Adsorption systems for desalination, drying, and cooling applications could be powered by renewable energy sources. Thus, it is a promising technology for solving energy and water problems. Designing an efficient adsorption system and evaluating its performance depend mainly on the adsorption isotherms and kinetics of nanoporous materials. The present work designs and manufactures a precise gravimetric sorption apparatus to measure the adsorption isotherms and kinetics of water vapor onto porous materials. It is equipped with a high-precision mass balance to record the change in mass of the tested sample. The main feature of the present apparatus is using an ultrasonic device to generate water vapor allowing easy control of the water vapor flow rate and operating pressure. This novel approach leads to a significant reduction in the apparatus capital cost. To confirm the accuracy and reliability of the proposed instrument, the adsorption kinetics and isotherms of water vapor onto three different materials are measured using the proposed apparatus and compared to the corresponding data in literature. The maximum deviation is found to be less than 4%, indicating the high accuracy of the proposed instrument. During the repeatability tests, a maximum uncertainty of 1.1% is observed at a relative pressure of 0.8, which is within the accuracy of the electronic mass balance. Accordingly, it is confirmed that the developed apparatus could measure the adsorption isotherm and kinetics of water vapor onto nanoporous materials with high accuracy and reliability.