Abstract

This specification discloses a device to determine the partial pressure of oxygen in a gaseous atmosphere. The device, which is immersed in the atmosphere, is constructed to define an enclosed volume in which the atmosphere can be established by means of a small leak. The enclosing structure contains two partitions which can conduct oxygen ions and act as electrochemical cells. One partition is called the pump cell while the other is called the sensor cell. When attached to an external power supply, the current (IP) drawn through the pump cell either adds or removes (from or to the ambient) gaseous oxygen from the volume. As a result of the pumping action, an EMF (VS) develops across the sensor cell which can be used to measure the change in oxygen partial pressure in the volume relative to the ambient. An external circuit causes a pump current to flow which removes oxygen from the volume until VS reaches a reference voltage. Then, pumping is reduced or reversed until VS reaches a second reference voltage. The pumping pattern is caused to repeat indefinitely establishing an oscillatory period that is proportional to oxygen partial pressure.