52 Input/Output Modules
Trident Planning and Installation Guide
Analog Input Module
The following analog input components are available.
The Analog Input (AI) Module has three independent input channels. Each input
channel receives variable voltage signals from each point, converts them to digital
values, and transmits the values to the three MPs on demand. One value is then
selected using a mid-value selection algorithm to ensure correct data for every
scan. Sensing of each input point is performed in a manner that prevents a single
failure on one channel from affecting another channel.
The AI Module sustains complete, ongoing diagnostics for each channel. If the
diagnostics detect a failure on any channel, the module’s Fault indicator is
activated, which in turn activates the system alarm. The Fault indicator points to a
channel fault, not a complete module failure. The AI Module is guaranteed to
operate properly in the presence of a single fault and may continue to operate
properly with multiple faults.
The AI Module supports hot sparing for online replacement of a faulty module or
continuous back-up to an active module. The AI Module is mechanically keyed to
prevent improper installation in a configured baseplate.
Model Description Current Type
3351 Analog Input Module 4–20 mA Commoned
2351 Analog Input Baseplate Direct Termination
2352 Analog Input External
Termination Panel Baseplate
External Signal Conditioners
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