Which instrument is specifically used to measure humidity by swinging a wet and dry bulb in air?

Which instrument is specifically used to measure humidity by swinging a wet and dry bulb in air?

• A. Hygrometer
• B. Sling Psychrometric
• C. Barometer
• D. Thermometer

Answer: (B)

Humidity is determined by how quickly water can evaporate from a surface in the moving air. A sling psychrometer uses two thermometers mounted together: one reads the air’s temperature directly (dry-bulb), and the other has its bulb coated with a wick of water (wet-bulb). When you swing the device, air constantly passes over both bulbs. Water on the wet bulb evaporates, which cools that bulb. How much cooling occurs depends on the air’s moisture: in dry air, evaporation is rapid and the wet-bulb temperature drops a lot; in humid air, evaporation slows and the wet-bulb temperature stays closer to the dry-bulb temperature. By comparing the two readings, you can determine the relative humidity (often with a chart or calculator). This swinging, wet-and-dry-bulb setup is what defines a sling psychrometer. The other instruments measure different things or don’t use the wet-dry bulb method.

Humidity is determined by how quickly water can evaporate from a surface in the moving air. A sling psychrometer uses two thermometers mounted together: one reads the air’s temperature directly (dry-bulb), and the other has its bulb coated with a wick of water (wet-bulb). When you swing the device, air constantly passes over both bulbs. Water on the wet bulb evaporates, which cools that bulb. How much cooling occurs depends on the air’s moisture: in dry air, evaporation is rapid and the wet-bulb temperature drops a lot; in humid air, evaporation slows and the wet-bulb temperature stays closer to the dry-bulb temperature. By comparing the two readings, you can determine the relative humidity (often with a chart or calculator). This swinging, wet-and-dry-bulb setup is what defines a sling psychrometer. The other instruments measure different things or don’t use the wet-dry bulb method.