Abstract
An injecting water dew point hygrometer using atmospheric pressure as the standard of the pressure difference measurement is described.
A sample gas is introduced into a metal vessel which is connected to two U-tube mano-meters, one of which has one end open to the atmosphere and the other attached to a pump for changing the volume of the sample gas.
As water of constant volume is injected into the vessel, the pressure of the sample gas increases, and when the pressure is reduced to the initial pressure, the volume of the sample gas will be increased.
The dew point of the sample gas is determined theoretically either from the increased pressure before and after the injection of water or from the increased volume after the reduc-tion of pressure; in both cases the temperature of the sample gas is made the same before and after the injection.
It is shown experimentally that both the constant volume and the constant pressure methods are applicable for measuring the dew point with a high accuracy.
