What instrument is used to measure dry bulb temperature?

• A. Digital thermometer
• B. Standard mercury thermometer
• C. Wet bulb thermometer
• D. Psychrometer

Answer: (B)

The standard mercury thermometer is the correct instrument to measure dry bulb temperature because it accurately indicates the air temperature by measuring the thermal expansion of mercury in a calibrated glass tube. This type of thermometer does not take into account humidity or other factors that would affect temperature readings in specific environments; it simply provides a straightforward measurement of the ambient air temperature.

In contrast, a digital thermometer also measures temperature effectively but is not typically classified as specifically measuring dry bulb temperature in traditional contexts where a mercury thermometer is standard. A wet bulb thermometer is designed to measure the temperature of evaporative cooling and reflects humidity levels, while a psychrometer uses both a dry and wet bulb thermometer to calculate relative humidity, thus not focusing directly on the dry bulb measurement alone.