Ammonium (NH4+) ISE electrode; 0 to 200 mg/L-N; 1, 2, or 3 point user selectable calibration; for use in freshwater only; 17m depth maximum.

YSI 2003 Polarographic Dissolved Oxygen Sensor for any cable for the Professional Plus and Pro20 DO instruments; Comes with 6 membrane caps and bottle of solutions; Cables must be ordered separately; 1-year sensor warranty.