CN102697500A - Current source application system applied to multi-frequency electrical impedance tomography and implementing method for system - Google Patents
Current source application system applied to multi-frequency electrical impedance tomography and implementing method for system Download PDFInfo
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- CN102697500A CN102697500A CN2012101889555A CN201210188955A CN102697500A CN 102697500 A CN102697500 A CN 102697500A CN 2012101889555 A CN2012101889555 A CN 2012101889555A CN 201210188955 A CN201210188955 A CN 201210188955A CN 102697500 A CN102697500 A CN 102697500A
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Abstract
The invention discloses a current source application system applied to multi-frequency electrical impedance tomography and an implementing method for the system. The system comprises a current source and a load communicated with the current source through a current source output channel; a comprehensive ground capacitor Cs connected in parallel with the load is arranged on the current source output channel; the comprehensive ground capacitor Cs is also connected in parallel with a compensating circuit which is used for reducing the deviation of an ideal output current injection imaging target body and has negative capacitive property -Ccom; and the equivalent parallel capacitance of the comprehensive ground capacitor Cs and the compensating circuit is Ceq=Cs-Ccom. The system solves the problems that voltage distribution in the imaging target body deviates from that in an ideal state, data acquired by an acquisition system are distorted and even imaging fails because the current injected to the imaging target body has certain deviation from the ideal output current of a constant alternating current source due to the ground capacitor on the current output channel of the constant alternating current source in the prior art and is easily nonlinearly changed together with the change of the impedance of the load.
Description
Technical field
The present invention relates to a kind of current source application system, specifically, relate to a kind of current source application system and its implementation that is applied to the multifrequency electrical impedance tomography.
Background technology
The multifrequency electrical impedance tomography is a kind of harmless harmless novel imaging technique; It is through injecting the ac-excited electric current of low-power of different frequency at surface to be measured placement electrode and to electrode; Use detecting electrode to survey the distribution of impedance characteristic of body to be measured inside under different frequency then; Because the spectral characteristic that under different frequency, appears of each biology is different, just can on 26S Proteasome Structure and Function, react the physiological property of each biological tissue, it has, and cost is low, volume is little, to early stage cancer sensitivity, data acquisition and image taking speed than advantages such as height; Can be used for the patient is carried out real-time for a long time, dynamic monitoring, have medical application prospect widely.
The factor that influences multifrequency electrical impedance tomography quality comprises stability and the accuracy of data collecting system and the reliability of imaging algorithm of hardware driving source.The electrical impedance tomography technical field mainly uses AC constant-current source as the hardware driving source now; But the AC constant-current source in the electrical impedance tomography system is owing to receive the electronic component parasitic capacitance; Circuit board cabling stray capacitance; The direct-to-ground capacitance of the active device that electric current is flowed through, (this patent is referred to as the comprehensive direct-to-ground capacitance on the current output channels with above-mentioned influence factor, uses C in many-sided influences such as electric current output cable distribution capacity
SExpression); The electric current of actual injection imageable target body and the desirable output current of AC constant-current source have certain deviation; And this electric current produces nonlinear variation along with the variation of exciting signal frequency and load impedance easily, and then causes that voltage distributes and perfect condition generation deviation on the imageable target body, and also can form bigger system deviation between the different frequency; The data distortion that finally causes acquisition system to be gathered, even cause the imaging failure.
In order to reduce the distortion rate of data acquisition, improve imaging effect, need to reduce the comprehensive direct-to-ground capacitance C of AC constant-current source output channel
STraditional processing means have the circuit board cabling of shortening and output cable, adopt the coaxial cable output current to reduce direct-to-ground capacitance, but its clinical effectiveness are limited; In order to eliminate the influence of analog switch; Traditional design also has a plurality of and line current source output of employing; Each excitation passage adopts independently current source; Between difference excitation passage, switch the negative effect of bringing into through analog switch to eliminate the single current source, but such processing mode the complexity and the system cost of system have been increased, especially is difficult to guarantee the unanimity row between a plurality of driving sources; Also can be through increasing compensating inductance at the current source outfan; Form the influence that parallel resonance is eliminated the current output channels direct-to-ground capacitance through compensating inductance and current output channels direct-to-ground capacitance; But this method can only compensate single-frequency, and then meaning for multi-frequency electrical impedance tomography system to increase a plurality of compensating circuits, in order to improve system response time; Often with output simultaneously after the sinusoidal signal stack mixing of a plurality of frequencies, so compensatory device has received great restriction.
Summary of the invention
The object of the present invention is to provide a kind of current source application system and its implementation that is applied to the multifrequency electrical impedance tomography; Solve feasible being injected into of the comprehensive direct-to-ground capacitance that exists on the current output channels of the AC constant-current source that exists in the prior art and deviation occurs as the electric current of objective body and the desirable output current of AC constant-current source; And then cause that voltage distributes and perfect condition generation deviation on the imageable target body; The data distortion that finally causes acquisition system to be gathered, even the problem that causes imaging to fail.
To achieve these goals, the technical scheme of the present invention's employing is following:
Be applied to the current source application system of multifrequency electrical impedance tomography, comprise current source and, have the comprehensive direct-to-ground capacitance C that is in parallel with this load on this current source output channel through the load that the current source output channel is communicated with this current source
S, said comprehensive direct-to-ground capacitance C
SAlso be parallel with and be used to reduce desirable output current and be injected into and possess negative capacitance characteristic-C as the deviation of objective body
ComCompensating circuit, and this comprehensive direct-to-ground capacitance C
SWith the equivalent parallel electric capacity of compensating circuit be: C
Eq=C
s-C
Com
Specifically, said current source output channel is at least any one in the active device that printed board cabling, electric current output cable, connector, electric current flow through.Said comprehensive direct-to-ground capacitance C
SBe at least the direct-to-ground capacitance of the active device that electronic component parasitic capacitance, circuit board cabling stray capacitance, electric current flow through, in the electric current output cable distribution capacity any one.Said possess negative capacitance characteristic-C
ComCompensating circuit be components and parts or module with negative capacitance characteristic; For example: the compensating circuit that constitutes by operational amplifier and the electric capacity that links to each other with this operational amplifier and resistance; The compensating circuit that perhaps constitutes by operational amplifier and the electric capacity that links to each other with this operational amplifier and digital adjustable potentiometer.
Be the basis with above-mentioned hardware system, the implementation method of above-mentioned application system provided by the invention may further comprise the steps:
(1) is communicated with current source and load through the current source output channel;
(2) all electric capacity that are set on the current source output channel are comprehensive direct-to-ground capacitance C
S, at this comprehensive direct-to-ground capacitance C
SThe two ends parallel connection possesses negative capacitance characteristic-C
ComCompensating circuit, then comprehensive direct-to-ground capacitance C
SWith the equivalent parallel electric capacity of compensating circuit be: C
Eq=C
s-C
Com
(3) adjustment compensating circuit parameter makes compensating circuit and comprehensive direct-to-ground capacitance C
SEquivalent parallel electric capacity in C
s=C
Com, promptly the equivalent parallel electric capacity of the two is: C
Eq=C
s-C
Com=0, thus make comprehensive direct-to-ground capacitance C under the duty
SInfinitely small with the equivalent parallel electric capacity of compensating circuit, the shunting that occurs thus is then infinitely small;
(4) open current source, making current source is the load injection current through the current source output channel.
Specifically, in said method, said current source output channel is at least any one in the active device that printed board cabling, electric current output cable, connector, electric current flow through.Said comprehensive direct-to-ground capacitance C
SBe at least the direct-to-ground capacitance of the active device that electronic component parasitic capacitance, circuit board cabling stray capacitance, electric current flow through, in the electric current output cable distribution capacity any one.Said possess negative capacitance characteristic-C
ComCompensating circuit be components and parts or module with negative capacitance characteristic; For example: the compensating circuit that constitutes by operational amplifier and the electric capacity that links to each other with this operational amplifier and resistance; The compensating circuit that perhaps constitutes by operational amplifier and the electric capacity that links to each other with this operational amplifier and digital adjustable potentiometer.
Compared with prior art, the present invention has following beneficial effect:
The present invention through the outfan of AC constant-current source over the ground between one of series connection have negative capacitance characteristic-C
ComCompensating circuit, make the comprehensive direct-to-ground capacitance C on itself and the current source output channel
SParallel connection is through making the equivalent parallel capacitor C of the two
Eq=C
s-C
Com=0, thus make comprehensive direct-to-ground capacitance C under the duty
SInfinitely small with the equivalent parallel electric capacity of compensating circuit, and then greatly reduce comprehensive direct-to-ground capacitance C
SInfluence to the shunt effect of load has reduced comprehensive direct-to-ground capacitance C
SIn wide frequency ranges,, make the current deviation that gets into the imageable target body reduce greatly, thereby avoided loss of data, guaranteed image quality the influence of current source output current.
2. has negative capacitance characteristic-C among the present invention
ComCompensating circuit multiple design is arranged; And can be placed on any position of current source output channel; Can select for use flexibly and arrange according to practical situation during use; So just be that circuit design and configuration provide ten minutes to adjust the space flexibly, and then greatly reduce design difficulty, finally reached the purpose that reduces the system design cost.
3. the present invention is according to the comprehensive direct-to-ground capacitance C of current output channels
SMeasurement result, designed the compensating circuit that possesses the negative capacitance characteristic dexterously and compensated, not only compensation method is very simple, and uses this compensation method can weaken the comprehensive direct-to-ground capacitance C of current source output channel greatly
SNegative effect, have very significant effect.
4. the present invention can also carry out dynamic evaluation to compensation result through the current detecting feedback element; And can be optimized compensation precision according to assessment result; Thereby realize the basis for follow-up technological expansion provides, further improved application prospect and using value.
5. the present invention can adopt a plurality of current source parallel operations; Also can select wherein one or more to carry out work through selector switch, therefore, the present invention not only has the scope of application widely, and its occupation mode also very flexibly.
6. the present invention has the little characteristic of frequency dependence, can the AC signal in the broad frequency effectively be compensated; Simultaneously, also have the little characteristic of waveform morphology dependency, can the AC signal of any form effectively be compensated; So just further improve range of application of the present invention and application prospect, further improved practical value of the present invention.
Description of drawings
Fig. 1 is the current source output sketch map of existing electrical impedance tomography system.
Fig. 2 is the circuit diagram of the present invention-embodiment 1.
Fig. 3 is the circuit diagram of the present invention-embodiment 2.
Fig. 4 is the circuit diagram of the present invention-embodiment 3.
The specific embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is described further, embodiment of the present invention includes but not limited to the following example.
Like Fig. 1, shown in 2, be applied to the current source application system of multifrequency electrical impedance tomography, comprise current source and, have the comprehensive direct-to-ground capacitance C that is in parallel with this load on this current source output channel through the load that the current source output channel is communicated with this current source
S, said comprehensive direct-to-ground capacitance C
SAlso be parallel with and be used to reduce desirable output current and be injected into and possess negative capacitance characteristic-C as the deviation of objective body
ComCompensating circuit, and this comprehensive direct-to-ground capacitance C
SWith the equivalent parallel electric capacity of compensating circuit be: C
Eq=C
s-C
Com
Wherein, the current source output channel is an electric current output cable; Possesses negative capacitance characteristic-C
ComCompensating circuit directly select components and parts with negative capacitance characteristic; Comprehensive direct-to-ground capacitance C
SThe direct-to-ground capacitance of the active device of flowing through for electronic component parasitic capacitance, circuit board cabling stray capacitance, electric current, electric current output cable distribution capacity sum.
Because the comprehensive direct-to-ground capacitance C of current output channels
SBe connected in parallel in the load, can form the shunting to load current, to such an extent as to influence the result of data acquisition and the quality of imaging, for addressing this problem, present embodiment is the basis with above-mentioned hardware configuration, adopts following method to compensate and supplies stream:
At first, be communicated with current source and load through the current source output channel; And at comprehensive direct-to-ground capacitance C
SThe two ends parallel connection possesses negative capacitance characteristic-C
ComCompensating circuit, then comprehensive direct-to-ground capacitance C
SWith the equivalent parallel electric capacity of compensating circuit be: C
Eq=C
s-C
Com
Then, adjustment compensating circuit parameter makes C
s=C
Com, promptly the equivalent parallel electric capacity of the two is:
C
eq=C
s-C
com=0；
At this moment, only need open current source, making current source is the load injection current through the current source output channel, and entire circuit is just started working, in the current delivery process, owing to possess negative capacitance characteristic-C
ComThe effect of compensating circuit, make comprehensive direct-to-ground capacitance C under the duty
SInfinitely small with the equivalent parallel electric capacity of compensating circuit, the shunting that occurs thus is then infinitely small, thereby has realized eliminating to greatest extent comprehensive direct-to-ground capacitance C
STo the shunt effect that load forms, make the electric current that injects load be infinitely close to the electric current that current source is exported, and and frequency-independent.And in real work, load is imageable target, therefore, through said method, has finally solved being injected into of existing in the prior art effectively and has had the problem of deviation as the desirable output current of the electric current of objective body and AC constant-current source, has guaranteed image quality.
Embodiment 2
As shown in Figure 3; The difference of present embodiment and embodiment 1 is; Present embodiment adopts a concrete active negative capacitance to compensate, and the current source output channel is the electronic component that output current is flowed through, and comprehensive direct-to-ground capacitance is present on the electronic component that output current flows through; Correspondingly, we will possess negative capacitance characteristic-C
ComThe compensating circuit module be parallel to the electronic component two that output current flows through and bring in the compensation of realization comprehensive direct-to-ground capacitance.
Because the common components and parts accuracy of manufacture with negative capacitance characteristic is lower; Its compensation effect is also relatively poor; For obtain high-precision compensation effect we use compensating circuit module that the compensating circuit based on the emulation negative capacitance constitutes by way of compensation circuit comprehensive direct-to-ground capacitance is compensated; Should be based on the compensating circuit of emulation negative capacitance by a plurality of passive devices, resistance R 1 as shown in Figure 3, resistance R 2, capacitor C 1 and operational amplifier etc. are formed by connecting.
The compensation principle of this instance is: node 6 possesses identical voltage with node 7, so the voltage at node 8 places is:
V
out=Vi*(1+R1/R2)
I is the electric current of capacitor C 1 of flowing through, and its value is:
The equiva lent impedance of this compensating circuit is:
Can draw thus; This compensating circuit can be regarded the negative capacitance of appearance value for
as, and promptly its equivalent capacity is
According to the comprehensive direct-to-ground capacitance C on the current output channels
sMeasurement data or assessment data, select suitable resistance R 1, resistance R 2, capacitor C 1, and it satisfied through fine setting
Just can reduce comprehensive direct-to-ground capacitance C
sInfluence, we also can replace the digital adjustable potentiometer of resistance R 1 or resistance R 2 usefulness, make load obtain maximum voltage amplitude through the adjustment potentiometer.
Embodiment 3
As shown in Figure 4; The difference of present embodiment and embodiment 2 is, in order to realize the dynamic compensation to current source, in the present embodiment; Also comprise the current sense resistor that is serially connected in the current source output channel; In order to detecting the current detection circuit of current source output current, in order to detecting the load voltage testing circuit of load voltage, and the signal that above-mentioned testing circuit detects carried out collection analysis and carry out the data acquisition and the Based Intelligent Control processing unit of feedback control; Equally; We are parallel to the electronic component two that output current flows through with compensating circuit and bring in the compensation of realization to comprehensive direct-to-ground capacitance, and through data acquisition and Based Intelligent Control processing unit compensation effect are assessed, and the parameter through control line control adjustment compensating circuit is to obtain best compensation effect then.
Based on same reason; We use based on the compensating circuit of emulation negative capacitance by way of compensation circuit come comprehensive direct-to-ground capacitance is compensated; Specifically, said compensating circuit based on the emulation negative capacitance comprises operational amplifier and the electric capacity and the digital adjustable potentiometer that link to each other with this operational amplifier.
In this instance; Current detection circuit is through sending into data acquisition after the voltage signal on the current sense resistor is handled and the Based Intelligent Control processing unit carries out sampling analysis; According to the resistance of the digital adjustable potentiometer in analysis result control and the adjustment negative capacitance compensating circuit to obtain current value near the theoretical output of current source; Present embodiment can utilize switch with standard testing resistance as the current source load place in circuit; Utilize the load voltage testing circuit that the voltage signal in the load is carried out sampling analysis then; Control and adjust the resistance of digital adjustable potentiometer according to analysis result; Make the voltage signal in the load maximum, perhaps utilize the resistance of detected current value of current detection circuit and the detected magnitude of voltage computational load of load voltage testing circuit simultaneously, and make the load resistance that calculates near the actual loading resistance through adjusting digital adjustable potentiometer.
Negative capacitance compensating circuit among the present invention can be positioned on any position of current source output channel; As long as guarantee that it is parallel with one another with comprehensive direct-to-ground capacitance; Its compensation effect can be measured through external measurement device and judge, also can judge automatically through system.
The compensating circuit that has the negative capacitance characteristic among the present invention includes but not limited to the circuit that provides in the foregoing description.
According to the foregoing description, just can realize the present invention well.
Claims (8)
1. be applied to the current source application system of multifrequency electrical impedance tomography, comprise current source and, have the comprehensive direct-to-ground capacitance C that is in parallel with this load on this current source output channel through the load that the current source output channel is communicated with this current source
S, it is characterized in that said comprehensive direct-to-ground capacitance C
SAlso be parallel with and be used to reduce desirable output current and be injected into and possess negative capacitance characteristic-C as the deviation of objective body
ComCompensating circuit, and this comprehensive direct-to-ground capacitance C
SWith the equivalent parallel electric capacity of compensating circuit be: C
Eq=C
s-C
Com
2. the current source application system that is applied to the multifrequency electrical impedance tomography according to claim 1; It is characterized in that said current source output channel is at least any one in the active device that printed board cabling, electric current output cable, connector, electric current flow through.
3. the current source application system that is applied to the multifrequency electrical impedance tomography according to claim 2 is characterized in that, said comprehensive direct-to-ground capacitance C
SBe at least the direct-to-ground capacitance of the active device that electronic component parasitic capacitance, circuit board cabling stray capacitance, electric current flow through, in the electric current output cable distribution capacity any one.
4. the current source application system that is applied to the multifrequency electrical impedance tomography according to claim 3 is characterized in that, said possess negative capacitance characteristic-C
ComCompensating circuit be components and parts or module with negative capacitance characteristic.
5. be applied to the implementation method of the current source application system of multifrequency electrical impedance tomography, it is characterized in that, may further comprise the steps:
(1) is communicated with current source and load through the current source output channel;
(2) all electric capacity that are set on the current source output channel are comprehensive direct-to-ground capacitance C
S, at this comprehensive direct-to-ground capacitance C
SThe two ends parallel connection possesses negative capacitance characteristic-C
ComCompensating circuit, then comprehensive direct-to-ground capacitance C
SWith the equivalent parallel electric capacity of compensating circuit be: C
Eq=C
s-C
Com
(3) adjustment compensating circuit parameter makes compensating circuit and comprehensive direct-to-ground capacitance C
SEquivalent parallel electric capacity in C
s=C
Com, promptly the equivalent parallel electric capacity of the two is: C
Eq=C
s-C
Com=0, thus make comprehensive direct-to-ground capacitance C under the duty
SInfinitely small with the equivalent parallel electric capacity of compensating circuit, the shunting that occurs thus is then infinitely small;
(4) open current source, making current source is the load injection current through the current source output channel.
6. the implementation method that is applied to the current source application system of multifrequency electrical impedance tomography according to claim 5; It is characterized in that said current source output channel is at least any one in the active device that printed board cabling, electric current output cable, connector, electric current flow through.
7. the implementation method that is applied to the current source application system of multifrequency electrical impedance tomography according to claim 6 is characterized in that, said comprehensive direct-to-ground capacitance C
SBe at least the direct-to-ground capacitance of the active device that electronic component parasitic capacitance, circuit board cabling stray capacitance, electric current flow through, in the electric current output cable distribution capacity any one.
8. the implementation method that is applied to the current source application system of multifrequency electrical impedance tomography according to claim 7 is characterized in that, said possess negative capacitance characteristic-C
ComCompensating circuit be components and parts or module with negative capacitance characteristic.
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| CN2012101889555A CN102697500A (en) | 2012-06-08 | 2012-06-08 | Current source application system applied to multi-frequency electrical impedance tomography and implementing method for system |
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|---|---|---|---|
| CN2012101889555A CN102697500A (en) | 2012-06-08 | 2012-06-08 | Current source application system applied to multi-frequency electrical impedance tomography and implementing method for system |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104605851A (en) * | 2015-02-16 | 2015-05-13 | 天津大学 | Electrical impedance tomography (EIT) system data acquisition method |
| WO2018201342A1 (en) * | 2017-05-03 | 2018-11-08 | 深圳市稳先微电子有限公司 | Small-capacitance compensated network circuit |
| CN110768524A (en) * | 2019-10-24 | 2020-02-07 | 西安锐智翼电子科技有限公司 | Power regulation method and device and charging equipment |
| CN112448680A (en) * | 2019-08-13 | 2021-03-05 | 中国科学院物理研究所 | Negative capacitance device, negative inductance device, and circuit including the same |
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| US4158787A (en) * | 1978-05-08 | 1979-06-19 | Hughes Aircraft Company | Electromechanical transducer-coupled mechanical structure with negative capacitance compensation circuit |
| CN1479328A (en) * | 2003-07-03 | 2004-03-03 | 杜维俭 | Aging circuit of capacitor |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104605851A (en) * | 2015-02-16 | 2015-05-13 | 天津大学 | Electrical impedance tomography (EIT) system data acquisition method |
| WO2018201342A1 (en) * | 2017-05-03 | 2018-11-08 | 深圳市稳先微电子有限公司 | Small-capacitance compensated network circuit |
| CN109417385A (en) * | 2017-05-03 | 2019-03-01 | 深圳市稳先微电子有限公司 | Small capacitances amount compensation network circuit |
| US10496116B2 (en) | 2017-05-03 | 2019-12-03 | Shenzhen Winsemi Microelectronics Co., Ltd. | Small capacitance compensation network circuit |
| CN109417385B (en) * | 2017-05-03 | 2022-03-11 | 深圳市稳先微电子有限公司 | Small capacitance compensation network circuit |
| CN112448680A (en) * | 2019-08-13 | 2021-03-05 | 中国科学院物理研究所 | Negative capacitance device, negative inductance device, and circuit including the same |
| CN110768524A (en) * | 2019-10-24 | 2020-02-07 | 西安锐智翼电子科技有限公司 | Power regulation method and device and charging equipment |
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Application publication date: 20121003 |