Fluidic partial pressure sensor

Claim 1

A fluidic partial pressure sensor for obtaining direct indication of the partial pressure of gas constituent in a mixture which comprises: a first input channel for receiving a reference gas; a second input channel for receiving a sample mixture gas; a fluidic bridge which comprises a pair of linear resistors connected respectively to each of the input channels, a pair of non-linear resistors connected at a first junction in series to each of the linear resistors and at a second junction to a reference output channel, and means for sensing pressure across the bridge; and a means for creating a constant pressure drop across the fluidic bridge, wherein the characteristics of the linear and non-linear resistors' geometry is determined by the equation ##EQU8## where P b = the pressure drop across the bridge a and b = geometric constants for the linear and non-linear resistors in the bridge circuit ρ = the density of the reference gas μ = the viscosity of the reference gas and θ has a value of approximately 0.05 or less at the anticipated ambient pressures at which the sensor will operate.

Claim 6

A method for obtaining a direct indication of the partial pressure of a first gas in a reference gas by means of a fluidic bridge sensor containing a first and second channel, each having a linear and nonlinear resistor, and an outlet common to each of the channels, comprising the steps of: selecting the bridge pressure drop compatible with system criteria; selecting the geometries of the bridge resistors according to the equation ##EQU9## where P b = the pressure drop across the bridge a and b = geometric constants for the linear and non-linear resistors in the bridge circuit ρ = the density of the reference gas μ = the viscosity of the reference gas and θ has a value of approximately 0.05 or less at the anticipated ambient pressures at which the sensor will operate; supplying the fluidic bridge concentration sensor with the reference gas in the first channel and with a sample mixture gas comprising the first gas whose partial pressure is desired to be measured in the reference gas in the second channel of the sensor; exhausting the sample mixture gas and the reference gas through the common outlet which is maintained at a constant pressure; and measuring the pressure difference across the bridge channels, thereby obtaining a signal output which provides a pressure directly proportional to the partial pressure of the first gas in the reference gas.

Claim 7

A method for obtaining a direct indication of the partial pressure of a first gas in a reference gas by means of a fluidic bridge sensor containing a first and second channel, each having a linear and nonlinear resistor, and an outlet common to each of the channels, comprising the steps of: selecting the bridge pressure drop compatible with system criteria; selecting the geometries of the bridge resistors according to the equation ##EQU9## where P b = the pressure drop across the bridge a and b = geometric constants for the linear and non-linear resistors in the bridge circuit ρ = the density of the reference gas μ = the viscosity of the reference gas and θ has a value of approximately 0.05 or less at the anticipated ambient pressures at which the sensor will operate; supplying the fluidic bridge concentration sensor with the reference gas in the first channel and with a sample mixture gas comprising the first gas whose partial pressure is desired to be measured in the reference gas in the second channel of the sensor; exhausting the sample mixture gas and the reference gas through the common outlet which is maintained at a constant pressure; and measuring the pressure difference across the bridge channels, thereby obtaining a signal output which provides a pressure directly proportional to the partial pressure of the first gas in the reference gas.