Introducing Apera's all-new Optical Dissolved Oxygen Meter. Equipped with state-of-the-art optical DO probe, the DO850 meter generates quick and accurate dissolved oxygen readings in a hassle-free manner. No membrane or solution needed for the optical probe. Unlike the traditional polarographic or galvanic probes, the optical probe does not consume oxygen at all, hence has no requirement on the water flowing speed. Quick response time: only takes 1 to 3 minutes to get stable readings. Durable luminescent cap: over 8000 hours’ service life. The special coating on the luminescent cap makes it anti-interference and unaffected by light and chemicals. A calibration cap comes with the probe, which allows it to be easily calibrated and stored in saturated air. Rugged Structure: The IP67 waterproof and Dustproof structure allows the meter to be used in harsh environments. The silicon protective cover gives you a nice and firm grip. The foldable stand also allows use as a benchtop meter. Intelligent Functions: Auto. Temperature Compensation; Auto. Air Pressure Compensation; Manual salinity compensation; large backlit LCD simultaneously displays DO and temperature readings. Users can switch from mg/L to ppm or percentage with a single tap. The advance digital processing technology supports stable reading and auto-lock display modes. The meter is RoHs& CE certified and comes with a 3-YEAR Warranty (1-Year for the Optical Probe).