What is Dew point meter? Operation

What is a Dew point meter?

Dew point is, When cooled at constant pressure, if the air temperature is reduced, the water vapor in the air will begin to condense at a particular temperature. This temperature is called the dew point temperature

A dew point meter measures and records all pressure dew points, other dew points and moisture related measurements etc.

Components of Dew point meter

  • A shiny surface (mirror) is fixed with a thermocouple.
  • A nozzle provides a jet of air in the mirror.
  • A source of light constantly focused on the mirror.
  • A photo cell to detect the amount of light reflected in the mirror

The mirror is constantly cooled by a cooling medium. The cooling medium is maintained at a constant temperature

To this mirror is attached a thermocouple whose cables are connected to a millivoltimeter

Operation of the dew point meter:

A light is constantly made to fall at an angle on the mirror and the amount of reflected light is detected by a photoelectric cell.

Now a jet of air is made to fall at an angle on the mirror and the water vapor (moisture) contained in the air begins to condense on the mirror and appear as small drops (dew) on the mirror.

This moisture (dew) formed in the mirror reduces the amount of light reflected in the mirror and is detected by a photocell. When for the first time, there is a change in the amount of light transmitted; it becomes a sign of dew formation.

In this case (ie, when the proper formation is first detected), the temperature indicated by the thermocouple attached to the mirror becomes the temperature of the dew point.

Therefore, this arrangement is used to determine the time the dew appears for the first time and the temperature of the dew point.

Application of the dew point meter.

  • This instrument is used on ships to protect cargoes from condensation damage by keeping the dew point of the air in the holds below the temperature of the cargo.
  • Used in industries to determine the dew point.
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