Which tool is used to measure relative humidity (RH)?

Which tool is used to measure relative humidity (RH)?

• A. Analog Hygrometer
• B. Sling Psychrometer
• C. Digital Hygrometer
• D. Thermo-hygrometer

Answer: (B)

Relative humidity depends on how much moisture the air can hold at a given temperature, which you determine by comparing two temperature readings obtained through evaporation. A sling psychrometer has two thermometers—one measuring the dry-bulb air temperature and one with a moistened wick measuring the wet-bulb temperature. When you swing it, water evaporates from the wick, cooling the wet-bulb. The difference between the dry-bulb and wet-bulb readings changes with humidity: the drier the air, the greater the cooling and the larger the difference; the more humid the air, the smaller the difference. Using these two temperatures, you can read relative humidity from a psychrometric chart or calculate it with a formula. This method is specifically designed to derive RH from the wet- and dry-bulb readings, making the sling psychrometer the best tool for measuring relative humidity. Hygrometers and thermo-hygrometers measure humidity directly from sensors, but the sling psychrometer uniquely provides RH through the wet-bulb/dry-bulb method.

Relative humidity depends on how much moisture the air can hold at a given temperature, which you determine by comparing two temperature readings obtained through evaporation. A sling psychrometer has two thermometers—one measuring the dry-bulb air temperature and one with a moistened wick measuring the wet-bulb temperature. When you swing it, water evaporates from the wick, cooling the wet-bulb. The difference between the dry-bulb and wet-bulb readings changes with humidity: the drier the air, the greater the cooling and the larger the difference; the more humid the air, the smaller the difference. Using these two temperatures, you can read relative humidity from a psychrometric chart or calculate it with a formula. This method is specifically designed to derive RH from the wet- and dry-bulb readings, making the sling psychrometer the best tool for measuring relative humidity. Hygrometers and thermo-hygrometers measure humidity directly from sensors, but the sling psychrometer uniquely provides RH through the wet-bulb/dry-bulb method.