Q. How does the Actiwatch work?

A. The Actiwatch is a wrist-worn device containing a miniature uniaxial Accelerometer that produces a signal as the wearer makes physical movement. This signal is measured 32 times per second and processed to provide the digital integration of the amount and duration of movement. The data is then stored within the Actiwatch in non-volatile memory ready for download and analysis.

Q. How Sensitive is the Actiwatch?

A. The Actiwatch will record all movement over 0.05g. The Actiwatch has filters to exclude readings outside the 3-11Hz range. This helps to eliminate gravitational artifacts.

Q. Can the Actiwatch only be worn on the wrist?

A. Because of its small physical size and weight, it is possible to mount the Actiwatch in alternative ways. For example, the PLMS (Periodic Limb Movement in Sleep) analysis requires that an Actiwatch be mounted across the toes of each foot. The quantity, frequency and intensity of kicks are then recorded and may be analysed using the PLMS software.

Q. How long does the battery last?

A. Battery life is dependent upon the type of Actiwatch - the new Actiwatch 7 has battery life of 8 years in continuous use.  It is typically six months for the Actiwatch AW4 and 18 months for the Actiwatch Mini. The battery in the AW4 is a CR2025 coin cell that is readily available from most chemists or photographic shops.

Q. Is the battery easy to change?

A. The Actiwatch 7 requires that the battery is replaced by Cambridge Neurotechnology at the end of 8 years to retain waterproofing and shock-resistance.  The Actiwatch 4 and Mini have been designed to allow easy removal and re-fitting of the battery by the user.

Q. Will I lose my data if the battery runs down?

A. No, the activity data and user settings are all stored in non-volatile memory.

Q. How do I read the data from my Actiwatch?

A. The complete Actiwatch system comprises of one or more Actiwatches, an Actiwatch Reader, a personal computer and some software. The Actiwatch Reader simply connects to the serial (RS232) port of your computer and the Actiwatch is placed, 'face down' onto the Reader. The software allows communication to take place with the Actiwatch to read data or send settings. There are no physical connections between the Actiwatch and the Reader that could compromise the waterproof seals such as with other types of Actigraph.

Q. What type of Personal Computer do I need?

A. Any IBM Compatible PC with Windows NT, 2000 or XP. You will require 100MB of free hard disk space and a CD-ROM drive to load the software. A 9-pin or 25-pin RS232 (serial) port is required to connect the reader. It is recommended that a minimum display resolution of 800x600 pixels be used.

Q. Can I use the data in other applications (e.g. spreadsheets)?

A. Yes, the data is stored as comma separated values in ASCII format. Data can be copied to the clipboard and then simply pasted into other applications as required.

Q. What do the readings mean?

A. The readings are activity counts over a specified time period (epoch). There are approximately 25 counts to 1g.