Abstract: The respirometer module consists of an airtight chamber which includes an air pump, a carbon dioxide scrubber, an electronic gas volume transducer, an air vent, and a fill tube. This single module is combined with separate sample chambers of various sizes and applications. The sample chambers are designed for laboratory, on-line, or submersible application to measure respiration of microorganisms, animals, fish, and plants. The respirometer module which provides air circulation, CO.sub.2 absorption, and electronic gas volume sensing can be used interchangeably with any one of these specialized chambers.

Abstract: An instrument for measuring the amount of dissolved oxygen in liquids such as waste water includes an enclosure which is partially submerged. Liquid from the main body is continuously circulated through the enclosure and an entrapped volume of air is continuously circulated through the enclosure. The amount of oxygen in this entrapped air is continuously measured by an oxygen concentration sensor which is disposed in the path of the circulating air. This provides an indirect measurement of the amount of dissolved oxygen in the liquid without actually bringing the sensor into contact with the liquid.

Abstract: A submersible recording respirometer includes an oxygen analyzer which measures the concentration of oxygen absorbed by a wastewater sample contained in an aeration chamber. The aeration chamber forms part of a housing which is submerged in the main body of wastewater and the aeration chamber is periodically drained, washed with fresh water and refilled with another wastewater sample. This cycle is accomplished automatically under the direction of a microprocessor-based control circuit which generates signals to a chart recorder that provides a hard copy of the measurement results.