Click on Sea-Bird's Application Note 11S for questions using the Biospherical Surface PAR sensor with the Sea-Bird SBE deck unit. In addition, you can search the Sea-Bird website for “Biospherical” for other application notes regarding integrating Biospherical sensors with Sea-Bird equipment.
A full discussion of PAR can be found in BSI's Application Note "Light Quantities, Units, and Conversion Factors."