Technical Notes: Dew Point Temperature Error from Measuring Dry Bulb Temperature and Relative Humidity

A component error analysis was performed to relate the accuracy of measured values of dry bulb temperature and relative humidity to errors in calculated dew point temperature. Dew point temperature errors were found to be greatest for dryer air (less than about 50% relative humidity) and to increase proportionately with dry bulb temperature. Error calculations for various combinations of dry bulb temperature, relative humidity, and measurement errors in each variable which are representative of current commercial sensors, are provided in tabular format. The magnitude of dew point errors from these calculations suggests that modern applications such as automated weather stations can have significant errors in computed dew point temperature, and even for very accurate sensors the dew point error can exceed twice the magnitude of the dry bulb sensor error for dryer conditions.