Fully Automatic Calibration - Emerson Rosemount 6888C Manual

Calibration
January 2023
If the electronics is used, it stores calibration data for the past ten successful
calibrations.
CAUTION
Reading errors
Make sure the calibration gas cap is replaced tightly after calibration is complete.
Many combustion processes operate at a slight negative pressure (draft pressure)
and can draw ambient air down the cal gas lines and into the sensing cell, causing
a falsely elevated O2 reading. The same phenomenon is possible if the calibration
gas hoses are permitted to become degraded or loose.
6.2

Fully automatic calibration

For fully automatic calibration, the Rosemount 6888Xi Electronics must manage
the actuation of solenoids to introduce gases into the probe.
6.2.1 Probe with standard electronics housing
In addition to the Rosemount
single probe sequencer (SPS), which is a solenoid box for switching calibration
gases or a larger intelligent multiprobe sequencer (IMPS) which can handle the
autocal for up to four probes in one box.
The automatic calibrations can be initiated in several ways:
• Calibration recommended diagnostic that is periodically checking cell
impedance.
• Push button on the Rosemount 6888 Xi Electronics.
• HART
• External contact closure.
• Time since the last successful calibration.
Note
To manually initiate an automatic calibration, select 9999 for CAL INTERVAL in the
setup menu.
If using the O
loop into manual prior to calibrating. Always inform the operator prior to
calibrating. The Rosemount 6888 Xi Electronics provides an in cal contact closure
for this purpose as well as an initiate cal contact.
The Rosemount 6888 Xi Electronics sequences the calibration gases in turn into
the sensing cell. A 300 second flow time is the factory default for both gases and
also for the purge cycle, which lets the probe signal come back to the normal
flue gas readings. The 4-20 mA signal representing O
calibration cycle or permitted to vary with the bottled gases, in which case a
record of the calibration can be trended at the DCS.
Calibration setup is found under the detailed setup menu.
56
™
communications from a Field Communicator or AMS.
®
measurement for automatic control, always place the O
2
6888 Xi, this arrangement requires a separate
Manual
00809-0100-4891
control
2
can be held during the
2
Rosemount 6888C