Rockwell Automation 1756-XXXX ControlLogix Analog I/O Modules - Manual (Page 362)

362 Publication 1756-UM009C-EN-P - December 2010
Appendix E Additional Specification Information
Calibrated Accuracy The Calibrated Accuracy specification represents the module’s accuracy
when its ambient (that is, operating) temperature is the same as the
temperature at which the module was calibrated.
Immediately following a calibration, a ControlLogix analog I/O module is
most accurate. Because the module was calibrated at its zero and span, the
inaccuracy is largely non-linearity between zero and span. Assuming the
module is operating at the exact temperature when it was calibrated and uses
the same voltage source to check the post-calibration accuracy, a module may
be as accurate as 0.01…0.05% of range.
Once the module begins operation, its accuracy lessens as components change
over time. However, this change (in components or accuracy) is different from
the Gain Drift With Temperature specification described on
page 363 .
Other than non-linearity, the Calibrated Accuracy @ 25 °C (77 °F)
specification represents a time drift/aging specification between calibrations.
A module with a calibration accuracy of 0.01% of range immediately following
calibration is estimated to be better than 0.1% of range @ 25 °C (77 °F) for
one year (that is, the calibration cycle).
The reason for the difference between 0.01% and 0.1% of range is that the
Calibrated Accuracy @ 25 °C (77 °F) specification must capture the effect of
component aging until the next time the module is calibrated. Primarily, the
module's operating conditions, such as temperature, humidity, and power
cycling, affect component aging.
Because ControlLogix analog I/O modules operate in different conditions, the
specific accuracy deviation from 0.01% of range cannot be measured.
Typically, however, a module’s Calibrated Accuracy @ 25 °C (77 °F) is closer
to 0.05% of range than 0.1% of range as the 0.1% of range is determined by
the worst case scenario operating conditions.