---
title: SRPhotoplethysmogramOpticalSample
framework: sensorkit
role: symbol
role_heading: Class
path: sensorkit/srphotoplethysmogramopticalsample
---

# SRPhotoplethysmogramOpticalSample

A data sample from the photoplethysmogram (PPG) optical sensor.

## Declaration

```swift
class SRPhotoplethysmogramOpticalSample
```

## Overview

Overview To get the PPG waveform, use the normalizedReflectance property. Apple Watch uses an arrangement of emitters and photodiodes to measure the PPG waveform. Interpret second-generation PPG sensors data Second-generation optical heart sensors, in Apple Watch 4, 5, SE 3 and SE models, use green or infrared (IR) LED lights paired with light-sensitive photodiodes. The active photodiode’s indices show which photodiode or combination of photodiodes the Apple Watch uses. The light-sensitive photodiodes have different arrangements between the Apple Watch models: For the second-generation sensors, the mapping of the optical heart sensor (SE, Series 4 and 5) emitter is:  |   |   |   |   |   |   |  Interpret third-generation PPG sensors Third-generation optical heart sensor, in Apple Watch Series 6 and later, plus Apple Watch Ultra and Ultra 2, use an additional red LED with a different arrangement of emitters and photodiodes than the second-generation PPG sensors. The active photodiodes indices show which photodiode or combination of photodiodes the Apple Watch uses.

For the third-generation sensors, the mapping of the optical heart sensor (Series 6, 7, 8, 9, Ultra, and Ultra 2) emitter is:  |   |   |   |   |   |   |   |   |   |   |   |   |   |

## Topics

### Accessing optical data

- [emitter](sensorkit/srphotoplethysmogramopticalsample/emitter.md)
- [activePhotodiodeIndexes](sensorkit/srphotoplethysmogramopticalsample/activephotodiodeindexes.md)
- [signalIdentifier](sensorkit/srphotoplethysmogramopticalsample/signalidentifier.md)
- [nominalWavelength](sensorkit/srphotoplethysmogramopticalsample/nominalwavelength.md)
- [effectiveWavelength](sensorkit/srphotoplethysmogramopticalsample/effectivewavelength.md)
- [samplingFrequency](sensorkit/srphotoplethysmogramopticalsample/samplingfrequency.md)
- [nanosecondsSinceStart](sensorkit/srphotoplethysmogramopticalsample/nanosecondssincestart.md)
- [conditions](sensorkit/srphotoplethysmogramopticalsample/conditions.md)
- [SRPhotoplethysmogramOpticalSample.Condition](sensorkit/srphotoplethysmogramopticalsample/condition.md)
- [noiseTerms](sensorkit/srphotoplethysmogramopticalsample/noiseterms-swift.property.md)
- [SRPhotoplethysmogramOpticalSample.NoiseTerms](sensorkit/srphotoplethysmogramopticalsample/noiseterms-swift.struct.md)
- [normalizedReflectance](sensorkit/srphotoplethysmogramopticalsample/normalizedreflectance-15f2k.md)

## Relationships

### Inherits From

- [NSObject](objectivec/nsobject-swift.class.md)

### Conforms To

- [CVarArg](swift/cvararg.md)
- [CustomDebugStringConvertible](swift/customdebugstringconvertible.md)
- [CustomStringConvertible](swift/customstringconvertible.md)
- [Equatable](swift/equatable.md)
- [Hashable](swift/hashable.md)
- [NSCoding](foundation/nscoding.md)
- [NSCopying](foundation/nscopying.md)
- [NSObjectProtocol](objectivec/nsobjectprotocol.md)
- [NSSecureCoding](foundation/nssecurecoding.md)
- [Sendable](swift/sendable.md)
- [SendableMetatype](swift/sendablemetatype.md)

## See Also

### Accessing PPG data

- [startDate](sensorkit/srphotoplethysmogramsample/startdate.md)
- [nanosecondsSinceStart](sensorkit/srphotoplethysmogramsample/nanosecondssincestart.md)
- [usage](sensorkit/srphotoplethysmogramsample/usage-swift.property.md)
- [SRPhotoplethysmogramSample.Usage](sensorkit/srphotoplethysmogramsample/usage-swift.struct.md)
- [opticalSamples](sensorkit/srphotoplethysmogramsample/opticalsamples.md)
- [accelerometerSamples](sensorkit/srphotoplethysmogramsample/accelerometersamples.md)
- [SRPhotoplethysmogramAccelerometerSample](sensorkit/srphotoplethysmogramaccelerometersample.md)
- [temperature](sensorkit/srphotoplethysmogramsample/temperature.md)