What does a sling psychrometer measure?

A sling psychrometer is a device specifically designed to measure relative humidity in the air. It consists of two thermometers: one that measures the ambient air temperature (the dry-bulb thermometer) and another that measures the cooling effect of evaporation from a wetted wick (the wet-bulb thermometer).

The key to understanding how a sling psychrometer works lies in the evaporation process. When the water on the wick evaporates, it cools the wet-bulb thermometer, leading to a lower temperature reading compared to the dry-bulb thermometer. By comparing the two temperatures, you can calculate the relative humidity of the air. Relative humidity is a critical measurement in various applications like HVAC, meteorology, and building performance analysis, as it indicates the amount of moisture present in the air compared to the maximum amount of moisture the air can hold at a given temperature.

In this context, the other options are related to different aspects of atmospheric measurement but do not accurately reflect the primary function of a sling psychrometer. Water vapor pressure is a different measurement related to humidity but not directly measured by this tool, daily temperature changes are monitored by standard thermometers but do not provide information on humidity, and air pressure is measured using a barometer, which