CN209416924U - Front end circuit and multichannel atomic fluorescence detector including the front end circuit - Google Patents
Front end circuit and multichannel atomic fluorescence detector including the front end circuit Download PDFInfo
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- CN209416924U CN209416924U CN201821791005.0U CN201821791005U CN209416924U CN 209416924 U CN209416924 U CN 209416924U CN 201821791005 U CN201821791005 U CN 201821791005U CN 209416924 U CN209416924 U CN 209416924U
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Abstract
The utility model provides a kind of front end circuit and the multichannel atomic fluorescence detector including the front end circuit, the front end circuit is used to low current signal being converted to significantly voltage signal, including resistance feedback type I-V conversion circuit, inverter cricuit and amplifier type amplifying circuit；The I-V conversion circuit is resistance feedback type I-V conversion circuit, and the output of I-V conversion circuit is directly proportional to feedback resistance R4；The negative feedback resistor R3 of amplifying circuit is adjustable resistance, to adjust the gain of amplifying circuit.Low current signal is converted to significantly voltage signal by the utility model front end circuit, when not increasing the negative high voltage of PMT in detector, increases substantially the detection sensitivity of detector；Multichannel atomic fluorescence detector detects while realizing multiple element using single detector timeslice rotation work mode, simplifies apparatus structure, in turn avoids the interference between multiple sense channels, improves the reliability and accuracy of detection data.
Description
Technical field
The utility model relates to the electronic circuit systems in atomic spectroscopic analysis technical field, and in particular to one kind is suitable for
The front end circuit of Detection of Weak Signals and multichannel atomic fluorescence detector including the front end circuit.
Background technique
Currently, atomic fluorescence detector is common spectral class analysis instrument, its working principle is that being contained using excitation light source irradiation
There is the atom vapor of certain density element to be measured, so that ground state atom transits to excitation state, issues atomic fluorescence, measure atom
The content of the element in sample to be tested, i.e., the fluorescence signal intensity obtained measurement and a system can be calculated in the intensity of fluorescence
The fluorescence signal intensity value comparison for arranging the known elemental standards content, is calculated the content of tested element.
Atomic fluorescence detection sensitivity and detection limit are two key indexes for reflecting atomic fluorescence detector performance, to improve original
The detection sensitivity of sub- luminoscope reduces its detection limit, and the mode being usually taken is used more first is that using stronger light source
Good atomizer, third is that increasing the negative high voltage of photomultiplier tube (PMT) in detector suitably to improve gain amplifier.Due to miscellaneous
The presence of astigmatism takes the above method that can not effectively remove the influence of stray light, for example, by increasing PMT in detector
Negative high voltage come when improving gain amplifier, while amplifying effective atomic fluorescence signal, stray light will be also amplified, meanwhile, by
Amplify the limit with the conversion range of analog electrical signal to digital electric signal by device itself and circuit design in the electric signal of circuit
System can not have very wide dynamic range, and the method effect of this gain amplifier is very limited.
According to atomic fluorescence detector number of active lanes, atomic fluorescence detector can be divided into single channel atomic fluorescence detector and multichannel atom
Luminoscope.Existing multichannel atomic fluorescence detector is usually that multiple mutually independent channels are arranged, i.e., multiple excitation light source channels
It is designed with corresponding sense channel, in use, one element of single channel measurement, each channel are mutually indepedent.In this way, atom
It is more complicated in luminoscope structure, and easily interfered between multiple sense channels, thus influence detection data reliability and
Accuracy.
Utility model content
To solve the above-mentioned problems, the utility model provides a kind of front end circuit, which is suitable for small-signal
Detection.
The above-mentioned purpose of the utility model is realized by following technical scheme:
A kind of front end circuit, for low current signal to be converted to significantly voltage signal, including I-V conversion electricity
Road, inverter cricuit (032) and amplifying circuit, the I-V conversion circuit are resistance feedback type I-V conversion circuit (031), and I-V turns
The output for changing circuit (031) is directly proportional to feedback resistance R4；Amplifying circuit is amplifier type amplifying circuit (033), gain AfGreatly
Small directly proportional to the ratio of negative feedback resistor R3 and divider resistance R5, the negative feedback resistor R3 of amplifying circuit is adjustable resistance, is used
To adjust the gain of amplifying circuit (033).
In above-mentioned front end circuit, be provided between the I-V conversion circuit (031) and inverter cricuit (032) capacitor C2 and
The partiting dc circuit that resistance R1 is formed.
In above-mentioned front end circuit, the amplifying circuit (033) is provided with offset adjustment circuit, to adjust output signal
DC offset.
The utility model also provides a kind of multichannel atomic fluorescence detector with above-mentioned front end circuit, and a kind of multichannel is former
Sub- luminoscope includes multichannel excitation light source (02) and the detector for capturing, detecting fluorescence signal, and the detector includes light
Electric multiplier tube (05), mainboard (01) and signal processing circuit (04) are integrated with processor (011), digital-to-analogue conversion on mainboard (01)
Module (012), analog-to-digital conversion module (014) and interface module (013), the detector further include above-mentioned front end circuit (03),
Processing of the output signal through signal processing circuit (04) of front end circuit (03) is converted to number through analog-to-digital conversion module (014)
Signal is sent to processor (011).
In above-mentioned multichannel atomic fluorescence detector, the signal processing circuit (04) includes that filter circuit (041) and peak value take
Sample circuit (042), filter circuit (041) be low-pass filter, for the signal that front end circuit (03) export be filtered with
Smoothly；Peak sample circuit (042) is for completing the sampling operation in scheduled sampling time.
In above-mentioned multichannel atomic fluorescence detector, front end circuit (03) is individually integrated on a front end circuit plate, and and photoelectricity
The output of multiplier tube (05) connects, and front end circuit plate and photomultiplier tube (05) are hermetically sealed together.
Above-mentioned multichannel atomic fluorescence detector further includes a display touch screen (00), and display touch screen (00) passes through interface module
(013) processor (011) is accessed.
Using the above technological means, the utility model obtains following technical effect:
The utility model front end circuit combines shape using resistance feedback type I-V conversion circuit, inverter cricuit and amplifying circuit
At two-stage amplifying circuit, pA grades of current signal is converted into mV grades of voltage signal, it can be achieved that not increasing PMT in detector
Negative high voltage in the case where, increase substantially the detection sensitivity of detector；The utility model multichannel atomic fluorescence detector uses
Single detector timeslice rotation work mode detects while realizing multiple element, not only simplifies apparatus structure, in turn avoids
Interference between multiple sense channels, to improve the reliability and accuracy of detection data.
Detailed description of the invention
Fig. 1 is the structural block diagram of the detector of the utility model multichannel atomic fluorescence detector；
Fig. 2 is that photomultiplier tube is formed by electric impulse signal figure in detector；
Fig. 3 is the circuit diagram of the utility model front end circuit；
Fig. 4 is the circuit diagram of existing front end circuit；
Fig. 5 is the flow chart of the detection process of the utility model two-channel atomic luminoscope；
Fig. 6 is the fluorescence detection structure screenshot obtained using the utility model atomic fluorescence detector.
Appended drawing reference indicates in figure are as follows:
00: display touch screen；
01: mainboard, 011: processor (MCU), 012: D/A converter module (DAC), 013: interface module, 014: modulus turns
Change circuit (ADC)；
02: excitation light source (fluorescent tube)；
03: front end circuit, 031:I-V conversion circuit, 032: inverter cricuit, 033: amplifying circuit；U1: the first operation amplifier
Device, U2: second operational amplifier, U3: third operational amplifier；
04: signal processing circuit, 041: filter circuit, 042: peak sample circuit；
05: photomultiplier tube (PMT), 9:PMT ground pin；11:PMT negative pressure pin；10:PMT output pin；
06: pulsed constant current supply；
Ip:PMT exports electric current；Voltage pulse peak value after Vp:I-V conversion；Af: the gain of third operational amplifier；
Vop: the voltage pulse output peak value of front end circuit.
Specific embodiment
Below in conjunction with the drawings and specific embodiments, to the utility model front end circuit and with the multichannel of the front end circuit
Atomic fluorescence detector is described in detail.
As shown in Figure 1, the utility model multichannel atomic fluorescence detector includes a detector, detector is used for capturing
Atomic fluorescence signal is analyzed and processed the content that tested element is calculated, including photomultiplier tube (PMT) 05, mainboard 01,
Front end circuit 03 and signal processing circuit 04, in which:
Processor (MCU) 011, D/A converter module (DAC) 012, analog-to-digital conversion module (ADC) are integrated on mainboard 01
014 and interface module 013, MCU are the core of detector, are the brains of entire detector, are responsible for detector each section circuit
Management and timing control, MCU are built-in with computing module, and D/A converter module (DAC) 012 exports certain duty ratio, predetermined amplitude
Control wave of the electric pulse through the simulation output interface in interface module 013 as the pulsed constant current supply 06 of a high pressure,
Pulsed constant current supply 06 exports the electric pulse of 30mA-150mA to excitation light source (fluorescent tube) 02 under the action of control wave, makes
Excitation light source 02 emits the exciting light of element to be detected.Meanwhile MCU control signal processing circuit 04 handle PMT capture should
The fluorescence signal of element.
The atomic fluorescence signal that photomultiplier tube (PMT) 05 captures forms electric impulse signal as shown in Figure 2, the signal
It is 10-9The low current signal of A (pA) range, in detection process, it usually needs the current signal is converted into voltage signal, so
After carry out corresponding method, filtering etc. processing, currently used I-V conversion circuit is as shown in figure 4, the defect of the circuit is resistance
R9 etc. consumes a large portion weak current, leads to the reduction of I-V converting sensitivity, so that detector entirety detection limit increases
It is high.
As shown in figure 3, the utility model front end circuit 03 will using succinct resistance feedback type I-V conversion circuit 031
The weak current pulse signal of PMT output is converted to significantly voltage pulse signal, and will be positive by inverter cricuit 032
Pulses switch is negative pulse, then direct impulse is further amplified through level-one amplifying circuit 033, and front end circuit 03 uses two
Grade amplifying circuit, increases the sensitivity of detector.
In embodiment shown in Fig. 3, the second operational amplifier U2 in I-V conversion circuit 031, which is selected, has low input inclined
The operational amplifier CA3140 for setting electric current selects the feedback resistance R4 of 5.1M, the peak value of the voltage pulse after conversion are as follows:
Vp=Ip × R4 (1)
The first operational amplifier U1 in inverter cricuit 032 selects MOS type operational amplifier TL081, amplifying circuit 033
In third operational amplifier U3 select have ultra-low noise general-purpose operation amplifier 0P07；I-V conversion circuit 031 it is defeated
Stopping direct current electric current (preventing the interference between the circuit of front and back), which is formed by, through capacitor C2 and resistance R1 out enters negater circuit 032,
The negative pulse that inverter cricuit 032 exports is after amplifying circuit 033, the gain of this grade of amplifying circuit are as follows:
Af=-R3/R5=- (10~100) (2)
Wherein, the resistance R3 in amplifying circuit 033 and resistance R11 are set as adjustable resistance, are respectively used to adjust detector
Sensitivity and front end circuit 03 output signal offset.Therefore, in embodiment shown in Fig. 3, the spirit of front end circuit
Sensitivity is reachable: Vop/Ip=1250mV/10nA.
After the voltage pulse signal that front end circuit 03 exports is handled through signal processing circuit 04, obtain stable and accurate
It is sent to after digital signal in processor (MCU) 011 and is calculated and be further processed.
As shown in Figure 1, signal processing circuit 04 includes filter circuit 041 and peak sample circuit 042.Filter circuit 041
Signal for exporting to front end circuit 03 is filtered and smoothly, generally low-pass filter, is also possible to other filters；
Peak sample circuit 042 completes the sampling operation in scheduled sampling time.Signal processing circuit 04 will acquire signal and turn through modulus
Mold changing block (ADC) 014 is converted into digital signal and is sent to MCU, and member to be measured is calculated by built-in computing module 011
The fluorescence intensity detected value of element, the detected value is generally by taking all peak values within preset sample time and as member to be measured
The fluorescence intensity of element, the intensity value is directly proportional to the content of element to be measured, and therefore, the standard sample by comparing element to be measured is surveyed
The content value of element to be measured can be obtained in the fluorescence intensity obtained.
Above-mentioned processor (MCU) 011 and its peripheral circuit, signal processing circuit 04 and for electrical component power supply
AC-DC power supply can be integrated on one piece of mainboard 01, and front end circuit 03 is individually integrated on a front end circuit plate, be connect with PMT
And seal, prevent external light influence；The cathode voltage (- HV) of PMT by mainboard power interface access PMT negative pressure pin 11
It provides, is grounded after the divider resistance R12 of PMT ground pin connection afterbody multiplier stage, the access of PMT output pin 10 second
The inverting input terminal of operational amplifier U2.+ 9V needed for front end circuit 03, -9V, GND are provided by the power interface of mainboard.
The utility model multichannel atomic fluorescence detector further includes display touch screen 00, and display touch screen 00 passes through interface module
013 is electrically connected to processor (MCU) 011, and the operation information for atomic fluorescence detector is shown, parameter setting and operation control.With
Under described by taking two-channel atomic luminoscope as an example the utility model multichannel atomic fluorescence detector two kinds of elements and meanwhile detection mistake
Journey.
The utility model two-channel atomic luminoscope swashing respectively as element A and B element using two-way excitation light source 02
Light emitting source, two-way excitation light source are respectively defined as the road A excitation light source and the road B excitation light source, may be implemented in certain period of time
Content that is interior while detecting two kinds of elements.The different and prior art, the two-way excitation of the utility model two-channel atomic luminoscope
Light source shares a detector, and the MCU control road A excitation light source and the road B excitation light source are worked by the way of timeslice rotation, joined
According to Fig. 5, i.e., timeslice 1 starts timing, the excitation spectrum of the starting road A excitation light source transmitting element A, while detector starts to detect
Element A fluorescence signal, until 1 timing of timeslice terminates, the closing road A excitation light source, detector stops detection；Timeslice 2 starts
Timing, the excitation spectrum of the starting road B excitation light source transmitting B element, while detector starts to detect B element fluorescence signal, until
2 timing of timeslice terminates, and closes the road B excitation light source, and detection stops detection；It is repeated in the above process, until this was detected
Journey terminates.
Interval time between above-mentioned detection process time leaf length is timely between piece is set by MCU, depends primarily on MCU
It is sent to the pulse drive signal feature of excitation light source 02.For example, using cycle T for 4000uS, pulsewidth t in the present embodimentwFor
200uS, duty ratio DR are the pulse drive signal of 20:1, and the timeslice of the road Ze Mei excitation light source work is 200uS, rotation per second
Work 250 times, interval time 1800uS.Sample time is according to the property of element to be measured, experiment condition and repeatedly measures
Empirical value setting.All peak values addition acquired in sample time is taken and is obtained by the fluorescence intensity for calculating element A and B element
Fluorescence intensity of the value arrived as corresponding element, after testing, to be calculated element fluorescence intensity level directly proportional to constituent content,
By comparing the fluorescence intensity level of the standard sample detection of corresponding element, the content of the element in sample to be tested is obtained.
When multichannel atomic fluorescence detector is arranged three with upper channel, increase corresponding excitation light source 02, it is same to share one
Detector, fluorescence detection are as shown in Figure 5.
It is more using timeslice rotation work mode detection that the utility model multichannel atomic fluorescence detector is based on a detector
A element uses Special pulse current signal source for the performance for verifying front end circuit 03 below, generates 7 groups of different Ip amplitudes
Current signal, simulation PMT generate actual signal, by this front end circuit 03 and the obtained survey of signal processing circuit 04
Test result (referring to table 1), wherein signal source uses the pulse that the period is 20:1 for 4000uS, pulsewidth 200uS, duty ratio to drive
Dynamic signal, sample time are set as 12S.
1 test result of table
| 1st group | 2nd group | 3rd group | 4th group | 5th group | 6th group | 7th group | |
| Ip(pA) | 50 | 100 | 500 | 100 | 5000 | 10000 | 20000 |
| Measured value | 168 | 329 | 1606 | 3211 | 16063 | 32077 | 64107 |
The above test result it is found that simulation PMT detected signal value there are positive correlation, phase relations with actually detected value
Number close 1.000.
As shown in fig. 6, carrying out practical fluorescence detection, obtained sample to mercury element using the utility model atomic fluorescence detector
The matched curve of concentration and fluorescence intensity, related coefficient reach 0.9998.As it can be seen that the utility model multichannel atomic fluorescence detector
Front end circuit 03 is suitable for the detection of small-signal, and the utility model multichannel atomic fluorescence detector detection sensitivity is high, detection limit
It is low.
The utility model front end circuit uses resistance feedback type I-V conversion circuit 031, inverter cricuit 032 and amplifying circuit
033 combination forms two-stage amplifying circuit, and pA grades of current signal is converted to mV grades of voltage signal, it can be achieved that not increasing inspection
In survey device in the case where the negative high voltage of PMT, the detection sensitivity of detector is increased substantially；The utility model multichannel atom is glimmering
Light instrument detects while realizing multiple element using single detector timeslice rotation work mode, not only simplifies apparatus structure,
The interference between multiple sense channels is in turn avoided, to improve the reliability and accuracy of detection data.
It will be appreciated by those skilled in the art that these embodiments are merely to illustrate the utility model, without limitation, this is practical new
The range of type, the various equivalent variations and modification made to the utility model each fall within the appended claims for the utility model and are limited
In fixed range.
Claims (7)
1. a kind of front end circuit, for low current signal to be converted to significantly voltage signal, including I-V conversion circuit,
Inverter cricuit (032) and amplifying circuit, which is characterized in that the I-V conversion circuit is resistance feedback type I-V conversion circuit
(031), the output of I-V conversion circuit (031) is directly proportional to feedback resistance R4；Amplifying circuit is amplifier type amplifying circuit (033),
Its gain AfSize is directly proportional to the ratio of negative feedback resistor R3 and divider resistance R5, and the negative feedback resistor R3 of amplifying circuit is can
Resistance is adjusted, to adjust the gain of amplifying circuit (033).
2. front end circuit according to claim 1, which is characterized in that the I-V conversion circuit (031) and inverter cricuit
(032) partiting dc circuit that capacitor C2 and resistance R1 is formed is provided between.
3. front end circuit according to claim 1 or 2, which is characterized in that the amplifying circuit (033) is provided with offset
Adjustment circuit, to adjust the DC offset of output signal.
4. a kind of multichannel atomic fluorescence detector, the detection including multichannel excitation light source (02) and for capturing, detecting fluorescence signal
Device, the detector include photomultiplier tube (05), mainboard (01) and signal processing circuit (04), and mainboard is integrated with place on (01)
Manage device (011), D/A converter module (012), analog-to-digital conversion module (014) and interface module (013), which is characterized in that described
Detector further includes the described in any item front end circuits of claims 1 to 3 (03), and the output signal of front end circuit (03) is through signal
The processing of processing circuit (04) is converted to digital signal through analog-to-digital conversion module (014) and is sent to processor (011).
5. multichannel atomic fluorescence detector according to claim 4, which is characterized in that the signal processing circuit (04) includes
Filter circuit (041) and peak sample circuit (042), filter circuit (041) is low-pass filter, for front end circuit (03)
The signal of output is filtered and smoothly；Peak sample circuit (042) is for completing the sampling operation in scheduled sampling time.
6. multichannel atomic fluorescence detector according to claim 4 or 5, which is characterized in that front end circuit (03) is individually integrated
It on a front end circuit plate, and is connect with the output of photomultiplier tube (05), front end circuit plate and photomultiplier tube (05) seal
It is packaged together.
7. multichannel atomic fluorescence detector according to claim 4, which is characterized in that it further include a display touch screen (00),
Show that touch screen (00) passes through interface module (013) access processor (011).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201821791005.0U CN209416924U (en) | 2018-10-31 | 2018-10-31 | Front end circuit and multichannel atomic fluorescence detector including the front end circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201821791005.0U CN209416924U (en) | 2018-10-31 | 2018-10-31 | Front end circuit and multichannel atomic fluorescence detector including the front end circuit |
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| CN209416924U true CN209416924U (en) | 2019-09-20 |
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ID=67932958
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114146310A (en) * | 2021-12-08 | 2022-03-08 | 中科创辰(厦门)智慧科技有限公司 | Matrix type electric pulse time sequence isolation output circuit |
-
2018
- 2018-10-31 CN CN201821791005.0U patent/CN209416924U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114146310A (en) * | 2021-12-08 | 2022-03-08 | 中科创辰(厦门)智慧科技有限公司 | Matrix type electric pulse time sequence isolation output circuit |
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