Emerson NGA2000 - 2 Analog Output;3 Alarms; Overview

Instruction Manual
748275-F
September 2003
Rosemount Analytical Inc. A Division of Emerson Process Management Analog Output/3 Alarms
2-1
Model NGA2000 I/O Modules
SECTION 2
ANALOG OUTPUT/3 ALARMS
2-1 OVERVIEW
See Section 1 for information that applies to
all I/O Modules.
The Analog Output with 3 Alarms I/O Module
uses up to three of the SPDT relay outputs.
These outputs are configured as common,
normally open and normally closed.
Each of these alarms trips a relay to alert the
user that some variable is outside of the de-
sired range. Alarms can be set to trigger on
high/low, high/high, low/low or just single high
or low setpoints.
Alarm deadband is also a software program-
mable item with an upper limit of 20% of
fullscale.
There are four alarm categories: Gas Concen-
tration, Warning or Failure, Status and Valid-
ity.
Gas Concentration
Gas concentration can be expressed as a
percentage of the current range or as an ab-
solute value. Alarms can be set to alert the
user of low concentration, high concentration
and percent of range values.
Warning or Failure
Warning indicates one or more software con-
figured limits on any network variable (other
than gas concentration) has been exceeded.
Examples of these secondary variables are
flow rate and internal voltage. A software re-
set or other resolved software failure would
also be reported.
Failure indicates an unrecoverable hardware
or software failure (i.e., some component is
not responding to network communications or
a safety related failure such as lack of purge
air in a Flame Ionization Detection Analyzer
Module has been noted).
In the event of a Warning or Failure alarm,
gas concentration values displayed on the
Operator Interface or present on output lines
are accurate.
Status
Status can describe either Maintenance or
Calibration Mode.
Maintenance - a user enters the menu sys-
tem; this can be sued to alert the system of
unauthorized entry.
Calibration Mode - alerts the user that the
Analyzer Module is being calibrated.
Gas concentration values are accurate.
Validity
Validity describes a condition in which gas
concentration values present on the Operator
Interface or output lines should be considered
invalid. The Analyzer Module alerts the sys-
tem that an error in gas concentration is pre-
sent.
See Figure 2-1 for a flowchart depicting menu
screens related to this I/O Module.