Rockwell Automation 1790D-NOV2/TNOV2 CompactBlock LDX Analog Modules - Manual (Page 96)

Publication 1790-UM001A-EN-P - March 2002
Glossary 2
input image – The input from the module to the controller. The input
image contains the module data words and status bits.
LSB – (Least Significant Bit) The bit that represents the smallest value
within a string of bits.
For analog modules, the LSB is defined as the rightmost bit, bit 0, of
the 16-bit field.
linearity error – An analog input or output is composed of a series
of voltage or current values corresponding to digital codes. For an
ideal analog input or output, the values lie in a straight line spaced by
a voltage or current corresponding to 1 LSB. Any deviation of the
converted input or actual output from this line is the linearity error of
the input or output. The linearity is expressed in percent of full scale
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 – For input modules, 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
processor. For output modules, the time required for the module to
receive the digital code from the processor, convert it to the analog
output signal, and send it to the output channel.
multiplexer – An switching system that allows several signals to
share a common A/D or D/A converter.
normal operating range – Input or output signals are within the
configured range. See for a list of input and output types/ranges.
Ideal Transfer
Actual Transfer
Function