Rockwell Automation 1762-IT4 Thermocouple/mV Input Module - Manual (Page 137)

Publication 1762-UM002A-EN-P - July 2002
Glossary G-3
is expressed in percent full-scale input. See the variation from the
straight line due to linearity error (exaggerated) in the example below.
LSB – Least significant bit. The LSB represents the smallest value
within a string of bits. For analog modules, 16-bit, two’s complement
binary codes are used in the
I/O image. For analog inputs, the LSB is defined as the rightmost bit of
the 16-bit field (bit 0). The weight of the LSB value is defined as the
full-scale range divided by the resolution.
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 processor.
multiplexer – An 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. The measurement does not apply to
noise signals between the equipment grounding conductor or signal
reference structure and the signal conductors.
number of significant bits – The power of two that represents the
total number of completely different digital codes to which an analog
signal can be converted or from which it can be generated.
overall accuracy – The worst-case deviation of the digital
representation of the input signal from the ideal over the full input
range is the overall accuracy. Overall accuracy is expressed in percent
of full scale.
repeatability – The closeness of agreement among repeated
measurements of the same variable under the same conditions.
resolution – The increment of change represented by one unit.
For example, the resolution of engineering units x1 is 0.1° and the
resolution of raw/proportional data is equal to
(maximum_value - minimum_value)/65534.
Ideal Transfer
Actual Transfer
Function