Application 
To test the water vapor transmission rate (WVTR) of packaging materials, such as plastic film, composite film, coextrusion film, aluminum-plated film, aluminum foil, infusion bag, sheets, paper, paper board, solar battery panel, cellophane, ceramics and porcelain, and various containers such as bag, pouch, bottle, can, bowl, and box. It is widely used in the industries of food, pharmaceuticals, personal care, household, electronics and so on and institutions of quality control, drug inspection and science research. 

Working principle 
Weight reduction method (wet cup method).
Fill the test dish with distilled water (according to stipulation of ASTM E 96), seal the cup with test sample,
keep humidity difference between inside and outside of the cup, and water vapor will penetrate the test sample;
monitor the change of cup weight to calculate transmission rate.