Publication 1794-6.5.12 - November 1997
Chapter
1
Overview of FLEX I/O and Your
Thermocouple/RTD/mV Input Module
What This Chapter
Contains
Read this chapter to familiarize yourself with the 1794-IRT8 module.
What the
Thermocouple/RTD/mV
Input Module Does
The 1794-IRT8 module accepts up to 8 thermocouple or RTD inputs. The
inputs are nonisolated and are selected with analog multiplexers which
have a common-mode input range of ±4 volts. The inputs will accept a
millivolt or resistive input. Default input spans are –40.00mV to
+100.00mV or 0.00 to 500.00 ohms. Fault Indicators are located on the
field side.
No switches or jumpers are used on the TC/RTD Input module. The
Inputs have both fixed hardware filters and selectable firmware digital
filters.
How TC/RTD/mV Modules
Communicate with
Programmable Controllers
FLEX I/O Thermocouple/RTD/mV modules are block transfer modules
that interface analog signals with any Allen-Bradley programmable
controllers that have block transfer capability. Block transfer
programming moves input or output data words between the module’s
memory and a designated area in the processor data table. Block transfer
programming also moves configuration words from the processor data
table to module memory.
The adapter/power supply transfers data to the module (block
transfer write) and from the module (block transfer read) using BTW and
BTR instructions in your ladder diagram program. These instructions let:
• the adapter obtain input or output values and status from the module
• you establish the module’s mode of operation.
The illustration describes the communication process.
For information on See page
What the Thermocouple/RTD/mV Input Module Does. . . . . . . . . 1-1
How the module communicates . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Module features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
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