How does a Hanna EC/TDS tester work?

To get an EC reading when using a tester, you need two electrodes, a meter, and an applied voltage.

Two electrodes with an applied AC voltage are placed in the solution. This creates a current dependent upon the conductive nature of the solution. The meter reads this current and displays either conductivity (EC) or ppm (TDS). Each type of conductivity probe works a bit differently, but the basics are the same.