User Manual

Pico Technology ADC-20/ADC-24 Terminal Board User Guide
DO117-5 5
The following four noise problems are often associated with potential divider circuits:
1. Noise from source voltage. Try fitting a capacitor as described below.
2. RF interference is picked up at high-impedance points. Smaller values for
RA and RB may help.
3. Noise on the earth connections.
4. The signal 0 V line is connected to mains earth. Try to avoid this situation.
In the event of 1 or 2 (above) occurring, and you want to try a capacitor, ensure that
you have fitted resistor R
A
and cut the corresponding track beneath the resistor. Fit
the capacitor in place of or in parallel with R
B
, as necessary. Use the following
equation for C, the value of the capacitor:
Rf
C
×
=
π 2
1
where R is R
A
or the smaller of R
A
and R
B
, and f is the highest signal frequency in
hertz.