The Oakton phtestr 50 has a replaceable double junction sensor for longer life, an expanded number of applications, and easy maintenance. Double-junction electrode sensor handles wastewater and solutions containing sulfides, heavy metals, and TRIS. Electrode sensor offers a clog-resistant Kynar junction and a recessed, glass pH bulb to protect against breakage. Valox sensor housing resists most chemicals. The keypad clicks to confirm operation, and allows access to a variety of functions. Calibrate up to three pH points with the auto-buffer recognition at both USA and NIST standard buffers. Additional features include an automatic temperature compensation (ATC), hold function, Auto-off function, self-diagnostic error messages, and a three-segment battery-life indicator. Versatile, compact design works in the field or laboratory redesigned leak-proof cap functions as a sample cup, hydrating cup and stabilizing base to stand the meter upright easy-to-navigate interface for quick setup and calibration replaceable, double-junction electrode sensors save time and money automatic temperature compensation ensures accurate reading in varying environments.