Bfm#6 To #9: Digital Filter Setting - Mitsubishi Electric FX3G User Manual

FX /FX /FX /FX /FX
3S 3G 3GC 3U
FX -4AD/FX -4AD (4-channel Analog Input)
3U 3UC
5.4.3

BFM#6 to #9: Digital filter setting

To use the digital filter for channel data (BFM#10 to #13 for channels 1 to 4), set the digital filter value in the
corresponding buffer memory (BFM#6 to #9 for channels 1 to 4).
If the digital filter function is used, the relation between the analog input value and the set digital filter value or
the digital output value (channel data) will be as follows:
• Digital filter value (BFM#6 to #9 for channels 1 to 4) > Fluctuation of analog signal (fluctuation
width: less than 10 times of sampling)
If the fluctuation of the analog signal (input value) is less than the set digital filter value, the analog input
value will be converted into a stabilized digital output value and stored in the corresponding buffer memory
(BFM#10 to #13 for channels 1 to 4).
• Digital filter value (BFM#6 to #9 for channels 1 to 4) < Fluctuation of analog signal
If the fluctuation of the analog signal (input value) is more than the set digital filter value, the digital output
value will follow the analog input value, and the digital output value equal to the analog input value will be
stored in the corresponding buffer memory (BFM#10 to #13 for channels 1 to 4).
The relation between the set value and the corresponding operation is shown in the following table:
Set value
Less than 0
0
1 to 1600
1601 or more
1. Application
If the measurement signal contains steep spike noise, use the digital filter instead of the averaging function.
The digital filter produces more stabilized data results.
2. Cautions regarding digital filter setting
• To use the digital filter function, be sure to set the averaging time of the corresponding channel to "1".
(Averaging time: BFM#2 to #5 for channels 1 to 4) If the averaging time is set to a value other than "1" and
the digital filter is set to a value other than "0", the digital filter setting error (b11 of BFM#29) will occur.
• If one of the channels uses the digital filter, the A/D conversion time will be set to 5 ms for all the channels.
• If the digital filter set value is not in the range from 0 to 1600, the digital filter setting error (b11 of BFM#29)
will occur.
B-28
PLC User's Manual - Analog Control Edition
3UC
→ For a detailed description of channel data update timing, refer to Subsection 5.4.4.
Analog input value
Digital output value
Converted into stabilized digital output value
(Fluctuation width is less than 10 times of sampling)
Disables the digital filter function. A setting error will occur (b11 of BFM#29 will be set to ON).
Disables the digital filter function.
Enables the digital filter function.
Disables the digital filter function. A setting error will occur (b11 of BFM#29 will be set to ON).
Numeric data type: Decimal (K)
The digital output value will
follow the analog input value.
Set digital filter value
Set digital filter value
Time
Operation
5 Buffer Memory (BFM)
5.4 Buffer Memory Details
Setting range: 0 to 1600
Initial value: K0