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

General
Description
NOTE
Chapter 1
Module Overview
This chapter describes the 1769sc-IR6I and the conformally coated 176sc-IF6IK
Isolated RTD/Resistance input modules and explains how the controller reads
resistance temperature detector (RTD) or direct resistance-initiated analog input
data from the modules. Other than the conformal coating, both modules are
identical so all information applicable to the 1769sc-IR6I also applies to the K
version. The following section covers:
• The module's hardware and diagnostic features.
• An overview of system and module operation.
• Compatibility.
The 1769sc-IR6I (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 to 42 mA and 1.0 mA) 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
wire provides lead wire compensation. See Chapter 2, Installation and
Wiring, for more information.
User's Manual Pub. 0300241-02 Rev. A