Rockwell Automation 1762-IR4 RTD/Resistance Input Module - Manual (Page 11)

1 Publication 1762-UM003A-EN-P - February 2003
Chapter
1
Overview
This chapter describes the four-channel 1762-IR4 RTD/resistance Input
module and explains how the controller reads resistance temperature
detector (RTD) or direct resistance-initiated analog input data from the
module. Included is:
•
a general description of hardware features
•
an overview of module and system operation
•
compatibility
General Description The 1762-IR4 module supports RTD and direct resistance signal
measurement applications that require up to four channels. The
module digitally converts analog data and then stores the converted
data in its image table.
The module supports connections from any combination of up to four
input devices. Each channel is individually configurable via software
for 2- or 3-wire RTD or direct resistance input devices. Channels are
compatible with 4-wire sensors, but the fourth sense wire is not used.
Two programmable excitation current values (0.5mA and 1.0mA) are
provided, to limit RTD self-heating. When configured for RTD inputs,
the module can convert the RTD readings into linearized digital
temperature readings in °C or °F. When configured for resistance
analog inputs, the module can convert voltages into linearized
resistance values in ohms. The module assumes that the direct
resistance input signal is linear prior to input to the module.
Each channel provides open-circuit (all wires), short-circuit (excitation
and return wires only), and over- and under-range detection and
indication.
IMPORTANT
The module accepts input from RTDs with up to 3
wires. If your application requires a 4-wire RTD, one
of the two lead compensation wires is not used, and
the RTD is treated like a 3-wire sensor. The third wire
provides lead wire compensation. See Chapter 2,
Installation and Wiring, for more information.