A water injection dew point hygrometer of atmospheric pressure type with a U-tube water manometer is described.
The dew point hygrometer is composed of a sample vessel, a water injector and a Utube open water manometer. The U-tube manometer is connected to the vessel by a glass tube with a three-way cock. One end of the three-way cock is open to the atmosphere. The space between the U-tube manometer and the three-way cock is saturated with water vapor.
A sample gas is introduced into the vessel and a definite amount of water is injected into the vessel. The dew point of the sample gas is obtained theoretically from the increase of pressure by the water injection.
Results of experiments show that the pressure of the sample gas becomes almost in equilibrium within 1 min after the water injection, and that the dew point is measurable with an accuracy of ±0.1°C.