Yuav ua li cas txhawm rau ntsuas qhov tseeb ntawm diodes hauv oximeter circuits?

1, Dual wavelength LED: lub hauv paus pob zeb ntawm cov cim cim cim
Lub oximeter txais lub teeb ci dual wavelength LED nrog 660nm lub teeb liab thiab 940nm infrared lub teeb, thiab nws cov qauv tsim yog raws li qhov sib txawv ntawm cov yam ntxwv nqus ntawm hemoglobin (Hb) thiab oxygenated hemoglobin (HbO ₂) rau qhov sib txawv wavelengths ntawm lub teeb. Tshwj xeeb:

660nm lub teeb liab: HbO ₂ nqus tus nqi qis, Hb nqus tus nqi siab, thiab cov teeb liab siv tsis zoo cuam tshuam nrog cov ntsiab lus ntawm cov hlab ntsha oxygen;
940nm infrared lub teeb: HbO ₂ nqus tus nqi siab dua Hb, thiab cov teeb liab siv tau zoo cuam tshuam nrog cov ntsiab lus ntawm cov hlab ntsha oxygen.
Cov ntsiab lus tseem ceeb ntawm kev siv technology:

Kev tswj lub sijhawm: Tsav lub LED kom hloov pauv (feem ntau ntawm 100-500Hz) los ntawm H-bridge circuit kom tsis txhob muaj kev cuam tshuam ntawm ob lub teeb liab. Piv txwv li, ib qho qauv ntawm oximeter siv MSP430 microcontroller's PWM teeb liab los tswj LED tsav nti, ua tiav cov teeb pom kev sib hloov ntawm lub teeb liab thiab infrared ntawm lub sijhawm ntawm 0.5ms.
Tsis tu ncua tsav tam sim no: siv qhov tam sim no qhov chaw Circuit Court kom ruaj khov LED luminous siv thiab tshem tawm qhov cuam tshuam ntawm cov khoom siv hluav taws xob hloov pauv ntawm lub teeb siv. Lub chaw kho mob qib oximeter siv qhov ntsuas qhov ntsuas qhov tseeb (xws li 0.1% qhov tseeb) thiab lub tshuab ua haujlwm ua haujlwm los tsim lub voj voog tawm tswv yim, tswj LED tam sim no hloov pauv hauv ± 0.5%.
Lub teeb siv lub teeb calibration: Nyob rau hauv cov txheej txheem ntau lawm, LED tso zis lub teeb siv tau hloov kho los ntawm cov ntxaij lim dej kho qhov muag kom phim lub teeb liab amplitudes ntawm ob lub wavelengths thiab txhim kho qhov ntau yam ntawm cov teeb liab tom ntej. Piv txwv li, lub portable oximeter siv ib tug integrating sphere calibration system los tswj qhov sib piv ntawm liab thiab infrared teeb ntawm 1: 1.2 ± 0.05 ua ntej tawm hauv lub Hoobkas.
2, Photodiode: lub hauv paus ntawm siab -sensitivity photoelectric hloov dua siab tshiab
Photodiodes yog lub luag haujlwm los hloov cov teeb liab teeb liab kis los ntawm cov ntiv tes mus rau hauv cov teeb liab hluav taws xob, thiab lawv qhov kev ua tau zoo cuam tshuam ncaj qha rau cov teeb liab - rau - suab nrov piv (SNR). Qhov tseem ceeb technical parameter muaj xws li:

Teb wavelength ntau: Nws yuav tsum tau npog 400-1050nm los teb rau ob lub teeb liab thiab infrared ib txhij;
Teb ceev: Lub sijhawm nce yuav tsum tsawg dua 1 μs txhawm rau ntes me me hloov pauv hauv cov mem tes tsis;
Tsaus tam sim no: Nws yuav tsum qis dua 0.1nA txhawm rau txo qhov cuam tshuam ib puag ncig.
Cov ntawv thov raug:
Ib qho kev kho mob qib oximeter siv OSRAM SFH 2701 photodiode. Thaum qhov thim rov qab yog 5V, qhov tsaus nti tam sim no tsuas yog 0.05nA, thiab lub luag haujlwm ncav cuag 0.55A / W ntawm 940nm. Cov cuab yeej ua tau zoo txhim kho nws qhov siab - zaus teb muaj peev xwm los ntawm kev ua kom zoo dua PN hlws ris qauv thiab txo qhov kev sib tshuam capacitance mus rau 1.7pF.

Cov ntsiab lus tseem ceeb ntawm kev tsim Circuit Court:

Trans impedance amplifier (TIA): hloov cov teeb liab tsis muaj zog tam sim no (feem ntau 0.1-10 μ A) ntawm photodiode rau hauv lub teeb liab voltage. Piv txwv li, ib qho kev tsim qauv siv AD8065 ua haujlwm amplifier los tsim TIA, nrog kev tawm tswv yim tawm tsam ntawm 1M Ω, ua tiav kev hloov pauv nce ntawm 0.1V / μ A.
Environmental light suppression: Dual suppression of environmental light interference is achieved through optical filters (xws li 660nm thiab 940nm bandpass filters) thiab circuit filters (xws li RC low -pass filters). Kev sim cov ntaub ntawv qhia tau hais tias cov tswv yim no tuaj yeem txo 50Hz fais fab zaus cuam tshuam los ntawm 40dB.
Kev them nyiaj kub: Ib qho NTC thermistor yog sib xyaw ua ke ntawm ib sab ntawm lub photodiode, thiab TIA nce tau raug kho nyob rau hauv tiag - sij hawm los ntawm microcontroller los them rau qhov kub thiab txias drift. Piv txwv li, ib qho kev tsim qauv tswj cov zis hluav taws xob hloov pauv hauv ± 0.5% hauv thaj tsam ntawm -20℃txog 50 degree.
3, Kev Tiv Thaiv Tsis Txaus Ntshai: Tag Nrho Txuas Kev Txhim Kho los ntawm Hardware mus rau Algorithm
Lub teeb liab ntawm lub oximeter muaj ntau qhov chaw ntawm lub suab nrov, uas yuav tsum tau suppressed los ntawm kev kho vajtse thiab algorithm kev sib koom ua ke:

Hardware filtering:
Preamplification: Tsawg- suab nrov ua haujlwm amplifier (xws li OPA2333, nrog lub suab nrov input voltage tsuas yog 3.5nV / √ Hz) yog siv los tsim TIA thiab txo cov suab nrov thermal;
Bandpass filtering: Extract pulse wave signals ntawm 0.7-3Hz los ntawm ib thib ob-order low-pass filter (txiav-tawm zaus 11.25Hz) thiab thawj-order high pass filter (cut-off zaus 0.0159Hz);
50Hz notch: siv dual T network los yog active filtering Circuit Court los suppress hwj chim zaus cuam tshuam.
Digital filtering:
FIR lim: siv los tshem tawm siab - suab nrov zaus thiab khaws cov mem tes yoj nta;
Adaptive filtering: dynamically kho cov lim coefficients los ntawm LMS algorithm los suppress cov khoom cuav. Ib qho kev sim cov ntaub ntawv qhia tau hais tias cov tswv yim no tuaj yeem txo qhov kev ntsuas qhov yuam kev los ntawm kev cuam tshuam los ntawm ± 5% mus rau ± 1.5%.
4, Dynamic nyiaj them: hloov mus rau txawv physiological thiab kev siv scenarios
Txhawm rau txhim kho kev ntsuas thoob ntiaj teb, oximeter yuav tsum tau them nyiaj rau cov xwm txheej hauv qab no:

Cov tawv nqaij xim sib txawv: Cov tawv nqaij tsaus muaj zog nqus ntawm lub teeb thiab yuav tsum tau them nyiaj rau cov teeb liab attenuation los ntawm kev kho cov LED tsav tam sim no (xws li nce ntawm 5mA mus rau 10mA) lossis TIA nce. Ib qho kev tsim qauv siv lub microcontroller los saib xyuas cov zis hluav taws xob ntawm photodiodes hauv lub sijhawm tiag tiag thiab hloov kho qhov nce coefficient.
Tsawg perfusion xeev: poob siab lossis hypothermia ua rau txo qis hauv pulse nthwv dej amplitude, thiab lub teeb liab - rau - suab nrov piv yuav tsum tau txhim kho los ntawm kev nce tus nqi piv txwv (xws li los ntawm 100Hz mus rau 500Hz) thiab ncua sij hawm kev sib koom ua ke (xws li los ntawm 100ms mus rau 500ms). Ib txoj kev tshawb fawb soj ntsuam tau pom tias txoj hauv kev no tuaj yeem nce qhov kev ntsuas kev ua tau zoo ntawm cov neeg mob uas tsis tshua muaj perfusion los ntawm 75% mus rau 92%.
Kev sojntsuam tshem tawm: Los ntawm kev saib xyuas cov kev hloov pauv hauv lub teeb liab amplitude (xws li qhov txo qis dua 30%), lub tswb tau tshwm sim los ua kom tus neeg siv rov kho qhov kev sojntsuam. Lub portable oximeter integrates ib tug acceleration sensor thiab ntxiv suppresses displacement cuam tshuam los ntawm kev tshawb nrhiav algorithms.
5, Clinical validation thiab tus qauv ua raws
Kev kho mob qib oximeters xav tau kev soj ntsuam nruj nruj thiab kev ua raws li tus qauv:

Cov ntaub ntawv kho mob haum: Tsim ib daim ntawv qhia nkhaus ntawm R tus nqi (lub teeb liab rau lub teeb infrared AC / DC teeb liab piv) thiab SpO ₂ raws li cov ntaub ntawv tuaj yeem pab dawb. Piv txwv li, calibration nkhaus ntawm ib qho qauv ntawm oximeter npog thaj tsam ntawm SpO ₂ 70% -100%, nrog qhov yuam kev siab tshaj plaws tsawg dua lossis sib npaug li 2%.
IEC 60601-2-20 tus qauv: yuav tsum muaj lub teeb ci LED tsis pub tshaj 10mW / cm² kom tsis txhob muaj tawv nqaij kub hnyiab; Nyob rau tib lub sijhawm, nws tau teev tseg tias qhov kev ntsuas qhov yuam kev yuav tsum tsis pub tshaj ± 3% hauv thaj tsam ntawm SpO ₂ 70% -100%.