COSA Xentaur Xentaur XDT - Manual (Page 30)

Section 3: Instrument
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a repetitive timer scheduled basis. The user interface for both is the same, with additional steps for
interval setting and automatic stabilization time outs for the instrument with the electrically actu-
ated valve.
Manual Single Point Self Calibration procedure for instruments without electrically actu-
ated switchover valve:
•
Refer to the unshaded area of the flow diagram on the second page of Appendix A.
• Expose the sensor to a known dewpoint
• Wait at least 15 minutes for the sample system to be stable, if the known gas is of a low dew-
point the waiting time may have to be increased - specially if the sensor was wet before the
procedure is initiated. Consult with your representative to determine sufficient waiting time
for your application.
• 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 known gas to which the sensor is exposed.
• 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 will be canceled and instrument will go to the
Serial Number mode. All setup will still be in effect, e.i. newly entered reference dewpoint
will remain in the instrument’s memory.
If the DOWN button is pressed the Self Calibration corrections will be disabled; any Self Cal-
ibrations performed previously will not be used in correcting the computed dewpoint of the
instrument.
• 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.
• Press the UP button to confirm the Self Calibration. The display will show alternately S.C./
STB /-41.5, indicating that Self Cal Stabilization is being checked and currently the instru-
ment is measuring -41.5°C. When the measured dewpoint is stable within 0.5°C for 3 minutes
the instrument will record the new single point self calibration values and finish by going to
the display dewpoint mode. Note that the program will spend at least 3 minutes on this stage
of the calibration.
• The sensor may now be exposed to the sample gas and the instrument will display the mea-
surement using the newly acquired calibration values.
Scheduled Timer Activated Single Point Self Calibration procedure for instruments with
electrically actuated switchover valve and on-board battery backed real-time clock:
•
Make sure that your sample system is properly connected according to the sample system
instructions. When the time-outs and stabilization times are summed from the calibration
stages below, it can be determined that the calibration reference gas will be used for at least 18
minutes, the user should make sure that there is sufficient amount of gas available. If the refer-
ence gas is provided from a compressed gas bottle, make sure that there is sufficient pressure