Emerson Rosemount 6888C Quick Start Manual page 29

October 2019
The Rosemount 6888 Xi displays several screens while saving the
configuration, resets itself, and then returns to the main screen.
2.5 Calibration
2.5.1 Manual/semi-automatic calibration
A technician can calibrate the Rosemount 6888 probe with standard housing
by following prompts via the display of the Rosemount 6888 Xi Electronics
or via HART
technician needs to manually switch the gases based upon these prompts.
Emerson recommends using 0.4% O
calibration gases. Always use a two-stage pressure regulator set to 20 psi.
Set the calibration gas flow meter for a maximum of 5 scfh with the cal gas
fitting removed from the probe. A diffuser/filter that is plugged over time
may cause the flow meter to deliver less flow to the sensing cell, but never
readjust the flow rate until a new diffuser is installed. Readjusting the flow
meter back up to the 5 scfh level could pressurize the cell during calibration
and cause the O
The electronics determine if the calibration was successful and calculate new
calibration values. New calibration values are not automatically loaded into
the electronics after a successful calibration, however. The technician has
the opportunity to accept or reject the new values.
CAUTION
Reading errors
A loose or missing cap can permit fresh air to bias the O
processes that run at negative pressure.
Make sure the calibration gas port is capped tightly between calibrations.
2.5.2 Fully automatic calibration
For fully automatic calibration, the Rosemount
manage the actuation of solenoids to introduce gases into the probe.
Probe with standard electronics housing
In addition to the Rosemount
separate 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.
Quick Start Guide
®
communications to a Field Communicator or AMS console. The
reading to shift downwards.
2
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and 8% O , balance nitrogen as
2 2
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6888 Xi Electronics must
6888 Xi, this arrangement requires a
Quick Start Guide
readings high in
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