MICRO-EPSILON CSP2008, Instruction Manual

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Page 42
Operation
CSP2008
5.3.10.4 Averaging Program
The averaging types
- moving average,
- recursive average and
- median are implemented in the controller.
Using the averaging,
- the resolution is improved,
- the hiding of individual interference points is enabled or
- the measurement result is "smoothed".
The linearity is not influenced by averaging.
Moving average
Using the selectable number N of sequential measured values (window width), the arith-
metic mean M
gl
is calculated according to the following formula and output:
MV (k)
k=1
N
N
M =
gl
MV = Measured value,
N
= Averaging number,
k = Continuous index (n the window)
M
gl
= Average value or output value
Method:
Each new measured value is added, the first (oldest) measured value is removed from
the averaging (from the window) again. In this way, short response times for measured
value jumps are achieved.
Example: N = 4
... 0, 1, 2, 2, 1, 3
2, 2, 1, 3
4
= M (n)
gl
... 1, 2, 2, 1, 3, 4
2, 1, 3, 4
4
= M (n+1)
gl
Measured values
Output value
Standard values for N: The values N = 1, 2, 4, 8, ... 1024 are permanently stored in the
controller.
Recursive Average
Formula:
MV + (N-1) x
(n)
M
rec (n-1)
N
M (n) =
rec
MV = Measured value,
N
= Averaging number,
n = Measured value index
M
rec
= Average value or output value
Method:
The weighted value of each new measured value MV(n) is added to the sum of the previ-
ous average values M
rec
(n-1).
Standard values for N: The values N = 1 ... 32768 are possible in the controller.
Special features:
The recursive averaging enables very strong smoothing of the measured values, how-
ever it needs very long response times for measured value jumps. The recursive average
value shows low-pass behavior.
Median
The median is formed from a preselected number of measured values. The incom-
ing measured values (3, 5, 7 or 9 measured values) are also sorted again after each
measurement. Afterwards, the average value is output as the median. 3, 5, 7 or 9 meas-
ured values are taken into account in the controller for the calculation of the median, i.e.
there is no median 1. Individual interference pulses can thus be suppressed. However,
the smoothing of the measured value curves is not very strong.