CN107064225B - Intelligent water quality detection system based on dual-mode self-adjustment conductivity detection - Google Patents
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Abstract
An intelligent water quality detection system based on dual-mode self-adjusting conductivity detection comprises a dual-mode self-adjusting conductivity detection circuit, a data acquisition circuit and a programmable logic array; the dual-mode self-adjusting conductivity detection circuit is used for detecting conductivity; the data acquisition circuit is connected with the dual-mode self-adjusting conductivity detection circuit to acquire the change data of the first sensor electrode and the second sensor electrode and perform analog-to-digital conversion; the programmable logic array is connected with the dual-mode self-adjusting conductivity detection circuit and the data acquisition circuit so as to compare the detected conductivity with the data after analog-to-digital conversion, and control the acquisition precision and the data conversion speed of the data acquisition circuit according to the comparison result. The invention realizes automatic conductivity detection, can eliminate the capacitance effect influence of the electrode of the conductivity sensor, overcomes the defects of detection value deviation and detection result distortion caused by the concentration of homogeneous charges on the same side electrode due to electrode polarization, and has better practical significance and higher economic value.
Description
Technical Field
The invention relates to the field of water quality detection, in particular to an intelligent water quality detection system based on dual-mode self-adjustment conductivity detection.
Background
With the continuous improvement of the economic level and the urbanization level of China, the aggravation of environmental pollution and the increasing attention of people on the problems of sewage treatment technology and control. Therefore, the status of water quality detection in modern industrial production is becoming more and more important. At present, methods for detecting water quality mainly comprise an ultraviolet absorbance method, a spectrophotometry method, a fluorescence method, a conductivity method and the like. The first three methods estimate the solute and concentration of the water quality to be measured by performing spectral absorption and refraction on the water quality, so that certain measurement precision requirements can be met. But has disadvantages of requiring manual operation in the process of detection, long detection time, complicated instrument operation, and high detection cost. At the same time, it is difficult for the user to satisfy in terms of stability, reliability, especially in terms of synchronism of measurement and measurement accuracy at medium and high concentrations. The conductivity detection method is a main method for detecting water quality in industrial production at present, and has become an important method for detecting water quality due to the advantages of stable data and simplicity and convenience. However, the traditional conductivity detection method has low precision and low intelligence degree, and the traditional conductivity detection method has the problems that due to electrode polarization, homogeneous positive or negative charges are concentrated on the same side electrode, so that the detection value is shifted, and the detection result is distorted. No relevant literature reports exist to solve the problem. Based on the above, the invention provides a real-time intelligent conductivity detection design scheme based on the polarization compensation of the electrode of the conductivity sensor of the dual-mode self-adjusting conductivity detection circuit.
In the traditional conductivity detection method, a conductivity sensor is regarded as a pure resistor, and a detected signal passes through an inverting amplification circuit formed by the conductivity sensor and a known resistor to obtain a conductivity output signal. The resistance of the conductivity sensor equivalent resistor is calculated from the inverting amplifier input and the conductivity output signal. And solving according to the equivalent resistance of the conductivity sensor to obtain a solution conductivity value. This method has two major drawbacks: (1) The traditional conductivity detection method has the problems that due to electrode polarization, homogeneous charges are concentrated on the same side electrode, so that the detection value is shifted, and the detection result is distorted. (2) The conventional conductivity detection method considers the conductivity of the solution to be detected as a constant value, which is obviously limited because the detection solution varies with the test environment, concentration and time, and thus cannot be simply considered as a constant value.
Disclosure of Invention
The invention mainly aims to overcome the defects in the prior art, and provides an intelligent water quality detection system based on dual-mode self-adjusting conductivity detection, which can automatically detect the conductivity, eliminate the capacitance effect influence of electrodes of a conductivity sensor, and overcome the defects of detection value deviation and detection result distortion caused by the fact that homogeneous charges are concentrated on the same side electrode due to electrode polarization.
The invention adopts the following technical scheme:
an intelligent water quality detection system based on dual-mode self-adjustment conductivity detection is characterized in that: the system comprises a dual-mode self-adjusting conductivity detection circuit, a data acquisition circuit and a programmable logic array; the dual-mode self-adjusting conductivity detection circuit is provided with a first sensor electrode and a second sensor electrode to detect conductivity; the data acquisition circuit is connected with the dual-mode self-adjusting conductivity detection circuit to acquire the change data of the first sensor electrode and the second sensor electrode and perform analog-to-digital conversion; the programmable logic array is connected with the dual-mode self-adjusting conductivity detection circuit and the data acquisition circuit so as to compare the detected conductivity with the data after analog-to-digital conversion, and control the acquisition precision and the data conversion speed of the data acquisition circuit according to the comparison result.
Preferably, the dual-mode self-adjusting conductivity detection circuit includes a first timer, a second timer, a first inverter, a second inverter, a first triode, a second triode, a first switch, a second switch, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a first resistor and a second resistor; the output ends of the first timer and the second timer are respectively connected with one ends of a first resistor and a second resistor, and the other ends of the first resistor and the second resistor are respectively connected with bases of a first triode and a second triode and serve as conductivity output ends; the collector electrodes of the first triode and the second triode are connected with VCC; the emitter of the first triode is connected with the discharge end of a first timer, one end of a first switch, the input end of a first reverser and one end of a first sensor electrode; the emitter of the second triode is connected with the discharge end of the second timer, one end of the second switch, one end of the sixth capacitor and one end of the second sensor electrode; the other end of the first switch is connected with one end of a third capacitor, the other end of the second sensor electrode, and a high trigger end and a low trigger end of a second timer; the other end of the second switch is connected with one end of a second capacitor, and the other end of the first sensor electrode is connected with a high trigger end and a low trigger end of a first timer; the other ends of the third capacitor and the second capacitor are grounded; the output end of the first reverser is connected with one end of a fifth capacitor, the other end of the fifth capacitor is connected with VCC of the input end of a second reverser, and the output end of the second reverser is connected with the other end of a sixth capacitor; the grounding ends of the first timer and the second timer are respectively connected with one ends of a first capacitor and a fourth capacitor, and the other ends of the first capacitor and the fourth capacitor are grounded.
Preferably, the first triode and the second triode are NPN triodes.
Preferably, the first timer and the second timer are 555 timers.
Preferably, the data acquisition circuit comprises an analog-to-digital converter, a signal amplifier, a third resistor, a fourth resistor, a fifth resistor and a sixth resistor, wherein one end of the fifth resistor is connected with the first sensor electrode or the second sensor electrode, the other end of the fifth resistor is connected with one end of the fourth resistor, and the other end of the fourth resistor is connected with one end of the third resistor and one input end of the signal amplifier; the other input of the signal amplifier is connected with a sixth resistor; the other end of the third resistor and the output end of the signal amplifier are connected with an analog-to-digital converter.
Preferably, the programmable logic array is a Cyclone II EP2C5T144 from Altera corporation.
Preferably, the conductivity test data is displayed on a display circuit, the display circuit being connected to the programmable logic array to display the conductivity test data.
Preferably, the device further comprises a memory connected with the programmable logic array to store the data after analog-to-digital conversion.
As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following advantages:
the invention provides a real-time intelligent conductivity detection system based on conductivity sensor electrode polarization compensation of a dual-mode self-adjusting conductivity detection circuit, which aims at solving the problems that the traditional conductivity detection equipment is low in test precision and low in intelligence degree, and the problems that homogeneous charges are concentrated on electrodes on the same side along with the increase of the traditional conductivity detection method along with the use time, so that the detection value is shifted, and the detection result is distorted. The system not only realizes automatic detection of conductivity, but also eliminates the influence of capacitance effect of the conductivity sensor electrode, overcomes the defects of detection value deviation and detection result distortion caused by the fact that homogeneous charges are concentrated on the same side electrode due to electrode polarization, and has good practical significance and high economic value.
Drawings
FIG. 1 is a block diagram of the system of the present invention;
FIG. 2 is a circuit diagram of the dual-mode self-adjusting conductivity detection circuit of the present invention;
FIG. 3 is a data acquisition circuit;
FIG. 4 is a display circuit;
wherein: 10. the device comprises a dual-mode self-adjusting conductivity detection circuit 20, a data acquisition circuit 30, a programmable logic array 40, a memory 50 and a display circuit.
Detailed Description
The invention is further described below by means of specific embodiments.
Referring to fig. 1 to 4, an intelligent water quality detection system based on dual-mode self-adjusting conductivity detection comprises a dual-mode self-adjusting conductivity detection circuit 10, a data acquisition circuit 20, a programmable logic array 30, a display circuit 50 and a memory 40. The dual-mode self-adjusting conductivity detection circuit 10 is provided with a first sensor electrode F1 and a second sensor electrode F2 to detect conductivity, and can also eliminate homogeneous charge polarization effect and improve detection precision and working speed. The data acquisition circuit 20 is connected to the dual-mode self-adjusting conductivity detection circuit 10 to acquire the variation data of the first sensor electrode F1 and the second sensor electrode F2 and perform analog-to-digital conversion, and the programmable logic array 30 temporarily stores the data into the memory 40. The programmable logic array 30 is connected to the dual-mode self-adjusting conductivity detection circuit 10, the data acquisition circuit 20, the display circuit 50 and the memory 40, and is used for analyzing the output of the dual-mode self-adjusting conductivity detection circuit 10, obtaining the equivalent impedance data of the conductivity sensor and comparing the equivalent impedance data with the analog-to-digital converted data temporarily stored in the memory 40. If the difference between the two is smaller than the preset measurement accuracy epsilon, the output is output through the display circuit 50, otherwise, the adjustable resistance (i.e. the fifth resistance R5) of the signal amplifying circuit in the data acquisition circuit 20 is adjusted until the difference between the two is smaller than the preset measurement accuracy epsilon.
Specifically, the dual-mode self-adjusting conductivity detection circuit 10 further includes a first timer J1, a second timer J2, a first inverter IV1, a second inverter IV2, a first triode Q1, a second triode Q2, a first switch S1, a second switch S2, a first sensor electrode F1, a second sensor electrode F2, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a first resistor R1, a second resistor R2, and the like. The first triode Q1 and the second triode Q2 are NPN triodes, and the first timer J1 and the second timer J2 are 555 timers.
The output ends of the first timer J1 and the second timer J2 are respectively connected with one ends of a first resistor R1 and a second resistor R2, and the other ends of the first resistor R1 and the second resistor R2 are respectively connected with the base electrodes of a first triode Q1 and a second triode Q2 and serve as a conductivity output end V 01 And V 01 . The collectors of the first transistor Q1 and the second transistor Q2 are connected to VCC. The emitter of the first triode Q1 is connected with the discharge end of the first timer J1, one end of the first switch S1, the input end of the first reverser IV1 and one end of the first sensor electrode F1. The emitter of the second triode Q2 is connected with the discharge end of a second timer J2, one end of a second switch S2, one end of a sixth capacitor C6 and one end of a second sensor electrode F2; the other end of the first switch S1 is connected with one end of a third capacitor C3, the other end of a second sensor electrode F2, and a high trigger end and a low trigger end of a second timer J2; the other end of the second switch S2 is connected to one end of the second capacitor C2, the other end of the first sensor electrode F1, and the high and low trigger terminals of the first timer J1. The other ends of the third capacitor C3 and the second capacitor C2 are grounded.
The output end of the first inverter IV1 is connected to one end of a fifth capacitor C5, the other end of the fifth capacitor C5 is connected to VCC together with the input end of the second inverter IV2, and the output end of the second inverter IV2 is connected to the other end of a sixth capacitor C6. The grounding ends of the first timer J1 and the second timer J2 are respectively connected with one ends of a first capacitor C1 and a fourth capacitor C4, and the other ends of the first capacitor C1 and the fourth capacitor C4 are grounded.
When the first switch S1 and the second switch S2 are turned off, i.e. S 1 S 2 When =00, the circuit normally starts the working mode, and the input voltage of the low trigger end of the timer is lower than 1/3V cc At the moment, the built-in trigger of the first timer J1 is set, the output end of the first timer J1 outputs high level, the first triode Q1 and the second triode Q2 are conducted, vcc passes through Q1 and Q2 and passes throughThe first sensor electrode F1 and the second sensor electrode F2 respectively charge the C2 and the C4, and meanwhile, a discharge switch tube arranged in the timer is cut off. In this mode, if the low trigger side trigger input exceeds the reference level by 2/3V cc And meanwhile, the high-level comparator in the high trigger end is turned over, the trigger is reset, the output end of the timer outputs a low level, the discharge switch tube is switched on, and the second capacitor C2 and the third capacitor C3 are discharged simultaneously.
When the second switch S2 is closed, the first switch S1 is turned off, i.e. S 1 S 2 And =01, the circuit is in the mode of eliminating polarization effect. At this time, the initial voltage of the input voltage of the low trigger end of the first timer J1 and the second timer J2 is zero, the built-in flip-flop is set, the output ends of the first timer J1 and the second timer J2 output high levels, the first triode Q1 and the second triode Q2 are switched on, vcc is charged to the second capacitor C2 and the fourth capacitor C4 through the first triode Q1 and the second triode Q2 and the first sensor electrode F1 and the second sensor electrode F2, respectively. Meanwhile, since the second switch S2 is closed, vcc charges the second capacitor C2 through the sixth capacitor C6 and the second inverter IV2 alone. Compared with S 1 S 2 Case =00, the circuit has a faster charging time. If the low trigger end input exceeds the reference level by 2/3V cc And meanwhile, the high-level comparator in the high trigger end is turned over, the trigger is reset, the 3 pins of the output end of the timer output low level, the discharge switch tube is switched on, and the second capacitor C2 and the third capacitor C3 discharge simultaneously. Since the second S2 is closed, it is compared to S 1 S 2 =00 operating mode increased by a 2 B 1 The charge leakage path has a faster charge discharge rate.
When the second switch S2 is turned off, the first switch S1 is closed, i.e. S 1 S 2 =10, the circuit is in the mode of eliminating polarization effect, and its working principle and S 1 S 2 Similarly, description is omitted when = 01.
The first inverter IV1 and the fifth capacitor C5 and the second inverter IV2 and the sixth capacitor C6 in the dual-mode self-adjusting conductivity detection circuit 10 can adjust the charge-discharge time coefficient of the circuit, improve the working speed of the circuit and widen the noise tolerance. The first triode Q1 and the second triode Q2 are used for expanding the load carrying capacity of the first timer J1 and the second timer J2, and when the system is used for measuring the conductivity, the circuit output has a wider linear range. The first resistor R1 and the second resistor R2 can improve the input impedance of the first triode Q1 and the second triode Q2 and reduce the 1/f noise of the circuit.
When the electrode polarization effect of the homogeneous charge is detected, the first switch S1 and the second switch S2 are set to S 1 S 2 =01 or 10, the detection circuit enters a polarization effect elimination mode, at this time, the A1 end of the first sensor electrode F1 is conducted with the B2 end of the second sensor electrode F2, or the A2 end of the first sensor electrode F1 is conducted with the B1 end of the second sensor electrode F2, so that the cations at the A1 end of the first sensor electrode F1 and the anions at the B2 end of the second sensor electrode F2 are neutralized, the direction of the potential difference between the two electrodes is opposite to that of the potential difference during testing, the cations on the cathode and the anions on the anode can be driven away, the next measurement result is accurate, and the problem of detection distortion is avoided.
According to the working principle of the circuit, the following formula can be obtained:
wherein
Z o Is the on-resistance, Z, of the first inverter IV1 F Is the equivalent impedance of the sensor resistance, V o1 The output of the conductivity detection circuit 10 is self-adjusting for two modes.
Thus, an output V of the dual-mode self-regulating conductivity detection circuit 10 is obtained o1 And electrical conductivity G F (G F ＝1/Z F ) The mathematical transformation relation of (1) is as follows:
can be shown from the above formulaGo out, V o1 And G F A linear relationship is present. Due to the circuit output V o1 The frequency form is adopted, so that the double-mode self-adjusting conductivity detection circuit 10 can be isolated from a micro system by adopting a photoelectric coupler to realize electric appliance isolation, the sensor electrode is considered as variable impedance research from the conductivity detection method essentially, the impedance is automatically jumped along with the frequency, the polarization effect and capacitance effect influence of the conductivity sensor electrode are eliminated, and the defects of detection value deviation and detection result distortion caused by the fact that homogeneous charges are concentrated on the same side electrode due to electrode polarization are avoided.
The data acquisition circuit 20 comprises an analog-to-digital converter, a signal amplifier, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a sixth resistor R6, wherein one end of the fifth resistor R5 is connected with the first sensor electrode F1 or the second sensor electrode F2, the other end of the fifth resistor R5 is connected with one end of the fourth resistor R4, and the other end of the fourth resistor R4 is connected with one end of the third resistor R3 and one input end of the signal amplifier; the other input of the signal amplifier is connected with a sixth resistor R6; the other end of the third resistor R3 and the output end of the signal amplifier are connected with an analog-to-digital converter. The ICL7189 is used as a sampling chip of the analog-digital converter. ICL7189 is based on a dual integration analog-to-digital converter, which integrates the input analog voltage for a fixed time, and then integrates the standard voltage in reverse phase until the integrated input returns to the initial value, where the two integration times are proportional to the two values, so as to obtain the digital quantity corresponding to the analog voltage. ICL7189 had the following properties: (a) high precision (1/4096 accurate); (b) low noise (typically 15 μ VP-P); (c) The output is compatible with TTL, is output in a byte mode (divided into high and low bytes) three-state mode, has a VART hook mode, and can be connected to a micro-processing system by a simple parallel or serial port; (d) The transition timing can be monitored and controlled with RVNHOLD (run/hold) and STATUS signals. Therefore, the ICL7109 is selected to meet the data acquisition requirements of the system. The signal amplifier selects model LM324, through gathering the conductivity sensor electrode change data in the detection circuit 10 of the bimodulus self-regulating conductivity, then send the conductivity signal into the analog-to-digital converter to carry on the analog-to-digital conversion through the amplifier in the acquisition circuit 20 of the data, the conductivity sensor is equivalent to the impedance R4, the measured signal passes a inverting signal amplifying circuit formed by conductivity sensor and known resistance R3. R5 is an adjustable rheostat for adjusting the resistance value of an adjustable resistor R5 of a signal amplifying circuit in the data acquisition circuit 20 until the difference value between the two is less than the preset measurement precision epsilon
Programmable logic array 30 is used to analyze the collected data, control the data in memory 40, and provide interactive access to the display, memory 40, etc. The programmable logic array 30 processes and displays the data, and when the parameter index shows change, the system automatically outputs. The signals from the dual mode self regulating conductivity detection circuit 10 and the data acquisition circuit 20 are converted, either directly or indirectly, by analog to digital converter ICL7189 and then collected, analyzed and stored by the programmable logic array 30. The primary roles of programmable logic array 30 are two-fold: firstly, analysis and acquisition control of an analog-to-digital converter are controlled, and accuracy of a data discretization result is ensured; and the second step is to cache data, analyze and judge the data measurement result. The output of the dual-mode self-adjusting conductivity detection circuit 10 is connected with the programmable logic array 30, the programmable logic array 30 is used to obtain the equivalent impedance data of the conductivity sensor and compare the equivalent impedance data with the data after the analog-to-digital conversion temporarily stored in the memory 40, and if the difference between the two is smaller than the preset measurement accuracy epsilon, the output is displayed through a peripheral circuit. Thus, the invention uses clone II EP2C5T144 from Altera under Intel. The Cyclone II-series FPGA adopts a 90nm technology of TSMC (station accumulated power), the density of the low-cost FPGA is expanded to 68 416 logic units (LES), so that a complex digital system can be realized on the low-cost FPGA, the stability is high, and the control requirement of system acquisition logic can be met.
The display circuit 50 is composed of a 4-bit eight-segment code, and the specific circuit is shown in fig. 4, and further includes a third triode Q3, a fourth triode Q4, a fifth triode Q5, and a sixth triode Q6. The circuit is in a common cathode connection mode, and cathodes of all the light emitting diodes are connected together to form a common cathode nixie tube. The programmable logic array 30 is adopted to control time division multiplexing and alternate control for 4 nixie tubes. Because the scanning speed of the programmable logic array 30 is fast enough to be faster than the visual response speed of human eyes, the display circuit 50 can stably display dynamic data, and simultaneously save a large number of input/output ports and has low power consumption. As can be seen from FIG. 4, 8 pins A-H of the 4 nixie tubes are connected to pins A3, B3, C3, D3, E3, F3, G3 and H3 of the programmable logic array 30. The emitters of the third transistor Q3, the fourth transistor Q4, the fifth transistor Q5 and the sixth transistor Q6 are connected to a 4-bit eight-segment code. The bases of the third transistor Q3, the fourth transistor Q4, the fifth transistor Q5 and the sixth transistor Q6 are respectively connected to the control pins D25, J22, E26 and E25 of the programmable logic array 30 through an impedance matching sixth resistor R6, a seventh resistor R7, an eighth resistor R8 and a ninth resistor R9. The corresponding nixie tubes can be selected through the control pins D25, J22, E26 and E25, and then the pins A3, B3, C3, D3, E3, F3, G3 and H3 are used for displaying the conductivity test data of the corresponding nixie tubes (1-4 nixie tubes).
The above description is only an embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any insubstantial modifications made by using the design concept should fall within the scope of infringing the present invention.
Claims (7)
1. An intelligent water quality detection system based on dual-mode self-adjustment conductivity detection is characterized in that: the system comprises a dual-mode self-adjusting conductivity detection circuit, a data acquisition circuit and a programmable logic array; the dual-mode self-adjusting conductivity detection circuit is provided with a first sensor electrode and a second sensor electrode to detect conductivity; the data acquisition circuit is connected with the dual-mode self-adjusting conductivity detection circuit to acquire the change data of the first sensor electrode and the second sensor electrode and perform analog-to-digital conversion; the programmable logic array is connected with the dual-mode self-adjusting conductivity detection circuit and the data acquisition circuit so as to compare the detected conductivity with the data after analog-to-digital conversion, and control the acquisition precision and the data conversion speed of the data acquisition circuit according to the comparison result; the dual-mode self-adjusting conductivity detection circuit comprises a first timer, a second timer, a first reverser, a second reverser, a first triode, a second triode, a first switch, a second switch, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a first resistor and a second resistor; the output ends of the first timer and the second timer are respectively connected with one ends of a first resistor and a second resistor, and the other ends of the first resistor and the second resistor are respectively connected with bases of a first triode and a second triode and serve as conductivity output ends; the collector electrodes of the first triode and the second triode are connected with VCC; the emitter of the first triode is connected with the discharge end of a first timer, one end of a first switch, the input end of a first reverser and one end of a first sensor electrode; the emitter of the second triode is connected with the discharge end of the second timer, one end of the second switch, one end of the sixth capacitor and one end of the second sensor electrode; the other end of the first switch is connected with one end of a third capacitor, the other end of the second sensor electrode, and a high trigger end and a low trigger end of a second timer; the other end of the second switch is connected with one end of a second capacitor, and the other end of the first sensor electrode is connected with a high trigger end and a low trigger end of a first timer; the other ends of the third capacitor and the second capacitor are grounded; the output end of the first reverser is connected with one end of a fifth capacitor, the other end of the fifth capacitor is connected with VCC of the input end of a second reverser, and the output end of the second reverser is connected with the other end of a sixth capacitor; the grounding ends of the first timer and the second timer are respectively connected with one ends of a first capacitor and a fourth capacitor, and the other ends of the first capacitor and the fourth capacitor are grounded.
2. The intelligent water quality detection system based on dual-mode self-adjusting conductivity detection as claimed in claim 1, wherein: the first triode and the second triode are NPN triodes.
3. The intelligent water quality detection system based on dual-mode self-regulation conductivity detection as claimed in claim 1, wherein: the first timer and the second timer are 555 timers.
4. The intelligent water quality detection system based on dual-mode self-regulation conductivity detection as claimed in claim 1, wherein: the data acquisition circuit comprises an analog-to-digital converter, a signal amplifier, a third resistor, a fourth resistor, a fifth resistor and a sixth resistor, wherein one end of the fifth resistor is connected with the first sensor electrode or the second sensor electrode, the other end of the fifth resistor is connected with one end of the fourth resistor, and the other end of the fourth resistor is connected with one end of the third resistor and one input end of the signal amplifier; the other input of the signal amplifier is connected with a sixth resistor; the other end of the third resistor and the output end of the signal amplifier are connected with an analog-to-digital converter.
5. The intelligent water quality detection system based on dual-mode self-regulation conductivity detection as claimed in claim 1, wherein: the programmable logic array is clone II EP2C5T144 from Altera.
6. The intelligent water quality detection system based on dual-mode self-regulation conductivity detection as claimed in claim 1, wherein: and the display circuit is connected with the programmable logic array to display the conductivity test data.
7. The intelligent water quality detection system based on dual-mode self-regulation conductivity detection as claimed in claim 1, wherein: and the memory is connected with the programmable logic array to store the data after analog-to-digital conversion.
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