Скачать или смотреть Let's Learn about the " Wet and Dry Bulb" Thermometers

The Hygrometer aka the Wet and Dry Bulb Thermometers.
The Wet and Dry Bulb Thermometer is also a hygrometer, which is simply an instrument used to measure the relative humidity of the atmosphere. It consists of two thermometers, one with a bulb that is kept dry and one that is kept moist

What the HYGROMETER readings mean:
1. If there is a LARGE DIFFERENCE between the temperature readings then the Air is DRY.

2. If there is a SMALL DIFFERENCE between the temperature readings then the AIR is very CLOSE TO SATURATION.

3. If there is NO DIFFERENCE between the Thermometers then the AIR is SATURATED.


WHY
If a thermometer is wrapped in a water-moistened cloth, it will behave differently. The drier and less humid the air is, the faster the water will evaporate. The faster water evaporates, the lower the thermometer's temperature will be relative to air temperature.


Water can only evaporate if the air around it can absorb more water. This is measured by comparing how much water is in the air, compared to the maximum which could be in the air—the relative humidity. 0% means the air is completely dry, and 100% means the air contains all the water it can hold in the present circumstances and it cannot absorb any more water (from any source).

This is part of the cause of apparent temperature in humans. The drier the air, the more moisture it can hold beyond what is already in it, and the easier it is for extra water to evaporate. The result is that sweat evaporates more quickly in drier air, cooling down the skin faster. But if the relative humidity is 100%, no water can evaporate, and cooling by sweating or evaporation is not possible.

When relative humidity is 100%, a wet-bulb thermometer can also no longer be cooled by evaporation, so it will read the same as an unwrapped thermometer.