NIRStar 14.1 - User Manual
Page 82 of 124
16.1.3 Dynamic Range Consideration: Detector Gain and Source Amplitude
In addition to the detector gain switching mechanism, by which NIRSport achieves a dynamic measuring
range of approximately 1:10
5
, a new LED intensity adjustment was implemented to prevent situations of
detector saturation.
Depending on the chosen target site, probe configurations, or subject populations one may encounter
situations in which a rather strong light transmission could cause detector saturation, which, if not
accounted for, can lead to signal distortion or loss. Examples are prefrontal measurements, layouts
utilizing short source-detector distances (< 2.5 cm), or measurements on children. To avoid potential
detector saturation, prior to the gain setting procedure, NIRStar will automatically perform an LED
intensity optimization. The procedure consists of illuminating the target at the lowest LED intensity and
evaluating the signals received at the lowest gain settings. The LED intensity is then incrementally
increased until a satisfactory signal level is obtained, or the highest permissible LED current is reached.
The LED adjustment covers an illumination intensity range of 1:100.
During this procedure, a waiting bar informs the user of the progress.
This is immediately followed by the gain calibration process, as indicated by another waiting bar display.
Figure 58. Low levels of battery charge and alert messages. Left: Level <= 50%; Right: Level <= 25%.
L
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