I
NITIAL
S
TARTUP AND
C
ALIBRATION
748250-L Rosemount Analytical October 1999
3-21
Model 880A Non-Dispersive Infrared Analyzer
The purge [PURGE: nnn MIN] display allows the user to select the amount of time for
the calibration gas to flow through the analyzer before the calibration starts for zero
and span or the amount of time for sample gas to flow through the analyzer before run
mode values are recorded when the sample and hold feature is selected. The
analyzer is calibrated during the final minute of purge time. During the remaining
purge time the signal is modified according to previous calibration data.
The repeat zero [RPT ZERO nnn HR] display allows the user to select the amount of
time between zero calibrations. This is the amount of time after the initial calibration
before the zero calibration is repeated without repeating the span calibration.
Note:
Each time an auto span calibration is made, a zero calibration is also made
regardless of selection.
The keyboard is disabled during the auto zero/span sequence.
During the auto zero/span sequence, the time constant is set to one second. Upon
completion of the calibration sequence, the time constant is reset to the value chosen
in Range Parameters.
In order to engage the Auto-Cal function with the Remote Range I/O, the Auto-Cal
function must be disabled by toggling AUTO-CAL to OFF in the [AUTO-CAL:OFF]
display.
The repeat span [RPT SPAN nnn HR] display allows the user to select the amount of
time between span calibrations. This is the amount of time after the initial span
calibration before this calibration is repeated.
The [DRIFT LIMIT: ON] display allows the user to determine the maximum amount of
span and zero drift allowable. The [ZR-DFT:
±
XX%] or [SP-DFT
±
XX%] display
allows the user to select the percentage of fullscale by
which the analyzer is allowed to drift from the reference span or zero calibration
values. The maximum zero drift limit is 10% fullscale and the maximum span drift is
15% fullscale.
In the linearized mode, these values should be obtained from the Response Curve for
Range located at the back of the manual. For the linear mode, locate the amount of
span or zero drift limit desired on the bottom scale and find the corresponding
Recorder Deflection value on the side scale. These are the values that should be
entered in [ZR-DFT:
±
XX%
→
←
] or [S-DFT:R#
±
XX%
←
].
Calibration drift calculations for all ranges toggled "ON" in the [Range: 1Y 2Y 3Y]
display include only calibrations occurring after initiation of the Calibration Drift
function. Two reference zero and/or span calibrations after initiation of the Calibration
Drift function are required for calculation of the Calibration Drift value.
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