---
title: activePhotodiodeIndexes
framework: sensorkit
role: symbol
role_heading: Instance Property
path: sensorkit/srphotoplethysmogramopticalsample/activephotodiodeindexes
---

# activePhotodiodeIndexes

The set of photodiodes in use during the sample.

## Declaration

```swift
var activePhotodiodeIndexes: IndexSet { get }
```

## Discussion

Discussion To map the spatial location of the active photodiodes, see the Apple Watch diagrams in Interpret second-generation PPG sensors data and Interpret third-generation PPG sensors.

## See Also

### Accessing optical data

- [emitter](sensorkit/srphotoplethysmogramopticalsample/emitter.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)