Section 19 - Appendix B–Filter Board Options PWA 79562-01 and PWA 105521-01
75
19.13 Example Low-Pass Filter Configuration
This example shows how to configure channel B with a low-pass filter that has a corner
frequency, f
LP
, of 7500 CPM (125 Hz). (The resulting -3dB point is at 1.06 x f
LP
or 7950 CPM
(132.5 Hz). The Low-Pass Filter is before the Integrator/Gain Stage.
NOTE: Since this corner frequency is listed in Section 19.10, you would normally
configure the filter from the table. This example is meant to illustrate the calculation
procedure used when the desired corner frequency is not given in the table.
Follow the steps outlined in the General Procedure, Section 19.4 for the following two
steps.
1. Set the type of filter as a Low-Pass filter as shown in the table of Section 19.5. The
table in Section 19.5 shows that for a Low-Pass filter for channel B
On the Filter Board
Install: W21 and W58
Remove: W20 and W59
2. Set the Low-Pass Filter before the Integrator/Gain Stage as shown in the table for
channel B in Section 19.6.
On the Main Board
Install: W3A,W3C, and W5B
Remove: W3B
On the Filter Board
Install: W61
Remove: W41,W60,W85 and W86
Follow the steps outlined in General Procedure, Section 19.4, to set the
low-pass corner frequency,
f
LP
.
3. Set the anti-aliasing filter. Select the anti-aliasing corner frequency f
AA
to band-
limit the input signal.
625=125×5=f
AA
4. Select a value, K. In this case,
f
AA
is between 120 Hz and 4.81 kHz, so the value of K
is 19.188.
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