Rockwell Automation 1790P-4R0 CompactBlock LDX I/O RTD/Resistance Input Module - Manual (Page 7)

1 Publication 1790-UM002A-EN-P
Chapter
1
Overview
This chapter describes the four-channel 1790D-4R0/T4R0 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 1790D-4R0/T4R0 (1790P-T4R0) 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. 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) 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.