CN109171764A - A kind of SCM Based blood oxygen detection method - Google Patents
A kind of SCM Based blood oxygen detection method Download PDFInfo
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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
- A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
- A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
- A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
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- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7203—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal
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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
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7235—Details of waveform analysis
- A61B5/725—Details of waveform analysis using specific filters therefor, e.g. Kalman or adaptive filters
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Abstract
The present invention relates to medical electronics technical fields, specifically disclose a kind of SCM Based blood oxygen detection method, detection method includes the following steps: step 1, blood oxygen signal acquisition: by single-chip microcontroller output pwm signal, processing is amplified by the pwm signal that driving circuit exports single-chip microcontroller, and the signal is transmitted at blood oxygen probe and controls blood oxygen probe progress blood oxygen signal collecting work acquisition blood oxygen photo-signal；Step 2, blood oxygen signal pretreatment: voltage signal to be processed is converted by current/voltage converter circuit to the blood oxygen photo-signal that step 1 is taken；Step 3, voltage filter processing；Step 4, blood oxygen signal processing.The present invention realizes the comprehensive of each frequency noise signal in pulse wave signal and quickly filters out, and with good stability, accuracy, sensitivity.
Description
Technical field
The present invention relates to medical electronics technical fields, more particularly to a kind of SCM Based blood oxygen detection method.
Background technique
According to statistics, by the end of the year 2017, the number of all kinds of cardiovascular patients in China up to 2.8 hundred million people, and angiocarpy
The lethality of disease is up to 40%, in China's death rate statistics, is in first three within cardiovascular disease continuous ten years.Because of blood
The vitals anoxic such as physical and mental, brain, kidney caused by middle oxygen content is low, and then cause all kinds of cardiovascular diseases, it seriously endangers
The health of people.So either in daily life or in clinical treatment, the detection for oxygen content in blood seems outstanding
It is important.
Currently, the blood oxygen saturation in blood oxygen signal mainly carries out non-invasive optical detection using BOLD contrast.The country has perhaps
More medical apparatus corporation, Ltds and producer are engaged in the research of BOLD contrast, and Principle of Products is nearly all spectrophotometry, user
Fado is that finger is inserted in transmission sensors to detect.
The place of domestic BOLD contrast Shortcomings is the interference as caused by blood oxygen probe structure and use environment, to draw
Playing result appearance, error, reason are embodied in the following once in a while:
1, for bias light than stronger, ambient light is too strong；
2, user's test position (finger) shakes and introduces interference and cause distorted signals
3, the detection error as caused by age, the colour of skin, gender, individual physique reason is larger.
The required oxygen of each organ-tissue metabolism of human body, is transmitted by that can carry with the hemoglobin in conjunction with oxygen in blood
Everywhere to body, the joint efficiency of hemoglobin and oxygen directly influences the transmittability of oxygen, which can be full with blood oxygen
It is measured with degree, oximetry value is normal, then can guarantee the efficiency of transmission of oxygen in human body.Blood oxygen saturation indicates oxygenated blood
Lactoferrin accounts for the percentage of hemoglobin, and in tissue, the transport of oxygen is completed mainly by oxyhemoglobin.Oxygenated blood is red
The ability of albumen transport oxygen can be reflected as blood oxygen saturation numerical value, and the height of oximetry value indicates human body metabolism
Quality, oximetry value is too low, easily causes oxygen supply difficult, the decline of the oxygen consumptions organ dysfunction such as brain.And oximetry value mistake
Height indicates that internal oxygen environment is excessively high, causes blood viscosity high, body system is made to get muddled.So being directed to the inspection of blood oxygen saturation
Survey is particularly important.In the past, be mostly invasive measurement for the measurement method of blood oxygen saturation, but invasive measurement can not continuously into
Row, and easy infection at wound, therefore a kind of noninvasive oxygen saturation measurement instrument based on single-chip microcontroller for core control is studied, it realizes
The method of noninvasive, continuous measurement blood oxygen saturation is of great significance.
Summary of the invention
The technical problem to be solved in the present invention is to overcome the shortcomings of the prior art, provides a kind of SCM Based blood
Oxygen detection method.
In order to solve the above-mentioned technical problem, the invention adopts the following technical scheme:
A kind of SCM Based blood oxygen detection method, detection method includes the following steps:
Step 1, blood oxygen signal acquisition: by single-chip microcontroller output pwm signal, single-chip microcontroller is exported by driving circuit
Pwm signal amplifies processing, and the signal is transmitted at blood oxygen probe and controls blood oxygen probe progress blood oxygen signal acquisition work
Make to obtain blood oxygen photo-signal；
Step 2, blood oxygen signal pretreatment: current/voltage-converted electricity is passed through to the blood oxygen photo-signal that step 1 is taken
Road is converted into voltage signal to be processed；
Step 3, voltage filter processing: the voltage signal to be processed that step 2 obtains is filtered by the high pass of cutoff frequency 0.1Hz
Wave device filters DC component, retains AC compounent, allows the signal higher than 0.1Hz to pass through, the garbage signal lower than 0.1Hz is shielded
It covers；It then passes through by the second-order low-pass filter that frequency is 20~40Hz, filters out the garbage signal higher than 20Hz, it is final to obtain
Effective voltage signal within the scope of 0.1~20~40Hz；
Step 4, blood oxygen signal processing: AD converter is utilized, filter circuit output signal is directly subjected to A/D sampling；It is right
The pulse blood oxygen signal that samples carries out light beam separation, pulse wave detection obtains waveform diagram, by period of analysis waveform figure and
Amplitude, peak value complete numerical analysis, are exported numerical value to the end LCD or PC by serial ports via single-chip microcontroller and shown.
It is calculated according to langbobier law.Mainly there are reduced hemoglobin (Hb) and oxygenated blood in blood of human body tissue
Lactoferrin (HbO2) etc. 4 kinds of albumen, blood oxygen saturation can use Sp02This physical quantity indicates that the variation of value reflects human body
The situation of change of metabolism, the calculation formula of blood oxygen saturation are as follows:
Sp02=HbO2/HbO2+ Hb × 100%
Currently rely primarily on Dichroic Optical method detection blood oxygen saturation, Dichroic Optical method based on langbobier law,
It is mainly different according to absorptivity of the different material to different wave length, the content of different material is known via calculating sub-license.?
Reduced hemoglobin and oxyhemoglobin in blood of human body tissue have the characteristics that the absorption coefficient of light respective, work as selection
When wavelength is the red light-emitting of 660nm, oxyhemoglobin and reduced hemoglobin are maximum to the absorption coefficient difference of light, work as hair
When optical diode launch wavelength is the infrared light of 940nm, the two is minimum to absorption coefficient of light difference, by incident light and emergent light it
Between difference be expressed as current signal, by absorption difference to pulse blood oxygen waveform diagram is when analyzed, and then show that oxygenated blood is red
The total amount and percentage of albumen and hemoglobin.Hb mainly absorbs feux rouges, HbO2It is main to absorb infrared light.
Pulse blood oxygen waveform diagram is mainly made of DC component and AC compounent, the unwanted contributions such as bone, skin, melanin
Uptake to light is flip-flop DC, and arterial blood is reflected as AC compounent AC to the absorption of light, is useful component, HbO2With
Absorption of the Hb in arterial blood changes with the cyclically-varying of impulse action and becomes the exchange in oxygen saturation signal point
Measure AC, blood oxygen saturation virtual value is mainly the value of AC compounent, and AC and DC component is received by photoelectric receiving tube, blood oxygen signal from
After blood oxygen probe output, after filtering removal of impurities and current/voltage-converted, its pulse blood oxygen waveform diagram, nothing can be measured with oscillograph
DC component DC and useful AC compounent AC can be extracted from pulse blood oxygen waveform diagram by programming and be obtained, Ke Yigen
The absorption of oxyhemoglobin, reduced hemoglobin to two-way light is calculated according to the peak value of blood oxygen impulse waveform, amplitude and period
Rate, and thus calculate and remove detecting sphygmus and blood oxygen saturation, formula is as follows:
SpO2=A-BR+CR2
In formula, A, B, C are scaling constant, can be obtained by scaling experiment.
R=(VREDAC/VREDDC)/(VIREDAC/VIREDDC)
For the light absorption ratio of two wavelength, wherein VREDACFor the AC compounent of feux rouges；VREDDCFor the direct current point of feux rouges
Amount；VIREDACFor the AC compounent of infrared light；VIREDDCFor the DC component of infrared light.
Further, the process of single-chip microcontroller output pwm signal is as follows in the step 1: on modulated square wave, it is certain fixed to choose
When device/counter period, controlled using timer/counter and interrupt duration, within a signal period, allow high level, low
Level conversion reaches control PWM duty cycle output, completes in a cycle, low and high level presses the mutual conversion of some cycles.
Further, driving circuit described in step 1 mainly constitutes H-bridge circuit by 4 triodes and forms, 4 triodes point
Not Wei Q1, Q2, Q3, Q4, Q1, Q2 and the pwm signal that is exported using single-chip microcontroller of single-chip microcontroller connection are opened as the gating of driving circuit
It closes, when Q1 is connected, the red light of blood oxygen probe is bright, and when Q2 is connected, the infrared lamp of blood oxygen probe is bright；Q3, Q4 are electric as control is played
Stream effect, wherein the route of Q3 control conducting is connected several divider resistances, and the route of Q4 control conducting is connected several partial pressures
When resistance, 4 triodes are in a saturated state: triode ON, it is desirable that Vc > Vb and Ve > Vb, i.e. base stage connect low level；
When triode is in off state: collector and emitter disconnect, it is desirable that Vc < Vb and Ve < Vb, i.e. base stage connect high level.
Further, blood oxygen probe described in step 1 includes U-shaped phototransistor, is provided on the phototransistor
The transmitting light source and photoreceiver of two pairs of transmission light, two pairs of transmitting light sources and photoreceiver are equidistant and right
Claim setting, two pairs of transmitting light sources are respectively the red light for emitting feux rouges and the infrared lamp for emitting infrared light；Feux rouges or infrared light are worn
Optical signal is received by the photoreceiver of lower section after saturating arterial-venous, and is converted to current signal output corresponding with optical signal.
Blood oxygen probe of the invention is specifically completed using plastic glove and optical filter, all plastics hands of project by reasonable design
Set is generic latex gloves and common ultra thin optical optical filter, and filbtercharacteristic is that black can lead to infrared light (800nm-
1600nm), most of naked eyes visible light (400nm-680nm) percent of pass is only 10%, can completely cut off external light source interference well.
Traditional blood oxygen probe is roomy, and finger easily introduces noise jamming because of activity wherein, and project interception plastic glove finger tip one cuts packet
Blood oxygen probe is wrapped, avoids finger movement from causing distorted signals or introduces interference signal, probe opening is closed using optical filter, prevents
Only external light source interferes.
Further, current/voltage converter circuit described in step 2 includes an operational amplifier, the operational amplifier
Normal phase input end connects the collected current signal of step 1 institute, and anti-phase input terminates integrating circuit, and input terminal exports voltage to be processed
Signal, the integrating circuit are made of a feedback resistance and connecing in the feedback resistance capacitor in parallel with feedback resistance.
Further, the feedback resistance carries out choosing value according to following models:
R1=-U0/is
Wherein, R1For feedback resistance resistance value, for the voltage U to be processed of output0> 0.01V, is are photoelectric current, 1mA > is >
0.01nA；
Further, the capacitance of the capacitor is between 250~290pF.
Beneficial effect is: the present invention realizes the comprehensive of each frequency noise signal in pulse wave signal and quickly filters out, and
With good stability, accuracy, sensitivity.
Detailed description of the invention
It, below will be to specific in order to illustrate more clearly of the specific embodiment of the invention or technical solution in the prior art
Embodiment or attached drawing needed to be used in the description of the prior art are briefly described.In all the appended drawings, similar element
Or part is generally identified by similar appended drawing reference.In attached drawing, each element or part might not be drawn according to actual ratio.
Fig. 1 is structural principle block diagram of the invention；
Fig. 2 is driving circuit figure of the invention；
Fig. 3 is that driving circuit of the invention runs figure；
Fig. 4 is pwm signal waveform diagram of the invention；
Fig. 5 is blood oxygen probe structure chart of the invention；
Fig. 6 is I/V circuit conversion figure of the invention；
Fig. 7 is circuit of high pass filter figure of the invention；
Fig. 8 is the waveform voltage signal figure of the invention by before high-pass filter；
Fig. 9 is the waveform voltage signal figure of the invention after high-pass filter；
Figure 10 is low-pass filtering figure of the invention；
Figure 11 is the waveform variation diagram of the invention by signal before and after low-pass filter；
Figure 12 is 0809 and STM89C51 single-chip microcontroller wiring diagram of the invention；
Specific embodiment
Presently in connection with Figure of description, the present invention is described further.
Whole principle of the invention is as shown in Figure 1, specifically, operation probe driving circuit first, then passes through sensor
Optical signal is collected, and converts thereof into electric signal, for postorder processing.Current signal is then passed through into a series of processing, it will be electric
Circulation is changed to voltage signal, then goes through high-pass filter except direct current signal, finally after low-pass filter, acquires respective counts
According to come the blood oxygen saturation of extrapolating tester.
It is signal acquisition first, the single-chip microcontroller that the present embodiment uses is STM89C51 single-chip microcontroller, utilizes 51 single-chip microcontrollers
Transmission PWM process control blood oxygen probe light emitting diode takes turns to operate by some cycles.PWM program is strong to noise immunity, control
Circuit processed is simple, at low cost.The method of its specific output pwm signal are as follows: on modulated square wave, by programming, choose proper
It when the period of timer/counter, is controlled using timer/counter and interrupts duration, within a signal period, allowed high electric
Flat, low transition reaches control PWM duty cycle output, completes in a cycle, and low and high level is mutually turned as some cycles
It changes, using pulse width modulating technology, to reach control red light, the infrared lamp function that light on and off are detected in turn.Single-chip microcontroller benefit
Two pwm signals are generated with timer, and pwm signal is accessed in driving circuit designed by project and is carried out at signal amplification
Reason.In order to which red light and infrared lamp can be according to the light on and off in turn of certain period, it is desirable that the PWM programming write according to this method
Duty ratio is 50%, and energy override initial value counts judgement, inverts level, lampet is made to complete red light in a signal generating period
The movement that bright, red light goes out, infrared lamp is bright, infrared lamp goes out.
Driving circuit is substantially power amplification circuit.Because the PWM wave signal power directly exported from single-chip microcontroller is small, it is not enough to
Blood oxygen probe LED light lamp is worked normally, thus needs to design a driving circuit to put to pwm control signal
Greatly, LED power is limited, if power is excessively high, light emitting diode is easy to cause to burn, if power is inadequate, diode
It can not work normally, and corresponding nominal operation environment can be provided for electronic component by driving, according to electronic component
In parallel, series system difference, driving circuit is divided into again provides two kinds of voltage, electric current power amplification circuits.It is red in blood oxygen probe
Lamp and infrared lamp are parallel way, thus require driving circuit that can export larger current.
The driving circuit that the present invention designs is as shown in figure 3, it is because of single-chip microcontroller maximum output 3.3V that power supply, which selects 3.3V,.
So this voltage is determined according to the output voltage of selected single-chip microcontroller, it should be no more than single-chip microcontroller maximum output electricity
Pressure, is typically chosen equal.Symmetrical two triodes Q1, Q2 above circuit can control the friendship of two light emitting diodes
For flashing, because of this switch of two triodes as driving circuit, this is because Q1Q2 is used as switch, when triode is in
When saturation state, triode ON, Vc > Vb and Ve > Vb, i.e. base stage connect low level when triode is in off state, current collection
The disconnection of pole emitter, Vc < Vb and Ve < Vb, i.e. base stage connect the transformation of high level PWM low and high level, and triode is made to be connected and disconnect
Between convert, LED is converted between OFF state lighting, to have the function that switch.
In addition, inputting two complementary pwm signals again, it is the two triode alternate conductions of Q1, Q2, realizes two hairs
The alternating of optical diode (feux rouges, infrared light) flashes.
Two triodes of Q3 and Q4 can control the bright intensity of two light emitting diodes, because the two triodes rise
To the effect of control electric current.
The circuit is run in simulation software, we may safely draw the conclusion: being up to by the electric current of light emitting diode
12.9mA, circuit operation figure are as shown in Figure 3.
The present embodiment is examined using the transmission-type blood oxygen probe that the luminous tube that wavelength is respectively 660nm and 940nm forms
It surveys.Light-emitting diodes tube voltage drop is 1.8V or so, operating current generally in 15mA-20mA, in order to prevent circuit because power it is excessive and
Luminous tube is burnt, resistance of the resistance value between 60-150 Ω range need to be increased.Besides electrical resistance, it is also necessary to use PNP and NPN two
Kind triode, the NPN used here are S8050, and PNP S8550, two kinds of triodes are the difference is that two kinds of materials rows of P, N
Column sequence is different, both triodes play the role of amplifying circuit signal, the Standard resistance range of triode be more than ten kilo-ohms extremely
Between several hundred kilo-ohms, short circuit, also needs to choose the resistance value resistance between 5K-100K Ω partial pressure current limliting work in order to prevent
With.PWM input connects at the PNP pipe base stage of driving circuit upper end, when PWM input low level, QB1 conducting, when PWM input voltage is big
When triode cut-in voltage, electric current will be generated in collector, e emitter is in low potential, and light emitting diode is in positively biased,
Conducting shines.
In order to make two light emitting diode alternating light on and off, we choose STM89C51 single-chip microcontroller to realize the function.C51 is mono-
Piece machine generate two pwm signals, by the Q1 and Q2 being introduced into driving circuit in, achieve the purpose that control signal so that two send out
The lighting timings of light pipe.(feux rouges is opened, and infrared light closes；Infrared light is opened, and feux rouges closes).In the case of breadboardin, timer time is set
Set 50ms.But in practical situations, since circuit requirement LED light flicker cycle is 1ms, timer time setting be should be
0.1ms, therefore the period for generating pwm signal is 1ms.Pwm signal waveform diagram is as shown in Figure 4.
As shown in figure 5, the blood oxygen probe includes U-shaped phototransistor 1, two are provided on the phototransistor 1
To the transmitting light source and photoreceiver 4 of transmission light, two pairs of transmitting light sources and photoreceiver 4 are equidistant and right
Claim setting, two pairs of transmitting light sources are respectively the red light 2 for emitting feux rouges and the infrared lamp 3 for emitting infrared light；Feux rouges 2 or infrared light
It wears and optical signal is received by the photoreceiver 4 of lower section after 3 saturating arterial-venous 5, and be converted to current signal corresponding with optical signal
Output.Blood oxygen probe of the invention is specifically completed using plastic glove and optical filter by reasonable design, and the present invention is all
Plastic glove is generic latex gloves and common ultra thin optical optical filter, and filbtercharacteristic is that black can lead to infrared light (800nm-
1600nm), most of naked eyes visible light (400nm-680nm) percent of pass is only 10%, can completely cut off external light source interference well.
Traditional blood oxygen probe is roomy, and finger easily introduces noise jamming because of activity wherein, and project interception plastic glove finger tip one cuts packet
Blood oxygen probe is wrapped, avoids finger movement from causing distorted signals or introduces interference signal, probe opening is closed using optical filter, prevents
Only external light source interferes.
Followed by current/voltage-converted, is illustrated in figure 6 I/V circuit conversion figure, and the effect of I/V conversion circuit is by light
The electric received photo-signal of receiver is converted into the voltage signal directly proportional to transmitted light intensity, due to actually detected photoelectric current
Very little, usually Naan rank.
Feedback resistance carries out choosing value according to following models:
R1=-U0/is
Wherein, R1For feedback resistance resistance value, for the voltage U to be processed of output0> 0.01V, is are photoelectric current, 1mA > is >
0.01nA；
In view of amplifying circuit and AD conversion etc., output voltage should reach volt grade, feedback resistance in the present embodiment below
Choose 4.7M Ω；A both ends small capacitances in parallel form integrating circuit simultaneously, can further decrease input current noise.In addition
It due to photoelectric current very little, is easy by external interference, it is necessary to select high input resistance, Low-bias Current, low-voltage noise integrates
Operational amplifier.OPA380 is able to satisfy above-mentioned requirements, the accurate transformation of realization electric current to voltage.
It is high-pass filter first, core circuit portions figure by high pass as shown in fig. 7, filter followed by filtering processing
Waveform voltage signal figure before wave device and the waveform voltage signal figure after high-pass filter are as shown in Figure 8 and Figure 9.
Since human pulse signal is quasi-periodic signal, frequency range 0.1-50Hz, dominant frequency component one
As between 0.1-40Hz, the Hz-KHz of system removes 0.1-40Hz, therefore low cut-off in signal conditioning circuit
Frequency presses this Frequency Design.In order to obtain calculate detecting sphygmus and blood oxygen saturation required for alternating component, need to pulse signal into
Row high-pass filtering filters off flip-flop.High-pass filter uses cutoff frequency for the single order passive high three-way filter of 0.8Hz,
Structure is simple, high reliablity.In high-pass filter design, C=10uF, f=0.8Hz are taken, f=1/2 π RC is substituted into and obtains R=20K
Ω。
High-pass filter is made of capacitance-resistance, as shown in fig. 7, circuit is by a 10uF capacitor and 20K Ω resistance
Composition, can filter out direct current signal, and principle is because capacitor has the function of separated by direct communication.Capacitor connects DC power supply
When, charging process only occurs within the of short duration time being just switched on, forms charging current in circuit.After charging, because of electricity
The voltage at container both ends is no longer changed equal to supply voltage, so the electric current in capacitor circuit is zero, is equivalent to capacitor
Device separates DC current, this effect of capacitor is usually referred to as " blocking ".It (is handed over when capacitor connects AC power source
The maximum value of galvanic electricity does not allow more than the rated operational voltage of capacitor), due to AC supply voltage size and Orientation at any time
Between constantly change, capacitor constantly carries out charge and discharge, so will occur charging and discharging currents in circuit repeatedly, is equivalent to exchange
Electric current can be by capacitor, usually this effect of capacitor referred to as " logical to hand over ".
It is shown according to the image of Fig. 9 and Figure 10, after high-pass filter, direct current signal has been filtered out, in circuit
Only remaining ac voltage signal, it is due that this shows that high-pass filter plays the role of it.
It moreover has been found that causing voltage value to decline due to having filtered out direct current signal, this makes the 20K because in bandpass filter
Ω resistance plays decompression, so needing next amplifying circuit to amplify to signal.
Low-pass filter circuit as shown in Figure 10 designs cutting for low-pass filter circuit according to the frequency characteristic of pulse signal
Only frequency is 42Hz.In view of using second-order filter circuit structure simple, and there is good frequency characteristic, therefore can adopt
Second-order low-pass filter is carried out with Butterworth LPF, so as to the amplification and detection of succeeding target signal.Low-pass filter
Design has used OP07AH chip, since its input offset voltage is very low, has low excursion with temperature characteristic, because without additional
Zeroing measure.In the low pass filter, cutoff frequency f=1/2 π RC takes C=0.033uF, then f=42Hz, by C=1uF, f
=40Hz substitutes into f=1/2 π RC, obtains R=22k Ω, filter effect is preferable.
Variation by signal before and after low-pass filter is as shown in figure 11.
Last signal after being filtered, is analyzed and processed to blood oxygen signal in next step.First to collected blood
Oxygen signal is AD converted, and the voltage value for indicating blood oxygen saturation is converted to corresponding digital quantity, in order to monolithic
Machine carries out algorithm analysis to it, and the characteristic signal that will test is analyzed by algorithm to represent and represent human body blood oxygen saturation
Numerical value designs as follows: utilizing AD converter, filter circuit output signal is directly carried out A/D sampling.After sampling, pass through calculation
Method design carries out light beam separation to the pulse blood oxygen signal sampled, pulse wave detects.The key that blood oxygen saturation tests and analyzes
It is that can obtain the waveform diagram for being similar to standard pulse wave, by the period of analysis waveform figure and amplitude, peak value, completes number
Analysis, numerical value is exported to the end LCD or PC via single-chip microcontroller by serial ports show
Signal by filter circuit output is pulse blood oxygen waveform diagram, and standard pulse blood oxygen saturation waveform diagram is as follows: wave
Shape situation can reflect blood of human body mobility status, as ascending branch reflects that the fast rapid fire blood of ventricle, a large amount of blood flow into rapidly dynamic
Arteries and veins blood vessel, expands arterial wall, if ventricular beat is larger, forms ascending branch, penetrates that blood speed is fast, and peripheral resistance is small, then rise
The slope of Zhi You great and big surplus；Conversely, then rising, relatively slow, amplitude is smaller.Decent is ventricle slow ejection period, is entered
The blood volume of aorta is less than the blood volume that periphery is flowed to from aorta, Large artery elasticity retraction, and angioplerosis amount is reduced, and forms decline
Branch.In the moment of aortic valve closing.Because ventricular diastole causes the centripetal room direction reflux of aorta blood, aorta petal is caused
It closes, reflux blood makes aortic root dilatation, and a reflexed wave is formed by the blocking for the aorta petal being turned off,
Decent occur one it is of short duration on to wave, referred to as dicrotic notch.
The light source that blood oxygen probe light emitting diode issues penetrates tissue, and part light source is absorbed by bone, skin etc., and one
Part light source receives transmitted light after blood absorption, by reception pipe, and after blood oxygen saturation is exactly transmitted by this part by blood
Light source calculate analysis obtain.After obtaining waveform, blood oxygen signal exports to 51 single-chip microcontrollers and carries out A/D conversion, believes after through number
It can also be passed through oscillograph, PC machine software through numeral method via the signal processing of a series of complex by number processing module
It is shown as waveform diagram.It for blood oxygen signal waveform diagram, is filtered first, obtains feux rouges, infrared light waveform diagram respectively, cut
Relatively steady waveform diagram is taken, the peak point and valley point of acquisition waveforms are split waveform diagram, accurately obtain a waveform week
Maximum value and minimum value in phase calculate formula according to the blood oxygen saturation in summary of the invention, can calculate blood oxygen levels.In A/
In the design of D conversion, carried out using ADC0809 chip.
The acquisition module groundwork of blood oxygen signal is the waveform diagram acquisition to blood oxygen signal, after collecting waveform diagram, with
Normal human's pulse blood oxygen waveform diagram compares the waveform situation of analysis tester, then calculates principle according to blood oxygen saturation, leads to
The peak value in programming extraction pulse blood oxygen waveform and period are spent, oximetry value is calculated.This step is converted in A/D
In, the present embodiment uses 8 A/D converter ADC0809, and 0809 compared to other ADC converters, and 0809 fast speed is right
Small-signal as pulse blood oxygen, it is more appropriate using Parallel ADC, ADC0809 error between ± 11/4LSB, precision compared with
Height can prevent the occurrence of losing information, causing distortion, cheap, 0809 and STM89C51 single-chip microcontroller wiring such as Figure 12
It is shown.
The above embodiments are only used to illustrate the technical solution of the present invention., rather than its limitations；Although referring to aforementioned each reality
Applying example, invention is explained in detail, those skilled in the art should understand that: it still can be to aforementioned each
Technical solution documented by embodiment is modified, or equivalent substitution of some or all of the technical features；And
These are modified or replaceed, the range for technical solution of various embodiments of the present invention that it does not separate the essence of the corresponding technical solution,
It should all cover within the scope of the claims and the description of the invention.
Claims (7)
1. a kind of SCM Based blood oxygen detection method, it is characterised in that: detection method includes the following steps:
Step 1, blood oxygen signal acquisition: by single-chip microcontroller output pwm signal, believed by the PWM that driving circuit exports single-chip microcontroller
Processing number is amplified, and the signal is transmitted at blood oxygen probe and controls blood oxygen probe and carries out the acquisition of blood oxygen signal collecting work
Blood oxygen photo-signal；
Step 2, blood oxygen signal pretreatment: the blood oxygen photo-signal that step 1 is taken is turned by current/voltage converter circuit
Change voltage signal to be processed into；
Step 3, voltage filter processing: the voltage signal to be processed that step 2 obtains passes through the high-pass filtering of cutoff frequency 0.1Hz
Device filters DC component, retains AC compounent, allows the signal higher than 0.1Hz to pass through, the garbage signal lower than 0.1Hz is shielded；
It then passes through by the second-order low-pass filter that frequency is 20~40Hz, filters out the garbage signal higher than 20Hz, finally obtain 0.1
Effective voltage signal within the scope of~20~40Hz；
Step 4, blood oxygen signal processing: AD converter is utilized, filter circuit output signal is directly subjected to A/D sampling；To sampling
The pulse blood oxygen signal that arrives carries out light beam separation, pulse wave detection obtains waveform diagram, by the period of analysis waveform figure and amplitude,
Peak value completes numerical analysis, is exported numerical value to the end LCD or PC by serial ports via single-chip microcontroller and shown.
2. a kind of SCM Based blood oxygen detection method according to claim 1, it is characterised in that: in the step 1
The process of single-chip microcontroller output pwm signal is as follows: on modulated square wave, choosing the period of certain timer/counter, utilizes timing
Device/counter controls interrupts duration, within a signal period, allows high level, low transition, reaches control PWM duty cycle
Output is completed in a cycle, and low and high level presses the mutual conversion of some cycles.
3. a kind of SCM Based blood oxygen detection method according to claim 1, it is characterised in that: described in step 1
Driving circuit mainly constitutes H-bridge circuit by 4 triodes and forms, and 4 triodes are respectively Q1, Q2, Q3, Q4, Q1, Q2 and monolithic
The pwm signal that machine connection is exported using single-chip microcontroller is as the gating switch of driving circuit, when Q1 is connected, the red light of blood oxygen probe
Bright, when Q2 is connected, the infrared lamp of blood oxygen probe is bright；Q3, Q4 are as the control function of current is played, and wherein Q3 controls the route of conducting
It connects several divider resistances, the route of Q4 control conducting is connected several divider resistances, and 4 triodes are in saturation shape
When state: triode ON, it is desirable that Vc > Vb and Ve > Vb, i.e. base stage connect low level；When triode is in off state: collector
It is disconnected with emitter, it is desirable that Vc < Vb and Ve < Vb, i.e. base stage connect high level.
4. a kind of SCM Based blood oxygen detection method according to claim 1, it is characterised in that: described in step 1
Blood oxygen probe includes U-shaped phototransistor, be provided on the phototransistor two pairs of transmission light transmitting light source and
Photoreceiver, two pairs of transmitting light sources and photoreceiver are equidistant and are symmetrical arranged, and two pairs of transmitting light sources are respectively
Emit the red light of feux rouges and emits the infrared lamp of infrared light；Feux rouges or infrared light are connect after penetrating arterial-venous by the photosensitive of lower section
It receives device and receives optical signal, and be converted to current signal output corresponding with optical signal.
5. a kind of SCM Based blood oxygen detection method according to claim 1, it is characterised in that: described in step 2
Current/voltage converter circuit includes an operational amplifier, and it is collected that the normal phase input end of the operational amplifier meets step 1 institute
Current signal, anti-phase input terminate integrating circuit, and input terminal exports voltage signal to be processed, and the integrating circuit is by a feedback electricity
Hinder and connect the capacitor composition in parallel with feedback resistance in feedback resistance.
6. a kind of SCM Based blood oxygen detection method according to claim 5, it is characterised in that: the feedback resistance
Choosing value is carried out according to following models:
R1=-U0/is
Wherein, R1For feedback resistance resistance value, for the voltage U to be processed of output0> 0.01V, is are photoelectric current, 1mA > is > 0.01nA.
7. a kind of SCM Based blood oxygen detection method according to claim 5, it is characterised in that: the electricity of the capacitor
Capacitance is between 250~290pF.
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| CN110547808A (en) * | 2019-09-24 | 2019-12-10 | 深圳市惟拓力医疗电子有限公司 | Blood oxygen measuring device and system and blood oxygen signal detection method thereof |
| CN110584629A (en) * | 2019-09-23 | 2019-12-20 | 重庆医药高等专科学校 | Working method for acquiring medical data by utilizing single chip microcomputer |
| CN111493889A (en) * | 2020-05-19 | 2020-08-07 | 重庆市计量质量检测研究院 | Detection simulation device for blood oxygen saturation monitor |
| CN114052682A (en) * | 2021-12-14 | 2022-02-18 | 重庆科技学院 | Physiological parameter monitoring system based on raspberry group |
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| CN111493889A (en) * | 2020-05-19 | 2020-08-07 | 重庆市计量质量检测研究院 | Detection simulation device for blood oxygen saturation monitor |
| CN114052682A (en) * | 2021-12-14 | 2022-02-18 | 重庆科技学院 | Physiological parameter monitoring system based on raspberry group |
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| CN114652326A (en) * | 2022-01-30 | 2022-06-24 | 天津大学 | Real-time brain fatigue monitoring device based on deep learning and data processing method |
| CN114652326B (en) * | 2022-01-30 | 2024-06-14 | 天津大学 | Real-time brain fatigue monitoring device based on deep learning and data processing method |
| CN116192257A (en) * | 2022-09-29 | 2023-05-30 | 西安电子科技大学 | Health monitoring and characterization system based on visible light communication and application thereof |
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