CN201917560U - Baseline automatic zeroing device for electron capture detector - Google Patents
Baseline automatic zeroing device for electron capture detector Download PDFInfo
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- CN201917560U CN201917560U CN201020626850XU CN201020626850U CN201917560U CN 201917560 U CN201917560 U CN 201917560U CN 201020626850X U CN201020626850X U CN 201020626850XU CN 201020626850 U CN201020626850 U CN 201020626850U CN 201917560 U CN201917560 U CN 201917560U
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Abstract
A baseline automatic zeroing device for an electron capture detector comprises an automatic zeroing circuit and a detection circuit, wherein the automatic zeroing circuit is arranged on the detection circuit, and forms a double closed-loop structure with the detection circuit; the detection circuit comprises a closed-loop structure formed by a pulse generator, a charge amplifier and a voltage frequency converter, and a detecting pool connected with the output terminal of the pulse generator; the automatic zeroing circuit comprises a micro-controller connected with the output terminal of the pulse generator, and an ADC (Analog-to-Digital Converter) connected with the output terminal of the micro-controller; and the output terminal of the ADC is also connected with the input terminal of the charge amplifier, then goes back to the pulse generator through the voltage frequency converter, and forms the other closed-loop structure. By regulating the output voltage of the charge amplifier, the output frequency of the voltage frequency converter is controlled, the applying frequency of the pulse electric field of the pulse generator is changed, and thus the electric field charge quantity used for forming the baseline and transported into the detecting pool is regulated, so as to regulate the baseline in real time. Therefore, the utility model can ensure that the baseline can stay stable on any conditions.
Description
Technical field
The utility model relates to a kind of Automatic Zero Set, particularly a kind of baseline Automatic Zero Set that is used for the electron capture detector of gas chromatography instrument.
Background technology
Electron capture detector (hereinafter to be referred as the ECD detecting device) is the detecting device of a kind of high sensitivity, high selectivity, and is responsive especially to the electronegativity material; It is applied in the gas chromatography instrument more, and one of maximum detecting device is used in the residual toxicity amount and the environmental monitoring fields such as (water, soil, atmospheric pollution) that become in the present biosome.
Described ECD detecting device mainly is made up of gas circuit and circuit:
On the gas circuit, provide the carrier gas of certain pressure flow velocity, tested gas-entrained is entered the ECD detection cell; Detection cell is built-in with radioactive source, with carrier gas molecules ionization, produces a large amount of free electrons.
On the circuit, apply the impulse electric field of a fixed width at the detection cell end, make free electron that directed moving be taken place, produce electric current, this electric current promptly is the baseline (also claiming base flow) of ECD detecting device.
By the isolated tested gas stream of chromatographic column, enter successively in the ECD detection cell with carrier gas.Because these tested gas molecule electrophilics, it is caught free electron in a large number and discharges outside the pond, has caused the minimizing of directed mobile free electron, causes that baseline descends.
In order to keep the stable of baseline, generally adopt the way of compensation on the circuit, or increase or reduce the frequency that applies of impulse electric field, impel some more or less free electron orientation to move, reached the purpose of steady baseline.
Extract the DC component signal of the impulse electric field waveform of described changeable frequency, will be wherein peak type collection of illustrative plates, promptly thereon each of baseline and base goes out the peak and shows: the gas composition that different peaks is corresponding different; The height or the area at peak are proportional to gas concentration.
, impulse electric field amplitude certain when described radioactive source sensitivity and constant width, nebulizer gas pressure flow velocity are constant, when temperature constant and circuit parameter are constant, baseline just can be stablized, but is difficult to realize.Therefore, must keep the long-term stability of baseline by zeroing; Baseline stability, it is stable then to go out the peak, could be precisely to the measurement of concetration of gas.
ECD detecting device does not in the market generally have the automatic zero set (AZS) function.What have does not have a zeroing function at all; What have only has a hand reset function.Thereby those ECD detecting devices, owing to can't accomplish round-the-clock running, in as the field of air quality surveillance, just can't use; If need hand reset, then need operating personnel to intervene; And when returning to zero, all to demarcate with standard model at every turn, extremely inconvenient.
The utility model content
The purpose of this utility model provides a kind of baseline Automatic Zero Set of electron capture detector, and the baseline of ECD detecting device be need not artificial adjustment, can maintain a long-term stability automatically, has degree of precision with the mensuration that guarantees material concentration.
In order to achieve the above object, the technical solution of the utility model provides a kind of baseline Automatic Zero Set of electron capture detector, comprises to be arranged on the automatic zero set (AZS) loop of detecting on the loop;
Described detection loop comprises the closed loop configuration that pulse producer, charge amplifier, voltage-frequency converter form, and the detection cell that is connected with described pulse producer output terminal;
Described automatic zero set (AZS) loop comprises the microcontroller that is connected with described pulse producer output terminal, and the analog to digital converter that is connected with described microcontroller output terminal; The output terminal of described analog to digital converter also is connected with the input end of described charge amplifier, gets back to described pulse producer via described voltage-frequency converter again, forms another closed loop configuration;
Described pulse producer output impulse electric field makes a part of electric field electric charge wherein, exports in the described detection cell, and the baseline that participates in measured matter forms;
Described microcontroller is controlled described analog to digital converter output zeroing signal by detecting baseline value, makes another part electric field electric charge of described zeroing signal and described pulse producer output, and stack is transported to described charge amplifier;
By regulating the output voltage of described charge amplifier, control the output frequency of described voltage-frequency converter, change described pulse producer impulse electric field apply frequency, and then adjust to be delivered to and be used for the electric field quantity of electric charge that baseline forms in the described detection cell, thereby regulate baseline.
Described pulse producer comprises voltage source, electronic switch and the charge pump electric capacity that connects successively, the output terminal of described voltage-frequency converter is connected with described electronic switch, and controls its switching frequency.
Described charge pump electric capacity exports described detection cell to, also exports the inverting input of described charge amplifier to by series resistor.
Described automatic zero set (AZS) loop also comprises the filtering link, and it is arranged between the input end of the output terminal of described electronic switch and described microcontroller, described electronic switch is communicated with at interval with described voltage source or disconnects the square-wave signal that forms carry out filtering.
Described microcontroller is gathered the mean value of described square-wave signal as described baseline value, and described baseline value and setting value are compared, and calculates the control signal of output to described analog to digital converter.
Described analog to digital converter output zeroing signal is a current signal, and by series resistor, output zeroing voltage is to the inverting input of described charge amplifier.
Described detection loop also comprises the output terminal that is arranged on described charge amplifier and the feedback capacity on the inverting input.
Compared with prior art, the baseline Automatic Zero Set of electron capture detector in the utility model, its advantage is: by the microcontroller continuous detecting baseline value in described automatic zero set (AZS) loop, control analog to digital converter output regulated quantity, and stack exports the charge amplifier that detects the loop to, regulate the output of V/F voltage-frequency converter, realize the adjustment of baseline.
The utility model can round-the-clock automatic operation, when baseline changes at any time, can effectively suppress from the inside and outside various disturbance factors of ring, carries out the compensation zeroing of baseline in real time, guarantees that baseline can both keep stable under any condition; Once demarcate, the term of validity surpasses 100 days, and the long-term stability setting value deviation of baseline (promptly with) is better than 1%.
Owing to be provided with microcontroller, make device described in the utility model can realize digitizing and intellectuality, and characteristic is hard, be subjected to such environmental effects little.Generalized case was upgraded once, more by a small margin with 10 seconds, had taken into account response and accuracy requirement; When baseline value departed from normal value for a long time, the renewal amplitude of increasing modulus converter then reached the purpose of quick readjustment.
Description of drawings
Fig. 1 is the electrical block diagram of the baseline Automatic Zero Set of the utility model electron capture detector.
Embodiment
Below in conjunction with description of drawings embodiment of the present utility model.
As shown in Figure 1, the baseline Automatic Zero Set of electron capture detector described in the utility model (ECD) is realized by the double-loop circuit structure that detects loop and automatic zero set (AZS) loop.
In a kind of typical described detection loop, comprise+30V voltage source 21, electronic switch 22, charge pump electric capacity 23, detection cell 24, resistance 25, charge amplifier 26 and feedback capacity 27, V/F voltage-frequency converter 28.
In certain moment, electronic switch 22 closures are connected voltage source 21 and charge pump electric capacity 23; After charge pump electric capacity 23 was squeezed into circuit with the electric field electric charge of its generation, electronic switch 22 disconnected.For detection cell 24, be equivalent to apply a momentary pulse electric field; At this moment, described electric field part of charge enters in this detection cell 24, makes directed the moving of free electron of carrier gas in the detection cell 24 form baseline.
The remainder of electric field electric charge enters the inverting input of charge amplifier 26 through resistance 25; The voltage swing that charge amplifier 26 exports V/F voltage-frequency converter 28 to changes, and makes V/F voltage-frequency converter 28 export the frequency shift of electronic switch 22 to, and the frequency that applies of impulse electric field changes immediately, forms closed-loop control.
When the increase of measured matter concentration, its free electron number at detection cell 24 ITs increases, and then forms the corresponding minimizing of electric charge number of baseline, and baseline is descended.For steady baseline, need the charge number total amount of this minimizing of compensation; Because the amount of charge of each charge pump electric capacity 23 outputs is fixed, the number of impulse electric field is increased, could in the identical time, the electric charge number of input charge amplifier 26 be increased; And then the increase of the output voltage of charge amplifier 26, the output frequency of V/F voltage-frequency converter 28 is increased, the number of impulse electric field increases; Repeat above process, realize the compensation that baseline is descended.
When measured matter concentration reduced, compensation process was similar to the above, by reducing the frequency that applies of impulse electric field, reduced the impulse electric field number, and the electric charge number of input charge amplifier 26 is reduced, and had compensated the rising of baseline.
From described electronic switch 22, behind the filtering link 11 that the described automatic zero set (AZS) of process loop is provided with, microcontroller 12, digital to analog converter, the resistance 14, insert the inverting input of described charge amplifier 26, get back to described electronic switch 22 through V/F voltage-frequency converter 28, form another closed loop configuration thus.
Wherein, microcontroller 12 uses the PIC16F886 type; Digital to analog converter uses the D/A integrated chip of 12 high precision, full scale 2.5V; Resistance 14 is 1G ohm; V/F voltage-frequency converter 28 uses the VFC32 type; Charge amplifier 26 uses the extremely low biasing of the high-performance of AD549 type to transport amplifier.
By the pulsed frequency control of V/F voltage-frequency converter 28 outputs, described electronic switch 22 opens and closes and the output square-wave signal at interval, after handling through filtering link 11, gathers conversion by microcontroller 12, obtains the mean value of this square-wave signal; Described mean value is equivalent to the baseline value of electron capture detector (ECD).
Described microcontroller 12 compares this baseline value and setting value, with the PID regulative mode, the control digital to analog converter produces a little current signal, resistance 14 through serial connection forms a zeroing voltage, and be superimposed upon the inverting input of described charge amplifier 26, participate in the automatic adjusting in described detection loop.
When baseline value is big, when promptly baseline rises, then reduce the output current of digital to analog converter, reduce the input of described charge amplifier 26; Afterwards, with similar in the above-mentioned detection loop, the output voltage of charge amplifier 26 reduces, and the output frequency of V/F voltage-frequency converter 28 reduces, and the number of impulse electric field reduces, and the control baseline descends.Vice versa.
When measured matter enters detection cell 24, in peak type collection of illustrative plates, can occur the peak that of baseline and this material simultaneously, yet it is same signal physically, microcontroller 12 will be difficult to differentiate.
To go out peak-to-peak signal normally for fear of the microprocessor in automatic zero set (AZS) loop and be regulated, and cause material is gone out the influence that the peak detects as background signal.Generally, in microcontroller 12, be provided with and carry out a baseline zeroing per 10 seconds, and analog to digital converter 13 is to adjust output by a small margin, to take into account the requirement of response and precision.
For example, measured matter concentration is low excessively, and it is also lower that it goes out the peak, thereby peak area is little, and the peak type is narrow, and the above-mentioned 10 seconds time intervals once are greater than its peak width; Perhaps only whole through a mistuning, and, can not cause unacceptable influence to the result because the amplitude of adjusting is very little.
When measured baseline value departs from setting value 50%, then might be the peak, microprocessor is suspended regulate, and pick up counting; Surpass 200 seconds if this reference value departs from, illustrate that this is not the peak, but baseline value excessively departed from, then controlled analog to digital converter 13, realized the quick readjustment of baseline with by a relatively large margin variable quantity output.
In sum, the loop of automatic zero set (AZS) described in the utility model is by microcontroller 12 continuous detecting baseline values, control analog to digital converter 13 output regulated quantitys, and stack exports the charge amplifier 26 that detects the loop to, the output of adjusting V/F voltage-frequency converter 28, the adjustment of realization baseline.
Compared with prior art, the utility model can round-the-clock automatic operation, when baseline changes at any time, can effectively suppress from the inside and outside various disturbance factors of ring, carries out the compensation zeroing of baseline in real time, guarantees that baseline can both keep stable under any condition; Once demarcate, the term of validity surpasses 100 days, and the long-term stability setting value deviation of baseline (promptly with) is better than 1%.
Owing to be provided with microcontroller 12, make device described in the utility model can realize digitizing and intellectuality, and characteristic is hard, be subjected to such environmental effects little.Generalized case was upgraded once, more by a small margin with 10 seconds, had taken into account response and accuracy requirement; When baseline value departed from normal value for a long time, the renewal amplitude of increasing modulus converter 13 then reached the purpose of quick readjustment.
Although content of the present utility model has been done detailed introduction by above preferred embodiment, will be appreciated that above-mentioned description should not be considered to restriction of the present utility model.After those skilled in the art have read foregoing, for multiple modification of the present utility model with to substitute all will be conspicuous.Therefore, protection domain of the present utility model should be limited to the appended claims.
Claims (7)
1. the baseline Automatic Zero Set of an electron capture detector is characterized in that, comprises to be arranged on the automatic zero set (AZS) loop of detecting on the loop;
Described detection loop comprises the closed loop configuration that pulse producer, charge amplifier (26), voltage-frequency converter (28) form, and the detection cell (24) that is connected with described pulse producer output terminal;
Described automatic zero set (AZS) loop comprises the microcontroller (12) that is connected with described pulse producer output terminal, and the analog to digital converter (13) that is connected with described microcontroller (12) output terminal; The output terminal of described analog to digital converter (13) also is connected with the input end of described charge amplifier (26), gets back to described pulse producer via described voltage-frequency converter (28) again, forms another closed loop configuration;
Described pulse producer output impulse electric field makes a part of electric field electric charge wherein, exports in the described detection cell (24), and the baseline that participates in measured matter forms;
Described microcontroller (12) is controlled described analog to digital converter (13) output zeroing signal by detecting baseline value, makes another part electric field electric charge of described zeroing signal and described pulse producer output, and stack is transported to described charge amplifier (26);
By regulating the output voltage of described charge amplifier (26), control the output frequency of described voltage-frequency converter (28), change described pulse producer impulse electric field apply frequency, and then adjust to be delivered to and be used for the electric field quantity of electric charge that baseline forms in the described detection cell (24), thereby regulate baseline.
2. the baseline Automatic Zero Set of electron capture detector according to claim 1, it is characterized in that, described pulse producer comprises voltage source (27), electronic switch (22) and the charge pump electric capacity (23) that connects successively, the output terminal of described voltage-frequency converter (28) is connected with described electronic switch (22), and controls its switching frequency.
3. as the baseline Automatic Zero Set of electron capture detector as described in the claim 2, it is characterized in that, described charge pump electric capacity (23) exports described detection cell (24) to, also exports the inverting input of described charge amplifier (26) to by series resistor (25).
4. as the baseline Automatic Zero Set of electron capture detector as described in the claim 3, it is characterized in that, described automatic zero set (AZS) loop also comprises filtering link (11), it is arranged between the input end of the output terminal of described electronic switch (22) and described microcontroller (12), and described electronic switch (22) is communicated with at interval with described voltage source (27) or the square-wave signal that disconnects formation carries out filtering.
5. as the baseline Automatic Zero Set of electron capture detector as described in the claim 4, it is characterized in that, described microcontroller (12) is gathered the mean value of described square-wave signal as described baseline value, and described baseline value and setting value compared, calculate the control signal of output to described analog to digital converter (13).
6. as the baseline Automatic Zero Set of electron capture detector as described in the claim 5, it is characterized in that, described analog to digital converter (13) output zeroing signal is a current signal, and by series resistor (14), output zeroing voltage is to the inverting input of described charge amplifier (26).
7. as the baseline Automatic Zero Set of electron capture detector as described in the claim 6, it is characterized in that described detection loop also comprises output terminal and the feedback capacity on the inverting input (27) that is arranged on described charge amplifier (26).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201020626850XU CN201917560U (en) | 2010-11-26 | 2010-11-26 | Baseline automatic zeroing device for electron capture detector |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201020626850XU CN201917560U (en) | 2010-11-26 | 2010-11-26 | Baseline automatic zeroing device for electron capture detector |
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| CN201917560U true CN201917560U (en) | 2011-08-03 |
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| CN201020626850XU Expired - Fee Related CN201917560U (en) | 2010-11-26 | 2010-11-26 | Baseline automatic zeroing device for electron capture detector |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105891396A (en) * | 2015-01-02 | 2016-08-24 | 山东鲁南瑞虹化工仪器有限公司 | Electric fishing detector lining device of gas chromatograph |
| CN106610407A (en) * | 2015-10-26 | 2017-05-03 | 株式会社岛津制作所 | Sensitivity automatic detection method and device of electron capture detector |
| CN112782507A (en) * | 2020-12-30 | 2021-05-11 | 苏州中科先进技术研究院有限公司 | STM 32-based weak electronic signal capturing and collecting system |
-
2010
- 2010-11-26 CN CN201020626850XU patent/CN201917560U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105891396A (en) * | 2015-01-02 | 2016-08-24 | 山东鲁南瑞虹化工仪器有限公司 | Electric fishing detector lining device of gas chromatograph |
| CN106610407A (en) * | 2015-10-26 | 2017-05-03 | 株式会社岛津制作所 | Sensitivity automatic detection method and device of electron capture detector |
| CN112782507A (en) * | 2020-12-30 | 2021-05-11 | 苏州中科先进技术研究院有限公司 | STM 32-based weak electronic signal capturing and collecting system |
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| Date | Code | Title | Description |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20110803 Termination date: 20171126 |
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| CF01 | Termination of patent right due to non-payment of annual fee |