Characteristics

The typical zirconia oxygen sensor consists of a closed end tube with the sensing portion at the tip. The tube operates on the principle of yttria-stabilized zirconia.  Figure 1 illustrates the SuperOX^TM Sensor design with details omitted for clarity. The tip of the tube is spring loaded into contact with the outer, negative platinum electrode, which is in contact with the ceramic sheath. The inner, positive electrode is spring loaded into contact with the inner zirconia surface. A thermocouple is positioned close to the inner electrode surface and reference air bathes the sensing surface.

 

Figure 1

                                           

To the instrument technician, the sensor looks like a battery (see Figure 2). It displays a voltage, EC, from which the carbon potential can be calculated. The probe thermocouple is shown next to the sensing electrode.

                                      

Figure 2

The value of the internal resistance can be measured, as shown in Figure 3, by connecting a shunt resistor across the sensor terminals, measuring the resultant voltage, Em, and carrying out the simple calculation shown.

Figure 3