Continuous Body Monitoring - Ambient Intelligence for Scientific Discovery - page 208

Table 1. Detailed specifications for the SenseWear II armband.

Dimensions and weight
(l) 85.3mm x (w) 53.4mm x (h) 19.5mm. Weight 85g.
(l) 3.4” x (w) 2.1” x (h) 0.8”. Weight 3.0 oz

Mechanical
Medical Device Grade ABS - monitor top and skin-touching bottom.
UV-stabilized Thermoplastic Urethane(TPU) - flexible wings, overmolded
to monitor top.
FDA-registered co-polyester - skin touching label covers screws providing
asmoothinterfacetoskin.
Surgical grade stainless steel 304 - external sensors, progressive stamped
and insert molded to bottom.
Custom designed non-latex elastic - adjustable strap.

Hardware
Battery - 1 AAA, up to 14 days continuous use (24/7).
Memory - 512Kbytes of flash data storage, up to 14 days continuous use
(24/7) in standard configuration.
Processor - low power 16 bit w/integral program flash, scratch RAM,
A/D, and peripheral support.
USB - USB 2.0 interface with drivers for Windows 98, ME, 2000, and
XP.
Wireless - ISM band 916.5MHz radio transceiver for wireless communi-
cation.

Sensors
Accelerometer - 2-axis MEMs device
Heat Flux - patented configuration of injection molded heat pipe, sensor,
and differential amplification
Galvanic skin response - symmetrical stainless steel pads insert molded
into the ABS bottom
Skin temperature - thermistor-based sensor assemblies

indicator of evaporative heat loss by identifying the onset, peak and recovery of
maximal sweat rates. The GSR circuit records skin resistance to a high degree of
accuracy over a wide range of values, with a 2.5nSiemen maximum error up to
100nSiemens, and a 2.5% maximum error otherwise. Typically minute averages
in GSR show small changes from minute to minute. Subtle physiological effects
can be seen in GSR at higher sampling rates.

Skin Temperature. Skin temperature is measured using a highly accurate
thermistor-based sensor located on the backside of the armband near its edges
and in contact with the skin. Continuously measured skin temperature is ap-
proximately linearly reflective of the body's core temperature. The skin temper-
ature sensor has a resolution

0.05 degrees Celsius and is accurate to 0.5 ◦ C <