Transient mode oxygen sensor and method

Claim 1

An electrochemical apparatus for making a measurement of oxygen partial pressure in an ambient environment including other gaseous materials, said electrochemical apparatus including: a solid electrochemical pump cell; a solid electrochemical sensor cell; an associated supporting structure which in combination with said pump and sensor cells defines an enclosed volume; a leak orifice for providing communication between said enclosed volume and the ambient environment so that when said enclosed volume is immersed in an ambient environment containing a partial pressure of oxygen there is a tendency for the partial pressure of oxygen inside said enclosed volume to equalize with the partial pressure of oxygen of the ambient environment; a first circuit means coupled to said pump cell to apply an electrical input to said pump cell, said electrical input being a voltage step function with an abruptly rising leading edge with respect to time having a polarity suitable for withdrawing oxygen from said enclosed volume, and said first circuit means including measuring means for measuring the magnitude of the current drawn through said pump cell as a result of the voltage step function; a second circuit means coupled to said sensor cell for measuring an electrical output generated by said sensor cell in response to said electrical input at said pump cell, said electrical output having a relatively simple relationship to the ambient oxygen partial pressure so that said electrochemical apparatus can be used as a sensor of the oxygen partial pressure, said second circuit means being adapted to measure the first derivative with respect to time of the sensor voltage, as induced by the pumping action of said pump cell when the voltage step is applied to said pump cell, said voltage step rising in magnitude with respect to time faster than the sensor voltage; and said pump and sensor cells being formed of platelets of solid ionic conductors capable of conducting oxygen ions and including two electrode layers attached to opposing faces of each of said platelets, and lead wire attached to each of said electrodes for coupling said external circuit means to said pump and sensor cells.

Claim 9

A method for making a measurement of oxygen partial pressure in an ambient environment having other gaseous material including the steps of: establishing an enclosed volume with restricted access to the ambient environment, the enclosed volume being bounded by a solid electrolyte electrochemical pump cell and a solid electrolyte electrochemical sensor cell, and the restricted access being sufficient so that when the enclosed volume is immersed in an ambient environment containing a partial pressure of oxygen there is a tendency for the partial pressure of oxygen inside the enclosed volume to equalize with the partial pressure of oxygen of the ambient environment; applying to the pump cell an electrical voltage step function with an abruptly rising leading edge having a polarity suitable for withdrawing oxygen from the enclosed volume; measuring the magnitude of the current drawn through the pump cell as a result of applying the voltage step function; measuring an electrical output generated by the sensor cell in response to the electrical input at the pump cell, the electrical voltage step function being chosen to rise in magnitude with respect to time faster than the electrical output; and calculating the oxygen partial pressure using an inverse relationship with the first derivative of the voltage measured at the sensor cell.

Claim 10

A method for making a measurement of oxygen partial pressure in an ambient environment having other gaseous material including the steps of: establishing an enclosed volume with restricted access to the ambient environment, the enclosed volume being bounded by a solid electrolyte electrochemical pump cell and a solid electrolyte electrochemical sensor cell, and the restricted access being sufficient so that when the enclosed volume is immersed in an ambient environment containing a partial pressure of oxygen there is a tendency for the partial pressure of oxygen inside the enclosed volume to equalize with the partial pressure of oxygen of the ambient environment; applying to the pump cell an electrical voltage step function with an abruptly rising leading edge having a polarity suitable for withdrawing oxygen from the enclosed volume; measuring the magnitude of the current drawn through the pump cell as a result of applying the voltage step function; measuring an electrical output generated by the sensor cell in response to the electrical input at the pump cell, the electrical voltage step function being chosen to rise in magnitude with respect to time faster than the electrical output; and calculating the oxygen partial pressure using an inverse relationship with the first derivative of the voltage measured at the sensor cell.