A&O The DCC Ammeter/Scale DCC Load Meter


Many model railroaders attached an ammeter to their DC layout to monitor the performance of their locomotives. But with today’s DCC the simple analog meter can’t accurately measure the square wave AC waveform. One popular electronic meter is Tony’s Train Exchange RRampMeter. It is a fine product that digitally displays DCC voltage and current draw.

Unfortunately, in the late 1960’s we didn’t have LED displays. To better fit the era we now have

[size=150]A&O The DCC Ammeter[/size]

This little board uses a current transformer to measure the average DCC current load on a 10A NCE booster. But what does it drive if not LEDs? Why one of these, of course.

This meter is probably from a F7, F9, GP7, GP9, SD7 or SD9. Or for that matter, it could be from one of the later E units as represented by the NYC E8 in Elkhart IN. The F3 used a different color-coded meter. Full scale deflection requires 20 mA. When deployed the board will be calibrated to indicate 100 times the actual current (scale current.)

A round load meter from an EMD second-generation diesel is already installed and working at the 16th Street yard complex. A sufficient number of tested meters have been procured for the rest of the layout.

Sure, it is a little geeky but I like it anyway. The meters are a varied collection of load meters from EMD, GE, and Alco, including a “smiley face” meter from GW GP7 2233 as she was cut up in Loveland. One or two 100 MPH PRR GG1 speedometers may also appear in the mix.


Hi Bob,
just joined this group because of your post on the DCC ammeter. I have a similar requirement in the UK and your solution is perfect. Could you post a component list and circuit diagram please? Many thanks. John


John -

I’m glad to share what I built and learned. The design isn’t perfectly accurate, and normally shows up to a 1/2 A offset, but it still is fun, and that is the intent on the A&O. I’m happy to share what I built and learned. I’ll dig into my archives. Check your private email from this web site, because the design information would not be very interesting to most of the forum members. You are the first to indicate any interest.

All the best!