CN204425298U - A kind of faint AC signal amplitude lock-in amplifier - Google Patents

A kind of faint AC signal amplitude lock-in amplifier Download PDF

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Publication number
CN204425298U
CN204425298U CN201520154740.0U CN201520154740U CN204425298U CN 204425298 U CN204425298 U CN 204425298U CN 201520154740 U CN201520154740 U CN 201520154740U CN 204425298 U CN204425298 U CN 204425298U
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China
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circuit module
signal
amplifier
faint
module
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Expired - Fee Related
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CN201520154740.0U
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Chinese (zh)
Inventor
张伟玉
束健伟
董晋峰
刘华
高平
周杰
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Tianjin Agricultural University
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Tianjin Agricultural University
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Abstract

The utility model discloses a kind of faint AC signal amplitude lock-in amplifier, comprise: the faint AC signal modulation circuit module, phase shift block, comparator module and the inverter modules that are electrically connected successively, lock-in amplifier also comprises: phase sensitive detection module, low-pass filter circuit module, direct current amplification module and microprocessor controls circuit module; The square wave that phase sensitive detection module utilizes reference channel to export carries out rectification to the same frequency sinusoidal signal that described faint AC signal modulation circuit module modulates and exports all-view signal; Described all-view signal, by described low-pass filter circuit module and described direct current amplification module, carries out output display through described microprocessor controls circuit module.The utility model can will be submerged in the known effective faint alternating current signal detection of very noisy medium frequency out, and export amplitude and the amplitude effective value of effective faint AC signal, solve small-signal lock-in amplifier acquisition precision not, the shortcoming such as the testing requirement that can only meet under particular case.

Description

A kind of faint AC signal amplitude lock-in amplifier
Technical field
The utility model relates to lock-in amplifier field, particularly relates to a kind of faint AC signal amplitude lock-in amplifier.
Background technology
Detection of Weak Signals is the measurement to being submerged in small-signal in background noise.This kind of signal has to pass through amplification, and due to the impact of the fluctuation of small-signal itself, background and amplifier noise, measurement sensistivity is restricted.Need the preamplifier that noise factor is as far as possible little, and design optimum Match according to source impedance and operating frequency; Need development to be applicable to faint Cleaning Principle and the device of special requirement can be met; Utilize electronics and information-theoretical method, the origin cause of formation of research noise and rule, the feature of analytic signal and coherent relationships.Since nineteen twenty-eight finds that the thermal agitation of electronics in resistance causes non-periodic voltage, weak detection technique is subject to most attention and is developed rapidly.
Existing small-signal lock-in amplifier still also exist acquisition precision not, can not determine the quality of institute's detection signal, the shortcoming such as testing requirement under system can only meet particular case.
Utility model content
The utility model provides a kind of faint AC signal amplitude lock-in amplifier, solve small-signal lock-in amplifier acquisition precision not, can not determine institute's detection signal quality, can only meet particular case under the shortcoming such as testing requirement, described below:
A kind of faint AC signal amplitude lock-in amplifier, comprise: the faint AC signal modulation circuit module, phase shift block, comparator module and the inverter modules that are electrically connected successively, described lock-in amplifier also comprises: phase sensitive detection module, low-pass filter circuit module, direct current amplification module and microprocessor controls circuit module;
The square wave that phase sensitive detection module utilizes reference channel to export carries out rectification to the same frequency sinusoidal signal that described faint AC signal modulation circuit module modulates and exports all-view signal;
Described all-view signal, by described low-pass filter circuit module and described direct current amplification module, carries out output display through described microprocessor controls circuit module.
Wherein, the phase shift range of described phase shift block is: the cascade of two panels operational amplifier forms 0 ~ 360 °.Described phase sensitive detection module is made up of multi-channel electronic switch group and an adder.
Wherein, described low-pass filter circuit module is the second order passive low ventilating filter of resistance, electric capacity structure.Described direct current amplification module is made up of operational amplifier, potentiometer and protective resistance.
Further, described microprocessor controls circuit module comprises: microcontroller, display circuit module, key circuit module, DDS signal generator and AD Acquisition Circuit module;
Described faint AC signal modulation circuit module comprises: ac amplifier circuit module and bandwidth-limited circuit module;
Described microcontroller controls described display circuit module, described key circuit module, described DDS signal generator, described AD Acquisition Circuit module and described bandwidth-limited circuit module respectively;
The 3dB frequency band range of described key circuit module input measured signal frequency and signalling channel, described microcontroller regulates the parameter of described bandwidth-limited circuit module automatically by the measured signal of input.
Further, the model of described DDS signal generator is AD9850; Described AD Acquisition Circuit module is made up of AD conversion chip.Described bandwidth-limited circuit module is built by filtering chip and digital regulation resistance and is formed.
The beneficial effect of the technical scheme that the utility model provides is: the utility model amplifies process by echo signal being carried out interchange, carry out bandpass filtering again, filtering interference signals, obtain AC signal, the reference signal of same frequency obtains the square-wave signal identical with phase of ac signal through phase shift block and comparator module simultaneously, pure all-view signal is obtained after phase sensitive detection module, then process is amplified through low-pass filtering and direct current, carry out gathering and sending into display circuit module finally by AD Acquisition Circuit module, complete the detection of small-signal.The utility model can will be submerged in the known effective faint alternating current signal detection of very noisy medium frequency out, and export amplitude and the amplitude effective value of effective faint AC signal, solve small-signal lock-in amplifier acquisition precision not, can not determine the shortcomings such as the quality of institute's detection signal, the testing requirement that can only meet under particular case.
Accompanying drawing explanation
Fig. 1 is a kind of structural representation of faint AC signal amplitude lock-in amplifier;
Fig. 2 is a kind of operation principle schematic diagram of faint AC signal amplitude lock-in amplifier;
Fig. 3 is a kind of ac amplifier circuit module principle figure of faint AC signal amplitude lock-in amplifier;
Fig. 4 is a kind of bandpass filtering modules block schematic diagram of faint AC signal amplitude lock-in amplifier;
Fig. 5 is a kind of phase sensitive detection module principle figure of faint AC signal amplitude lock-in amplifier;
Fig. 6 is a kind of low-pass filter circuit module principle figure of faint AC signal amplitude lock-in amplifier;
Fig. 7 is a kind of direct current amplification module schematic diagram of faint AC signal amplitude lock-in amplifier;
Fig. 8 is a kind of phase shift block schematic diagram of faint AC signal amplitude lock-in amplifier.
In accompanying drawing, the list of parts representated by each label is as follows:
1: faint AC signal modulation circuit module; 2: phase shift block;
3: comparator module; 4: inverter modules;
5: phase sensitive detection module; 6: low-pass filter circuit module;
7: direct current amplification module; 8: microprocessor controls circuit module;
11: ac amplifier circuit module; 12: bandwidth-limited circuit module;
31: the first comparators; 32: the second comparators;
41: the first inverters; 42: the second inverters;
81: microcontroller; 82: display circuit module;
83: key circuit module; 84:DDS signal generator;
85:AD Acquisition Circuit module.
Embodiment
For making the purpose of this utility model, technical scheme and advantage clearly, below the utility model execution mode is described in further detail.
The utility model provides a kind of faint AC signal amplitude lock-in amplifier, see Fig. 1, this lock-in amplifier comprises: faint AC signal modulation circuit module 1, phase shift block 2, comparator module 3, inverter modules 4, phase sensitive detection module 5, low-pass filter circuit module 6, direct current amplification module 7, microprocessor controls circuit module 8.
During specific implementation, faint AC signal modulation circuit module 1 comprises: ac amplifier circuit module 11, bandwidth-limited circuit module 12.
Microprocessor controls circuit module 8 comprises: microcontroller 81, display circuit module 82, key circuit module 83, DDS signal generator 84 and AD Acquisition Circuit module 85.Microprocessor controls circuit module 8 adopts circuits mask, and isolation interference, can monitor supply voltage; Microcontroller 81 controls display circuit module 82, key circuit module 83, DDS signal generator 84 and AD Acquisition Circuit module 85 and bandwidth-limited circuit module 12 respectively.
The square wave that phase sensitive detection module 5 utilizes reference channel to export carries out rectification to the same frequency sinusoidal signal (sensitive signal) that faint AC signal modulation circuit module 1 modulates and exports all-view signal, by low-pass filter circuit module 6 and direct current amplification module 7, after the AD conversion of AD Acquisition Circuit module 85, deliver to display circuit module 82 by microcontroller 81 show.
When measured signal frequency is known, inputted the 3dB frequency band range of measured signal frequency and signalling channel by key circuit module 84, microcontroller 81 is by measured signal parameter automatic accommodation zone bandpass filter circuit module 12 parameter of input.
The waveform phase that square wave phase and the phase shift block 2 of square wave driver output export is without the need to strictly identical; Phase sensitive detection module 5 outputs signal the all-view signal for faint AC signal.
Wherein, phase shift block 2 forms phase shift range 0 ~ 360 ° by the cascade of two panels operational amplifier.Program control module 2 will be inputted by operational amplifier, output signal isolation; The waveform phase that phase shift block 2 exports is that linear stepping is adjustable.The multiplication factor of phase shift block 2 is approximately 1, and its phase shift angle regulates digital regulation resistance to realize controlling by level controller.
Comparator module 3 comprises: two comparison circuits be made up of high speed amplifier, is respectively the first comparator 31 and the second comparator 32.The zero-crossing comparator that first comparator 31 and the second comparator 32 are made up of operational amplifier respectively, signal enters the inverting input of operational amplifier by coupling capacitance, and output voltage is determined by chip power supply voltage.
Reverser module 4 comprises: two negater circuits be made up of high speed amplifier, is respectively the first inverter 41 and the second inverter 42.The inverter that first inverter 41 and the second inverter 42 are made up of operational amplifier respectively, signal enters the inverting input of operational amplifier by coupling capacitance, in the same way input end grounding.
Phase sensitive detection module 5 is made up of multi-channel electronic switch group and an adder, AC signal with oppositely after signal respectively as 2 two-way input signals of electronic switch, the square wave of the phase 180 ° exported by 2 zero-crossing comparators is as the control signal of electronic switch.The output signal of electronic switch is added through adder 1:1 again, the all-view signal corresponding to output AC signal.
The second order passive low ventilating filter that low-pass filter circuit module 6 is resistance, electric capacity builds.
Wherein, direct current amplification module 7 is made up of operational amplifier, potentiometer and protective resistance.Signal is inputted by the positive input of operational amplifier, and cross-over connection potentiometer between output and reverse input end, reverse input end is by grounding through resistance.
During specific implementation, AD Acquisition Circuit module 85 is made up of AD conversion chip, and the negative analog input end grounding of AD conversion chip, positive analog input end connects input signal.DDS signal generator 84 adopts AD9850, the analog sine that AD9850 just can produce a frequency and phase place PLC technology after connecting precision interval clock source and write frequency phase control words exports, and this sine wave directly can be used as frequency signal source or be converted to square wave through the high-speed comparator of inside to export.Under the clock of 125MHz, the frequency control word of 35 can make the output frequency resolution rate of AD9850 reach 0.0291Hz; And there are 5 phase control positions, and allow phase place press increment 180,45,90,22.5,11.25 or these values be combined into Row sum-equal matrix.The sinusoidal signal identical with signal will be extracted is generated, for detection after the process such as phase shift by signal generating module.The AD Acquisition Circuit module 85 of this lock-in amplifier, is made up of AD conversion chip and feedback loop, and AD conversion chip directly gathers the voltage that programmed direct current amplifier module 7 exports, and microcontroller 81 reads the magnitude of voltage that A/D chip collects.The negative analog input end grounding of AD conversion chip, analog input termination inputs direct current signal to be measured.The direct voltage that AD Acquisition Circuit module 85 generates for gathering low pass filter.Display circuit module 82 is sent to after AD sampling.
The multiplication factor of ac amplifier circuit module 11 within the specific limits can stepping linear regulation.The mode of operation centre frequency f of bandwidth-limited circuit module 12 and gain are adjustable.In ac amplifier circuit module 11, digital potentiometer is connected across two Rg ends of instrument and meter operational amplifier, and the reference voltage terminal of instrument and meter operational amplifier, positive input all directly ground connection, as signal output part after output serial connection ceramic condenser.Digital potentiometer carry controls the tissue of its resistance at microcontroller 81 and then controls the multiplication factor of ac amplifier circuit module.
Wherein, bandwidth-limited circuit module 12 is built by filtering chip and digital regulation resistance and is formed, and multiple filtering chip cascaded-output signal can be selected as required to deliver to the input of phase sensitive detection module 5.
The operation principle of this lock-in amplifier is described in detail below in conjunction with Fig. 2-Fig. 8, described below:
See Fig. 2, input signal is echo signal S (t) and reference signal R (t), echo signal S (t) first carries out amplification process through ac amplifier circuit module 11 pairs of signals, then bandpass filtering is carried out by bandwidth-limited circuit module 12, filtering interference signals, obtain AC signal x1 (t), signal x1 (t) is divided into two-way one tunnel directly to first via electronic switch as input signal, and another road obtains sinusoidal signal x2 (t) to No. second electronic switch as input signal through reverser.The reference signal R (t) of the same frequency of DDS signal generator 84 generation simultaneously, through phase shift block 2, makes reference signal R (t) identical with the signal phase that will extract.Square-wave signal r1 (t) identical with x (t) phase place is obtained again through the first comparator 31, signal r1 (t) is divided into two-way one tunnel directly to first via electronic switch as control signal, and another road obtains square-wave signal r2 (t) through reverser and does control signal to another No. second electronic switch.AC signal x1 (t), x2 (t) and square-wave signal r1 (t), r2 (t) obtain pure all-view signal after phase sensitive detection module 5, then obtain direct current signal q (t) after low-pass filter circuit module 6.After deliver to display circuit module 82 through the AD conversion of direct current amplification module, AD Acquisition Circuit module 85 by microcontroller 81 and show.
See Fig. 3, ac amplifier circuit module 11 operational amplifier used is instrument and meter operational amplifier INA128 family chip, and also can calculate by common amplifier the high-amplification-factor amplifier network that amplifier stage joint group becomes, its multiplication factor is up to 10000 times.Multiplication factor determines by being connected across the resistance that Rg holds, and holds cross-over connection one potentiometer at Rg, for the multiplication factor of control amplifier as R4 in figure, regulates the size of R4 can change the multiplication factor of amplifier.
See Fig. 4, the core parts of bandwidth-limited circuit module 12 are OPA227P universal amplifier and digital regulation resistance x9318, form quadravalence active filter.Digital regulation resistance R2 and R3 will change centre frequency and the gain of band pass filter.
See Fig. 5, phase sensitive detection module 5 is made up of components and parts such as operational amplifier, resistance and electronic switches.
See Fig. 6, low-pass filter circuit module 6 forms the low pass filter of resistance-capacitance coupling by two electrochemical capacitors and resistance.Its input is all-wave, and output is a DC quantity.Its advantage is that circuit structure is simple, and reliable working performance is stablized.
See Fig. 7, DC amplification circuit module 7 is made up of a general-purpose operation amplifier OPA227P.Multiplication factor is by regulator potentiometer R4.
See Fig. 8, phase shift block 2 will be inputted by OPA series operational amplifier, be outputed signal isolation, and phase shift angle is controlled by the digital regulation resistance of carry on data/address bus and control bus.
The utility model embodiment is to the model of each device except doing specified otherwise, and the model of other devices does not limit, as long as can complete the device of above-mentioned functions.
It will be appreciated by those skilled in the art that accompanying drawing is the schematic diagram of a preferred embodiment, above-mentioned the utility model embodiment sequence number, just to describing, does not represent the quality of embodiment.The foregoing is only preferred embodiment of the present utility model, not in order to limit the utility model, all within spirit of the present utility model and principle, any amendment done, equivalent replacement, improvement etc., all should be included within protection range of the present utility model.

Claims (8)

1. a faint AC signal amplitude lock-in amplifier, comprise: the faint AC signal modulation circuit module, phase shift block, comparator module and the inverter modules that are electrically connected successively, it is characterized in that, described lock-in amplifier also comprises: phase sensitive detection module, low-pass filter circuit module, direct current amplification module and microprocessor controls circuit module;
The square wave that phase sensitive detection module utilizes reference channel to export carries out rectification to the same frequency sinusoidal signal that described faint AC signal modulation circuit module modulates and exports all-view signal;
Described all-view signal, by described low-pass filter circuit module and described direct current amplification module, carries out output display through described microprocessor controls circuit module.
2. one according to claim 1 faint AC signal amplitude lock-in amplifier, is characterized in that, the phase shift range of described phase shift block is: the cascade of two panels operational amplifier forms 0 ~ 360 °.
3. one according to claim 1 faint AC signal amplitude lock-in amplifier, is characterized in that, described phase sensitive detection module is made up of multi-channel electronic switch group and an adder.
4. one according to claim 1 faint AC signal amplitude lock-in amplifier, is characterized in that, the second order passive low ventilating filter that described low-pass filter circuit module is resistance, electric capacity builds.
5. one according to claim 1 faint AC signal amplitude lock-in amplifier, is characterized in that, described direct current amplification module is made up of operational amplifier, potentiometer and protective resistance.
6. one according to claim 1 faint AC signal amplitude lock-in amplifier, is characterized in that,
Described microprocessor controls circuit module comprises: microcontroller, display circuit module, key circuit module, DDS signal generator and AD Acquisition Circuit module;
Described faint AC signal modulation circuit module comprises: ac amplifier circuit module and bandwidth-limited circuit module;
Described microcontroller controls described display circuit module, described key circuit module, described DDS signal generator, described AD Acquisition Circuit module and described bandwidth-limited circuit module respectively;
The 3dB frequency band range of described key circuit module input measured signal frequency and signalling channel, described microcontroller regulates the parameter of described bandwidth-limited circuit module automatically by the measured signal of input.
7. one according to claim 6 faint AC signal amplitude lock-in amplifier, is characterized in that,
The model of described DDS signal generator is AD9850; Described AD Acquisition Circuit module is made up of AD conversion chip.
8. one according to claim 6 faint AC signal amplitude lock-in amplifier, is characterized in that, described bandwidth-limited circuit module is built by filtering chip and digital regulation resistance and formed.
CN201520154740.0U 2015-03-18 2015-03-18 A kind of faint AC signal amplitude lock-in amplifier Expired - Fee Related CN204425298U (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105425025A (en) * 2015-11-23 2016-03-23 浙江工业职业技术学院 High-precision multi-range weak current detection system
CN108288956A (en) * 2017-12-29 2018-07-17 河南北瑞电子科技有限公司 A kind of digital Lock-in Amplifier based on DSP
CN108693486A (en) * 2018-03-30 2018-10-23 华中科技大学 A kind of faint low frequency magnetic signal detection method and system based on AMR sensor
CN109085464A (en) * 2018-09-29 2018-12-25 广东电网有限责任公司 A kind of power grid weak signal extraction based on line terminal recording
CN112213538A (en) * 2020-09-22 2021-01-12 杭州电子科技大学 Phase self-adaptive adjusting lock-in amplifier based on magnetic control phase shifting

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105425025A (en) * 2015-11-23 2016-03-23 浙江工业职业技术学院 High-precision multi-range weak current detection system
CN105425025B (en) * 2015-11-23 2017-12-22 浙江工业职业技术学院 A kind of high-precision multrirange weak current system
CN108288956A (en) * 2017-12-29 2018-07-17 河南北瑞电子科技有限公司 A kind of digital Lock-in Amplifier based on DSP
CN108693486A (en) * 2018-03-30 2018-10-23 华中科技大学 A kind of faint low frequency magnetic signal detection method and system based on AMR sensor
CN109085464A (en) * 2018-09-29 2018-12-25 广东电网有限责任公司 A kind of power grid weak signal extraction based on line terminal recording
CN109085464B (en) * 2018-09-29 2020-05-29 广东电网有限责任公司 Power grid weak signal extraction method based on line terminal wave recording
CN112213538A (en) * 2020-09-22 2021-01-12 杭州电子科技大学 Phase self-adaptive adjusting lock-in amplifier based on magnetic control phase shifting
CN112213538B (en) * 2020-09-22 2022-04-22 杭州电子科技大学 Phase self-adaptive adjusting lock-in amplifier based on magnetic control phase shifting

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CF01 Termination of patent right due to non-payment of annual fee

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