HIM
18
The Interface Solution Experts
Smart HART
Loop
Interface and Monitor
Alarms Tab
The Alarms tab controls the programmable alarm
trip(s) option. This screen will be grayed out if the
attached HIM is not equipped with at least one alarm
trip. To program the Alarm parameters, change the
settings in the
Alarm1
and/or
Alarm2
box, then press
Quick Set
. The sections of the screen are described
below.
Trip/Fault Alarms
A
Trip Alarm
monitors a selected variable and trips
either when the variable exceeds a set value (Trip
High) or when the variable falls below a selected
value (Trip Low). The
Source
specifies which variable
will be monitored, while the
Trip Point
sets the point
at which the alarm will trip. After the alarm trips, the
Dead Band
determines how far past the trip point the
variable will have to go before the alarm condition
returns to normal.
There are two types of Fault Alarms. A
HIM Fault
Alarm
monitors the health of the HART monitor. It will
trip whenever the internal error status word is set.
For example, if the HIM’s configuration file becomes
corrupt, this alarm will trip and the monitor will display
BAD_CONFIG.
A
Field Device Fault Alarm
monitors
the health of the HART transmitter. This fault alarm will
trip for any of these eight malfunctions:
Device Malfunction (Bit 7)
Figure 11.
Alarms Tab
Relay trips whenever it detects that a hardware error or
failure has occurred in the connected HART device.
Configuration Changed (Bit 6)
Relay trips whenever it detects that the connected
HART device has had its configuration changed.
Cold Start (Bit 5)
Relay trips whenever the power to the HART device
is interrupted. It will also trip during a HART Master
Reset or Self Test Command.
Additional Status (Bit 4)
Relay trips whenever the connected HART device
reports a condition requiring HART Command #48,
which is Read Additional Information. This indicates
that the instrument needs attention from a device with
full HART command capability.
Output Current Fixed
(Bit 3)
Relay trips whenever the HIM detects that the
connected HART device’s output is no longer
responding to changes in its input, and is being held at
a predefined level.
PV Analog Output Saturated (Bit 2)
Relay trips whenever it detects that both its analog
and digital representations of the Primary Variable are
outside rated operating limits, and no longer reflect the
true sensor input.
Non-PV Out of Limits (Bit 1)
Relay trips whenever one of the HART ancillary
variables (Secondary, Tertiary, or Quaternary), are
operating outside the limits that can be effectively
measured.
PV Out of Limits (Bit 0)
Relay trips whenever the HART Primary Variable is
operating outside the limits that can be effectively
measured.
Delay & Fail Safe
By entering a value in the
Delay
box, you can specify
how long (in seconds) the alarm condition needs
to exist before the alarm trips.
Failsafe
alarms (box
checked) de-energize when in alarm condition;
Non-Failsafe
alarms energize when tripped.
