Emerson Rosemount 6888C Instruction Manual page 53

Instruction Manual
00809-0100-4891
6.2.2 Rosemount 6888 Probe with integral autocal housing
This probe contains the autocal solenoids within the blue electronics housing, eliminating
the need and cost for an SPS or IMPS solenoid enclosure. Both calibration gases are
permanently piped into two ports on the probe. It's important to confirm that there are no
piping leaks or the calibration bottles will leak down permanently.
NOTICE
The calibration sequence from the Rosemount 6888 Xi Electronics is identical to that for
the manual/semiautomatic calibration, but note that with the integral autocal version of
this probe it is not possible to conduct a manual calibration. The factory offers a probe
rebuild capability if solenoid or other failures occur.
CAUTION
LEAKS
Calibration gas bottles ARE piped and under pressure at all times, so be sure to leak-check
all fittings, tubing, and connections. Always use dual-stage pressure regulators.
6.2.3 Other features associated with calibration
1. Cal Check capability - You can choose to look at new calibration values prior to having
them load in and become active. If this feature is selected, a calibration changed
alarm comes up after the calibration is complete. Push Diagnostics button on the
Rosemount Xi to require an Accept Cal stepso that the technician and operator can
decide if they are ready to accept a potentially large change in calibration values.
2. Plugged diffuser diagnostic - this feature measures the return-to-process rate after
calibration gases are removed and will alarm when this time exceeds 75% of the purge
time configured. A purge time too short alarm is an indication that the diagnostic
could not work because of a short purge time and is another indication that the diffuser
is plugged. Increase purge time in this case.
Another feature that comes with the plugged diffuser diagnostic is auto gas switching.
This feature switches cal gases and also ends the purge sequence when the readings
settle out vs. waiting for a configured flow time. This saves time and gas.
3. Tolerance check - alarms if the cell mV signal is significantly different from the
expected signal of the bottles noted in the setup. This indicates if the wrong bottles are
being used or if a bottle runs out in the middle of a calibration.
Calibration setup is under the Detailed Setup menu on the Rosemount Xi menu. See
Figure
Instruction Manual
6-1.
Calibration
July 2018
53