User Manual

Publication 1746-UM003A-EN-P
4-16 Channel Configuration, Data, and Status
The following two tables show the data resolution provided by the 1746-NR8
for resistance input types using the various data formats.
Table 4.18 Channel Data Word Resolution for 150Ω
ΩΩ
Ω Resistance Input
Table 4.19 Channel Data Word Resolution for 500
Ω
ΩΩ
Ω, 1000Ω
ΩΩ
Ω, and 3000Ω
ΩΩ
Ω Resistance
Inputs
Broken Input Selection (Bits 6 and 7)
The next table shows the descriptions for bits 6 and 7. The broken input bit
field lets you define the state of the channel data word when an open-circuit or
short-circuit condition is detected for that channel.
An open-circuit condition occurs when the RTD or potentiometer or its
extension wire is physically separated or opened. This can happen if the wire is
cut or disconnected from the terminal block.
The short-circuit condition applies only to RTD input types. This can happen
if the RTD or its signal wires are shorted together for any reason. The
short-circuit condition does not apply to resistance ranges since they start at 0
ohms, which can be a short-circuit condition.
Table 4.20 Bit Descriptions for Broken Input Selection
Resistance
Input Type
Data Format (Bits 4 and 5)
Engineering Units
x 1
Engineering
Units x 10
Scaled-for-PID Proportional
Counts
(Default)
Ohms Ohms Ohms Ohms
150
Ω 0.01Ω/step 0.1Ω/step 0.0092Ω/step 0.0023Ω/step
Resistance
Input Type
Data Format (Bits 4 and 5)
Engineering Units
x 1
Engineering
Units x 10
Scaled-for-PID Proportional
Counts
(Default)
Ohms Ohms Ohms Ohms
500
Ω 0.1Ω/step 1Ω/step 0.0305Ω/step 0.0076Ω/step
1000
Ω 0.1Ω/step 1Ω/step 0.0610Ω/step 0.0153Ω/step
3000
Ω 0.1Ω/step 1Ω/step 0.1831Ω/step 0.0458Ω/step
Binary
Value
Select Description
00 Zero Force the channel data word to 0 during an open-circuit condition
or short-circuit condition.
01 Upscale Force the channel data word value to its full scale value during an
open-circuit or short-circuit condition. The full scale value is
determined by the input type, data format, and scaling selected.
10 Downscale Force the channel data word value to its low scale value during
an open-circuit or short-circuit condition. The low scale value is
determined by the input type, data format, and scaling selected.