Справочник Пользователя для Mitsubishi Electronics FX2N-5A

7-26

Formula for filter cut-off frequency f

L

: f

L 

= F

1

/(sampling time 

× no. of active channels) [Hz] with

cut-off frequency factor F

1

=0.1, 0.05, 0.025 or 0.01.

There are two filter parameters that can be changed, the filter-level and the cut-off frequency.
This selection is done in bit0 to bit7. The selected filter values apply to all channels 1 through 4
in the same way. Selecting a non existing filter mode or selecting a filter mode without
specifying a cut-off frequency will lead to an error in BFM 29. In this case the previously valid
settings will be kept.

The filter settings for the module also have a direct influence on the sampling rate and
conversion speed of the module. The relation between selected filter level and sampling rate is
as follows:

* In these cases b4 to b7 must be set to a value between K1 to K4.

The value of BFM 25 is stored non-volatile in the internal EEPROM. There is a safety function
to protect the internal EEPROM from being destroyed by accidentally writing the same value
continuously to BFM 25.

filter off (K0)

1ms / ch

update every 2 ms

2nd level digital    filter (K1)*

3ms / ch

update every 6 ms

5th level digital filter (K2)*

4ms / ch

update every 8 ms

7th level digital    filter (K3)*

4.5ms / ch

update every 9 ms