ELI5: Explain Like I'm 5

Fluoride selective electrode

A fluoride selective electrode is a device used to measure how much fluoride is in a liquid or gas. It works by sending an electric current through the liquid or gas, and then measuring how much fluoride is in the sample. The device then tells you the amount of fluoride present. This information can be used to help people test the safety of drinking water or make sure that medications are at the right strength.