Abstract

This specification discloses a device to determine the percentage of oxygen in an ambient 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. If an external circuit causes adequate current to flow in the pump cell to keep the sensor EMF at a constant value, then the magnitude of the current is linearly proportional to the percentage of oxygen in the atmosphere.