DCC Impulses Column - 2
1: DCC Data – Voltage between the rails with 15 volt track
voltage setting.
1
system and the decoders. This is square-wave data, as shown
in figure 1.
If you measure from a common point like the case ground on
some DCC systems to each rail, you will see half of figure 1, for
example, the signal going from zero to + 7.5 volts.
2. My multi-meter accurately reads my
DCC track voltage
Your multi-meter will not give you accurate readings, due to
the fact that the DCC signal is neither sine-wave AC nor steady
DC, which are the two types of voltage that multi-meters are
designed to measure.
But what those AC
numbers actually are
means nothing. If you
set the DCC track volt-
age with an oscillo-
scope to 15 volts, your
multi-meter may read
anywhere from 9 to
22 volts.
For accurate DCC mea-
surements, I highly
recommend the
RR-AmpMeter shown
in figure 3.
You can build circuitry
to measure DCC.
My friend Marcus
Ammann, from
Australia, has a circuit
on his web site to build your own
is method
drops the DCC voltage by about 1.5 volts, so it is not a good
thing to leave connected all the time. However, it is an inex-
pensive way to build your own DCC current measuring system.
3. The larger your layout, the more
boosters you need
2: Inexpensive digital multi-meter.
2
“When measuring DCC track voltage with
a multi-meter, the actual number you get is
inaccurate, but you can rely on the differ-
ences in values obtained different places
on the layout.”
MRH-Mar 2014
