Science Buddies: "Ask an Expert"

I made a sling psychrometer for my science fair but it doesn't seem to be working right. My teacher wants me to take readings before add steam, and then 2 minutes after I introduce steam and then again at 5 minutes and 10 minutes after the steam is introduced.

As soon as I add water to the gauze on the wet bulb and spin it in the air for two minutes, the wet bulb drops in temperature. When I introduce steam, the wet bulb decreases in temperature and the dry bulb stays consistent. As we head toward the 5 minute mark both the dry bulb and the wet bulb increase in temperature and then by the 10 minute reading both increase even more.

Are we doing something wrong? My understanding was that the dry bulb would remain the same temperature throughout the experiment and the wet bulb would decrease in temperature. Are we supposed to add more water to the gauze after every reading?

Thank you so much for your help!

Dear SkippyProductions,

Are you doing the experiment from Science Buddies called "Make Your Own Psychrometer" (https://www.sciencebuddies.org/science- ... eityourown)? According to the procedure in that article, the temperature of the dry bulb thermometer should be the same throughout and the temperature of the wet bulb thermometer should stop changing within two or three minutes. I do not think that more water should be added to the gauze after every reading because I believe that your independent variable is the change in the dry bulb temperature. There should not be two independent variables in a experiment, therefore the amount of water on the gauze should not be changed.

I hope this helps you. If you have any questions, please let me know.

RicaC