CN104161506A - Active non-contact capacitive type bio-electricity signal sensor and application thereof - Google Patents
Active non-contact capacitive type bio-electricity signal sensor and application thereof Download PDFInfo
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- CN104161506A CN104161506A CN201410208068.9A CN201410208068A CN104161506A CN 104161506 A CN104161506 A CN 104161506A CN 201410208068 A CN201410208068 A CN 201410208068A CN 104161506 A CN104161506 A CN 104161506A
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Abstract
The invention relates to an active non-contact capacitive type bio-electricity signal sensor. The sensor is characterized in that bio-electricity signals are introduced into an electrode in a capacity coupling mode and sent to a backward stage system through a pre-amplifier, a shielding layer and a high-pass filter, the backward stage system is a backward stage buffer, the bio-electricity signals are output through the backward stage buffer, and electrical signals of capacity coupling are introduced into an organism by means of a capacitor formed by skin and an electrode pad in a coupling mode and are conducted through the skin. The sensor has the advantages that the whole structure is ingeniously designed, and antijamming capability of a circuit is high; according to the technical scheme, the four basic requirements of high input impedance, a high common-mode rejection ratio, low noise and low drift and safety reliability are met; the non-contact capacitive type electrode can collect the bio-electricity signals without making contact with the surface of the organism, and the sensor is suitable for users with sensitive skin or special symptoms.
Description
Technical field
The present invention relates to bioelectrical signals sensor, specifically a kind of active non-contact capacitive formula bioelectrical signals sensor and application thereof, belong to auxiliary medical equipment technical field.
Background technology
Along with the raising of scientific and technical development and people's living standard, bioelectrical signals measuring technique is developed fast in medical electronics research field and daily portable use field.In biological signal measuring, electrode is first extremely important element, because it is being undertaken, the bioelectrical signals that relies on ionic conduction in human body is converted to the effect that relies on the signal of telecommunication of electron conduction in measuring circuit.In clinical treatment, using maximum is wet electrode.In laboratory or scientific research institution, what research and discussion were maximum is active or passive dry electrode and contactless electrode.
Traditional electrode is generally for designing under clinical condition or in the static situation of user.And the application of bioelectrical signals is under human motion state or severe electromagnetic environment often, therefore, telegraph circuit should possess the features such as anti-interference, noise is low, power consumption is lower, power supply is stable.For these requirements, following three difficult problems are mainly broken through in the later research of telegraph circuit: the capacity of resisting disturbance of (1) circuit; (2) the battery powered scheme of reliable, stable and low-power consumption; (3) can combine with rear class digital circuit easily.
Ag/AgCl wet electrode can collect that amplitude is normal, the obvious biopotential signal of various features, and what in clinical treatment, often use is this kind of electrode.And need in use to remove keratodermatitis and add extra conductive paste and fixation adhesive tape just can obtain good signal, thereby so both inconvenience is also uncomfortable, limited bioelectric range of application.The trouble that dry electrode and contactless electrode can be removed coating conductive paste from, the signal characteristic collecting is obvious, but is easily subject to external interference, and signal amplitude is slightly decay also.
What dry electrode was used is microneedle electrodes and finger electrode mostly, do not need at skin surface, to smear conductive paste before use, the bio signal collecting is more optimistic, the major defect of microneedle electrodes is that the occupation mode of its intrusive mood easily causes skin infection, and the major defect of finger electrode is that use is can allow user extremely uncomfortable to the constriction of skin.Therefore, a kind of new technical scheme of exigence solves the problems of the technologies described above.
Summary of the invention
The present invention is just for the technical problem existing in prior art, a kind of active non-contact capacitive formula bioelectrical signals sensor is provided, the designed non-contact capacitive formula electrode of the present invention does not contact organism skin surface and just can gather out bioelectric signal, has avoided the shortcoming of above-mentioned two kinds of electrodes.This device overall construction design is ingenious, the capacity of resisting disturbance of circuit, and signal is reliable, stable.
To achieve these goals, the technical solution used in the present invention is as follows, a kind of active non-contact capacitive formula bioelectrical signals sensor, it is characterized in that, electrode adopts capacity coupled mode to introduce bioelectrical signals, through preamplifier, screen layer, high pass filter send in after level system, described rear level system is rear class buffer, after rear class buffer, export, the described capacity coupled signal of telecommunication is the electric capacity that utilizes skin and electrode pad to form, and the signal of telecommunication that organism goes out by skin conductance is introduced in coupling.In the technical program, preamplifier has the characteristics such as low noise, low drift, then passes through high pass filter, and high pass filter filtering low-frequency disturbance reduces the personal error in measuring process, also can reduce the skew of baseline; Last signal is through rear class buffer, and the effect of buffer is to make output signal have enough large drive current.
What in the technical program, adopt is signal coupling mode, and the Capacitance Coupled that non-contact capacitance formula electrode covers copper coin sheet and skin surface formation by electrode surface is introduced organism electric potential signal.Wet electrode of the prior art needs directly to contact skin with dry electrode and just can get a desired effect, even and in the technical program non-contact capacitance type sensor skin and electrode have interval still can collect organism electric potential signal.When using sensor, allow some megohmite insulants to serve as capacitor dielectric, hair for example, clothes or air, and do not need special electrolyte.Contactless electrode can be equivalent to by a very little electric capacity, approximately 10pF coupled signal.
As a modification of the present invention, described screen layer is in the middle of the circuit layer of the printed circuit board (PCB) of electrode and electrode disk, to lay one deck screen layer.Can effectively stop the signal generation after source signal and processing to interfere with each other.
As a modification of the present invention, described high pass filter is set to single order RC filter circuit, and cut-off frequency is 0.65 Hz-0.75Hz.The cut-off frequency of high pass filter is in 0.7Hz left and right, and filtering low-frequency disturbance, reduces the personal error in measuring process, also can reduce the skew of baseline.
As a modification of the present invention, in described single order RC filter circuit, capacitor C is 220nF, and resistance R is 1M Ω.Can reduce the personal error in measuring process, also can reduce the skew of baseline.
As a modification of the present invention, described pre-amplification circuit adopts the precision amplifier LMP7702 of high cmrr and high input impedance.In order not allow interfering signal by amplifier saturation, amplifier is applied under low gain state.Therefore, pre-amplifier is set to a buffer.In order to obtain the output signal of high s/n ratio, the low-noise performance of amplifier is had to very high requirement, this precision amplifier LMP7702 can suppress external interference, and to make it be attenuated to the intrinsic noise of amplifier be the same order of magnitude.
As a modification of the present invention, the cut-off frequency of described high pass filter is 0.7Hz.The cut-off frequency of high pass filter is 0.7Hz, and filtering low-frequency disturbance to greatest extent reduces the personal error in measuring process, also can reduce the skew of baseline.
A kind of application of active non-contact capacitive formula bioelectrical signals sensor, it is characterized in that, the Capacitance Coupled that non-contact capacitance formula electrode covers copper coin sheet and skin surface formation by electrode surface is introduced organism electric potential signal, between skin and electrode, is provided with insulating barrier.This sensor in use can directly not touch skin, allow some megohmite insulant charging capacitor media, for example hair, clothes, air and do not need special electrolyte, noncontacting electrode can be equivalent to by a smaller electric capacity, is approximately 10pF coupled signal.Sensor described in this technical scheme does not need extra conductive paste, fixation adhesive tape, due to discord contact skin, more can not cause skin infection, therefore, this sensor in application very aspect, comfortable, signal stabilization, do not allow to be subject to external interference, and range of application is more extensive, for some special populations, for example autopath can use.
With respect to prior art, advantage of the present invention is as follows, and 1) overall construction design is ingenious, the capacity of resisting disturbance of circuit is strong; 2) three layers of distributed architecture of electrode printed circuit board in this technical scheme, be circuit layer and the middle one deck screen layer of laying of electrode disk of electrode printed circuit board, the effect of electrode circle lamella is to form plates capacitance coupling input bioelectrical signals with skin surface, then through screen layer, arrive circuit layer, circuit layer is used for laying preamplifier circuit and circuit of high pass filter, the object that screen layer is laid on electrode circle lamella and circuit layer is that this signal between two-layer of shielding disturbs, and screen layer also can have the effect of feedback with the plates capacitance of electrode circle lamella formation; 3) the technical program has met high input impedance, high cmrr, low noise and low drift and safe and reliable these four basic demands; 4) non-contact capacitive formula electrode does not need to contact organism surface and just can collect bioelectrical signals, is applicable to user sensitive skin or that have special condition of illness to use.
Accompanying drawing explanation
Fig. 1 is the workflow diagram of electrode of the present invention.
Fig. 2 is each layer of schematic diagram of electrode printed circuit board of the present invention.
Fig. 3 is electrode signal coupling schematic diagram of the present invention.
Fig. 4 is electrode topologies figure of the present invention.
Fig. 5 is circuit of high pass filter of the present invention.
Fig. 6 is electrode integral circuit diagram of the present invention.
The specific embodiment
In order to deepen the understanding of the present invention and understanding, below in conjunction with accompanying drawing, the invention will be further described and introduction.
Embodiment 1: referring to Fig. 1, Fig. 6, a kind of active non-contact capacitive formula bioelectrical signals sensor, electrode adopts capacity coupled mode to introduce bioelectrical signals, through preamplifier, screen layer, high pass filter send in after level system, described rear level system is rear class buffer, after rear class buffer, export, the described capacity coupled signal of telecommunication is the electric capacity that utilizes skin and electrode pad to form, and the signal of telecommunication that organism goes out by skin conductance is introduced in coupling.In the technical program, preamplifier has the characteristics such as low noise, low drift, then passes through high pass filter, and high pass filter filtering low-frequency disturbance reduces the personal error in measuring process, also can reduce the skew of baseline; Last signal is through rear class buffer, and the effect of buffer is to make output signal have enough large drive current.What in the technical program, adopt is signal coupling mode, and the Capacitance Coupled that non-contact capacitance formula electrode covers copper coin sheet and skin surface formation by electrode surface is introduced organism electric potential signal.Wet electrode of the prior art needs directly to contact skin with dry electrode and just can get a desired effect, even and in the technical program non-contact capacitance type sensor skin and electrode have interval still can collect organism electric potential signal.
Embodiment 2: referring to Fig. 3, as a modification of the present invention, described screen layer is in the middle of the circuit layer of the printed circuit board (PCB) of electrode and electrode disk, to lay one deck screen layer.Can effectively stop the signal generation after source signal and processing to interfere with each other.
Embodiment 3: referring to Fig. 5, Fig. 6, as a modification of the present invention, described high pass filter is set to single order RC filter circuit, and cut-off frequency is 0.65 Hz-0.75Hz.Be preferably 0.7 Hz, the cut-off frequency of high pass filter is in 0.7Hz left and right, and filtering low-frequency disturbance, reduces the personal error in measuring process, also can reduce the skew of baseline.
Embodiment 4: referring to Fig. 5, Fig. 6, as a modification of the present invention, in described single order RC filter circuit, capacitor C is 220nF, and resistance R is 1M Ω.Can reduce the personal error in measuring process, also can reduce the skew of baseline.
Embodiment 5: referring to Fig. 6, as a modification of the present invention, described pre-amplification circuit adopts the precision amplifier LMP7702 of high cmrr and high input impedance.In order not allow interfering signal by amplifier saturation, amplifier is applied under low gain state.Therefore, pre-amplifier is set to a buffer.In order to obtain the output signal of high s/n ratio, the low-noise performance of amplifier is had to very high requirement; This precision amplifier LMP7702 can suppress external interference, and to make it be attenuated to the intrinsic noise of amplifier be the same order of magnitude.
Embodiment 6: referring to Fig. 6, a kind of application of active non-contact capacitive formula bioelectrical signals sensor, the Capacitance Coupled that non-contact capacitance formula electrode covers copper coin sheet and skin surface formation by electrode surface is introduced organism electric potential signal, between skin and electrode, is provided with insulating barrier.This sensor in use can directly not touch skin, allow some megohmite insulant charging capacitor media, for example hair, clothes, air and do not need special electrolyte, noncontacting electrode can be equivalent to by a smaller electric capacity, be approximately 10pF coupled signal, as shown in Figure 3.Sensor described in this technical scheme does not need extra conductive paste, fixation adhesive tape, due to discord contact skin, more can not cause skin infection, therefore, this sensor in application very aspect, comfortable, signal stabilization, do not allow to be subject to external interference, and range of application is more extensive, for some special populations, for example autopath can use.According to this characteristic of contactless electrode, design its circuit model, referring to Fig. 4, amplifier has larger input impedance, circuit model is equivalent to the electromotive force that impedance between amplifier input impedance series connection electrode and skin forms the body signal that bleeder circuit comes minute, the electric capacity that two pole plates of the screen layer of designing and electrode disk form can not be ignored, and its electrical schematic diagram is shown in Fig. 5.As shown in Figure 4, it simplifies circuit as shown in Figure 5 to the circuit topology figure that the three-decker of electrode printed circuit board forms, and the parameters in Fig. 4 and Fig. 5 is:
skin surface signal source,
the coupling admittance of skin-electrode,
amplifier input admittance,
screen layer-interelectrode capacitance,
amplifier gain,
it is amplifier output signal.
The source signal of electrode to the gain of output signal is:
(formula 1-1)
Select the front-end amplifier first order to make buffer,
(formula 1-2)
So the source signal of electrode becomes to the gain of output signal:
(formula 1-3)
With respect to amplitude, only for the low frequency bioelectrical signals of microvolt, the millivolt order of magnitude, low noise, low drift are the basic demands of preamplifier.The high-impedance behavior of organism skin just can be brought appreciable thermal noise, input signal second-rate.So, in order to obtain the output signal of high s/n ratio, the low-noise performance of amplifier is had to very high requirement.Desirable preamplifier, can suppressing external interference, to make it be attenuated to the intrinsic noise of amplifier be the same order of magnitude.Therefore described pre-amplification circuit adopts the precision amplifier LMP7702 of high cmrr and high input impedance.In order not allow interfering signal by amplifier saturation, amplifier is applied under low gain state, and pre-amplifier is set to a buffer.Whole sensor comprises prebuffer, high pass filter and the output of rear class buffer, has met high input impedance, high cmrr, low noise and low drift and safe and reliable these four basic demands.
The present invention can also be combined to form new embodiment by least one and embodiment 1 in technical characterictic described in embodiment 2,3,4,5.
It should be noted that above-described embodiment, be not used for limiting protection scope of the present invention, the equivalents of having done on the basis of technique scheme or substitute and all to fall into the scope that the claims in the present invention are protected.
Claims (7)
1. an active non-contact capacitive formula bioelectrical signals sensor, it is characterized in that, electrode adopts capacity coupled mode to introduce bioelectrical signals, through preamplifier, screen layer, high pass filter send in after level system, described rear level system is rear class buffer, after rear class buffer, export, the described capacity coupled signal of telecommunication is the electric capacity that utilizes skin and electrode pad to form, and the signal of telecommunication that organism goes out by skin conductance is introduced in coupling.
2. a kind of active non-contact capacitive formula bioelectrical signals sensor according to claim 1, is characterized in that, described screen layer is in the middle of the circuit layer of the printed circuit board (PCB) of electrode and electrode disk, to lay one deck screen layer.
3. a kind of active non-contact capacitive formula bioelectrical signals sensor according to claim 1 and 2, is characterized in that, described high pass filter is set to single order RC filter circuit, and cut-off frequency is 0.65 Hz-0.75Hz.
4. a kind of active non-contact capacitive formula bioelectrical signals sensor according to claim 3, is characterized in that, in described single order RC filter circuit, capacitor C is 220nF, and resistance R is 1M Ω.
5. a kind of active non-contact capacitive formula bioelectrical signals sensor according to claim 1 and 2, is characterized in that, described pre-amplification circuit adopts the precision amplifier LMP7702 of high cmrr and high input impedance.
6. a kind of active non-contact capacitive formula bioelectrical signals sensor according to claim 4, is characterized in that, the cut-off frequency of described high pass filter is 0.7Hz.
7. the application of an active non-contact capacitive formula bioelectrical signals sensor, it is characterized in that, the Capacitance Coupled that non-contact capacitance formula electrode covers copper coin sheet and skin surface formation by electrode surface is introduced organism electric potential signal, between skin and electrode, is provided with insulating barrier.
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Application publication date: 20141126 |