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Monitoring of DC analog measurements
Measuring
Converter
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The measured voltage is filtered by the low-pass analog filter before entering the analog
to digital converter (A/D). Users can set the sampling frequency of the A/D converter
between 5 Hz and 255 Hz to adapt to different application requirements as best as pos-
sible.
The digital information is filtered by the digital low-pass filter with the (sinx/x)
sponse. The filter notch frequency automatically follows the selected sampling frequen-
cy. The relation between the frequency corresponding to the suppression of -3 dB and
the filter notch frequency corresponds to the equation:
,
⋅
f
0 262
f
=
3dB
notch
–
Using optocouplers and DC/DC conversion elements that are used separately for each
measuring channel, the input circuitry of each measuring channel is galvanically sepa-
rated from:
•
The internal measuring circuits
•
The control microprocessor on the board
A microprocessor collects the digitized information from each measuring channel. The
microprocessor serves as a communication interface to the main processing module
(MPM).
U
I
R
DC
Udc
DC
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REx 5xx Terminal
A
D
99000533.vsd
3
re-
(Equation 78)
363
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