General Diagnostic Features

The thermocouple/mV module contains diagnostic features that can

help you identify the source of problems that may occur during

power-up or during normal channel operation. These power-up and

channel diagnostics are explained in chapter 7. Module Diagnostics

and Troubleshooting.

System Overview

The thermocouple module communicates to the SLC 500 processor

through the parallel backplane interface and receives +5V dc and

+24V dc power from the SLC 500 power supply through the

backplane. No external power supply is required. You may install as

many thermocouple modules in your system as the power supply can support.

Each individual channel on the thermocouple module can receive

input signals from thermocouple sensors or mV analog input devices.

You configure each channel to accept either input. When configured

for thermocouple input types, the thermocouple module converts the

analog input voltages into cold-junction compensated and linearized,

digital temperature readings. The 1746-NT4 uses the National Bureau

of Standards (NBS) Monograph 125 and 161 based on IPTS-68 for

thermocouple linearization.

When configured for millivolt analog inputs, the module converts the

analog values directly into digital values. The module assumes that the

mV input signal is already linear.