Velleman K8000, Manual, Page: 8 / 16

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If desired, a voltage divider or filter can be fitted tn each analogue input. The voltage
divider can be useful if a higher input voltage than normal is to be monitored. Nor-
mally only a maximum of 5V can be accepted by the input. The filter can be useful
for eliminating (mains) hum from the signal for example. Points A to D give
examples.
No attenuation and no filtering (input impedance= 100K). In place of RA a
jump wire needs to be fitted. RA is a resistor. Nothing should be fitted in
place of CA.
Ri = 100K
RA : J
RB : 100K (1-04-B)
CA : /
50Hz mains filter (low-pass filter). By use of the formula, different values for RA
and CA can be calculated as a function of the desired frequency. If a high
value for CA is arrived at, then an electrolytic capacitor can be used, but check
the polarity.
Freq. = 50Hz / -3dB
CA = 1
RA : 10K 6,28 x f x RA
RB : /
CA : 330nF
21. Information
C A
R B
R A
I N
K 8 0 0 0
A D 1 . . . A D 4
Information