DAD 141.1 Technical Manual, Rev. 2.5 – April 2015
Page 36 of 54
10.4. Filter Setting Commands
– FM, FL, UR
A digital filter can be set which will eliminate most of the unwanted disturbances. The commands
FM
and
FL
are used to define the digital filter settings, the command
UR
is used to define an averaging of up to 128
measurement values. Please note that these filters are positioned immediately after the A/D Converter and
therefore affect all aspects of the weighing operation.
10.4.1. FM Filter Mode
[
Index 0x2110
]
This command defines the filter mode. Choose the filter mode for your application.
P
ermitted values are “0” for IIR filter and “1” for FIR filter.
Master (PC / SPS) sends
Slave (WCN-H 122.1) responds
Meaning
FM
M+00000
Request: FM = 0 (IIR filter)
FM 0
OK
Setup: FM = 0 (IIR filter)
WP
OK
Setup saved
The digital IIR filter operates as 2
nd
order low pass filter and Gaussian characteristics. The attenuation is
40dB/decade (12 dB/octave).
The digital FIR filter works as a low-pass filter with quick response; damping see table mode 1.
Factory default:
FM = 0 (IIR filter)
10.4.2. FL Filter Settings
[
Index 0x2106
]
This command defines the 3dB filter cut-off frequency.
Master (PC / SPS) sends
Slave (WCN-H 122.1) responds
Meaning
FL
F+00003
Request: FL = 3 (4 Hz)
FL 7
OK
Setup: FL = 7 (0.5 Hz)
WP
OK
Setup saved
The permitted settings are from 0 and 8 (see below table).
Factory default
: FL = 3.
Mode 0 (IIR filter) Settings / Characteristic
FL
Settling time to 0.1%
(ms)
3dB Cut-off frequency
(Hz)
Damping
@300Hz
(dB)
Output-rate
*
(samples/s)
0
no filtering
**
600
1
55
18
57
600
2
122
8
78
600
3
242
4
96
600
4
322
3
104
600
5
482
2
114
600
6
963
1
132
600
7
1923
0.5
149
600
8
3847
0.25
164
600
*
Output-rate = 600/2
UR
samples/s
**
Antialiasing filter 17 Hz @ 60 dB/dec