CN108627553A - Platinum electrode multifunctional sensor - Google Patents

Abstract

The invention discloses a platinum electrode multifunctional sensor. The data processing module is composed of a microprocessor and a memory. The communication module is a wireless communication module Zigbee. The data acquisition module detects the temperature, conductivity, pH value, redox potential, For heavy metal ions such as lead ions, the detection signal enters the microprocessor through the A/D converter, and the microprocessor filters, fuses and stores the data. The communication module uses wireless communication technology to realize communication with the remote control center. The microprocessor The processed data is forwarded to the remote control center through the aggregation node. If it is detected that the water quality index is not within the specified range, the alarm circuit will alarm, and the remote control center will query the abnormal index and make corresponding processing. The beneficial effect of the invention is that the sensor has high detection precision and can realize the function of water quality detection.

Description

Platinum electrode multifunctional sensor

technical field

The invention belongs to the technical field of water quality monitoring and relates to the application of platinum electrode multifunctional sensors in aquaculture.

Background technique

With the improvement of technology and management level, aquaculture has gradually transitioned from traditional extensive farming (fish farming in lakes and reservoirs) to intensive farming and high-density intensive farming to obtain high yields. Water quality is crucial to aquaculture. Changes in temperature, conductivity, pH, redox potential, and leakage of heavy metal ions such as lead ions will all result in reduced production and economic losses. Traditional water quality detection sensors have shortcomings such as high cost, inability to measure on-site, single detection results, and low sensitivity, which cannot ensure water quality detection in aquaculture.

Contents of the invention

The object of the present invention is to provide a platinum electrode multi-functional sensor. The beneficial effect of the present invention is that the sensor has high detection accuracy and can realize the function of water quality detection.

The technical scheme adopted in the present invention comprises a data acquisition module, a data processing module, a communication module and a power supply module, and the data acquisition module is composed of a temperature sensor, an electrical conductivity sensor, a pH value ORP sensor, a lead ion sensor and an A/D converter, The data processing module is composed of a microprocessor and a memory. The communication module is a wireless communication module Zigbee. The data acquisition module detects the temperature, conductivity, pH value, oxidation-reduction potential, lead ion and other heavy metal ions in the water body through sensors, and the detection signal is passed through A The /D converter enters the microprocessor, which filters, fuses and stores the data. The communication module uses wireless communication technology to communicate with the remote control center. The microprocessor forwards the processed data to the If the remote control center detects that the water quality index is not within the specified range, the alarm circuit will alarm, and the remote control center will query the abnormal index and make corresponding processing.

Further, the temperature sensor, the conductivity sensor, the PH value ORP sensor, and the lead ion sensor are three-electrode target sensors made of platinum. In the three-electrode target sensor, one of the central electrodes is circular and located in the center, and the other two electrodes are The arc-shaped electrodes surround the central electrode respectively.

Further, the temperature sensor, conductivity sensor, PH value ORP sensor, and lead ion sensor are two-electrode sensors or four-electrode sensors, wherein the two-electrode sensor has two electrodes separated by 5 microns, and a 5V power supply and a 100kΩ resistor are connected between the two electrodes , the sensor is immersed in the test solution containing lead ions and other heavy metal ions; the small gap between the left two electrodes and the right two electrodes of the four-electrode sensor is 5 microns, and the large gap between the middle two electrodes is 50 microns, A 5V power supply and a 100kΩ resistor are connected between the left and right electrodes, and the sensor is immersed in a test solution containing lead ions and other heavy metal ions.

The invention designs a platinum electrode multifunctional sensor, which can measure the temperature, conductivity, pH value, oxidation-reduction potential, lead ion and other heavy metal ions in water, so as to ensure the water quality safety of aquaculture. The platinum electrode multifunctional sensor belongs to the chemical water quality detection sensor (electrode type). It mainly generates a changing voltage or current in the circuit through the electrochemical reaction between the electrode surface and the ions or molecules in the water, and detects the current or voltage change in the circuit. To determine the impact factor in water. The platinum electrode multifunctional sensor consists of a single layer of PVDTi/Pt, which is low in cost and simple in structure and fabrication.

Description of drawings

Fig. 1 is the schematic diagram of platinum electrode multifunctional sensor monitoring system of the present invention;

Fig. 2 is a schematic diagram of a three-electrode target sensor;

Fig. 3 is a schematic diagram of a two-electrode sensor;

Figure 4 is a schematic diagram of a four-electrode sensor.

Detailed ways

The present invention will be described in detail below in combination with specific embodiments.

As shown in FIG. 1 , the present invention includes a data acquisition module 1 , a data processing module 2 , a communication module 3 and a power supply module 4 , and its structure is shown in FIG. 1 . Data acquisition module 1 is made up of temperature sensor 101, conductivity sensor 102, pH value ORP sensor 103, lead ion sensor 104 and A/D converter 105, and data processing module 2 is made up of microprocessor 201, memory 202, communication module 3 It is a wireless communication module Zigbee301, and the data acquisition module 1 detects the temperature, conductivity, pH value, redox potential, lead ion and other heavy metal ions in the water body through the sensor, and the detection signal enters the microprocessor 201 through the A/D converter 105, and the microprocessor Processor 201 filters, fuses and stores the data. The communication module uses wireless communication technology to realize communication with the remote control center. The microprocessor 201 forwards the processed data to the remote control center through the aggregation node. The center queries abnormal indicators and makes corresponding processing.

Wherein, as shown in Figure 2, temperature sensor 101, conductivity sensor 102, pH value ORP sensor 103, lead ion sensor 104 are the three-electrode target sensor 5 that is made of platinum, and in the three-electrode target sensor 5, one of them The center electrode 501 is a circle located at the center, and the other two electrodes are arc-shaped electrodes 502 surrounding the center electrode respectively. The three-electrode target sensor 5 can be used for the detection of conductivity and pH/ORP. During conductivity testing, two external arc electrodes 502 are connected in series with an off-chip resistor R, and the effective current I _rms through the resistor is measured as an indication of conductivity.

During the measurement, a 6200Hz, 0.5V pulse wave V _rms is passed between the two external electrodes, and the effective current I _rms represents the conductivity σ. The sensitivity of the conductivity measurement can be easily adjusted by changing the off-chip resistor R in series with these electrodes. The relationship between conductivity σ and effective current I _rms is shown in formula (1)

Formula (1) follows Ohm's law, where I _max is the saturation current. By changing the resistance R in the circuit, I _max can be optimized for a specific conductivity range.

Ionic conductivity is affected by temperature, and the current will deviate at different temperatures. The effect of water temperature can be reduced by using equation (2).

where _σ0 is the calibrated conductivity at a given temperature _T0 , and _σt is the conductivity at temperature T. Combining formula (1) and formula (2)

Then we can use formula (4) to describe the conductivity in solution

Detection of pH value and redox potential

pH and redox potential were measured. In the pH value and oxidation-reduction potential test, the largest electrode is the anode (+), the middle electrode is the cathode (-), and the smallest electrode is the ORP detection electrode. Experiments have shown that in the electrified state, in a solution containing chloride ions, the cathode potential of the sensor remains relatively constant, and the electrochemical reaction that produces a stable cathode potential is that the active sites on the surface of the platinum cathode are occupied by chloride through adsorption, so the cathode Potential can be used as reference potential. In addition, the anode potential varies with pH, and the minimum electrode potential varies with ORP, so the potential difference between the anode and the minimum electrode is measured as △V1 (>0) and the potential difference between the cathode and the minimum electrode is ΔV2 (<0) . △V2 represents the oxidation-reduction potential, and the potential difference between the anode and the cathode, namely △V1-△V2 represents the pH value. Record the pH value, redox potential and the corresponding potential difference, draw the pH-(△V1—△V2) curve and the ORP-△V2 curve respectively, and the microprocessor can measure the corresponding pH by detecting the potential difference on the sensor value and redox potential. In aquaculture, chloride ions are ubiquitous in water, so this sensor can be used for water quality monitoring.

When the concentration of strong oxidizing agents (such as hypochlorite) is higher than 1ppm, the cathodic potential may change significantly and the pH/ORP sensor will lose sensitivity. Coating on the surface of the electrode can reduce the influence of the strong oxidant solution on the cathode potential. Chlorinated PVC film is not easy to penetrate hypochlorite, it is coated on the surface of the electrode to block

^The influence of ClO-, keeping the cathode potential stable, the sensor can continue to work normally.

Two-electrode sensor design

Detection of lead ions and other heavy metal ions

The two-electrode system is shown in Figure 3, and the two electrodes are separated by 5 microns. A 5V power supply and a 100kΩ resistor are connected between the two electrodes. The sensor is immersed in a test solution containing lead ions and other heavy metal ions, and the voltage difference △V across the resistor is measured as a signal. ΔV reflects the overall impedance across the electrodes, and ΔV increases when the impedance between two electrodes decreases.

When the system is energized, heavy metal ions (copper ions, iron ions and zinc ions) are reduced to conductive metals on the cathode due to their reducing properties. If the reduced metal connects the gap between the platinum electrodes, the impedance of the system will drop significantly, the current in the system will increase, and the voltage difference ΔV across the resistor R will increase. The change of the voltage difference ΔV due to the change of impedance is the basis for the existence of heavy metals in the solution.

Lead ions are the only ions that can deposit conductive species around the anode. The main reaction around the anode is the oxidation reaction, and lead ions can be oxidized into a conductive substance - lead dioxide, the chemical equation is

Pb ²⁺ -2e ^- +2H ₂ O→PbO ₂ +4H ⁺ (5)

When the deposited lead dioxide connects the gap between the platinum electrodes, the system impedance decreases and the voltage difference ΔV across the resistor R increases. In the two-electrode system, whether the presence of lead ions or other heavy metal ions will lead to an increase in ΔV, the sensor can effectively detect the presence of ions.

Four-electrode sensor design

In a solution containing lead ions and other heavy metal ions, in the electrified state, heavy metal ions undergo a reduction reaction and deposit on the cathode, while lead ions undergo an oxidation reaction to form lead dioxide and deposit on the anode. According to the characteristics of lead ions, the design The four-electrode system is shown in Fig. 4. In the figure, the small gap between the two electrodes on the left and the two electrodes on the right is 5 microns, and the large gap between the two electrodes in the middle is 50 microns. The system can not only detect the presence of lead ions and other heavy metal ions, but also distinguish and identify the most toxic lead. When the sensor is connected as Aa-BB', the voltage difference across the resistor is measured as △V1 to measure the impedance between the anode and the second electrode for the determination of lead ions; when the sensor is connected as AA'-Bb, The voltage difference across the resistor is measured as ΔV2 to measure the impedance between the cathode and the third electrode for the determination of other heavy metal ions.

test experiment

The performance of the sensor is tested by the principle of unique variable, and the interference of other factors is excluded. Since the sensor can only detect the presence of lead ions and other heavy metal ions, but cannot measure their concentration, when detecting lead ions and other heavy metal ions, an alarm is connected to the circuit to detect the change of the circuit current, and the alarm is judged by whether the alarm Existence of lead ions and other heavy metal ions in water. Only the test results of temperature, pH value, lead ion and other heavy metal ions are given in Table 1.

Table 1 Experimental test results

After testing, the changes of each parameter are small, the alarm is normal and there is no abnormality, the sensor can realize the accurate detection of temperature, conductivity, pH value, redox potential, lead ion and other heavy metal ions, and meet the needs of actual operation.

The platinum electrode multifunctional sensor of the present invention can detect six water quality indicators of temperature, conductivity, pH value, oxidation-reduction potential, lead ion and other heavy metal ions, and overcomes the shortcomings of single detection results of traditional water quality detection sensors. The sensor is composed of a single layer of PVDTi/Pt, and since the platinum electrode is an inert electrode, the sensor can perform long-term detection. In addition, the sensor made by this process is low in cost, simple in structure and manufacture, and has good economic benefits, and will have a good development prospect in the application of water quality detection.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Any simple modifications made to the above embodiments according to the technical essence of the present invention, equivalent changes and modifications, all belong to this invention. within the scope of the technical solution of the invention.

Claims (3)

1. Platinum electrode multifunctional sensor, it is characterized in that: comprise data acquisition module, data processing module, communication module and power supply module, data acquisition module is made of temperature sensor, conductivity sensor, PH value ORP sensor, lead ion sensor and A/D The data processing module is composed of a microprocessor and a memory. The communication module is a wireless communication module Zigbee. The data acquisition module detects the temperature, conductivity, pH value, oxidation-reduction potential, lead ion and other heavy metal ions in the water body through sensors. The detection signal enters the microprocessor through the A/D converter. The microprocessor filters, fuses and stores the data. The communication module uses wireless communication technology to communicate with the remote control center. The microprocessor passes the processed data through The aggregation node forwards it to the remote control center. If it detects that the water quality index is not within the specified range, the alarm circuit will alarm, and the remote control center will query the abnormal index and make corresponding processing. 2. according to the described platinum electrode multifunctional sensor of claim 1, it is characterized in that: described temperature sensor, conductivity sensor, pH value ORP sensor, lead ion sensor are three electrode target type sensors made of platinum, three electrode target In the type sensor, one of the central electrodes is circular and located in the center, and the other two electrodes are arc-shaped electrodes respectively surrounding the central electrode. 3. according to the described platinum electrode multifunctional sensor of claim 1, it is characterized in that: described temperature sensor, conductivity sensor, pH value ORP sensor, lead ion sensor are two-electrode sensor or four-electrode sensor, and wherein two-electrode sensor is two The two electrodes are separated by 5 microns, a 5V power supply and a 100kΩ resistor are connected between the two electrodes, and the sensor is immersed in the test solution containing lead ions and other heavy metal ions; the small between the two electrodes on the left and the two electrodes on the right of the four-electrode sensor The gap is 5 microns, and the large gap between the middle two electrodes is 50 microns. A 5V power supply and a 100kΩ resistor are connected between the left and right electrodes. The sensor is immersed in a test solution containing lead ions and other heavy metal ions.