Rockwell Automation 1746-NR8 SLC 500 RTD/Resistance Input Module User Manual User Manual

Page 110

Publication 1746-UM003A-EN-P

Glossary 2

excitation current

excitation current - A user-selectable current (0.25 mA and 1.0 mA) that the
module sends through the RTD or resistive device to produce an analog signal
which the NR8 can process and convert to temperature or to ohms,
respectively.

effective resolution

effective resolution - The amount of jitter (data variation) that typically
occurs in the data word due to the influence of the internal electrical noise in
the module.

filter frequency

filter frequency - The user-selectable stop-band frequency for the A/D
converter’s digital filter. The digital filter provides AC power line noise
rejection when the first notch is at 10 Hz or at the power line frequency.

full scale error (gain error)

full scale error (gain error) - The difference in slope between the actual and
ideal potentiometer or RTD transfer functions.

full scale range (FSR)

full scale range (FSR) - The difference between the maximum and minimum
specified analog RTD or resistive input values.

gain drift

gain drift - The change in full scale transition voltage measured over the
operating temperature range of the module.

input data scaling

input data scaling -The data formats that you select to define the logical
increments of the channel data word. These may be scaled-for-PID, or
Engineering Units for RTD or potentiometer inputs, which are automatically
scaled. They may also be proportional counts, which you must calculate to fit
your application’s temperature or resistance resolution.

local configuration

local configuration - A control system where all the chassis are located within
several feet of the processor and chassis-to-chassis communication is via a
1746-C7 or 1746-C9 ribbon cable.

LSB (Least Significant Bit)

LSB (Least Significant Bit) - Refers to a data increment defined as the full
scale range divided by the resolution. The LSB represents the smallest value
within a string of bits.

multiplexer

multiplexer - A switching system that allows several input signals to share a
common A/D converter.

normal mode rejection (differential mode rejection)

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, but not between equipment grounding conductor or
signal reference structure and the signal conductors.

potentiometer (Pot)

potentiometer (Pot) - A variable resistor that can be connected to the RTD
module.

remote configuration

remote configuration - A control system where the chassis can be located
several thousand feet from the processor chassis. Chassis communication is via
the 1747-SN Scanner and 1747-ASB Remote I/O Adapter.