Overview

This chapter describes the four-channel 1746-NR4 RTD/Resistance

Input Module and explains how the SLC controller gathers RTD

(Resistance 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-NR4 RTD/Resistance Input

Module is referred to as simply the RTD module.

Description

The RTD module receives and stores digitally converted analog data

from RTD units or other resistance inputs such as potentiometers into

its image table for retrieval by all fixed and modular SLC 500

processors. An RTD module consists of a temperature-sensing element

connected by two, three, or four wires that provide www.abb-drive.com input to the RTD

module. The module supports connections from any combination of

up to four RTD units 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 unit connected

to the module inputs (up to 4 input channels). The module provides

on-board scaling and converts RTD unit 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.