Track laying,..electrical question


beiland

Well-Known Member
Track laying,..electrical question

I'm a little confused with this observation of mine. I've been laying lots of code 100 atlas track lately,...and attaching the multiple feeders wires to the bus wires. The area I have in question is down one side of the layout under my steel mill and freight yard tracks. Its all going to be a single power district with a single bus wire feeding it.

That single bus wire stretches the length of side of the layout and has open ends (no connections at this time on either end).

For testing purposes I hooked up a standard DC transformer to one end of that bus wire,...then I can run a couple of DC engines on these tracks,..no problem.

When I test the tracks for continuity with my multimeter, I first touch the tips of the probes together to be sure I am measuring zero ohms resistance. I can then measure along any single rail and/or across rail joints to see that I have very good (zero ohms) resistance.

What I am confused about is when I touch those probes across to two opposite rails of a piece of track, my reading is almost zero resistance,...almost the same as when I have the 2 probes in direct contact with one another......Correct me if I'm wrong, but this measurement should be VERY HIGH resistance,...infinity ?

Wouldn't this indicate some sort of electrical short would occur if I should hook up my power supply to this bus?
 
Test Set-up this morning


So here is the test set-up I used this morning. I used two different multimeters trying to see if that made any difference?



image-20210928104811-1.jpeg



image-20210928104851-2.jpeg



I also selected 4 different locos for the test,...all of which I am pretty sure are DC only. The one questionable one might be the Atlas switcher.

I specifically left the DC power pack unpluged and NOT attached to the bus wire at either end of this block of tracks.


This time I measured infinity ohms across the two rails of any track WHEN any of the locos were NOT on the track. When any of the locos were on any of the tracks I got the zero ohms measurement. I surmise that the wiring in the locos themselves were giving me this 'shorting problem' that I thought I was experiencing when I first posted this thread.

Furthermore I hope I can believe as a result of this test that all of my feeder wires are correctly wired for this portion of the layout,...since I did not experience any zero ohm measurements??
 
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You should get the same readings on the locomotives if you measure the resistance across the opposing pickups. Your reasoning is correct. The resistance across the motor windings is virtually zero. With no locomotives on the tracks, there is no connection between the two rails (assuming you do not have the feeder wires from the power pack connected to the track rails) so resistance is infinite.
 



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