Filter Register (R37) IP/IE3112
The IP/IE3112 possesses two low-pass filter stages. The first stage consists of a sin³ filter. This is always active. The second consists of a 22nd order FIR filter. This can be deactivated. The filter settings always apply to all the channels, and are set in the first register for channel 1. The settings are not effective until after a power on reset (switch the Fieldbus Box off and on again).
|
Bit |
SF11 |
SF10 |
SF9 |
SF8 |
SF7 |
SF6 |
SF5 |
SF4 |
SF3 |
SF2 |
SF1 |
SF0 |
0 |
0 |
SKIP |
Fast |
|
Name |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
FAST
1 - active
0- inactive
When active there is a fast reaction to input steps (in spite of
the filter stage being active); in this case the filter is being
bypassed.
SKIP
0 - FIR filter active
1 - FIR filter is bypassed
Bits 2, 3
must be zero.
SF0-11
This is the filter constant itself. It specifies the 3dB limit frequency of the sin³ filter. The value ranges from 150 to 2,047. The 3 dB limit frequency and the 64.5 dB stop frequency Fstop are listed in the following table and are calculated as follows:
SKIP = 0
SF = 11981/ Flimit
SF = 43008/ Fstop
SKIP = 1
SF = 80486/ Flimit
Example: You want to set a limit frequency of 75 Hz
SF=11981/ Flimit = 11981/75 = 160dez »
0000_1010_0000bin + LowByte = 0000_1010_0000_0000 =
0x0A00
Default 0x3200
|
|
Register 37 |
Fstop [Hz] |
Flimit [Hz] |
Cycle time [ms] |
|---|---|---|---|---|
|
SKIP =0 |
0x0A00 |
270 |
75 |
50 |
|
0x1400 |
135 |
38 |
100 | |
|
0x1E00 |
90 |
25 |
150 | |
|
0x2800 |
68 |
19 |
200 | |
|
0x3200 |
54 |
15 |
250 | |
|
| ||||
|
SKIP = 0 |
0x0781 |
|
|
5 |
|
0x0F01 |
|
|
10 | |
|
0x1681 |
|
|
15 | |
|
0x1E01 |
|
|
20 | |
|
0x2581 |
|
|
25 | |
|
| ||||
|
SKIP = 1 |
0x0782 |
|
671 |
5 |
|
0x0F02 |
|
335 |
10 | |
|
0x1682 |
|
224 |
15 | |
|
0x1E02 |
|
168 |
20 | |
|
0x2582 |
|
134 |
15 |