8-5
Digital Filtering
8-5-1
Function Applications and Overview
This function uses the digital filter to remove noise components that are contained in analog input sig-
nals to suppress the fluctuations of analog input values.
A digital filter can remove electrical noise that is contained in analog input signals to provide stable
measurements.
8-5-2
Details on the Function
You can freely combine the following three digital filters for the High-speed Analog Input Units.
• Digital low-pass filter
• Moving average filter 1
• Moving average filter 2
Digital
low-pass filter
Moving
average filter
1
Moving
average filter
2
Enable
Enable
Enable
Input
Disable
Disable
Disable
Analog
input value
The digital low-pass filter and moving average filters are disabled by default. When the digital low-pass
filter and moving average filters are used, you can set the Unit operation settings or the relevant bit in
the Ch
£
Operation Command of I/O data to enable the digital low-pass filter and moving average fil-
ters.
For details on digital filter functions and the procedure to enable/disable filters, refer to the following
function descriptions for each digital filter.
The digital low-pass filter and moving average filters process data according to the Digital Filter Proc-
essing Period. Refer to
Digital Filter Processing Period
on page 8 - 19 for details on the Digital Filter
Processing Period.
After digital filtering, the analog input values are stored in separate buffers for each digital filter. In the
following cases, the past analog input values that are stored in buffers are cleared and the analog in-
put values at the recovery are stored.
• When the power supply is turned ON.
• When the NX Unit is restarted.
• When the system recovers from input disconnection detection and returns to normal operation.
If the digital filter is disabled with the relevant bit in the Ch
£
Operation Command, the past analog
input values that are stored in the buffer for the disabled digital filter are cleared. If it is enabled, the
analog input values are stored.
The High-speed Analog Input Units have a library of the Sysmac Library prepared to identify the noise
frequency band and confirm the noise removal effect. Refer to
A-4 Digital Filter Design with the Library
on page A - 21 for examples of digital filter design that utilizes the library.
8 Functions
8 - 18
NX-series Analog I/O Units User’s Manual for High-speed Analog Input Units (W592)
