The HI98108 pHep+® pH tester provides high accuracy measurements in a rugged pocket-sized design. The simple two-button operation provides one button for ON/OFF, the other for calibration. Being lightweight and only 0.7" thick, the pHep+ is extremely ergonomic and fits comfortably in your hand. The pH electrode uses a unique reference cell design that utilizes an extractable cloth junction. A clogged junction will typically exhibit erratic readings that will not stabilize. Simply extracting a small portion of cloth from the meter will clear any clog by exposing a fresh, clean surface. The ability to clear any clogging will extend the life of the pH electrode.