The Aquadyne DVS is a fully automated, gravimetric, dual sample water vapor sorption analyzer. It measures adsorption and desorption isotherms of water vapor both accurately and sensitively, including sorption kinetics, with minimal operator involvement. The weight(s) of one or two sample(s) is/are constantly monitored and recorded as the relative humidity is automatically varied by the blending of dry carrier gas with a saturated gas stream. The dual balance design allows increased analysis throughput, side-by-side comparison with known or reference materials, or an extended mass range for a single sample. The independently temperature-controlled balance head environment ensures long term stability. The small sample chamber ensures rapid changes in sample atmosphere conditions when the relative humidity is altered during an analysis. Samples can be pre-dried in situ at up to 80degC in a flow of dry gas. The software supports multiple users with password-controlled access.