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Calibration 5
IR7000
52
Teledyne Analytical Instruments., - Rev. 3
linearized at the factory, a maximum delta using a full span gas
(100%) is determined and permanently burned into memory.
This value is used to compare subsequent readings (real or
calibration) to determine if:
A) The reading is real and not an anomaly.
B) In the case of a calibration, the calibration yielded valid
data i.e. the delta obtained is within 30% of the maximum
delta determined at the factory. If not, a calibration alarm
message is displayed and the old calibration values are
restored. See Section 5.4.
•
Drift
During calibration, approximately 40 readings are taken in 20
seconds. The imbedded software looks at the difference of 39
pairs of successive readings i.e. reading #1 – reading #2,
reading #2 – reading #3 etc., and analyzes these successive
pairs in terms of their spread about 0. If the system is stable as
it should be during calibration, then theoretically, these
readings should all be 0 or close to it although there may be
some spread about 0. If the number of pairs that are increasing
are seriously out of balance with the number that are
decreasing, the software generates an error depending on the
nature of the imbalance. If the number of increasing values is
much greater than the number of decreasing values, the
software will assume that the system is drifting. It will
immediately reset and attempt to recalibrate. There will be a
maximum of 5 attempts at recalibration before an alarm
condition is displayed and the system restores the old
calibration values.
In this case, you may receive an “
IR LOWFLOW FAIL
”
alarm. Most often, this is due to an insufficient purge of the
sample cell prior to calibration. Increase the CAL DELAY time
significantly and try again.
NOTE:
If an alarm condition is encountered, the alarm latches in the sense
that the message will only go away when the condition is corrected
AND the alarm is acknowledged. Correcting the conditions of the
alarm only will NOT clear the alarm message. Acknowledging the
alarm only will NOT clear the alarm. YOU MUST DO BOTH! To
acknowledge any alarm, press the UP button on the front display.