The Nova Model 325 portable trace oxygen analyzer is designed to measure the oxygen concentration of a clean, dry and non-corrosive sample gas. It uses a customer replaceable electrochemical oxygen sensor, which responds quickly and accurately to the oxygen present in the sample gas. Output from the sensor is directed to a digital readout meter and recorder output terminals. Several models are available. All models can measure ppm levels of oxygen in any range from 0-10 to 0-19,990 ppm. The lowest readable level is 1 ppm. Model 325 comes with a flow control valve and flowmeter for regulating the flow of sample under positive pressure, as well as a built-in sample pump or flowmeter for use on samples under atmospheric or slight negative pressure.