Take a straw used for drinking cold drinks and make its one end pointed with a sharp blade. As displayed in the diagram, stick it in the middle of the cardboard just below the reel with the help of a drawing pin but take care that the portion between the drawing pin and the pointed straw remains larger than the remaning portions of the straw to ensure the weight of the straw remains more toward the pointed end. Also, take precaution that the straw does not get fixed up with the cardboard. Rather, it should be in a position to move up and down freely with just a suggestion.

Now take a long human hair and fix one end of it on the upper portion of the reel with the help of a pin or sellotape, and then taking the hair above the reel tie its second end with the pointed end of the straw and keeping the straw horizontal.

To perform this experiment, cover your Hygrometer with a towel, soaked in hot water. Remove the towel after some time and note the position of the pointed end of the straw. Due to the humidty the hair would expand and grow larger, causing the straw to come down. Now remove the mositure on the hair by keeping it in some warm and dry place.When the pointed end of the straw remains steady at certain point for sufficiently long period of time, mark this point alos. This would be above the previous point. Divide these two points into small portions and graduate them. With the help of the above experiment you can find out the Humidity of the atmosphere on different days.