Emerson Process Management IM-106-340 instruction manual Troubleshooting, Overview

Instruction Manual

IM-106-340, Rev. 4.0 May 2006

Oxymitter 4000

Section 8 Troubleshooting

OVERVIEW

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 8-1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 8-3 Alarm Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 8-3 Alarm Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 8-4 Identifying and Correcting Alarm Indications . . . . . . . . . page 8-5 Calibration Passes, but Still Reads Incorrectly . . . . . . . . page 8-22

While the Oxymitter 4000 electronics provides a significant number of diagnostic alarms to assist in troubleshooting potential problems, it is good to place these alarms in perspective with respect to the instrument's operating principles:

When the Zirconium Oxide sensing cell is heated to its setpoint [1357°F (736°C)], the cell will generate a voltage that represents the difference between the process O2% and the reference O2% inside the probe (20.95% O2 ambient air).

Test points, Figure 8-1,are provided to read the raw millivolt value generated by the thermocouple that controls the cell temperature and also the raw cell signal.

The cell temperature at test points 3 and 4 should always be stable at approximately 29 to 30 millivolts, which represents the [1357°F (736°C)] setpoint temperature.

When flowing calibration gasses, the raw cell millivolt value at test points 1 and 2 should represent the levels on the chart in Figure 8-1.Note that the raw cell millivolt value increases logarithmically as the O2 concentration decreases.

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