This document provides instructions for using a sling psychrometer to measure wet-bulb and dry-bulb temperatures and determine relative humidity. Students will construct a sling psychrometer using two thermometers, dowel, screw, washers and a wet cotton sleeve. They will take readings after swinging it, then use a chart to find relative humidity based on the temperature difference. The main conclusion is that tables and charts are needed to convert data into the final result. Repeating the process over time or in different conditions can show relationships between humidity and temperature.