Cardy Potassium Ion Meter

Calibrating the Cardy isn't complicated. It's basically wash and rinse, wash and rinse.  

To clean the sensor you can use distilled water, which is a lot less expensive than buying refills of the "de-ionized" water that comes with the kit. And don't use their testing tape to clean the sensor. Buy Kleenex brand facial tissues in those little pocket packs. They are potassium-free, and work just fine.

To calibrate the meter first: