CN104977281A - High-precision online fluorescence detector and detection method thereof - Google Patents

Abstract

The invention discloses a high-precision online fluorescence detector and a detection method thereof. The detector comprises a photoelectric sensor module, a single processing module, an equal precision frequency measuring module, a USB-serial interface conversion module, a power supply module and an upper computer. The photoelectric sensor module is connected to the single processing module; the output terminal of the single processing module is connected to the equal precision frequency measuring module; the equal precision frequency measuring module is connected to the USB-serial interface conversion module through a lower computer; the USB-serial interface conversion module is connected to the upper computer; and the power supply module is connected to the photoelectric sensor module, the single processing module, the equal precision frequency measuring module, and the USB-serial interface conversion module. The detector can be on-line co-used with a flow injection analyzer to detect the concentration of trace ammonia-N on line, has the advantages of good selectivity, high sensitivity, rapid responding speed, high accuracy, good stability, low cost, and small volume, and thus has a good application prospect.

Description

A kind of online fluorescence detector of high precision and detection method thereof

Technical field

The present invention relates to a kind of detecting device, be specifically related to the online fluorescence detector of a kind of high precision and detection method.

Background technology

Ammonium nitrogen is most important inorganic N forms in water body, and it directly can be utilized by the phytoplankton in water body, and first the nitrogen of other form need to be converted into ammonium nitrogen and could be utilized by phytoplankton.In water body, ammonium nitrogen content is too high, can poison hydrobiont and even destroy water ecology balance; Content is too low, may suppress the growth of phytoplankton, affects the primary productivity in waters, and then affects aquatic ecosystem balance.The content of ammonium nitrogen in Accurate Determining water body, is understanding water quality situation, predicts that aquatic productivity situation is necessary.In fact, ammonium nitrogen is one of elementary item requiring in the standards such as national water environment quality standard (GB 3838-2002), sea water quality standard (GB3097-1997) to measure.

Ammonium nitrogen fluorescence detection method is the method for measured trace rank ammonium nitrogen concentration extensively concerned in recent years, is the most potential method developing into on-line checkingi.The development trend of environmental monitoring is on-the-spot acquisition data, to improving detection efficiency, avoids the contamination problems of sample from sampled point to laboratory transportation.Therefore, based on ammonium nitrogen fluorescence detection method and Flow Injection Analysis Method, the online fluorescence detector of miniaturization ammonium nitrogen that development can be used for on-the site analysis has very large DEVELOPMENT PROSPECT.The current online detection technique of fluorescence of ammonium nitrogen is all based on o-phthalaldehyde(OPA) (ο-phthaldialdehyde, be called for short OPA) method, adopt large-scale all purpose instrument to analyze in laboratory, still lack can be applicable to environmental monitoring scene low cost, miniaturization the online fluorescence detector of ammonium nitrogen.And wavelength need be selected to be positioned at the excitation source of ultraviolet region based on OPA method developmental tester, there is very large difficulty in exploitation, and still lacks based on 4, and (4-methoxyphthalaldehyde is called for short M to 5-dimethoxy o-phthalaldehyde(OPA) ₂oPA) method, excitation source wavelength are positioned at the ammonium nitrogen on-line checkingi device of visible region.

Summary of the invention

For overcoming the above problems, the present invention is based on M ₂oPA method and Flow Injection Analysis Method, provide a kind of high precision online fluorescence detector, and its excitation source wavelength, in the visible region of centre wavelength between 390 ~ 400nm, can be used for field monitoring, and cost is low, volume is little.Because fluorescent intensity is directly proportional to ammonium nitrogen concentration, the online fluorescence detector of the present invention's design is by detecting the ammonium nitrogen concentration of the quantitative liquid to be measured of fluorescent intensity.

The online fluorescence detector of high precision of the present invention comprises photoelectric sensor module, signal processing module, equally accurate frequency measurement module, USB-serial ports modular converter, power module five modules and host computer.Photoelectric sensor module is connected with signal processing module, the output terminal of signal processing module is connected to equally accurate frequency measurement module, equally accurate frequency measurement module connects USB-serial ports modular converter by slave computer again, USB-serial ports modular converter is connected with host computer, power module respectively connected photoelectric sensor module, signal processing module, equally accurate frequency measurement module and USB-serial ports modular converter, is these module for power supply.

Described photoelectric sensor module comprises excitation source, flow cell, 3 convex lens, 1 narrow band pass filter, silicon photoelectric diode.In order to improve the sensitivity of detecting device, the light of excitation source will irradiate solution to be measured as much as possible, to inspiring more fluorescence; Meanwhile, the fluorescence inspired will enter silicon photoelectric diode as much as possible.The present invention makes improvement in following two: 1) select two LED staggered relatively, improves the intensity of excitation source.2) light in convex lens converges activation light source is used.Choose the placement location of convex lens 1,2, make its focus all be positioned at the center of modular cartridge groove, i.e. the center of flow cell transmission region.Groove length and width are 15mm, the diameter placing the aperture of LED is 10.5mm, and the focal length of convex lens 1,2 is 7mm, and diameter is 10mm, therefore only need convex lens 1,2 to be directly positioned over the marginal position of aperture near groove side, just can ensure that focal position is close to groove center.After placing convex lens 1,2, LED is fixed in hollow screw, screws in the aperture on modular cartridge wall.Do the position that can adjust LED neatly like this, turn avoid the interference of extraneous natural light.Meanwhile, in order to make fluorescence enter silicon photoelectric diode as much as possible, also convex lens 3 being close to flow cell printing opacity mouth and placing, the photosensitive region of silicon photoelectric diode being placed in the focus place of convex lens, utilizing convex lens converging ray.In order to avoid interference, ensure that the light of excitation source will enter silicon photoelectric diode as few as possible, the present invention also makes improvement in following two: 1) all placed perpendicular to silicon photoelectric diode by two excitation sources, and use the light in convex lens converges activation light source.2) on a fritter black electricity adhesive plaster, draw out the square hole measure-alike with silicon photoelectric diode photosensitive region, silicon photoelectric diode is wrapped up, only exposes photosensitive region; Before narrow band pass filter being close to silicon photoelectric diode, the light after guaranteeing only to allow by optical filter injects induction window simultaneously.

Described signal processing module comprises amplifying circuit, filtering circuit, voltage-frequency conversion circuit and optical coupling isolation circuit.Wherein the design of amplifying circuit, filtering circuit and voltage-frequency conversion circuit is the technical scheme disclosed in CN203364965U with reference to publication number: based on the optical signal detecting device of equally accurate frequency measurement.In order to avoid mimic channel produces interference to digital circuit, select high-speed linear optocoupler 6N137 to build optical coupling isolation circuit and both are separated, make the direct connection not having electricity between two parts circuit.Compared with the circuit not adopting optical coupling isolator, system signal noise ratio significantly improves, successful.

Described equally accurate frequency measurement module uses STM32 to carry out equal precision measurement as microcontroller to the frequency that signal processing module exports, and its design is the technical scheme disclosed in CN203364965U with reference to publication number: based on the optical signal detecting device of equally accurate frequency measurement.This module is made up of STM32F103RBT6 and peripheral circuit thereof on hardware, realizes equally accurate frequency measurement after burned program of lower computer.The passage 3 (TIM2_CH3) of general purpose timer 2 produces reference pulse F ₀, the pin PA2 corresponding from this passage exports; The passage 2 (TIM4_CH2) of general purpose timer 4 is to F ₀count, on hardware, corresponding pin PB7 and the PA2 of this passage is connected; The passage 1 (TIM1_CH1) of senior timer 1 is to pulse F to be measured _xcount, on hardware, the corresponding pin PA8 of this passage is connected with the output of photoelectric sensor module.

Described USB-serial ports modular converter is the conversion that Transistor-Transistor Logic level and RS-232 level are carried out in the communication of upper and lower machine.The main chip of USB-serial ports modular converter is that the 43 pin RXD of 1 pin TXD and the STM32F103RBT6 of PL2303, PL2303 are connected, and the 42 pin TXD of 5 pin RXD and the STM32F103RBT6 of PL2303 are connected, and realizes the conversion of USB-serial ports.

Described power module can adopt 9V power supply adaptor, 9V button cell or USB interface as power supply.The photoelectric sensor module of detecting device needs 3.3V voltage driven LED; AD795, AD706 and AD650 chip of signal processing module all needs ± 15V power voltage supply; The STM32F103RBT6 chip of equally accurate frequency measurement module needs 3.3V power voltage supply; The PL2303 chip of USB-serial ports modular converter needs 5V power voltage supply.The design of power module is the technical scheme disclosed in CN203981587U with reference to publication number: portable ammonium nitrogen fluorescence detector.

Described host computer is divided into following module: man-machine interface, serial communication modular, data processing module, display graphics module and data memory module.

Except photoelectric sensor module, signal processing module, equally accurate frequency measurement module, USB-serial ports modular converter and power module are all integrated on one piece of PCB mainboard.Finally photoelectric sensor module and mainboard are placed in the chassis, be assembled into an online fluorescence detector of ammonium nitrogen.

Another object of the present invention is to provide a kind of online fluorescence detector of high precision that utilizes and carries out the method detected, and the method comprises following key step:

1) solution to be measured in flow cell is exposed to after the light planoconvex lens optically focused that the excitation source in photoelectric sensor module sends, ammonium nitrogen fluorescence-causing substance in solution is stimulated and sends fluorescence, fluorescence injects silicon photoelectric diode photosensitive region after another convex lens are assembled and narrow band pass filter filters, fluorescence signal exports signal processing module to after being converted to weak current signal by silicon photoelectric diode;

2) weak current signal is converted to a larger d. c. voltage signal by amplifying circuit by signal processing module, then through filtering circuit filtering undesired signal wherein, filtered d. c. voltage signal is converted to frequency signal by voltage-frequency conversion circuit, and last frequency signal exports equally accurate frequency measurement module to through optical coupling isolation circuit;

3) equally accurate frequency measurement module adopts Equal-precision digital frequency measure method, carries out equal precision measurement, then process measurement result frequency, rejects gross error and gets average, obtaining detecting device desired data; Finally send data to host computer;

4) USB-serial ports modular converter carries out the conversion of Transistor-Transistor Logic level and RS-232 level to data, realizes the communication of upper and lower machine;

5) host computer receives and sends from equally accurate frequency measurement module, through the data of USB-serial ports modular converter conversion, then carries out zeroing process to data, and then in real time display detects data, calculating peak value drawing, and finally stores data.

Described step 3) in, use STM32 to carry out equal precision measurement as microcontroller to frequency.

The present invention can be applicable to environmental monitoring scene, have that selectivity is good, sensitivity is higher, fast response time, good stability, low cost and other advantages, there is good baseline stability and to constant signal response stability, the water sample of energy Measurement accuracy ammonium nitrogen concentration within the scope of 0.25 ~ 12 μm of ol/L, with the measurement result significant correlation of RF-5301PC type fluorescence detector; The mensuration with ammonium nitrogen concentration in actual water body can be applied, with RF-5301PC type fluorescence detector, there is comparability, there is certain accuracy.

Accompanying drawing explanation

Fig. 1 is general structure block diagram of the present invention;

Fig. 2 is that photoelectric sensor module of the present invention is overlooked and cutd open figure;

Fig. 3 is the upper computer software process flow diagram in the present invention.

Embodiment

As Fig. 1, the online fluorescence detector in visible region of trace ammonium nitrogen of the present invention is made up of photoelectric sensor module, signal processing module, equally accurate frequency measurement module, USB-serial ports modular converter, power module five modules and host computer.Photoelectric sensor module comprises the special flow cell of on-line checkingi, excitation source, silicon photoelectric diode, 3 convex lens and 1 narrow band pass filter.The light that two excitation sources send respectively after planoconvex lens 1,2 optically focused common irradiation to the solution to be measured in flow cell, ammonium nitrogen fluorescence-causing substance in solution is stimulated and sends fluorescence, silicon photoelectric diode photosensitive region is injected after fluorescence planoconvex lens 3 is assembled and narrow band pass filter filters, fluorescence signal exports signal processing module to after being converted to weak current signal by silicon photoelectric diode.Overlooking of this module cuts open figure as shown in Figure 2.Weak current signal is converted to a larger d. c. voltage signal by amplifying circuit by signal processing module, then through filtering circuit filtering undesired signal wherein, filtered d. c. voltage signal is converted to frequency signal by voltage-frequency conversion circuit, and last frequency signal exports equally accurate frequency measurement module to through optical coupling isolation circuit.Equally accurate frequency measurement module adopts Equal-precision digital frequency measure method, uses STM32 to carry out equal precision measurement as microcontroller to frequency, then processes measurement result, reject gross error and get average, obtaining detecting device desired data; Finally send data to host computer.USB-serial ports modular converter carries out the conversion of Transistor-Transistor Logic level and RS-232 level, realizes the communication of upper and lower machine.Power module adopts 9V power supply adaptor, 9V button cell or USB interface to provide electric energy for above each module.Finally, the frequency data that host computer equity Precision Measuring Frequency module is sent carry out receiving, process, show and storing.First receive and send from equally accurate frequency measurement module, through the data of USB-serial ports modular converter conversion, then carry out zeroing process to data, then displaying data in real-time, calculating peak value drawing, finally store data.

Being specifically described as follows of each parts of photoelectric sensor module:

The flow cell that flow cell uses RF-5301PC type fluorospectrophotometer supporting, this flow cell is of a size of 12.5mm × 12.5mm × 45mm, black quartz glass material, three printing opacities, square printing opacity mouth is of a size of 5.4mm × 5.4mm, 15mm, distance wall limit 6.25mm bottom printing opacity mouth centre distance.

Select TJ-LF5WVGYMC-AC type LED that Taiwan Tong Jia Optoelectronics Technology incorporated company produces as excitation source.

The S2386-8K type silicon photoelectric diode adopting Japanese Bin Song group to produce is as photoelectric sensor.

Convex lens 1,2 are for the light of converges activation light source LED, and select single convex lens sheet of PMMA material, diameter 10mm, the thick 4.5mm in center, the thick 1.5mm in limit, focal length 7mm, transmittance is 93%; The fluorescence that convex lens 3 are inspired for assembling fluorescent material, select single convex lens sheet of glass material, diameter 12.4mm, the thick 4.6mm in center, the thick 1.3mm in limit, focal length 14mm, transmittance is 95%.

The BP482/13K type spike interference filter selecting Shanghai Mega-9 Optoelectronic Technology Co., Ltd. to produce is placed between cuvette and silicon photoelectric diode, filters stray light, guarantees that silicon photoelectric diode receives only fluorescence.

Modular cartridge adopts the processing of 3D printing technique.In conjunction with size and the structural representation of each device, AutoCAD Software on Drawing is used to go out the three-dimensional plot of modular cartridge.Modular cartridge is made up of lid and box body.Lid external dimensions is 60mm × 60mm × 55mm, thick 8mm, and lid top has diameter to be the aperture of 8mm, is the import and export of reaction tube when carrying out Flow Injection Analysis.Box height 39mm, the length and width of below are 60mm, and the length and width at 10mm place, the top are 40mm, and design is in order to avoid extraneous natural light enters modular cartridge by the intersection of lid and box body like this; Length and width for the central recess placing flow cell are 15mm; On wall, there is circular opening in three faces, the center of circle in three holes and the center superposition of flow cell three printing opacity mouths, namely, 15mm bottom distance of center circle, apart from groove walls limit 7.5mm, two wherein relative diameters are that to place two LED and convex lens the 1,2, the 3rd diameter be that convex lens 3, narrow band pass filter and silicon photoelectric diode are placed in the hole of 14.5mm for the hole of 10.5mm; Bottom box body, there is aperture the corner of projection, screw stuck-module box easy to use.Select dimensional stability and the good black ABS plastic of shock resistance as printed material, three-dimensional plot is converted to STL form, gives 3D printer and print.

Amplifying circuit in signal processing module selects AD795 as amplifier, adopts T-shaped feedback resistive network, low current signal is converted to a larger voltage signal.Output voltage V _outwith input current I _drelational expression be:

$V_{out}=I_d{R}_{26}(1+\frac{R_{28}}{R_{27}})=2.2\×{10}^7\×(1+\frac{R_{28}}{{10}^3})I_d---\left(1\right)$

Because rheostat R ₂₈maximal value be 50k Ω, show that enlargement factor is 2.2 × 10 ⁷with 1.112 × 10 ⁹between.

Filtering circuit is divided into three grades, and select AD706 as amplifier, the first order is passive low ventilating filter, for removing the 50Hz Hz noise that AC power produces.Its cutoff frequency is f=1/2 π R ₃₁c ₃₂=1.6Hz, effectively can remove Hz noise.The second level is voltage follower.The output impedance of voltage amplifier is higher, and the input impedance of rear class is less, and in signal, a big chunk loss is in the output resistance of prime.Therefore need the voltage follower that input impedance is high and output impedance is low to cushion, play the effect of forming a connecting link.The third level is second order active low-pass filter, filtering interference signals, the direct current signal after being amplified.The transport function expression formula of second order active low-pass filter is:

$A\left(S\right)=\frac{A_0{{\mathrm{\ω}}_n}^2}{S^2+({\mathrm{\ω}}_n/Q)S+{{\mathrm{\ω}}_n}^2}---\left(2\right)$

Wherein, unity gain A ₀=1+R ₃₆/ R ₃₅, characteristic angular frequency quality factor $Q=\frac{\sqrt{R_{33}{R}_{34}{C}_{34}{C}_{35}}}{C_{34}(R_{33}+R_{34})+R_{33}{C}_{35}(1-A_0)}.$

The cutoff frequency that can calculate second order active low-pass filter is f=ω _n/ 2 π=7.24Hz, equivalent quality factor Q=1, gain A=2.Illustrate that wave filter can keep steady operation, the undesired signal of energy more than filtering 7.24Hz, leaves direct current signal, and by voltage amplification one times.

Voltage-frequency conversion circuit selects AD650 as amplifier, and convert voltage signal to frequency signal, according to the formula that chip handbook provides, the pass calculating output frequency and input voltage is:

$f_{out}=0.15\×\frac{V_{IN}}{R_{38}+R_{39}}\×\frac{1}{C_{37}+4.4\×{10}^{-11}}=\frac{1.6\×{10}^8}{R_{38}+1.5\×{10}^4}{V}_{IN}---\left(3\right)$

Visible, frequency and voltage is linear, due to rheostat R ₃₈maximal value be 5k Ω, show that conversion coefficient is between 8000 and 10000.

Equally accurate frequency measurement module is made up of STM32F103RBT6 and peripheral circuit thereof on hardware, realizes equally accurate frequency measurement after burned program of lower computer.The function that slave computer software realizes is frequency values, surveyed data is processed, and is uploaded to host computer after removing gross error.Idiographic flow comprises system initialization, Equal-precision digital frequency measure, data processing, serial ports transmission etc., accordingly by slave computer software procedure division frequency measuring block, data processing module and serial communication modular.

First frequency measuring block carries out Initialize installation to three timers and corresponding GPIO mouth.TIM2_CH3 is configured to the standard block pulse F that pulse-length modulation (Pulse Width Modulation is called for short PWM) pattern exports 1MHz ₀, the pin PA2 corresponding with this passage is configured to multiplexingly recommend output mode.TIM4_CH2 is set to downward count mode to full sized pules F ₀count, corresponding pin PB7 is configured to floating input pattern, and PB7 is connected with PA2 on hardware.TIM1_CH1 is set to downward count mode to pulse F to be measured _xcount, corresponding pin PA8 is configured to floating input pattern, and PA8 connects the output terminal of optical coupling isolation circuit on hardware.

Principal function control TIM4 and TIM1 starts counting simultaneously.A sign bit flag is set simultaneously, initialize 1.Principal function detects the value of flag, and as flag=1, two timers keep count status; As flag=0, two timers cut out, and counting terminates.Because measured signal F _xbe less than standard signal F ₀, so the inevitable TIM1 meter prior to counting measured signal of the TIM4 of counting criteria signal completely enters interruption.In the interrupt function of TIM4, remove interrupt flag bit, make its repeat count, and record enters frequency n _ 4 of interruption, for treating the calculating of measured frequency.In the interrupt function of TIM1, it is except interrupt flag bit clearly, is set to 0 by flag, and record enters the frequency n um of interruption, for the process of data.Have no progeny in TIM1 meter completely enters, principal function detects that flag is 0, and control TIM4 and TIM1 closes simultaneously.Employ TIM1 in module to interrupt and TIM4 interruption, priority orders is: TIM1 interrupt priority level >TIM4 interrupt priority level.

After two counters cut out, in principal function calculating frequency value.Computing formula is such as formula shown in (4).

$F_x=\frac{65536\×1000}{65536\×n_4+(65536-TIM\_GetCounter(TIM4\left)\right)}---\left(4\right)$

Wherein, Using Call Library Function TIM_GetCounter (TIM4) obtains in TIM4 and does not count full value, and the cps calculated is kHz.

Gross error is differentiated according to Lay with special criterion in data processing module ^[12], reject the measurement wherein containing a Frequency point in completing user meaning of averaging after the measured value of gross error.Detailed process is, work as num=50, after namely carrying out 50 frequency measurements, try to achieve the arithmetic mean L of these frequency values according to formula (5), obtain the residual error γ of each result and L again according to formula (6) respectively, finally obtain standard error σ according to formula (7).The standard error of each residual error obtained and three times compares, if be greater than 3 σ, think in this result containing gross error, should reject.Reject wherein containing after the frequency values of gross error, remaining frequency values is averaged the measurement of a Frequency point in completing user meaning.

$L=\underset{k=1}{\overset{50}{\Σ}}{l}_k---\left(5\right)$

γ _k＝|l _k-L| (6)

$\mathrm{\σ}=\sqrt{\underset{k=1}{\overset{50}{\Σ}}\frac{{{\mathrm{\γ}}_k}^2}{50-1}}---\left(7\right)$

Serial communication modular utilizes the serial ports 1 of STM32F103RBT6 that the data handled well are sent to host computer.The Initialize installation of serial ports leaves in function usart.c, and concrete steps comprise the enable serial ports clock of call function RCC_APB2PeriphClockCmd (RCC_APB2Periph_USART1), call function USART_DeInit (USART1) is realized serial ports and resets, realized data transmission and receive, read com-state by status register USART_SR by bi-directional data register USART_DR.

In principal function, the frequency values recorded is floating number, retains 2 significant digits in program.Before sending, data are multiplied by 100 and become integer.First send check code 0xAA through serial ports, then divide three transmissions by data from a high position to low level, each transmission eight.Process accordingly at host computer, be reduced into original floating number.After data are sent, control DS1 glimmers once, by judging that button KEY1 determines whether to enter frequency measurement next time.If do not press KEY1, then flag is put 1, n_4, n_1 are reset, enters frequency measurement next time immediately; If press KEY1, then terminate program immediately.

In power module, the photoelectric sensor module of detecting device needs 3.3V voltage driven LED; AD795, AD706 and AD650 chip of signal processing module all needs ± 15V power voltage supply; The STM32F103RBT6 chip of equally accurate frequency measurement module needs 3.3V power voltage supply; The PL2303 chip of USB-serial ports modular converter needs 5V power voltage supply.

Except photoelectric sensor module, signal processing module, equally accurate frequency measurement module, USB-serial ports modular converter and power module are all integrated on one piece of PCB mainboard.The apparent size of mainboard is 10cm × 10cm, and top is power module, and lower left is signal processing module, and lower right is equally accurate frequency measurement module and USB-serial ports modular converter.Although mainboard is small and exquisite, feature richness, not only achieves the demand of detecting device, also has good extendability.

Except the resource of signal processing module, equally accurate frequency measurement module, USB-serial ports modular converter and power module indispensability, it is as follows that other plate of mainboard carries resource:

2 power lights a: mimic channel powers on instruction (red), a digital circuit powers on instruction (green);

2 status indicator lamp: DS1 (orange), DS2 (white);

Mouth is downloaded in the JTAG/SW debugging of 1 standard;

1 OLED module interface;

1 SD card interface;

1 start-up mode option and installment switch;

1 reset button, can be used for reset MCU and OLED;

3 buttons, wherein 2 is the button of common key-press, 1 compatible arousal function;

1 RTC backup battery seat, and be with 3.3V button cell;

1 active buzzer;

1 group of 9V power supply supply/access port;

1 group of 5V power supply supply/access port;

1 group of 3.3V power supply supply/access port;

1 group of 15V power supply supply/access port;

1 group of-15V power supply supply/access port;

37 I/O ports are drawn.

Finally photoelectric sensor module and mainboard are placed in the chassis, be assembled into an online fluorescence detector of ammonium nitrogen.Photoelectric sensor module and mainboard separate, and avoid careless manipulation to be poured onto on mainboard by solution, damage detecting device.Cabinet Size is 29cm × 21cm × 10cm, ABS plastic material, good impact resistance, good airproof performance, heat-resisting low temperature resistant.Make detecting device not only attractive in appearance but also can measure under lowered in field environment like this.

Upper computer software, as Fig. 3, accordingly, is divided into following module by the process flow diagram of upper computer software: man-machine interface, serial communication modular, data processing module, display graphics module and data memory module.

Man-machine interface is divided into drawing area, viewing area and control area.The range of the drawing area longitudinal axis is 667, for drawing the change curve of data in real time.Viewing area is made up of two edit boxes, one for real-time display frequency value, another is for display frequency maximal value.Control area then comprises the selection drop-down hurdle of serial ports, opens serial ports button, closes serial ports button, zero-setting button and exit button.

In man-machine interface, the fluorescent intensity that the frequency values that host computer receives sends to solution in certain scope is directly proportional, and for the purpose of directly perceived, this frequency values is called fluorescence intensity by this interface, and unit is arbitrary unit (A.U.).

Serial communication modular utilizes MSCOMM communication control to realize serial communication.

Opening serial ports and closing serial ports button in man-machine interface, control function is set to OnOpencomm and OnClosecomm.In OnOpencomm function, first needing to arrange reception buffer zone size is 2048 bytes, and sending buffer size is 512 bytes, data acquisition is scale-of-two, and getting at every turn and reading length be 0, ONCOM threshold value is 4, baud rate is 9600bps, no parity check value, 8 data bit, 1 position of rest.Then call SetCommPort (m_selectcomm.GetCurSel ()+1) function and select serial ports COM (n), SetPortOpen function opens this serial ports, EnableWindow function control knob state.OnClosecomm function is then comparatively simple, calls SetPortOpen function and closes serial ports, EnableWindow function control knob state.

After opening serial ports, when there is character reception buffer zone, gets and read buffer zone character, complete the reception of data.And be BYTE type array by the Data Format Transform received, facilitate follow-up data processing.

The mode that data processing module sends according to slave computer, the character received by serial communication modular is oppositely reduced into original frequency values.First search out the starting point of each data, i.e. check code 0xAA, three data then after sequence reception check code, what first receive is data most-significant byte, and what finally receive is data least-significant byte.It is combined by high-low-position, and divided by 100, just obtains the legacy data that slave computer sends.This module also has zeroing function.When detecting device detects blank (as pure water), the frequency values recorded by principle should be 0, but because hardware itself exists certain background signal, detecting device can detect that frequency values is about 20, by opening the zeroing function of software, can be adjusted to 0.A sign bit zero_flag is set, initialize 0, after receiving data, judges the value of zero_flag.If zero_flag=0, then do not carry out zeroing computing, directly send into display graphics module and carry out showing and drawing; If zero_flag=1, then send into display graphics module after data being deducted 20 again and carry out showing and drawing.

First the frequency values calculated is presented in the instantaneous value edit box of man-machine interface by display graphics module.The data of floating-point format are converted to string format, the character string after conversion is assigned to edit box variable.In addition, the maximal value of data also need be shown in peak value edit box.If the initial value of variable temp_max is 0, host computer often receives data, just these data is compared with temp_max, if be greater than temp_max, then by this data assignment to temp_max, finally obtain the maximal value of data.This module, according to the data received, uses CClientDC class to realize real-time drawing function function.First in OnPaint () function, drawing scope is determined, and draw the fundamental such as horizontal stroke, the longitudinal axis, concrete step is as follows: call dc.Rectangle function determination rectangle draw region, the coordinate in its upper left corner and the lower right corner is divided into other (40,30) and (1240,430); Call dc.MoveTo (x1, y1) and dc.LineTo (x2, y2) function, draw horizontal, the longitudinal axis, horizontal, longitudinal axis major division line, horizontal stroke, the secondary scale mark of the longitudinal axis and horizontal stroke, longitudinal axis mesh lines; Determine longitudinal axis range, the fluorescence intensity level arranging 3 lattice major division representatives is 100, then the longitudinal axis range of drawing is 667; Call dc.TextOut function in corresponding coordinate points write range value.

Real-time drawing function is realized in principal function.Transverse axis coordinate interval between every two frequency values is 4, is the interval between two secondary scale marks, but need calculate each frequency values ordinate of orthogonal axes corresponding in drawing area.According to ordinate 30 respective frequencies value be 667, ordinate 430 respective frequencies value is 0, can calculate y_1=30+ (1-temp/667) × 400, wherein temp is frequency values, y_1 is ordinate value.Drafting principle is: (x_0, y_0) be last point coordinate, (x_1, y_1) be present coordinate, call dc.MoveTo (x_0, y_0) and dc.LineTo (x_1, y_1) function to draw one and connect this curve of 2, then any coordinate before covering with the coordinate of present point, prepares to draw next section of curve.

Data memory module utilizes the base class CFile of the supporting document operation provided in MFC to realize the storage of data.Module file is shared and the mode of accessing arranges as follows: CFile::modeCreate, indication structure function creation new file, if exist, then its length being blocked is 0; CFile::modeNoTruncate, combinationally uses with CFile::modeCreate, if the file just created exists, so its length can not be truncated is 0; CFile::modeReadWrite, opens file, and this file is readable to be write; CFile::typeText, arranges special processing to new line.

Then get edit box data and need call function GetDlgItemText, call the data write 1.txt that Write method will be taken out, in data writing process, the length that GetLength method obtains file need be called.Before each write, ending place that file pointer is placed into file by SeekToEnd method must be called, avoid data to be capped.Line feed after data write, close file, preservation process terminates.

The present invention has also carried out testing and analysis to the baseline stability of detecting device, constant signal response stability, measurement accuracy, on-line checkingi and practical application thereof.Instrument start latter about 7 minutes baselines and signal all reach stable, sustainablely stablize 290 minutes, as seen its baseline stability and constant signal response stability good.This detecting device and RF-5301PC type fluorescence detector is adopted to carry out offline inspection to 8 ammonium nitrogen standard solution within the scope of 0 ~ 12mol/L, both measurement result significant correlation (R respectively ²=0.9986, n=8), this detecting device can be used for the measurement of ammonium nitrogen sample solution as seen.Simultaneously, this detecting device and flow injection analyzer coupling, carried out on-line checkingi to the ammonium nitrogen solution of 5 within the scope of 0 ~ 32mol/L, upper computer software intactly have recorded the output signal curve of detecting device in real time, curve peak height value and ammonium nitrogen concentration significant correlation (R ²=0.9985, n=5), this detecting device can be successfully applied to the on-line checkingi of ammonium nitrogen sample solution as seen.Adopt this detecting device and RF-5301PC type fluorescence detector to measure the ammonium nitrogen concentration of 9 colored river samples respectively, this detecting device records the ammonium nitrogen concentration that the ammonium nitrogen concentration of water sample and RF-5301PC type fluorescence detector record and presents linear correlation (R ²=0.9281, n=9), the slope of linear equation is 1.145, and close to 1, this detector applies is in the mensuration of actual water sample as seen, has comparability with commercial instrument, has certain accuracy.

Claims (7)

1. the online fluorescence detector of high precision, comprises the equally accurate frequency measurement module containing slave computer, it is characterized in that, also comprises photoelectric sensor module, signal processing module, USB-serial ports modular converter, power module and host computer;

Photoelectric sensor module is connected with signal processing module, the output terminal of signal processing module is connected to equally accurate frequency measurement module, equally accurate frequency measurement module connects USB-serial ports modular converter by slave computer again, USB-serial ports modular converter is connected with host computer, and power module respectively connected photoelectric sensor module, signal processing module, equally accurate frequency measurement module and USB-serial ports modular converter;

In photoelectric sensor module, two excitation sources are placed on the both sides of flow cell respectively, the focus of convex lens 1, convex lens 2 is positioned at the center of modular cartridge groove, convex lens 3 are close to flow cell printing opacity mouth and are placed, the photosensitive region of silicon photoelectric diode is placed in the focus place of convex lens, utilize the black electricity adhesive plaster with square hole to be wrapped up by silicon photoelectric diode simultaneously, only expose photosensitive region; Before optical filter is close to silicon photoelectric diode.

2. online fluorescence detector according to claim 1, is characterized in that, the visible ray of wavelength between 390 ~ 400 nm centered by described excitation source.

3. online fluorescence detector according to claim 1, is characterized in that, described optical filter is narrow band pass filter.

4. online fluorescence detector according to claim 1, is characterized in that, described signal processing module comprises amplifying circuit, filtering circuit, voltage-frequency conversion circuit and optical coupling isolation circuit, and each circuit sequence connects.

5. online fluorescence detector according to claim 4, is characterized in that, optical coupling isolation circuit uses high-speed linear optocoupler 6N137 to build.

6. utilize the online fluorescence detector as described in any one of claim 1-5 to carry out the method detected, it is characterized in that: comprise step as follows:

1) solution to be measured in flow cell is exposed to after the light planoconvex lens optically focused that excitation source sends, ammonium nitrogen fluorescence-causing substance in solution is stimulated and sends fluorescence, fluorescence injects silicon photoelectric diode photosensitive region after another convex lens are assembled and narrow band pass filter filters, fluorescence signal exports signal processing module to after being converted to weak current signal by silicon photoelectric diode;

2) weak current signal is converted to a larger d. c. voltage signal by amplifying circuit by signal processing module, then through filtering circuit filtering undesired signal wherein, filtered d. c. voltage signal is converted to frequency signal by voltage-frequency conversion circuit, and last frequency signal exports equally accurate frequency measurement module to through optical coupling isolation circuit;

3) equally accurate frequency measurement module adopts Equal-precision digital frequency measure method, carries out equal precision measurement, then process measurement result frequency, rejects gross error and gets average, obtaining detecting device desired data; Finally send data to host computer;

4) USB-serial ports modular converter carries out the conversion of Transistor-Transistor Logic level and RS-232 level to data, realizes the communication of upper and lower machine;

5) host computer receives and sends from equally accurate frequency measurement module, through the data of USB-serial ports modular converter conversion, then carries out zeroing process to data, and then in real time display detects data, calculating peak value drawing, and finally stores data.

7. the detection method of online fluorescence detector according to claim 6, is characterized in that: use STM32 to carry out equal precision measurement as microcontroller to frequency in step 3).