Rockwell Automation 1790P-4R0 CompactBlock LDX I/O RTD/Resistance Input Module - Manual (Page 69)

Publication 1790-UM002A-EN-P
G-3
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 smallest detectable change in a measurement, typically
expressed in engineering units (e.g. 1°C) or as a number of bits. For
example a 12-bit system has 4096 possible output states. It can therefore
measure 1 part in 4096.
RTD – Resistance temperature detector. A temperature-sensing device that
consists of a temperature-sensing element connected by two, three, or
four lead wires that provide input to the module. The RTD uses the basic
concept that the electrical resistances of metals increase with temperature.
When a small current is applied to the RTD, it creates voltage that varies
with temperature. The module processes and converts this voltage into a
temperature value.
sampling time – The time required by the A/D converter to sample an
input channel.
step response time – The time required for the channel data word signal
to reach a specified percentage of its expected final value, given a
full-scale step change in the input signal.
update time – see “module update time”