The HOBO U26 Dissolved Oxygen Logger is a highly precise, low-cost data logger for measuring concentrations of oxygen in lakes, streams, rivers, estuaries, and coastal waters. Used by aquatic biologists, hydrologists, and other research professionals, the HOBO U26 combines the high accuracy, robust performance of industry-leading RDO® Basic (Rugged Dissolved Oxygen) sensor technology with an easy-to-maintain design.