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Operation
optoNCDT 1700
6.6.3 Recursive Average
Formula
MV + (N-1) x
(n)
M
rek (n-1)
N
M (n) =
rek
MV = Measuring value
N = Averaging number
n = Measurement value index
M
rek
= Average value respectively output value
Mode:
Each new measurement value MV(n) is added, as a weighted value, to the sum of the previous measurement
values M
rek
(n-1).
Standard values for N: The values N = 1, 4, 32, 128 are permanently stored in the sensor. For other
permissible values for N, see Chap. 8.5.4 „Averaging“.
Characteristics:
The recursive average permits a high degree of smoothing of the measurement values. However, it requires
extremely long transient recovery times for steps in measurement values. The recursive average shows low-
pass behavior.
6.6.4 Median
The median is generated from a pre-selected number of measurement values. To do so, the incoming
measurement values (3, 5, 7 or 9 measurement values) are resorted again after every measurement. The
average value is then given as the median. In generating the median in the controller, 3, 5, 7 or 9
measurement values are taken into account, i.e. there is never a median of 1.
This permits individual interference pulses to be repressed, but the measurement value curve is not
smoothed to any great extent.
Example: Average from five measurement values
... 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)
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