Digital Filter Processing Period
The following describes the Digital Filter Processing Period, which is the data processing period for
the digital low-pass filter and moving average filters.
Application
The Digital Filter Processing Period is used to calculate the set value of the digital low-pass filter
cutoff frequency, the set value of the moving average count for a moving average filter, and the de-
lay time.
Determining the Processing Period
The Digital Filter Processing Period is the period during which the High-speed Analog Input Units
execute the processing of the digital low-pass filter and moving average filters in the sampling peri-
od. This period is automatically determined for each channel with the following formula. The period
is calculated as a value between 5 and 9.999 µs.
Ch
£
Digital Filter Processing Period
[µs]
=
Ch
£
Sampling Period [µs] ÷ Ch
£
Number of Digi-
tal Filter Processing Operations [times]
The resulting Digital Filter Processing Period is truncated to three decimal places.
The meanings of calculation elements are as follows.
Element
Description
Ch
£
Sampling
Period
This indicates the sampling period of analog input data during the task period in the rele-
vant channel.
Refer to
8-4 Number of Samplings Setting
on page 8 - 8 for the calculation formula for
the sampling period.
Ch
£
Number of
Digital Filter
Processing Op-
erations
This indicates the number of processing operations during the sampling period in the rel-
evant channel. It can be calculated with the following formula.
•
Ch
£
Number of Digital Filter Processing Operations [times] = Ch
£
Sampling Period
[µs] ÷ 5 µs
The Ch
£
Number of Digital Filter Processing Operations is calculated as an integer. The
decimal portion of the result is truncated.
Digital Filter
Processing
Period
Digital Filter
Processing
Period
1
2
N
1
2
N
1
Sampling period
Sampling period
N [times]: Number of digital filter processing operations [times]
8 Functions
8 - 19
NX-series Analog I/O Units User’s Manual for High-speed Analog Input Units (W592)
8-5 Digital Filtering
8
8-5-2
Details on the Function
