Rockwell Automation 1756-XXXX ControlLogix Analog I/O Modules - Manual (Page 363)

Publication 1756-UM009C-EN-P - December 2010 363
Additional Specification Information Appendix E
Error Calculated Over
Hardware Range A ControlLogix analog I/O module’s calibration accuracy at 25 °C (77 °F) is
calculated over the full hardware range of the module and is not dependent on
the application’s use of the range. The error is the same if you are measuring it
across a 10% or 100% portion of a given range.
However, a module’s accuracy at 25 °C (77 °F) is dependent on the hardware
range in which the module operates.
How Operating
Temperature Changes
Affect Module Accuracy The following specifications take into account how the module’s operating
temperature changes can affect a module’s accuracy.
• Gain Drift With Temperature
• Module Error Over Full Temperature Range
Gain Drift With Temperature
The Gain Drift with Temperature specification represents the calibration
inaccuracy that occurs as a module’s ambient (that is, operating) temperature
drifts from the temperature at which it was calibrated.
You can use the Gain Drift with Temperature specification (varies for each
catalog number) to determine the module’s calibration inaccuracy for each
degree between calibration and operating temperature. The Gain Drift with
Temperature specification represents a percentage of the full operating range
that the module’s calibration is inaccurate to for each degree difference. The
specification is determined with the following formula:
Gain Drift with Temperature = (PPM/°C) x Module’s Full Range
EXAMPLE
The 1756-IT6I module offers two input ranges, -12…30 mV and
-12 …78 mV. Because module error at 25 °C (77 °F) depends on
the input range used, the module error is as follows when using
0.1% of range accuracy:
• +/- 42 mV for the -12…30 mV range
• +/- 90 mV for the -12…78 mV range
These error values are the same whether you use 10% or 100%
of the chosen range.