The YSI 550A adopts a fully waterproof (IP67 waterproof rating) and impact resistant instrument housing, and features an innovative field replaceable dissolved oxygen electrode module. Using YSI's proven polarographic technique and YSI's globally renowned thermistor technique, dissolved oxygen and temperature can be measured simultaneously. The new generation of PE cover film provides faster reaction time and lower stirring dependence.

1. Fully waterproof, meeting IP67 waterproof rating

2. The dissolved oxygen electrode module can be replaced in the field

3. Faster reaction time and lower stirring dependence

4. Stainless steel probe, sturdy and durable, easier to sink into water

5. Install stress relievers at both ends of the cable interface to reduce material fatigue at the connection and effectively extend the cable's lifespan

6. Built in dissolved oxygen calibration room/probe storage room, convenient to carry and maintain the normal working state of the probe

7. Available with 3.7, 7.5, 15, and 30 meter cables for selection

8. The measurement range of dissolved oxygen has been expanded to 50 milligrams per liter

9. Air saturation or milligram/liter calibration mode

10. 2000 hours of ultra long battery life