What Is a Dew Point Hygrometer?
The dew point is the temperature at which condensation occurs when a gas is cooled. A dew point hygrometer is used to measure the dew point of the gas continuously.
The first application where dew point measurement is needed is in dryers. A low dew point means less moisture in the air, so moisture can be efficiently removed from items that need to be dried.
In the industrial gas industry, a high dew point also means that there is more moisture in the air.
When used outdoors, the low temperatures can lead to condensation and freezing. Therefore, the dew point is always measured with a dew point hygrometer.
Uses of Dew Point Hygrometers
The first use of dew point hygrometers is in dryers. The word “dryer” may bring to mind a machine that dries food at high temperatures, but some foods may deteriorate under high temperatures.
Therefore, it is necessary to dry them at low temperatures, and in doing so, it is essential to expose them to air with a low dew point, so the dew point is constantly measured with a dew point hygrometer.
In other industries, there are also machines that do not like moisture or whose efficiency is reduced by moisture.
When supplying nitrogen or oxygen to such machines, the dew point is always measured with a dew point hygrometer.
Principle of Dew Point Hygrometers
A dew point hygrometer is an instrument that measures the moisture content in the air. The dew point hygrometer can be broadly divided into two types of measurement methods: the capacitance type and the mirror-cooled type.
The capacitance type is easy to measure and is used in portable devices. On the other hand, the mirror-cooled type is highly accurate and can be used for applications requiring high accuracy.
As the name suggests, the capacitance type uses electricity to detect moisture. The capacitance type has a very thin sensor inside, on which a special metal is deposited. When moisture adheres to the sensor, the resistance value changes depending on the amount of moisture. This change in resistance is output from the sensor as the amount of moisture.
As the name implies, the mirror-cooled type uses a mirror. In the mirror-cooled type, the gas whose dew point is to be measured is sprayed onto the mirror surface inside the instrument. Cooling then causes condensation to form on the mirror surface, and heating the mirror surface eliminates the condensation.
The dew point is output by repeating this process to find the best balance. Therefore, highly accurate measurement is possible, but it takes some time.