Chapter 1 Overview; Section 1.1 General Description - Spectrum Controls 1769 User Manual

Section 1.1
General
Description
User's Manual Pub. 0300241-01 Rev. A
Chapter 1
Overview
This chapter describes the 1769sc-IR6I Isolated 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:
•
The module's hardware and diagnostic features
•
An overview of system and module operation
•
Compatibility
The isolated RTD/Resistance input module supports RTD and direct resistance signal
measurement applications that require up to six 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 six 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..42mA 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 (All wires work – resistance
ranges don't apply), and over- and under-range detection and indication.
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
Attention
wire provides lead wire compensation. See Chapter 3, Installation and
Wiring, for more information.