R12 (10kΩ) is connected to the Output SDO-1 signal, pin 15 of ADS8691 chip (U13) outputs RVS signal, pin 16 of ADS8691 chip (U13) is connected to +5V_DVDD, and pin 16 is connected to AGND through parallel filter capacitors C48 (1μF) and C50 (100nF); pins 7 and 8 of ADS8691 chip (U13) are signal acquisition inputs, and pin 7 is connected to the analog voltage signal V_FILT at the output of signal conditioning circuit (23) ER, pin 8 is connected to AGND, so that the ADS8691 chip (U13) can collect the analog signal through pin 7 and convert it into a digital signal, and then transmit the collected data to the main control chip (32) through pins 10, 11, 12, and 13 of the ADS8691 chip (U13), i.e., the SPI signal pins, and control the collection voltage range and filtering functions of the signal collection circuit (24) through the main control chip (32) to improve the collection accuracy, thereby improving the accuracy of heavy metal concentration detection in water. .

7. A wireless rapid detection device for heavy metals in water as claimed in claim 1, characterized in that: The detection device LoRa wireless communication module (31) and the detection terminal LoRa wireless communication module (41) use the LLCC68 scheme, the working frequency band is 410-493MHz, the baud rate is 115200bps, the air rate is 19.2Kbps, the transmission power is 20dBm, and a transparent transmission mode is used; the detection device LoRa wireless communication module (31) sends the collected data to the detection terminal LoRa wireless communication module (41), and receives the detection instruction sent by the detection terminal LoRa wireless communication module (41), and the parameters configured by the instruction are set by the test parameter configuration (44) function block, so as to realize the data interaction between the microcontroller minimum system (3) and the heavy metal wireless detection terminal (4).

8. A wireless rapid detection device for heavy metals in water as claimed in claim 1, characterized in that: The main control chip (32) is a STM324L431 series chip, which is connected to the SPI signal pins of the DAC1220E chip in the signal generation circuit (21), namely, the 14th, 15th, and 16th pins of the DAC1220E chip, through the PC9, PC10, and PC11 pins. The main control chip (32) is connected to the SPI signal pins of the ADS8691 chip in the signal acquisition circuit (24), namely, the 10th, 11th, 12th, and 13th pins of the ADS8691 chip, through the PB15, PB11, PB10, and PB8 pins, to achieve signal generation. The circuit (21), the signal acquisition circuit (24) and the detection device LoRa wireless module (31) drive control tasks, configure the signal generation circuit (21) to output the differential pulse stripping voltammetry signal, and send the voltage signal data collected by the signal acquisition circuit (24) to the detection terminal LoRa wireless communication module (41) of the heavy metal wireless detection terminal (4) through the detection device LoRa wireless communication module (31); the CLK clock circuit (33) is composed of an 8MHz crystal oscillator (X3), a 32.768KHz crystal oscillator (X4) and a capacitor, 8 Pin 1 of the 8MHz crystal oscillator (X3) is connected to DGND via capacitor C92 (22pF), and pin 1 is connected to XIN pin PH0 of the main control chip (32). Pins 2 and 4 are directly connected to DGND, and pin 3 is connected to DGND via capacitor C91 (22pF), and pin 3 is connected to XOUT pin PH1 of the main control chip (32). The 8MHz crystal oscillator (X3) is used as a high-speed external clock source to provide an 8MHz clock signal to the main control chip (32). Pin 1 of the 32.768KHz crystal oscillator (X4) is connected to XIN pin PH0 of the main control chip (32). Pins 2 and 4 are directly connected to DGND, and pin 3 is connected to DGND via capacitor C91 (22pF), and pin 3 is connected to XOUT pin PH1 of the main control chip (32). The pin is connected to DGND through capacitor C104 (22pF), and pin 1 is connected to TXIN pin PC14 of the main control chip (32). Pin 2 is connected to DGND through capacitor C103 (22pF), and pin 2 is connected to TXOUT pin PC15 of the main control chip (32). A 32.768KHz crystal oscillator (X4) is used as a low-speed external clock source to provide a 32.768KHz clock signal to the main control chip (32). The SWD programming circuit (34) is composed of a socket H20, and pin 1 of the socket H20 is connected to +3.3V connection, pin 2 is connected to SWDIO pin PA13 of the main control chip (32), pin 3 is connected to SWCLK pin PA14 of the main control chip (32), pin 4 is connected to DGND, and the computer uses STLINK equipment to burn the program or debug the main control chip (32) through the SWD burning circuit (34); the RST reset circuit (35) is composed of a button SW2, a resistor R74 (10kΩ) and a capacitor C102 (100nF), pins 1 and 2 of the button SW2 are connected to DGND, pins 3 and 4 are connected to the NRST pin of the main control chip (32), pins 3 and 4 are simultaneously connected to +3.3V through a resistor R74 (10kΩ), and pins 3 and 4 are simultaneously connected to DGND through a capacitor C102 (100nF), and pressing the button SW2 can restore the detection device to its initial state. .

9. A wireless rapid detection device for heavy metals in water as claimed in claim 1, characterized in that: The heavy metal wireless detection terminal (4) is composed of a detection terminal LoRa wireless communication module (41), a heavy metal detection host computer program (42), a communication configuration (43), a test parameter configuration (44), data processing (45), and data storage (46); the heavy metal wireless detection terminal (4) exchanges data with a detection device LoRa wireless communication module (31) in a microcontroller minimum system (3) through the detection terminal LoRa wireless communication module (41), and can realize communication with multiple heavy metal detection terminals (4) in the heavy metal detection host computer program (42); the communication configuration (43) can configure the baud rate, working mode, transmission mode, air rate, communication address, communication channel and transmission power of LoRa data transmission, and connect heavy metal wireless rapid detection devices at different locations. The device can realize continuous detection of heavy metals in multiple places of water; the test parameter configuration (44) can configure the voltage signal of differential pulse stripping voltammetry generated by the signal generating circuit (21), and the parameters include initial potential, termination potential, potential increment, amplitude, pulse width, sampling interval, pulse period and rest time; the data processing (45) can restore the received data to the response current, and then smooth and filter the data through the Savitzky-Golay algorithm. After the detection is completed, the peak value of the heavy metal response current is calculated using the peak-finding algorithm based on local maximum screening, and the voltammetric curve before smoothing and filtering and the voltammetric curve after smoothing and filtering are plotted, and the heavy metal concentration in the water is calculated according to the electrode response current and the heavy metal concentration linear equation, and the concentration value is displayed in the heavy metal detection host computer program (42); The data storage (46) can store various types of data and images involved in the data processing (45) for data storage and backup.

10. A wireless method for rapid detection of heavy metals in water, characterized by: The invention relates to a wireless rapid detection device for heavy metals in water according to any one of claims 1 to 9. After the detection starts, the LoRa wireless communication module (31) of the detection device receives the detection instruction sent by the LoRa wireless communication module (41) of the detection terminal and sends the instruction to the main control chip (32). The main control chip (32) controls the DAC1220E chip in the signal generating circuit (21) to output the corresponding voltage VOUT_DAC according to the differential pulse stripping voltammetry signal parameters set by the test parameter configuration (44) through the SPI bus, generates a differential pulse voltammetry signal, and transmits it to the constant potential meter circuit (22). At the same time, the response current signal related to the heavy metal concentration generated by the working electrode (WE) in the heavy metal detection front end (1) is converted by I / V and the fourth-order low-frequency signal is converted by the signal conditioning circuit (23). After passing through the filter, an analog voltage signal V_FILTER is output, and then the analog voltage signal is converted into a digital signal through a signal acquisition circuit (24) and transmitted to a main control chip (32). The main control chip (32) transmits the data remotely and in real time to a detection terminal LoRa wireless communication module (41) through a detection device LoRa wireless communication module (31); the obtained data is first restored to a response current through a data processing (45) function, and then smoothed and filtered through a Savitzky-Golay algorithm, and a peak-finding algorithm based on local maximum screening is used to obtain a response current peak value, and finally a volt-ampere curve before smoothing and filtering and a volt-ampere curve after smoothing and filtering are drawn, and the heavy metal concentration in water is calculated according to the electrode response current and the heavy metal concentration linear equation, and the concentration value is displayed in a heavy metal detection host computer program (42).

Images