How to use Light and Temperature data?
The light sensor on the AX3 is a logarithmic lux sensor that has a wavelength characteristic close to that of the human eye. Without calibration the sensor can only be used qualitatively due to part variations; That is, comparison between devices is not possible. This is mainly because the sensor output is effected by the light attenuation of its particular enclosure, but also due to the variability of the sensor component. Some level of calibration is essential if the output is to be used quantitavely and to allow comparison between devices. The calibration must take into account the non-linear aspect of the logarithmic sensor and this should use the equation below which approximates the lux level at the sensor surface. A reasonable calibration can then be achieved by applying a coefficient to the approximated lux to take into account the linear attenuation of the enclosure. When measuring this coefficient the user should ensure that they choose a calibration point in the middle of the device operating range and use an incandescent light source. A suggested operating point would be 1k lux.
lux = 10^(COUNTS/341)
The temperature sensor is mounted on the PCB and thus does not provide a true measure of skin temperature. However, its output may be converted to ℃ using the equation below.
T = (COUNTS - 171)/3.413