ActiGraph GT9X (Link), GT3X+, ActiSleep+, wGT3X+, and wActiSleep+ devices are designed to preserve battery life when the device is idle (not experiencing movement). This feature, often referred to as "Idle Sleep Mode" can be enabled or disable upon initialization. Below is a description of the device's behavior with Idle Sleep Mode enabled and disabled.
When Idle Sleep Mode is disabled, the device collects data at the desired sample rate without entering any idle state. Each sample stored in the devices memory represents the exact reading from the internal accelerometer for the entire duration of data collection. Chart 2 in the help thread Battery Life vs Memory Recording Limits for GT3X+ series shows the expected battery life for GT3X+ devices under this condition (wGT3X+ battery life information coming soon).
Devices with Idle Sleep Mode enabled will enter a sleep or low power state after experiencing 10 seconds of inactivity (fluctuation on the accelerometer < +/- 40 milliGs). After entering this low power state, the device checks once every second to determine if the unit has moved. While in sleep mode, the last sampled accelerometer value is written into memory at the device's preset sample rate. [For example, a device set to sample at 30Hz would store the last known accelerometer reading 30 times every second; the device would then wake up and check for movement. If no movement were detected, this pattern would continue. Otherwise the unit would exit sleep mode (i.e., "wake up") and continue sampling in normal fashion.] After filtering (conversion to *.agd), this data becomes 0 counts since no movement is detected during this time period.
During low power state, the LED will stop flashing on devices that have the "flash LED during data collection" feature enabled.
LUX Data Collection
Because lux data is recorded every one (1) second regardless of the selected frequency of actigraphy data collection, lux data is continually stored even during low power state. That is, lux data storage is unaffected by the Idle Sleep Mode functionality
Idle Sleep Mode has no effect on the wireless functionality for wGT3X+ or wActiSleep devices. More information on the estimated power savings and battery life impact of Idle Sleep Mode can be found at Battery Life vs Memory Recording Limits for GT3X+ series.
If you need any further assistance, please go to our support portal at https://help.theactigraph.com/home. From here, you can view many helpful FAQ's and Troubleshooting Articles; log in to check any existing Support Requests; or create a new Support Ticket if you are unable to find a solution. You can also email us at firstname.lastname@example.org or give us a call at (877) 497-6996, Monday through Friday, 8 am to 5 pm CST.