A hand-held, battery-powered instrument designed to measure the concentration of dissolved oxygen (DO) in solutions, typically in the field. It typically consists of an electronic unit that processes an electric signal from a sensor and displays oxygen concentration, and probes including a sensor that detects dissolved oxygen level and a transducer that converts oxygen values into electrical signals. It may include probes that measure oxygen concentration in the atmosphere. The meter may have computerized capabilities and dedicated software to process information [may include biological oxygen demand (BOD) determination].