Model Railroading > Yea or Nay, Volt / Ammeter on a modern DCC layout

or not needed TIA

Ed Stewart
Jacksonville, FL

I still use the volt meter and ammeter on my DCC layout, primarily because I have a few older locomotives not yet converted to DCC.  I have the layout wired so that I can flip appropriate DPDT toggles and convert various electrical blocks to DC, allowing me to run the old DC locomotives.  Then the meters come in handy.

UP9116

A pocket (or smaller) DCC track tester is the first thing to have, if something doesn't move you first want to find out if power is getting to that track segment.
(This is how I am finding failed track wire and joint soldering 20+ years after construction.)
I think I am about ready to put in an AC Ammeter so I can check that I don't exceed the 5 amp limit of my command station. 
I have one on my test and programming track along with DC volt and ammeters to check out DC motors before installing decoders and the current draw after the locomotive is DCC.
It is probably safe to ignore AC volts because they are on and running at 16-17 volts or the breaker is tripped and there is zero.

Put an ammeter on my two DD40 brass engines I have that are both Alco made ones. They drew a combined 4 amps total and did run but were as loud as a full scale I think. They look ok sitting in my display cabnet dont want to repower them am going to buy the Athearn DD40AX ones instead.

Keep in mind that the DCC electrical protocol that comes out of the command station / booster and goes to the rails is a different kind of electrical signal. It has components of DC and AC together. The DCC data packets are a "high speed data transmission" signal (not truly AC). The data transmissions are riding on top of a DC voltage level. Therefore a traditional voltmeter will not provide a true answer of the actual voltage level. The voltmeter will "alias" due the precensce of the DCC digital data packet. 


Bob Perkins
 

Bob P is correct.  The volt meter readings on a typical volt meter are not that relavent.  A meter is looking for sine wave voltage,
but that isnt what the DCC systems put out.  What a volt meter will tell you is if the readings are the same throughout the layout 
which is important.  What the actual reading is, is not that important unless the reading is really, really low, then the packets will have
a hard time reaching their destination, especially if there is other activity on the track (multiple DCC operating locomotives).

...and different meters will read that differently, not to mention a big difference between an analog meter and that said for digital meters. I haven't tried to understand DCC but agree it's going to look different. Thanks for the pointers.

We recently converted a large club layout to DCC with a new bus but kept the legacy wiring for turnouts etc.  The VOM is my go to device to detect dead frogs, dead tracks, and two districts out of phase with each other. I'm sure once the conversion bugs are worked out I'll use it less.
Mike Stewart
Oakley,ca

WrongWayMurphy Wrote:
-------------------------------------------------------
> Bob P is correct.  The volt meter readings on a
> typical volt meter are not that relavent.  A
> meter is looking for sine wave voltage,
> but that isnt what the DCC systems put out.  What
> a volt meter will tell you is if the readings are
> the same throughout the layout 
> which is important.  What the actual reading is,
> is not that important unless the reading is
> really, really low, then the packets will have
> a hard time reaching their destination, especially
> if there is other activity on the track (multiple
> DCC operating locomotives).


This is what I use....I have a portable one I can carry around and clip to the track anywhere - and a fixed one between my NCE DCC system and the track.
https://dccspecialties.com/products/pdf/RRampMeter-Application-Notes.pdf

Bob

I have seen the RRampmeter in use and it is quite handy. The digital readout allows you to look a ways across the layout to see what is going on.