Allen-Bradley 1756-IF8I, User Manual, Page: 34 / 226

34 Rockwell Automation Publication 1756-UM540E-EN-P - December 2017
Chapter 2 Analog I/O Module Features
Calibrated Accuracy
The calibrated accuracy specification represents the module’s accuracy when its
ambient temperature is the same as the temperature at which the module
was calibrated.
For individual module specifications, see the ControlLogix I/O Module
Specifications Technical Data, publication 1756-TD002 .
Error Calculated over
Hardware Range
The calibration accuracy of a ControlLogix analog I/O module at 25 °C (77 °F)
is calculated over the full hardware range of the module. It 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.
RTD and Thermocouple
Error Calculations
When you use the 1756-IRT8I, 1756-IR12 or 1756-IT16 module in temperature
mode, error calculations are achieved by a two-step process.
1.
Calculate the module’s error in ohms or volts.
2.
Convert the ohm/volt error to temperature for the specific sensor and at
the correct application temperature.
Specification Description
Calibrated accuracy at 25 °C (77 °F) This specification matches the temperature at which the module was
calibrated in the factory during manufacturing.
Module error over full temperature range This specification represents the error that occurs if the module’s
ambient temperature changes a total of 60 °C (140 °F), that is, from
0…60 °C (32…140 °F) or 60…0 °C (140…32 °F).
EXAMPLE
When the 1756-IRT8I channel uses the Thermocouple (mV) input type, the
input range is -100…100 mV, the module error is 0.2 mV
when using 0.1%
of range accuracy.
These error values are the same whether you use 10% or 100% of the
chosen range.