ABB 800xA Operation page 111

Section 8 Control Loop Asset Monitor (CLAM)
Harris index is therefore a number between 0 and 1: the higher the number, the
higher the controller performance to the theoretical maximum.
Setpoint Crossing Index
This index identifies the amount of control error zero crossings related to the total
number of samples in a data batch. The aim is to quantify the closeness of the
control error to zero. A low value means long periods where the control error is
either above or below zero. White noise has a theoretical value of 50%. A value
>10% is considered to be good. This index is not used for diagnosis of level loops.
Oscillation Index
The main purpose of the Oscillation Index is to detect oscillatory control error
behavior. Detection of oscillations in control loops is a crucial indicator in control
loop monitoring. The oscillation detection based on the control error signal is the
main pre-requisite for several diagnosis indices, which are evaluated following the
detection.
Controller Output Saturation
This control loop asset monitor diagnostics indicates if the controller output has
reached saturation. This index quantifies the number of times the controller output is
significantly long (below 3% or above 97%) of the controller output range.
Manual Mode
Based on the controller output, this index quantifies the amount of time the control
loop is in manual mode. This index checks the variability of the controller output.
Control loop performance will not be optimal since the loop is not in automatic
mode.
Cascade Tracking Index
This simple index counts all samples that deviate more than 3% of the loop range
from the desired set point value. The purpose is to quantify set point tracking
performance. This index is defined as the number of samples outside the
specification divided by the total number of samples. A high index value means that
3BUA000150-600
Loop Performance Diagnostics
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