CN101738537B - High-sensitivity digital nanovoltmeter and realization method thereof - Google Patents

High-sensitivity digital nanovoltmeter and realization method thereof Download PDF

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CN101738537B
CN101738537B CN 200910243512 CN200910243512A CN101738537B CN 101738537 B CN101738537 B CN 101738537B CN 200910243512 CN200910243512 CN 200910243512 CN 200910243512 A CN200910243512 A CN 200910243512A CN 101738537 B CN101738537 B CN 101738537B
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voltage
circuit
cpu circuit
converter
conversion
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CN101738537A (en
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王斌
冯文武
潘攀
严明
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No514 Inst No5 Academy Chinese Space Science-Technology Group
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No514 Inst No5 Academy Chinese Space Science-Technology Group
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Abstract

The invention relates to a high-sensitivity digital nanovoltmeter and a realization method thereof. A conversion galvanometer for converting current into deflection laser and a feedback resistance network for voltage division are arranged on a measuring loop; a CCD circuit receives light-spot images of the conversion galvanometer, then the light-spot images are inputted to a CPU circuit to be processed, and the CPU circuit obtains the positions of light dots through filtering and calculation; the CPU circuit simultaneously controls a D/A converter to output a direct-current voltage; when the direct-current voltage passes through a voltage of the feedback resistance network after voltage division to offset a measured voltage, a current in the measuring loop is zero, the light spots in the light-spot images outputted by the CCD circuit are positioned at original points, and the CPU circuit outputs the direct-current voltage outputted by the D/A converter as a detected voltage to be measured; because the measuring loop, a feedback circuit and a detection circuit are completely-independent electric systems, and the circuits are only connected by optical signals, the high-sensitivity digital nanovoltmeter has the strong common-mode interference resistant capability and can be used as a high-sensitivity zero-pointing instrument to be applied to high-accuracy measuring equipment such as potential difference meters and electrical bridges.

Description

A kind of high-sensitivity digital nanovoltmeter and its implementation
Technical field
The present invention relates to a kind of low pressure inspection stream device, particularly relate to a kind of high-sensitivity digital nanovoltmeter and its implementation that can be used for DC low-voltage measurement and voltage nulling.
Background technology
The monitoring of weak current and detection technique are widely used in feeble signal precision measurement, bioelectric current detection, semiconductor and the chemical analysis field.At present, be used for the instrument that the high precision DC low-voltage measures with the voltage nulling and mainly contain permanent magnet moving coil galvanometer, photoelectricity amplification galvanometer and digital nanovoltmeter etc.Wherein, Permanent magnet moving coil galvanometer and photoelectricity amplify galvanometer and all adopt luminous point to show; Owing to receive the earth vibrations, near the Brownian movement of the air molecule of the moving frame of galvanometer and the factor affecting such as thermal noise voltage in moving frame loop, all there are the reading difficulty in permanent magnet moving coil galvanometer and photoelectricity amplification galvanometer, sensitivity is restricted and problems such as measuring error is big.But, therefore has the advantage of stronger anti-common mode interference ability because galvanometer inside has the structure that the size of current that flows through suspension is converted into torque.
Digital nanovoltmeter normally is made up of electronic amplifier and analog to digital converter, has the high advantage of resolving power, can reach the resolving power of 1nV.But the electronic amplifier of digital nanovoltmeter adopts modulation-demodulation technique and active amplifying technique, therefore have defectives such as noise is big, source impedance accommodation is less, and anti-common mode interference ability is lower than the photoelectricity galvanometer.Digital nanovoltmeter because himself defective does not reach the high-acruracy survey requirement, therefore, can not replace photoelectricity to amplify galvanometer and use in high-acruracy survey equipment such as potential difference meter and electric bridge.
Summary of the invention
The present invention is directed to the shortcoming and defect that digital nanovoltmeter exists in the prior art, a kind of high-sensitivity digital nanovoltmeter is provided, it has very strong anti-common mode interference ability and shock resistance, can be applicable to high-acruracy survey equipment such as potential difference meter and electric bridge.The invention still further relates to a kind of implementation method of high-sensitivity digital nanovoltmeter.
Technical scheme of the present invention is following:
A kind of high-sensitivity digital nanovoltmeter; Comprise the measurement loop that is composed in series by conversion galvanometer and feedback resistive network; Said feedback resistive network is composed in parallel by feedback resistance and divider resistance, wherein serial connection one D/A converter on the branch road of said feedback resistance; Also comprise a CCD circuit; Said CCD circuit links to each other with cpu circuit; Said CCD circuit is gathered the galvanometric dot pattern picture of conversion, and with in the said dot pattern picture input cpu circuit, said cpu circuit is controlled said D/A converter to the feedback resistive network output dc voltage.
One photoelectricity is set between said cpu circuit and the D/A converter isolates.
A kind of method that adopts high-sensitivity digital nanovoltmeter as claimed in claim 1 to realize low pressure inspection stream; Its step comprises: 1) when the DC voltage of tested voltage and D/A converter output is 0; Cpu circuit extracts optical spot centre position in the CCD circuit output dot pattern picture, preserves as initial point; When 2) beginning to measure, said tested voltage is added in measurement two ends, loop, said cpu circuit extracts optical spot centre position in the CCD circuit output dot pattern picture, compares with said initial point; 3) increase the DC voltage that said D/A converter is exported by turn, overlap with said initial point, the DC voltage U of record said D/A converter output this moment until said optical spot centre position DA 04) cpu circuit calculates tested voltage U according to equation (1) x:
U x = R g R g + R f U DA 0 - - - ( 1 )
In the formula, R fThe resistance of-feedback resistance 21; R gThe resistance of-divider resistance 22.
The best result of said digital nanovoltmeter is distinguished power U Δ:
U Δ = d × C 1 × R i × 10 - 3 2 l - - - ( 2 )
In the formula: the photoelectronic imaging figure unit interval of d-CCD circuit, unit is μ m; C 1-conversion galvanometer current constant, unit is A/mm/m; R iThe resistance value of coil in the-conversion galvanometer, unit is Ω; The galvanometric reflective mirror of l-conversion is to the light path of CCD circuit, and unit is m.
Use line fitting method that said dot pattern is looked like to carry out filtering in the said cpu circuit.
Technique effect of the present invention is following:
High-sensitivity digital nanovoltmeter of the present invention is provided with one and becomes the conversion galvanometer and of deflection laser to be used for the feedback resistive network of dividing potential drop the current conversion measuring on the loop; CCD (Charge Coupled Device; The CCD imageing sensor) the galvanometric dot pattern picture of circuit receiving conversion; Afterwards with handling in the dot pattern picture input cpu circuit, cpu circuit is through filtering and calculate the position of luminous point; Cpu circuit is controlled D/A converter simultaneously, and it exports a direct current voltage; When this DC voltage offsets through feedback resistive network voltage after partial and tested voltage; Measuring current in loop is 0; Light spot position in the dot pattern picture of CCD circuit output is in initial point, and the DC voltage of cpu circuit D/A converter output is at this moment exported as detected voltage to be measured; Be respectively fully independently electric system owing to measure loop, feedback circuit and testing circuit; Only there is the light signal contact between the each several part; Therefore have very strong anti-common mode interference ability, can be used as high sensitivity nulling instrument and be applied to high-acruracy survey equipment such as potential difference meter and electric bridge.
Because the thermal noise voltage of conversion galvo coil internal resistance is less than 0.5nV; And background noise is low; And the dot pattern picture that the CCD circuit records obtains comparatively stable measurement result through the cpu circuit digital filtering; Therefore the present invention can overcome the influence of the factors such as Brownian movement of the earth vibration, air molecule, has the characteristics of stable reading.
Because the measuring accuracy of high-sensitivity digital nanovoltmeter is by the accuracy of resistance ratio in the feedback resistive network and the accuracy decision of D/A converter; And the resistance of pin-point accuracy and D/A converter are easy to accomplish in the prior art, so the present invention can realize the high measurement accuracy of DC low-voltage.Resolving power of the present invention can improve through spacing, increasing light path and the galvanometric sensitivity of raising conversion that reduces the CCD circuit simultaneously, utilizes common magnetoelectricity series to exchange the resolving power that meter can reach 1nV.
Because the present invention uses the output of cpu circuit control D/A converter, thereby directly obtains measurement result, and need not to increase A/D converter again, so mimic channel is succinct, need carry out the circuit hardware and software debugging hardly, is convenient to produce in batches.
Description of drawings
Fig. 1 is the structural representation of apparatus of the present invention
Fig. 2 is a Flame Image Process process flow diagram in the cpu circuit of the present invention
Each label is listed as follows among the figure:
1-conversion galvanometer; The 11-light-emitting component; 12 reflective mirrors; The 13-coil; The 2-feedback resistive network; The 21-feedback resistance; The 22-divider resistance; The 3-CCD circuit; The 4-CPU circuit; 5-photoelectricity is isolated; The 6-D/A converter; The 7-digital indicator.
Embodiment
The present invention will be described below in conjunction with accompanying drawing.
As shown in Figure 1, high-sensitivity digital nanovoltmeter of the present invention comprises by conversion galvanometer 1, feedback resistive network 2, CCD circuit 3, cpu circuit 4, photoelectricity isolation 5, D/A converter 6 and digital indicator 7.Wherein, conversion galvanometer 1 is composed in series with feedback resistive network 2 and measures the loop, measures the tested voltage U of loop two terminations x, the measurement current in loop is I xConversion galvanometer 1 mainly comprises light-emitting component 11, reflective mirror 12 and coil 13, electric current I xDrive reflective mirror 12 deflection certain angles, the light beam that light-emitting component 11 sends forms images on CCD circuit 3 through after the reflection of reflective mirror 12.Cpu circuit 4 reads the luminous point view data of CCD circuit 3 outputs, confirms the luminous point image space in the dot pattern picture through filter processing method; Cpu circuit 4 also sends instruction to D/A converter 6 simultaneously, controls the DC voltage U that its output one increases progressively by turn DA, photoelectricity is set between cpu circuit 4 and the D/A converter 6 isolates 5.Feedback resistive network 2 is composed in parallel by feedback resistance 21 and divider resistance 22, wherein serial connection D/A converter 6 on the branch road of feedback resistance 21.The DC voltage U of D/A converter 6 outputs DAThrough after the dividing potential drop of divider resistance 22, on feedback resistance 21, form a feedback pressure drop U f, when tested voltage U xWith the feedback pressure drop U on the feedback resistance 21 fPressure differential deltap be not 0 o'clock, in measuring the loop, form electric current I x
Implementation method of the present invention is:
(1) cpu circuit 4 at first carries out initialization, when tested voltage U xDC voltage U with D/A converter 6 DABe at 0 o'clock, cpu circuit 4 reads the luminous point view data of CCD circuit 3 outputs.After cpu circuit 4 carries out digital filtering with the luminous point view data that reads, extract the reflection light point center of eliminating vibration and noise effect, this reflection light point center is preserved as initial point.This initial point is when reflective mirror 12 does not rotate in the conversion galvanometer 1, the position of luminous point in the CCD circuit 3 output dot pattern pictures.
When (2) beginning to measure, with tested voltage U xBe added in and measure the two ends, loop, the DC voltage U of D/A converter 6 outputs DABe set to 0, cpu circuit 4 reads the luminous point view data of CCD circuit 3 outputs, and through behind the digital filtering, the reflection light point center after vibration and the noise effect is eliminated in extraction, and this reflection light point center and the initial point that prestores are compared.
(3) increase the DC voltage U that D/A converter 6 is exported by turn DA, make the feedback pressure drop U on the feedback resistance 21 fBe tending towards tested voltage U x, measure electric current I in the loop xReduce gradually, the deflection angle of the reflective mirror 12 of conversion galvanometer 1 is tending towards 0.In the CCD circuit 3 output dot pattern pictures that cpu circuit 4 collects, initial point is got back at the reflection light point center gradually.The DC voltage U of D/A converter 6 outputs during beginning DAStepping can be bigger so that feedback pressure drop U fThe tested voltage U of convergence fast xAs feedback pressure drop U fNear tested voltage U xThe time, dwindle DC voltage U DAStepping, to improve accuracy of detection.
(4) as feedback pressure drop U fFinally equal tested voltage U xThe time, measure electric current I in the loop xBe 0, the deflection angle of the reflective mirror 12 of conversion galvanometer 1 is 0, and initial point is got back at the reflection light point center gradually, finally overlaps with initial point, and system reaches balance, and the balanced voltage of D/A converter 6 outputs was U when then system reached balance DA 0
(5) cpu circuit 4 is according to balanced voltage U DA 0, can obtain tested voltage U through equation (1) xCpu circuit 4 passes through digital indicator 7 with tested voltage U xOutput shows.
U x = R g R g + R f U DA 0 - - - ( 1 )
In the formula,
R fThe resistance of-feedback resistance 21;
R gThe resistance of-divider resistance 22.
The best result of digital nanovoltmeter of the present invention distinguishes that power is that luminous point changes 1 pairing input voltage of unit interval on the photoelectronic imaging figure of CCD circuit 3, and according to conversion galvanometer and CCD circuit measuring structural principle, the best result of can deriving is distinguished power U ΔFor:
U Δ = d × C 1 × R i × 10 - 3 2 l - - - ( 2 )
In the formula:
The photoelectronic imaging figure unit interval of d-CCD circuit 3, unit is μ m;
C 1-conversion galvanometer 1 current constant, unit is A/mm/m;
R iThe resistance value of coil 13 in the-conversion galvanometer 1, unit is Ω;
The reflective mirror 12 of l-conversion galvanometer 1 is to the light path of CCD circuit 3, and unit is m.
Can know that by equation (2) the photoelectronic imaging figure unit interval d of CCD circuit 3 is more little, light path l is longer, the sensitivity of conversion galvanometer 1 is just high more, thereby the best result of digital nanovoltmeter is distinguished power U ΔAlso high more.For example, as d=4 μ m, C 1=4 * 10 -9A/mm/m, R i=50 Ω, during l=0.4m, best result is distinguished power U Δ=1nV.
In the cpu circuit 4 of the present invention, use the line fitting method that is used for Image Edge-Detection in the existing method, the luminous point view data of CCD circuit 3 outputs is carried out filtering.Specifically be to utilize line fitting method, at first obtain one group of possible rim value, the intermediate value of edge calculation value is as the final rim value of luminous point again.As shown in Figure 2, its implementation process is:
(a) cpu circuit 4 is gathered the dot pattern picture of CCD circuit 3 outputs;
(b) if the bright spot quantity of judging continuous image vegetarian refreshments in the dot pattern picture greater than 8, is then chosen the starting point and the terminating point of 10 continuous bright spots, choose the starting point and the terminating point that comprise continuous bright spot scope maximum; If the bright spot quantity of continuous image vegetarian refreshments is less than 8 in the dot pattern picture, then gather the dot pattern picture of CCD circuit 3 outputs again, repeat deterministic process;
(c) calculate the above-mentioned maximum starting point of continuous bright spot scope and the intermediate value of terminating point of comprising, as the center of luminous point in the dot pattern picture.
Can filter out the luminous point error code that causes owing to light diffraction, error code transmission etc. through above method, and threshold values can be regulated according to circumstances also for being provided with in advance, threshold value gets 8 in the present embodiment.Get two maximum values of scope as starting point and terminating point, calculating intermediate point then is optical spot centre, can eliminate the influence that causes because of spot wobble like this.
Should be pointed out that the above embodiment can make those skilled in the art more fully understand the invention, but do not limit the present invention in any way creation.Therefore; Although this instructions has carried out detailed explanation with reference to accompanying drawing and embodiment to the invention,, those skilled in the art are to be understood that; Still can make amendment or be equal to replacement the invention; In a word, all do not break away from the technical scheme and the improvement thereof of the spirit and the scope of the invention, and it all should be encompassed in the middle of the protection domain of the invention patent.

Claims (5)

1. a high-sensitivity digital nanovoltmeter is realized the method that the low pressure inspection is flowed, and its step comprises:
1) makes high-sensitivity digital nanovoltmeter; Comprise the measurement loop that is composed in series by conversion galvanometer and feedback resistive network; Said feedback resistive network is composed in parallel by feedback resistance and divider resistance, wherein serial connection one D/A converter on the branch road of said feedback resistance; Also comprise a CCD circuit; Said CCD circuit links to each other with cpu circuit; Said CCD circuit is gathered the galvanometric dot pattern picture of conversion, and with in the said dot pattern picture input cpu circuit, said cpu circuit is controlled said D/A converter to the feedback resistive network output dc voltage;
2) when the DC voltage of tested voltage and D/A converter output is 0, cpu circuit extracts optical spot centre position in the CCD circuit output dot pattern picture, preserves as initial point;
When 3) beginning to measure, said tested voltage is added in measurement two ends, loop, said cpu circuit extracts optical spot centre position in the CCD circuit output dot pattern picture, compares with said initial point;
4) increase the DC voltage that said D/A converter is exported by turn, overlap with said initial point, the DC voltage U of record said D/A converter output this moment until said optical spot centre position DA 0
5) cpu circuit calculates tested voltage U according to equation (1) x:
U x = R g R g + R f U DA 0 - - - ( 1 )
In the formula,
R fThe resistance of-feedback resistance 21;
R gThe resistance of-divider resistance 22.
2. high-sensitivity digital nanovoltmeter as claimed in claim 1 is realized the method for low pressure inspection stream, it is characterized in that: a photoelectricity is set between said cpu circuit and the D/A converter isolates.
3. according to claim 1 or claim 2 high-sensitivity digital nanovoltmeter is realized the method for low pressure inspection stream, and it is characterized in that: the best result of said digital nanovoltmeter is distinguished power U A:
U Δ = d × C 1 × R i × 10 - 3 2 l - - - ( 2 )
In the formula:
The photoelectronic imaging figure unit interval of d-CCD circuit, unit is μ m;
C I-conversion galvanometer current constant, unit is A/mm/m;
R iThe resistance value of coil in the-conversion galvanometer, unit is Ω;
The galvanometric reflective mirror of l-conversion is to the light path of CCD circuit, and unit is m.
4. according to claim 1 or claim 2 high-sensitivity digital nanovoltmeter is realized the method for low pressure inspection stream, it is characterized in that: use line fitting method that said dot pattern is looked like to carry out filtering in the said cpu circuit.
5. high-sensitivity digital nanovoltmeter as claimed in claim 3 is realized the method for low pressure inspection stream, it is characterized in that: use line fitting method that said dot pattern is looked like to carry out filtering in the said cpu circuit.
CN 200910243512 2009-12-24 2009-12-24 High-sensitivity digital nanovoltmeter and realization method thereof Active CN101738537B (en)

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CN1614434A (en) * 2004-12-09 2005-05-11 中国科学院物理研究所 Superconductive conversion magnetic signal detecting system for high-voltage experiment
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CN101256220A (en) * 2008-01-02 2008-09-03 中国科学院物理研究所 System for detecting oscillatory type AC magnetic signal for high pressure experiment

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