The GT3X+ is an accelerometer manufactured by Actigraph (Pensacola, Florida, USA) released in 2010.

The device uses a capacitive triaxial Microelectro-Mechanical-System (MEMS) accelerometer which records accelerations with dynamic range ±6 g. The sampling rate is user defined at 10 Hz increments between 30 Hz to 100 Hz. Th device also collects ambient light data in Lux at a sampling rate of 1 Hz.

Battery life and storage capacity are dependent upon sampling rate (e.g. 22.5 days battery and 42.5 days memory at 30 Hz with 24 hour continuous activity).

Output is available in both the pre-filtered raw format (g), and in propietary activity counts at a user defined epoch derived using Actilife software, also produced by Actigraph. The device also uses data from all three axes to distinguish different postures (non-wear, standing, lying, sitting). Data from the verical axis are used to estimate step counts.

The GT3X+ features a Low Frequency Extension option, which increases sensitivity to very low amplitude activities allowing for the study of population groups who move slowly or take very light steps (for example, the elderly).

The device is attached to the body using a strap and can be attached at a variety of wear locations, for example the wrist, waist, arm or ankle.

Component	Detail
Sample Rate	30-100 Hertz
Battery Life	30 days
Axes	3
Weight	19 g
Size	46 mm * 33 mm * 15 mm
Memory	512 MB
Battery life	31 days
Dynamic range	±6 g

Output variable	Units
Acceleration	g
ActiGraph counts	Counts per user defined epoch (e.g. counts per minute)
Steps	Steps per user defined epoch (e.g. steps per minute)
Posture	1) Device off; 2) Standing; 3) Lying; 4) Sitting

Resource	Link
User guide	External site (PDF)
Firmware	External site
ActiLife Software	External site

Lifestage	Reliability and validity literature
Adults	External site
Infants	External site
Older adults	External site

First author (year)	Title
Brazendale et al. (2017)	External site