CN106725474A - A kind of human body impedance detection method - Google Patents
A kind of human body impedance detection method Download PDFInfo
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- CN106725474A CN106725474A CN201710127392.1A CN201710127392A CN106725474A CN 106725474 A CN106725474 A CN 106725474A CN 201710127392 A CN201710127392 A CN 201710127392A CN 106725474 A CN106725474 A CN 106725474A
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/053—Measuring electrical impedance or conductance of a portion of the body
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2560/00—Constructional details of operational features of apparatus; Accessories for medical measuring apparatus
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Abstract
A kind of detection method of human body impedance, step includes, (1) test system building, and (2), based on normal impedance calibration system, (3) carry out human body impedance test, it is characterized in that：When (1st) step builds system, using as far as possible small outside output impedance R0, it is similar to using constant pressure source forcing, to ensure as far as possible big operating current；In (2nd) step system calibration, in measurement range, system is demarcated using enough normal impedance samples, i.e., to each normal impedance sample, its corresponding voltage value under given excitation is measured, the one-to-one relationship between impedance and test voltage is set up in finally fitting.
Description
Technical field
The application is related to a kind of human body impedance detection method.
Human body impedance is the important physiological parameter of human body, and its detection has highly important meaning in biomedical sector
Justice.Such as, domestic and foreign scholars just find that the impedance variations of human body and breathing have close relationship very early.If human body impedance letter
One resistance of chemical conversion, according to resistance formula R=ρ L/A, when human body respiration, thorax changing, internal gas flow and into
Divide and also changing, this is all changing equivalent to human body resistance rate ρ and L/A in change, that is, human body resistance.Therefore, using electricity
The change that drive test goes out human body impedance also just reflects the breathing situation of human body indirectly.Human body impedance detection is the inspection of human body respiration signal
One of important means of survey, is widely applied in ECG monitor.
Background technology
Human body impedance includes reactance, induction reactance and capacitive reactance.The induction reactance of human body is very small, can generally ignore not
Meter.The capacitive reactance of human body is very sensitive for frequency, based on capacitive reactance formula XC=1/2 π fc understand that capacitive reactance is proportional to frequency l/f
Relation, when frequency increases, capacitive reactance is in reduction trend.Obviously, the impedance of a human body not fixed value, relevant with frequency.
In test, electrode and skin surface also certainly exist a contact impedance to human body impedance, its size and skin condition, contact
The factors such as area are relevant, drastically decline also with the increase of test frequency.Therefore, the test of human body impedance data for convenience
Analysis, human body impedance test system is often operated under frequency higher, such as TI companies release for human body impedance measuring
Chip ADS1294R work fundamental frequency be 32kHz, now, the human body impedance for measuring can approximately regard purely resistive as；Through
Impedance value between experiment, the limb of human body two is about 1500 Ω or so.
One typical human body impedance test system, including constant pressure source VS, output internal resistance ro, outside output impedance RO, it is tested
Human body RB, the module etc. such as the treatment of voltage record and impedance demodulation.Synchronous recording and treatment two-way voltage signal, this two paths of signals can
Being the voltage signal and known outside output impedance R of the measuring point of human body twoOOn voltage signal, or human body two measuring point
Voltage signal and electric power output voltage signal, or known outside output impedance ROOn voltage signal and power supply output letter
Number, then by certain calculating, the complex impedance of human body can be demodulated, this is so-called four line impedences mensuration, such as Fig. 2 (a)
Shown in (b) (c)；To extra high test frequency, human body impedance R is testedBPurely resistive can be regarded as, now, also can only record and
Voltage signal measures human body impedance value all the way for treatment, referred to as two line impedence mensurations, as shown in Figure 3.
Which type of human body impedance test system ineffective is, the basic step of human body impedance method of testing is all：(1)
Test system building；(2) based on normal impedance calibration system；(3) human body impedance test.For convenience's sake, existing way
All it is：The first step when system is built, using big output impedance RO, excitation power supply is changed into constant-current source, make human body impedance with
The detection voltage at its two ends is linear, consequently facilitating the calibration of system, second step only needs to less normal impedance and demarcates i.e.
Can.The deficiency of existing method is：Output impedance is too big, same driving voltage, produces less operating current, right so as to cause
The sensitivity of human body impedance change is relatively low, is unfavorable for pathology and physiologic information that reflection breathing etc. causes human body impedance to change.
Bibliography：
[1] TI, ADS 1298R Datasheet, Texas Instruments Incorporated, 2010.
A kind of new Respiratory Detecting System Using Impedance Method [J] Chinese medical devices of the such as [2] Wang Jianbo, Deng Qinkai, Guo Jingsong
Tool magazine, 2009,33 (2)
The progress health cares equipment of the breath signal detection techniques such as [3] Xi Tao, Yang Guosheng, hot water bathing pool, 2004,
12：26-29.
[4] Prutchi, D.and M.Norris. (2004) .Design and development of medical
electronic instrumentation：A practical perspective of the design,
Construction, and test of medical devices.Hoboken, NJ：Wiley Interscience.
[5] Grenvik, A., Ballou, S., McGinly, E., Cooley, W.L., and P.Safar. (1972)
.Impedance pneumography：Comparison between chest impedance changes and
The healthy volunteers.Chest, vol 62, pp.439-443. of respiratory volumes in 11
[6] Kelkar, S.P., Khambete, N.D., and S.S.Agashe. (2008) .Development of
movement artefacts free breathing monitor.Journal of the Instrument Society
Of India, vol.38, pp.34-43.
[7] a kind of impedance method breath signals of Qi Jianxin, Lin Yuan, Bian Zhengzhong detect design [J] Chinese medical devices of circuit
Tool magazine, 1998,22 (1)：9-11.
[8] Deng parent happy modern medicine Instrument Design principle [M] Beijing：Science Press, 2004.
The content of the invention
Goal of the invention.
Propose a kind of high sensitivity human body impedance detection method.
Technical scheme.
A kind of detection method of human body impedance, step includes that (1) test system building, (2) are demarcated based on normal impedance and are
System, (3) carry out human body impedance test, it is characterized in that：When (1st) step builds system, using as far as possible small outside output impedance
RO, it is similar to using constant pressure source forcing, to ensure as far as possible big operating current；In (2nd) step system calibration, in measurement range
It is interior, system is demarcated using enough normal impedance samples, i.e., to each normal impedance sample, it is measured in given excitation
Under corresponding voltage value, finally fitting sets up one-to-one relationship between impedance and test voltage.There is such one-to-one corresponding
Relation, when (3rd) step is actually detected, though what is directly measured is magnitude of voltage, can converse corresponding human body impedance value.
Above human body impedance detection method puies forward highly sensitive principle and can be further elaborated.It is with two line impedence mensurations
Example, as shown in Figure 3, it is assumed that excitation constant pressure source is VS, output internal resistance be ro, outside output impedance be RO, it is tested human body impedance RBThis
When be purely resistive, then the detection sensitivity for having human body impedance is：
Work as RO＞ ＞ RBAnd RO＞ ＞ ro, excitation can be regarded as constant current source forcing, then flow into the operating current of human body
I is approximately：
The impedance variations for making us body are Δ R, then the voltage change Δ V for detecting is：
Δ V=I* Δs R (3)
By above-mentioned derivation, we it is seen that, due to outside output impedance R in traditional constant-current source schemeOIt is very big, greatly
Operating current is limited greatly, so that whole change of the circuit to impedance is insensitive, simultaneously because in actual measuring environment
The influence of each noise like, Checking on effect can be very poor.
This programme, approximate constant voltage source forcing substantially reduces the output impedance R of circuitO, can simply take outside output
Impedance ROIt is 0, now, there is operating current：
Compare formula (2) and formula (4) understands that we are very easy to find due to eliminating outside output impedance RO, so
Now flow into the operating current I of human body1It is far longer than I.So under identical impedance variations, the system that this programme is built will
There is sensitivity higher than the system that traditional constant-current source scheme is built.
Beneficial effect.
According to two line impedence mensurations shown in Fig. 3, the circuit and this programme under traditional constant-current source scheme are built respectively
Under circuit, the sensitivity of system under two schemes is detected using measuring resistance.8 high accuracy of different resistances are have chosen altogether
Resistance simulation human body impedance is tested.Table 1 is its two ends that this programme is surveyed with constant-current source scheme to various criterion resistance value
Magnitude of voltage situation.
This programme of table 1 actual measurement magnitude of voltage corresponding from the different resistances that constant-current source scheme is measured
We want the sensitivity of evaluation system, then want comparison resistance often to change identical resistance, the change size of voltage.It is logical
Cross above-mentioned data, it can be appreciated that the Ω of 910 Ω to 2700 divide into 7 sections by above-mentioned 8 different resistance values, make each section it is right
The resistance variations answered are Δ R, and each section of corresponding voltage change is designated as the Δ V of this programme respectively1With the Δ V of constant-current source scheme2,
So we just can obtain respectivelyWithTwo class values, every group has 7 values.Table 2 is different resistances under two schemes
Section resistance often changes 1 ohm of voltage change for causing.Resulting value is bigger, shows to be got in the sensitivity of the stage system
It is good.
Different resistance section resistance often change 1 ohm of voltage change for causing under the two schemes of table 2
As seen from the above table, the changing value in this programme each stage in the Ω of 910 Ω to 2700 is all different, and in rising
Trend.And the changing value of conventional constant current source scheme is generally about in 26 μ V or so.By contrast, it has been found that no matter is resistance value
In which resistance section, the sensitivity of this programme will be better than traditional constant-current source scheme, this and derivation result phase above
Unanimously.
Brief description of the drawings
Fig. 1, the basic step block diagram of human body impedance detection method.
Fig. 2, typical four-wire method human body impedance test system schematic diagram.
Fig. 3, two collimation method human body impedance test system schematic diagrames.
Fig. 4, human body impedance detecting system schematic diagram in embodiment.
Fig. 5, the resistive voltage relation fitting result schematic diagram of this programme calibration in embodiment.
Fig. 6, surveys human body impedance data variation figure in embodiment.
Embodiment
Human body impedance detecting system such as Fig. 4 is built, and it is actually detected for human body impedance.The system includes acquisition module,
Control module and host computer processing module and power circuit.Acquisition module uses the ADS1294R cores of TI companies production
Piece.By configuring, the square-wave signal of chip generation 2.4V, 32KHz can be made for the excitation of circuit, this driving voltage has one
Fixed output internal resistance ro, because test frequency is high, belong to two-wire system measurement pattern.In addition the chip internal be integrated with 24 ADC with
And modulation /demodulation module.Control section uses C8051F320 single-chip microcomputers, the single-chip microcomputer be internally integrated USB module and
SPI communication agreement is supported, can be by the information transmission of host computer to ADS1294R, while the packed transmission of the signal that will be collected
Give host computer treatment.Epigynous computer section uses the graphical programming language LabVIEW of NI companies, the data reality that will be collected
When show and preserve.Power circuit is then for whole system is powered, it is ensured that system is normally run.
First whole system is demarcated before the actual measurement of human body impedance is carried out.We choose a large amount of resistances and are distributed in
The measuring resistance of 910 Ω -3000 Ω, surveys out the corresponding magnitude of voltage of each of which, and resistance is fitted with the relation of voltage
Come as shown in Figure 5.Certainly the mode of fitting has many kinds, such as interpolation method, least square method etc..By fitting, Wo Menbian
It is known that the corresponding magnitude of voltage of certain resistance or the corresponding resistance value of certain voltage within the specific limits.
Next system is used for human experimentation, simple cleaning treatment first is carried out to arm with alcohol and medical cotton stick.
Requirement according to databook configures ADS1294R, and electrode paste is affixed at the arm at human body two ends, runs host computer, sits quietly,
The voltage data of 20s is measured and records, shown in such as Fig. 6 (a).It is assumed that a certain voltage is 100032 μ V, demarcated by before lookup
The table of comparisons set up, can find, and the corresponding voltages of 1600 Ω are that the 99122 corresponding voltages of μ V, 1700 Ω are 106378 μ V,
Let us now assume that the voltage change caused because of resistance variations in the range of this is linear, it is computed drawing now
Corresponding human body impedance value is 1612.54 Ω.Using the above method, we can be drawn in this 20s, the impedance variations feelings of human body
Shown in condition, such as Fig. 6 (b).
Claims (1)
1. a kind of detection method of human body impedance, step includes that (1) test system building, (2) are demarcated based on normal impedance and are
System, (3) carry out human body impedance test, it is characterized in that：When (1st) step builds system, using as far as possible small outside output impedance
R0, it is similar to using constant pressure source forcing, to ensure as far as possible big operating current；In (2nd) step system calibration, in measurement range
It is interior, system is demarcated using enough normal impedance samples, i.e., to each normal impedance sample, it is measured in given excitation
Under corresponding voltage value, finally fitting sets up one-to-one relationship between impedance and test voltage.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108649924A (en) * | 2018-05-11 | 2018-10-12 | 新华网股份有限公司 | Detection circuit, method and device for human body resistance and computer readable storage medium |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1276709A (en) * | 1997-10-17 | 2000-12-13 | 株式会社百利达 | Body fat meter and body weight scales equipped with body fat meter |
| CN1907220A (en) * | 2006-08-16 | 2007-02-07 | 中山市创源电子有限公司 | Human body impedance measuring apparatus and fat meter using same |
-
2017
- 2017-03-01 CN CN201710127392.1A patent/CN106725474A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1276709A (en) * | 1997-10-17 | 2000-12-13 | 株式会社百利达 | Body fat meter and body weight scales equipped with body fat meter |
| CN1907220A (en) * | 2006-08-16 | 2007-02-07 | 中山市创源电子有限公司 | Human body impedance measuring apparatus and fat meter using same |
Non-Patent Citations (3)
| Title |
|---|
| T QURESHI， ET AL.: "Optimal device for a low output impedance voltage source for Electrical Impedance Tomography（EIT） Systems", 《IEEE》 * |
| TABASSUM R QURESHI,ET AL.: "Investigation of voltage source design’s for Electrical Impedance Mammography (EIM) Systems", 《34TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE EMBS》 * |
| 刘宝华: "一种新的阻抗式呼吸检测系统的设计", 《生物医学工程学杂志》 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108649924A (en) * | 2018-05-11 | 2018-10-12 | 新华网股份有限公司 | Detection circuit, method and device for human body resistance and computer readable storage medium |
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Application publication date: 20170531 |