Immediately prior to each sensor test the spectrometer within The Lightman is
calibrated against a neon argon source. During production of the Lightman and at
annual recalibration the intensity correction is achieved through using a
calibrated light source supplied by NPL. The Lightman spectrometer collects the
complete spectral output throughout the range 450 nanometres to 1100 nanometres.
The data is analysed to provide the centre of gravity wavelength of each LED.
The implications of wavelength errors for pulse oximeter accuracy for
the red and infrared are treated separately at SATs values of 97%, 90%, 80%, and
70%. The consequential errors in SATs values were calculated separately for the
red and infra red at each SATs value and then summated. So for example a
positive error in one wavelength could reduce the error in the other wavelength.
The resultant effect of wavelength errors on the SATs value that would be
displayed on the monitor at patient SAT values of 97%, 90%, 80%, and 70% are
displayed on the Lightman screen
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