CN102707695B - Switching system for electrical impedance tomography - Google Patents
Switching system for electrical impedance tomography Download PDFInfo
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- CN102707695B CN102707695B CN201210188786.5A CN201210188786A CN102707695B CN 102707695 B CN102707695 B CN 102707695B CN 201210188786 A CN201210188786 A CN 201210188786A CN 102707695 B CN102707695 B CN 102707695B
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Abstract
The invention discloses a switching system for electrical impedance tomography (EIT). The switching system comprises a flexible flat cable pin-shaped socket, a D-SUB connector, four shape memory alloy (SMA) connectors, four groups of decoding circuits, four groups of electric control switch circuits and a shielding driving circuit, wherein the shielding driving circuit is connected with the D-SUB connector through a shielding signal connecting wire; the input ends of the four groups of electric control switch circuits are connected with the D-SUB connector through an internal connecting bus respectively; the input end of each group of decoding circuit is connected with the output end of a group of electric control switch circuit respectively; the output ends of the four groups of decoding circuits are connected to the same flexible flat cable pin-shaped socket; and each SMA connector is connected to a group of electric control switch circuit. The switching system is ingenious in concept; the switching system of the conventional EIT system forms a subsystem independent from a data acquisition system, so that an electrode distribution parameter is reduced; and due to the adoption of novel switches and a shielding driving technology, the whole EIT system has the advantages of high imaging accuracy, high imaging speed, long service life, wide working frequency range and the like.
Description
Technical field
The present invention relates to a kind of switching system, specifically, relate to a kind of switching system for electrical impedance tomography.
Background technology
Electrical impedance tomography (Electrical Impedance Tomography, EIT) is the technology of a kind of noninvasive resistivity distribution of take inside of human body rebuilding body inner tissue image that is target.Human body is a large bioelectricity conductor, each tissue, organ all have certain impedance, when the local organs generation pathology of human body, the impedance of part is inevitable different from other positions, thereby can to the pathology of human organ, diagnose by the measurement of impedance.Compare with the nuclear medicine technology such as CT, MRI, that EIT has is harmless harmless, cost is low, volume is little, safe, simple to operate, to advantages such as early carcinoma kitchen range sensitivities, doctor and patient are acceptant.But the imaging precision of EIT is relatively not high, because data acquisition and the image taking speed of EIT are higher, can be used for patient to carry out real-time, dynamic monitoring for a long time, there is medical application prospect widely.
EIT imaging is the inverse problem solution procedure of a Very Ill-conditioned, reconstitutes picture and is broadly divided into three classes: back projection, process of iteration, a step linear approach, above reconstruction algorithm is to all requirements to some extent of convergence.Therefore, no matter take which kind of data acquisition scheme, the picture quality of EIT imaging all depends on collected data precision, and very high to data accuracy requirement.According to EIT basic functional principle, EIT system architecture is basically identical, as numerous data about EIT aspect and patent (as CN03134598.0), describes, and all data acquisition system (DAS), electrode, excitation system, data processing and imaging system, consists of.The performance of electrode, data acquisition system (DAS) directly affects image data precision, thus image quality, and data acquisition system (DAS) comprises switching system, LNA, differential amplification, filtering, AD etc., wherein the design of switching system is difficult point.
At present, also there is many difficulties in EIT technology in clinical practice, and one of them is exactly that image data precision is not high enough, image quality is impacted, and then affect EIT system accuracy of detection.Switching system performance is undesirable is the key factor that causes data precision not high, particularly for working frequency range in the multifrequency EIT of 10KHz～1MHz system.Traditional E IT system has all adopted conventional Electronic Switching System, and has adopted cross bar switch and multiple-pole switch, attempts to reduce as much as possible the factor of paying no attention to that it brings.But the physical arrangement restriction due to conventional electronic switch, inevitably exist conducting resistance inconsistent, crosstalk, the number of drawbacks such as distortion, leakage, noise, and conventional Electronic Switching System can produce relatively large electric capacity, be generally 10～30pF, while using switch in parallel, electric capacity also can increase.And the capacity effect of conventional electronic switch, can affect greatly system input and output impedance, thereby cause collection signal waveform gross distortion, different greatly with the signal that system expectation detects, produce very serious data error, especially when system frequency is operated in 1MHz when following, this impact of experimental verification is very outstanding.Conventional electronic switch causes crosstalks, distortion, leakage, noise, capacity effect all can affect data precision and limit whole EIT system maximum operation frequency, is difficult to eliminate this defect at present from theoretical and technique.
Summary of the invention
The object of the present invention is to provide a kind of switching system for electrical impedance tomography, solve the phenomenon of crosstalking of adopting at present that conventional Electronic Switching System exists, distortion, leakage, noise, capacity effect and cause the problem that EIT system data precision and maximum operation frequency are not high.
To achieve these goals, the technical solution used in the present invention is as follows:
For a switching system for electrical impedance tomography, comprise winding displacement aciculiform socket, D-SUB connector, 4 SMA connectors, 4 groups of decoding schemes, 4 groups of electric-controlled switch circuit, shield guard circuit; Wherein, shield guard circuit is connected with D-SUB connector by shielded signal connecting line, pin one end of 4 groups of electric-controlled switch circuit is connected with D-SUB connector by interior connection bus respectively, the output terminal of every group of decoding scheme is connected with the control end of one group of electric-controlled switch circuit respectively, the input end of 4 groups of decoding schemes is connected on same winding displacement aciculiform socket, and each SMA connector is connected on the pin other end of one group of electric-controlled switch circuit.
Further, described electric-controlled switch circuit comprises multiselect one electric-controlled switch and switch driving circuit; Wherein, many signal pins end of multiselect one electric-controlled switch is connected in interior connection bus, mono signal leads ends is connected with SMA connector, and its control end is connected with the output terminal of switch driving circuit, and the input end of described switch driving circuit is connected with the output terminal of described decoding scheme.
Described decoding scheme comprises decoder chip and resistance; Wherein, the output terminal of decoder chip is connected with the input end of switch driving circuit, and the input end of decoder chip is connected with winding displacement aciculiform socket by resistance.
Described shield guard circuit comprises operational amplifier and resistance, and wherein, the output terminal of operational amplifier is connected with D-SUB connector; Resistance is arranged between the inverting input and output terminal of operational amplifier.
Again further, described winding displacement aciculiform socket is 24 faller gill line aciculiform sockets; Described decoder chip is 4-16 decoder chip; Described multiselect one electric-controlled switch is for to select 1 electric-controlled switch based on 16 of novel switched structure.
Compared with prior art, the present invention has following beneficial effect:
(1) the present invention is by adopting new electronic control switch combination to form switching system, overcome conventional electronic switch intrinsic crosstalk, the problem such as distortion, leakage, noise, capacity effect, EIT system data precision and maximum operation frequency have been improved, thereby improved the imaging precision of EIT system, expanded the band limits of multifrequency EIT system.
(2) electric-controlled switch that the present invention adopts has low delay, long-life feature, make phase delay time and the life-span of switching system approach conventional electronic switch, meet system requirements, and do not there is the problems such as the crosstalking of conventional electronic switch, distortion, leakage, noise, capacity effect.
(3) the present invention is independent from data acquisition system (DAS) by switching system, forms subsystem, greatly reduce the length of electrode, thus reduced electrode long cause crosstalk, the problem such as distributed capacitance.
(4) the present invention realizes shield guard technology by shield guard circuit, has further reduced the problems such as crosstalking of causing because electrode is long, capacity effect.
(5) the present invention is skillfully constructed, simple in structure, cheap, is applicable to applying.
Accompanying drawing explanation
Fig. 1 is the system chart of the present invention while being applied to Electrical Impedance Tomography System.
Fig. 2 is system principle diagram of the present invention.
Fig. 3 is the schematic block circuit diagram of shield guard circuit in the present invention.
Fig. 4 is the schematic block circuit diagram of 4-16 decoding scheme in the present invention.
Fig. 5 is 16 schematic block circuit diagram of selecting 1 electric-controlled switch circuit in the present invention.
Embodiment
Below in conjunction with drawings and Examples, the invention will be further described, and embodiments of the present invention include but not limited to the following example.
Embodiment
As depicted in figs. 1 and 2, should be a subsystem of EIT system for the switching system of electrical impedance tomography, EIT system mainly by master control, driving source, switching system, signal condition and acquisition system, image, is processed and master is aobvious and 16 electrodes form.And this switching system comprises input interface, output interface, 4 groups of 4-16 decoding schemes, selects 1 electric-controlled switch circuit, shield guard circuit for 4 group 16.Wherein, input interface comprises 24 faller gill line aciculiform sockets, D-SUB socket, 2 SMA connectors; 24 faller gill line aciculiform sockets are mainly used in receiving key control signal, wherein have 16 pins to connect 4 groups of decoding schemes, connect+5V of 2 pins power supply, 2 pin ground connection, connect-5V of 2 pins power supply, and all the other pin hoverings are reserved; D-SUB socket is totally 40 pins, is divided into 20 pins and lower 20 pins, and wherein, 16 pins in lower 20 pins are respectively used to connect 16 electrodes, receive 16 electrode signals; 2 SMA connectors connect respectively source+, source-signal, and source+, source-are the difference pumping signal that the driving source of EIT system produces.Output interface comprises D-SUB connector, 2 SMA connectors; Wherein 2 SMA connectors are exported respectively signal+, signal-signal to signal condition and the acquisition system of EIT system, and signal+, signal-are the channel signal after electrode and electric-controlled switch circuit are selected; 16 pins in upper 20 pins of D-SUB connector are for shielded signal corresponding to output electrode.The output terminal of 4 groups of 4-16 decoding schemes is connected with this 24 faller gill line aciculiform socket, the output terminal of every group of 4-16 decoding scheme connects respectively one group 16 and selects 1 electric-controlled switch circuit, select for every group 16 1 electric-controlled switch circuit to connect a SMA connector simultaneously, and the many signal pins end that selects 1 electric-controlled switch circuit for 4 group 16 is all connected in interior connection bus, and be connected with D-SUB socket by interior connection bus, electrode signal line.Described shield guard circuit is connected with D-SUB connector by shielded signal line.D-SUB socket and D-SUB connector complement one another, and are referred to as D-SUB connector.
To shield guard circuit, 4-16 decoder circuit and 16, select 1 electric-controlled switch circuit to be elaborated respectively below.
As shown in Figure 3, above-mentioned shield guard circuit consists of operational amplifier and resistance, and wherein, the two ends of resistance are inverting input and the output terminal of concatenation operation amplifier respectively, makes an emitter follower of the common formation of resistance and operational amplifier.The input end of this emitter follower is the in-phase input end of operational amplifier, the output terminal that output terminal is operational amplifier, and by the input end of emitter follower and a path electrode signal communication, corresponding output terminal is exported the shielded signal of this path electrode.The emitter follower that 16 route operational amplifiers and resistance form forms 16 road shield guard circuit altogether, i.e. 16 emitter followers, and they control respectively an electrode signal, exports a shielded signal, thus realization feeds back to electrode signal the function of screen layer.
As shown in Figure 4, above-mentioned 4-16 decoder circuit consists of 4-16 decoder chip and resistance, totally 4 groups of 4-16 decoder circuits in the present invention, and the digital control code that is used for respectively master control to send carries out decoding, produces 4 group of 16 control signal of selecting 1 electric-controlled switch circuit.The input end of switch driving circuit is directly connected with 16 output terminals of 4-16 code translator, and 4 digital input ends of 4-16 decoder chip are connected with 24 faller gill line aciculiform sockets after resistance in series respectively.The master control of EIT system is sent digital control code, first by resistance, then enters decoder chip and translates correct switch control code, and exports 16 to and select 1 electric-controlled switch.When there is digital high signal, be generally 3.3V, because decoder chip input impedance is large, need electric current little, the voltage difference at resistance two ends is very little, code translator input voltage is similar to 3.3V, increase resistance on normal decoding without impact; If most voltage outside, have very large surge voltage to arrive, although, at the input end of code translator, but due to the metering function of resistance, also can not cause damage to code translator.Code translator is worked according to normal 4-16 decoded mode, as shown in Table 1:
Table one
As shown in Figure 5, above-mentioned 16 select 1 electric-controlled switch circuit to consist of electric-controlled switch, triode and resistance, the present invention selects 1 electric-controlled switch circuit totally for 4 group 16, and each group connects a SMA connector, is used for inputting source+, source-signal and output signal+, signal-signal.Interconnective triode and resistance form the driving circuit of electric-controlled switch, to drive electric-controlled switch, and electric-controlled switch has without crosstalking, undistorted, ultralow leakage, ultra-low noise, ultralow conducting resistance, low delay, long-life feature, after 16 electric-controlled switch parallel connections, its control end is connected with switch driving circuit, form 16 and select 1 electric-controlled switch circuit, its many signal pins end is connected with SMA connector with the interior bus that is connected respectively with mono signal leads ends.Because electric-controlled switch control end need to consume very large electric current, and common digital device cannot drive, and therefore uses triode to realize and drives.Because 4-16 decoder circuit only has an output code at every turn, be 1, so this 16 selects 1 electric-controlled switch circuit also to only have an electric-controlled switch in closure state at every turn.
When EIT system works, its driving source circuit can provide pumping signal source+, source-, the electrode channel that simultaneously needs switching system that pumping signal is switched to the appointment output of getting on.Now master control first provides activation switch control code, and switching system of the present invention, after receiving activation switch control code, is connected the electrode signal passage of appointment and source+, source-respectively.Simultaneously, EIT system is after sending pumping signal, also to carry out measurement target signal by electrode, therefore the master control meeting of EIT system is sent potential electrode passage gating control code to switching system, switching system is after receiving this control code, respectively the electrode signal passage of appointment and signal+, signal-are connected, realized specifying the measurement of electrode channel differential signal.
Framework of the present invention and design are not only for the EIT system of 16 electrodes, can also, for the EIT system of other quantity electrodes, only need the joint quantity of the output terminal quantity of corresponding electric-controlled switch quantity, decoder chip and D-SUB connector be adjusted into identical with number of electrodes.The routine that above-mentioned variation belongs to the industry changes, and need not pay creative work, therefore, and within above-mentioned variation also belongs to protection scope of the present invention.
According to above-described embodiment, just can realize well the present invention.
Claims (7)
1. for a switching system for electrical impedance tomography, it is characterized in that, comprise winding displacement aciculiform socket, D-SUB connector, 4 SMA connectors, 4 groups of decoding schemes, 4 groups of electric-controlled switch circuit, shield guard circuit; Wherein, shield guard circuit is connected with D-SUB connector by shielded signal connecting line, pin one end of 4 groups of electric-controlled switch circuit is connected with D-SUB connector by interior connection bus respectively, the output terminal of every group of decoding scheme is connected with the control end of one group of electric-controlled switch circuit respectively, the input end of 4 groups of decoding schemes is connected on same winding displacement aciculiform socket, and each SMA connector is connected on the pin other end of one group of electric-controlled switch circuit.
2. a kind of switching system for electrical impedance tomography according to claim 1, is characterized in that, described electric-controlled switch circuit comprises multiselect one electric-controlled switch and switch driving circuit; Wherein, many signal pins end of multiselect one electric-controlled switch is connected in interior connection bus, mono signal leads ends is connected with SMA connector, and its control end is connected with the output terminal of switch driving circuit, and the input end of described switch driving circuit is connected with the output terminal of described decoding scheme.
3. a kind of switching system for electrical impedance tomography according to claim 2, is characterized in that, described decoding scheme comprises decoder chip and resistance; Wherein, the output terminal of decoder chip is connected with the input end of switch driving circuit, and the input end of decoder chip is connected with winding displacement aciculiform socket by resistance.
4. a kind of switching system for electrical impedance tomography according to claim 3, is characterized in that, described shield guard circuit comprises operational amplifier and resistance, and wherein, the output terminal of operational amplifier is connected with D-SUB connector; Resistance is arranged between the inverting input and output terminal of operational amplifier.
5. a kind of switching system for electrical impedance tomography according to claim 4, is characterized in that, described winding displacement aciculiform socket is 24 faller gill line aciculiform sockets.
6. a kind of switching system for electrical impedance tomography according to claim 5, is characterized in that, described decoder chip is 4-16 decoder chip.
7. a kind of switching system for electrical impedance tomography according to claim 6, is characterized in that, described multiselect one electric-controlled switch is 16 to select 1 electric-controlled switch.
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| CN103054578B (en) * | 2013-01-24 | 2015-04-01 | 四川大学 | Meridian point search tester |
| CN103228104B (en) * | 2013-02-27 | 2018-01-09 | 思澜科技（成都）有限公司 | The on-off circuit PCB of electrical impedance tomography serial data collection system multiselect 1 |
| CN105982671B (en) * | 2015-03-03 | 2020-07-07 | 思澜科技（成都）有限公司 | Optimized biological impedance test circuit |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101125080A (en) * | 2007-09-25 | 2008-02-20 | 重庆大学 | Increment magnifying type signal measuring device using for impedance imaging |
| GB2449275A (en) * | 2007-05-15 | 2008-11-19 | Thomas William Bach | Driving a sensor pad for electrical impedance tomography (EIT) |
| CN102274025A (en) * | 2011-05-30 | 2011-12-14 | 郑州大学 | Multi-electrode electrical impedance tomography data acquisition system |
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| JP5756132B2 (en) * | 2010-03-16 | 2015-07-29 | スイストム・アクチェンゲゼルシャフトＳｗｉｓｓｔｏｍ Ａｇ | Electrode for scanning electrical impedance tomography apparatus, and scanning electrical impedance tomography apparatus |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2449275A (en) * | 2007-05-15 | 2008-11-19 | Thomas William Bach | Driving a sensor pad for electrical impedance tomography (EIT) |
| CN101125080A (en) * | 2007-09-25 | 2008-02-20 | 重庆大学 | Increment magnifying type signal measuring device using for impedance imaging |
| CN102274025A (en) * | 2011-05-30 | 2011-12-14 | 郑州大学 | Multi-electrode electrical impedance tomography data acquisition system |
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