CN103323426B - Threshold laser liquid turbidity measuring device and method - Google Patents
Threshold laser liquid turbidity measuring device and method Download PDFInfo
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- CN103323426B CN103323426B CN201310244241.6A CN201310244241A CN103323426B CN 103323426 B CN103323426 B CN 103323426B CN 201310244241 A CN201310244241 A CN 201310244241A CN 103323426 B CN103323426 B CN 103323426B
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Abstract
The invention discloses a threshold laser liquid turbidity measuring device and method. The measuring device comprises a light source module, a light path transmission and photovoltaic conversion module, a signal conditioning module, a signal acquisition and processing module, a controlled signal generating module, a flange, an optical focalizer and standard liquid. The measuring method comprises the following steps of: carrying out high speed modulation on a laser by a pulser in the controlled signal generating module, calculating transmission time of pulsed light in optical fibers, filtering direct current interference wave by a band-pass filtering circuit, filtering interference signals with same frequency and different time in the manner that an adjustable delayer controls the opening and closing of a threshold circuit, and selecting useful signals, thus realizing the accurate measurement on liquid turbidity. The measuring device provided by the invention has the advantages that the structure is simple, the stability is high, the realization is easy, the liquid turbidity measurement accuracy and sensitivity are effectively improved, and the technical guarantee for on-line water quality monitoring is provided.
Description
Technical field
The present invention relates to a kind of thresholding formula laser liquid turbidity meter and measuring method, belong to environmental monitoring technology field.
Background technology
Along with China's industry, agriculture development, a large amount of industrial and agricultural wastewaters, sewage discharge to rivers,lakes and seas, simultaneously, 80% unprocessed direct discharge is about had in China's city domestic sewage, samll cities and towns and vast domestic sewage in rural areas are in unordered emissions status especially, and this makes the water quality deterioration in many areas.It is healthy that these have threatened people, becomes one of main Environmental Problems of puzzlement Economic Sustainable Development of China.Therefore need badly and real time on-line monitoring is carried out to water quality, for environmental improvement department provides foundation and reference.Turbidity is one of water quality five parameter, is an important indicator of Water Pollution Monitoring and body eutrophication.Therefore, the accurate measurement of water turbidity, development and drinking water safety etc. for monitoring water environment, culture fishery all have very important significance.
The measurement of external liquid turbidity from the thirties in last century just, defined sizable research and development, production scale and industrial chain.The 2100A type Laboratory Turbidimeter that such as U.S. HACH company released the end of the eighties, use tungsten sodium lamp as light source, measurement range is 0-1000NTU, measuring accuracy is to 0.01, the end of the nineties, company released again four sections of Novel laboratory turbidimeters, all have employed multiple silicon photo diode for receiving beam, from different perspectives receiving scattered light signal, thus improve measurement range [1-4]; The CUS31/41 type turbidimeter that E+H company of Germany releases is online high-end turbidity probe tip, and indoor design has two detection optical channels, a channel measurement 90 degree scattered light, another channel measurement forward scattering light, and measurement range is 0-9999NTU, and precision can reach 0.01[5]; 7997 serial turbidimeters of ABB KENT company of Britain have Four types: 7997-200 types are flow type, 90 degree of scattering principles, maximum range is 0-250NTU, minimum is 0-25NTU, and 7997-201 & 202(202 are without washer) type is flow type, 90 degree of scattering principles, low turbidity is measured, maximum range is 0-30NTU, and minimum is 0-1NTU, generally can be used for the pure water that survey turbidity is less than 1NTU; 7997-300 types are flow type, turbidimetry in transmission. maximum range is 0-500NTU; 7997-400(405) type is immersion, transmission high concentrtion is measured, and is applicable to open type pipeline and container is installed and used, and maximum range is 0-1000NTU[6].The research of domestic Turbidity measurement technology is started late, and technical feature has very large gap compared with external turbidimeter, and through the researches of technique of nearly 10 years and Importing Foreign Advanced Technology experience, domestic turbidimeter parameters index improves a lot.The Laboratory Turbidimeter that such as Feihua, Xiamen instrument company is proposed TSZ series has adopted the scattered light that many silicon photo diodes detect multi-angle simultaneously, improve measurement range (0-4000NTU) and measuring accuracy (0.001), in Laboratory Turbidimeter, measurement range is higher at home, but it adopts tungsten lamp as light source, optical design complexity [7]; The online turbidimeter of WT-OT3 series of Wuhan Water Company for light source with infrared monochromatic light, adopts back scattering measuring principle, and uses optical fiber to realize transmission and the detection of light, eliminate the interference in light path; Measurement range is 10-2000NTU, measuring accuracy is 3%, for flowing pipeline general formula and plug-in type installation.The reception back scattering light signal adopted, so measurement lower limit is restricted (not meeting ISO7027 standard), and does not measure the function of suspended solid, and measuring accuracy is compared with sensitivity external lower [8].
At present, various turbidimetry system bulk both domestic and external is larger, be difficult to realize the online turbidimetry of small space particularly under mal-condition, have again in domestic nephelometer, the precision measured all is difficult to compared with external product with sensitivity, therefore designs a kind of high precision, highly sensitive liquid turbidity measuring system is a key content of the present invention.
List of references:
[1]Hach Company,2100-N laboratory turbidimeter application instruction.
[2]Hach Company,2100-AN laboratory turbidimeter application instruction.
[3]Hach Company,2100-NIS laboratory turbidimeter application instruction.
[4]Hach Company,2100-ANIS laboratory turbidimeter application instruction.
[5]E+H Company,Cus31/41online turbidimeter application instruction.
[6]ABB-KENT Company,7997-200online turbidimeter application instruction.
[7] Feihua, Xiamen finite instrument company, TSZ serial experiment room turbidimeter instruction manual.
[8] Wuhan water Instrument Corporation, the online turbidimeter instruction manual of WT-OT3 series.
Summary of the invention
Fundamental purpose of the present invention is to provide a kind of thresholding formula laser liquid turbidity meter and measuring method, to solve existing turbidimetry technology especially precision and the low problem of sensitivity in low turbidity measuring technique.
The technical solution used in the present invention is: a kind of thresholding formula laser liquid turbidity meter, comprise light source module 100, optic path and photoelectric conversion module 200, Signal-regulated kinase 300, Signal acquiring and processing module 400, controllable signal generation module 500, second flange 11B, optical fiber focuser 12, normal fluid 13; Light source module 100 comprises Laser Control System 101, laser instrument 102; Optic path and photoelectric conversion module 200 comprise three fiber port circulators 201, photodetector 202, first flange 11A, three-flange 11C; Signal-regulated kinase 300 comprises pre-amplification circuit 301, second amplifying circuit 302, bandwidth-limited circuit 303, threshold circuit 304; Signal acquiring and processing module 400 comprises signal acquisition circuit 401, controller 402, data display circuit 403, memory circuit 404; Controllable signal generation module 500 comprises adjustable time delay 501, pulse producer 502; Optical fiber focuser 12 is connected with three fiber port circulators 201 by the second flange 11B;
A. described Laser Control System 101 is after pulse producer 502 is modulated, and control the light modulated 20 that laser instrument 102 launches cycle and adjustable pulse width, described laser instrument 102 adopts high-speed pulse to modulate, and minimum pulse width is wanted to reach 10ps;
B. described laser instrument 102 utilizing emitted light enters into three port circulator 201 first port 201A through the first flange 11A, then optical fiber focuser 12 is transferred to from the second port 201B of three port circulators 201 through the second flange 11B, from the illumination of optical fiber focuser 12 outgoing to normal fluid 13, part rear orientation light after the scattering of normal fluid 13 endoparticle thing feeds back to optical fiber focuser 12, three fiber port circulators 201 are entered into by the second flange 11B, and enter into photodetector 202 from the 3rd port 201C of three fiber port circulators 201 through three-flange 11C, photodetector 202 realizes the conversion of light signal to low current signal,
C. the low current signal that the described pre-amplification circuit 301 pairs of photodetectors 202 are changed carries out electric current to the conversion of voltage and amplification, second amplifying circuit 302 pairs of pre-amplification circuit 301 output signals carry out secondary amplification, meet-10V-+10V the requirement of signal acquisition circuit 401 voltage range 30A, bandwidth-limited circuit 303 realizes pulse producer 502 and produces passing through of frequency signal, the signal amplitude being different from pulse producer frequency is subject to large decay or suppresses 30B, threshold circuit 304 can realize producing signal 33 to normal fluid 13 rear orientation light and select, to having with the asynchronous AC influence signal 31 of frequency, 32, 35 carry out isolation 30C),
D. described signal acquisition circuit 401 realizes the conversion of simulating signal to digital signal, controller 402 realizes the control of Acquisition Circuit 401, digital signal processing, magnitude of voltage to the conversion of actual liquid turbidity, the coefficient that memory circuit 404 storage voltage value is changed to actual liquid turbidity, data display circuit 403 shows the turbidity value of liquid;
E. described adjustable time delay 501 is synchronous with pulse producer 502 signal, described adjustable time delay 501 sends enable signal and starts threshold circuit 304 after time delay Δ t1, threshold circuit 304 is opened, signal now from bandwidth-limited circuit 303 starts to be selected, after opening the Δ t2 time, signal is chosen complete, and threshold circuit 304 cuts out, threshold circuit 304 down periods, the signal from bandwidth-limited circuit 303 is all isolated.
In described optic path and photoelectric conversion module 200, the transmission medium of light adopts single-mode fiber, has long transmission distance, loss is low, antijamming capability is strong, advantage that security is high.
Described optic path and photoelectric conversion module 200 adopt the detecting structure of all-fiber formula, and probe size is less, and the liquid turbidity being applicable to small space is measured.
A kind of thresholding formula laser liquid turbidimetry method, performing step is as follows:
A. light is issued to from laser instrument 102 and reaches normal fluid 13, and then being arrived transmission time of photodetector 202 by liquid-scattering is a fixed amount T;
B. arranging pulse producer 502 to produce width be T1 and cycle is the waveform 20 of T2, and the time delay arranging adjustable time delay 501 is Δ t1=T, and delay time length is Δ t2=(2 ~ 3) * T1;
C. the second amplifying circuit 302 output waveform 30A in signal conditioning circuit 300, comprises three parts at output waveform 30A: AC influence signal, and its frequency is identical with the modulating light frequency that pulse producer 502 produces; DC influence signal 34 all exists in whole cycle T 2; The voltage waveform 33 of the rear orientation light conversion that normal fluid 13 produces;
D. the output signal of second amplifying circuit 302 is by the output waveform 30B after bandwidth-limited circuit 303, and DC influence ripple 34 is filtered out, and AC influence signal 31,32,35 still exists;
E. adjustable time delay 501 is after time delay Δ t1, send enable signal to threshold circuit 304, threshold circuit 304 is opened, after opening the Δ t2 time, threshold circuit 304 cuts out, the voltage waveform 33 of the rear orientation light conversion that the normal fluid 13 selected produces is the magnitude of voltage of normal fluid 13 rear orientation light conversion, and AC influence signal 31,32,35 is isolated;
F. controller 402 collects the magnitude of voltage of threshold circuit 304 output by signal acquisition circuit 401, and is saved in memory circuit 404 after magnitude of voltage being made maximum-minimum value removal and average value processing;
G. for the standard solution of different turbidity, measure the magnitude of voltage that its scattered light produces, the data of magnitude of voltage and standard solution turbidity carried out least-squares algorithm linear fitting, obtains the relation of turbidity and magnitude of voltage:
y=kx+b （1）
Wherein: x: magnitude of voltage, unit mV;
Y: titer turbidity value, unit NTU;
K, b: least-squares algorithm linear fitting coefficient;
H. fitting coefficient is saved in memory circuit (404), when measuring liquid turbidity, the magnitude of voltage obtained is updated in formula (1), obtains liquid turbidity value.
Principle of the present invention: a kind of thresholding formula laser liquid turbidity meter and measuring method, comprise light source module, optic path and photoelectric conversion module, Signal-regulated kinase, Signal acquiring and processing module, controllable signal generation module, flange, optical fiber focuser, normal fluid, as shown in Figure 1.Light source module comprises Laser Control System and laser instrument, for generation of the light of certain frequency and pulsewidth, as shown in Figure 2, optic path and photoelectric conversion module comprise three fiber port circulators, photodetector, flange, for the conversion to electric signal of the transmission of light path and light, be specially the light that three fiber port circulator first port accepts are launched from laser instrument, and by the second port transmission to optical fiber focuser, optical fiber focuser is irradiated on normal fluid after focusing on light, light after normal fluid back scattering enters into again optical fiber focuser, photodetector is entered into by the 3rd port of three fiber port circulators, photodetector realizes the conversion of light signal to low current signal, Signal-regulated kinase comprises pre-amplification circuit, second amplifying circuit, bandwidth-limited circuit and threshold circuit, for the conversion of low current signal to voltage signal, amplify and process, being specially pre-amplification circuit core devices is low noise, high input impedance direct current amplifier, realize the conversion to low current signal and amplification, as shown in Figure 3A, second amplifying circuit carries out secondary amplification to pre-amplification circuit output signal, meet the requirement of signal acquisition circuit voltage range, bandwidth-limited circuit realizes passing through of the frequency waveform of pulse producer generation, other frequency signal amplitude attenuation or suppression are as shown in Figure 3 B, threshold circuit is the key component of whole system, its quality is directly connected to precision and the sensitivity of system, the signal behavior that main realization produces normal fluid rear orientation light, to other same frequency but have certain hour interval signal isolation, as shown in Figure 3 C.The start-up time delay of threshold circuit need be determined according to the transmission time of whole light path, the pulsewidth that the effective acting time of threshold circuit need produce according to pulse producer is determined, generally get the pulsewidth of 2 ~ 3 times, need the start-up time delay of threshold circuit and effective acting time precisely to determine, otherwise garbage signal can be have selected isolated useful signal; Signal acquiring and processing module comprises signal acquisition circuit, controller, data display circuit, memory circuit, for the digital filtering process of signal, magnitude of voltage is to the conversion of turbidity value, data store and display, be specially signal acquisition circuit and realize the conversion of simulating signal to digital signal, controller realizes the control of Acquisition Circuit, digital signal processing, collection magnitude of voltage are changed to actual liquid turbidity, the turbidity value of data display circuit display liquid, memory circuit storage voltage value is to actual liquid turbidity conversion parameter and liquid turbidity value; Controllable signal generation module comprises adjustable time delay, pulse producer, the break-make of the light produced for modulated laser and control threshold circuit, be specially pulse producer by the radiative pulsewidth of modulated laser and frequency, adjustable time delay is synchronous with pulse producer, controls the break-make of threshold circuit; For the standard solution of different turbidity, measure the magnitude of voltage that its scattered light produces, the data of magnitude of voltage and standard solution turbidity are carried out least-squares algorithm linear fitting, obtain the linear relationship of turbidity and magnitude of voltage, and fitting coefficient is saved in memory circuit, when measuring liquid turbidity, the magnitude of voltage obtained is updated in relational expression, obtains liquid turbidity value.
The present invention's beneficial effect is compared with prior art:
(1) optical system of the present invention can carry out pulsewidth and the cycle of dynamic modulation laser instrument luminescence by pulse producer, and determine that adjustable time delay controls the break-make of threshold circuit by the time calculating optic path, thus the signal that fluid to be measured scattered light produces is selected, substantially increase the measuring accuracy of system;
(2) in optical system of the present invention, Optical Maser System adopts high-speed pulse modulation, avoids environment temperature and pressure change to cause the random variation of laser phase, thus reduces external interference, improve the stability of system;
(3) optical transmission medium of the present invention adopts single-mode fiber, has long transmission distance, loss is low, antijamming capability is strong, advantage that security is high;
(4) bandwidth-limited circuit in signal conditioning circuit of the present invention can carry out effective filtering to DC noise signal and the signal being different from modulating light frequency, substantially increases the measuring accuracy of system;
(5) threshold circuit in signal conditioning circuit of the present invention can have same frequency to light modulated, but and light modulated have the signal at certain hour interval to shield, the reflected light of such as end face of flange, the reflected light of three port circulators.This threshold circuit effectively can catch the signal that liquid rear orientation light produces, and effective seizure of even single photon, so can significantly improve measuring accuracy and sensitivity;
(6) the present invention adopts the detecting structure of all-fiber formula, and probe size is less, and the liquid turbidity being applicable to small space is measured.
Accompanying drawing explanation
Fig. 1 is liquid turbidity measuring system schematic diagram of the present invention;
Fig. 2 is the schematic diagram of modulating pulse light of the present invention;
Fig. 3 A be of the present invention after two-stage amplifying circuit signal schematic representation;
Fig. 3 B be of the present invention after bandwidth-limited circuit signal schematic representation;
Fig. 3 C be of the present invention after threshold circuit signal schematic representation;
Fig. 4 is least-squares algorithm linear fitting schematic diagram of the present invention.
Embodiment
Below in conjunction with accompanying drawing, enforcement of the present invention is described in further detail.
Fig. 1 is a kind of thresholding formula laser liquid turbidity meter schematic diagram, comprises light source module 100, optic path and photoelectric conversion module 200, Signal-regulated kinase 300, Signal acquiring and processing module 400, controllable signal generation module 500, first flange 11A, the second flange 11B and three-flange 11C, optical fiber focuser 12, normal fluid 13.Light source module 100 comprises Laser Control System 101 and laser instrument 102, and Laser Control System 101 controls the light that laser instrument 102 launches certain frequency and pulsewidth after being modulated by pulse producer 502, optic path and photoelectric conversion module 200 comprise three fiber port circulators 201, photodetector 202, first flange 11A, for the conversion to electric signal of the transmission of light path and light, be specially three fiber port circulator 201 first port 201A and receive the light launched from laser instrument 102, and be transferred to optical fiber focuser 12 by the second port 201B, optical fiber focuser 12 is irradiated on normal fluid after focusing on light, optical fiber focuser 12 is entered into after normal fluid back scattering, photodetector 202 is entered into by the 3rd port 201C of three fiber port circulators 201, photodetector 202 realizes the conversion of light signal to low current signal, what wherein three fiber port circulators 201 adopted is polarization independence light ring machine, there is high-isolation, the advantage of low insertion loss and high return loss, be specially maximum insertion≤0.8dB, minimum isolation >=40dB, return loss >=50Db, optical fiber focuser has low insertion loss, the advantage of minimum echo loss, it has the function of receiving and dispatching in one, can either Emission Lasers to normal fluid, also the backward scattered light of normal fluid can be received, photodetector 202 adopts high sensitivity avalanche optoelectronic detecting module, its objective is the intensity that can detect faint scattered light single photon even, Signal-regulated kinase 300 comprises pre-amplification circuit 301, second amplifying circuit 302, bandwidth-limited circuit 303 and threshold circuit 304, for the conversion of low current signal to voltage signal, amplify and process, being specially pre-amplification circuit 301 core devices is low noise, high input impedance direct current amplifier, realize the conversion to low current signal and amplification, second amplifying circuit 302 pairs of pre-amplification circuit output signals carry out secondary amplification, meet the requirement of signal acquisition circuit voltage range-10V-+10V, bandwidth-limited circuit 303 realizes pulse producer and produces passing through of frequency waveform, other frequency signal amplitude attenuation or suppression, threshold circuit 304 is key components of whole system, main realization produces the selection of signal to normal fluid rear orientation light, to other same frequency there is the isolation of the signal at certain hour interval.The start-up time delay of threshold circuit 304 need be determined according to the transmission time of whole light path, the pulsewidth that the effective acting time of threshold circuit need produce according to pulse producer is determined, generally get 2-3 pulsewidth doubly, need the start-up time delay of threshold circuit and effective acting time precisely to determine, otherwise garbage signal can be have selected isolated useful signal, Signal acquiring and processing module 400 comprises signal acquisition circuit 401, controller 402, data display circuit 403, memory circuit 404, for the digital filtering process of signal, magnitude of voltage is to the conversion of turbidity value, data store and display, be specially signal acquisition circuit 401 and realize the conversion of simulating signal to digital signal, controller 402 realizes the control of Acquisition Circuit, digital signal processing, gather magnitude of voltage to change to actual liquid turbidity, data display circuit 403 shows the turbidity value of liquid, memory circuit 404 storage voltage value is to actual liquid turbidity conversion parameter and liquid turbidity value, controllable signal generation module 500 comprises adjustable time delay 501, pulse producer 502, for modulated laser and the break-make controlling threshold circuit, be specially pulse producer 502 launches certain pulsewidth and frequency light by modulated laser 102, adjustable time delay 501 is synchronous with pulse producer 502 signal, for controlling the break-make of threshold circuit 304.
Fig. 2 is the modulation signal schematic diagram that pulse producer produces.Its effect controls the light that Optical Maser System produces certain frequency and pulsewidth; Wherein modulating frequency f2=1/T2, the size of modulating frequency is determined at the transmission time T of optical fiber according to light, generally gets T2 >=1.5-2T, in order to avoid utilizing emitted light and scattered light produce interference in Optical Fiber Transmission.Such as laser instrument is L1 to the transmission range of the light of normal fluid, and normal fluid is L2 to the transmission range of the light of photodetector, then light is issued to from laser instrument and reaches normal fluid, and then being arrived transmission time of photodetector by liquid-scattering is a fixed amount T;
Fig. 3 A is the output waveform schematic diagram of the second amplifying circuit in signal conditioning circuit.Wherein 31,32,35 is AC influence ripples, result from the reflection of connectivity port, frequency is identical with the modulating light frequency that pulse producer produces, DC influence ripple 34, produces and parasitic light or be surround lighting, all exists in whole cycle T 2, the magnitude of voltage of the rear orientation light conversion that waveform 33 produces for normal fluid, frequency is identical with the modulating light frequency that pulse producer produces, and waveform 31,32,33,35 frequency is identical, but has certain time interval;
Fig. 3 B is the waveform schematic diagram that bandwidth-limited circuit exports.Bandwidth-limited circuit filters out the waveform different with modulating light frequency, and the clutter of the less filtering of bandwidth is cleaner, but requires also higher to filtering circuit, and DC influence ripple 34 is filtered out, and AC influence signal 31,32,35 and waveform 33 still exist;
Fig. 3 C is the waveform schematic diagram of the output of threshold circuit.Adjustable time delay 501 is after time delay Δ t1, send enable signal to threshold circuit, threshold circuit is opened, start to catch the signal waveform produced by normal fluid scattered light, after opening the Δ t2 time, threshold circuit cuts out, the waveform 33 caught is the signal that normal fluid scattered light produces, AC influence signal 31, 32, 35 are isolated, Δ t1 is the opening time of gate circuit, its start time is synchronous with pulse producer, its size is the time value T that light is transmitted into that light arrives photodetector, Δ t2 is the service time of gate circuit, its numerical value is (2 ~ 3) * T1,
Fig. 4 is the least-squares algorithm linear fitting schematic diagram that standard solution turbidity value and voltage carry out.For the standard solution of different turbidity, measure the magnitude of voltage 40 that its scattered light produces, the data of magnitude of voltage and standard solution turbidity are carried out least-squares algorithm linear fitting, and obtain the linear relationship 41 of turbidity and magnitude of voltage, fitting formula is:
y=kx+b
Wherein: x: magnitude of voltage, unit mV;
Y: titer turbidity value, unit NTU;
K, b: least-squares algorithm linear fitting coefficient;
Error:
e=|y1-（kx1+b）|
E is actual turbidity value and error size after least square fitting, and its value size can as the evaluation of precision after least square fitting.
Structure of the present invention is simple, be easy to realize, stability is high, effectively improve liquid turbidity measuring accuracy and sensitivity, providing technical guarantee for carrying out long-term online water quality monitoring.
The content be not described in detail in instructions of the present invention belongs to the known prior art of professional and technical personnel in the field.
The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (4)
1. a thresholding formula laser liquid turbidity meter, it is characterized in that: comprise light source module (100), optic path and photoelectric conversion module (200), Signal-regulated kinase (300), Signal acquiring and processing module (400), controllable signal generation module (500), the second flange (11B), optical fiber focuser (12), normal fluid (13); Light source module (100) comprises Laser Control System (101), laser instrument (102); Optic path and photoelectric conversion module (200) comprise three fiber port circulators (201), photodetector (202), the first flange (11A), three-flange (11C); Signal-regulated kinase (300) comprises pre-amplification circuit (301), second amplifying circuit (302), bandwidth-limited circuit (303), threshold circuit (304); Signal acquiring and processing module (400) comprises signal acquisition circuit (401), controller (402), data display circuit (403), memory circuit (404); Controllable signal generation module (500) comprises adjustable time delay (501), pulse producer (502); Optical fiber focuser (12) is connected with three fiber port circulators (201) by the second flange (11B);
A. described Laser Control System (101) is after pulse producer (502) modulation, control the light modulated (20) that laser instrument (102) launches cycle and adjustable pulse width, described laser instrument (102) adopts high-speed pulse modulation, and minimum pulse width is wanted to reach 10ps;
B. described laser instrument (102) utilizing emitted light enters into three port circulators (201) first port (201A) through the first flange (11A), then send from second port (201B) of three port circulators (201) and be transferred to optical fiber focuser (12) through the second flange (11B), the illumination of launching from optical fiber focuser (12) is on normal fluid (13), part rear orientation light after the scattering of normal fluid (13) endoparticle thing is reflected back optical fiber focuser (12), three fiber port circulators (201) are entered into by the second flange (11B), and enter into photodetector (202) from the 3rd port (201C) of three fiber port circulators (201) through three-flange (11C), photodetector (202) realizes the conversion of light signal to low current signal,
C. described pre-amplification circuit (301) carries out electric current to the conversion of voltage and amplification to the low current signal that photodetector (202) is changed, the output signal of second amplifying circuit (302) to pre-amplification circuit (301) carries out secondary amplification, meet the requirement of signal acquisition circuit (401) voltage range-10V-+10V, bandwidth-limited circuit (303) realizes pulse producer (502) and produces passing through of frequency signal, the signal amplitude being different from pulse producer frequency is subject to large decay or suppression, the signal (33) that threshold circuit (304) can realize normal fluid (13) rear orientation light produces is selected, to having with the asynchronous AC influence signal (31 of frequency, 32, 35) isolate,
D. described signal acquisition circuit (401) realizes the conversion of simulating signal to digital signal, controller (402) realizes the control of Acquisition Circuit (401), digital signal processing, magnitude of voltage to the conversion of actual liquid turbidity, the coefficient that memory circuit (404) storage voltage value is changed to actual liquid turbidity, the turbidity value of data display circuit (403) display liquid;
E. described adjustable time delay (501) is synchronous with pulse producer (502) signal, described adjustable time delay (501) sends enable signal and starts threshold circuit (304) after time delay Δ t1, threshold circuit (304) is opened, the pulsewidth that the effective acting time of threshold circuit need produce according to pulse producer is determined, get the pulsewidth of 2 ~ 3 times, signal now from bandwidth-limited circuit (303) starts to be selected, after opening the Δ t2 time, signal is chosen complete, threshold circuit (304) cuts out, threshold circuit (304) down periods, signal from bandwidth-limited circuit (303) is all isolated.
2. thresholding formula laser liquid turbidity meter according to claim 1, it is characterized in that: in described optic path and photoelectric conversion module (200), the transmission medium of light adopts single-mode fiber, there is long transmission distance, loss is low, antijamming capability is strong, advantage that security is high.
3. thresholding formula laser liquid turbidity meter according to claim 1, it is characterized in that: described optic path and photoelectric conversion module (200) adopt the detecting structure of all-fiber formula, probe size is less, and the liquid turbidity being applicable to small space is measured.
4. a thresholding formula laser liquid turbidimetry method, is characterized in that performing step is as follows:
A. light is issued to from laser instrument (102) and reaches normal fluid (13), and the transmission time then being arrived photodetector (202) by liquid-scattering is a fixed amount T;
B. arrange the waveform (20) that pulse producer (502) produces width to be T1 and cycle be T2, the time delay arranging adjustable time delay (501) is Δ t1=T, and delay time length is Δ t2=(2 ~ 3) * T1;
C. second amplifying circuit (302) output waveform (30A) in signal conditioning circuit (300), three parts are comprised: AC influence signal (31 in output waveform (30A), 32,35), its frequency is identical with the modulating light frequency that pulse producer (502) produces; DC influence signal (34) all exists in whole cycle T 2; The voltage signal (33) of the rear orientation light conversion that normal fluid (13) produces;
D. the output signal of second amplifying circuit (302) is by the output waveform (30B) after bandwidth-limited circuit (303), DC influence signal (34) is filtered out, and AC influence signal (31,32,35) still exists;
E. adjustable time delay (501) is after time delay Δ t1, send enable signal to threshold circuit (304), the pulsewidth that the effective acting time of threshold circuit need produce according to pulse producer is determined, get the pulsewidth of 2 ~ 3 times, threshold circuit (304) is opened, after opening the Δ t2 time, threshold circuit (304) cuts out, the voltage signal (33) of the rear orientation light conversion that the normal fluid (13) selected produces is the magnitude of voltage of normal fluid (13) rear orientation light conversion, and AC influence signal (31,32,35) is isolated;
F. controller (402) gathers threshold circuit (304) magnitude of voltage that exports by signal acquisition circuit (401), and magnitude of voltage is made maximum-minimum value and remove and be saved in memory circuit (404) after average value processing;
G. for the standard solution of different turbidity, measure the magnitude of voltage that its scattered light produces, the data of magnitude of voltage and standard solution turbidity carried out least-squares algorithm linear fitting, obtains the relation of turbidity and magnitude of voltage:
y＝kx+b (1)
Wherein: x: magnitude of voltage, unit mV;
Y: titer turbidity value, unit NTU;
K, b: least-squares algorithm linear fitting coefficient;
H. fitting coefficient is saved in memory circuit (404), when measuring liquid turbidity, the magnitude of voltage obtained is updated in formula (1), obtains liquid turbidity value.
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| CN103528960A (en) * | 2013-10-25 | 2014-01-22 | 吉林省百瑞生科技发展有限公司 | Online monitoring system of sewage by spectral interference method |
| CN103837501B (en) * | 2014-03-12 | 2016-05-25 | 江苏绿威环保科技有限公司 | A kind of analytical method of moisture percentage in sewage sludge |
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