Today I would like to propose a straightforward and inexpensive scientific experiment. It involves the construction of a psychrometer or psychrometer; for all those who have a little free time, scientific curiosity, and little money.
A psychrometer is a simple device, elementary to build, that allows us to measure different thermodynamic properties of the air, fundamentally humidity.
We will need the following material:
- Two thermometers Preferably of mercury or alcohol.
- A small cloth, cotton or paper
- A small container with water
- A psychrometric graphic. (There are many more on the Internet )
- Support for thermometers
We take one of the thermometers and wrap the bulb with the cloth and hold it so that the bulb is well covered while remaining some fabric hanging. The fabric that remains hanging we put it in contact with the water of the container so that this one ascends by the fabric and moistens the bulb of the thermometer thoroughly. The thermostat must not be submerged in water.
The other thermometer we leave it as it is. We hold both thermostats in the holder. Make sure that the wet thermometer does not dry. Otherwise, the data you read will be incorrect. A small air stream (fan, open windows) may be convenient.
The temperature that marks the dry thermometer is called dry bulb temperature or dry temperature; The one that marks the wet thermometer is called the wet-bulb temperature.
The operation is as simple as reading both temperatures and consult the psychrometric chart to obtain absolute humidity, relative humidity, enthalpy of humid air, the specific volume of breath, and other data.
The physical properties of air vary with its water content. When the humidity is lower, the evaporation of the water from the wet thermometer will cause it to mark a temperature lower than the dry one. When the humidity is 100%, both thermostats will score the same temperature since there is no evaporation because the air does not admit more moisture. The drier the air, the more drying there will be, and the higher the difference in temperature between the two.