Hach-Lange ORBISPHERE K1100_M1100 Operator Manual - Manual (Page 55)

53
Measurement Menu
Measurement alarms configuration
Set the thresholds for the low/high concentration levels, according to the application. Each alarm type
can be individually enabled or disabled without losing its settings.
These events can activate the relays and can be displayed.
•
Low-low : 2nd stage for too low concentration
• Low : 1st stage for too low concentration
• High : 1st stage for too high concentration
• High-high : 2nd stage for too high concentration
• Hysteresis : A percentage of the above concentration values. The hysteresis is used to prevent relay
“flickering” when the measurement is just at the alarm levels. Set this to a minimum, but enough to
eliminate flickering.
As an example, if the High Alarm is set to 40 units and the Hysteresis is set to 10%, then the High
Alarm is activated once the measurement reaches 40 units, but only deactivated once the
measurement drops below 36 units. With the Low Alarm the opposite is true, in that if the Low Alarm
is set to 20 units and the Hysteresis set to 10%, then the Low Alarm is activated when the
measurement drops below 20 units, and deactivated when the measurement rises above 22 units.
• Delay : The delay in seconds, before alarms go on whenever concentration values go above ”High
alarms” or below “Low alarms”. Set this to a minimum value, but enough to avoid alarms for
non-representative peaks beyond the set level.
Figure 37 Alarms system diagram
Measurement filter configuration
The filters are aimed at “flattening” the measurement curve in situations where the process shows
atypical peak values that could otherwise hamper the interpretation of measurement readings. The filter
is applied on the last set of measurements each time a measurement is taken.
•
Mean : Mathematical average of the last set (depth) of measurement values.
• Median filter : Allows for eliminating atypical peak measurement values, and average the remaining
ones. The calculation sorts the last measurements set (depth) by values, then delete the highest and
lowest values, and averages the remaining values (central depth).
Example for depth 7, central depth 5:
Sorted values, both ends eliminated, the average of the center five is then 3.88.
0.7 - 1.1 - 4.0 - 4.3 - 4.4 - 5.6 - 7.0
Example for depth 5, central depth 3:
Sorted values, both ends eliminated, the average of the center three is then 4.23.
1.1 - 4.0 - 4.3 - 4.4 - 5.6
Example for depth 8, central depth 4:
Sorted values, both ends eliminated, the average of the center four is then 4.43.
0.7 - 1.1 - 4.0 - 4.3 - 4.4 - 5.0 - 5.6 - 7.0