An Evaluation of the Fluidic Oxygen Partial Pressure Sensor.

A theoretical concept for a fluidic gas partial pressure sensor is evaluated. In the sensor concept, a fluidic resistive bridge gas concentration sensor is powered by the vacuum produced with a compressible flow ejector. Because of the ejector characteristics, the pressure drop across the bridge is proportional to the ambient pressure hence, the sensor output is proportional to the gas concentration and the ambient pressure, the product of which is partial pressure. A complete mathematical model is derived that is in close agreement with the experiment. A prototype sensor is discussed and tested over a range of 0.3 to 1.0 atmospheres pressure and 0 to 100 concentrations of CO2 in air and O2 in air. The test results show that the sensor responds to both variables. Environmental sensitivities and signal amplification are discussed. Author