CN108761209A - A kind of liquid electric conductivity measurement method and device - Google Patents

Abstract

The present invention provides a method and device for measuring the conductivity of a liquid. The method includes: sending sine wave excitation signals with different frequencies to electrode A 310; receiving coupling signals with different frequencies from electrode B 311; calculating the coupling signals of different frequencies The voltage value corresponding to the signal; the conductivity is calculated using the voltage value corresponding to the coupled signal of different frequencies. It overcomes at least one of the shortcomings of the existing conductivity measurement technology that the conductivity measurement electrode is easy to corrode, the conductivity measurement accuracy is affected by the deposit on the electrode surface, and the water temperature measurement increases the complexity of the watertight structure. Low cost and practical.

Description

Method and device for measuring liquid conductivity

technical field

The invention relates to the field of environmental protection, in particular to a liquid conductivity measurement method and device.

Background technique

The water quality online monitoring system uses on-line analytical instruments and laboratory analytical instruments to detect water quality, and realizes online automatic monitoring of samples by collecting representative, timely and reliable samples. An automatic monitoring system generally includes a sampling system, a preprocessing system, a data acquisition and control system, an online monitoring and analysis instrument, a data processing and transmission system, and a remote data management center. Continuous and reliable operation of the automatic monitoring system.

Since 1998, my country has successively established 100 national surface water quality automatic monitoring stations in 10 key river basins of the seven major river systems, and various localities have successively established more than 400 local-level surface water quality automatic monitoring stations according to the needs of environmental management station, realized the automatic monitoring of water quality weekly. The current water quality automatic monitoring device can no longer meet the needs of the rapid development of water quality monitoring in manufacturing. Therefore, the domestic automatic monitoring device has broad development prospects and potential sales markets.

The multi-parameter water quality online automatic monitoring system is suitable for: water source monitoring, environmental protection monitoring stations, municipal water treatment process, municipal pipe network water quality supervision, rural tap water monitoring; circulating cooling water, swimming pool water operation management, industrial water recycling, industrial aquatic products fields such as farming.

The software architecture of the online water quality monitoring system can expand hundreds of monitoring nodes, and each node can be configured with multiple sensors. According to the actual operation situation, the test water quality parameters can be added, for example: the user can choose the water routine parameters monitored by traditional sensors, such as turbidity, conductivity, redox potential, total organic carbon, ammonia nitrogen, COD, various organic matter, Free chlorine, total chlorine, total fluorine, PH value, flow, pressure, temperature, etc. At the same time, various chemical pollutants can be selectively monitored according to local water resource conditions and past pollution events.

The water quality online monitoring system can quickly and accurately extract important water quality data and present the data in a clear report format. A standard report includes the following information: Water General Indicators, Maximum, Minimum, Average, System Status.

Water quality online analysis instruments are usually divided into electrode method and photometric method according to the measurement method.

According to the measured parameters, the water quality online analysis instruments are divided into the following types:

The design of the water intake system is mainly designed to meet the representativeness, reliability and continuity of water samples. The main components of the system are: water intake head, water intake pump, water sample delivery pipeline and flow rate and flow adjustment. According to the division of water intake methods, it is mainly divided into two types: direct extraction type and buoy type. The direct extraction type is mainly used in environments with small water level changes, such as sewage plants, pollution sources, tap water culvert pipes, etc., while the buoy type is mainly used in environments with large water level changes. Environmental use, such as surface water, etc.

The pretreatment system of the online water quality monitoring system is mainly to eliminate the factors that interfere with the analysis of the instrument and the use of the instrument without losing the representativeness of the water sample. Pretreatment methods usually include natural sedimentation, physical filtration and infiltration. The level of pretreatment is usually determined according to the purity of the water sample. Some analytical instruments have been designed with sample pretreatment in mind, and should be used in conjunction with system integration.

The data acquisition and control of the water quality online monitoring system is mainly composed of PLC, on-site industrial computer, central station computer, transmitter, actuator, etc. Its functions mainly include:

(1) Control the automatic operation of the entire online monitoring system, which is mainly completed by the PLC after writing the program;

(2) Collect, store and transmit the data analyzed by the instrument. This part is mainly completed by the on-site industrial computer and the data collection and transmission module.

The integrated auxiliary system of the water quality online monitoring system is mainly to ensure the continuous and stable operation of the online monitoring system, and it needs to make corresponding adjustments according to the changes of the site conditions. In general, the following aspects need attention:

(1) Cleaning of the pipeline: Since the remaining dirt in the pipeline and the resulting algae will pollute the water sample, it is necessary to clean the pipeline regularly and quantitatively. There are various cleaning methods and contents, and the goals are all It is to ensure the authenticity and representativeness of the water samples.

(2) Power guarantee: The stability of power is directly related to the accuracy and continuity of instrument analysis, so firstly choose a stable AC grid for access; secondly, before the AC enters the automatic monitoring system, the current needs to be checked again. rectification, in order to cope with the occurrence of sudden current instability; finally, if necessary, a backup power supply can be equipped for the normal operation of the online monitoring system during power failure.

(3) Prevention of lightning strikes: lightning protection is mainly divided into station building lightning protection, power supply lightning protection and communication lightning protection. When lightning strikes, the current first breaks through the lightning protector to protect instruments and system equipment. This is especially important in areas where thunderstorms occur frequently. When a thunderstorm occurs, the staff should check the status of the lightning arrester as soon as possible, and replace it in time if it is damaged.

(4) Adjust temperature and humidity: suitable temperature and humidity are also very important for the stable operation of the instrument, and this part of the function is mainly realized by air conditioners and dehumidification equipment.

The probes of existing electrode-type multi-parameter water quality monitors (for example, DCT-MWQ-5100/5101) can be combined freely, replaced independently, plug and play, and can be controlled remotely; scalability: monitor multiple factors at the same time, can Install 2-12 sensors; multiple applications: long-term online work, rapid on-site measurement, emergency monitoring, groundwater monitoring, self-contained battery; solid shell: POM material (metaldehyde polymer), anti-seawater corrosion, can be underwater 200 The meter works normally; the structure is compact: the diameter is 76mm, and it can be installed in small-sized occasions.

The existing water quality five-parameter sensor adopts advanced modular design and advanced digital communication technology. It is composed of a general-purpose controller and a sensor. A general-purpose controller can be connected to five Support sensors, and can realize the same screen display. Among them, the turbidity sensor has a built-in ultrasonic cleaning module to ensure the stability and accuracy of long-term work.

In the field of patent application, the following conductometric measurement technology appears:

The application number is CN201721555968.6, and the utility model titled "a conductivity measuring instrument" includes a conductivity sensor, an excitation signal generation circuit that provides an excitation source for the conductivity sensor, and performs an output signal for the conductivity sensor. Amplifying and shaping circuit, DC conversion circuit, analog-to-digital conversion circuit and controller, excitation signal generation circuit includes square wave excitation source and filter circuit, square wave excitation source, filter circuit, conductivity sensor, amplification and shaping circuit, DC conversion The circuit, the analog-to-digital conversion circuit and the controller are connected in sequence, the controller is connected to the square wave excitation source and provides a clock signal for the square wave excitation source, the conductivity measuring instrument also includes a temperature compensation circuit, and the temperature compensation circuit communicates with the control circuit through the analog-to-digital conversion circuit. device connection.

The application number is CN201710270275.0, and the title of the invention is "measurement device and method for water conductivity and resistivity detection". The device includes a sequentially connected measurement circuit, a subtraction circuit, an AD conversion circuit, and a main chip; Chip connection; the method includes: the measuring circuit loads different voltages to both ends of the electrodes according to the positive pulse square wave excitation from the main chip, so that alternating forward and reverse currents are generated in the water and amplified and detected to obtain signal voltages V1 and V2; The subtraction circuit subtracts the signal voltages V1 and V2 to obtain the measurement signal Vout; the AD conversion circuit performs AD conversion on the measurement signal Vout; the main chip calculates the conductivity or resistivity of water according to the measurement signal Vout after AD conversion. The invention adopts a positive pulse square wave to excite the solution to be tested, and an excitation amplifying circuit is set so that the conductivity cell has positive and negative currents flowing when the positive pulse square wave is excited, so as to resist the polarization effect.

The application number is CN201611172938.7, and the invention name is "a water resource conductivity measurement circuit with temperature compensation". The processor module is connected to the excitation source circuit signal, the excitation source circuit is connected to the conductivity probe signal, and the conductivity probe is The signal connection of the range switching circuit, the signal connection of the range switching circuit and the true effective value conversion circuit, the signal connection of the true effective value conversion circuit and the analog-to-digital conversion circuit, the signal connection between the analog-digital conversion circuit and the processor module, the temperature value probe and the signal conditioning circuit signal Connection, the signal conditioning circuit is connected with the signal of the analog-to-digital conversion circuit, and the power supply module is connected with the power supply of all other modules. The invention has the functions and characteristics of automatic temperature compensation, manual range adjustment, high-precision analog acquisition and the like.

The application number is CN201610583932.2, and the title of the invention is "a conductivity measuring method, circuit and conductivity measuring instrument". A conductivity measuring method is provided, the method includes: generating an AC square wave signal; amplifying the AC square wave signal; Connect the amplified square wave signal to one end of the electrode through a wire to generate an alternating electric field in the electrolyte solution; through the other end of the electrode to detect the weak alternating current signal generated by the electrolyte solution at both ends of the electrodes of the conductivity meter in the alternating electric field ; Transform the weak AC current signal into an AC voltage signal; rectify and filter to obtain a stable DC voltage signal; convert the DC voltage signal into a corresponding conductivity display.

The application number is CN201520679587.3, and the invention name is a utility model given as "a high-precision conductivity measurement system", which discloses a high-precision conductivity measurement system, including a quadrupole conductivity measurement system for measuring the conductivity of liquid media. The test voltage generation module is connected with the four-pole conductivity sensor, and under the control of the control module, the test voltage signal is generated and transmitted to the test plate and the reference voltage signal is transmitted to the reference plate; the current sampling module is used for sampling The current signal generated by the four-pole conductivity sensor is amplified by the preamplifier module and the secondary amplifier module, and then output to the control module. The control module obtains the conductivity value through calculation and displays the data information through the display module. Adopting the technical solution of the utility model, through automatic multi-range switching, a suitable range range can be selected according to different test environments. At the same time, a four-pole conductivity sensor can be used to automatically adjust the test voltage according to the reference electrode to realize automatic compensation, thereby providing measurement accuracy.

The application number is CN201410828826.7, and the invention name is "a liquid conductivity measurement electrode with a micro-pump". The first electrode and the second electrode are cylindrical straight tubes with unequal diameters and equal heights, the first electrode is a cylindrical straight tube with a bottom surface, and the second electrode is a cylindrical straight tube without a bottom surface; the second electrode and the first electrode Coaxial and aligned with the end faces to form two aligned electrode end faces, the end face corresponding to the first electrode with the bottom surface is called the first aligned electrode end face, the other end face is called the second aligned electrode end face, and the second electrode surrounds the first electrode , there is a uniform gap between the cylindrical side walls of the two electrodes, and the end face of the first alignment electrode is coaxially connected with the outlet end of the micro water pump. The innovation of this technical solution lies in preventing the electrode surface from gathering and attaching ions to form a stable electric double layer and avoiding electrode polarization.

The application number is CN201310560258.2, and the title of the invention is "a method for measuring conductivity and a system for measuring conductivity using the method". The method for measuring conductivity includes: using a conductivity standard solution to obtain a conductivity cell Conductivity cell constant; inject the solution to be measured into the conductivity cell, and apply a predetermined DC voltage to the electrodes in the conductivity cell by changing the predetermined DC voltage in stages at each preset time t; according to the voltage The resistance of the solution is obtained as a slope from a linear relationship between the peak current measured for each voltage and the peak current; and the conductivity of the solution is calculated using the cell constant and the resistance of the solution.

Although the existing conductivity measurement devices can maintain good performance in lightly polluted waters, in heavily polluted waters, direct contact between electrodes and sewage for a long time will cause conductivity measurement electrodes to be easily corroded, and conductivity measurement accuracy is affected by electrode surface deposition. The disadvantage of increasing the complexity of the watertight structure due to the influence of objects and the measurement of water temperature.

The invention provides a liquid conductivity measurement method and device, which are used to overcome the existing conductivity measurement technology that the conductivity measurement electrode is easy to corrode, the conductivity measurement accuracy is affected by the deposit on the electrode surface, and the water temperature measurement increases the complexity of the watertight structure at least one of these disadvantages.

Contents of the invention

The invention provides a liquid conductivity measurement method and device, which are used to overcome the existing conductivity measurement technology that the conductivity measurement electrode is easy to corrode, the conductivity measurement accuracy is affected by the deposit on the electrode surface, and the water temperature measurement increases the complexity of the watertight structure at least one of these disadvantages.

The present invention provides a liquid conductivity measurement method, comprising the following steps:

A method for measuring liquid conductivity, comprising the steps of:

Step S110, sending sine wave excitation signals with different frequencies to the electrode A 310;

Step S120, receiving coupling signals with different frequencies from the electrode B 311;

Step S130, calculating voltage values corresponding to coupling signals of different frequencies;

Step S140, using the voltage values corresponding to the coupling signals of different frequencies to calculate the conductivity.

The present invention provides a liquid conductivity measuring device, which includes the following modules:

Excitation channel module 380, electrode A 310, receiving channel module 390, electrode B 311 and processor 320; wherein,

An excitation channel module 380, configured to send sine wave excitation signals with different frequencies to the electrode A 310, including an excitation signal generation module 330 and an excitation signal amplification module 331;

Electrode A 310, used to inject sine wave excitation signals of different frequencies into the liquid 300, including metal conductors;

The receiving channel module 390 is used to receive coupling signals with different frequencies from the electrode B 311, including a coupling signal sampling module 340, a coupling signal amplification module 341, a coupling signal peak holding module 342, and an A/D sampling module 343;

The electrode B 311 is used to detect the coupling signal of the liquid 300 to the sine wave excitation signals of different frequencies, including metal conductors;

The processor 320 is used to calculate the voltage values corresponding to the coupling signals of different frequencies, and use the voltage values to calculate the conductivity, including an operation unit, a storage unit and a peripheral interface circuit.

The method and device provided in the embodiments of the present invention can overcome the shortcomings of the existing conductivity measurement technology, such as the conductivity measurement electrode is easy to corrode, the conductivity measurement accuracy is affected by the deposit on the electrode surface, and the water temperature measurement increases the complexity of the watertight structure. at least one. Low cost and practical.

Additional features and advantages of the invention will be set forth in the description which follows.

Description of drawings

Fig. 1 is the flowchart of a kind of liquid conductivity measurement method that the embodiment of the present invention provides;

Fig. 2 is a schematic diagram of a liquid conductivity measurement equivalent circuit provided by an embodiment of the present invention;

Fig. 3 is a schematic composition diagram of a liquid conductivity measuring device given in an embodiment of the present invention.

Embodiment of the invention

The invention provides a liquid conductivity measurement method and device, which are used to overcome the existing conductivity measurement technology that the conductivity measurement electrode is easy to corrode, the conductivity measurement accuracy is affected by the deposit on the electrode surface, and the water temperature measurement increases the complexity of the watertight structure at least one of these disadvantages. Low cost and practical.

In order to make the purpose, technical solution and advantages of the present invention more clear, the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined arbitrarily with each other.

The conductivity measurement includes an indirect method and a direct method. In order to overcome the shortcoming that the conductivity measurement electrode is easy to corrode, the present invention adopts the indirect method to realize the conductivity measurement.

The embodiment of the conductivity measurement given by the present invention adopts the indirect method to measure the conductivity. In the indirect method of conductivity measurement, the surface of the electrode is covered with an insulating layer or an insulating sheet, which does not directly contact with the sewage, but conducts the conductivity through the insulating protective layer. The advantage of measurement is that it is easy to realize the physical isolation between the conductivity measurement electrode and the measured liquid, so that the electrode does not directly contact the liquid, but conducts the conductivity measurement of the liquid (such as sewage) through the insulating protective layer.

In the following, an example of a position detection method and a system provided by the present invention will be described with reference to the accompanying drawings.

Embodiment 1, an example of a liquid conductivity measurement method

Referring to shown in Fig. 1, a kind of liquid conductivity measurement method embodiment provided by the present invention comprises the following steps:

Step S110, sending sine wave excitation signals with different frequencies to the electrode A 310;

Step S120, receiving coupling signals with different frequencies from the electrode B 311;

Step S130, calculating voltage values corresponding to coupling signals of different frequencies;

Step S140, using the voltage values corresponding to the coupling signals of different frequencies to calculate the conductivity.

The method given in this embodiment, wherein,

The sending of sine wave excitation signals with different frequencies to the electrode A 310 includes:

The processor 320 controls the excitation signal generation module 330 to generate sine wave signals with first, second and third frequencies, and the sine wave signals of the first, second and third frequencies are sent to the electrode A through the excitation signal amplification module 331 310 , the electrode A310 injects the received sine wave signal into the liquid 300 .

Specifically, the excitation signal generation module 330 includes a DDS (Direct Digital Synthesizer; Direct Digital Synthesizer) sub-module, and the DDS sub-module generates sine wave signals of the first, second and third frequencies, and the first, second and third frequencies The sine wave signal is sent to the electrode A 310 after being amplified by the excitation signal amplification module 331 .

Specifically, the excitation signal amplifying module 331 amplifies the power of the sine wave signals of the first, second and third frequencies.

Further, the processor 320 controls the excitation signal generation module 330 to generate the first, second and third frequency sine wave signals, including the processor 320 controlling the excitation signal generation module 330 to generate the first, second and third frequencies in a time-division manner. Three frequency sine wave signals; or, the processor 320 controls the excitation signal generation module 330 to generate first, second and third frequency sine wave signals concurrently;

Preferably, the processor 320 controls the excitation signal generating module 330 to generate sine wave signals of the first, second and third frequencies in a time-division manner.

The method given in this embodiment, wherein,

The slave electrode B 311 receives coupled signals with different frequencies, including:

Processor 320 receives through receiving channel module 390 and electrode B 311 receives sine wave coupling signals with first, second and third frequencies, and said sine wave coupling signal is the equivalent resistance of water and the sampling resistance in series divided voltage.

Specifically, the electrode B 311 detects the coupling signal of the electrode A 310 injecting the liquid 300 to the sine wave excitation signal with the first, second and third frequencies, and the coupling signal is the liquid 300 pair with the first, second and third frequency The voltage division signal of the frequency sine wave excitation signal;

The coupling signal detected by the electrode B 311 is sampled by the coupling signal sampling module 340 , and sent to the processor 320 through the coupling signal amplification module 341 , the coupling signal peak holding module 342 and the A/D sampling module 343 .

Further, after the coupling signal detected by the electrode B 311 is sampled by the coupling signal sampling module 340, it is sent to the processor 320 through the coupling signal amplification module 341, the coupling signal peak holding module 342 and the A/D sampling module 343, including:

The coupling signal amplification module 341, the coupling signal peak holding module 342 and the A/D sampling module 343 process the sine wave coupling signals with the first, second and third frequencies in a time-division manner; or,

The coupling signal amplification module 341, the coupling signal peak holding module 342 and the A/D sampling module 343 process the sine wave coupling signals with first, second and third frequencies in parallel;

Preferably, the coupled signal amplification module 341 , the coupled signal peak hold module 342 and the A/D sampling module 343 process the sine wave coupled signals with the first, second and third frequencies in a time-division manner.

Specifically, the coupling signal amplifying module 341 amplifies the collected weak sine wave coupling signals of the first, second and third frequencies.

Specifically, the coupling signal peak holding module 342 holds the peak values of the sine wave coupling signals of the first, second and third frequencies.

Specifically, the A/D sampling module 343 performs analog-to-digital conversion on the peak values of the sine wave coupling signals of the first, second and third frequencies, and the converted digital signals are sent to the processor 320 .

The method given in this embodiment, wherein,

The calculation of the voltage values corresponding to the coupling signals of different frequencies specifically includes:

calculating first, second and third voltage values corresponding to peak values of the sine wave coupling signals of the first, second and third frequencies;

The calculation of the conductivity using the voltage values corresponding to the coupling signals of different frequencies specifically includes:

The equivalent resistance Rx is calculated using the first, second and third voltage values, and then converted into the conductivity of the liquid 300 .

The model of the indirect method conductivity measurement comprises the common influence of electrode, insulating spacer and water body, and the model of the indirect method conductivity measurement that the present embodiment adopts is as shown in Figure 2, wherein,

Cy is the equivalent capacitance generated between the conductive layers of the two electrodes, Cx is the equivalent capacitance formed between the conductive layers of the two electrodes and the measured liquid, and Rx is the equivalent resistance of the measured liquid. The equivalent impedance model between two electrodes is shown in formula (1).

………………..Formula 1)

Transform the formula (1) to get the complex expression (2)

……….Formula (2)

The corresponding output impedance of the electrode output in the liquid is obtained by the modulo operation of formula (2) , in order to solve Rx, Cy, Cx at this time, it is only necessary to select three suitable sine wave excitation signals, that is, the sine wave excitation signals of the first, second and third frequencies, and obtain the same frequency as the first, second and third The first, second and third voltage values corresponding to the peak values of the frequency sine wave coupling signal can be solved for corresponding parameters.

The method given in this embodiment, wherein,

The calculation of the equivalent resistance Rx by using the first, second and third voltage values, and then converting it into the conductivity of the liquid 300 specifically includes:

Use the temperature measurement module 360 to obtain the temperature value of the liquid 300

The normalized equivalent conductivity of the liquid 300 is solved for using the temperature value of the liquid 300 .

The normalized equivalent conductivity calculation relationship is as follows:

Conductivity value at 25 degrees = actual conductivity value/(1+0.02*(t-25));

Among them, 0.02 is the temperature compensation coefficient; t is the actual water temperature.

Embodiment 2, an example of a liquid conductivity measuring device

Referring to Fig. 2, a kind of liquid conductivity measuring device embodiment provided by the present invention comprises:

Excitation channel module 380, electrode A 310, receiving channel module 390, electrode B 311 and processor 320; wherein,

An excitation channel module 380, configured to send sine wave excitation signals with different frequencies to the electrode A 310, including an excitation signal generation module 330 and an excitation signal amplification module 331;

Electrode A 310, used to inject sine wave excitation signals of different frequencies into the liquid 300, including metal conductors;

The receiving channel module 390 is used to receive coupling signals with different frequencies from the electrode B 311, including a coupling signal sampling module 340, a coupling signal amplification module 341, a coupling signal peak holding module 342, and an A/D sampling module 343;

The electrode B 311 is used to detect the coupling signal of the liquid 300 to the sine wave excitation signals of different frequencies, including metal conductors;

The processor 320 is used to calculate the voltage values corresponding to the coupling signals of different frequencies, and use the voltage values to calculate the conductivity, including an operation unit, a storage unit and a peripheral interface circuit.

The device provided in this embodiment, wherein,

The excitation channel module 380 is configured to perform the operation of sending sine wave excitation signals with different frequencies to the electrode A 310, specifically including the following steps:

The processor 320 controls the excitation signal generation module 330 to generate sine wave signals with first, second and third frequencies, and the sine wave signals of the first, second and third frequencies are sent to the electrode A through the excitation signal amplification module 331 310 , the electrode A310 injects the received sine wave signal into the liquid 300 .

Specifically, the excitation signal generation module 330 includes a DDS (Direct Digital Synthesizer; Direct Digital Synthesizer) sub-module, and the DDS sub-module generates sine wave signals of the first, second and third frequencies, and the first, second and third frequencies The sine wave signal is sent to the electrode A 310 after being amplified by the excitation signal amplification module 331 .

Specifically, the excitation signal amplifying module 331 amplifies the power of the sine wave signals of the first, second and third frequencies.

Further, the processor 320 controls the excitation signal generation module 330 to generate the first, second and third frequency sine wave signals, including the processor 320 controlling the excitation signal generation module 330 to generate the first, second and third frequencies in a time-division manner. Three frequency sine wave signals; or, the processor 320 controls the excitation signal generation module 330 to generate first, second and third frequency sine wave signals concurrently;

Preferably, the processor 320 controls the excitation signal generating module 330 to generate sine wave signals of the first, second and third frequencies in a time-division manner.

The device provided in this embodiment, wherein,

The receiving channel module 390 is configured to perform the operation of receiving coupling signals with different frequencies from the electrode B 311, specifically including the following operation steps:

Processor 320 receives through receiving channel module 390 and electrode B 311 receives sine wave coupling signals with first, second and third frequencies, and said sine wave coupling signal is the equivalent resistance of water and the sampling resistance in series divided voltage.

Specifically, the electrode B 311 detects the coupling signal of the electrode A 310 injecting the liquid 300 to the sine wave excitation signal with the first, second and third frequencies, and the coupling signal is the liquid 300 pair with the first, second and third frequency The voltage division signal of the frequency sine wave excitation signal;

The coupling signal detected by the electrode B 311 is sampled by the coupling signal sampling module 340 , and sent to the processor 320 through the coupling signal amplification module 341 , the coupling signal peak holding module 342 and the A/D sampling module 343 .

Further, after the coupling signal detected by the electrode B 311 is sampled by the coupling signal sampling module 340, it is sent to the processor 320 through the coupling signal amplification module 341, the coupling signal peak holding module 342 and the A/D sampling module 343, including:

The coupling signal amplification module 341, the coupling signal peak holding module 342 and the A/D sampling module 343 process the sine wave coupling signals with the first, second and third frequencies in a time-division manner; or,

The coupling signal amplification module 341, the coupling signal peak holding module 342 and the A/D sampling module 343 process the sine wave coupling signals with first, second and third frequencies in parallel;

Preferably, the coupled signal amplification module 341 , the coupled signal peak hold module 342 and the A/D sampling module 343 process the sine wave coupled signals with the first, second and third frequencies in a time-division manner.

Specifically, the coupling signal amplifying module 341 amplifies the collected weak sine wave coupling signals of the first, second and third frequencies.

Specifically, the coupling signal peak holding module 342 holds the peak values of the sine wave coupling signals of the first, second and third frequencies.

Specifically, the A/D sampling module 343 performs analog-to-digital conversion on the peak values of the sine wave coupling signals of the first, second and third frequencies, and the converted digital signals are sent to the processor 320 .

The device provided in this embodiment, wherein,

The processor 320 is configured to perform operations of calculating voltage values corresponding to coupling signals of different frequencies and calculating conductivity using voltage values corresponding to coupling signals of different frequencies, specifically including:

The calculation of the voltage values corresponding to the coupling signals of different frequencies specifically includes:

calculating first, second and third voltage values corresponding to peak values of the sine wave coupling signals of the first, second and third frequencies;

The calculation of the conductivity using the voltage values corresponding to the coupling signals of different frequencies specifically includes:

The equivalent resistance Rx is calculated using the first, second and third voltage values, and then converted into the conductivity of the liquid 300 .

The model of the indirect method conductivity measurement comprises the common influence of electrode, insulating spacer and water body, and the model of the indirect method conductivity measurement that the present embodiment adopts is as shown in Figure 2, wherein,

Cy is the equivalent capacitance generated between the conductive layers of the two electrodes, Cx is the equivalent capacitance formed between the conductive layers of the two electrodes and the measured liquid, and Rx is the equivalent resistance of the measured liquid. The equivalent impedance model between two electrodes is shown in formula (1).

………………..Formula 1)

Transform the formula (1) to get the complex expression (2)

……….Formula (2)

The corresponding output impedance of the electrode output in the liquid is obtained by the modulo operation of formula (2) , in order to solve Rx, Cy, Cx at this time, it is only necessary to select three suitable sine wave excitation signals, that is, the sine wave excitation signals of the first, second and third frequencies, and obtain the same frequency as the first, second and third The first, second and third voltage values corresponding to the peak values of the frequency sine wave coupling signal can be solved for corresponding parameters.

The device provided in this embodiment, wherein,

The processor 320 is configured to perform an operation of calculating the equivalent resistance Rx by using the first, second and third voltage values, and then converting it into the conductivity of the liquid 300, specifically including:

Use the temperature measurement module 360 to obtain the temperature value of the liquid 300;

The normalized equivalent conductivity of the liquid 300 is solved for using the temperature value of the liquid 300 .

The normalized equivalent conductivity calculation relationship is as follows:

Conductivity value at 25 degrees = actual conductivity value/(1+0.02*(t-25));

Among them, 0.02 is the temperature compensation coefficient; t is the actual water temperature.

The device given in this embodiment also includes a temperature measurement module 360, specifically,

The temperature sensor contained in the temperature measurement module 360 is not directly placed in the liquid to be measured. The temperature sensor contained in the temperature measurement module 360 uses a good heat conductor as a heat conduction channel and as a watertight component to reduce the complexity of the watertight structure.

Specifically, the temperature sensor contained in the temperature measurement module 360 uses a good thermal conductor as a heat conduction channel and as a watertight component. A specific implementation is to place the temperature sensor contained in the temperature measurement module 360 on the rear side of the electrode A 310 or electrode B 311, Using the electrode A 310 or the electrode B 311 can achieve two effects of water tightness and heat conduction.

The device given in this embodiment also includes a communication module 350, specifically,

The communication module 350 is electrically connected to the processor 320 and is electrically or radio connected to a network-side communication node.

Specifically, the communication module 350 obtains control commands from the network-side communication node or sends measurement results to the network-side communication node through its electrical connection or radio connection with the processor 320 and the network-side communication node.

Preferably, there is a radio connection between the communication module 350 and a communication node on the network side, and the radio connection is a radio connection complying with the LoRa communication protocol or the NB-IOT communication protocol.

The methods and devices provided in the embodiments of the present invention can be implemented in whole or in part using electronic technology, radio transmission technology and Internet technology; the methods provided in the embodiments of the present invention can be realized in whole or in part through software instructions and/or hardware circuits; The modules or units included in the device provided in the embodiments of the present invention may be realized by using electronic components.

The above descriptions are only preferred implementations of the present invention, and are not intended to limit the protection scope of the present invention. Anyone skilled in the field of the present invention, without departing from the spirit and scope disclosed by the present invention, can make any modifications and changes in the form and details of the implementation, but the protection scope of the present invention is defined in the appended The defined scope of the claims shall prevail.

The method and device provided by the present invention overcome at least one of the shortcomings of the existing conductivity measurement technology that the conductivity measurement electrode is easy to corrode, the conductivity measurement accuracy is affected by the deposit on the electrode surface, and the water temperature measurement increases the complexity of the watertight structure. kind. Low cost and practical.

Claims (12)

1. A method of measuring the conductivity of a liquid, comprising the steps of:

step S110, sending sine wave excitation signals with different frequencies to the electrode a 310;

step S120, receiving coupling signals with different frequencies from the electrode B311;

step S130, calculating voltage values corresponding to the coupling signals with different frequencies;

in step S140, the electrical conductivity is calculated by using the voltage values corresponding to the coupling signals with different frequencies.

2. The method of claim 1, wherein,

the sending of sine wave excitation signals with different frequencies to the electrode a310 includes:

the processor 320 controls the excitation signal generation module 330 to generate sine wave signals having first, second and third frequencies, which are sent to the electrode a310 through the excitation signal amplification module 331, and the electrode a310 injects the sine wave signals received by the electrode a into the liquid 300.

3. The method of claim 1, wherein,

the receiving of the coupled signals with different frequencies from the electrode B311 includes:

the processor 320 receives the sine wave coupling signal having the first, second and third frequencies, which is the serial voltage division of the equivalent resistance of water and the sampling resistance, through the receiving channel module 390 and the receiving electrode B311.

4. The method of claim 1, wherein,

the calculating the voltage values corresponding to the coupling signals with different frequencies specifically includes:

calculating first, second and third voltage values corresponding to peak values of the sine wave coupling signals of the first, second and third frequencies;

the calculating the conductivity by using the voltage values corresponding to the coupling signals with different frequencies specifically includes:

the equivalent resistance Rx is calculated using the first, second and third voltage values and then converted into the conductivity of the liquid 300.

5. The method of claim 4, wherein,

the calculating the equivalent resistance Rx using the first, second, and third voltage values, and then converting into the conductivity of the liquid 300 specifically includes:

obtaining temperature values of the liquid 300 using the temperature measurement module 360

The normalized equivalent conductivity of the liquid 300 is solved using the temperature value of the liquid 300.

6. A liquid conductivity measurement device comprising:

excitation channel module 380, electrode a310, receive channel module 390, electrode B311, and processor 320; wherein,

the excitation channel module 380 is used for sending sine wave excitation signals with different frequencies to the electrode a310, and comprises an excitation signal generation module 330 and an excitation signal amplification module 331;

an electrode a310 for injecting sine wave excitation signals of different frequencies into the liquid 300, comprising a metal conductor;

a receiving channel module 390 for receiving the coupled signals with different frequencies from the electrode B311, comprising a coupled signal sampling module 340, a coupled signal amplifying module 341, a coupled signal peak holding module 342, and an A/D sampling module 343;

the electrode B311 is used for detecting coupling signals of the liquid 300 to sine wave excitation signals with different frequencies and comprises a metal conductor;

the processor 320 is configured to calculate voltage values corresponding to the coupling signals with different frequencies, and calculate the conductivity using the voltage values, and includes an arithmetic unit, a memory unit, and a peripheral interface circuit.

7. The apparatus of claim 6, wherein,

the excitation channel module 380 is configured to perform an operation of sending sine wave excitation signals with different frequencies to the electrode a310, and specifically includes the following operation steps:

the processor 320 controls the excitation signal generation module 330 to generate sine wave signals having first, second and third frequencies, which are sent to the electrode a310 through the excitation signal amplification module 331, and the electrode a310 injects the sine wave signals received by the electrode a into the liquid 300.

8. The apparatus of claim 6, wherein,

the receiving channel module 390 is configured to perform an operation of receiving the coupled signals with different frequencies from the electrode B311, and specifically includes the following operation steps:

the processor 320 receives the sine wave coupling signal having the first, second and third frequencies, which is the serial voltage division of the equivalent resistance of water and the sampling resistance, through the receiving channel module 390 and the receiving electrode B311.

9. The apparatus of claim 6, wherein,

the processor 320 is configured to perform operations of calculating voltage values corresponding to the coupling signals with different frequencies and calculating electrical conductivity by using the voltage values corresponding to the coupling signals with different frequencies, and specifically includes:

the calculating the voltage values corresponding to the coupling signals with different frequencies specifically includes:

calculating first, second and third voltage values corresponding to peak values of the sine wave coupling signals of the first, second and third frequencies;

the calculating the conductivity by using the voltage values corresponding to the coupling signals with different frequencies specifically includes:

the equivalent resistance Rx is calculated using the first, second and third voltage values and then converted into the conductivity of the liquid 300.

10. The apparatus of claim 9, wherein,

a processor 320, configured to perform an operation of calculating an equivalent resistance Rx using the first, second, and third voltage values, and then converting the calculated equivalent resistance Rx into the conductivity of the liquid 300, specifically including:

acquiring a temperature value of the liquid 300 by using a temperature measuring module 360;

the normalized equivalent conductivity of the liquid 300 is solved using the temperature value of the liquid 300.

11. The apparatus of claim 6, further comprising a thermometry module 360, in particular,

the temperature sensor included in the temperature measurement module 360 is not directly placed in the measured liquid, and the temperature sensor included in the temperature measurement module 360 utilizes a good heat conductor as a heat conduction channel and as a watertight component to reduce the complexity of the watertight structure.

12. The apparatus according to claim 6, further comprising a communication module 350, in particular,

the communication module 350 is electrically connected to the processor 320 and electrically connected or wirelessly connected to a communication node on the network side.