The tension of the water at the upper plastic limit is equivalent to pF value

The liquid limit (LL) or upper plastic limit is the e-water content at which the soil changes from a liquid state to an aplastic state.
The pF value is a quantity that indicates the quality of water contained in the soil. A pF value near 0 indicates that the soil is filled with water.
For the upper plastic limit or liquid limit, the pF value is 0.5.