The back-scattering measurements are a portion of the total beam attenuation coefficient of the water being sampled. The beam attenuation is measured during the back-scattering calibration. Therefore, the range specification on the data sheet for the BB sensor (0 – 3 or 0 – 5 m^-1) refers to the beam attenuation coefficient range of the calibration.
There is a note on the data sheet that further explains the backscattering specification:
*Backscattering specifications are given in beam cp (m^-1) based on the regression of the response of the instrument relative to the beam cp measured at the coincident wavelength using an ac-s spectrophotometer. Scale factors for backscattering incorporate the target weighting function and the solid angle subtended.