Rosemount 6888Xi - Section 4: Troubleshooting; Overview of Operating Principles

Troubleshooting 71
Reference Manual Section 4: Troubleshooting
00809-0100-4892 January 2019
Section 4: Troubleshooting
4.1 Overview
When the Zirconium Oxide sensing cell is heated to its setpoint [736 °C (1357 °F)], the cell will
generate a voltage that represents the difference between the process O2% and the reference
O2% inside the probe (20.95% O2 instrument or ambient air).
When flowing calibration gases, the raw cell millivolt value should represent the levels on the
chart in Figure 4 -1. Note that the raw cell millivolt value increases logrithmically as the O2 con-
centration decreases.
FIGURE 4-1. O
2
Sensor mV Reading vs O
2
at 736°C (1357°F) (Reference Air, 20.95 O
2
)
120
100
80
60
40
20
0
EMF (mV)
0 5 10 15 20
c(O
2
)(%)