CN116087179A - Water quality monitoring circuit and water quality analyzer - Google Patents
Water quality monitoring circuit and water quality analyzer Download PDFInfo
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Abstract
The invention relates to a water quality monitoring circuit and a water quality analyzer, wherein the water quality monitoring circuit is used for monitoring coliform in water quality and comprises the following components: the colorimetric light source control circuit unit is used for controlling stable output of the colorimetric light source by utilizing gain adjustment; the ultraviolet light source control circuit unit is used for controlling the stable output of the ultraviolet light source by utilizing gain adjustment; the colorimetric detection circuit unit is used for detecting a target light signal emitted after the colorimetric light source irradiates the coliform group culture tank and converting the target light signal into a first voltage signal; the fluorescence detection circuit unit is used for detecting a fluorescence signal generated after the ultraviolet light source irradiates the coliform group culture tank and converting the fluorescence signal into a second voltage signal; the ADC data acquisition circuit unit is used for respectively converting the first voltage signal and the second voltage signal into corresponding digital signals so as to obtain the concentration of coliform bacteria. The invention can simultaneously carry out colorimetric and fluorescent detection, and has high efficiency and high precision.
Description
Technical Field
The invention belongs to the technical field of analysis and detection, and particularly relates to a water quality monitoring circuit and a water quality analyzer.
Background
Coli is ubiquitous in the human and animal intestinal tract, and if the population of E.coli is found in the natural environment, it can be demonstrated that it is contaminated with faeces and that other intestinal pathogens may be present. Thus, the measurement of coliform can be used as an indicator of contamination of water or food with fecal material.
In the microbial test, the most amount of the feces is coliform, and the survival time of the coliform after the coliform is discharged along with the feces is approximately similar to that of main pathogenic bacteria in intestinal tracts. Therefore, it is preferable to select coliform bacteria as fecal contamination indicator bacteria.
In practical application, the more common method for measuring the escherichia coli comprises the following steps: enzyme substrate method, multitube fermentation method, filter method and PCR (gene fragment). According to the national standard GB/T4789.32-2002, an analyzer generally adopts an enzyme substrate method, and the main principle is as follows: the total coliform, the fecal coliform, the escherichia coli form and the like can generate beta-galactosidase under specific culture conditions, and colorless substrates o-nitrobenzene-beta-D-galactopyranoside in a selective culture medium can be decomposed into yellow o-nitrophenol, so that the culture medium is yellow, and the concentration of the total escherichia coli form can be obtained through colorimetric measurement; the escherichia coli can also produce beta-glucuronidase, 4-methylumbelliferone-beta-D-glucuronide in a selective culture medium can be decomposed into 4-methylumbelliferone, fluorescence can be generated under the irradiation of an ultraviolet lamp, and the concentration of the escherichia coli group can be measured by measuring the fluorescence intensity; thus, the concentration of the total coliform, fecal coliform and Escherichia coli can be obtained.
The existing detection circuit has the defects that the light source is unstable to drive, the color comparison and the fluorescence detection cannot be simultaneously carried out, and the detection precision and the detection efficiency are low.
Disclosure of Invention
In view of the foregoing drawbacks and deficiencies of the prior art, it is an object of the present invention to at least solve one or more of the above-mentioned problems of the prior art, in other words, to provide a water quality monitoring circuit and a water quality analyzer that meet one or more of the above-mentioned needs.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
a water quality monitoring circuit for monitoring coliform bacteria in water quality, comprising:
the colorimetric light source control circuit unit is used for controlling stable output of the colorimetric light source by utilizing gain adjustment;
the ultraviolet light source control circuit unit is used for controlling the stable output of the ultraviolet light source by utilizing gain adjustment;
the colorimetric detection circuit unit is used for detecting a target light signal emitted after the colorimetric light source irradiates the coliform group culture tank and converting the target light signal into a first voltage signal;
the fluorescence detection circuit unit is used for detecting a fluorescence signal generated after the ultraviolet light source irradiates the coliform group culture tank and converting the fluorescence signal into a second voltage signal;
the ADC data acquisition circuit unit is used for respectively converting the first voltage signal and the second voltage signal into corresponding digital signals so as to obtain the concentration of coliform bacteria.
As a preferred scheme, the colorimetric light source control circuit unit comprises a colorimetric light source, a first light source constant current driving circuit module, a first reference detector feedback circuit module and a first gain adjusting circuit module, wherein the first light source constant current driving circuit module is used for driving the colorimetric light source to emit light, the first reference detector feedback circuit module is used for detecting a light signal of the colorimetric light source and converting the light signal into a voltage signal, and the first gain adjusting circuit module is used for comparing according to the voltage signal and a preset input voltage so as to dynamically adjust the driving current output by the first light source constant current driving circuit module.
As a preferred scheme, the ultraviolet light source control circuit unit comprises an ultraviolet light source, a second light source constant current driving circuit module, a second reference detector feedback circuit module and a second gain adjusting circuit module, wherein the second light source constant current driving circuit module is used for driving the ultraviolet light source to emit light, the second reference detector feedback circuit module is used for detecting an optical signal of the ultraviolet light source and converting the optical signal into a voltage signal, and the second gain adjusting circuit module is used for comparing according to the voltage signal and a preset input voltage so as to dynamically adjust the driving current output by the second light source constant current driving circuit module.
As a preferred scheme, the first gain adjustment circuit module or the second gain adjustment circuit module comprises a resistor R16, a resistor R25, an operational amplifier U7, a resistor R30, a capacitor C36, an operational amplifier U12, a capacitor C30, a capacitor C31, a resistor R28 and a resistor R29, wherein the resistor R16 is respectively connected with the first reference detector feedback circuit module or the second reference detector feedback circuit module and the non-inverting terminal of the operational amplifier U7, the resistor R25 is respectively connected with the inverting terminal and the output terminal of the operational amplifier U7, and the resistor R16, the resistor R25 and the operational amplifier U7 form a voltage follower; the resistor R30 and the capacitor C36 form RC filtering, the voltage output end of the singlechip is connected to the opposite phase end of the operational amplifier U12 through RC filtering, the in-phase end of the operational amplifier U12 is connected to the output end of the operational amplifier U7 through the resistor R29, and the output end of the operational amplifier U12 is connected to the first light source constant current driving circuit module or the second light source constant current driving circuit module; the capacitor C30, the capacitor C31, the resistor R28 and the resistor R29 are connected in series and form a loop with the in-phase end and the output end of the operational amplifier U12 so as to carry out loop compensation;
the operational amplifier U7 and the operational amplifier U12 are powered by a power supply.
As a preferred scheme, the first light source constant current driving circuit module or the second light source constant current driving circuit module comprises a current feedback resistor R40, a triode Q1, an operational amplifier U15, a resistor R39 and a capacitor C39, wherein the in-phase end of the operational amplifier U15 is connected with the output end of the operational amplifier U12, the output end of the operational amplifier U15 is connected with the base electrode of the triode Q1, the collector electrode of the triode Q1 is connected to the positive electrode of a power supply, the emitter electrode of the triode Q1 is connected with the positive electrode of a colorimetric light source or an ultraviolet light source, and the negative electrode of the colorimetric light source or the ultraviolet light source and the opposite end of the operational amplifier U15 are respectively connected to the negative electrode of the power supply through the current feedback resistor R40; the resistor R39 and the capacitor C39 are connected in series and connected between the negative electrode of the colorimetric light source or the ultraviolet light source and the inverting end of the operational amplifier U15 to form loop compensation;
the op-amp U15 is powered by a power supply.
As a preferred scheme, the first reference detector feedback circuit module or the second reference detector feedback circuit module comprises a photoelectric detector D2, a resistor R20, an operational amplifier U11 and a feedback capacitor C25, wherein the positive electrode of the photoelectric detector D2 is connected with the non-inverting terminal of the operational amplifier U11, and the negative electrode of the photoelectric detector D2 is connected with the inverting terminal of the operational amplifier U11; the resistor R20 is connected in parallel with the feedback capacitor C25 and is respectively connected to the inverting terminal and the output terminal of the operational amplifier U11; the output end of the operational amplifier U11 is connected with a resistor R16;
wherein, the resistor R20 and the operational amplifier U11 form a transimpedance amplifier; the op-amp U11 is powered by a power supply.
As a preferred scheme, the colorimetric detection circuit unit or the fluorescence detection circuit unit comprises a photoelectric detector D3, an operational amplifier U10, a resistor R22, a feedback capacitor C26, a resistor R17, a resistor R26, a resistor R24 and an operational amplifier U6, wherein the positive electrode of the photoelectric detector D3 is connected with the same-phase end of the operational amplifier U10, and the negative electrode of the photoelectric detector D3 is connected with the opposite-phase end of the operational amplifier U10; the resistor R22 is connected in parallel with the feedback capacitor C26 and is respectively connected to the inverting terminal and the output terminal of the operational amplifier U10; the resistor R17 is respectively connected to the in-phase end of the operational amplifier U6 and the output end of the operational amplifier U10, the resistor R26 is respectively connected to the output end and the inverting end of the operational amplifier U6, and the resistor R24 is respectively connected to the inverting end of the operational amplifier U6 and the negative electrode of the power supply;
the resistor R22 and the operational amplifier U10 form a transimpedance amplifier, and the operational amplifier U6 and the operational amplifier U10 are powered by a power supply.
Preferably, the colorimetric detection circuit unit is electrically connected with the ADC data acquisition circuit unit through the first filter circuit unit.
Preferably, the fluorescence detection circuit unit is electrically connected with the ADC data acquisition circuit unit through the integration circuit unit and the second filter circuit unit in sequence.
The invention also provides a water quality analyzer, which adopts the water quality monitoring circuit according to any scheme.
Compared with the prior art, the invention has the beneficial effects that:
(1) The brightness of the light source can be set; the brightness of the light emitting diode of the light source can be controlled by controlling the initial input voltage through the singlechip, so that the method is suitable for detecting sample applications with different concentrations, and is flexible and convenient;
(2) The stability of the light source is high and the light source is automatically adjusted in real time; the whole circuit uses a circuit to carry out negative feedback, automatically adjusts and controls the current of the light emitting diode, has high response speed and stable output, and has actual measurement fluctuation smaller than 0.5 per mill;
(3) Low system drift; the temperature drift of the whole driving circuit in the whole temperature range (0-50 ℃) of the instrument is less than 1 per mill; the time drift is less than 5 per mill after long-term test;
(4) The service life of the light source is long. As is generally known, the luminous intensity of an LED light source is weakened along with the increase of the service time, and the measurement accuracy of a meter is difficult to guarantee in the past for a long time;
(5) The measurement efficiency is high; the two paths of measuring circuits are designed, so that colorimetric and fluorescence can be measured simultaneously, and compared with the traditional measuring circuits, half of time is shortened;
(6) The measurement accuracy is high; because the colorimetric light intensity and the fluorescent light intensity have a great difference, the same detection circuit is used, the fixed amplification factors are difficult to coordinate two different light signals, and the two detection circuits are adopted to amplify the two different signals to a proper interval for detection, so that the detection is more accurate.
Drawings
FIG. 1 is a block diagram of a water quality monitoring circuit according to an embodiment of the present invention;
FIG. 2 is a circuit diagram of a colorimetric light source control circuit unit in accordance with an embodiment of the invention;
fig. 3 is a circuit diagram of a colorimetric detection circuit unit, a fluorescence detection circuit unit, and an ADC data acquisition circuit unit according to an embodiment of the invention.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention, specific embodiments of the present invention will be described below with reference to the accompanying drawings. It is evident that the drawings in the following description are only examples of the invention, from which other drawings and other embodiments can be obtained by a person skilled in the art without inventive effort.
Example 1:
as shown in fig. 1, the water quality monitoring circuit in this embodiment includes a colorimetric light source control circuit unit (i.e., a colorimetric light source control circuit), an ultraviolet light source control circuit unit (i.e., an ultraviolet light source control circuit), a colorimetric detection circuit unit (i.e., a colorimetric detection circuit), a fluorescent detection circuit unit (i.e., a fluorescent detection circuit), and an ADC data acquisition circuit unit (abbreviated as ADC), so as to implement measurement of total coliform, fecal coliform, and escherichia coli concentration in water.
The colorimetric light source control circuit unit of the embodiment is used for controlling stable output of the colorimetric light source by utilizing gain adjustment. Specifically, the colorimetric light source control circuit unit comprises a colorimetric light source, a first light source constant current driving circuit module (short for light source driving circuit), a first reference detector feedback circuit module (short for reference detector) and a first gain adjusting circuit module (short for gain adjusting circuit), wherein the first light source constant current driving circuit module is used for driving the colorimetric light source to emit light, the first reference detector feedback circuit module is used for detecting an optical signal of the colorimetric light source and converting the optical signal into a voltage signal, and the first gain adjusting circuit module is used for comparing according to the voltage signal and a preset input voltage so as to dynamically adjust the driving current output by the first light source constant current driving circuit module.
As shown in fig. 2, the first gain adjustment circuit module includes a resistor R16, a resistor R25, an operational amplifier U7, a resistor R30, a capacitor C36, an operational amplifier U12, a capacitor C30, a capacitor C31, a resistor R28, and a resistor R29, where the resistor R16 is connected to the feedback circuit module of the first reference detector and the non-inverting terminal of the operational amplifier U7, and the resistor R25 is connected to the inverting terminal and the output terminal of the operational amplifier U7, and the resistor R16, the resistor R25, and the operational amplifier U7 form a voltage follower; one end of a resistor R30 is connected to a voltage output end MCU_Vout of the singlechip, the other end of the resistor R30 is respectively connected to an inverting end of the operational amplifier U12 and a capacitor C36, the capacitor C36 is also connected to a power supply negative electrode, the resistor R30 and the capacitor C36 form RC filtering, the voltage output end of the singlechip is connected to the inverting end of the operational amplifier U12 through RC filtering, the in-phase end of the operational amplifier U12 is connected to an output end of the operational amplifier U7 through a resistor R29, and the output end of the operational amplifier U12 is connected to a first light source constant current driving circuit module; the capacitor C30, the capacitor C31, the resistor R28 and the resistor R29 are connected in series and form a loop with the in-phase end and the output end of the operational amplifier U12 so as to carry out loop compensation;
the operational amplifier U7 and the operational amplifier U12 are powered by a power supply.
The first light source constant current driving circuit module comprises a current feedback resistor R40, a triode Q1, an operational amplifier U15, a resistor R39 and a capacitor C39, wherein the in-phase end of the operational amplifier U15 is connected with the output end of the operational amplifier U12, the output end of the operational amplifier U15 is connected with a base electrode 1 of the triode Q1, a collector electrode 3 of the triode Q1 is connected to a power supply positive electrode VCC, an emitter electrode 2 of the triode Q1 is connected with the positive electrode of a colorimetric light source (namely a light emitting diode) D4, and the negative electrode of the colorimetric light source D4 and the opposite phase end of the operational amplifier U15 are respectively connected to the negative electrode of the power supply through the current feedback resistor R40; the resistor R39 and the capacitor C39 are connected in series and connected between the negative electrode of the colorimetric light source D4 and the inverting end of the operational amplifier U15 to form loop compensation;
wherein the op-amp U15 is powered by a power supply.
The first reference detector feedback circuit module comprises a photoelectric detector D2, a resistor R20, an operational amplifier U11 and a feedback capacitor C25, wherein the positive electrode of the photoelectric detector D2 is connected with the same phase end of the operational amplifier U11, and the negative electrode of the photoelectric detector D2 is also connected to the opposite phase end of the operational amplifier U11 and the negative electrode of the power supply respectively; the resistor R20 is connected in parallel with the feedback capacitor C25 and is respectively connected to the inverting terminal and the output terminal of the operational amplifier U11; the output end of the operational amplifier U11 is connected with a resistor R16;
wherein, the resistor R20 and the operational amplifier U11 form a transimpedance amplifier; the op-amp U11 is powered by a power supply.
The working principle of the colorimetric light source control circuit unit of the embodiment is as follows:
1. the method comprises the steps that an initial input voltage MCU_Vout of a first gain adjusting circuit module is set through a singlechip, the initial input voltage MCU_Vout is input to an inverting terminal of an operational amplifier U12 after RC filtering, at the moment, the output of a first reference detector feedback circuit module is 0V because a light emitting diode D4 is not lightened yet, the voltage input to an in-phase terminal of the operational amplifier U12 is also 0V, the voltage of the inverting terminal is larger than that of the in-phase terminal, the operational amplifier U12 outputs the maximum value (power voltage VCC) to the in-phase input terminal of the operational amplifier U15, and a first light source constant current driving circuit module starts to work;
2. at this time, as the input of the first light source constant current driving circuit module is the maximum value, the operational amplifier U15 controls the triode Q1 to generate the maximum current value, the light emitting diode D4 generates the maximum light intensity, the brightness reaches the maximum, and the loop compensation networks R39 and C39 enable the light source constant current driving circuit to work stably without oscillation;
3. the photoelectric detector D2 of the first reference detector feedback circuit module detects light of the light emitting diode D4, corresponding current flows out, a transimpedance amplifier formed by the resistor R20 and the operational amplifier U11 converts the current value into a corresponding voltage value, the corresponding voltage value is output to a next-stage circuit for gain adjustment, the feedback capacitor C25 limits the bandwidth, and the circuit is kept stable. In particular, since the output voltage is obtained by multiplying the current output by the photodetector by the resistor R20, the resistor uses a resistor with a low temperature drift and an accuracy of one thousandth, and the capacitor C25 also uses a low temperature drift capacitor with a material NP 0; gain adjustment compares the voltage signal with MCU_Vout controlled by the singlechip, and performs negative feedback: when the voltage signal is larger than MCU_Vout, reducing the current output by the constant current source, so that the luminous intensity of the light emitting diode D4 is weakened; when the voltage signal is smaller than MCU_Vout, increasing the current output by the constant current source, so that the luminous intensity of the light emitting diode D4 is enhanced; a very stable light source can be obtained through dynamic adjustment, so that the stability and the accuracy of subsequent colorimetric measurement and fluorescence detection can be directly improved;
4. the output voltage of the previous stage circuit is buffered by a voltage follower formed by the resistor R16, the resistor R25 and the operational amplifier U7, and the output of the circuit is equal to the input, so that the circuit is mainly used for improving the impedance input to the operational amplifier U12 and avoiding the influence of a transimpedance amplifier on a loop compensation network of the U12;
5. the voltage output by the operational amplifier U7 enters the in-phase end of the operational amplifier U12 through the resistor R29, the voltage of the in-phase end is larger than that of the anti-phase end at the moment, the output value of the operational amplifier U12 is reduced from the maximum value, the first light source constant current driving circuit module controls the current to be reduced, the luminous intensity of the light emitting diode D4 is reduced along with the reduction, the output voltage of the first reference detector feedback circuit module is reduced along with the reduction, and the balance is achieved until the voltage of the in-phase end of the operational amplifier U12 is equal to that of the anti-phase end. In particular, the loop compensation formed by the capacitor C30, the capacitor C31, the resistor R28 and the resistor R29 enables the whole regulating circuit to reach an equilibrium state quickly and stably during negative feedback regulation, and oscillation cannot occur. All operational amplifiers in the circuit are precise operational amplifiers with low offset and low drift so as to ensure the stability of the output of each stage.
The ultraviolet light source control circuit unit of the embodiment is used for controlling stable output of the ultraviolet light source by utilizing gain adjustment. Specifically, the ultraviolet light source control circuit unit comprises an ultraviolet light source, a second light source constant current driving circuit module, a second reference detector feedback circuit module and a second gain adjusting circuit module, wherein the second light source constant current driving circuit module is used for driving the ultraviolet light source to emit light, the second reference detector feedback circuit module is used for detecting an optical signal of the ultraviolet light source and converting the optical signal into a voltage signal, and the second gain adjusting circuit module is used for comparing according to the voltage signal and a preset input voltage so as to dynamically adjust driving current output by the second light source constant current driving circuit module.
The specific circuit of the ultraviolet light source control circuit unit in this embodiment has the same circuit structure as that of the colorimetric light source control circuit unit, and only the colorimetric light source needs to be replaced by an ultraviolet light source, which is not described herein.
Light emitted by the light emitting diode D4 is injected into an escherichia coli flora culture tank (short for culture tank) for colorimetric measurement and fluorescence excitation.
As shown in fig. 3, the colorimetric detection circuit unit of the present embodiment is configured to detect a target optical signal emitted after the colorimetric light source irradiates the coliform culture tank, and convert the target optical signal into a first voltage signal.
Specifically, the colorimetric detection circuit unit comprises a photoelectric detector D3, an operational amplifier U10, a resistor R22, a feedback capacitor C26, a resistor R17, a resistor R26, a resistor R24 and an operational amplifier U6, wherein the positive electrode of the photoelectric detector D3 is connected with the same-phase end of the operational amplifier U10, and the negative electrode of the photoelectric detector D3 is connected with the opposite-phase end of the operational amplifier U10; the resistor R22 is connected in parallel with the feedback capacitor C26 and is respectively connected to the inverting terminal and the output terminal of the operational amplifier U10; the resistor R17 is respectively connected to the in-phase end of the operational amplifier U6 and the output end of the operational amplifier U10, the resistor R26 is respectively connected to the output end and the inverting end of the operational amplifier U6, and the resistor R24 is respectively connected to the inverting end of the operational amplifier U6 and the negative electrode of the power supply;
the resistor R22 and the operational amplifier U10 form a transimpedance amplifier, and the feedback capacitor C26, the resistor R17, the resistor R26, the resistor R24 and the operational amplifier U6 form a first-stage in-phase amplifying circuit; the operational amplifier U6 and the operational amplifier U10 are powered by a power supply.
In addition, the colorimetric detection circuit unit of the embodiment is electrically connected with the ADC data acquisition circuit unit through the first filter circuit unit.
Specifically, the first filter circuit unit comprises a first-stage active low-pass filter formed by a capacitor C24, a capacitor C27, a capacitor C29, a resistor R19, a resistor R18, a resistor R23, a resistor R27 and an operational amplifier U8, and is also a second-stage in-phase amplifying circuit, and further comprises a second-stage passive filter formed by a resistor R21 and a capacitor C28.
The working principle of the colorimetric detection circuit unit of the embodiment is as follows:
the photoelectric detector D3 detects colorimetric light absorbed by a sample to be detected to generate a current signal, the current signal is converted into corresponding voltage through a transimpedance amplifier, and the feedback capacitor C26 limits the bandwidth and keeps the circuit stable; the voltage signal enters a first-stage in-phase amplifier formed by the operational amplifier U6 to be amplified, and the first-stage in-phase amplifier converts and amplifies a weak optical signal into a processable electric signal and enters a next-stage circuit. In particular, since the output voltage is obtained by multiplying the current output from the photodetector by the resistor R22, the resistor uses a low temperature drift resistor with an accuracy of one thousandth, and the capacitor C26 also uses a low temperature drift capacitor made of NP 0. The first filter circuit unit amplifies the amplified signal again and performs two-stage filtering to remove most of interference and fluctuation on the signal, so that the later-stage measurement is facilitated.
The fluorescence detection circuit unit of the embodiment is used for detecting a fluorescence signal generated after the ultraviolet light source irradiates the coliform group culture tank and converting the fluorescence signal into a second voltage signal.
Specifically, the fluorescence detection circuit unit comprises a photoelectric detector D5, an operational amplifier U17, a resistor R32, a feedback capacitor C34, a resistor R31, a resistor R38, a resistor R42 and an operational amplifier U13, wherein the positive electrode of the photoelectric detector D5 is connected with the same-phase end of the operational amplifier U17, and the negative electrode of the photoelectric detector D5 is connected with the opposite-phase end of the operational amplifier U17; the resistor R32 is connected in parallel with the feedback capacitor C34 and is respectively connected to the inverting terminal and the output terminal of the operational amplifier U17; the resistor R31 is respectively connected to the in-phase end of the operational amplifier U13 and the output end of the operational amplifier U17, the resistor R38 is respectively connected to the output end and the inverting end of the operational amplifier U13, and the resistor R42 is respectively connected to the inverting end and the power supply negative electrode of the operational amplifier U13;
the resistor R32 and the operational amplifier U17 form a transimpedance amplifier, and a first-stage in-phase amplifying circuit consists of a feedback capacitor C34, a resistor R31, a resistor R42, a resistor R38 and the operational amplifier U13; the operational amplifier U13 and the operational amplifier U17 are powered by a power supply.
In addition, the fluorescence detection circuit unit is electrically connected with the ADC data acquisition circuit unit through the integration circuit unit and the second filter circuit unit in sequence.
The integrating circuit of this embodiment includes a resistor R33, a capacitor C33 and an operational amplifier U14, where one end of the resistor R33 is connected to the output end of the operational amplifier U13, the other end is connected to one end of the capacitor C33 and the inverting end of the operational amplifier U14, the other end of the capacitor C33 is connected to the output end of the operational amplifier U14, and the non-inverting end of the operational amplifier U14 is connected to the negative electrode of the power supply.
The second filter circuit unit of this embodiment includes a first stage active low-pass filter formed by a capacitor C32, a capacitor C35, a capacitor C38, a resistor R34, a resistor R37, a resistor R41, a resistor R35 and an operational amplifier U8, and also includes a second stage in-phase amplifying circuit, and further includes a second stage passive filter formed by a resistor R36 and a capacitor C37.
The working principle of the fluorescence detection circuit unit of this embodiment is:
the photoelectric detector D5 of the fluorescence detection circuit detects that the fluorescence excited by the sample to be detected generates a current signal, the current signal is converted into corresponding voltage through a transimpedance amplifier, and the feedback capacitor C34 limits the bandwidth and keeps the circuit stable; the voltage signal enters a first-stage in-phase amplifier formed by U13 for amplification, and the first-stage circuit converts and amplifies a weak optical signal into a processable electric signal and enters a next-stage circuit. In particular, since the output voltage is obtained by multiplying the current output from the photodetector by the resistor R32, the resistor uses a low temperature drift resistor with an accuracy of one thousandth, and the capacitor C34 also uses a low temperature drift capacitor made of NP 0.
Because the fluorescent signal is too weak, even though the amplification by the operational amplifier U13 is still small in amplitude, the waveform distortion and the interference are likely to be serious due to the fact that the amplification factor is directly set to be too large. The fluorescent signal is added with a first-stage integrating circuit relative to the colorimetric signal, and the unstable fluorescent signal generated by excitation is subjected to integration processing, so that the signal is changed into a gentle direct current signal.
The second filter circuit unit amplifies the integrated signal again and performs two-stage filtering, so that most of interference and fluctuation on the signal are filtered out, and the later-stage measurement is facilitated. The magnification setting of the fluorescent moiety will be greater than the colorimetric moiety, making the fluorescent signal easier to measure.
The ADC data acquisition circuit unit of this embodiment is configured to convert the first voltage signal and the second voltage signal into corresponding digital signals, respectively, so as to obtain the concentration of the coliform group bacteria.
Specifically, the ADC data acquisition circuit unit adopts two paths of input 24-bit high-precision ADC chips U9 controlled by the singlechip, and can convert two paths of analog electric signals into 24-bit digital signals simultaneously under the control of the singlechip so as to facilitate subsequent data calculation.
The working principle of the water quality monitoring circuit of the embodiment is as follows:
(1) The colorimetric light source irradiates and enters the culture tank, the light of the color contrast color is absorbed by the o-nitrophenol produced by the culture of the coliform group, so that the emitted light is weakened, that is, the detected light intensity is inversely proportional to the concentration of the o-nitrophenol, after the colorimetric detector receives the light signal, the trans-impedance amplifier U10 converts the light signal into a corresponding voltage signal, and the corresponding voltage signal is sampled by the ADC after passing through the in-phase amplifier U6 and the filter circuit, so that the concentration of the o-nitrophenol is calculated, and the concentration of the total coliform group is calculated;
(2) The ultraviolet light source irradiates and enters the culture tank to excite the 4-methylumbelliferone in the culture tank to generate fluorescence, the intensity of the fluorescence is in direct proportion to the concentration of the 4-methylumbelliferone, after the fluorescence detector receives a fluorescence signal, the trans-impedance amplifier U17 converts the fluorescence signal into a corresponding voltage signal, and as the fluorescence is weaker, the U14 integrates the voltage signal and then filters and amplifies the voltage signal, and the ADC samples the voltage signal to obtain a corresponding value, so that the concentration of the 4-methylumbelliferone is calculated, and the concentration of the escherichia coli group is calculated;
(3) And (3) subtracting the values in the steps (1) and (2) to obtain the concentration of the coliform faecalis.
The water quality analyzer of the embodiment adopts the water quality monitoring circuit of the embodiment, so that the analysis efficiency is high, and the analysis precision is also high.
The above-mentioned connection with the power supply negative electrode in this embodiment is grounding.
Example 2:
the water quality monitoring circuit of this embodiment is different from embodiment 1 in that:
the integrating circuit part and the filter circuit part of the embodiment 1 can be replaced by the existing common integrating circuit and filter circuit, so that the requirements of different applications are met;
other circuit configurations can be referred to embodiment 1;
the water quality analyzer of the embodiment adopts the water quality monitoring circuit of the embodiment, so that the analysis efficiency is high, and the analysis precision is also high.
The foregoing is only illustrative of the preferred embodiments and principles of the present invention, and changes in specific embodiments will occur to those skilled in the art upon consideration of the teachings provided herein, and such changes are intended to be included within the scope of the invention as defined by the claims.
Claims (10)
1. A water quality monitoring circuit for monitoring coliform bacteria in water quality, comprising:
the colorimetric light source control circuit unit is used for controlling stable output of the colorimetric light source by utilizing gain adjustment;
the ultraviolet light source control circuit unit is used for controlling the stable output of the ultraviolet light source by utilizing gain adjustment;
the colorimetric detection circuit unit is used for detecting a target light signal emitted after the colorimetric light source irradiates the coliform group culture tank and converting the target light signal into a first voltage signal;
the fluorescence detection circuit unit is used for detecting a fluorescence signal generated after the ultraviolet light source irradiates the coliform group culture tank and converting the fluorescence signal into a second voltage signal;
the ADC data acquisition circuit unit is used for respectively converting the first voltage signal and the second voltage signal into corresponding digital signals so as to obtain the concentration of coliform bacteria.
2. The water quality monitoring circuit of claim 1, wherein the colorimetric light source control circuit unit comprises a colorimetric light source, a first light source constant current driving circuit module, a first reference detector feedback circuit module and a first gain adjustment circuit module, the first light source constant current driving circuit module is used for driving the colorimetric light source to emit light, the first reference detector feedback circuit module is used for detecting an optical signal of the colorimetric light source and converting the optical signal into a voltage signal, and the first gain adjustment circuit module is used for comparing according to the voltage signal and a preset input voltage to dynamically adjust the driving current output by the first light source constant current driving circuit module.
3. The water quality monitoring circuit according to claim 1, wherein the ultraviolet light source control circuit unit comprises an ultraviolet light source, a second light source constant current driving circuit module, a second reference detector feedback circuit module and a second gain adjustment circuit module, the second light source constant current driving circuit module is used for driving the ultraviolet light source to emit light, the second reference detector feedback circuit module is used for detecting an optical signal of the ultraviolet light source and converting the optical signal into a voltage signal, and the second gain adjustment circuit module is used for comparing according to the voltage signal and a preset input voltage to dynamically adjust the driving current output by the second light source constant current driving circuit module.
4. The water quality monitoring circuit according to claim 2 or 3, wherein the first gain adjustment circuit module or the second gain adjustment circuit module comprises a resistor R16, a resistor R25, an operational amplifier U7, a resistor R30, a capacitor C36, an operational amplifier U12, a capacitor C30, a capacitor C31, a resistor R28 and a resistor R29, the resistor R16 is respectively connected with the first reference detector feedback circuit module or the second reference detector feedback circuit module, the non-inverting terminal of the operational amplifier U7, the resistor R25 is respectively connected with the inverting terminal and the output terminal of the operational amplifier U7, and the resistor R16, the resistor R25 and the operational amplifier U7 form a voltage follower; the resistor R30 and the capacitor C36 form RC filtering, the voltage output end of the singlechip is connected to the opposite phase end of the operational amplifier U12 through RC filtering, the in-phase end of the operational amplifier U12 is connected to the output end of the operational amplifier U7 through the resistor R29, and the output end of the operational amplifier U12 is connected to the first light source constant current driving circuit module or the second light source constant current driving circuit module; the capacitor C30, the capacitor C31, the resistor R28 and the resistor R29 are connected in series and form a loop with the in-phase end and the output end of the operational amplifier U12 so as to carry out loop compensation;
the operational amplifier U7 and the operational amplifier U12 are powered by a power supply.
5. The water quality monitoring circuit according to claim 4, wherein the first light source constant current driving circuit module or the second light source constant current driving circuit module comprises a current feedback resistor R40, a triode Q1, an operational amplifier U15, a resistor R39 and a capacitor C39, the in-phase end of the operational amplifier U15 is connected with the output end of the operational amplifier U12, the output end of the operational amplifier U15 is connected with the base electrode of the triode Q1, the collector electrode of the triode Q1 is connected to the positive electrode of the power supply, the emitter electrode of the triode Q1 is connected to the positive electrode of the colorimetric light source or the ultraviolet light source, and the negative electrode of the colorimetric light source or the negative electrode of the ultraviolet light source and the inverting end of the operational amplifier U15 are respectively connected to the negative electrode of the power supply through the current feedback resistor R40; the resistor R39 and the capacitor C39 are connected in series and connected between the negative electrode of the colorimetric light source or the ultraviolet light source and the inverting end of the operational amplifier U15 to form loop compensation;
the op-amp U15 is powered by a power supply.
6. The water quality monitoring circuit of claim 5, wherein the first reference detector feedback circuit module or the second reference detector feedback circuit module comprises a photo detector D2, a resistor R20, an op-amp U11 and a feedback capacitor C25, wherein the positive electrode of the photo detector D2 is connected with the non-inverting terminal of the op-amp U11, and the negative electrode of the photo detector D2 is connected with the inverting terminal of the op-amp U11; the resistor R20 is connected in parallel with the feedback capacitor C25 and is respectively connected to the inverting terminal and the output terminal of the operational amplifier U11; the output end of the operational amplifier U11 is connected with a resistor R16;
wherein, the resistor R20 and the operational amplifier U11 form a transimpedance amplifier; the op-amp U11 is powered by a power supply.
7. The water quality monitoring circuit according to any one of claims 1 to 6, wherein the colorimetric detection circuit unit or the fluorescent detection circuit unit comprises a photoelectric detector D3, an operational amplifier U10, a resistor R22, a feedback capacitor C26, a resistor R17, a resistor R26, a resistor R24 and an operational amplifier U6, wherein the positive electrode of the photoelectric detector D3 is connected with the non-inverting terminal of the operational amplifier U10, and the negative electrode of the photoelectric detector D3 is connected with the inverting terminal of the operational amplifier U10; the resistor R22 is connected in parallel with the feedback capacitor C26 and is respectively connected to the inverting terminal and the output terminal of the operational amplifier U10; the resistor R17 is respectively connected to the in-phase end of the operational amplifier U6 and the output end of the operational amplifier U10, the resistor R26 is respectively connected to the output end and the inverting end of the operational amplifier U6, and the resistor R24 is respectively connected to the inverting end of the operational amplifier U6 and the negative electrode of the power supply;
the resistor R22 and the operational amplifier U10 form a transimpedance amplifier, and the operational amplifier U6 and the operational amplifier U10 are powered by a power supply.
8. The water quality monitoring circuit of any one of claims 1-6, wherein the colorimetric detection circuit unit is electrically connected to the ADC data acquisition circuit unit via a first filter circuit unit.
9. The water quality monitoring circuit according to any one of claims 1 to 6, wherein the fluorescence detection circuit unit is electrically connected to the ADC data acquisition circuit unit by sequentially passing through the integration circuit unit and the second filter circuit unit.
10. A water quality analyzer characterized in that a water quality monitoring circuit according to any one of claims 1-9 is employed.
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| CN202211711198.5A CN116087179A (en) | 2022-12-29 | 2022-12-29 | Water quality monitoring circuit and water quality analyzer |
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| CN202211711198.5A CN116087179A (en) | 2022-12-29 | 2022-12-29 | Water quality monitoring circuit and water quality analyzer |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117420091A (en) * | 2023-12-19 | 2024-01-19 | 河北德润厚天科技股份有限公司 | Method and equipment for detecting quality of purified water |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117420091A (en) * | 2023-12-19 | 2024-01-19 | 河北德润厚天科技股份有限公司 | Method and equipment for detecting quality of purified water |
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