33 Analog weigh module XN-322-2DMS-WM
33.5 Filter settings
259 XN300 slice modules 02/24 MN050002EN Eaton.com
33.5 Filter settings
The reading's accuracy and stability will depend on how the filter is
configured. If the filter has a high cutoff frequency, so that the goal is to have
a short refresh time for the reading, the resolution will be lower. If the filter
has a low cutoff frequency, resulting in a long refresh time, the measured
value will be more accurate and the transmission frequency (bus load) will be
lower.
The refresh frequency can be calculated by using the formula below. The
cutoff frequency must be configured in CAN object 5060 Section “
0x5060”, page 262.
For a cutoff frequency of 3 dB, this yields:
For: sinc x = sinc 4, AIxFilterDepth = 5
f
ADC
=
f
CLK
f
ADC
: ADC data rate
f
CLK
: 4.92 MHz
AIxFilterDepth :ADC filter depth
(sin c x
∙ 1024 ∙ AIxFilterDepth
t
SETTLE
=
2
=
2 ∙ (sin c x ∙ 1024 ∙ AIxFilterDepth) t
SETTLE
: Conversion time
f
ADC
: ADC data rate
f
CLK
: 4.92 MHz
AIxFilterDepth : ADC filter depth
f
ADC
f
CLK
f
3dB
=0.24∙ f
ADC
=
0.24
∙ f
CLK
f
ADC
: ADC data rate
f
CLK
: 4.92 MHz
AIxFilterDepth: ADC filter depth
(sin c x ∙ 1024 ∙ AIxFilterDepth)
t
SETTLE
=
2
=
2 ∙ (4 ∙ 1024 ∙ 5)
= 0.0083s
f
ADC
4920000 Hz
Conversion time = 8.3 ms
f
3dB
=0.24∙ f
ADC
=
0.24 ∙ 4920000 Hz
4 ∙ 1024 ∙ 5
3dB limit frequency = 57.66 Hz
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