COSA Xentaur Xentaur XDT - Manual (Page 31)

XDT User’s Manual
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in the bottle, for some bottles there is a cut-off pressure below which the dewpoint is not guar-
anteed. Make a note of the exact dewpoint of the reference gas as it will be required in the next
steps.
• Refer to the unshaded area of the flow diagram on the second page of Appendix A.
• Make sure the instrument is unlocked.
• Press the MODE button a few times until the display shows CAL.
• Press the DOWN button to select the Self Calibration mode. The display will show SLF/CAL
• Press the UP button to confirm entry into the Self Calibration mode. The display will show the
reference dewpoint which has been previously programed into the instrument, the SET and
DEWPOINT legends will also appear. Use the UP and DOWN buttons to modify this dew-
point to match the dewpoint of the reference gas.
• Press the MODE button, the display will alternately show 720 / HRS / INTR, indicating that
the calibrations are scheduled at 720 hours interval. Use the UP and DOWN buttons to change
the interval time to whatever is determined to be most effective for your application, consult
with your representative if you are in doubt. An interval of 0 Hrs (appears as a blank on the
display), disables any further scheduled unattended calibrations, however the instrument will
continue to make use of calibration values acquired previously or manually in the future.
Pressing the Pressure Correct button will cause the instrument to momentarily display 150 /
HRS / LEFT, indicating that there are 150 hours left until the next scheduled calibration is per-
formed. This is a useful indication in cases where it is not known when the next calibration
will be performed.
• Press the MODE button, the display will show BEG/S.C., prompting to begin the Self Calibra-
tion.
- If the MODE button is pressed the calibration procedure will be canceled and instrument
will go to the Serial Number mode. All setup will still be in effect, e.i. newly entered reference
dewpoints, the scheduled interval time etc. will still be used by the system.
- If the DOWN button is pressed the Self Calibration corrections will be disabled; any Self
Calibrations performed previously will not be used in correcting the computed dewpoint of
the instrument. However newly entered reference dewpoints and the scheduled interval time
will still be in effect; thus when the time elapses a Self Calibration will be performed and its
values will be used in correcting the computed dewpoint from that time on.
• Press the UP button to initiate the Self Calibration. the display will show CNF/SC?, prompting
for a confirmation that the Self Calibration should be performed.
If the DOWN or Pressure Correct buttons are pressed the Self Calibration will be aborted,
however everything set until now will remain in effect.
• Press the UP button to confirm the Self Calibration. The display will show SLF/CAL/-41.5
indicating that self calibration has started and it is measuring a dewpoint of -41.5°C, (this is
also the entry place into the procedure when the scheduled time elapses). Now the instrument
will “freeze” the analog output and the alarm relays so that they are not influenced by the ref-
erence gas dewpoint. Then the instrument will activate the electrically actuated switchover
valve and thus introduce the reference gas to the sensor, and initiate a 15 minute time out
allowing the system to reach equilibrium. (Since the program will perform the above when the
scheduled interval elapses, this step may be occurring in an unattended mode, thus the refer-
ence gas bottle and regulator must be left in the open positions, the switchover valve will keep
them from being exhausted.)
• After the 15 minute stabilization time out, the display will show alternately S.C./STB /-41.5,