170 Rockwell Automation Publication 1756-UM540E-EN-P - December 2017
Chapter 9 Troubleshoot Your Module
Troubleshoot Incorrect
Readings on the Module
Incorrect temperature, current, or voltage readings on temperature-sensing and
current/voltage I/O modules are often considered to be the result of a module
needing to be calibrated. This is typically not the case.
ControlLogix analog I/O modules are calibrated before shipment from the
factory and maintain a high degree of module accuracy throughout their lifespan.
Additionally, 1756-IRT8I module channels that are configured for
Thermocouple inputs perform a resistance self-calibration when the module
power is cycled.
The following sections describe tasks that you can use to troubleshoot
your module:
• 1756-IRT8I and 1756-IT16 Modules - Incorrect Temperature Readings
• 1756-IRT8I and 1756-IR12 Modules - Incorrect RTD Readings
• 1756-IF8I Module - Incorrect Input Voltage/Current Readings
• 1756-OF8I Module - Incorrect Output Voltage/Current Readings
1756-IRT8I and 1756-IT16 Modules - Incorrect Temperature Readings
To determine the cause of the incorrect reading, first determine the nature of the
incorrect reading. For example, the module can perform as follows:
• The module always reads maximum.
• The module always reads minimum.
• The module reads erratically (data jumping around).
• The module reads with an offset over the entire range.
First, complete the following tasks.
1. To verify that the module is powered and communicating, check the status
indicators.
Red or flashing green status indicators indicate a problem. For more
information on the module status indicators, page 166
.
2. Check the module wiring to verify the following:
– The wiring is correct.
– The wiring is intact.
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