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3.4 Set point deviation histo-
gram
The set point deviation histogram contains a
statistical analysis of any set point deviations
recorded. It provides information on to which
extent a set point deviation has occurred
during the valve service life and whether
faults may occur due to a restricted working
range or due to seat leakage.
Data are recorded in the background re-
gardless of the operating mode selected. Da-
ta logging does not need to be activated.
The positioner records the set point deviation
every second and assigns the data into pre-
defined classes. The distribution showing
how often the set point deviation remained
within a class is shown in a bar graph.
− The 'Average value e long' indicates the
average class assignment of the set point
deviation over the 'Observation period.'
− The 'Number of measurement values'
shows the total number of values were
recorded during the 'Observation peri-
od'.
− 'Observation period'
− 'Absolute value of max. set point devia-
tion' indicates the largest set point devia-
tion measured during the observation
period.
The measured data are saved every 24
hours in the positioner.
Short-term monitoring
In order to be able to recognize any short-
term changes in set point deviation, the posi-
EB 8389S EN
tioner records the set point deviation accord-
ing to the adjusted 'Scan rate short-term his-
togram' and analyses the last 100 measured
values.
− The 'Average value e short' contains the
average class assignment for the last
100 measured values.
The positioner saves the set point deviations
in a circular buffer, which holds 100 mea-
sured values at one time.
Note:
On changing scan rate in 'Scan rate
short-term histogram', all existing
measured values are deleted from the
circular buffer.
Defining parameters
1. Set 'Scan rate short-term histogram'.
2. Select classification for status messages.
Diagnosis > Statistical information > Set
point deviation histogram e > Short-term
1.
− Scan rate short-term histogram:
1 to 3600 s, [1 s]
Settings > Positioner > Error control >
Classification report > Extended > ...
2.
Limit working range
− Down: [
],
,
− Up: [
],
,
− Modification impossible (jammed):
[
],
,
,
Connection positioner-valve
− No optimum travel transmission (TEST)
[
],
,
,
− Perhaps loose/(TEST): [
Statistical information
1)
,
],
,
,
33
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