1746-NR8 SLC 500™ RTD/Resistance Input Module

This chapter describes the 8-channel 1746-NR8 RTD/Resistance Input 1746-NR8 RTD/Resistance Input 1746-NR8 RTD/Resistance Input Module and explains how the SLC controller gathers RTD (Resistance Module
Temperature Detector) temperature or resistance-initiated analog input from the module. Included is:
• a general description of the module’s hardware and software features
• an overview of system operation
For the rest of the manual, the 1746-NR8 RTD/Resistance Input Module 1746-NR8 RTD/Resistance Input Module 1746-NR8 RTD/Resistance Input Module is referred to as simply the RTD module. RTD module
The RTD module receives and stores digitally converted analog data from RTDs or other resistance inputs such as potentiometers into its image table for retrieval by all fixed and modular SLC 500 processors. An RTD consists of a temperature-sensing element connected by 2, 3, or 4 wires that provide input to the RTD module. The module supports connections from any combination of up to eight RTDs of various types (for example: platinum, nickel, copper, or nickel-iron) or other resistance inputs.

The RTD module supplies a small current to each RTD connected to the module inputs (up to 8 input channels). The module provides on-board scaling and converts RTD input to temperature (°C °F or reports resistance input in ohms.
Each input channel is individually configurable for a specific input device. Broken sensor detection (open- or short-circuit) is provided for each input channel. In addition, the module provides indication if the input signal is out-of-range. For more detail on module functionality, refer to the subsection entitled System Overview System Overview later in this chapter.