Rockwell Automation 1746-NR4 SLC RTD/Resistance Input Module User Manual - Manual (Page 75)

Publication 1746-UM008B-EN-P - December 2006
Channel Configuration, Data, and Status 75
Broken Input Selection (Bits 6 and 7)
The Bit Descriptions for Broken Input Selection 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.
Channel Data Word Resolution for 500 Ω, 1000 Ω, and 3000 Ω Resistance Inputs
Resistance Input
Type
Data Format (Bits 4 and 5)
Engineering Units x 1 Engineering Units x 10 Scaled-for-PID
Proportional
Counts (Defaults)
Ohms Ohms Ohms Ohms
500 Ω 0.1 Ω / step 0.1 Ω / step 0.0305 Ω / step 0.0076 Ω / step
1000 Ω 0.1 Ω / step 0.1 Ω / step 0.0610 Ω / step 0.0153 Ω / step
3000
Ω 0.1 Ω / step
0.1
Ω / step
0.1831
Ω / step
0.0458
Ω / step
Bit Descriptions for Broken Input Selection
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 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.
11 not used