Aqueous solution conductivity monitor

Abstract

The invention discloses an aqueous solution conductivity monitor, which comprises a main processor, a conductivity acquisition circuit, a display unit and a square wave excitation circuit, and is characterized in that the conductivity acquisition circuit, the display unit and the square wave excitation circuit are respectively connected with the main processor; the square wave excitation circuit comprises a power conversion circuit, a square wave control circuit, a square wave amplitude switching circuit and a current amplification circuit which are connected in sequence; the conductivity acquisition circuit is connected to a conductivity electrode, and the conductivity electrode is connected with the current amplification circuit. According to the aqueous solution conductivity monitor, based on the arrangement of the square wave excitation circuit, the frequency and amplitude of the square wave voltage signal of the square wave excitation circuit can be controlled through a program of the main processor, and the aqueous solution conductivity monitor has a variable frequency adjustment function, so that conductivity online monitoring can be switched back and forth in different frequency bands; according to the invention, other measured pulse signals can be effectively distinguished, and the polarization effect of the conductivity electrode can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of industrial aqueous solution conductivity measuring equipment, in particular to an aqueous solution conductivity monitor. Background Art

[0002] The conductivity of aqueous solutions is usually measured using conductivity electrodes and matching conductivity measuring instruments. During the measurement process, direct current or alternating current is connected to the parallel plates of the conductivity electrodes, and a potential difference is applied to the aqueous solution, causing the ions in the aqueous solution to move under the action of the electric field, forming a current. The conductivity electrodes are then used to measure the current and potential difference in the solution, and the conductivity is calculated.

[0003] Most of the existing conductivity measuring instruments use sine wave AC signals for measurement. When measuring sine wave AC signals, the output power is small, the compatibility with digital circuits is poor, the circuit requirements are high, and a large investment is required. In addition, the electrode surface through which the current passes is prone to polarization. After the electrode is polarized, the electrode potential deviates from its equilibrium potential, which will cause serious errors in the measurement. In order to slow down the polarization of the conductivity electrode, the polarization effect can often be reduced by increasing the effective area of ​​the electrode, increasing the electrode spacing, and adding coatings. However, once the electrode is selected, the difficulty of adjusting the effective area of ​​the electrode, the electrode spacing, and adding coatings are usually large, and the effect is low. Summary of the invention

[0004] The object of the present invention is to provide an aqueous solution conductivity monitor.

[0005] The technical solution for achieving the purpose of the present invention is: an aqueous solution conductivity monitor, comprising a main processor, a conductivity acquisition circuit, a display unit and a square wave excitation circuit, wherein the conductivity acquisition circuit and the display unit are each connected to the main processor, the square wave excitation circuit comprises a power conversion circuit, a square wave control circuit, a square wave amplitude switching circuit and a current amplification circuit, the square wave control circuit comprises an electronic switch U2, the square wave amplitude switching circuit comprises a voltage divider circuit and an electronic switch U3, the power conversion circuit, the electronic switch U2 of the square wave control circuit, the voltage divider circuit of the square wave amplitude switching circuit, the electronic switch U3 and the current amplification circuit are connected in sequence, the control end of the electronic switch U2 is connected to the PWM interface of the main processor, and the control end of the electronic switch U3 is connected to the IO port of the main processor; the conductivity acquisition circuit is connected to a conductivity electrode, and the conductivity electrode is connected to the current amplification circuit of the square wave excitation circuit.

[0006] Further, the voltage divider circuit is a three-stage voltage divider circuit. Specifically, the voltage divider circuit is composed of a resistor R3, a resistor R8 and a resistor R7, and the front ends of the resistors R3, R8 and R7 are respectively connected to the input end of the electronic switch U3. The voltage divider circuit can be a two-stage voltage divider circuit or a multi-stage voltage divider circuit. For simplicity of use, preferably, the voltage divider circuit is a three-stage voltage divider circuit.

[0007] Furthermore, the electronic switch U2 and the electronic switch U3 are both high-speed electronic switch chips. High-speed electronic switch chips not only have low power consumption, but also can perform fast and high-precision switch control to ensure the stability and reliability of the circuit.

[0008] Furthermore, it also includes a temperature compensation circuit, which is connected to the main processor. The temperature compensation circuit is mainly composed of an acquisition circuit of a temperature sensor, and is used in conjunction with the temperature sensor provided by the user to set corresponding temperature compensation parameters. When working, the temperature compensation circuit acquires the temperature signal of the aqueous solution in real time, and sends the acquired temperature signal of the aqueous solution to the main processor, and the main processor compensates the detection result according to the temperature signal acquired by the temperature compensation circuit. Preferably, the temperature compensation circuit includes acquisition circuits of two temperature sensors, PT100 and NTC10K, to increase the scope of application.

[0009] Furthermore, it also includes an analog output circuit, which is connected to the main processor. The analog output circuit is used to output the measured values ​​such as conductivity in the form of analog signals such as 0-20mA or 4-20mA or 0-5V or 1-5V, such as outputting them to external devices for synchronous monitoring. Specifically, the analog output circuit uses an operational amplifier to receive the PWM frequency signal of the main processor, and amplifies the current through a transistor to increase the driving capacity. When in use, according to the PWM frequency signal of the main processor, the analog output circuit generates analog signals such as 0-20mA or 4-20mA or 0-5V or 1-5V. The setting of the analog output circuit increases the function of the aqueous solution conductivity monitor, so that the aqueous solution conductivity monitor can be easily linked with external devices for synchronous monitoring.

[0010] Furthermore, it also includes a communication circuit, which is connected to the main processor. The communication circuit is used to form a remote communication network with external devices. Considering the application of the aqueous solution conductivity monitor, preferably, the communication circuit is a 485 communication circuit, which is connected to the serial port of the main processor and provides a 485 output interface, and the communication protocol used is the standard modbus rtu protocol.

[0011] Furthermore, it also includes an alarm circuit, which is connected to the main processor. The alarm circuit is used to receive a control signal from the main processor and send an alarm signal according to the online status of the conductivity. Preferably, the alarm circuit is a buzzer alarm circuit.

[0012] Furthermore, the main processor is a processor with a built-in 32-bit timer. The main processor with a built-in 32-bit timer can generate a 2HZ-10KHZ PWM frequency signal, which performs frequency conversion control on the square wave excitation circuit, and its cost is relatively low while meeting application requirements.

[0013] Furthermore, the conductivity acquisition circuit includes a rectifier circuit and an AD conversion circuit connected to each other. The rectifier circuit is used to receive the square wave signal fed back by the conductivity electrode and rectify the recovered square wave signal into a linear voltage acquisition signal, after which the voltage acquisition signal is transmitted to the AD conversion circuit; the AD conversion circuit is used to convert the analog voltage acquisition signal into a digital signal for the main processor to collect and convert the real-time conductivity value.

[0014] Furthermore, the display unit is an LCD display screen. The LCD display screen can not only display interactively, but also set the electrode constant, range, and display unit, etc. The present invention has less display content and low operation requirements. Under the condition of meeting the requirements of display and operation, the cost of the LCD display screen is lower than that of the LED display screen.

[0015] The aqueous solution conductivity monitor of the present invention, through the setting of the square wave control circuit in the square wave excitation circuit, can, after being connected to the main processor, utilize the PWM frequency signal of the main processor to not only control the square wave excitation circuit to generate a square wave voltage signal and provide a square wave voltage signal for the conductivity electrode, but also can adjust the frequency of the square wave voltage signal generated by the square wave excitation circuit through the frequency control of the PWM frequency signal of the main processor, so that the frequency of the square wave voltage signal applied to the conductivity electrode can be adjusted.

[0016] The aqueous solution conductivity monitor of the present invention provides a square wave voltage signal for the conductivity electrode, and measures the conductivity of the aqueous solution through the square wave voltage signal. The square wave voltage signal will produce rapid voltage changes at the rising and falling edges. This rapid change will excite the inductance and capacitance elements in the circuit, thereby generating a freely decaying oscillation signal. This freely decaying oscillation signal contains high-frequency components. The signal within a specific frequency range can be retained by a bandpass filter, thereby improving the signal-to-noise ratio of the response signal; and the high-frequency components of the oscillation signal can also be used for high-sensitivity detection. In the conductivity measurement of the present invention, by measuring the freely decaying frequency at the falling edge of the square wave, The first peak voltage of the oscillation signal can realize high-precision conductivity measurement. This detection method is more sensitive to small changes and has high detection sensitivity. In addition, the high-frequency component of the oscillation signal can be effectively amplified by the amplifier, thereby achieving a higher output power and a larger output power. In addition, the square wave signal is a commonly used signal form in digital circuits, with clear high and low levels and fast edge changes. The freely decaying oscillation signal in the square wave signal can be processed by a simple digital circuit (such as filtering, shaping, etc.) and is compatible with the digital circuit. In addition, the high-frequency component of the oscillation signal can be used for digital signal processing to further improve the performance of the digital circuit. In other words, compared with the sine wave AC signal, the present invention provides a square wave voltage signal for the conductivity electrode, which can improve the signal-to-noise ratio of the response signal, and has the advantages of higher sensitivity, large output power, and good compatibility with digital circuits.

[0017] The aqueous solution conductivity monitor of the present invention has a square wave voltage signal whose frequency provided to the conductivity electrode is not only adjustable but also flexibly adjustable. When the square wave voltage signal frequency is flexibly adjustable, on the one hand, the square wave voltage signal applied to the conductivity electrode can be conveniently adjusted to a high frequency, so that under the high-frequency square wave voltage signal, the oxidation reaction (losing electrons) and the reduction reaction (gaining electrons) on the surface of the conductivity electrode are alternately performed, and this alternating reaction reduces the charge accumulation on the surface of the conductivity electrode, thereby reducing the polarization effect; on the other hand, during the process of the conductivity electrode performing online monitoring of the aqueous solution conductivity, if other situations such as the frequency type flow meter measuring the flow rate are encountered, the frequency of the square wave voltage signal applied to the conductivity electrode can be switched back and forth to effectively distinguish the pulse signal of the frequency type flow meter measuring the flow rate, avoid mutual interference with the pulse signal of the frequency type flow meter measuring the flow rate, and thus make the detection of the aqueous solution conductivity monitor of the present invention more accurate and stable.

[0018] The water solution conductivity monitor of the present invention has a square wave voltage signal generated by the square wave excitation circuit, which has high adjustment flexibility and strong adaptability and can be applied to detection in various occasions. At the same time, when controlled by the PWM frequency signal of the main processor, it can be operated on the main processor, and its adjustment operation is convenient.

[0019] The aqueous solution conductivity monitor of the present invention applies a high-frequency square wave voltage signal to the conductivity electrode by adjusting the frequency of the square wave voltage signal applied to the conductivity electrode. The polarization effect of the conductivity electrode is reduced by alternating oxidation and reduction on the surface of the conductivity electrode under the high-frequency square wave voltage signal. Compared with the existing method of reducing the polarization effect by increasing the effective area of ​​the electrode, increasing the electrode spacing, adding a coating, etc., the monitor has high operability, is simple to operate, easy to implement, and more effective.

[0020] In addition, the aqueous solution conductivity monitor of the present invention also uses the ingenious design of the square wave amplitude switching circuit in the square wave excitation circuit, including the voltage divider circuit and the electronic switch U3, so that the amplitude of the square wave voltage signal generated by the square wave excitation circuit can be adjusted and switched by the main processor through the gating control of the electronic switch U3. In this way, it can be compatible with the conductivity electrodes with different constants, greatly improving the adaptability of the aqueous solution conductivity monitor of the present invention and making the application range of the aqueous solution conductivity monitor of the present invention wider.

[0021] The aqueous solution conductivity monitor of the present invention, based on the setting of the square wave excitation circuit, controls the square wave excitation circuit to generate and provide a square wave voltage signal for the conductivity electrode through the program of the main processor, so that under the input of the square wave voltage signal, the signal-to-noise ratio of the response signal can be improved, and has the advantages of higher sensitivity, large output power, and good compatibility with digital circuits. At the same time, the frequency and amplitude of the square wave voltage signal of the square wave excitation circuit can also be controlled by the program of the main processor, and the function of variable frequency regulation can be provided, so that the online monitoring of conductivity can be switched back and forth in different frequency bands, which can not only effectively distinguish the pulse signal of the frequency type flowmeter measuring the flow rate, avoid mutual interference with the pulse signal of the frequency type flowmeter measuring the flow rate, and make the detection of the aqueous solution conductivity and the measurement process of other frequency type flowmeters more stable; it can also reduce the polarization effect of the conductivity electrode and reduce the measurement error caused by the polarization of the conductivity electrode. The aqueous solution conductivity monitor of the present invention takes into account the influence of the input signal, polarization efficiency and signal interference of the conductivity electrode on the measurement result, and finally makes the measurement result of conductivity more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a functional structure diagram of the aqueous solution conductivity monitor of the present invention; Figure 2 The present invention discloses a circuit diagram of a square wave excitation circuit of a networking system of an aqueous solution conductivity monitor. DETAILED DESCRIPTION

[0023] The preferred embodiment of the aqueous solution conductivity monitor of the present invention is described in detail below in conjunction with the accompanying drawings: like Figure 1 and Figure 2 As shown, an aqueous solution conductivity monitor includes a main processor 1, a conductivity acquisition circuit 2, a display unit 3 and a square wave excitation circuit 4, wherein the conductivity acquisition circuit 2 and the display unit 3 are each connected to the main processor 1, the square wave excitation circuit 4 includes a power conversion circuit 41, a square wave control circuit 42, a square wave amplitude switching circuit 43 and a current amplification circuit 44, the square wave control circuit 42 includes an electronic switch U2, the square wave amplitude switching circuit 43 includes a voltage divider circuit 431 and an electronic switch U3, the power conversion circuit The circuit 41, the electronic switch U2 of the square wave control circuit 42, the voltage divider circuit 431 of the square wave amplitude switching circuit 43, the electronic switch U3 and the current amplifier circuit 44 are connected in sequence, the control end of the electronic switch U2 is connected to the PWM interface of the main processor 1, and the control end of the electronic switch U3 is connected to the IO port of the main processor 1; the conductivity acquisition circuit 2 is connected to the conductivity electrode 10, and the conductivity electrode 10 is connected to the current amplifier circuit 44 of the square wave excitation circuit 4.

[0024] In the aqueous solution conductivity monitor of the present invention, the conductivity acquisition circuit 2 is connected to the conductivity electrode 10, and is used to receive the square wave signal fed back by the conductivity electrode 10, and collect the square wave signal fed back by the conductivity electrode 10, collect the conductivity signal, and transmit the collected conductivity signal to the main processor 1. The main processor 1 is used to receive the conductivity signal collected by the conductivity acquisition circuit 2, and process the collected conductivity signal such as conversion to obtain the conductivity measurement value; and to send the conductivity measurement value to the display unit 3 for display; and to send a PWM frequency signal to the electronic switch U2 of the square wave control circuit 42 through the PWM interface of the main processor 1 to perform frequency conversion control on the square wave excitation circuit 4; and to send a selection signal through the IO port to control the inlet voltage of the electronic switch U3 and switch the amplitude of the square wave voltage signal.

[0025] In the aqueous solution conductivity monitor of the present invention, in the square wave excitation circuit 4, the power conversion circuit 41 mainly includes a power chip for converting the power supply voltage, such as converting the ±5V of the power supply voltage to ±2V; in the square wave control circuit 42, after the control end of the electronic switch U2 is connected to the PWM interface of the main processor 1, the PWM frequency signal sent by the PWM interface of the main processor 1 is received. Under the control of the PWM frequency signal, the electronic switch U2 continuously switches its input voltage to output a positive and negative alternating square wave voltage signal; in the square wave amplitude switching circuit 43, the control end of the electronic switch U3 is connected to the IO port ( Figure 2The electrical conductivity electrode 10 is connected to the electrical conductivity electrode 10 (marked as IO1, IO2), receives the selection signal from the main processor 1, is used to control the input voltage of the electronic switch U3, and switches the amplitude of the square wave voltage signal; the current amplifier circuit 44 is used to perform pre-current amplification on the square wave voltage signal and output it to the electrical conductivity electrode 10 as the power supply of the electrical conductivity electrode 10.

[0026] The aqueous solution conductivity monitor of the present invention, when in use, the square wave excitation circuit 4 applies a square wave voltage signal to the conductivity electrode 10, under which the ions in the aqueous solution move to form a current; the conductivity electrode 10 feeds back the square wave signal recovered from the aqueous solution, and sends the recovered square wave signal to the conductivity acquisition circuit 2; the conductivity acquisition circuit 2 collects the square wave signal fed back by the conductivity electrode 10, and transmits the collected conductivity signal to the main processor 1; the main processor 1 converts the conductivity signal collected by the conductivity acquisition circuit 2 to obtain a conductivity measurement value, and sends it to the display unit 3 for display, thereby realizing the detection of the conductivity of the aqueous solution. The aqueous solution conductivity monitor of the present invention detects the conductivity of the aqueous solution in real time, and can complete the online monitoring of the conductivity of the aqueous solution.

[0027] The aqueous solution conductivity monitor of the present invention can control the frequency and amplitude of the square wave voltage signal output by the square wave excitation circuit 4 and applied to the conductivity electrode 10 through the main processor 1 when detecting the conductivity of the aqueous solution. Specifically, the PWM frequency signal is sent to the electronic switch U2 of the square wave control circuit 42 through the PWM interface of the main processor 1. Under the control of the PWM frequency signal, the electronic switch U2 continuously switches its input voltage, which can not only generate a positive and negative alternating square wave voltage signal, but also adjust the frequency of the generated positive and negative alternating square wave voltage signal through the frequency of the PWM frequency signal, thereby performing frequency conversion control on the square wave excitation circuit 4. The main processor 1 sends a selection signal to control the input voltage of the voltage divider circuit 431 connected to the electronic switch U3, and the amplitude of the square wave voltage signal can be switched.

[0028] The aqueous solution conductivity monitor of the present invention, through the setting of the square wave control circuit 42 in the square wave excitation circuit 4, can, after being connected to the main processor 1, utilize the PWM frequency signal of the main processor 1 to not only control the square wave excitation circuit 4 to generate a square wave voltage signal and provide a square wave voltage signal for the conductivity electrode 10, but also can adjust the frequency of the square wave voltage signal generated by the square wave excitation circuit 4 through the frequency control of the PWM frequency signal of the main processor 1, so that the frequency of the square wave voltage signal applied to the conductivity electrode 10 can be adjusted.

[0029] The aqueous solution conductivity monitor of the present invention provides a square wave voltage signal for the conductivity electrode 10, and measures the conductivity of the aqueous solution through the square wave voltage signal. The square wave voltage signal will produce rapid voltage changes at the rising and falling edges. This rapid change will excite the inductance and capacitance elements in the circuit, thereby generating a freely decaying oscillation signal. This freely decaying oscillation signal contains high-frequency components. The signal within a specific frequency range can be retained by a bandpass filter, thereby improving the signal-to-noise ratio of the response signal; and the high-frequency components of the oscillation signal can also be used for high-sensitivity detection. In the conductivity measurement of the present invention, by measuring the freely decaying frequency at the falling edge of the square wave, The first peak voltage of the oscillation signal can be reduced to achieve high-precision conductivity measurement. This detection method is more sensitive to small changes and has high detection sensitivity. The high-frequency component of the oscillation signal can be effectively amplified by the amplifier, thereby achieving a higher output power and a larger output power. In addition, the square wave signal is a commonly used signal form in digital circuits, with clear high and low levels and fast edge changes. The freely decaying oscillation signal in the square wave signal can be processed by a simple digital circuit (such as filtering, shaping, etc.) and is compatible with the digital circuit. In addition, the high-frequency component of the oscillation signal can be used for digital signal processing to further improve the performance of the digital circuit. In other words, compared with the sine wave AC signal, the present invention provides the conductivity electrode 10 with a square wave voltage signal, which can improve the signal-to-noise ratio of the response signal and has the advantages of higher sensitivity, large output power, and good compatibility with digital circuits.

[0030] In the aqueous solution conductivity monitor of the present invention, the frequency of the square wave voltage signal provided to the conductivity electrode 10 is not only adjustable, but also flexibly adjustable. When the frequency of the square wave voltage signal is flexibly adjustable, on the one hand, the square wave voltage signal applied to the conductivity electrode 10 can be conveniently adjusted to a high frequency, so that under the high-frequency square wave voltage signal, the oxidation reaction (losing electrons) and the reduction reaction (gaining electrons) on the surface of the conductivity electrode 10 are alternately performed, and this alternating reaction reduces the charge accumulation on the surface of the conductivity electrode 10, thereby reducing the polarization effect; on the other hand, during the process of the conductivity electrode 10 performing online monitoring of the aqueous solution conductivity, if other situations such as the frequency type flow meter measuring the flow rate are encountered, the frequency of the square wave voltage signal applied to the conductivity electrode 10 can also be switched back and forth to effectively distinguish the pulse signal of the frequency type flow meter measuring the flow rate, avoid mutual interference with the pulse signal of the frequency type flow meter measuring the flow rate, and thus make the detection of the aqueous solution conductivity monitor of the present invention more accurate and stable.

[0031] In the aqueous solution conductivity monitor of the present invention, the square wave voltage signal generated by the square wave excitation circuit 4 has high adjustment flexibility and strong adaptability, and can be applied to detection in various occasions. At the same time, when controlled by the PWM frequency signal of the main processor 1, it can be operated on the main processor 1, and its adjustment operation is convenient.

[0032] The aqueous solution conductivity monitor of the present invention applies a high-frequency square wave voltage signal to the conductivity electrode 10 by adjusting the frequency of the square wave voltage signal applied to the conductivity electrode 10. The surface of the conductivity electrode 10 is alternately oxidized and reduced under the high-frequency square wave voltage signal to reduce the polarization effect of the conductivity electrode 10. Compared with the existing method of reducing the polarization effect by increasing the effective area of ​​the electrode, increasing the electrode spacing, adding a coating, etc., the method has high operability, is simple to operate, easy to implement, and has higher efficiency.

[0033] In addition, the aqueous solution conductivity monitor of the present invention also uses the ingenious design of the square wave amplitude switching circuit 43 in the square wave excitation circuit 4, including the voltage divider circuit 431 and the electronic switch U3, so that the amplitude of the square wave voltage signal generated by the square wave excitation circuit 4 can be adjusted and switched by the main processor 1 through the gating control of the electronic switch U3. In this way, it can be compatible with the conductivity electrodes 10 with different constants, greatly improving the adaptability of the aqueous solution conductivity monitor of the present invention and making the application range of the aqueous solution conductivity monitor of the present invention wider.

[0034] The aqueous solution conductivity monitor of the present invention, based on the setting of the square wave excitation circuit 4, controls the square wave excitation circuit 4 to generate and provide a square wave voltage signal for the conductivity electrode 10 through the program of the main processor 1, so that under the input of the square wave voltage signal, the signal-to-noise ratio of the response signal can be improved, and has the advantages of higher sensitivity, large output power, good compatibility with digital circuits, etc. At the same time, the frequency and amplitude of the square wave voltage signal of the square wave excitation circuit 4 can also be controlled by the program of the main processor 1, and the function of variable frequency regulation can be provided, so that the online monitoring of conductivity can be switched back and forth in different frequency bands, which can not only effectively distinguish the pulse signal of the frequency type flowmeter measuring the flow rate, avoid mutual interference with the pulse signal of the frequency type flowmeter measuring the flow rate, and make the detection of the aqueous solution conductivity and the measurement process of other frequency type flowmeters more stable; it can also reduce the polarization effect of the conductivity electrode 10, and reduce the measurement error caused by the polarization of the conductivity electrode 10. The aqueous solution conductivity monitor of the present invention takes into account the influence of the input signal, polarization efficiency and signal interference of the conductivity electrode 10 on the measurement result, and ultimately makes the measurement result of the conductivity more accurate.

[0035] In the aqueous solution conductivity monitor of the present invention, preferably, the voltage divider circuit 431 is a three-stage voltage divider circuit. Specifically, the voltage divider circuit 431 is composed of a resistor R3, a resistor R8 and a resistor R7, and the front ends of the resistors R3, R8 and R7 are respectively connected to the input end of the electronic switch U3. The voltage divider circuit 431 can be a two-stage voltage divider circuit or a multi-stage voltage divider circuit. In order to simplify the use, preferably, the voltage divider circuit 431 is a three-stage voltage divider circuit.

[0036] In the aqueous solution conductivity monitor of the present invention, preferably, the electronic switch U2 and the electronic switch U3 are both high-speed electronic switch chips. High-speed electronic switch chips not only have low power consumption, but also can perform fast and high-precision switch control to ensure the stability and reliability of the circuit.

[0037] The aqueous solution conductivity monitor of the present invention preferably further includes a temperature compensation circuit 5, and the temperature compensation circuit 5 is connected to the main processor 1. The temperature compensation circuit 5 is mainly composed of an acquisition circuit of a temperature sensor, and is used in conjunction with the temperature sensor provided by the user to set corresponding temperature compensation parameters. When working, the temperature compensation circuit 5 acquires the temperature signal of the aqueous solution in real time, and sends the acquired temperature signal of the aqueous solution to the main processor 1. The main processor 1 compensates the detection result according to the temperature signal acquired by the temperature compensation circuit 5, avoids the influence of different temperatures of the aqueous solution on the detection result, and makes the detection of the conductivity of the aqueous solution more accurate. Preferably, the temperature compensation circuit 5 includes acquisition circuits of two temperature sensors, PT100 and NTC10K, to improve the scope of application.

[0038] The aqueous solution conductivity monitor of the present invention preferably further includes an analog output circuit 6, which is connected to the main processor 1. The analog output circuit 6 is used to output the measured values ​​such as conductivity in the form of analog signals such as 0-20mA or 4-20mA or 0-5V or 1-5V, such as outputting them to an external device for synchronous monitoring. Specifically, the analog output circuit 6 uses an operational amplifier to receive the PWM frequency signal of the main processor 1, and amplifies the current through a transistor to increase the driving capacity. When in use, according to the PWM frequency signal of the main processor 1, the analog output circuit 6 generates analog signals such as 0-20mA or 4-20mA or 0-5V or 1-5V. The setting of the analog output circuit 6 increases the function of the aqueous solution conductivity monitor, so that the aqueous solution conductivity monitor can be conveniently linked with external devices for synchronous monitoring.

[0039] The aqueous solution conductivity monitor of the present invention preferably further comprises a communication circuit 7, and the communication circuit 7 is connected to the main processor 1. The communication circuit 7 is used to form a remote communication network with external devices. Considering the application of the aqueous solution conductivity monitor, preferably, the communication circuit 7 is a 485 communication circuit, the communication circuit 7 is connected to the serial port of the main processor 1, and provides a 485 output interface, and the communication protocol adopted is the standard modbus rtu protocol.

[0040] The aqueous solution conductivity monitor of the present invention preferably further comprises an alarm circuit 8, which is connected to the main processor 1. The alarm circuit 8 is used to receive a control signal from the main processor 1 and issue an alarm signal according to the online status of the conductivity. Preferably, the alarm circuit 8 is a buzzer alarm circuit.

[0041] In the aqueous solution conductivity monitor of the present invention, preferably, the main processor 1 is a processor with a built-in 32-bit timer. The main processor 1 with a built-in 32-bit timer can generate a 2HZ-10KHZPWM frequency signal, which performs frequency conversion control on the square wave excitation circuit 4, and its cost is relatively low while meeting the application requirements.

[0042] In the aqueous solution conductivity monitor of the present invention, preferably, the conductivity acquisition circuit 2 includes a rectifier circuit 21 and an AD conversion circuit 22 connected to each other. The rectifier circuit 21 is used to receive the square wave signal fed back by the conductivity electrode 10, and rectify the recovered square wave signal into a linear voltage acquisition signal, after which the voltage acquisition signal is transmitted to the AD conversion circuit 22; the AD conversion circuit 22 is used to convert the analog voltage acquisition signal into a digital signal for the main processor to collect and convert the real-time conductivity value.

[0043] In the aqueous solution conductivity monitor of the present invention, preferably, the display unit 3 is an LCD display screen. The LCD display screen can not only display interactively, but also set the electrode constant, range, and display unit, etc. The present invention has less display content and low operation requirements. Under the condition of meeting the requirements of display, operation, etc., the cost of the LCD display screen is lower than that of the LED display screen.

[0044] In the aqueous solution conductivity monitor of the present invention, the power conversion circuit 41 is composed of a power chip, and the current amplifier circuit 44 is composed of an operational amplifier. The structures of the power conversion circuit 41 and the current amplifier circuit 44 are both existing structures, and the present invention will not elaborate on this.

[0045] For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A water solution conductivity monitor, characterized in that: The invention comprises a main processor, a conductivity acquisition circuit, a display unit and a square wave excitation circuit. The conductivity acquisition circuit and the display unit are respectively connected to the main processor. The square wave excitation circuit comprises a power conversion circuit, a square wave control circuit, a square wave amplitude switching circuit and a current amplification circuit. The square wave control circuit comprises an electronic switch U2. The square wave amplitude switching circuit comprises a voltage divider circuit and an electronic switch U3. The power conversion circuit, the electronic switch U2 of the square wave control circuit, the voltage divider circuit of the square wave amplitude switching circuit, the electronic switch U3 and the current amplification circuit are connected in sequence. The control end of the electronic switch U2 is connected to the PWM interface of the main processor, and the control end of the electronic switch U3 is connected to the IO port of the main processor. The conductivity acquisition circuit is connected to a conductivity electrode, and the conductivity electrode is connected to the current amplification circuit of the square wave excitation circuit.

2. The aqueous solution conductivity monitor according to claim 1, characterized in that: The voltage divider circuit is a three-stage voltage divider circuit.

3. The aqueous solution conductivity monitor according to claim 1, characterized in that: The electronic switch U2 and the electronic switch U3 are both high-speed electronic switch chips.

4. The aqueous solution conductivity monitor according to claim 1, characterized in that: A temperature compensation circuit is also included, and the temperature compensation circuit is connected to the main processor.

5. The aqueous solution conductivity monitor according to claim 1, characterized in that: It also includes an analog output circuit, which is connected to the main processor.

6. The aqueous solution conductivity monitor according to claim 1, characterized in that: It also includes a communication circuit, which is connected to the main processor.

7. The aqueous solution conductivity monitor according to claim 1, characterized in that: It also includes an alarm circuit, which is connected to the main processor.

8. The aqueous solution conductivity monitor according to claim 1, characterized in that: The main processor is a processor with a built-in 32-bit timer.

9. The aqueous solution conductivity monitor according to claim 1, characterized in that: The conductivity acquisition circuit includes a rectifier circuit and an AD conversion circuit connected to each other.

10. The aqueous solution conductivity monitor according to claim 1, characterized in that: The display unit is an LCD display screen.

Images