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Advanced Settings
confocalDT 24x1
3, 5, 7 or 9 readings are taken into account. This means that individual interference
pulses can be suppressed. However, smoothing of the measurement curves is not very
strong.
Example
: Median value from five readings
... 1 2 4 5 1 3 5
... 0 1 2 4 5 1 3
Sorted measurement values: 1 3 4 5 5
Sorted measurement values: 1 2 3 4 5
Median = 3
(n)
Median
= 4
(n+1)
Application tips
-
The measurement value curve is not
smoothed to a great extent, used to elimi-
nate spikes
-
Suppresses individual interference pulses
-
In short, strong signal peaks (spikes)
-
Also suitable for edge jumps (only minor
influence)
-
For rough, dusty or dirty environment, to
eliminate dirt or roughness
-
Further averaging can be used after the
median filter
Signal without averaging
Signal with averaging
Fig. 41 Median, N = 7
Measurement
Measurement
Position value
Position value
Fig. 42 Original profile
Fig. 43 Profile with Median, N = 9
6.3.4
Error Handling (Hold Last Value)
If no valid reading can be obtained, an error is issued. Should this be a problem for pro-
cessing, the last valid value can be hold for a certain period of time, and will be issued
repeatedly.
Between 1 and 1024 values can be hold.
If the number is 0, the last value is hold until a new, valid reading is obtained.
6.3.5
Spike Correction
This special form of filtering is used to remove very high spikes from a relatively constant
course of measurement values, though while retaining any smaller spikes. A median
would remove all the spikes.
The assessment of whether a measurement is a spike (outlier) is based on the mean of
a particular number of previous valid readings. The permissible deviation from the next
value is calculated using the tolerance range. If the new measured value deviates too
much, it will be corrected to the previous value. A maximum number of consecutive mea-
sured values to be corrected must also be stated.
Attention: In the event of several consecutive spikes (outliers), the previous corrected
value is used in the correction of the following measured value. Use this function only in
appropriate applications. Improper use can lead to a distortion of the measured value
sequence! Check the possible impact of a changed measured value sequence on the
measuring environment and subsequent controllers/systems.
