CN104020346A - Micro-current signal extraction system - Google Patents
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Abstract
The invention relates to a micro-current signal extraction system. A signal is sampled by adopting a high-precision resistor, a current signal is transformed into a voltage signal; the voltage signal is transmitted to an analog signal preconditioning circuit, and sequentially passes through a primary amplification circuit, an analog filter circuit and a secondary amplification circuit to complete analog signal preconditioning; the signal which is subjected to analog signal preconditioning is output to a digital signal preconditioning circuit, and sequentially passes through an A/D (analog to digital) conversion circuit and a range switching and digital filter circuit; and a required micro-current signal is output after the digital signal conditioning is completed. According to the micro-current signal extraction system, the analog signal and digital signal conditionings are combined, a chopper-stabilizer integrated operational amplifier with high gain, high input impedance and high common mode rejection ratio is selected for preposed amplification of the system, 50Hz power line interference is inhibited by a dual-integral AD analog-to-digital conversion chip, and the I/O (input/output) interfaces can be greatly saved by virtue of 4-line serial communication, and high-efficiency and reliable data transmission can be realized. The micro-current signal extraction system can realize accurate measurement on micro-current, and can be used for insulation monitoring of electrical equipment.
Description
Technical field
The present invention relates to a kind of signal processing technology, particularly a kind of micro-current signal extraction system.
Background technology
Micro-current signal is extracted in has demand widely in electric system electrical equipment online monitoring.But in electric system, the running environment of electrical equipment is complicated, has various noise, mainly comprise that power line noise, electrical equipment noise, radio noise, machinery play source noise etc.Power line noise is mainly the noise that the spike that caused by power frequency electromagnetic field, high power switch break-make, voltage ripple of power network etc. produce; Electrical equipment noise mainly comprises the noise that power frequency electromagnetic field that equipment produces, corona discharge spark discharge, arc discharge etc. cause; Radio noise is mainly the interference that the meanss of communication such as the TV, radar, radio communication in life cause, and modulated electromagnetic wave is in the majority; Mechanical noise is mainly that mechanical vibration are converted to electrical noise, as piezoelectric effect noise, microphony noise etc.Therefore particularly important to current signal conditioning in micro-current signal extracts, only have signal is carried out to necessary suitable filtering processing, just can extract needed signal, the running status of correct judgment device.
At present, both at home and abroad the technical merit of the research and development of weak current acquisition system is reached its maturity, the maximum current resolution of external advanced potentiostat can reach 30fA, but it is expensive.Domestic product quality and technical indicator with compare one section of gap in addition abroad, need to be continued research.Be directed to above-mentioned situation, this patent has designed a kind of circuit that can realize tiny current measurement, thereby realizes the monitoring to insulation of electrical installation state.
Summary of the invention
The present invention be directed to weak current acquisition system precision and fall behind external problem, propose a kind of micro-current signal extraction system, realize the accurate measurement of micro-electric current.
Technical scheme of the present invention is: a kind of micro-current signal extraction system, comprise signals collecting, simulating signal preconditioned circuit and digital signal preconditioned circuit, adopt precision resister sampled signal, current signal is converted into voltage signal and send simulating signal preconditioned circuit, voltage signal is successively through amplifying circuit, analogue filter circuit and a secondary amplifying circuit, complete simulating signal preconditioned, analog filtering adopts five rank Butterworth low-pass filtering, by all filterings of the signal higher than 3HZ; Signal after simulating signal preconditioned is outputed to digital signal preconditioned circuit, pass through successively A/D change-over circuit, range conversion process and digital filter circuit, complete after digital signal is nursed one's health and be output as required micro-current signal.
The voltage signal of described signals collecting output by linear optical coupling isolate with transient state killer tube in parallel after output to simulating signal preconditioned circuit.
A described amplifying circuit is selected chopper-zero-stabilized integrated operational amplifier ICL7650; ICL7650 is connected into sign-changing amplifier; 10K sampling with high precision resistance two ends connect respectively ICL7650 input end; between two input ends and ground, connect respectively the protective circuit of diode of two positive-negative connecteds; ICL7650 operational amplifier input and output side shunt capacitance, suppresses the higher-order of oscillation.
Described analogue filter circuit is selected five rank Butterworth switching capacity filter, can adopt the MAX7410 wave filter of MAXIM company.
Described A/D change-over circuit is selected and can be suppressed the double integration A/D chip that 50HZ power frequency is disturbed, and can adopt the MAX132-18 position double integrator AD chip of Maxim.
Beneficial effect of the present invention is: the micro-current signal extraction system of the present invention, simulating signal and digital signal conditioning combine, the ICL7650 chopper-zero-stabilized integrated operational amplifier of high-gain, high input impedance, high cmrr is selected in the preposition amplification of system, 18 double integrator AD modulus conversion chips, having suppressed the power frequency of 50Hz disturbs, I/O interface has been saved in the serial communication of MAX132 simultaneously greatly, efficient, reliable data transmission.The accurate measurement of realization to micro-electric current, can be used for the insulating monitoring of electrical equipment, as the Leakage Current of high-voltage cable insulating, sheath, measures, and has obtained good effect.
Accompanying drawing explanation
Fig. 1 is the micro-current signal extraction system of the present invention block diagram;
Fig. 2 is the micro-current signal extraction system sampling of the present invention and amplification circuit diagram;
Fig. 3 is the micro-current signal extraction system five rank Butterworth analogue filter circuit figure of the present invention;
Fig. 4 is 18 A/D convertor circuit figure of the micro-current signal extraction system of the present invention;
Fig. 5 is the micro-current signal extraction system of the present invention general flow chart.
Embodiment
Native system is by measured signal constituent analysis, and micro-current signal extraction module adopts precision resister sampled signal, current signal is converted into voltage signal and is convenient to extract.To the signal after conversion once amplify, analog filtering and secondary amplify, complete simulating signal preconditioned, in view of containing many noise signals in signal, adopt 5 rank Butterworth low-pass filtering, by all filterings of the signal higher than 3HZ, native system selects MAX7410 chip can well realize its function.Filtered signal is carried out after secondary amplifies exporting the conversion through A/D, simulating signal is converted into digital signal, be convenient to data processing below, native system adopts MAX132 chip, can realize 18 high-precision A/D conversion, can suppress the power frequency of 50HZ simultaneously and disturb, through overrange, process and MCU digital signal processing again, be mainly digital filtering, the data-signal that obtains wanting, completes digital signal conditioning.Finally by LCD12864, signal is shown, as shown in Figure 1 system chart.Excessive in order to prevent input signal; cause the infringement to follow-up metering circuit; input signal is protected and isolated; first it allow signal by transient state killer tube in parallel; when signal surpasses its threshold values; voltage remains on the magnitude of voltage of transient state killer tube, thereby guarantees that input voltage is no more than the maximal value that follow-up metering circuit can bear.Improper in order to prevent owing to measuring, cause sampling resistor to puncture, cause earth potential to be raised, cause the damage of metering circuit, adopt linear optical coupling to isolate.
Sampling and amplification circuit diagram: ICL7650 are chopper-zero-stabilized integrated operational amplifiers as shown in Figure 2, and it has the features such as Low-offset voltage and ultralow drift, high-gain, high input impedance, high cmrr, and performance is very superior stable.In the circuit of measuring feeble signal, be commonly used for prime amplifier.In Fig. 2, ICL7650 is connected into sign-changing amplifier.R8 is 10K sampling with high precision resistance, and the current conversion flowing through is become to voltage Vin; Then voltage signal is added on two input ends of ICL7650, feeble signal 10 pin from chip after amplifying are exported.In order to protect ICL7650 to burn out too greatly because of the amplitude of input signal, at the input end of signal, connect 4 diodes and carry out holding circuit.The capacitor C 1 that is added in ICL7650 operational amplifier input and output side is in order to prevent that circuit from producing the higher-order of oscillation, because its capacity is very little, also very little on the enlargement factor impact of signal.
Five rank Butterworth analogue filter circuit figure as shown in Figure 3, adopt the MAX7410 wave filter of MAXIM company, and this is a five rank Butterworths, switching capacity filter (SCFS).Circuit is used 5V power supply, has low-power consumption, the low-pass filter that bandwidth is 15KHZ.The cutoff frequency of circuit determines (seeing formula 2) by the clock signal frequency of circuit.The clock signal of circuit can have two kinds of modes to provide, a kind of is directly at the external electric capacity of 8 pin, realize concussion clocking with chip internal, its clock frequency depends on the size (seeing formula 1) of external capacitor, another kind is directly from 8 pin inputs by external clock, this mode can change the frequency of external timing signal at any time, thereby changes easily the cutoff frequency of filtering circuit.According to the requirement of signal, choose C
oSCfor 0.1uF(refers to C11 in figure here), now cutoff frequency is 3Hz.
(formula 1)
(formula 2)
The effect of A/D converter is that the simulating signal of input is converted to digital form, makes CPU can process the simulating signal receiving from circuit-under-test.18 A/D convertor circuit figure as shown in Figure 4, the MAX132-18 position double integrator AD chip of the selection Maxim of the A/D conversion chip of native system, this chip has very high conversion accuracy, and can suppress 50HZ power frequency and disturb.And there is following several advantage:
(1) the high change-over period of measuring accuracy is short: the inner multiple slope integration mode that adopts of MAX132, provide than fast many high resolution conversion standard A D switching time, and conversion times is greater than 100 times/s.At full scale, be
in the situation of 512mV, input signal resolution 2
v/LSB.
(2) low in energy consumption: MAX132 adopts CMOs circuit, guarantees that its exemplary operation electric current only has 60uA; And when park mode, even only need the electric current of 1uA, can be in follow-up work state.
(3) adopt 4 line serial line interface: MAX132 to adopt distinguished 4 line interface mode processed, only need sheet choosing (CS), clock (SCLK), data inputs (DIN), data output (DOUT) four lines can realize easily and the I/O interface of any general purpose microprocessor, and guarantee at Millisecond the time of whole communication process.
(4) 4 program control parallel output: MAX132 also have 4 digital spcs that can be arranged by serial order and export, and can be used for the gain of control inputs signal or carry out the setting of working environment, even can be directly used in expansion parallel interface.
MAX872 is the 2.5V voltage chip of accurate micro-power consumption, for AD chip provides the high progress reference voltage of 2.5V, has ultralow quiescent current and 200mV low voltage difference.
System main-process stream design: after system powers on, first whole system is carried out to initialization, initialize routine comprises carries out the setting of initialization, zero clearing and some port attributes to various parameters, each chip.Then carry out range judgement, then call A/D conversion routine and carry out data acquisition, input signal is carried out to A/D analog to digital conversion.After EOC, in order to improve the signal accuracy of measurement, system is carried out the processing of running mean value filtering for 10 times to input voltage continuous acquisition, and its result is as corresponding magnitude of voltage.Carry out numerical value conversion again, the value obtaining is converted to the amount of required demonstration, call the display subroutine of LCD12864, the interface of display panel, finally can calling communication subroutine realize serial communication.System general flow chart is as shown in Figure 5:
The feature of feeble signal set forth in article, contains complicated various noises, and for filter out noise signal, system adopts the method for analog filtering and digital filtering combination.The ICL7650 chopper-zero-stabilized integrated operational amplifier of high-gain, high input impedance, high cmrr is selected in the preposition amplification of system, 18 double integrator AD modulus conversion chips, having suppressed the power frequency of 50Hz disturbs, I/O interface has been saved in the serial communication of MAX132 simultaneously greatly, efficient, reliable data transmission.According to the little current signal extraction system of exploitation herein, can realize the accurate measurement to micro-electric current, can be used for the insulating monitoring of electrical equipment, as the Leakage Current of high-voltage cable insulating, sheath is measured, and obtain good effect.
Claims (5)
1. a micro-current signal extraction system, it is characterized in that, comprise signals collecting, simulating signal preconditioned circuit and digital signal preconditioned circuit, adopt precision resister sampled signal, current signal is converted into voltage signal and send simulating signal preconditioned circuit, voltage signal through amplifying circuit, analogue filter circuit and a secondary amplifying circuit, completes simulating signal preconditioned successively, analog filtering adopts five rank Butterworth low-pass filtering, by all filterings of the signal higher than 3HZ; Signal after simulating signal preconditioned is outputed to digital signal preconditioned circuit, pass through successively A/D change-over circuit, range conversion process and digital filter circuit, complete after digital signal is nursed one's health and be output as required micro-current signal.
2. micro-current signal extraction system according to claim 1, is characterized in that, the voltage signal of described signals collecting output by linear optical coupling isolate with transient state killer tube in parallel after output to simulating signal preconditioned circuit.
3. micro-current signal extraction system according to claim 2; it is characterized in that; a described amplifying circuit is selected chopper-zero-stabilized integrated operational amplifier ICL7650; ICL7650 is connected into sign-changing amplifier; 10K sampling with high precision resistance two ends connect respectively ICL7650 input end; between two input ends and ground, connect respectively the protective circuit of diode of two positive-negative connecteds, ICL7650 operational amplifier input and output side shunt capacitance, suppresses the higher-order of oscillation.
4. micro-current signal extraction system according to claim 2, is characterized in that, described analogue filter circuit is selected five rank Butterworth switching capacity filter, can adopt the MAX7410 wave filter of MAXIM company.
5. micro-current signal extraction system according to claim 2, is characterized in that, described A/D change-over circuit is selected and can be suppressed the double integration A/D chip that 50HZ power frequency is disturbed, and can adopt the MAX132-18 position double integrator AD chip of Maxim.
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Cited By (14)
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| CN104991115A (en) * | 2015-06-12 | 2015-10-21 | 武汉精测电子技术股份有限公司 | Chopper-type direct current detection method and circuit |
| CN105259402A (en) * | 2015-10-27 | 2016-01-20 | 昆山洺九机电有限公司 | USB interface current and voltage test device |
| CN105914836A (en) * | 2016-05-24 | 2016-08-31 | 北京工业大学 | Charging-type portable pA micro current monitoring system |
| CN105954805A (en) * | 2016-06-02 | 2016-09-21 | 桂林电子科技大学 | Self-adaption data acquisition system for mining ultrahigh density electrical method instrument |
| CN108418565A (en) * | 2018-01-26 | 2018-08-17 | 芯海科技（深圳）股份有限公司 | A kind of extracting method of PIR useful signals |
| CN109116092A (en) * | 2018-08-10 | 2019-01-01 | 王泉 | A kind of digitlization current sensor module |
| CN109342805A (en) * | 2018-11-21 | 2019-02-15 | 陕西电器研究所 | A kind of high-precision micro-ampere current detection circuit |
| CN109633252A (en) * | 2018-12-05 | 2019-04-16 | 西安航天精密机电研究所 | The method and circuit of big small-range segmented A/D acquisition accelerometer current signal |
| CN110568252A (en) * | 2019-08-29 | 2019-12-13 | 桂林电子科技大学 | four-channel double-gear interface control circuit current detection system |
| CN111323828A (en) * | 2020-04-02 | 2020-06-23 | 中国海洋大学 | Program-controlled gain type ocean electric field signal acquisition method, system, device and application |
| CN111551797A (en) * | 2020-04-17 | 2020-08-18 | 中国兵器工业火***工程与安全技术研究院 | Online electrostatic charge quantity measuring device suitable for energetic material |
| CN111751611A (en) * | 2020-07-20 | 2020-10-09 | 北京卫星环境工程研究所 | Weak current measuring system |
| 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 |
| CN114401005A (en) * | 2022-03-25 | 2022-04-26 | 湖南恩智测控技术有限公司 | Power frequency interference elimination method and device |
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Cited By (19)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104991115B (en) * | 2015-06-12 | 2017-12-15 | 武汉精测电子技术股份有限公司 | A kind of chopped mode direct current detection method and circuit |
| CN104991115A (en) * | 2015-06-12 | 2015-10-21 | 武汉精测电子技术股份有限公司 | Chopper-type direct current detection method and circuit |
| CN105259402A (en) * | 2015-10-27 | 2016-01-20 | 昆山洺九机电有限公司 | USB interface current and voltage test device |
| CN105914836B (en) * | 2016-05-24 | 2019-03-22 | 北京工业大学 | Chargeable portable pA micro-current monitors system |
| CN105914836A (en) * | 2016-05-24 | 2016-08-31 | 北京工业大学 | Charging-type portable pA micro current monitoring system |
| CN105954805A (en) * | 2016-06-02 | 2016-09-21 | 桂林电子科技大学 | Self-adaption data acquisition system for mining ultrahigh density electrical method instrument |
| CN105954805B (en) * | 2016-06-02 | 2018-03-09 | 桂林电子科技大学 | A kind of mining VHD electrical prospecting apparatus self-adapting data acquisition system |
| CN108418565A (en) * | 2018-01-26 | 2018-08-17 | 芯海科技（深圳）股份有限公司 | A kind of extracting method of PIR useful signals |
| CN109116092A (en) * | 2018-08-10 | 2019-01-01 | 王泉 | A kind of digitlization current sensor module |
| CN109342805A (en) * | 2018-11-21 | 2019-02-15 | 陕西电器研究所 | A kind of high-precision micro-ampere current detection circuit |
| CN109342805B (en) * | 2018-11-21 | 2020-12-22 | 陕西电器研究所 | High-precision microampere current detection circuit |
| CN109633252A (en) * | 2018-12-05 | 2019-04-16 | 西安航天精密机电研究所 | The method and circuit of big small-range segmented A/D acquisition accelerometer current signal |
| CN110568252A (en) * | 2019-08-29 | 2019-12-13 | 桂林电子科技大学 | four-channel double-gear interface control circuit current detection system |
| CN111323828A (en) * | 2020-04-02 | 2020-06-23 | 中国海洋大学 | Program-controlled gain type ocean electric field signal acquisition method, system, device and application |
| CN111551797A (en) * | 2020-04-17 | 2020-08-18 | 中国兵器工业火***工程与安全技术研究院 | Online electrostatic charge quantity measuring device suitable for energetic material |
| CN111751611A (en) * | 2020-07-20 | 2020-10-09 | 北京卫星环境工程研究所 | Weak current measuring system |
| CN111751611B (en) * | 2020-07-20 | 2023-04-21 | 北京卫星环境工程研究所 | Weak current measurement system |
| 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 |
| CN114401005A (en) * | 2022-03-25 | 2022-04-26 | 湖南恩智测控技术有限公司 | Power frequency interference elimination method and device |
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Application publication date: 20140903 |