Rockwell Automation 1769-IF16V Compact High Density Analog Input Modules - Manual (Page 77)

Publication 1769-UM018A-EN-P - October 2008 77
Glossary
input or output. See the variation from the straight line due to linearity
error (exaggerated) in the example below.
number of significant bits – The power of two that represents the
total number of completely different digital codes an analog signal can
be converted into or generated from.
module scan time – same as module update time
module update time – The time required for the module to sample
and convert the input signals of all enabled input channels and make
the resulting data values available to the controller.
multiplexer – A switching system that allows several signals to share
a common A/D converter.
normal mode rejection – (differential mode rejection) A logarithmic
measure, in dB, of a device’s ability to reject noise signals between or
among circuit signal conductors.
normal operating range – Input or output signals are within the
configured range.
overall accuracy – The worst-case deviation of the output voltage or
current from the ideal over the full output range is the overall
accuracy. For inputs, the worst-case deviation of the digital
representation of the input signal from the ideal over the full input
range is the overall accuracy. this is expressed in percent of full scale.
Gain error, offset error, and linearity error all contribute to input and
output channel accuracy.
output accuracy – The difference between the actual analog output
value and what is expected, when a given digital code is applied to
the d/a converter. Expressed as a ± percent of full scale. The error
will include gain, offset and drift elements, and is defined at
25 °C (77 °F), and also over the full operating temperature range,
0…60 °C (0…140 °F).
repeatability – The closeness of agreement among repeated
measurements of the same variable under the same conditions.
Ideal Transfer
Actual Transfer
Function