Accelerometer (lamp.accelerometer)

Records device acceleration in three axes. Units are g (multiples of gravitational acceleration, where 1 g ≈ 9.81 m/s²). At rest with the screen facing up, the z-axis reads approximately -1.0 g. The coordinate plane is relative to the device.

Configuration

• SensorSpec: lamp.accelerometer
• Sampling: Discrete (default 5 Hz — 5 samples per second)
• Platform: iOS, Android
• Permissions: Motion & Fitness required

Configure sampling rate via the API.

API settings fields

Setting	API Field	Type	Default	Max
Sampling Rate	frequency	number (Hz)	5	5

Quality Factors

• Motion & Fitness permissions must be granted.
• Battery optimization can restrict background sensor access.
• Higher sampling rates produce more granular data but consume more battery.

Usage

Accelerometer data is collected continuously in the background. No participant action is required.

note

On Android, accelerometer data may be delivered inside a DeviceMotion-style structure with a motion sub-object. Cortex normalizes this automatically. The data format described here is the canonical iOS format.

Data

Fields

Field	Type	Unit	Description
x	float	g	Acceleration on x-axis (left to right across the screen)
y	float	g	Acceleration on y-axis (bottom to top of the screen)
z	float	g	Acceleration on z-axis (out from the screen toward the user)

Example

{
  "timestamp": 1649859212042,
  "sensor": "lamp.accelerometer",
  "data": {
    "x": 0.19378,
    "y": 1.28474,
    "z": -0.19385
  }
}

Cortex Features

accelerometer (raw) → acc_jerk (primary) → inactive_duration (secondary)

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