Reference Manual
748384-C
September 2003
1-44 Introduction
Rosemount Analytical Inc. A Division of Emerson Process Management
NGA2000 Reference
1-24 ALARM I/O MODULE GENERAL
INFORMATION
Information about this module may be found in
the Platform manual. However there are some
more subtle points not covered there.
Version V2.2 and earlier I/O modules had gen-
eral alarm functions, but were not capable of re-
sponding to specific analyzer conditions or of
giving analyzers specific commands. Version
2.3 and later I/O modules are capable of both of
these functions. They are controlled by a modi-
fication of the menu handling code in the V2.3
Platform Control module that is capable of put-
ting values from analyzer variables into the I/O
module menus, thus allowing the user to select
analyzer specific options.
Network variables: AM_INPUT, DI_MSGE,
ST1NAME, ST2NAME, STCONT
a. Setup
Procedure
Binding To Analyzers
See Section 1-2b on page 1-2 Binding.
Setting Up Analog Output
The analog output is available either as a
voltage or a current output. However only
one is meaningful at a time, the other one
will have incorrect readings even though it
is physically present.
You can setup the output to track the ana-
lyzer ranges, to change the analyzer ranges
automatically, or to report only one range
despite what range the analyzer is on. You
can also attach remote range control lines
to the I/O module and it will control the ana-
lyzer's range. See Section 1-3 on page 1-7
for more details on the ramifications of this.
b. Details
The analog output module is a self con-
tained computer that uses the Echelon Neu-
ron chip as its processor. It gets data from
the network, and it performs the necessary
calculations to produce the analog output
and the relay indications.
It updates its analog output at 100 micro
seconds intervals. The output circuit uses a
16-bit DAC, producing a resolution of about
0.3 mV or 1 uA.
Because it communicates to the analyzer
over the network, there are inherent delays
involved. If the remote range change option
is used, there will be a delay of about a half
of a second before the output responds to
the range change request.
The various diagnostic measurements are
made of the actual parameter measured.
They are not calculated based upon the de-
sired result, they are a direct measurement
of it, as close to the reality as possible.
Thus the output voltage is measured at the
output circuit just before the EMC protection
devices, and the relay states are measured
by inspecting the state of the second relay
contact.
The output current is measured as a voltage
across the output terminals. It may be re-
ported as a current by entering the load re-
sistance in the diagnostic screen. However
this is not a direct measurement of the cur-
rent.
In any case, the voltage measurements do
not have the resolution of the output cir-
cuits, and so should not be used to calibrate
the latter.