Rockwell Automation 1762-IR4 RTD/Resistance Input Module - Manual (Page 95)

Publication 1762-UM003A-EN-P - February 2003
Glossary 5
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”