Rockwell Automation 1762-IR4 RTD/Resistance Input Module - Manual (Page 49)

Publication 1762-UM003A-EN-P - February 2003
Module Data, Status, and Channel Configuration 3-15
Selecting Temperature Units/Mode (Bit 7)
The module supports two different linearized, scaled temperature
ranges for RTDs, degrees Celsius (°C) and degrees Fahrenheit (°F).
You can select the type that is appropriate for your application by
setting bit 7 in the channel configuration word. Bit 7 is ignored for
resistance input types or when raw/proportional, scaled-for-PID, or
percent data formats are used.
Selecting Open-Circuit Response (Bits 5 and 6)
Broken inputs for the module include open-circuit and short-circuit
conditions. An open-circuit occurs when the module’s maximum input
voltage is reached. This can happen if the wire is cut or disconnected
from the terminal block. The module can encounter an open-circuit
for any RTD or resistance input.
A short-circuit occurs when the calculated lead wire compensated
resistance is less than 3
Ω
. The module can only report a short-circuit
for an RTD.
Use bits 5 and 6 of channel configuration word to define the state of
the channel data word when a broken input condition is detected for
the corresponding channel. When it detects an open circuit or a short
circuit, the module overrides the actual input data with the value that
you specify.
Table 3.6 Open/Broken Circuit Response Definitions
Open/Broken
Circuit Value Response Definition
Upscale Sets input to full upper scale value of channel data word. The full-scale
value is determined by the selected input type, data format, and scaling.
Downscale Sets input to full lower scale value of channel data word. The low scale
value is determined by the selected input type, data format, and scaling.
Last State Sets input to last input value.
Zero Sets input to 0 to force the channel data word to 0.