Ammeter for my layout

Model Railroader General Discussion (Model Railroader)
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I have wanted an ammeter on the layout for a long time. I found a +100-0-100 microamp meter movement. I wound a shunt to multiply the +/- 100 microamp meter up to +/- 1 amp. Computing the shunt is straight forward. Meter current times meter resistance equals shunt current times shunt resistance. In this case shunt current was 1000 times meter current. Winding the shunt is equally straight forward. Find the resistance per 1000 foot of copper wire from a copper wire table. I used the copper wire table in the CRC Handbook of Chemistry and Physics, but you can find copper wire tables on line. In my case a shunt of 19.4 inches of AWG 26 wire did the trick. I checked by work by putting the shunted meter in series with my B&K multimeter, and everything matched up.

Here is an Athearn rubber bad RDC model drawing 0.4 amps.

HHere is the shop made meter movement case with two coats of paint. I gave it a couple of more coats of wipe on varnish before installing it.

And here is the ammeter installed next to my MDC powerpack.

2

Power supply of LION.
Is Regulated, can run 1 to 10 trains at once witout voltage drops.

Main power supply for house of LION. Utility transformer is just outside of the wall with that main cabinet.

Back-up 100KW generattor in powerhouse of LION. Is wired to the service switches in previous photo.

ROAR

3

I have only ever needed an amp meter for troubleshooting.

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The output of each power pack has been wired to a DPDT switch. With the switch up, power is routed to the tracks, with the switch down, power is routed to a pair of jacks I can press my Fluke leads into. Then the Fluke can be set to DC amps, and it will complete the circuit and check current draw.

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This switch also functions as a main on/off switch for each power pack output when the Fluke Digital Multimeter is not in the circuit.

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-Kevin

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4

Nicely done. I like the old fashion look of that meter!

I only use this setup at the test bench. I modified this MRC Tech ll with a volt meter, then modified a Radio Shack separate ammeter with a large microphone jack to plug into the again modified power pack.

It stays in that drawer, less than a foot from the terminals on the test track on the bench above. It’s usually hooked up even when the drawer is closed unless I’m going for a super cleaned up look . The power to it, like soldering irons and such, goes out with the lights. Dan

5

They were scrapping this ammeter at GE. I couldn’t let it go to the dumpster —

GE_Amp60 by Edmund, on Flickr

It is vintage [8-|]

GE_Amp by Edmund, on Flickr

I’ve seen this type used in railroad signal towers (although they could be volt meters) mounted above the lever machines.

Cheers, Ed

6

Lion, Good looking stuff. Completely outclasses me.