Re: DCC Meters

Mark Gurries

On larger layout without a load, you will see the track voltage go up the further you get away from the DCC system or booster powering the track.

The is voltage ringing (spike) on the DCC waveform created by the layout wiring that confuses the meter into reading a higher voltage than what is actually there.

The use a of a ten scope is good in that one can visually ignore the leading edge voltage ringing (Spike) and focus on the flat portion of the DCC waveform for the reading.

The advantage of having a resistive or locomotive head lamp load is it consumes the voltage ringing/spike by absorbing it.  Your presented with a much cleaner reading.

To check for voltage drops in the wiring, you will need a large lamp load such as offered by an 12V automotive lamp.

On May 22, 2019, at 1:09 PM, Richard Gagnon via Groups.Io <richg_1998@...> wrote:

When I connected my Harbor Freight meters to the output of the Power Cab
Had a loco on the track running. They all showed close to 13.6 vac. My Tek scope verified. I did the math conversion.
I figured whatever reading I got would be a bench mark as the loco was running fine and the system was.new
Rich

On Tuesday, May 21, 2019, 1:41 PM, Rop Honnor <robbie.honnor@...> wrote:

The accuracy of an AC volts reading when monitoring a DCC potential depends largely upon the sampling rate of your meter.

As stated DCC waveform is square format bi-polar not sinusoidal which is what an AC volts meter uses as its algorithm, therefore the higher the sampling frequency the more chance there is of an accurate DCC reading.

My three (cheapish) meters show a scatter of around +/- 5 volts measuring DCC on the AC volts scale as compared to the reading I see on my PicoScope set up for DCC.

Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics: www.markgurries.com

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