Rockwell Automation 1794-IRT8XT FLEX I/O Thermocouple/RTD /Millivolt Input Module User Manual - Manual (Page 42)

Publication 1794-6.5.12 - September 2011
30 Read and Write Configuration Maps for the FLEX I/O Module
You select individual channel ranges using write word 1 of the block transfer
write instruction.
Read Data From the Module Read programming transmits status and data from the TC and RTD input
module to the processor data table in one I/O scan. The processor user
program initiates the request to transfer data from the TC and RTD input
module to the processor.
Map Data for the Module The following read and write words and bit/word descriptions describe the
information written to and read from the TC and RTD input module. The
120 Ω Nickel α = 0.00672 (-80 … +320 °C) (-112…608 °F) R -50 … 1768 °C (-58 … 3214 °F)
10 Ω Copper α = 0.00427 (-200 … +260 °C) (-328…500 °F) S -50 … 1768 °C (-58 … 3214 °F)
T -270 … 400 °C (-454 … 752 °F)
RTD Type Thermocouple Type
ATTENTION
Disconnecting and reconnecting RTDs with power applied temporarily
disturbs the steady state data of the channel. Allow 2 minutes for
settling time or cycle power to the module after terminating
connections.
ATTENTION
If using RTD isolators, we recommend using 2- or 4-wire
configurations only and digital filtering to the inputs.
WARNING
The range -32768…32767 should only be used with mV selection.
Signals from a thermocouple or RTD are non-linear, the mV selection is
not recommended for thermocouple or RTD real time readings.
If selected, the module will return the mV generated by the
thermocouple or RTD, in addition to any offsets generated by wiring
without any correction for the non-leanearity of the device.
Also, when the module is configured for mV the CJC compensation is
not applied for thermocouple devices.
For thermocouples and RTDs you should use F or C data format. When
configured as thermocouple or RTD the module will use an internal
table to adjust for the non-linear mV returned by the field devices.
After the internal calculations are preformed the module will provide
results in degrees F or C.