Which instrument is associated with reading dew point in the air?

• A. Wet bulb thermometer
• B. Barometer
• C. Anemometer
• D. Hygrometer

Answer: (A)

Dew point is about how much moisture the air can hold at a given temperature, so you determine it by measuring humidity through a psychrometric setup. A wet-bulb thermometer is part of that setup: it cools by evaporation, and the amount of cooling depends on how much moisture is already in the air. The difference between the dry-bulb (ambient air temperature) and the wet-bulb temperature tells you the relative humidity, and with that information you can read or calculate the dew point. So the wet-bulb thermometer is the instrument most directly associated with obtaining dew point readings. Barometers measure pressure, anemometers measure wind speed, and hygrometers measure humidity, but they don’t link to dew point readings as directly as the wet-bulb in this context.