Abstract: Apparatus and methods for measuring NOx concentrations are disclosed. One method includes the steps of providing a gas stream having a NO concentration and a NO2 concentration, wherein a sum of the NO concentration and the NO2 concentration is a total NOx concentration; contacting the gas stream with a first zirconium oxide based oxygen sensor at a first temperature to achieve a first NO:NO2 equilibrium at the first temperature; contacting the gas stream with a second zirconium oxide based oxygen sensor at a second temperature to achieve a second NO:NO2 equilibrium at the second temperature; and determining the total NOx concentration by measuring a response of the first zirconium oxide based oxygen sensor to achieve the first NO:NO2 equilibrium and a response of the second zirconium oxide based oxygen sensor to achieve the second NO:NO2 equilibrium. The second temperature is different than the first temperature.

Abstract: Apparatus and methods for measuring gas component concentrations are disclosed. The method includes measuring a total gas concentration, including a first gaseous component and a second gaseous component, in an atmosphere with a gas sensor. The gas sensor includes a first cell and a second cell. The first cell is electrically coupled to a pump controller and the second cell is electrically coupled to a sense controller. The pump controller and sense controller are then switched such that the pump controller is electrically coupled to the second cell and the sense controller is electrically coupled to the first cell. Then a first gaseous component concentration is measured.