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  • PPG foundations

    Follow light through tissue and into a waveform.

    • SpO2Oxygen saturation from red and infrared light
    • Heart rate variabilityWhat beat-to-beat variation can show
    • Interbeat intervalTiming each pulse in the waveform
    • Perfusion indexThe AC/DC ratio as a signal-strength measure
    • Skewness SQIA shape statistic used as a quality index
    • Template matching SQIHow much a beat resembles a reference pulse
    • Pulse transit timePulse timing between two sites
    • Waveform morphologyPeaks, notches and pulse shape
    Algorithms

    Methods for cleaning and interpreting PPG.

    • Bandpass filteringKeeping the cardiac band, dropping drift
    • Dicrotic notch detectionFinding the notch in each pulse
    • Signal quality indexWhether a PPG window is fit for the next vital
    • Adaptive filteringLMS motion-artifact removal
    • Kalman filterTracking heart rate through noise
    • RMSSDThe core short-term HRV statistic
    Charts and conditions

    Reference ranges and where PPG is studied.

    • Resting heart rate chartPercentiles by age and sex
    • What is a good HRV?Normal HRV by age
    • Blood pressure chartWhat the AHA ranges mean
    • Atrial fibrillationRhythm screening with optical sensors
    • Sleep apneaOvernight oximetry and PPG features
    • HypertensionCuffless blood pressure research
    Start hereWhat is photoplethysmography?How a light and a photodetector turn blood volume changes into a pulse waveform.Read the guide
    Popular
    • All PPG algorithms
    • All reference charts
    • How a PPG sensor works
  • Research atlas

    Wearable models, papers and devices in one catalog.

    • ModelsPPG, ECG and motion foundation models
    • Model familiesModels grouped by what they do
    • PublicationsThe papers behind each model
    • DevicesSensors and wearables used in studies
    • AuthorsResearchers and their linked work
    • OrganizationsLabs and companies in affiliations
    Leaderboards

    Ranked within task, dataset and metric.

    • All resultsEvery reported benchmark result
    • Wearable accuracy databasePublished validation results with DOIs
    • rPPG vendor mapCamera vitals vendors by clearance and openness
    • Raw data accessRaw PPG, accelerometer and IBI by wearable
    • FDA clearance database510(k) and De Novo records for PPG and wearables
    • Topic guidesCurated datasets and models by task
    • SnapshotsVersioned, citable copies of the atlas
    Datasets

    Public PPG, ECG and wearable recordings.

    • Research datasetsUsed to train and benchmark models
    • ECG with PPGSynchronized ECG and optical signals
    • Wrist PPGWatch and band recordings
    • Finger PPGPulse oximeter and clinical recordings
    • Open accessNo data use agreement required
    • Blood pressure datasetsCuff and arterial-line references
    Latest leaderboardRppg hrmmpd intra: HR MAE6 results · Updated Nov 12, 2026View leaderboard
    Popular
    • PPG sleep tracking SOTA
    • Sleep staging datasets
    • Activity recognition datasets
    • ECGFounder
    • Pulsewatch dataset
  • Devices

    Optical sensors in watches, rings and bands.

    • Apple Watch
    • Garmin
    • Oura Ring
    • WHOOP
    • Samsung Galaxy Watch
    • Fitbit
    • Polar
    • Sensor Bio
    • Amazfit
    • COROS
    • Empatica
    • Pixel Watch
    • Suunto
    • Ultrahuman
    • Withings ScanWatch
    Accuracy

    Published validation results by metric.

    • Heart rate accuracyWearables against ECG references
    • HRV accuracyValidation studies for HRV
    • Sleep tracking accuracyCompared with polysomnography
    • SpO2 accuracySmartwatch oxygen readings
    • Heart rate app accuracyCamera apps measured against ECG
    Comparisons

    Side-by-side sensors, specs and findings.

    • Garmin vs Apple Watch
    • Withings ScanWatch vs Apple Watch
    • Fitbit vs Garmin
    • Polar vs Garmin
    • Samsung vs Garmin
    • WHOOP vs Oura
    Most comparedApple Watch Ultra vs Garmin FenixBattery, maps, GPS, diving and ECG compared from official specs, with a verdict by use case.See the comparison
    Popular
    • Suunto vs Garmin
    • WHOOP vs Garmin
    • Pixel Watch vs Apple Watch
  • Signal processing library

    Open-source software for wearable signals.

    • PPG toolsPeak detection, HRV and SpO2 code
    • ECG toolsDelineation and rhythm analysis
    • IMU toolsMotion and activity processing
    • Signal qualityQuality indices and artifact checks
    • Dataset loadersReaders for public recordings
    Calculators and checkers

    Agreement statistics and quick interpretations.

    • Validation toolkitAgreement statistics from paired readings
    • Bland-AltmanBias and limits of agreement
    • Bland-Altman sample sizePlan an agreement study
    • ICCIntraclass correlation for reliability
    • Cohen's kappaAgreement for categorical labels
    • Perfusion index checkerInterpret a pulse oximeter PI reading
    • SpO2 at altitudeExpected saturation by elevation
    Interactive and ppg-js

    Simulators and open-source PPG in JavaScript.

    • PlethscapeSimulate how light becomes a PPG signal
    • HRV Spot CheckThe focused ppg-js camera demo
    • Pulse PaintingWatch your pulse become a painted landscape
    • ppg-js quick startScript tag, npm or a React hook
    • API referenceEvents, methods, options and types
    Open-source directoryWearable Signal ToolsOpen-source PPG, ECG and IMU signal processing software, with licence and maintenance shown.265 toolsBrowse the tools
    Popular
    • ppg-js documentation
    • Signal processing packages
    • EDA tools
  • Fundamentals

    How optical pulse sensing works.

    • How a PPG sensor worksLEDs, photodiodes and tissue
    • Reading a PPG waveformThe parts of each pulse
    • Green, red or infraredHow wavelength changes the signal
    • PPG vs ECG accuracyWhere optical timing differs
    • Camera vs contact PPGWhat remote PPG can measure
    Wearables in practice

    What the devices measure, and how well.

    • Best heart rate monitorsPicks by use case, wellness to AFib
    • iPhone camera heart rateHow fingertip camera readings work
    • AFib burden on a smartwatchWhat a watch can and cannot estimate
    • Continuous SpO2 monitoringOvernight and all-day oxygen
    • PPG sleep tracking SOTAStaging kappa, AHI/REI cutoffs, ODI
    Methods and AI

    Signal processing and models, explained.

    • Transformer models for PPGAttention for biosignals
    • Wavelet denoisingRemoving noise across scales
    • Second-derivative PPGThe a-to-e waves and vascular age
    • Powerline notch filtersRemoving 50 and 60 Hz noise
    • Vascular age from PPGArterial stiffness from the waveform
    Newest articleDoes WHOOP Measure Blood Pressure? Accuracy, Calibration and the FDAWHOOP estimates your blood pressure each morning after a cuff calibration. How Blood Pressure Insights works, how accurate it is, and why the FDA stepped in.Nov 12, 2026Read the article
    Popular
    • All articles
    • What is photoplethysmography?
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  4. Nonin 320 pulse oximeter
Nonin 320 pulse oximeter: ChatPPG research summary card

Device research record

Nonin 320 pulse oximeter

  • 1 Datasets
  • 2 Papers
  • 2 Models

Signals and sensors

From the device record. Fields the source does not state are left out.

Maker
Nonin
Form factor
Pulse oximeter (PSG oximetry module)
Signals recorded
PPGSpO₂
Also called
Nonin model 320

Datasets recorded with this device

  • CCSHS (Cleveland Children's Sleep and Health Study, NSRR): in-lab PSG with finger pleth in a pediatric/adolescent cohort (907 children)907 subjects · PPG · ECG · SpO₂

Models trained or evaluated on its data

Models whose published training or evaluation datasets include recordings from this device.

  • AnySleep (FH Aachen; channel-agnostic EEG/EOG sleep stager, npj Digit Med 2026)EEGEOG2026 · Open weights
  • LPSGM (Large PSG Model; flexible-channel EEG/EOG/EMG sleep staging + clinical screening; ZJU / Hangzhou Seventh People's Hospital)Foundation modelEEGEMGEOG2026 · Open weights

Papers using these datasets

  • AnySleep: a channel-agnostic deep learning system for high-resolution sleep staging in multi-center cohortsnpj Digital Medicine · 2026
  • A Unified Flexible Large Polysomnography Model for Sleep Staging and Downstream Clinical Screening (LPSGM)medRxiv preprint · 2024

Browse the device database →

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Research

Research atlasGraph explorerLeaderboardsDatasetsModelsPapersDevicesAuthorsOrganizationsWearable accuracy

Understand

Learn PPGSignal processingReference chartsApplicationsWearables & comparisonsThe libraryWhat is PPG?

Tools

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Popular guides

Accuracy comparisons, signal explainers, and the best public datasets by task.

Wearable accuracy

8 guides
Heart rate app accuracyApple Watch vs chest strapSkin tone & HR accuracyPolar vs smartwatchHow accurate is Oura Ring?Active caloriesPPG vs ECG accuracyClinical vs consumer PPG

Blood pressure & rhythm

10 guides
Wrist BP monitorsABPM vs smartwatchWhite-coat vs masked HTNMasked hypertension & wearablesSmartwatch AF vs HolterSpO₂ in heart failureHome sleep apnea testWhat is AHI?Central sleep apneaWhat is a hypopnea?

PPG & signal science

14 guides
How a PPG sensor worksGreen vs red vs IRReflectance vs transmittanceRing vs wrist PPGrPPG vs contact PPGRemote PPG accuracy factorsLMS / NLMS adaptive filtersSTFT heart-rate trackingArterial-line waveformsNon-invasive hemoglobinPPG sensor designRead a PPG waveformSignal quality indexWearable SpO₂ accuracy

Dataset guides

10 guides
Blood pressure datasetsAtrial fibrillation datasetsFoundation-model pretrainingSpO₂ & skin-tone fairnessHeart rate under motionPPG sleep tracking SOTASleep staging datasetsGlucose & metabolicStress & emotionActivity recognition
See all guides →

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