CN100489497C - Automatic expanding circuit for absorption type analytical instrument optical detection measurement range - Google Patents
Automatic expanding circuit for absorption type analytical instrument optical detection measurement range Download PDFInfo
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Abstract
The present invention relates to an absorption type analysis instrument photo detection range automatic expansion circuit. Said invention is aimed at providing a circuit which has no need of changing the gain of photoelectric detector and can obtain automatic expansion of detection range. Said circuit includes silicon photoelectric detection amplifier, microprocessor, state memory and switch control circuit, electronic switch, pulse duration ratio/pulse generator, optical power drive circuit and light source. The light source is selected from LED light source or laser light source. Said invention also provides their connection mode.
Description
Technical field
The present invention relates to a kind of circuit of in absorbing the class spectral instrument, realizing Photoelectric Detection range automatic expansion, especially relate to a kind of to absorbing the inverse proportion control of the luminous power of light source in the class spectral instrument, so as to reaching the circuit that the output light after the absorption cell absorption of sample is detected the automatic expansion purpose of range.
Background technology
In the electronic technology in early days,, generally adopt fork shift switch manual switch to connect required range for the conversion of detecting device range.Development along with electronic technology and automatic technology, microprocessor, electronic switch, array resistors obtain to use widely, the range automatic expansion technology of automatically differentiating, carrying out automatically the range conversion be widely used in the conversion work of detecting device range (Zhao Maotai. intelligence instrument principle and application. Beijing: Electronic Industry Press, 1999:125-127), the detecting instrument that should change range by hand is fewer and feweri, is confined to the unaffordable occasions of electronic switch such as high pressure, big electric current more and uses.
No matter be the range automatic expansion technology or the process of manual fork shift conversion range, classical way in fact all is the yield value that changes detecting amplifier, make that the working point (be in the amplifier cut-off region or be in the saturation region) of the linear amplification region of sideslip detecting device comes back to the amplification region, thereby guarantee the linear relationship of all detected values.Their difference only is artificial and automatic differentiation, automaticity difference artificial and that change automatically.
In of the utilization of modern integrated operational amplifier as detecting amplifier, the element of decision detecting amplifier gain almost is linear element a---resistance R, and necessary bigger capacity cell C in parallel of ripe application, be used to eliminate the influence of loop distribution electric capacity and PCB (P.e.c.) plate distributed capacitance, it makes detecting amplifier have stable frequency characteristics.Therefore, suppose that the resistance R value of a design has the characteristic that is proportional to the amplifier gain coefficient, then with complex impedance after capacitor C is in parallel
Z＝R//(1/jωC)＝(R/jωC)/(R+1/jωC)
For making the linear detection zone of detecting device extend upward N times journey, then the slope of linearity of amplifier working curve is necessary for original 1/N, and promptly original complex impedance should change to
Zn＝Z/N
Obviously, the expansion of N times of range is actually the process in parallel (or equivalent process) of implementing N Z impedance, and manual range transformation applications fork shift switch connects, and automatic range transformation applications electronic switch carries out under the effect of range control signal from being dynamically connected.
The manufacture craft of hyundai electronics switch has accomplished that leakage resistance is the level of hundred megaohms, application scenario in most detecting device range automatic expansion, the resistance value that can change the detecting amplifier gain is the level of number K to hundreds of K ohm level, far below the leakage resistance of electronic switch, the influence of its leakage current can be ignored.But be more than 10 megohms and hold concurrently and to be the application scenario of detecting amplifier sample resistance for resistance value, the influence of leakage current that the electronic switch leakage resistance causes can not be ignored, it is shunted detection signal, causes the decline of detecting device detection sensitivity and detection resolution.
Silicon photoelectric diode is because to have a volume little and need not high voltage supply and long-lived advantage, and more is lower than 10 because the silicon photoelectric diode of modern crafts manufacturing has
-15(the performance level of W/Hz 1/2 noise equivalent power, being used in the electrooptical device field to replace must high voltage supply and the practical application of short photomultiplier is more and more many life-span, but it only is the per mille of photomultiplier or lower to the current sensitivity of same light intensity.Therefore, adopting silicon photoelectric diode to detect in the high impedance Photoelectric Detection amplifier of faint optical signal, utilizing 100 megohms sampling resistor above even 10G ohm to be used to obtain high as far as possible opto-electronic conversion and detected magnitude of voltage.Ratio increases and decreases the then variation of opto-electronic conversion detection magnitude of voltage generation ratio thereupon increase and decrease of this sampling resistor value, so its decision Photoelectric Detection Amplifier Gain.When using classics design range automatic expansion circuit, walk line loop but increased the electronic switch parallel resistor with electric capacity and the actual printed circuit of forming that is connected these parts (PCB), be used for making up the function that realizes the range automatic expansion with this sampling resistor.And will find that in actual applications building of this range automatic expansion circuit makes the following detection index of Photoelectric Detection amplifier that intrinsic change take place to depart from, when serious or even can't use, perhaps must the derate index use:
A. noise increases
Increased Resistance Thermal Noise, direct current Johnson noise, 1/f noise and temperature noise, walked line loop with electric capacity and the actual printed circuit of forming that is connected these parts (PCB) but the reason of generation is the electronic switch parallel resistor that increases.When the actual samples resistance that adopts is 100 megohms when above, Resistance Thermal Noise, direct current Johnson noise even may increase by one ten the order of magnitude than the Photoelectric Detection amplifier that does not adopt range automatic expansion circuit.The consequence that causes is the noise equivalent power (NEP) of detecting amplifier circuit overall noise greater than silicon photoelectric diode, the detection resolution of actual Photoelectric Detection amplifier is no longer by noise equivalent power (the http://www.hamamatsu.com of silicon photoelectric diode, si-photo-diode) decide, and mainly decide by in fact much bigger circuit noise.
B. intrinsic leakage current of electronic switch and the printed circuit board (pcb) extra influence of leakage current of walking line loop
For the current signal that makes opto-electronic conversion is converted to voltage signal effectively, the prime amplifier that detects the detecting device of faint optical signal must be the integrated operational amplifier of high input impedance.It is used to obtain the power coupling coefficient of maximum photoelectric conversion signal, improves detectability.And the printed circuit board (pcb) of the electronic switch that increases, parallel connection is walked the relation that the leakage current of line loop connects because of circuit, preposition input circuit is caused the bypass effect inevitably, cause the idle loss of opto-electronic conversion current signal, effectively decline of detection current value and then the decline of detectability index (high light God compiling. sensor and signal condition device application technology. Beijing: Science Press, 2002:43-57).
Therefore, for the consideration of detection sensitivity and stability indicator, their high resolving power Photoelectric Detection amplifier is still continued to use the photomultiplier of large-signal as electrooptical device in instrument, particularly the high resolving power spectrophotometer that more domestic and international famous absorption class spectral instrument manufacturers produce.The applying silicon photodiode is as the Photoelectric Detection amplifier of high sensitivity electrooptical device, yet there are no the range automatic expansion circuit that adopts classical design, these instruments require breadboard environment for use condition usually, and limiting the absorption light path of absorption cell, the sample concentration of preparation etc., the Photoelectric Detection amplifier that satisfies fixed gain is applied in the detection requirement in linear amplification zone.
In design based on the multiwave length spectro state carbon dioxide automatic monitoring system of long light path liquid core waveguide pipe, need a kind of auxiliary technology, be used to solve long light path liquid core waveguide pipe and absorb problem in the scope in Photoelectric Detection linearity of amplifier district that the light intensity of different wave length beam split after the absorption cell absorption of sample that optical length causes be seated in different gains.Wish to adopt silicon photoelectric diode to satisfy the requirement that long-lived and no high pressure uses simultaneously, and adopt Photoelectric Detection amplifier to detect the requirement that multiwave length spectro satisfies multiwave length spectro detected value consistance and relevance simultaneously with unified detection resolution and detectability index as photoelectric commutator.
Based on designing requirement, adopt silicon photoelectric diode must possess the function of range automatic expansion and the detection index of all multiwave length spectro detected values must meet unicity, promptly only can adopt the Resolution Si Photoelectric Detection amplifier of a fixed gain as the Photoelectric Detection amplifier of photoelectric commutator.
Summary of the invention
The objective of the invention is to cause high sensitivity detector detection sensitivity and detection resolution to descend at existing electronic detectors range automatic expansion circuit, increase problems such as extra many loops noise and electronic switch leakage current, a kind of circuit that the photoelectric detector gain obtains to detect the range automatic expansion that do not change is provided, be mainly used in and absorb in the class spectral instrument, the present invention only just can obtain multi-pass with the photoelectric detector of a fixed gain, the effect of accurately doubly taking advantage of the expansion linearity measuring range of many multiplying powers, and have unified detection resolution of whole ranges and detectability index, do not have the typical case and change extra many loops noise that RC sampling impedance acquisition Range Extension may be brought, the problem of electronic switch leakage current.
The luminous power of light source of the present invention must accurately be controlled, and promptly light source is the may command light source.Light emitting diode and laser diode exist certain linear very to be adapted at the application of circuit of the present invention because of belonging to cold light source and luminous power and drive signal, it is relevant with thermal effect because of luminous power before to have absorbed tungsten lamp common in the class spectral instrument, deuterium lamp, xenon lamp etc., belong to thermal light source, and have also must high pressure light and not too be fit to the use of circuit of the present invention.
The present invention is provided with:
A. the silicon Photoelectric Detection amplifier that has fixed gain is used for the monochromatic light of exporting after the absorption cell absorption of sample is carried out opto-electronic conversion and detects amplification;
B. microprocessor system, microprocessor system is provided with A/D converter, detect on the numerical value/the lower limit judging circuit, detect numerical value of N times multiplication circuit and the upper limit/lower limit overflow pulse generator, wherein, the detection numerical simulation signal output part of A/D converter input termination Photoelectric Detection amplifier:
C. state memorization and ON-OFF control circuit are made up of shift register and output buffered gate, and shift register moves to right and imports termination microprocessor upper limit overflow pulse output terminal, and shift register moves to left and imports termination microprocessor lower limit overflow pulse output terminal;
D. electronic switch is integrated analog switch, and electronic switch controling end connects level output buffered gate;
E. pulse duty factor/pulse producer is made up of time base circuit;
F. the luminous power driving circuit is used for providing the pulsed drive of the light source with works fine stability under the frequency pulse effect, the output terminal of its input termination pulse duty factor/pulse producer, output termination light source;
G. light source is selected from light emitting diode or laser diode light source.
Can make up base application of the present invention by said structure---single N multiplying power range automatic expansion circuit of single channel light source.
With existing electricity detecting device range automatic expansion circuit compare, outstanding advantage of the present invention is:
1) in absorbing the class spectral instrument, on the high sensitivity Photoelectric Detection amplifier of applying silicon optical diode as electrooptical device, can be implemented in the automatic expansion of the optical detection measurement range that still has unified high sensitivity and high detection resolution detection index between different ranges.
2) compare with classical detecting amplifier conversion range technology, have range conversion accuracy height, be not subjected to the influence that the issuable extra electrical noise of silicon Photoelectric Detection amplifier and contingent detection index change in the range transfer process.
3) the easy continuous automatic inspection that realizes the multiple light courcess spectrum of no step range.
Description of drawings
Fig. 1 is single N multiplying power range automatic expansion schematic block circuit diagram of base application embodiment single channel light source of the present invention.
Fig. 2 is N of the present invention times of range automatic expansion " virtual " fundamental diagram.
Fig. 3 is expansion Application Example three light paths of the present invention, take advantage of 2 with take advantage of 4 two multiplying power linearity measuring range automatic expansion circuit electrical schematic diagrams.
Embodiment
Following examples will be used with expansion know-why of the present invention in conjunction with the accompanying drawings and be described further.
In absorbing the spectrophotometric instrument, basic extinction law is an absorbance
A＝log(I
0/I)＝knl
Wherein, I
0Be the light intensity before the monochromatic light incident absorption cell, I is the output intensity after the monochromatic light process absorption cell absorption of sample, and K is the absorption coefficient of light of sample, n is a sample concentration, l for absorb light path (He Jinlan, Yankee allows, Li Xiaoge. the instrumental analysis principle, Science Press, 2002:193-321).
When K, n, l are given definite value,
knl＝log(I
0/I)＝log(2I
0/2I)＝log(NI
0/NI) <1>
Formula＜1〉illustrate under the situation of given K, n, l parameter, as former incident intensity I
0Be increased to 2 times, i.e. 2I
0The time, detected output intensity has also increased by 2 times, i.e. 2I; As former incident intensity I
0Be increased to N doubly, i.e. NI
0The time, detected output intensity has also increased N doubly, i.e. NI.
When the N value is during less than 1 decimal, incident intensity reduces, and increases greater than 1 o'clock.Suppose that output intensity after the absorption cell absorption of sample is too by force or too, cause the working point of Photoelectric Detection amplifier to surmount linear amplification region and enter saturation region or cut-off region, design and a kind ofly can satisfy formula＜1 circuit that changes is used to adjust the size of incident intensity (promptly adjusting the luminous power of light source), make output intensity get back to the intensity that is fit to Photoelectric Detection linearity of amplifier zone, then can realize the function of times range automatic expansion of Photoelectric Detection amplifier.
Formula＜1〉point out simultaneously, when the detection of given absorption cell and sample concentration being carried out absorbance when analyzing, using testing result that monochromatic light that different N doubly is worth intensity obtains at the Photoelectric Detection amplifier of fixed gain can be by formula＜1〉carry out Equivalent Conversion and obtain identical result.
The present invention is based on above-mentioned principle designs.
Below provide single N multiplying power range automatic expansion circuit theory of base application embodiment single channel light source of the present invention, referring to Fig. 1, single N multiplying power range automatic expansion circuit of single channel light source is provided with:
A. the Resolution Si Photoelectric Detection amplifier that has fixed gain is used for the monochromatic light of exporting after the absorption cell absorption of sample is carried out opto-electronic conversion and detects amplification.The sampling resistor of using is that the representative value of variable gain resistance is 1G ohm, and the electrooptical device of cooperation is S1226-44BQ type silicon photoelectric diode (Hamamatsu Corp.Japan), can obtain stable to be low to moderate 10
-6The detection lower limit of Lx illuminance.The present invention does not make the change of any resistance to this 1G ohm in testing process with in the transfer process of range automatic expansion, so the Photoelectric Detection Amplifier Gain is fixed, only for being in series with a loop of sampling resistor, it is minimum that the loop number reaches for preposition input circuit.Therefore, the Photoelectric Detection amplifier unit of rational Application electronic production technology manufacturing can reach the detection sensitivity of light signal or near the detectability of silicon photoelectric diode noise equivalent power.
B. microprocessor system adopts the PIC16F77 single-chip microcomputer.Microprocessor system is provided with A/D converter, detect on the numerical value/the lower limit judging circuit, detect numerical value of N times multiplication circuit and the upper limit/lower limit overflow pulse generator.Wherein, the detection numerical simulation signal output part of A/D converter input termination Photoelectric Detection amplifier.Be used for 1) the Photoelectric Detection numerical value of silicon Photoelectric Detection amplifier output is carried out the A/D conversion; 2) to detect numerical value on/lower limit differentiates; 3) when detection numerical value surmounts higher limit or lower limit, generate upper limit overflow pulse or lower limit overflow pulse, by corresponding I/O mouth output; 4) detect on the numerical value/lower limit judging circuit control detection numerical value of N times multiplication circuit simultaneously: do not take place when detecting numerical value/when lower limit overflows, close N times of multiplication function, detect numerical value and directly export without multiplying; When the detection numerical value generation upper limit is overflowed, open N times of multiplication function, detect numerical value and must after N times of multiplying, just export (this state is the extended mode of N times of range); Issue and give birth to limit and overflow when detecting the extended mode of numerical value, then close N times of multiplication function once again, detect numerical value and recover directly output and no longer carry out N times of multiplying (promptly getting back to the state that range is not expanded) at N times of range.
Microprocessor has the function of " memory " to the control of above-mentioned numerical operation, and when numerical value promptly not taking place overflowing, previous numerical operation rule will continue to go on.The corresponding numerical operation method that changes and continue after maintenance changes just takes place and overflows up to producing new numerical value in only when generation numerical value overflows (when generating overflow pulse), numerical operation rule.
C. state memorization and ON-OFF control circuit are made up of shift register (can adopt the MN4194 integrated circuit) and output buffered gate.Shift register moves to right and imports termination microprocessor upper limit overflow pulse output terminal, and shift register moves to left and imports termination microprocessor lower limit overflow pulse output terminal.When microprocessor produced upper limit overflow pulse, the output state occurrence logic state of shift register was the variation that moves to right of " 1 "; When microprocessor produced the lower limit overflow pulse, the output state occurrence logic state of shift register was the variation that moves to left of " 1 "; When microprocessor did not produce any overflow pulse, the output state of shift register remained unchanged.Thereby automatically synchronous working with the detection numerical value of N times multiplication circuit of microprocessor system or the state do not expanded for range, perhaps be the extended mode of N times of range, and have the function of " memory " equally.
The output state of shift register is through the conducting or the disconnection of output buffered gate control electronic switch, and when the expansion of N times of range took place, electronic switch was conducting among the present invention; When range was not expanded, electronic switch disconnected.
D. electronic switch is integrated analog switch (as the MN4066 integrated circuit), and control end connects level output buffered gate.Under the situation that electronic switch disconnects, subordinate's pulse duty factor/pulse producer is operated under the state of basic pulse duty ratio (being generally 50%) of original setting; Under the situation of electronic switch conducting, the corresponding change will take place in the duty of ratio example that subordinate's pulse duty factor/pulse producer produces, and its dutycycle only is N/one of former benchmark pulse duty factor example.
E. pulse duty factor/pulse producer is made up of time base circuit, and the typical case is applied as time-base integrated circuit NE555.Under the situation that electronic switch disconnects, i.e. range extended mode not, it produces basic pulse, and its pulse duty factor example is generally 50% (preestablishing).When Range Extension takes place when, the electronic switch conducting, the resistor network that can accurately adjust is incorporated the RC charging circuit (peripheral circuit of time-base integrated circuit) that determines pulse duty factor into, makes the RC duration of charging shorten, thereby has changed the duty ratio of production burst in the recurrence interval.Accurately adjust the resistor network that inserts through electronic switch, the dutycycle that can make production burst is N/one of former benchmark pulse duty factor, be that former benchmark duty of ratio example is 50% o'clock, the duty of ratio example that the conducting of electronic switch then makes subordinate's pulse duty factor/pulse producer produce becomes 1/N * 50%.
F. luminous power driving circuit, be used under the frequency pulse effect, the pulsed drive of the light source with works fine stability is provided, the output terminal of its input termination pulse duty factor/pulse producer, output termination light source (light emitting diode or laser diode), circuit bank becomes the negative feedback type common collector power driving circuit with good temperature stability.The pulsating direct current electric current size that built-up circuit offers light source is subjected to the influence of environment for use temperature and light source load size hardly, and only depends on that design goes up given to negative feedback component.Thereby under the constant situation in the pulsating direct current electric current working point of light source, the luminous power of light emitting diode or laser diode light source and the pulse duty factor of driving pulse are linear proportional relationship.Utilize the proportionate relationship of this linearity to implement inverse proportion control, promptly realized when the Photoelectric Detection range need be expanded inverse proportion control function light source luminescent power to light source.
G. light source, light source of the present invention is preferably selected light emitting diode or laser diode light source for use.
Obviously, if the predefined upper limit value and lower limit value of microprocessor is represented the range of linearity of Photoelectric Detection amplifier and the critical point of zone of saturation, the range of linearity and cut-off region respectively, then when detecting numerical value greater than higher limit, the Photoelectric Detection amplifier of fixed gain has been operated in the saturation region, according to formula＜1 〉, allow light source luminescent power reduce, can make testing point " drop-down " get back to the range of linearity of Photoelectric Detection amplifier according to the N ratio; When detecting numerical value less than lower limit, the Photoelectric Detection amplifier has been operated in cut-off region, allows light source luminescent power recover original intensity, can make testing point " on draw " get back to the range of linearity of Photoelectric Detection amplifier.
Therefore, exactly, circuit of the present invention is that a kind of differentiation that automatically detects numerical value allows then and breaks away from working point that the Photoelectric Detection amplifier detects linear magnification region and get back to the intellectual technology in linear amplification zone automatically and use, but the characteristics of its maximum have been used above-mentioned＜1〉formula carried out the conversion of numerical value, belongs to a kind of " virtual " technology.In the transfer process of N times of range automatic expansion, the range of linearity of Photoelectric Detection amplifier has not really been extended upward N doubly but to remain the intrinsic range of linearity constant, but we can be considered as the extension straight line of N times of range " the dotted line range of linearity ", technically think that the linearity test ability of detecting amplifier is unlimited in theory, detecting actual detected numerical value uses the N multiplying power then and carries out Equivalent Conversion and obtain accurate equivalent result, " virtual linear working point " then is on " dotted line extension straight line ", referring to Fig. 2.
Be characteristic and the advantage that further specifies base application circuit of the present invention, in conjunction with the expansion scheme of microprocessor system, referring to Fig. 3 to " based on the multiwave length spectro state carbon dioxide automatic monitoring system of long light path liquid core waveguide pipe " enforcement three light paths, two multiplying power linearity measuring range automatic expansion.
Fig. 3 uses " single N multiplying power range automatic expansion circuit of single channel light source " development to combine, adopt 3 independently silicon Photoelectric Detection amplifiers of monochromatic source beam splitting system, single high-gain, implemented " liquid core waveguide pipe " with very long light path carried out the absorption spectroanalysis of 432nm, 620nm and 740nm wavelength three monochromatic gas concentration lwevels.The monochromatic light of each wavelength is lighted in turn, and all monochromatic light passes " liquid core waveguide pipe " back and finally all detected by unique Silicon High-Gain Photoelectric Detection amplifier.
Among Fig. 3, a, b, c, d, e, f, the circuit unit of g symbology has identical or equivalent electric principle, effect and the mutual mechanism that is connected with the Elementary Function block diagram of the middle same-sign representative of Fig. 1 " single N multiplying power range automatic expansion schematic block circuit diagram of single channel light source ".But it is 3 equal modules (a circuit unit is one) that each circuit unit is expanded, with the independent processing that adapts to three-wavelength monochromatic light absorbed light and times range automatic expansion times range automatic expansion independently.The detailed circuit theory of partial circuit unit is only drawn in Fig. 3 to the treatment channel of 432rm wavelength (passage 1).
In the system, increased microprocessor system is lighted control and three independent multiplying power range automatic expansion circuit paths to the order of 3 LED pipes control.When system powers on, microprocessor b, state memorization and ON-OFF control circuit c reset, the pulse duty factor of three passages/pulse producer e at first produces the frequency pulse signal of pulse duty factor about 50%, " light source code translator " deciphered " the light source coded signal " of microprocessor output, the corresponding gating high level signal of output acts on storbing gate " with door ", and the frequency pulse signal takes turns the luminous power that the output frequency pulse controls corresponding LED pipe by " with door " circuit and at first is operated in the level that range is expanded (taking advantage of 1 grade).
When expansion takes place in the range of arbitrary wavelength channel, the pulse width of " upper limit overflow pulse " is at first extended to the level that is slightly higher than " light source coded signal " period of change by " pulse width delay circuit " shaping, and the light source gating signal of " light source code translator " output acts on the input end of clock of state memorization and ON-OFF control circuit c after " reverser " is reverse.The sequential cooperation of the two guarantees that the state memorization of selected passage is expanded the change of state and is memorized (referring to relevant U6 device, the usage of MN4194) at the terminal adaptation range that just takes place constantly of light source gating signal with ON-OFF control circuit c.The accurate inverse proportion that corresponding expansion multiplying power takes place under the closed effect of electronic switch matrix combination the frequency pulse that the pulse duty factor of respective channel/pulse producer e circuit produces change and the luminous power of control LED pipe to the level of this ratio.
The range that identical mechanism occurs in equally when arbitrary wavelength channel takes place to produce " lower limit overflow pulse " output but microprocessor does not produce " upper limit overflow pulse " by the change procedure of height expansion multiplying power to low expansion multiplying power.
Single N multiplying power range automatic expansion of " single N multiplying power range automatic expansion circuit of single channel light source " is developed into two continuous times range automatic expansion of 2 multiplying powers, 4 multiplying powers of each wavelength treatment channel in this expansion is used.Owing to adopted shift register MN4194, so the conversion sequence of the range automatic expansion of each wavelength channel takes advantage of 2 all for taking advantage of 1, take advantage of 4, or take advantage of 4, take advantage of 2, take advantage of 1 inverted order.
3 all corresponding real-time range states of LED pipe all are stored in state memorization and ON-OFF control circuit c, corresponding change only just takes place when the state of range changes, thereby has realized together with the automatic expansion of taking advantage of 1 grade of (basic gear) three multiplying power linearity measuring range and memory in real time.
In system, because " incoherentness " of each passage, thereby under the sequential control of " light source gating signal ", realized continuous detecting to the no step range of the three light source beam splitting system spectrum that adopt single photoelectric detector.
Because the photoelectric detector that the present invention exists is the Photoelectric Detection amplifier of fixed gain and do not have the problem of internal conversion device, so whether its issuable detection numerical error in range automatic expansion process only depends on previous accurate according to the adjustment of the ratio of range to light source luminescent power.
The scope of utilizing of the present invention is confined to application in absorbing the class spectral instrument.Use the adjustment of electronic switch owing in fact relate in the range automatic expansion process to the Photoelectric Detection amplifier, thus be more suitable for photoelectron only the skin peace to receiving the range conversion of low light level signal high resistant detecting amplifier of peace level.Simultaneously owing to the power control to light source has the effect of " memory ", so can realize the continuous detecting of the multiple light courcess spectrum of no step range for the absorption class spectral instrument that adopts single photoelectric detector, a plurality of light sources.
Claims (7)
1, absorption analytical instrument optical detection measurement range expanding circuit is characterized in that being provided with:
A. the silicon Photoelectric Detection amplifier that has fixed gain;
B. microprocessor system, microprocessor system is provided with A/D converter, detect on the numerical value/the lower limit judging circuit, detect numerical value of N times multiplication circuit and the upper limit/lower limit overflow pulse generator, wherein, the detection numerical simulation signal output part of A/D converter input termination Photoelectric Detection amplifier, detect on the numerical value/lower limit judging circuit input termination A/D converter output terminal, detect numerical value of N times mlultiplying circuit and the upper limit/lower limit overflow pulse generator and be controlled by and detect on the numerical value/output state of lower limit judging circuit;
C. state memorization and ON-OFF control circuit are made up of shift register and output buffered gate, and shift register moves to right and imports termination microprocessor upper limit overflow pulse output terminal, and shift register moves to left and imports termination microprocessor lower limit overflow pulse output terminal;
D. electronic switch is integrated analog switch, and electronic switch controling end connects level output buffered gate;
E. pulse duty factor/pulse producer is made up of time base circuit, and pulse duty factor/pulse producer connects electronic switch;
F. luminous power driving circuit, the output terminal of its input termination pulse duty factor/pulse producer, output termination light source;
G. light source is selected from light emitting diode or laser diode light source.
2, absorption analytical instrument optical detection measurement range expanding circuit as claimed in claim 1, it is variable gain resistance that the silicon Photoelectric Detection amplifier that it is characterized in that having fixed gain is selected sampling resistor for use, the representative value of sampling resistor is 1G ohm, and the electrooptical device of cooperation is a S1226-44BQ type silicon photoelectric diode.
3, absorption analytical instrument optical detection measurement range expanding circuit as claimed in claim 1 is characterized in that microprocessor system is selected from the PIC16F77 single-chip microcomputer.
4, absorption analytical instrument optical detection measurement range expanding circuit as claimed in claim 1, the output state that it is characterized in that the shift register of state memorization and ON-OFF control circuit is controlled the conducting or the disconnection of electronic switch through exporting buffered gate, when the expansion of N times of range took place, electronic switch was conducting; When range was not expanded, electronic switch disconnected.
5, absorption analytical instrument optical detection measurement range expanding circuit as claimed in claim 1 is characterized in that integrated analog switch is selected from the MN4066 integrated circuit.
6, absorption analytical instrument optical detection measurement range expanding circuit as claimed in claim 1 is characterized in that under the situation that electronic switch disconnects, and subordinate's pulse duty factor/pulse producer is operated under the state of basic pulse duty ratio of original setting; Under the situation of electronic switch conducting, the duty of ratio example that subordinate's pulse duty factor/pulse producer produces is N/one of former benchmark pulse duty factor example.
7, absorption analytical instrument optical detection measurement range expanding circuit as claimed in claim 1 is characterized in that pulse duty factor/pulse producer is selected from time-base integrated circuit NE555.
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|---|---|---|---|---|
| US5042946A (en) * | 1990-05-02 | 1991-08-27 | Hitachi, Ltd. | Atomic absorption spectrophotometric method and apparatus |
-
2005
- 2005-11-10 CN CNB2005101244343A patent/CN100489497C/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5042946A (en) * | 1990-05-02 | 1991-08-27 | Hitachi, Ltd. | Atomic absorption spectrophotometric method and apparatus |
Non-Patent Citations (2)
| Title |
|---|
| WFD－Y_2型原子吸收分光光度计的改装. 何长一，卢志昌.云南冶金，第1977年第6期. 1977 |
| WFD－Y_2型原子吸收分光光度计的改装. 何长一，卢志昌.云南冶金，第1977年第6期. 1977 * |
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