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5-25GFK-0787B Chapter 5 Diagnostics
Fault, No Fault, and Alarm Contacts
Fault and No Fault contacts can optionally be used to detect fault or lack of fault
conditions on a discrete (%I or %Q) or analog (%AI or %AQ) reference. They can also be
programmed with the Series 90-70’s built-in fault-locating references. In a GMR system,
there are fault contacts associated with voted inputs, with the original block inputs, and
with logical outputs. Alarm contacts can also be used to detect high or low alarm
conditions on an analog (%AI or %AQ) reference. See the Programming chapter for
information about using these contacts.
Discrete Input Fault Contacts for GMR
In the discrete Input Table there are fault contacts associated with each item of voted
input data, non-voted input data, and “raw” data input from bus A, B, and C:
Discrete Input Table
Voted Inputs
Non-voted Inputs
Input
Voting
Logic
Bus A inputs
A
B
C
Bus B inputs
Bus C inputs
Reserved inputs
Conditions that Cause these
Fault Contacts to be Set
Any fault
Genius fault
Autotest fault
Genius fault
Autotest fault
Discrepancy fault
Genius fault
Autotest fault
Discrepancy fault
Genius fault
Autotest fault
Discrepancy fault
Genius fault
•
•
•
•
•
•
•
•
•
•
•
•
•
(see text below)
Conditions that Cause Discrete Input Fault Contacts to be Set
For more information about fault contacts, see page 7-21.
For the voted input, a fault contact is set if any of the physical inputs has an
associated fault contact set. For example, if a there is an autotest fault on input A, a
fault contact is set both for input A and for the voted input.
For non-voted inputs, the single fault contact is associated with the physical input. It
is set under the following conditions:
Autotest fault. Set on digital inputs configured for autotesting, if autotesting
detects a fault.
Genius faults, including Loss of Block.
Line fault. These are a feature of the 16-circuit DC blocks. To report line faults, an
input must be configured for tristate operation.
For blocks in GMR mode, a line fault represents a short circuit fault on the field wiring.
For non-GMR blocks, a line fault represents an open circuit fault in the field wiring.
For bus A, bus B, and bus C inputs, fault contacts are set under the following conditions:
Autotest fault (see above).
Line fault (see above).
Genius faults, including Loss of Block.
Discrepancy between the raw input data, and the corresponding voted input.