CN105380647B - A kind of faint motional impedance detection device and its method based on four electrode half-bridge methods - Google Patents
A kind of faint motional impedance detection device and its method based on four electrode half-bridge methods Download PDFInfo
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- CN105380647B CN105380647B CN201510700478.XA CN201510700478A CN105380647B CN 105380647 B CN105380647 B CN 105380647B CN 201510700478 A CN201510700478 A CN 201510700478A CN 105380647 B CN105380647 B CN 105380647B
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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
Abstract
The invention discloses a kind of faint motional impedance detection device and its method based on four electrode half-bridge methods, half arm self-balancing bridge circuit circuit are collectively formed by digital regulation resistance and bio-impedance；Pga circuit is made of 2 instrumentation amplifiers and a programmable instrument amplifier, and the output of an instrumentation amplifier is the partial pressure V of digital regulation resistance1, another instrumentation amplifier output is the partial pressure V of bio-impedance2, the output of programmable instrument amplifier is V1And V2Difference；Automatic Balance Regulation circuit, according to the fast digital phase lock circuitry based on over-sampling demodulate come faint motional impedance variable signal voltage magnitude as negative-feedback, control the tap position of digital regulation resistance, until the voltage magnitude demodulated enters within threshold value, then Automatic Balance Regulation circuit enters equilibrium state.The present invention realizes the detection of the motional impedance based on four electrode half-bridge methods, with high-precision, high sensitivity, Larger Dynamic range, the advantage for realizing simple, real-time continuous measurement.
Description
Technical field
The present invention relates to motional impedance detection field more particularly to a kind of faint motional impedances based on four electrode half-bridge methods
Detection device and its method.
Background technique
Bioelectrical impedance analysis is a kind of non-invasive, at low cost, common anthropological measuring and clinical state appraisal procedure.With
The development increasingly of biological impedance technology and mature, biological impedance is applied to clinic and has become possibility.Biology resistance
It is anti-to be divided into static basis impedance and two parts of faint motional impedance.Faint motional impedance variation often carries more physiology
Information, therefore the real-time continuous monitoring of faint motional impedance variable quantity provides possibility for clinical application.In faint motional impedance
Measurement in, it is crucial for deducting the influence of static basis impedance.
Inventor has found in the implementation of the present invention, existing impedance measurement method, usually to quiet in collection process
State impedance and faint motional impedance are acquired simultaneously, and carry out the amplification of same degree, for and its faint motional impedance
The measurement of variable quantity causes certain difficulty.Biggish static basis impedance simultaneously can introduce individual difference, survey for impedance
Amount means are applied to clinic and cause certain difficulty.
Summary of the invention
The present invention provides a kind of faint motional impedance detection device and its method based on four electrode half-bridge methods, the present invention
Have many advantages, such as that precision height, high sensitivity, dynamic range are big, it is low in energy consumption and low in cost, it can be to more faint dynamic
Impedance variation amount carries out continuous prolonged monitoring, described below:
A kind of faint motional impedance detection device based on four electrode half-bridge methods, comprising: excitation constant-current source, further includes:
Half arm self-balancing bridge circuit circuit, is collectively formed by digital regulation resistance and bio-impedance；
Pga circuit is collectively formed by 2 instrumentation amplifiers and a programmable instrument amplifier, and an instrument is put
The output of big device is the partial pressure V of digital regulation resistance1, the output of another instrumentation amplifier is the partial pressure V of bio-impedance2, may be programmed instrument
The output of device amplifier is V1And V2Difference；
Automatic Balance Regulation circuit, according to the fast digital phase lock circuitry based on over-sampling demodulate come faint dynamic hinder
The voltage magnitude of anti-variable signal controls the tap position of digital regulation resistance as negative-feedback, until the voltage magnitude demodulated
Into within threshold value, then Automatic Balance Regulation circuit enters balance dress state.
The excitation constant-current source is high frequency sinusoidal constant current supply pumping signal.
The four electrode configurations circuit is made of four electrodes, is carried out in such a way that excitation electrode and measuring electrode are separated
Configuration.
The programmable instrument amplifier is used to carry out static basis impedance and faint dynamic change impedance different degrees of
Amplification.
A kind of faint motional impedance detection method based on four electrode half-bridge methods, the method are a kind of autobalance half-bridges
Method the described method comprises the following steps:
Digital regulation resistance is expressed as RS, tested bio-impedance is expressed as RZ；
After high frequency sinusoidal current excitation, RSOutput voltage of the both end voltage after an instrumentation amplifier is expressed as
V1, RZOutput voltage of the both ends after another instrumentation amplifier is expressed as V2；
V1With V2Output voltage after programmable instrument amplifier is expressed as Vout, VoutIt is converted by analog-digital converter
Digital signal；
Demodulation average filter is carried out to digital signal by the fast digital locking phase based on over-sampling, obtains tested impedance
Voltage magnitude；
The voltage magnitude for the tested bio-impedance that fast digital demodulation of phase locking obtains is as negative-feedback signal, by putting down automatically
Weighing apparatus electric bridge is adjusted the tap position of digital regulation resistance；
If inclined absolute value of the difference is greater than deviation threshold, amplitude and deviation are recalculated, until inclined absolute value of the difference is less than
Deviation threshold then completes the adjusting of bridge balance.
The beneficial effect of the technical scheme provided by the present invention is that: the present invention removes the shadow of contact impedance by four electrode method
It rings, while achieving the purpose that deduct larger static basis impedance using autobalance half-bridge method, and amplify by programmable instrument
Device carries out different degrees of amplification to static basis impedance and motional impedance variable quantity, then carries out base to the data after ADC sampling
In the quick phase locked algorithm of over-sampling to demodulate faint impedance variation amount.The present invention can be to faint motional impedance variable quantity
Continuous, detection for a long time is carried out, and has precision height, high sensitivity, dynamic range big, low in cost, low in energy consumption, small in size
The characteristics of, application value with higher.
Detailed description of the invention
Fig. 1 is a kind of structural representation of the faint motional impedance detection device based on four electrode half-bridge methods provided by the invention
Figure；
Fig. 2 is the circuit diagram of the faint motional impedance detection provided by the invention based on four electrode half-bridge methods；
Fig. 3 is distribution of electrodes figure provided by the invention；
Fig. 4 is the flow chart that the adjustment of amplitude autobalance is carried out to electric bridge；
Fig. 5 is experimental waveform figure.
In attached drawing, each component is listed as follows:
1: excitation constant-current source；2: half arm self-balancing bridge circuit circuits；
3: pga circuit；4: fast digital phase lock circuitry；
5: Automatic Balance Regulation circuit；6: four electrode configuration circuits.
Specific embodiment
To make the object, technical solutions and advantages of the present invention clearer, embodiment of the present invention is made below further
Ground detailed description.
Embodiment 1
A kind of faint motional impedance detection device based on four electrode half-bridge methods, referring to Fig. 1 and Fig. 2, the detection device packet
It includes: excitation constant-current source 1, half arm self-balancing bridge circuit circuit 2, pga circuit 3, the fast digital locking phase based on over-sampling
Circuit 4, Automatic Balance Regulation circuit 5 and four electrode configuration circuits 6.
Wherein, excitation constant-current source 1 is high-frequency sine constant-current source pumping signal.
The bridge arm of half arm self-balancing bridge circuit circuit 2 is collectively formed by digital regulation resistance and bio-impedance, and half arm is automatic
The purpose of null-type bridge circuit 2 is to deduct static basis impedance, eliminates its caused individual difference, extracts faint motional impedance
Component is to improve dynamic range and measurement accuracy.
Referring to fig. 2, pga circuit 3 is mainly common by 2 instrumentation amplifiers and a programmable instrument amplifier
It constitutes, wherein the output of instrumentation amplifier A1 is the partial pressure V of digital regulation resistance1, the output of instrumentation amplifier A2 is bio-impedance
Partial pressure V2, the output of programmable instrument amplifier A3 is V1And V2Difference Vout, the wherein master of programmable instrument amplifier A3
Wanting function is to carry out different degrees of amplification to static basis impedance and faint dynamic change impedance.
Automatic Balance Regulation circuit 5, according to the fast digital phase lock circuitry 4 based on over-sampling demodulate come faint dynamic
The voltage magnitude of impedance change signal controls the tap position of digital regulation resistance as negative-feedback, faint until what is demodulated
The voltage magnitude of motional impedance variable signal enters within default threshold value, then Automatic Balance Regulation circuit 5 enters equilibrium state.
When specific implementation, high frequency sinusoidal constant current supply pumping signal can be generated by microprocessor；Based on the quick of over-sampling
Digital servo-control circuit 4 can also be realized by microprocessor；Pga circuit 3 and Automatic Balance Regulation circuit 5 also can be with
It is realized by micro process.
Four electrode configuration circuits 6 are made of four electrodes, are matched in such a way that excitation electrode and measuring electrode are separated
It sets.Its major function is the interference eliminating contact impedance and introducing, and then improves the measurement accuracy of system.Referring to fig. 2 and Fig. 3, four
Electrode is respectively a, b, c and d, and wherein a, d are excitation electrode, and b, c are 2 measuring electrodes.
Wherein, above-mentioned all microprocessors mentioned are same microprocessors, which is a kind of highly integrated micro-
The processor of power consumption, it is low in cost, it is easy to operate.Microprocessor can be using any one in MCU, ARM, DSP or FPGA.
Embodiment 2
The faint motional impedance based on four electrode half-bridge methods in embodiment 1 is detected below with reference to specific device type
Device is further described through, as detailed below:
In the embodiment of the present invention, the microprocessor used is low-power microprocessor CY8C3866AXI；Analog-digital converter
ADC is 11bit, and sample rate 200Ksps, over-sampling multiple is 4.
Amplifying circuit 3 include programmable gain amplifier on 2 instrumentation amplifier AD623 and microprocessor used with
The programmable instrument amplifier A3 that amplifier is constituted improves programmable amplification after Automatic Balance Regulation circuit 5 reaches equilibrium state
The gain of device can demodulate faint motional impedance variable signal to the distortionless maximum gain of signal at this time.Autobalance tune
Digital regulation resistance in economize on electricity road 5 has the 20k digital regulation resistance AD5272 of 1024 taps.
The lower number of sampling points of average filter is 25000 in fast digital phase lock circuitry 4 based on over-sampling, about 46-48It
Between, so analog-digital converter ADC is equivalent to mention most-significant byte, the equivalent resolution of the detection device reaches 0.822 μ V/bit.It is more micro-
Weak motional impedance variable quantity can be measured accurately.Self-balancing bridge circuit makes system signal noise ratio be significantly improved.
Embodiment 3
Realize that the basic principle of the faint motional impedance detection method of four electrode half-bridge methods is described as follows, in detail as shown in Figure 4
Schematic diagram be referred to as elementary errors modulation method firstly, this method is a kind of autobalance half-bridge method, half arm modulation bridge by
Digital regulation resistance RSWith bio-impedance RZIt collectively forms.
101: microprocessor generates high frequency sinusoidal current excitation signal all the way and is expressed as I (t), set of frequency 50kHz；
102: digital regulation resistance is expressed as RS, tested bio-impedance is expressed as RZ；
103: passing through after high frequency sinusoidal current excitation, RSOutput voltage meter of the both end voltage after instrumentation amplifier A1
It is shown as V1, RZOutput voltage of the both ends after instrumentation amplifier A2 is expressed as V2；
104:V1With V2Output voltage after programmable instrument amplifier A3 is expressed as Vout, VoutBy in microprocessor
Analog-digital converter ADC digital signal V is converted into the sample rate of 200KspsDout；
105: microprocessor is by the fast digital locking phase based on over-sampling to digital signal VDoutIt is average to carry out demodulation
Filtering obtains the voltage magnitude of tested impedance；
106: the voltage magnitude for the tested bio-impedance that fast digital demodulation of phase locking obtains is as negative-feedback signal, by certainly
Dynamic balancing electric bridge is adjusted the tap position of digital regulation resistance.
When specific implementation, according to four electrode configuration schemes, electrode and measuring electrode spaced apart are motivated, is connect with guaranteeing to eliminate
The interference that impedance introduces is touched, there is excitation one measuring electrode of electrode at the both ends of impedance to be measured, and motivate electrode and measurement
Electrode gap is about 2.5cm.
In the embodiment of the present invention, the flow chart of specific implementation bridge balance adjustment includes referring to fig. 4: starting to adjust, set
Digital regulation resistance initial position is set, the amplitude for calculating digital signal, amplitude and target value deviation is calculated, tap is calculated by deviation
Position is simultaneously arranged digital regulation resistance tap position, calculates deviation again, judges whether the threshold range for reaching deviation, completes electric bridge
The adjusting of balance improves the gain of programmable amplifier after balance, and program adjustment terminates, and starts to measure motional impedance variation letter
Number.
Wherein, start condition be that human body is remain stationary motionless, system electrification, the startup program of adjustment.Amplitude balance is adjusted
It is with the calculated V of quick locking phase based on over-samplingDoutSignal amplitude as negative-feedback signal, it is true by negative-feedback signal
Determine the tap position of digital regulation resistance, so that electric bridge is reached equilibrium state by adjusting the tap position of digital regulation resistance.
Firstly, the initial position R of the tap of setting digital regulation resistanceS=0, calculate digital signal V at this timeDoutSignal
Amplitude y calculates amplitude y by e=y-w and adjusts the deviation e of target value w, according to formula ui=ke+u0Calculating is adjusted next time
The tap position u of whole required digital regulation resistancei, wherein k is to adjust proportionality coefficient, u0For the initial position of digital regulation resistance, meter
Calculate uiThe tap position of digital regulation resistance is reset afterwards, if the absolute value of deviation e is greater than the threshold value E0 of deviation, is needed again
Amplitude y and deviation e is calculated, until the absolute value of deviation e is less than the threshold value E0 of deviation, then completes the adjusting of bridge balance, at this point,
The gain of programmable instrument amplifier is improved to distortionless maximum rating, i.e. gain k=max, program adjustment terminates, defeated at this time
Signal V outoutAs faint motional impedance variable signal.
Wherein, k is scaling factor, is determined by the characteristic of whole device.
Wherein, adjustment target value w is set as 20mV, and output amplitude y is arranged and adjusts the threshold value E0 of the deviation e of target value w
=10mV judges whether that the adjusting condition for completing balanced adjustment is that the absolute value of deviation e is less than the threshold value E0 of deviation.Adjustment is completed
The range of output signal y is between w-E0 and w+E0 afterwards.
Wherein, the range that programmable instrument amplifier gain improves is 4~32 times.It, can be with by the adjusting of above step
The bio-impedance magnitude of minor change is set to be amplified and be more readily detected.
Embodiment 4
The faint motional impedance based on four electrode half-bridge methods in embodiment 3 is measured below with reference to specific calculation formula
Basic principle be described in detail, it is as detailed below:
When the pumping signal that microprocessor generates is high-frequency current signal, it can be indicated with formula (1):
I=Asin (wt)+I0 (1)
Wherein, the π f of ω=2 is the angular frequency of pumping signal；I is excitation current source；T is time variable；A is alternating current
The amplitude in source；I0For DC bias current.Wherein the output of instrumentation amplifier A1 is RSBoth end voltage, expression formula such as formula (2)
It is shown:
V1=IRS=RS(Asin(wt)+I0)=ARS sin(wt)+I0RS (2)
Wherein the output of instrumentation amplifier A2 is bio-impedance RZBoth end voltage, shown in expression formula such as formula (3):
V2=I (RZ+ Δ Z)=(RZ+ΔZ)(Asin(wt)+I0)=RZ(Asin(wt)+I0)+ΔZ(Asin(wt)+I0) (3)
The output of programmable instrument amplifier A3 is V1With V2Difference, shown in expression formula such as formula (4):
Vout=V1-V2=(RS-RZ)(Asin(wt)+I0)-ΔZ(Asin(wt)+I0) (4)
Wherein, bio-impedance includes: static basis impedance and dynamic change impedance two parts, RZIndicate static basis resistance
Anti-: Δ Z indicates faint motional impedance variable quantity.
Want the faint motional impedance variable quantity of measurement, needs to deduct the influence of static basis impedance, so that signal-to-noise ratio is improved,
Expand the dynamic range of signal.Wherein, digital regulation resistance RSMain function be exactly the influence for deducting static basis impedance.
When specific implementation, when starting to adjust electric bridge, 1 is set by the multiple of all amplifiers, adjusts digital regulation resistance
Tap position, until RSWith RZIt is approximately equal.Output is as shown in formula (5) at this time:
Vout=V1-V2=-Δ Z (Asin (wt)+I0) (5)
Simultaneously because Δ Z is minimum, thus exports close to 0, so electric bridge amplifies programmable instrument close to balance at this time
The amplification factor of device A3 is adjusted to distortionless maximum rating, then output signal is the signal of faint motional impedance variable quantity.
Embodiment 5
Feasibility verifying is carried out to the scheme in embodiment 1-4 below with reference to specific example, described below:
By taking measurement breathing as an example, microprocessor used is the CY8C3866 of CYPRESS, and excitation current source I used is micro- by this
IDAC on processor is generated, and frequency uses 50kHz, and half-bridge circuit is constituted using digital regulation resistance AD5272 and human body impedance,
Digital regulation resistance AD5272 used, tap are 1024 taps, and total resistance value is 20k Ω, and the resolution ratio of resistance is 19.5 Ω.Enlarging section
Divide and be made of 2 instrumentation amplifier AD623 and programmable instrument amplifier A3, wherein programmable instrument amplifier A3 is by micro process
Programmable amplifier on device is collectively formed with operational amplifier composition.ADC sample rate on microprocessor used is set as
200ksps.Demodulating algorithm used is the quick phase locked algorithm of number based on over-sampling, is counted as 25000 points, after lower sampling
The sampling rate arrived is 8sps, obtains 480 points per minute.
Fig. 5 is the respiratory waveform detected in 1 minute, and wherein abscissa is sampling number, and ordinate is the output of system,
As shown in Figure 5, measured respiratory rate is 16 times/min.
This faint motional impedance measurement method based on four electrode half-bridge methods is by deducting static basis impedance elimination
Body difference eliminates the interference that contact impedance introduces, improves measurement accuracy, can be to the faint motional impedance variable quantity of Different Individual
Continuous real-time monitoring is carried out, there is important clinical value.
The embodiment of the present invention to the model of each device in addition to doing specified otherwise, the model of other devices with no restrictions,
As long as the device of above-mentioned function can be completed.
It will be appreciated by those skilled in the art that attached drawing is the schematic diagram of a preferred embodiment, the embodiments of the present invention
Serial number is for illustration only, does not represent the advantages or disadvantages of the embodiments.
The foregoing is merely presently preferred embodiments of the present invention, is not intended to limit the invention, it is all in spirit of the invention and
Within principle, any modification, equivalent replacement, improvement and so on be should all be included in the protection scope of the present invention.
Claims (3)
1. a kind of faint motional impedance detection device based on four electrode half-bridge methods, comprising: excitation constant-current source, further includes:
Half arm self-balancing bridge circuit circuit, is collectively formed, bio-impedance includes: static basis by digital regulation resistance and bio-impedance
Impedance and faint motional impedance, the digital regulation resistance are eliminated individual difference, are extracted faint for deducting static basis impedance
Motional impedance is to improve dynamic range and measurement accuracy；
Pga circuit is collectively formed, an instrumentation amplifier by 2 instrumentation amplifiers and a programmable instrument amplifier
Output be digital regulation resistance partial pressure V1, the output of another instrumentation amplifier is the partial pressure V of bio-impedance2, programmable instrument puts
The output of big device is V1And V2Difference, the programmable instrument amplifier be used for static basis impedance and faint motional impedance
Carry out different degrees of amplification；
Automatic Balance Regulation circuit, according to the fast digital phase lock circuitry based on over-sampling demodulate come faint motional impedance become
Change the voltage magnitude of signal as negative-feedback, control the tap position of digital regulation resistance, until the voltage magnitude demodulated enters
Within threshold value, then Automatic Balance Regulation circuit enters equilibrium state；
Four electrode configuration circuits are made of four electrodes, are configured in such a way that excitation electrode and measuring electrode are separated.
2. a kind of faint motional impedance detection device based on four electrode half-bridge methods according to claim 1, feature exist
In the excitation constant-current source is high frequency sinusoidal constant current supply pumping signal.
3. a kind of faint dynamic resistance for implementing in claim 1-2 described in any claim based on four electrode half-bridge methods
The detection method of anti-detection devices, which is characterized in that the method is a kind of autobalance half-bridge method, and the method includes following
Step:
Digital regulation resistance is expressed as RS, tested bio-impedance is expressed as RZ；
After high frequency sinusoidal current excitation, RSOutput voltage of the both end voltage after an instrumentation amplifier is expressed as V1, RZ
Output voltage of the both ends after another instrumentation amplifier is expressed as V2；
V1With V2Output voltage after programmable instrument amplifier is expressed as Vout, VoutNumber is converted by analog-digital converter
Signal；
Demodulation average filter is carried out to digital signal by the fast digital locking phase based on over-sampling, obtains the electricity of tested impedance
Pressure amplitude value；
The voltage magnitude for the tested bio-impedance that fast digital demodulation of phase locking obtains passes through autobalance electricity as negative-feedback signal
Bridge is adjusted the tap position of digital regulation resistance；
If inclined absolute value of the difference is greater than deviation threshold, amplitude and deviation are recalculated, until inclined absolute value of the difference is less than deviation
Threshold value then completes the adjusting of bridge balance.
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| CN106175773B (en) * | 2016-07-11 | 2019-09-10 | 芯海科技（深圳）股份有限公司 | Hand held multiband impedance breath signal measuring system and measurement method |
| CN106901706A (en) * | 2017-03-10 | 2017-06-30 | 安徽通灵仿生科技有限公司 | A kind of children gloves formula remote diagnosis system |
| CN106805948A (en) * | 2017-03-10 | 2017-06-09 | 安徽通灵仿生科技有限公司 | A kind of children use finger cot type remote diagnosis system |
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| US3750649A (en) * | 1971-06-25 | 1973-08-07 | Univ California | Pulmonary impedance bridge |
| US4291708A (en) * | 1977-11-02 | 1981-09-29 | Yeda Research & Development Co. Ltd. | Apparatus and method for detection of tumors in tissue |
| CN1114174A (en) * | 1994-05-23 | 1996-01-03 | 姚雪祥 | Automatic analyzing and diagnosing method and apparatus for hemotachogram |
| CN2577235Y (en) * | 2002-11-08 | 2003-10-01 | 中国科学院武汉岩土力学研究所 | High-precision gain-adjustable dynamic strain instrument |
| CN102662109A (en) * | 2012-04-16 | 2012-09-12 | 上海电机学院 | Balanced bridge |
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2015
- 2015-10-26 CN CN201510700478.XA patent/CN105380647B/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3750649A (en) * | 1971-06-25 | 1973-08-07 | Univ California | Pulmonary impedance bridge |
| US4291708A (en) * | 1977-11-02 | 1981-09-29 | Yeda Research & Development Co. Ltd. | Apparatus and method for detection of tumors in tissue |
| CN1114174A (en) * | 1994-05-23 | 1996-01-03 | 姚雪祥 | Automatic analyzing and diagnosing method and apparatus for hemotachogram |
| CN2577235Y (en) * | 2002-11-08 | 2003-10-01 | 中国科学院武汉岩土力学研究所 | High-precision gain-adjustable dynamic strain instrument |
| CN102662109A (en) * | 2012-04-16 | 2012-09-12 | 上海电机学院 | Balanced bridge |
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| 基于DLIA的交流阻抗谱测量系统关键技术研究;胡宾鑫;《万方数据》;20121225;第2,9-10,52，72页 * |
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