HBM PX401, Operating Manual

Page: 198 / 552

Internal calculation channels
198
A4354-2.2 HBM: public
PMX
13.2.2.8 Moving Average
Function A moving average for an assigned number of samplings.
The filter settling time is the number of samplings
multiplied by the computation cycle (default 1s/19200, see
section 1).
Inputs X: : the signal being averaged
Outputs Y: : the moving average of input X
Parameters The number of samplings (filter width)
Range 1...385
Default Number of samplings: p. 385
Exception handling If the input is marked as invalid (invalid bit), the filter is
deactivated and the output is blocked and marked as
invalid. Invalid input values are not fed into the filter.
If the input becomes invalid, the filter is reactivated and the
output immediately becomes valid again. A filter settling
time is required until the filter buffer is filled with sequential
samplings.
The moving average is an efficient option for eliminating
narrow band noise, for example from the power supply
(50 or 60 Hz).
Width = 19200 Hz/50 Hz = 384 eliminates 50­Hz noise
(and the harmonics at 100, 150, 200, 250, etc. Hz)
Width = 19200 Hz/60 Hz = 320 eliminates 60­Hz­noise
(and the harmonics at 120, 180, 240, 300... Hz) ...where
19200 is the sampling rate.
This function requires a lot of internal memory. Generally
it is not possible to create more than 6 or 7 blocks of
moving averages, or even fewer if other blocks have
already been created.
If there is not enough memory for a new function block, a
message is logged.