Extech PH100 ExStik Handheld pH Tester is designed as a unique stick-style pH meter. The Extech PH100 features the "RENEW" function to indicate when the pH electrode should be replaced, a "CAL" function to indicate when the unit requires recalibration, automatic temperature compensation, and an analog bargraph to help reveal trends in acidity or alkalinity. (Requires Extech PH103 buffer solution)