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.