Brookfield viscosity is measured in Centipoise (cP), which is absolute viscosity
Absolute viscosity (cP)= Kinematic viscosity (cSt) X Specific Gravity
The Brookfield apparatus uses a rotating spindle, the torque applied is measured and determines the viscosity This type of apparatus works particularly well for low temperature testing
As Badenewsbare correctly states Brookfield is usually a low temperature viscosity measurement, almost entirely used on new oil to confirm the SAE W viscosity rating. Also on ATFs (Dexron/Mercon) to confirm max viscosity requirements at the stated temerature(-40C) Low tempearture performance is affected by pour point/VI and base fluid selection. A lab would generally not conduct a Brookfield on used oil because of solids contamination damaging the equipment.