HOBO Dissolved Oxygen Data Logger

HOBO Dissolved Oxygen Data Logger

Manufacturer: onset
Part Number: U26-001
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Measure oxygen concentrations in lakes, streams, rivers, estuaries, and coastal waters with the HOBO U26 Dissolved Oxygen Data Logger. This affordable and precise data logger is recommended for aquatic biology and hydrology research projects. The HOBO U26 uses RDO® Basic (Rugged Dissolved Oxygen) optical DO sensor technology and is easy to maintain.


    Temperature, Dissolved Oxygen


  • Affordable, high performance dissolved oxygen (DO) monitoring with 0.2 mg/L accuracy
  • Optical DO sensor technology for long-lasting calibration with less maintenance
  • HOBOware Pro's Dissolved Oxygen Assistant software corrects for measurement drift from fouling; provides salinity-adjusted DO concentrations and percent saturation
  • Optical USB interface for high-speed, reliable data offload
  • Easy-to-replace DO sensor cap lasts six months
NOTE: For DO measurements in saltwater, an adjustment for salinity is required. For waters with small changes in salinity (<2 ppt), a salinity meter reading typically provides enough accuracy. For environments with greater salinity changes, we generally recommend the HOBO U24-002-C conductivity logger.

NOTE: If you need DO in Percent Saturation, barometric pressure data is required, which can be logged with a HOBO Water Level Data Logger (U20-001-04).


Detailed Specifications:

Dissolved Oxygen
Sensor Type Optical
Measurement Range 0 to 30 mg/L
Calibrated Range 0 to 20 mg/L; 0 to 35°C (32 to 95°F)
Accuracy 0.2 mg/L up to 8 mg/L; 0.5 mg/L from 8 to 20 mg/L
Resolution 0.02 mg/L
Response Time To 90% in less than 2 minutes
DO Sensor Cap Life 6 months, cap expires 7 months after initialization
Temperature Measurement/Operating Range -5 to 40°C (23 to 104°F); non-Freezing
Temperature Accuracy 0.2°C (0.36°F)
Temperature Resolution 0.02°C (0.04°F)
Response Time To 90% in less than 30 minutes
Memory 21,700 sets of DO and temperature measurements (64 KB total memory)
Logging Rate 1 minute to 18 hours
Time Accuracy ±1 minute per month at 0 to 50°C (32 to 122°F)
Battery 3.6 V lithium battery; factory replaceable
Battery Life 3 years (at 5 minute logging)
Download Type Optical
Depth Rating 100 m (328 ft)
Wetted Materials Black Delrin®, PVC, EPDM o-rings, silicone bronze screws; rated for saltwater use
Size 39.6 mm diameter x 266.7 mm length (1.56 x 10.5 inches)
Weight 464 g (16.37 oz)
Description: ce The CE Marking identifies this product as complying with all relevant directives in the European Union (EU).


  • U26-001 data logger
  • DO sensor cap
  • Protective Guard
  • Calibration Boot with sponge

Environment: The U26-001 Data Logger is for use in Underwater environments

Measurements: The U26-001 Data Logger supports the following measurements:

Temperature, Dissolved Oxygen