Field-proven, the YSI 55 meter measures dissolved oxygen in mg/L or percent. Offering pushbutton calibration with a built-in calibration chamber and direct salinity compensation, the YSI 55 provides simultaneous readings of oxygen and temperature. Temperature compensation is automatic. The stainless steel YSI probe sinks easily and the backlit display features a low battery indicator. A strain relief protects cable options of 12, 25, or 50 feet. Battery powered.