LM-3S voltages

[ON28]

Hello all--

Tried to find this in the archive but asking the group. What are the minimum, nominal and max voltages for the LM-3S in HO? I run RP on a layout wired for NCE. How does this jibe with NMRA S9.1 'Electrical Standards for Digital Command Control', April 9, 2021? Also, does a voltmeter provide a true reading of DCC track voltage, or do I need a RRampMeter by DCC Specialties? Thanks!

NMRA
Table 2.3 – Power transmission and amplitude limit parameters (Page 5)
Voltage limits for track HO/S/O scales for power station
8.5 volts minimum
15 volts 'nominal'
22 volts maximum

[William Brillinger]

From the LM-3S instruction page:

https://ringengineering.com/RailPro/Documents/LM-3Instructions.pdf

WARNING: Maximum voltage is 18 Volts. Only
power your LM-3 module with a Ring Engineering
Inc. RailPro Power Supply designed for the LM-3 or
a DCC power supply that only has the signal that is
described in NMRA DCC standards S-9.1 and S-9.2

[ON28]

Thanks, Bill, I missed that!

[gregeusa]

So a RRAMPMETER will give you true DCC voltage, i.e. when rectified to dc, that is the result, i.e. true dcc voltage of 18 volts through a full wave bridge with a tiny bit of noise filtering will be 18 volts DC.

But most "ordinary" meters on AC setting will not give you true DCC voltage.

You can hook a full wave bridge to your tracks, and then put a 0.1 mfd disk cap across the = and + and then read with a DC voltmeter. That will also tell you what the voltage is.

NCE systems (the 5 and 10 amp powerpro) are USUALLY about 16v DCC from the factory... but trust no one!

Greg

[ON28]

So what is the measurement differencde in track voltage between a multimeter and a RRampmeter?

I tried adjusting the voltage on my NCE base station following a YouTube video. For whatever reason some insulation began to smoke so I shut it down. My LM-equipped locos usually show voltage of 13-13.2v when not moving.

[gregeusa]

There is no relationship between a non-true-rms AC voltmeter and a true RMS reading AC voltmeter.

(RMS is a measurement technique, cheap meters do not use RMS but an approximation, and there is NO guarantee of how close the approximation is to the RMS value)

Some meters are close, some are way off. A full wave bridge might cost you 50 cents and 10 cents for the capacitor. Then you can use your DC meter.

If you want to measure something, if your tool is suspect, the measurement means nothing, really.

Greg