YSI® 550a Dissolved Oxygen Meter


Measure temperature and dissolved oxygen simultaneously using highly accurate thermistors and YSI's proven polarographic technology for dissolved oxygen. The fastest DO response times on the market.

Measurements are fast and easy with one-hand operation, an easy-to-use backlit display, automatic push-button calibration, and a weighted, quick-sinking probe. The YSI550A DO has a built-in calibration chamber, low-battery indicator, direct salinity, and altitude compensation. The instrument provides simultaneous readings of oxygen and temperature. Dissolved oxygen readings are automatically compensated for temperature.

Screw-on cap membranes make membrane changes easier than ever. The PE membranes are also faster responding and require far less flow dependence.

The replaceable electrode decreases any down time due to old or damaged electrodes. Simply unscrew the old electrode, replace it with a new one, and calibrate! No need to send it in or to replace the whole cable assembly. The cables are now even stronger!



Medium: Fresh, sea or polluted water

Dissolved Oxygen Sensor: Steady-state polarographic

Dissolved Oxygen Probe: Field-replaceable module

Dissolved Oxygen Response Time: 95% of end value in 9 seconds

Temperature Units: Celsius or Fahrenheit, user selectable

Parameter Compensation: Automatic temperature compensation for dissolved oxygen

Automatic salinity compensation (0-70 ppt) for dissolved oxygen

Altitude compensation for dissolved oxygen percent calibration

Size: 4.7 in. width; 9 in. length (11.9 cm x 22.9 cm)

Weight with Batteries: 2 lb. (0.91 kg)

Power: 4 alkaline C-cells

Battery life: Over 2000 hours at 25°C (77ºF)

Cables: 12, 25, 50, and 100-foot lengths

(3.5, 7.5, 15, 30.5 meter lengths)

Other Features: Waterproof to IP-67

High-impact resistance

Push-button calibration

Built-in calibration chamber

Large back-lit display

Low battery indicator on display

Manual salinity input


Toll Free: 1-888-233-3535

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