To enable/disable the digital low-pass filter with the relevant bit, set the cutoff frequency in the Unit
operation settings to a value other than
0
. If the cutoff frequency is set to
0
, the digital low-pass
filter will not be enabled even if the relevant bit is set to enable.
The relevant bit is Ch
£
Digital Low-pass Filter Disable. Refer to
£
Operation Command.
Attenuation Characteristics and Step Response Characteristics
(a) Attenuation characteristics
The attenuation characteristics of the digital low-pass filter for typical cutoff frequencies are
shown below.
Input signals are attenuated by -3 dB with the cutoff frequency. Note that the attenuation char-
acteristics shown in these graphs are based on theoretical values.
0
−
10
−
20
−
30
−
40
−
50
-60
−
70
-80
−
90
1
10
100
1 k
10 k
100 k
fc = 50 kHz
fc = 10 kHz
fc = 1k Hz
fc = 100 Hz
fc = 10 Hz
G
a
in
[
d
B]
Frequency [Hz]
(b) Step response characteristics
The step response characteristics of the digital low-pass filter with the cutoff frequency set to 1
kHz are shown below. The step response time of the digital low-pass filter is 366.4 µs if the
cutoff frequency is set to 1 kHz. The step response time is the time until the output of the digi-
tal filter reaches 90% from 0% when the step signal is input to the digital low-pass filter.
8 Functions
8 - 22
NX-series Analog I/O Units User’s Manual for High-speed Analog Input Units (W592)
