Moving Average (MA) Filter
LabVIEW file (sub-VI):
SubVI_moving_average_filter.vi
What is it?
It is a recursive (or online, or real-time) moving average filter implemented as a sub-VI.
The filter output is calculated with
yf_k = (1 - a)*yf_km1 + a*y_k
where
a = 1/N
where
N = ts/ts + 1
Above:
y_k is filter input at time index k (“now”).
yf_k is filter output at time index k (“now”).
yf_km1 is filter output at time index k-1 (“km1 = k minus 1”, i.e. previous time index).
ts is the time step (sampling time).
tf [s] is the filter time constant, or filter time window (i.e. the time interval over which the filter inputs are averaged). The smallest value of tf is 0 implying the filter does not actually filter.
N is the filter length (number of samples averaged).
a is a filter parameter.
This MA filter is identical to a time constant filter if the filter time window (t_ma) is identical to the filter time constant, and the time steps of both filters are equal.
Inputs and outputs of this subVI
Inputs:
y_k
tf [s]
ts [s]
Outputs:
yf_k
N
a
How to include the filter in your block-diagram?
Save the subVI file to any folder.
Add the subVI to the block diagram of your VI via Functions Palette / Select a VI etc. Then connect its inputs and outputs to the proper signals (wires) in your block diagram.
Filter tuning
To increase the filtering (smoothing), increase tf.
With tf = 0 there is no filtering, i.e. the input signal just pass through the filter.
Updated 20 October 2024 by Finn Aakre Haugen