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Logical Output Combinations
Any suitable output may be assigned as a logical OR
or logical AND output of the alarm and profile event
conditions, and can be configured for reverse or direct
action. If OR is chosen, any of the selected alarms or
profile events that are active will cause the output to
turn on for direct acting outputs, or inactive for reverse
acting outputs (NOR). If AND is chosen, all of the se-
lected alarms or profile events must be active to cause
the output to turn on for direct acting outputs, or inac-
tive for reverse acting outputs.
The following table explains the concept of logical OR
& AND outputs.
Also refer to: Alarm Operation; Alarm Types; Output
Configuration and Profile Events.
Examples of Logical Outputs
Logical OR: Alarm 1 OR Alarm 2
Direct Acting
Reverse-Acting
ALARM 1
OFF
ALARM 2
OFF
OUTPUT
OFF
ALARM 1
OFF
ALARM 2
OFF
OUTPUT
ON
ON
OFF
ON
ON
OFF
OFF
OFF
ON
ON
OFF
ON
OFF
ON
ON
ON
ON
ON
OFF
Logical AND: Event 3 AND Alarm 2
Direct Acting
Reverse-Acting
EVENT
3
OFF
ALARM 2
OFF
OUTPUT
OFF
EVENT 3
OFF
ALARM 2
OFF
OUTPUT
ON
ON
OFF
OFF
ON
OFF
ON
OFF
ON
OFF
OFF
ON
ON
ON
ON
ON
ON
ON
OFF
Loop Alarm
A loop alarm detects faults in the control feedback in the
selected loop, by continuously monitoring the process
variable response to the control outputs. If any alarm
is setup as a loop alarm, it repeatedly checks if the
control output is at saturation. If saturation is reached
(0% or 100% power for single control type, -100% or
+100% for dual control type), an internal timer is start-
ed. Thereafter, if the output has not caused the process
variable to be corrected by a predetermined amount ‘V’
after time ‘T’ has elapsed, the alarm becomes active.
The alarm repeatedly checks the process variable and
the control output. If the process starts to change in
the correct direction or the control output is no longer
at the limit, the alarm deactivates.
For PI or PID control, the loop alarm time ‘T’ can be au-
tomatic (twice the Integral Time value) or set to a user
defined value up to 99m 59s. Correct operation with
the automatic loop alarm time depends upon reason-
ably accurate PID tuning. The user defined value is al-
ways used for P, PD or On-Off control. The timer starts
as soon as an output turns on with on-off control.
The value of ‘V’ is dependent upon the input type. For
Temperature inputs, V = 2°C or 3°F. For Linear inputs,
V = 10 x LSD
The loop alarm is automatically disabled in manual
control mode and during execution of a pre-tune. Upon
exit from manual mode or after completion of the pre-
tune routine, the loop alarm is automatically re-enabled.
Also refer to: Alarm Types; Control Type; Manual Loop
Alarm Time; Linear Input; LSD; Manual Mode; On-Off
Control; PD; PI; PID; Pre-Tune; Process Variable and
Tuning.
LSD
The Least Significant Digit (LSD) is the smallest incre-
mental value that can be shown at the defined display
resolution.
Also refer to: Display Resolution.
mADC
This stands for milliamp DC. It is used in reference to
the linear DC milliamp input ranges and the linear DC
milliamp outputs. Typically, these will be 0 to 20mA or
4 to 20mA.
Also refer to: Input Range; Linear Input; Linear Output;
mVDC; Process Variable and VDC
Main Menu
The top-level menu that allows access to operation
mode as well as all other menus. These are: configura-
tion mode, profiler setup and recorder menus, the set-
up wizard, supervisor mode and the tuning and USB
menus. Most menus require an unlock code to gain
access.
Refer to the Main Menu information in the Configura-
tion & Use section.
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