Our Low Frequency Extension (LFE) filter is designed to detect lower amplitude movements over our standard filter. The sensitives of solid state MEMS accelerometers like the one utilized in ActiGraph's products are very high and can detect even the most minute of movements (+/- 6G's for our GT3X+/wGT3X+/ActiSleep+/wActiSleep+ devices and +/-3G's for our legacy products).
Because we are only interested in movements that are attributable to human activity and not minor vibrations found in our everyday environment, we have an internal acceleration threshold that must be crossed before we consider it human movement related and as a result, record it. This threshold limits the ability of the device to measure movement of populations such as the elderly or any population that is very slow and/or exhibits very low acceleration outputs.
In order to combat this, and in order to provide researchers the ability to gather useful information about this subject group we have provided the LFE which reduces this threshold. The net effect is that the reduced amplitude movements are now recognized and recorded, yielding information of value.
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 email@example.com or give us a call at (877) 497-6996, Monday through Friday, 8 am to 5 pm CST.