A portable water quality turbidity detection device

Abstract

The application discloses a portable water quality turbidity detection device, and aims at the problems of photosensitivity, existence of dark current, larger test error, higher use cost and sampling of weak voltage signal by the circuit in the existing portable water quality turbidity meter. The incident light generated by the light source generating circuit is evenly divided into two paths by a 1 / 2 splitter, and then is transmitted into standard water and measured water respectively. The current signals are converted into voltage signals by photoelectric detectors and current-voltage converters respectively, and are connected to the voltage control end of a high-precision voltage-controlled crystal oscillator through an alternative switch. The high-precision voltage-controlled crystal oscillator is used for frequency conversion, and then the standard water frequency and the measured water frequency are measured by a signal frequency measurement module. Then, the turbidity of the measured water is calculated by a data processing module, and is output to a display circuit for display. The application eliminates the influence of the dark current and is not easily affected by the external environment light, has higher precision, avoids the sampling circuit with higher use cost for sampling of weak voltage signals, and can obtain the turbidity of the measured water in real time.

Description

Technical Field

[0001] This invention belongs to the field of water quality testing technology, and more specifically, relates to a portable water turbidity testing device. Background Technology

[0002] Water turbidity detection (measurement) is an important indicator in water quality testing, water treatment, and environmental protection. It is not only related to people's health and safety but also closely linked to public health, environmental ecology, water resource management, and social stability. Therefore, the detection of water turbidity is of great significance.

[0003] The main methods for detecting (measuring) water turbidity include turbidimetry, light scattering, and transmittance measurement. Transmittance measurement estimates turbidity by measuring the attenuation of transmittance; its principle is as follows:

[0004] When a beam of parallel light propagates through transparent water, if there are no suspended particles, the beam will not change direction as it travels in a straight line. However, if there are suspended particles, regardless of whether the particles are transparent or not, the beam will change direction upon encountering them, resulting in scattered light in various directions. The more particles present, i.e., the higher the turbidity, the greater the scattering effect on the beam. Therefore, the turbidity of the water can be obtained by detecting the light intensity before and after the light passes through it.

[0005] The turbidity of the water body being measured is defined as... The incident light intensity is The intensity of the scattered light is The inherent parameters of the testing instrument are The optical path length of the sample cell is Particles in the tested water body The following relationship exists between them:

[0006] (1)

[0007] Obviously, when light enters a water sample, the particles that constitute turbidity scatter the light, and the intensity of the scattered light is proportional to the turbidity of the water sample.

[0008] In practice, measuring light intensity always requires converting it into an electric current using a photodetector. This is because photocurrent... The photocurrent is very weak, so a transimpedance amplifier (TIA) is needed to amplify it. When converted to voltage, the conversion relationship is as follows:

[0009] (2)

[0010] in, This is the feedback resistor for the transimpedance amplifier. The wavelength of light This refers to the quantum effect of photoelectric conversion. This represents light intensity.

[0011] Calculate using formula (2) and Substituting into formula (1), the turbidity of the water body being measured can be obtained.

[0012] Existing turbidity meters based on optical measurement methods generate emitted light using photodiodes or laser tubes. Turbidity information is obtained by sensing the intensity of the scattered light after the emitted light passes through the water body using a PN junction-based photoelectric sensor. This PN junction-based photoelectric sensor is made of semiconductor materials, exhibits photosensitivity, and contains dark current. This dark current is obviously converted into voltage by the TIA (Turbidity Assay), and the voltage corresponding to the dark current is included in the final converted voltage of the TIA. However, the photoelectric sensor is highly sensitive to ambient light, resulting in significant measurement errors. Furthermore, since this detection technology directly samples the converted voltage corresponding to turbidity, and this voltage is often a weak signal, a costly circuit for sampling this weak voltage signal is required to ensure measurement accuracy. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of the prior art and provide a portable water turbidity detection device to avoid the problem that the PN junction-based photoelectric sensor is sensitive to external ambient light and thus affects the test accuracy. At the same time, it avoids the use of expensive sampling circuits that sample weak voltage signals.

[0014] To achieve the above-mentioned objective, the portable water turbidity detection device of the present invention is characterized by comprising:

[0015] Light source generating circuit, used to generate incident light ;

[0016] Standard water sample collection tubes are used to store standard water samples;

[0017] The water sample collection tube is used to store the water sample being tested.

[0018] Its characteristic is that it further includes:

[0019] A 1 / 2 beam splitter is used to split the incident light generated by the light source generation circuit. The incident light is divided into two equally distributed incident beams. Among them, incident light The incident light was irradiated into the sampling tube of the standard water sample. The light is irradiated into the sampling tube of the water sample to be tested, and after passing through both the standard water sample and the water sample to be tested, the output is the transmitted light of the standard water sample. Transmitted light of the water body being measured ;

[0020] Two photodetectors with identical parameters, one of which is used to transmit light from a standard body of water. Converted to standard water body photocurrent signal Another photodetector is used to transmit light through the water body being measured. Converted into photocurrent signal of the water body being measured ;

[0021] Two current / voltage conversion circuits with identical parameters, one of which converts the standard water body photocurrent signal... Convert standard water body voltage signal Another current / voltage conversion circuit will measure the photocurrent signal of the water body. Converted into voltage signal of the water body being measured ;

[0022] A 2-to-1 switch, with its two input terminals connected to a standard water body voltage signal. and the voltage signal of the water body being measured And select one voltage signal output;

[0023] A high-precision voltage-controlled crystal oscillator with voltage-controlled frequency modulation has its voltage control terminal connected to the output terminal of a two-to-one switch, converting the voltage signal output by the two-to-one switch into a frequency signal.

[0024] The signal frequency measurement module is used to measure the frequency of the frequency signal output by a high-precision voltage-controlled crystal oscillator.

[0025] When the two-way switch selects the standard water body voltage signal During the conversion, the frequency measured by the signal frequency measurement module is the standard water body frequency. When the two-way switch selects the voltage signal of the water body being measured During the conversion, the frequency measured by the signal frequency measurement module is the frequency of the water body being measured. ;

[0026] The data processing module is used to process data according to the standard water body frequency. and the frequency of the water body being measured Calculate the turbidity of the water body being tested. :

[0027] (3)

[0028] in, These are inherent parameters of the system. The rate at which the frequency changes with the voltage-controlled voltage;

[0029] The display module is used to display the turbidity of the water being measured in real time. .

[0030] The objective of this invention is achieved as follows.

[0031] This invention provides a portable water turbidity detection device. Addressing the problems of existing portable water turbidity meters, whose photoelectric sensors are typically made of semiconductor materials, exhibiting photosensitivity and dark current, with the voltage corresponding to this dark current included in the conversion voltage, and also showing sensitivity to ambient light, resulting in significant testing errors, as well as the issue of using costly circuits to sample weak voltage signals, this invention utilizes a 1 / 2 beam splitter to separate the incident light generated by the light source generation circuit. The incident light is divided into two equally distributed incident beams. After passing through a standard water body, the signal is converted into a photocurrent signal of the standard water body using a photodetector. Then, a current-to-voltage converter is used to convert it into a standard water body voltage signal. The other path transmits the signal through the water body being measured, and then converts it into a photocurrent signal of the water body using a photodetector. Then, a current-to-voltage converter is used to convert it into a voltage signal of the water body being measured. The parameters of the two photodetectors and their voltage conversion circuits are identical. Then, the standard water body voltage signal... Voltage signal of the water body being measured The voltage is connected to the voltage control terminal of a high-precision voltage-controlled crystal oscillator via a two-to-one switch. The high-precision voltage-controlled crystal oscillator then processes the voltage signal from the standard water body. Voltage signal of the water body being measured Frequency conversion is performed, and then the standard water body frequency is measured by the signal frequency measurement module. Frequency of the water body being measured The data processing module is based on the standard water body frequency. Frequency of the water body being measured Calculate the turbidity of the water body being tested. The output is sent to the display circuit for display.

[0032] Compared with existing portable water turbidity analyzers, the portable water turbidity detection device of this invention has the following technical advantages:

[0033] 1. This invention uses a high-precision voltage-controlled crystal oscillator to convert the standard water body voltage signal... Voltage signal of the water body being measured Convert the values ​​to frequencies, then subtract them to obtain the frequency difference, and use this difference to calculate the turbidity of the water being measured. It eliminates the effects of dark current and is less susceptible to the influence of ambient light.

[0034] 2. This invention measures the turbidity of the water body by converting voltage into frequency. Frequency (time) is currently the physical quantity with the highest testing accuracy. Therefore, this invention has higher accuracy than the direct measurement by traditional photoelectric sensors based on semiconductors. At the same time, it avoids the use of sampling circuits that sample weak voltage signals, which are costly.

[0035] 3) This invention splits the incident light into two equal paths using a 1 / 2 beam splitter, simultaneously obtaining a voltage signal that reflects the light intensity. A two-to-one switch is used to select one path for voltage-frequency conversion and frequency measurement, avoiding the need for switching of the incident light. This allows for real-time frequency measurement and real-time determination of the turbidity of the water being measured. Attached Figure Description

[0036] Figure 1 This is a principle block diagram of a specific embodiment of the portable water turbidity detection device of the present invention;

[0037] Figure 2 This is a schematic diagram of a specific embodiment of the portable water turbidity detection device of the present invention;

[0038] Figure 3 yes Figure 2 The diagram shows a three-dimensional assembly of a portable water turbidity detection device. Detailed Implementation

[0039] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0040] Figure 1 This is a principle block diagram of a specific embodiment of the portable water turbidity detection device of the present invention.

[0041] In this embodiment, as Figure 1 As shown, the portable water turbidity detection device of the present invention includes a light source generating circuit 1, a 1 / 2 beam splitter 2, a standard water sample sampling tube 3, a sample sampling tube for the water to be tested 4, two photodetectors 501 and 502 with identical parameters, two current / voltage conversion circuits 601 and 602 with identical parameters, a two-to-one switch 7, a high-precision voltage-controlled crystal oscillator 8 with voltage-controlled frequency modulation, a signal frequency measurement module 9, a data processing module 10, and a display module 11.

[0042] Light source generating circuit 1 generates incident light The 1 / 2 beam splitter 2 splits the incident light generated by the light source generating circuit 1. The incident light is divided into two equally distributed incident beams. Among them, incident light The incident light was irradiated into the standard water sample sampling tube 3 containing the standard water sample. The light is irradiated into the water sample tube 4 containing the water sample to be tested. After passing through both the standard water sample and the water sample to be tested, the output is the transmitted light of the standard water sample. Transmitted light of the water body being measured .

[0043] Of the two photodetectors 501 and 502 with identical parameters, one photodetector 501 is used to transmit light from a standard water body. Converted to standard water body photocurrent signal Another photodetector 502 is used to transmit light through the water body being measured. Converted into photocurrent signal of the water body being measured .

[0044] In two current / voltage conversion circuits 601 and 602 with identical parameters, one current / voltage conversion circuit 601 converts the standard water body photocurrent signal. Convert standard water body voltage signal Another current / voltage conversion circuit 602 will measure the photocurrent signal of the water body. Converted into voltage signal of the water body being measured .

[0045] The two input terminals of the 2-to-1 switch 7 are respectively connected to the standard water body voltage signal. and the voltage signal of the water body being measured And select one voltage signal output to a high-precision voltage-controlled crystal oscillator 8 with voltage control frequency modulation.

[0046] The voltage control terminal of the high-precision voltage-controlled crystal oscillator 8 with voltage-controlled frequency modulation is connected to the output terminal of the two-to-one switch 7, converting the voltage signal output by the two-to-one switch 7 into a frequency signal.

[0047] Signal frequency measurement module 9 is used to measure the frequency of the frequency signal output by the high-precision voltage-controlled crystal oscillator 8. When the two-way switch 7 selects the standard water body voltage signal... During the conversion, the frequency measured by signal frequency measurement module 9 is the standard water body frequency. When the two-to-one switch 7 selects the voltage signal of the water body to be measured During the conversion, the frequency measured by the signal frequency measurement module 9 is the frequency of the water body being measured. .

[0048] Data processing module 10 based on standard water body frequency and the frequency of the water body being measured Calculate the turbidity of the water body being tested. :

[0049] (4)

[0050] in, These are inherent parameters of the system. The rate at which the frequency changes with the voltage-controlled voltage.

[0051] The display module 11 is used to display the turbidity of the water being measured in real time. .

[0052] In practical implementation, after the portable water turbidity detection device of the present invention is powered on, two incident lights... The switch can be turned off independently, and the 1 / 2 beam splitter 2 can also be switched independently. The photodetector 501 containing the standard water sample and the photodetector 502 containing the tested water sample only sense the transmitted light of their respective branches and are not affected by other optical paths.

[0053] The output frequency of a voltage-controlled crystal oscillator (VCXO) is typically based on its center frequency and controlled by a voltage-controlled voltage. Its output frequency... The expression is:

[0054] (5)

[0055] in, For the center frequency, It is a voltage-controlled voltage. The rate at which the frequency changes with the voltage-controlled voltage.

[0056] After the portable water turbidity detection device of this invention is powered on, the light source generating circuit 1 is turned off, and the two-way switch 7 is connected to the output terminal of the current / voltage conversion circuit 601 of the standard water sample circuit. At this time, the voltage corresponding to the dark current of the photodetector 501 is... The output frequency of the high-precision voltage-controlled crystal oscillator 8 is then... for:

[0057] (6)

[0058] Therefore, the frequency change caused by dark current can be obtained as follows:

[0059] (7)

[0060] Turn on the light source generating circuit 1, and connect the two-way switch 7 to the output terminal of the current / voltage conversion circuit 601 of the standard water body circuit. At this time, the voltage control voltage of the high-precision voltage-controlled crystal oscillator 8 includes the voltage corresponding to the dark current of the photodetector 501. And the voltage after light passes through the photodetector 501 and the current / voltage conversion circuit 601 after passing through the standard water sample. The output frequency of the high-precision voltage-controlled crystal oscillator 8 is then... for:

[0061] (8)

[0062] When the two-way switch 7 is switched to the output terminal of the current / voltage conversion circuit 602 for the water sample being tested, the voltage-controlled voltage of the high-precision voltage-controlled crystal oscillator 8 includes the voltage corresponding to the dark current of the photodetector 502. And the voltage after light passes through the photodetector 502 and the current / voltage conversion circuit 602 after the light passes through the water sample being tested. The output frequency of the high-precision voltage-controlled crystal oscillator 8 is then... for:

[0063] (9)

[0064] From formulas (8) and (9), the voltage change caused by the turbidity of the water sample being tested can be obtained as follows:

[0065] (10)

[0066] Voltage difference between the two branches of the standard water body and the water body being tested , and the turbidity of the water body being tested The following relationship exists:

[0067] (11)

[0068] in, These are inherent parameters of the system.

[0069] Substituting formula (10) into formula (11) will give the turbidity of the water body being measured. :

[0070] (12)

[0071] Figure 2 , 3 These are a structural schematic diagram and a three-dimensional assembly diagram of a specific embodiment of the portable water turbidity detection device of the present invention.

[0072] In this embodiment, the portable water turbidity detection device of the present invention is a cylindrical tube. The top and bottom surfaces of the cylindrical tube are sealed. The upper part of the interior is the optical path detection section, which is designed from top to bottom. The middle part is the circuit processing section, and the bottom part is the battery section, which are arranged in sequence as follows:

[0073] The light source generating circuit 1 includes a light source switch button 101, a light source control circuit module 102, and a light source 103. The light source switch 101 is located on the top surface, and the light source control circuit 102 is located inside the top surface of the cylindrical tube. Below the control circuit 102 is the light source 103, and below the light source 103 is a half-splitter 2. When the light source switch button 101 is turned on, the light source control circuit module 102 is activated, causing the light source 103 to generate incident light. The incident light is directed downwards into beam splitter 2, which then splits the incident light into beams. The incident light is divided into two downward-facing paths, one on the left and one on the right. Below the 1 / 2 beam splitter 2, on the left and right sides, are placed standard water sample tube 3 and the sample tube 4 of the water to be tested, respectively. The standard water sample tube 3 and the sample tube 4 of the water to be tested are placed in the two cylindrical spaces of the water sample chamber 12. In this way, the photodetectors of the standard water sample and the sample tube 4 of the water to be tested only sense the light of their own branch and are not affected by other optical paths.

[0074] Incident light The incident light is directed downwards into the standard water sample collection tube 3, which contains the standard water sample. The light from the sampling tube 4, which contains the water sample to be tested, is directed downwards. After passing through both the standard water sample and the water sample to be tested, the output light is the transmitted light from the standard water sample. Transmitted light of the water body being measured .

[0075] Below the standard water sample tube 3 and the sample tube 4 of the tested water sample are two photodetectors 501 and 502 with identical parameters, respectively. The transmitted light from the standard water sample... Transmitted light of the water body being measured The light shines downwards onto photodetectors 501 and 502 respectively. Photodetector 501 is used to transmit the light from the standard water body. Converted to standard water body photocurrent signal Another photodetector 502 is used to transmit light through the water body being measured. Converted into photocurrent signal of the water body being measured .

[0076] Below the two photodetectors 501 and 502 with identical parameters are two current-to-voltage conversion circuits 601 and 602 with identical parameters, respectively. One of the current-to-voltage conversion circuits 601 converts the photocurrent signal of the standard water body... Convert standard water body voltage signal Another current / voltage conversion circuit 602 will measure the photocurrent signal of the water body. Converted into voltage signal of the water body being measured .

[0077] The two-way selector switch 7 is located below the two current / voltage conversion circuits 601 and 602 with identical parameters, and is connected to the external two-way selector switch button 13 for the user to select the standard water body voltage signal. Voltage signal of the water body being measured Which voltage signal is input to the voltage control terminal of the high-precision voltage-controlled crystal oscillator 8 with voltage control frequency modulation?

[0078] The signal frequency measurement module 9 measures the frequency of the output signal from the high-precision voltage-controlled crystal oscillator 8. Then, the measured standard water body frequency is used. Frequency of the water body being measured The data is sent to the data processing module 10 to calculate the turbidity of the water body being tested. The turbidity of the water being tested is then sent to the display module 11 for real-time display. .

[0079] In addition, there is a data output module 14, which is connected to the data processing module 10, for outputting measurement data. A battery pack 15 is located at the bottom of the entire portable water turbidity detection device, with a charging port 16 on the corresponding side. The output of the battery pack 15 is connected to each component via a power switch button 17 to provide power.

[0080] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A portable water turbidity detection device, characterized in that, include: Light source generating circuit, used to generate incident light ; Standard water sample collection tubes are used to store standard water samples; The water sample collection tube is used to store the water sample being tested. A 1 / 2 beam splitter is used to split the incident light generated by the light source generation circuit. The incident light is divided into two equally distributed incident beams. Among them, incident light The incident light was irradiated into the sampling tube of the standard water sample. The light is irradiated into the sampling tube of the water sample to be tested, and after passing through both the standard water sample and the water sample to be tested, the output is the transmitted light of the standard water sample. Transmitted light of the water body being measured ; Two photodetectors with identical parameters, one of which is used to transmit light from a standard body of water. Converted to standard water body photocurrent signal Another photodetector is used to transmit light through the water body being measured. Converted into photocurrent signal of the water body being measured ; Two current / voltage conversion circuits with identical parameters, one of which converts the standard water body photocurrent signal... Convert standard water body voltage signal Another current / voltage conversion circuit will measure the photocurrent signal of the water body. Converted into voltage signal of the water body being measured ; A 2-to-1 switch, with its two input terminals connected to a standard water body voltage signal. and the voltage signal of the water body being measured And select one voltage signal output; A high-precision voltage-controlled crystal oscillator with voltage-controlled frequency modulation has its voltage control terminal connected to the output terminal of a two-to-one switch, converting the voltage signal output by the two-to-one switch into a frequency signal. The signal frequency measurement module is used to measure the frequency of the frequency signal output by a high-precision voltage-controlled crystal oscillator. When the two-way switch selects the standard water body voltage signal During the conversion, the frequency measured by the signal frequency measurement module is the standard water body frequency. When the two-way switch selects the voltage signal of the water body being measured During the conversion, the frequency measured by the signal frequency measurement module is the frequency of the water body being measured. ; The data processing module is used to process data according to the standard water body frequency. and the frequency of the water body being measured Calculate the turbidity of the water body being tested. : ； in, These are inherent parameters of the system. The rate at which the frequency changes with the voltage-controlled voltage; The display module is used to display the turbidity of the water being measured in real time. ; The portable water turbidity detection device is a cylindrical tube. The top and bottom surfaces of the tube are sealed. The upper part of the interior contains the optical detection section, designed from top to bottom. The middle part contains the circuit processing section, and the bottom contains the battery section, in that order: The light source generating circuit includes a light source switch button, a light source control circuit module, and a light source. The light source switch is located on the top surface, and the light source control circuit is located inside the top surface of the cylindrical tube. Below the control circuit is the light source, and below the light source is a half beam splitter. When the light source switch button is turned on, the light source control circuit module is activated, causing the light source to generate incident light. The incident light is directed downwards into the half beam splitter, which then splits the incident light... The incident light is divided into two downward-facing paths, one on the left and one on the right. Below the 1 / 2 spectrometer, on the left and right, are placed standard water sample tubes and the sample tubes to be tested, respectively. The standard water sample tubes and the sample tubes to be tested are placed in the two cylindrical spaces of the water sample chamber. Incident light The incident light is directed downwards into the sampling tube containing the standard water sample. The light is directed downwards into the sampling tube containing the water sample to be tested. After passing through both the standard water sample and the water sample to be tested, the output light is the transmitted light from the standard water sample. Transmitted light of the water body being measured ; Below the standard water sample tube and the sample tube of the water being tested are two photodetectors with identical parameters. The standard water sample transmits light... Transmitted light of the water body being measured The light is directed downwards and illuminates photodetectors, one of which is used to convert the transmitted light from the standard water body. Converted to standard water body photocurrent signal Another photodetector is used to transmit light through the water body being measured. Converted into photocurrent signal of the water body being measured ; Below the two photodetectors with identical parameters are two current-to-voltage conversion circuits with identical parameters, one of which converts the photocurrent signal of the standard water body into voltage. Convert standard water body voltage signal Another current / voltage conversion circuit will measure the photocurrent signal of the water body. Converted into voltage signal of the water body being measured ; The two-way selector switch is located below two current / voltage conversion circuits with identical parameters and is connected to an external two-way selector button, allowing the user to select a standard water voltage signal. Voltage signal of the water body being measured Which voltage signal is input to the voltage control terminal of the high-precision voltage-controlled crystal oscillator with voltage-controlled frequency modulation? The signal frequency measurement module measures the frequency of the output signal from a high-precision voltage-controlled crystal oscillator, and then uses the measured standard water body frequency. Frequency of the water body being measured The data is sent to the data processing module to calculate the turbidity of the water body being tested. The data is then sent to the display module to show the turbidity of the water being tested in real time. .

2. The portable water turbidity detection device according to claim 1, characterized in that, It also includes a data output module, which is connected to the data processing module and is used to output measurement data; The portable water turbidity detection device has a battery pack at the bottom and a charging port on the side. The battery pack output is connected to each part via a power switch button to provide power.

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