HOBO Dissolved Oxygen Logger - U26-001

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IMPORTANT: This HOBO data logger requires HOBOware Pro software and a communications device. See compatible items below.

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.

  • 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).


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

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

The U26-001 Data Logger supports the following measurements:

Temperature, Dissolved Oxygen

Onset # U26-001
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U26-001 Data Logger Product Video

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).


Part Number
Graphing and Analysis
HOBOware Pro Mac/Win (USB cable included)
HOBOware Pro - Mac/Win Data Logger Software - Download Only
Part Number
Data Offload - Base Stations - Shuttles
Optic USB Base Station
HOBO® Waterproof Shuttle
Part Number
Calibration Solution
Sodium Sulfite Solution - U26-CAL-SOL
Coupler Replacement
Replacement Coupler for U20L, U22, U24, and U26 Data Loggers
Replacement Sensor Cap
Replacement DO Sensor Cap - U26-RDOB-1
Part Number
Antifouling Protective Guard
Antifouling Protective Guard - U26-GUARD-2
Carrying Case
Pelican Case
Data Offload - Base Stations - Shuttles
HOBO U-Shuttle
HOBO® Waterproof Shuttle
Stainless Steel Cable/Crimps
1/16" Stainless Steel Cable 300ft
1/16" Stainless Steel Cable 50ft
Crimp Sleeve 12 Pack
Documentation for the U26-001

DO-technology-backgrounder logo
Dissolved Oxygen sensor technology backgrounder

Dissolved-Oxygen-Assistant-Users-Guide-15604 logo
Dissolved Oxygen Data Assistant for HOBOware Pro User's Guide

U26-RDOB-1 RDO® Basic Sensor Replacement Kit - Manual

HOBO® U26 Dissolved Oxygen Logger Manual