CN101194834A - Bio-electrical impedance measuring method and apparatus - Google Patents

Abstract

The invention discloses a measuring method of biological electric impedance, which is characterized in that the method comprises constant-current outputting the sine wave pumping signal with preset frequency to the measuring electrode which is arranged in a region for measuring, inspiring the region for measuring, receiving and magnifying the analog signal which passes through the region for measuring, A/D converting the analog signal, extracting a plurality of digital signals in one cycle of A/D conversion, calculating a group of impedance values corresponding to a plurality of digital signals through the fast Fourier algorithm, calculating the impedance values of different frequency points in the range of preset frequency through repeating above steps to form an impedance frequency diagram, and calculating the characteristic parameter of the region for measuring at the time point through coincidence circularity method according to the impedance frequency diagram. The invention provides pure electrical signal through effectively shielding inference signal, thereby guaranteeing the measurement precision. The invention adopts the fast Fourier algorithm and coincidence circularity method, which improves the precision of impedance calculation and effectively reduces the cost of circuit.

Description

A kind of bio-electrical impedance measuring method and measuring device

Technical field

The present invention relates to the bio-electrical impedance detection range, particularly relate to a kind of method and device of bio-electrical impedance measuring.

Background technology

Bio-electrical impedance measuring is that a kind of electrical characteristics of utilizing biological tissue and organ and Changing Pattern thereof extract the detection technique with physiology, biomedical information that pathological condition is relevant, employing bio-electrical impedance measuring method can noinvasive, highly sensitive, extract corresponding electrical characteristics and change information thereof exactly.Can be used for measurement and supervision to the various electric parameters of biology, for example electrocardiography, biological impedance, electroencephalogram art or the like are included in and place electrode on the organism, measure the signal of telecommunication then during electricity irritation is carried out or in the later time.

Concerning organism, because the similarities and differences of density, intercellular substance and the permeability of cell membrane of cell category, arrangement, different tissues, the impedance operator that different directions and state showed of homologue all might be different even; On the other hand because the physiology of tissue or the pathological change permeability that will inevitably have influence on cell membrane and the variations such as electrolysis concentration of intercellular substance, thereby influence the frequency characteristic energy of its tissue.The ultimate principle of impedance imaging is by being injected alternating current by the electrode around the imageable target, and the borderline voltage of synchro measure, the many drive electrodes of employing and measurement electrode structure realize the measurement of four electrode impedances, utilize image reconstruction method that the transforming impedance data that the phase sensitivity conditioning technology obtains are reconstructed, form the impedance faultage image.

The physiological function that the characteristic that obtains by bio-electrical impedance measuring can be used for detecting some bio-tissue changes the variation of the tissue impedance that causes, for example, tissue hyperemia and discharge etc., or the variation of the tissue impedance that causes of some histo pathological change, for example canceration etc., (electricalimpedance tomography EIT) embodies in the image, can offer the related personnel and be used for pathology detection, judgement and other purposes at electrical impedance tomography with these information.This technology noinvasive is harmless, measures easyly, is being with a wide range of applications for the secular image of patient monitoring this respect, and these are that present most clinical imaging means are difficult to accomplish; These characteristics that technology cost is low, expense is low also are fit to carry out medical treatment generaI investigation widely very much simultaneously.

The prior biological impedometer mostly adopts simple Resistance model for prediction, and for example the noinvasive impedance method output gauge of clinical employing etc. uses limitation big, can only be used for the human body specific part.Biological tissue's multi-frequency impedance gauge does not also have the practicability instrument at present.It is existing in addition that to be in the instrument design scheme of development experimental stage complicated, performance is simple, and the algorithm of employing and the function of realization are very simple, the cost height, and do not possess impedance model parameter extraction analytic function, for a long time detection in vivo organism impedance model parameter etc.

In addition, measure the hardware components that adopts and in measuring process, can produce the sum of errors interference, as: the surface potential signal errors that the contact resistance that attachment of electrodes causes produces, the interfering signal that produces when various instruments are worked etc., can causing carrying out electrical impedance, to calculate the signal of telecommunication degree of purity that is utilized not enough, promptly can not accurately reflect the distribution of impedance in zone to be measured, cause the undesirable of imaging precision, can't be accurately change of illness state in the antimer truly.

Summary of the invention

Technical problem to be solved by this invention provides a kind of bio-electrical impedance measuring method, so that when measuring, can remove the interfering signal of measured signal, for calculating, bio-electrical impedance provides purified signal, adopt simple, high speed algorithm to obtain the higher bio-electrical impedance characteristic parameter of precision, thereby obtain accurate image information.

Another object of the present invention is that above-mentioned design is applied in the concrete clinical practice environment, a kind of bio-electrical impedance measuring apparatus is provided, use this device can obtain the higher bio-electrical impedance characteristic parameter of precision, and accurately image, offer doctor or related personnel and show, thereby guarantee that this method is in clinical realization and application.

For solving the problems of the technologies described above, the invention provides a kind of bio-electrical impedance measuring method, described method comprises step:

The sine wave exciting signal of constant current output predeterminated frequency encourages zone to be measured to the measurement electrode that is arranged on zone to be measured;

Obtain and amplify the analogue signal in process zone to be measured;

Described analogue signal is carried out analog-to-digital conversion;

In an analog-to-digital conversion cycle, extract a plurality of digital signals, and calculate one group of resistance value of described a plurality of digital signal correspondences by the Fourier fast transform algorithm;

Repeat above-mentioned steps and calculate the resistance value of different frequency point in the predeterminated frequency scope, form impedance frequency figure;

Calculate the characteristic parameter in this described zone to be measured of time point according to described impedance frequency figure by the method for match circle.

Preferably, the scope of described predeterminated frequency is 1hz-300khz.

Preferably, in an analog-to-digital conversion cycle, extract 2000 digital signals at least.

Preferably, described method also comprises step: obtain the characteristic parameter in described zone to be measured at times, form the characteristic parameter trendgram.

Preferably, described method also comprises step: described analogue signal is carried out the pressure-limit current-limit pretreatment obtaining and amplifying through before the analogue signal in zone to be measured;

The pretreated method of described pressure-limit current-limit is specially: detect the current value and the magnitude of voltage of described analogue signal respectively, when detecting described current value or magnitude of voltage and exceed predetermined threshold value, disconnect and connecting.

Preferably, the described analogue signal step of obtaining and amplifying through zone to be measured comprises:

Standard sample resistance on the series circuit in the first high impedance amplifier and described zone to be measured is arranged in parallel, obtaining the current signal on the described regional series circuit to be measured, the impedance of described high impedance amplifier be at least described sample resistance impedance 10 ⁶Doubly;

The second high impedance amplifier is linked to each other with second measurement electrode with first measurement electrode that is arranged on described regional both sides to be measured, to obtain the voltage signal in described zone to be measured.

Preferably, described method is after carrying out analog-to-digital conversion with described analogue signal, also comprise step: when described numerical value through current signal after the analog-to-digital conversion and voltage signal is not within preset range, adjust the described first high impedance amplifier and the second high resistant Amplifier Gain.

Preferably, described resistance value comprises real part and imaginary part; Described characteristic parameter comprises characteristic frequency and characteristic impedance.

Preferably, described zone to be measured is the human body brain, and described trendgram is cerebral edema state trend figure.

Preferably, the scope of described predeterminated frequency is 10hz-100khz.

Preferably, described measurement electrode comprises adherent base bottom, conductive adhesive layer, clasp and laying; Described conductive adhesive layer, adherent base bottom are connected successively with laying, and described clasp is eccentric design, and described conductive adhesive layer is the cylinder bodily form, and described clasp is electrically connected with described conductive adhesive layer; Acrylic acid content is 5% in the electroconductive binder of described measurement electrode, and the diameter of conductive adhesive layer is 18mm, adheres to zone to be measured fully.

The invention also discloses a kind of bio-electrical impedance measuring apparatus, described device comprises:

Exciting unit, the sine wave exciting signal that is used for constant current output predeterminated frequency encourages zone to be measured to the measurement electrode that is arranged on zone to be measured;

High impedance amplifier is used to obtain and amplify the analogue signal of passing through zone to be measured;

The analog-to-digital conversion unit is used for described analogue signal is carried out analog-to-digital conversion;

The fast Flourier processing unit was used for extracting a plurality of digital signals in an analog-to-digital conversion cycle, and calculated one group of resistance value of described a plurality of digital signal correspondences by the Fourier fast transform algorithm;

The legend unit is used for the resistance value that the repetition above-mentioned steps is calculated different frequency in the predeterminated frequency point range, forms impedance frequency figure;

Computing unit is used for calculating the characteristic parameter in this described zone to be measured of time point according to described impedance frequency figure by the method for match circle.

Preferably, the scope of described exciting unit predeterminated frequency is 1hz-300khz.

Preferably, in an analog-to-digital conversion cycle, extract 2000 digital signals at least.

Preferably, described device also comprises:

Trendgram forms the unit, obtains the characteristic parameter in described zone to be measured at times, forms the characteristic parameter trendgram.

Preferably, described device also comprises:

Pretreatment unit is used for carrying out power-off protection when the numerical value that detects described current signal and voltage signal during greater than predetermined threshold value.

Preferably, described high impedance amplifier comprises:

The first high impedance amplifier comprises two inputs and an outfan, and described two inputs link to each other with the two ends of described sample resistance respectively, is used to obtain and amplify the current signal of the described standard sample resistance of process;

The second high impedance amplifier comprises two inputs and an outfan, and described two inputs link to each other with second test electrode with first test electrode that is arranged on regional both sides to be measured respectively, are used to obtain and amplify the voltage signal of described regional both sides to be measured;

Preferably, the input impedance of the described first high impedance amplifier and the second high impedance amplifier is at least 10 ⁹Ohm.

Preferably, described device also comprises:

Gain adjustment unit links to each other with described high impedance amplifier, is used for adjusting the described first high impedance amplifier and the second high resistant Amplifier Gain when described numerical value through current signal after the analog-to-digital conversion and voltage signal is not within preset range.

Compared with prior art, the present invention has the following advantages:

1, by high impedance amplifier and gain-adjusted are set, adopt the Fourier fast transform algorithm that current signal and voltage signal are carried out filtration treatment, DC component, high-frequency/low-frequency noise and other interfering signal have effectively been shielded, for the calculating of last bio-electrical impedance provides purified signal;

2, calculate one group of resistance value of a plurality of digital signal correspondences on the frequency by the Fourier fast transform algorithm, certainty of measurement is higher, and error is little, and effectively reduces circuit cost;

3, adopt the bio-electrical impedance electrode special, effectively avoided hardware error, reduced contact impedance, further guaranteed the precision of measuring;

4, the method by the match circle obtains characteristic parameter, and algorithm is simple, and the result is accurate;

5, by different frequencies and parameter are set, the present invention goes for the monitoring at any position of organism.

Description of drawings

Fig. 1 is the flow chart of a kind of bio-electrical impedance measuring method of the present invention;

Fig. 2 is the circuit structure diagram that the present invention obtained and amplified described analogue signal;

Fig. 3 is the structure chart of the measurement electrode used of the present invention;

Fig. 4 is the flow chart that an embodiment of the present invention is measured the characteristic parameter of cerebral edema;

Fig. 5 is the sketch map that forms impedance frequency figure in an embodiment of the present invention;

Fig. 6 is that the present invention adopts the method for match circle to carry out the sketch map of calculation of characteristic parameters;

Fig. 7 is the sketch map that forms the characteristic parameter trendgram among a kind of embodiment of the present invention;

Fig. 8 is a kind of embodiment of the present invention by injecting different volumes, different types of test solution impedance characteristic parameter changing condition sketch map to the biological tissue;

Fig. 9 is the structure chart of a kind of bio-electrical impedance measuring of the present invention system.

The specific embodiment

For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, the present invention is further detailed explanation below in conjunction with the drawings and specific embodiments.

With reference to Fig. 1, be the flow chart of a kind of bio-electrical impedance measuring method of the present invention, may further comprise the steps:

Step 101: the sine wave exciting signal of constant current output predeterminated frequency encourages zone to be measured to the measurement electrode that is arranged on zone to be measured;

Step 102: the analogue signal of obtaining and amplifying process zone to be measured;

Step 103: described analogue signal is carried out analog-to-digital conversion;

Step 104: in an analog-to-digital conversion cycle, extract a plurality of digital signals, and calculate one group of resistance value of described a plurality of digital signal correspondences by the Fourier fast transform algorithm;

Step 105: repeat the resistance value that above-mentioned steps is calculated different frequency point in the predeterminated frequency scope, form impedance frequency figure;

Step 106: calculate the characteristic parameter in this described zone to be measured of time point by the method for match circle according to described impedance frequency figure.

In order to prevent in measuring process, the phenomenon that is short-circuited causes electric current excessive and cause human body to come to harm, or each hardware device that participates in measuring is damaged, obtaining and amplifying through before the analogue signal in zone to be measured, the present invention can also comprise step 107: described analogue signal is carried out the pressure-limit current-limit pretreatment.Preferably, the pretreated method of described pressure-limit current-limit is:

Detect the current value and the magnitude of voltage of described analogue signal respectively, when detecting described current value or magnitude of voltage and exceed predetermined threshold value, disconnect and connecting.Wherein, described predetermined threshold value can be provided with according to the safe voltage of human body or the ability to bear standard of current standard and each hardware device.

Preferably, the present invention adopts DDS technology constant current sine wave output pumping signal.The operation principle of DDS is actually a reference clock carries out controlled interval to phase place sampling.Reference clock generally is the crystal oscillator of a high stable, and its output signal is used for each parts synchronous working of DDS.Phase accumulator is the core that realizes DDS, and it adds up once at each rising edge clock and frequency control word k, and when accumulator count during greater than (L is a L LSB phase value of phase accumulator), phase accumulator is equivalent to do the surplus computing of one-off pattern.Sine look up table is in each clock cycle, according to having stored and the corresponding sinusoidal magnitude value in address among the address of giving ROM (m of phase accumulator MSB phase value) taking-up ROM, at last this value is given the conversion between DAC and LPF realization quantization amplitude to a purified sinusoidal signal.

Adopt the advantage of DDS to be: can direct convenience ground to produce optional frequency, frequency stability is good, conversion time is short, frequency resolution is high, the change amplitude is easy, flexible and convenient to use.Certainly, it also is feasible using the sine wave signal of other method constant current output predetermined frequency of the prior art, and those skilled in the art select to get final product as required, and the present invention does not need this to limit.

For fear of the too high high frequency that causes of frequency, and may form the emission of spatial electromagnetic signal, make the low inadequately situation of frequency low side, for example,, just might lose the useful information that low frequency signal may bring when frequency during greater than 1000Hz.In this case, the scope of predeterminated frequency is controlled between the 1hz-300khz can avoids this error as far as possible, thereby accurately obtain the analogue signal in zone to be measured.

In based on above-mentioned predeterminated frequency scope, obtain and the analogue signal step 102 of amplifying through zone to be measured can also comprise following substep:

Substep 1021: the standard sample resistance on the series circuit in the first high impedance amplifier and described zone to be measured is arranged in parallel, obtaining the current signal on the described regional series circuit to be measured, the impedance of described high impedance amplifier be at least described sample resistance impedance 10 ⁶Doubly;

Substep 1022: the second high impedance amplifier is linked to each other with second measurement electrode with first measurement electrode that is arranged on described regional both sides to be measured, to obtain the voltage signal in described zone to be measured.

For making those skilled in the art understand the present invention better,, the present invention is obtained and the principle of amplifying described analogue signal is elaborated below with reference to Fig. 2.

With reference to figure 2, signal source 01 is used to produce the sinusoidal wave swept frequency excitation signal that frequency is 1hz-300khz, and the described pumping signal of constant output encourages zone to be measured to zone to be measured; In this process, pumping signal arrives the 3rd measurement electrode 03 through the standard sample resistance; First measurement electrode 04, second measurement electrode 05 are arranged at the both sides in zone to be measured; The input 071 of the first high impedance amplifier 07, input 072 link to each other with the two ends of described standard sample resistance respectively, and the input 081 of the second high impedance amplifier 08, input 082 link to each other with second measurement electrode 05 with first measurement electrode 04 respectively; Described first measurement electrode 04, second measurement electrode 05, the 3rd measurement electrode 03 and the power ground utmost point 06 contact with zone to be measured and produce contact resistance 031, contact resistance 041, contact resistance 051 and contact resistance 061.

The input impedance of the described first high impedance amplifier, the second high impedance amplifier is all 10 ⁹More than ohm, and the impedance order of magnitude of standard sample resistance 02, contact resistance 041, contact resistance 051 and contact resistance 061 all is ohm level, is 10～10 ³Ohm, and described standard sample resistance 02 is arranged on the polyphone circuit in zone to be measured; Therefore, signal source 01 constant current carries the sine-wave current signal of coming all by all entering zone to be measured by contact resistance 031 behind the described standard sample resistance 02, there is electric current hardly on contact resistance 041 and the contact resistance 051, promptly produces pressure drop hardly; And then, the first high impedance amplifier 07 can accurately obtain current signal on the standard sample resistance 02 and that is to say the current value surveyed on to be measured regional 10 and it is amplified according to default amplification that the second high impedance amplifier 08 can accurately obtain described regional 10 magnitude of voltage to be measured and it is amplified according to default amplification.

In this case, the described first high impedance amplifier 200 and the second high impedance amplifier 300 can obtain the purified analogue signal of reflection regional impedance 10 to be measured, and be so-called pure, promptly is that interfering signal is less; Reduce the error that contact resistance that measurement electrode produces causes signal thus, improved the impedance measurement precision.

The above the first high impedance amplifier and the second high impedance amplifier can be replaced by a high-impedance resistors and base amplifier, and the impedance of described high-impedance resistors can be 10 of the impedance of described standard sample resistance ⁷Doubly.

In measuring process, can produce the sum of errors interference for fear of measuring the hardware components that adopts, particularly because the surface potential signal errors that the contact resistance that attachment of electrodes causes produces, so measurement electrode used in the present invention is different from the electrocardioelectrode of using in the prior art, but a kind of electrode that is exclusively used in bio-electrical impedance measuring.

With reference to figure 3, be the structure chart of bio-electrical impedance measuring electrode used in the present invention, as can be seen, measurement electrode used in the present invention comprises adherent base bottom 301, conductive adhesive layer 302, clasp 303 and laying 304; Described conductive adhesive layer 302, adherent base bottom 301 and laying 304 are connected successively.Preferably, the area of described conductive adhesive layer 302, adherent base bottom 301 and laying 304 increases successively.

More preferably, the laying 304 of this measurement electrode covers the outer surface of described adherent base bottom 301, and exceeding the peripheral part of described adherent base bottom 301, this laying 304 also has the tacky adhesion face that contacts with skin viscosity, in order to strengthen the adhesion of electrode pair skin of the present invention.Because electrode is when adhering to skin, laying causes adhesion to reduce because of the excretory moisture of skin, and therefore laying 304 of the present invention is preferably non-woven fabrics.

And the inner surface of the adherent base bottom 301 of described measurement electrode connects conductive adhesive layer 302, and described conductive adhesive layer is as the electric interface between electrode and the skin, and the direct and contact skin of its outer surface is used to obtain the reflection current potential in zone to be measured.In order to guarantee the concordance of various piece electric conductivity on the conductive adhesive layer, it is this stable shaped that described conductive adhesive layer 302 is designed to the cylinder bodily form, thereby guarantee that the reflection current potential that gets access on the regional body surface contact surface to be measured by described conductive adhesive layer is accurate and stable.

In addition, the diameter of the conductive adhesive layer of described measurement electrode is preferably more than or equals 16mm, one preferably the result be that its diameter is 18mm.In this case, the present invention can obtain the higher bio-electrical impedance measuring value of accuracy.And, functional when acrylic acid content is 12%-18% in the described conductive adhesive layer 302, be performance the best of 15% o'clock conductive adhesive layer in acrylic acid content.

In clinical practice, for the reflection current potential that described conductive adhesive layer is obtained is transferred to the bio-electrical impedance measuring instrument, electrode need be linked to each other with the lead of gauge by clasp fetches realization, apparent, the connection of described clasp is electrically connected, and is used for the conduct electricity characteristic.In this case, the clasp 303 of described measurement electrode is made by conducting metal, be electrically connected with described conductive adhesive layer 302 by conductive layer 305, in order further to avoid because the measured body motion interference during to bio-electrical impedance measuring, described clasp 303 adopts eccentric design, center design compared to existing technology, the eccentric design of this kind can effectively improve the accuracy of measured value.

The measured value that uses measurement electrode of the present invention to obtain has higher accuracy with repeatable, for example, under the frequency of 40khz, the AC impedance value of described electrode is not more than 30 ohm, per two counter electrode between AC impedance value difference value for being not more than 3 ohm.

In order to realize the calculating of bio-electrical impedance, need with the current value of described each Frequency point through processing and amplifying and magnitude of voltage is parallel carry out analog-to-digital conversion, be digital signal by analog signal conversion.Be well known that analogue signal just becomes digital signal through over-sampling and two steps of quantification, sampling is meant that the signal sample sequence of using at regular intervals replaces successive in time originally signal, just in time with the analogue signal discretization; Quantification is with the approximate original continually varying range value of limited range value, the continuous amplitude of analogue signal is become the centrifugal pump that certain intervals is arranged of limited quantity.The frequency that it should be noted that described analog-to-digital conversion is the current value and the magnitude of voltage of the process processing and amplifying of 10hz for more than or equal to 2 times of the frequency of described Frequency point for frequency, and the frequency of described analog-to-digital conversion is at least 20hz.Form the multiple row signal thus, the corresponding Frequency point of every column signal.

Because corresponding different frequency, the corresponding different frequency of the impedance in zone to be measured must be different impedance, at the numerical value of low-frequency range and the numerical value of high band very big difference is arranged on scope, for example, there is very big difference certainly in impedance when impedance when frequency is 1hz and frequency are 300khz, may hundreds of ohm when high band, then may reach ohms up to ten thousand in low-frequency range, so big mobility scale can cause interference to signal measurement, therefore, the present invention also comprises step 108: when described numerical value through current signal after the analog-to-digital conversion and voltage signal is not within preset range, adjust the described first high impedance amplifier and the second high resistant Amplifier Gain.By the described first high impedance amplifier and the second high resistant Amplifier Gain (amplification) being divided into 8 gain shift such as 1,2,4,8,10,20,40,80, and the best scope of carrying out analog-to-digital conversion that draws according to test of many times, and empirical value (0.5 * range～0.8 * range is set in view of the above, described scope is to draw through test of many times according to the staff, be to carry out the best numerical range of analog-to-digital conversion), described range that is to say gain shift.

Extraction for digital signal in the analog-to-digital conversion cycle need be adjusted the time of analog-to-digital conversion according to different frequencies, guarantees that the point that once extracts can cover the plural constant current output signal cycle.Preferably, in an analog-to-digital conversion cycle, extract at least 2000 digital signals, in order to the precision of abundant assurance impedance bioelectrical measurement.

Described at least 2000 digital signals utilization Fourier fast transform algorithm is carried out spectrum analysis.Be specially, described a plurality of digital signals are resolved into discrete frequency component, obtain frequency spectrum profile, calculate the frequency spectrum of frequency-region signal, then f0+search voltage signal and current signal component on the Frequency point of ceiling capacity spectrum in/-10% scope, for example, corresponding output frequency is current value and the magnitude of voltage of f0, a window function can be set obtain the interior signal of [(f0-f010%)-(f0+f010%)] scope, can draw the mould value of AC impedance by the ratio that calculates two components.Need to prove, being chosen in the interior search signal of above-mentioned scope can also avoid power frequency to disturb, because if having power frequency disturbs, its energy intensity might be greater than the energy intensity at signal frequency place, if so in this scope, do not limit, system may detect work frequency as signal frequency, thereby produces error.

Simultaneously, in the Fourier Fast transforms, also drawn the phase contrast of described voltage signal and current signal, can on complex plane, calculate the resistance value of certain frequency, the i.e. real part of this frequency and imaginary part according to described mould value and phase contrast.In impedance frequency figure, described frequency, real part and imaginary part have just constituted a point on the frequency spectrum.Calculate the resistance value of the different frequency point in the predeterminated frequency scope according to the method described above, just can form impedance frequency figure.

In measurement in the past, the general virtual value that adopts detects voltage and current, thereby inevitably the voltage and current of other frequency is introduced virtual value, and in the voltage and current value that inevitably can produce other frequency range because of the hardware device in measuring process, because the current value of other frequency of these generations and the doping of magnitude of voltage, finally offer the unitary signal of the impedance computation signal of more than 1hz-300khz frequency range certainly, must cause the inaccurate of final calculation result.

In this case, can also adopt the Fourier Fast transforms measured waveform to be divided into the multiple harmonic of standard by the mode of software, form harmonic spectrum, and be greater than or less than the signal of telecommunication of predetermined threshold value according to the electrical signal energy value that output frequency and default energy threshold filter other frequency of deletion, the measured signal of real corresponding output frequency is extracted, improve the degree of purity of signal thus.

As from the foregoing, the present invention adopts the Fourier fast transform algorithm not only can carry out spectrum analysis, calculates resistance value, can also filtered electrical signal.

In actual applications, because measuring frequency is limited, must rely on algorithm to ask for the impedance model parameter of biological tissue according to the definite measured data.There is distinct disadvantage in existing algorithm, the anti-model of three Frequency point approximate calculation of usefulness blood resistivity that for example has, and the precision of this approximate calculation is low, and error is big.Adopt the characteristic parameter of least square circle fitting process extraction in vitro tissue model etc. in the prior art in addition, but this method exists iterations big, need through hundreds of or thousands of iterative computation, and fitting precision is not high, its initial value is chosen influences iteration convergence, causes arithmetic speed slow.The shortcoming of utilizing this algorithm to measure is that speed is slow, precision is low.

The present invention based on the above-mentioned impedance frequency figure that obtains, adopts the round method of match to propose the characteristic parameter in described zone to be measured at this, and wherein, described characteristic parameter is meant characteristic frequency and characteristic impedance.Hereinafter will be elaborated to this algorithm.

For the characteristic parameter that makes acquisition has the value of clinical judgment, method of the present invention can also comprise step 109: obtain the characteristic parameter in described zone to be measured at times, form the characteristic parameter trendgram.In clinical practice, can be by the patient at the characteristic frequency of different time points and the time dependent trendgram of characteristic impedance of characteristic impedance formation, with index as clinical evaluation.

Because cerebral edema is the pathological reaction of cerebral tissue to the different causes of disease, correct character and the evolution process of in time estimating cerebral edema be many critical patient's diagnosis of relation and treatment key of success, thereby a kind of application direction of the present invention is the monitoring to the cerebral edema state.In order to make those skilled in the art understand the present invention better, the present invention will be that example further specifies the present invention with the characteristic parameter to the measurement cerebral edema.

With reference to Fig. 4, one embodiment of the present invention are measured the flow chart of the characteristic parameter of cerebral edema, may further comprise the steps:

Step 401, in human body brain additional measure electrodes; Described measurement electrode is preferably above-mentioned bio-electrical impedance measuring electrode;

Step 402, constant current output frequency are extremely described electrode of the interior sine wave exciting signal of 10hz-100khz scope, and the human body brain is encouraged;

In the present embodiment, adopt the DDS technology to produce sine wave exciting signal, use the formula of this technique computes waveform to be:

I(t)＝0.1×Sin(2×π×f _i×t)

Need to prove, when carrying out the cerebral edema state observation, frequency is set in the scope of 10hz-100khz, can avoids high frequency error that can not lose the useful information that low frequency signal may bring again simultaneously, the characteristic parameter that is showed is most representative.

Step 403, detect the current value and the magnitude of voltage of analogue signal respectively,, disconnect connecting if detect described current value or magnitude of voltage exceeds predetermined threshold value.Otherwise, carry out step 404;

This step is in order to prevent in measuring process, the phenomenon that is short-circuited causes electric current excessive and cause human body to come to harm and each hardware device of participating in measuring is damaged, described predetermined threshold value is to be provided with according to the safe voltage of human body or the ability to bear standard of current standard and each hardware device, and ability technical staff is provided with voluntarily according to the detection demand and gets final product.

Step 404, the analogue signal of obtaining and amplifying process human body brain;

In order to obtain higher impedance measurement precision, the error of avoiding contact impedance to cause, this step is finished by following substep:

Substep 4041: utilize the first high impedance amplifier to obtain and amplify current signal on the standard sample resistance on the series circuit that is arranged on the human body brain, the impedance of described high impedance amplifier be at least described sample resistance impedance 10 ⁶Doubly;

Substep 4042: utilize the second high impedance amplifier to obtain and amplify the voltage signal of first measurement electrode and second measurement electrode of the both sides that are arranged on the human body brain.

As another embodiment, the above the first high impedance amplifier and the second high impedance amplifier can be replaced by a high-impedance resistors and base amplifier, and the impedance of described high-impedance resistors can be 10 of the impedance of described standard sample resistance ⁷Doubly.

Step 405 is carried out analog-to-digital conversion to described analogue signal;

With the current value of described each Frequency point through processing and amplifying with magnitude of voltage is parallel carries out analog-to-digital conversion, be digital signal by analog signal conversion.In order to obtain favorable linearity and high-resolution, the frequency of described analog-to-digital conversion is 2 times more than or equal to the frequency of described Frequency point, is the current value and the magnitude of voltage of the process processing and amplifying of 10hz for frequency, and the frequency of described analog-to-digital conversion is at least 20hz.

Step 406 judges whether the current value through analog-to-digital conversion is in the default scope (0.5 * range～0.8 * range), if not, enters step 410; Otherwise, enter step 407;

Step 407: adjust the described first high resistant amplifier magnification ratio gear;

In practice, can be as required the amplification (gain) of the described first high impedance amplifier be divided into 8 amplification gears such as 1,2,4,8,10,20,40,80, described range promptly is described amplification gear.

In order to ensure the current value that obtains at every turn all in default scope (0.5 * range～0.8 * range), described scope is to draw through test of many times according to the staff, be to carry out the best numerical range of analog-to-digital conversion, in the time of in current value is not in this scope, automatically adjust the gear of the amplification of the described first high impedance amplifier, make through the current value after its amplification to be in this scope.

Step 408: judge that whether the magnitude of voltage through analog-to-digital conversion is in the default scope (0.5 * range～0.8 * range), if not, enters step 410; Otherwise, enter step 409;

Step 409: adjust the described second high resistant amplifier magnification ratio gear.

Similarly, can be as required the amplification (gain) of the described second high impedance amplifier be divided into 8 amplification gears such as 1,2,4,8,10,20,40,80, described range promptly is described amplification gear.

In order to ensure the magnitude of voltage that obtains at every turn all in default scope (0.5 * range～0.8 * range), described scope is to draw through test of many times according to the staff, be to carry out the best numerical range of analog-to-digital conversion, in the time of in magnitude of voltage is not in this scope, automatically adjust the gear of the amplification of the described second high impedance amplifier, make through the magnitude of voltage after its amplification to be in this scope.

Step 410 is extracted at least 2000 digital signals in an analog-to-digital conversion cycle, and adopts the Fourier fast transform algorithm to calculate one group of resistance value of described digital signal correspondence;

The resistance value that obtains a plurality of frequencies of brain according to algorithm computation mentioned above is as shown in the table:

Step 411 according to the resistance value of a plurality of different frequency points in the last table, forms impedance frequency figure (the x direction of principal axis is a real part, and the y direction of principal axis is an imaginary part) as shown in Figure 5;

Step 412 with reference to figure 6, is calculated the cerebral edema characteristic parameter by the method for match circle;

The detailed process that described match circle calculates is:

$Z=R_s+\frac{1}{{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{j\&omega;}\right)}^n+\frac{1}{R_p}}$

$=R_s+\frac{\frac{1}{R_p}+{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\cos \frac{\mathrm{n\&pi;}}{2}-j{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\sin \frac{\mathrm{n\&pi;}}{2}}{\frac{1}{{{\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="A20061016108400241.png,A20061016108400262.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}^2}+\frac{2}{R_p}{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\cos \frac{\mathrm{n\&pi;}}{2}+{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^{2n}}$

Wherein, Z represents complex impedance, is the represented plural number of Z among Fig. 4, the present invention utilize two plural numbers and formal representation, in the formula Rs and Rp represent the series connection and the parallel resistance resistance, n is an index, ω represents angular frequency.

$Z_{\mathrm{re}}=R_s+\frac{\frac{1}{R_p}+{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\cos \frac{\mathrm{n\&pi;}}{2}}{\frac{1}{{{\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="A20061016108400241.png,A20061016108400262.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}^2}+\frac{2}{R_p}{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\cos \frac{\mathrm{n\&pi;}}{2}+{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^{2n}}$

Wherein, Zre represents the real part of complex impedance Z, and Rs and Rp represent series connection and parallel resistance resistance in the formula, and n is an index, and ω represents angular frequency.

$Z_{\mathrm{im}}=\frac{{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\sin \frac{\mathrm{n\&pi;}}{2}}{\frac{1}{{{\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="A20061016108400241.png,A20061016108400262.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}^2}+\frac{2}{R_p}{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\cos \frac{\mathrm{n\&pi;}}{2}+{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^{2n}}$

Wherein, Z _ImExpression complex impedance Z imaginary part, Rs and Rp represent series connection and parallel resistance resistance in the formula, and n is an index, and ω represents angular frequency.

$\left|Z\right|=\sqrt{{R_s}^2+\frac{1+\frac{{2R}_s}{R_p}+{2R}_s{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\cos \frac{\mathrm{n\&pi;}}{2}}{\frac{1}{{{\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="A20061016108400241.png,A20061016108400262.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}^2}+\frac{2}{R_p}{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\cos \frac{\mathrm{n\&pi;}}{2}+{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^{2n}}}$

Wherein, | Z| represents the mould of complex impedance Z, and Rs and Rp represent series connection and parallel resistance resistance in the formula, and n is an index, and ω represents angular frequency.

$\tan \mathrm{\&phi;}=\frac{{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\sin \frac{\mathrm{n\&pi;}}{2}}{R_s(\frac{1}{{{\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="A20061016108400241.png,A20061016108400262.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}^2}+\frac{2}{R_p}{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\cos \frac{\mathrm{n\&pi;}}{2}+{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^{2n})+\frac{1}{R_p}+{\left({\mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="A20061016108400261.png,A20061016108400262.png"\; state="\{\{state\}\}">Y</figure-callout>}}_0\mathrm{\&omega;}\right)}^n\cos \frac{\mathrm{n\&pi;}}{2}}$

Wherein, tan φ represents the tangent value of the argument of plural Z, and Rs and Rp represent series connection and parallel resistance resistance in the formula, and n is an index, and ω represents angular frequency.Thus, can prove Z _ReAnd Z _ImSatisfy equation of a circle:

${(Z_{\mathrm{re}}-R_s-\frac{R_p}{2})}^2+{(Z_{\mathrm{im}}+\frac{R_p\cot \frac{\mathrm{n\&pi;}}{2}}{2})}^2={\left(\frac{{\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="A20061016108400241.png,A20061016108400262.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}{2\sin \frac{\mathrm{n\&pi;}}{2}}\right)}^2$

Wherein, Rs and Rp represent series connection and parallel resistance resistance, and n is an index.

The center of circle of this circle is

Radius is

Rs and Rp represent series connection and parallel resistance resistance, and n is an index.

Finally obtain:

$\left|Z\right|=\sqrt{{R_s}^2+R_s{R}_p+\frac{{{\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="A20061016108400241.png,A20061016108400262.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}^2}{4}{\mathrm{<figure-callout\; id="2"\; label="sec"\; filenames="A20061016108400241.png,A20061016108400262.png"\; state="\{\{state\}\}">sec</figure-callout>}}^2\frac{\mathrm{n\&pi;}}{4}}$

Wherein, | Z| represents the mould of complex impedance Z, is the result that actual needs obtains, and also can use Zre and Z _ImThe associating expression, Rs and Rp represent series connection and parallel resistance resistance, n is an index.

$\mathrm{\&phi;}=\arctan \left(\frac{R_p}{{2R}_s+R_p}\tan \frac{\mathrm{n\&pi;}}{4}\right)$

Wherein, φ represents the argument of plural Z, and Rs and Rp represent series connection and parallel resistance resistance, and n is an index.

$Z_{\mathrm{re}}=R_s+\frac{{\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="A20061016108400241.png,A20061016108400262.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}{2}$

Wherein, Zre represents the real part of complex impedance Z, and Rs and Rp represent series connection and parallel resistance resistance, and n is an index.

$Z_{\mathrm{im}}=\frac{{\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="A20061016108400241.png,A20061016108400262.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}{2}\tan \frac{\mathrm{n\&pi;}}{4}$

Wherein, Z _ImExpression complex impedance Z imaginary part, Rs and Rp represent series connection and parallel resistance resistance, n is an index.

This process is the solution procedure of a discrete data match equation of a circle from mathematical logic, can directly try to achieve characteristic parameter, i.e. characteristic frequency and characteristic impedance by said process.

Step 413 as shown in Figure 7, is obtained the cerebral edema characteristic parameter of a plurality of periods according to above-mentioned steps, forms cerebral edema state trend figure.

By measurement in different time points, calculate the frequency sweep data respectively and obtain characteristic frequency and characteristic impedance, and make the time dependent trendgram of characteristic impedance in view of the above, promptly can be used as the clinical index that can estimate.

Be clinical evaluation according to this with reference to the standard of judging as shown in Figure 8 for impedance characteristic parameter changing condition after different volumes, the different types of test solution injection biological tissue.Wherein, the lines of different colours are represented the volume of different sample edema/hematoma and the relation of impedance measurement characteristic parameter.

In clinical practice, based on Fig. 8 cerebral edema state shown in Figure 7 is analyzed, can obtain following conclusion:

Along with the volume increase of measurand cerebral edema, the comprehensive complex impedance liquid that calculates based on predeterminated frequency increases thereupon, and the two has the positive relation, can be used as the basic foundation of differentiation intracranial edema/hematoma changing condition;

By the multiple tracks metering system, can segment the measuring point, tentatively determine the position of cerebral edema.

Preferably, the present invention can also obtain result of calculation by embedded integrated computing system (WINCE), in display system, show intuitively and printout in output system, constitutes inexpensive, noinvasive, bed other, reflect the custodial care facility of cranium brain deep edema/hematoma differentiation situation continuously.

With reference to figure 8, be the structure chart of a kind of bio-electrical impedance measuring apparatus of the present invention, comprising:

Exciting unit 01, the sine wave exciting signal that is used for constant current output predeterminated frequency encourages zone to be measured to the measurement electrode that is arranged on zone to be measured;

High impedance amplifier 200,300 is used to obtain and amplify the analogue signal of passing through zone to be measured;

Analog-to-digital conversion unit 500 is used for described analogue signal is carried out analog-to-digital conversion;

Fast Flourier processing unit 400 was used for extracting a plurality of digital signals in an analog-to-digital conversion cycle, and calculated one group of resistance value of described a plurality of digital signal correspondences by the Fourier fast transform algorithm;

Legend unit 900 is used for the resistance value that the repetition above-mentioned steps is calculated different frequency in the predeterminated frequency scope, forms impedance frequency figure;

Computing unit 600 is used for calculating the characteristic parameter in described zone to be measured according to described impedance frequency figure by the method for match circle.

Preferably, device of the present invention can also comprise that trendgram forms unit 901, is used for obtaining at times the characteristic parameter in described zone to be measured, forms the characteristic parameter trendgram.

Preferably, device of the present invention can also comprise pretreatment unit 800, is used for carrying out power-off protection when the numerical value that detects described current signal and voltage signal during greater than predetermined threshold value.

Preferably, described high impedance amplifier comprises:

The first high impedance amplifier 200 comprises 211,212 and outfans 213 of two inputs, and described two inputs 211,212 link to each other with the two ends of described sample resistance 100 respectively, is used to obtain and amplify the current signal of the described standard sample resistance of process;

The second high impedance amplifier 300, comprise 311,312 and outfans 313 of two inputs, described two inputs 311,312 link to each other with second test electrode 05 with first test electrode 04 that is arranged on regional both sides to be measured respectively, are used to obtain and amplify the voltage signal of described regional both sides to be measured.

The input impedance of the described first high impedance amplifier 200 and the second high impedance amplifier 300 is at least 10 ⁹Ohm.

Preferably, device of the present invention can also comprise:

Gain adjustment unit 700, link to each other with described high impedance amplifier 200,300, be used for when described numerical value through current signal after the analog-to-digital conversion and voltage signal is not within preset range, adjusting the gain of the described first high impedance amplifier 200 and the second high impedance amplifier 300.

For the not detailed part of the description of Fig. 8, can be referring to the aforementioned relevant portion of this description.

More than to a kind of bio-electrical impedance measuring method provided by the present invention and device, be described in detail, used specific case herein principle of the present invention and embodiment are set forth, the explanation of above embodiment just is used for helping to understand method of the present invention and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present invention, the part that all can change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.

Claims (13)

1. a bio-electrical impedance measuring method is characterized in that, described method comprises:

The sine wave exciting signal of constant current output predeterminated frequency encourages zone to be measured to the measurement electrode that is arranged on zone to be measured;

Obtain and amplify the analogue signal in process zone to be measured;

Described analogue signal is carried out analog-to-digital conversion;

In an analog-to-digital conversion cycle, extract a plurality of digital signals, and calculate one group of resistance value of described a plurality of digital signal correspondences by the Fourier fast transform algorithm;

Repeat above-mentioned steps and calculate the resistance value of different frequency point in the predeterminated frequency scope, form impedance frequency figure;

Calculate the characteristic parameter in this described zone to be measured of time point according to described impedance frequency figure by the method for match circle.

2. the method for claim 1 is characterized in that, the scope of described predeterminated frequency is 1hz-300khz.

3. the method for claim 1 is characterized in that, extracts 2000 digital signals in an analog-to-digital conversion cycle at least.

4. as claim 1,2 or 3 described methods, it is characterized in that, also comprise:

Obtain the characteristic parameter in described zone to be measured at times, form the characteristic parameter trendgram.

5. the method for claim 1 is characterized in that, the described analogue signal step of obtaining and amplifying through zone to be measured comprises:

Standard sample resistance on the series circuit in the first high impedance amplifier and described zone to be measured is arranged in parallel, obtaining the current signal on the described regional series circuit to be measured, the impedance of described high impedance amplifier be at least described sample resistance impedance 10 ⁶Doubly;

The second high impedance amplifier is linked to each other with second measurement electrode with first measurement electrode that is arranged on described regional both sides to be measured, to obtain the voltage signal in described zone to be measured.

6. the method for claim 1 is characterized in that, described resistance value comprises real part and imaginary part; Described characteristic parameter comprises characteristic frequency and characteristic impedance; Described zone to be measured is the human body brain; Described characteristic parameter trendgram is cerebral edema state trend figure.

7. method as claimed in claim 6 is characterized in that, the scope of described predeterminated frequency is 10hz-100khz.

8. described measurement electrode comprises adherent base bottom, conductive adhesive layer, clasp and laying; Described conductive adhesive layer, adherent base bottom are connected successively with laying, and described clasp is eccentric design, and described conductive adhesive layer is the cylinder bodily form, and described clasp is electrically connected with described conductive adhesive layer; Acrylic acid content is 5% in the electroconductive binder of described measurement electrode, and the diameter of conductive adhesive layer is 18mm, adheres to the tested position of human body fully.

9. a bio-electrical impedance measuring apparatus is characterized in that, comprising:

Exciting unit, the sine wave exciting signal that is used for constant current output predeterminated frequency encourages zone to be measured to the measurement electrode that is arranged on zone to be measured;

High impedance amplifier is used to obtain and amplify the analogue signal of passing through zone to be measured;

The analog-to-digital conversion unit is used for described analogue signal is carried out analog-to-digital conversion;

The fast Flourier processing unit was used for extracting a plurality of digital signals in an analog-to-digital conversion cycle, and calculated one group of resistance value of described a plurality of digital signal correspondences by the Fourier fast transform algorithm;

The legend unit is used for the resistance value that the repetition above-mentioned steps is calculated different frequency in the predeterminated frequency point range, forms impedance frequency figure;

Computing unit is used for calculating the characteristic parameter in this described zone to be measured of time point according to described impedance frequency figure by the method for match circle.

10. device as claimed in claim 9 is characterized in that, the scope of described exciting unit predeterminated frequency is 1hz-300khz.

11. device as claimed in claim 9 is characterized in that, extracts 2000 digital signals in an analog-to-digital conversion cycle at least.

12. as claim 9,10 or 11 described devices, it is characterized in that, also comprise:

Trendgram forms the unit, obtains the characteristic parameter in described zone to be measured at times, forms the characteristic parameter trendgram.

13. device as claimed in claim 9 is characterized in that, described high impedance amplifier comprises:

The first high impedance amplifier comprises two inputs and an outfan, and described two inputs link to each other with the two ends of described sample resistance respectively, is used to obtain and amplify the current signal of the described standard sample resistance of process;

The second high impedance amplifier, comprise two inputs and an outfan, described two inputs link to each other with second test electrode with first test electrode that is arranged on both sides, the tested position of human body respectively, are used to obtain and amplify the voltage signal of both sides, the tested position of described human body;

The input impedance of the described first high impedance amplifier and the second high impedance amplifier is at least 10 ⁹Ohm.

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