The HGD21 uses two inlet airs, one for high-purity nitrogen and the other for moisture from a standard humidity generator. With the adjustment handle on the instrument panel, we can freely ｓｅｌｅｃｔ the wet/dry gas switch for each device under test without affecting the measurement of other devices. Precision metering valves ensure stable and adjustable sample flow, swagelok high-polished stainless steel tubing allows humidity to occur faster, and HGD21 can be illuminated with optional LED tubes, making the laboratory brighter and cleaner.