hgodling I have little experience with the analog meters, but from what I remember you had to make sure you had the polarity correct.
Nevermind.
-Kevin
Living the dream.
I am wondering if this is just an artifact of the anolog meter. I have little experience with the analog meters, but from what I remember you had to make sure you had the polarity correct. They can't just show negative voltage like the digital ones do. (This may have just been an issue with the one I used 20 years ago.) However, given Kevin's comment that the digital are easier to use, I think that was a common thing.
Let me be clear. The change in reading occurred whenever I reversed the probes. It showed a strong reading every time I put the red probe on the inside rail and a weak reading every time I put the black probe on the inside rail. That's not the result of a loose probe or a defective meter. Tom's response seems to be the one that makes the most sense. I will also use settings selector has suggested and see what I get.
maxman Meter bad or a loose probe connection?
Meter bad or a loose probe connection?
If either of those were the case, I would think it would show up no matter which way the probes were set.
make sure the probes have good contact. they can be affected by dirty rail
greg - Philadelphia & Reading / Reading
I agree, digital is the way to go. However, whatever the meter, set it to measure AC and in the 20 volt range. You want to see, with about 0.4 volt variance over passing seconds, about 13-14 volts showing.
If the rails are connected and being fed properly along their lengths, the voltage will be rather constant and robust, up near 13.5 - 14 volts. If you get drops, it could be a bad connection at a joiner. It could also be a damaged lead wire anywhere from the probe back to the connector.
John-NYBWI got out my analog Multi-Meter.
BigDaddy....if the probes are in the proper port, ppolarity should not create different readings.
Yes, when reading resistances. When reading voltages, however, you can get the inverse voltage with the probes reversed but it's the same voltage only with a negative sign; not an entirely different reading.
[Edit: My comment above was made in regard to a digital meter. An analog meter does behave differently when the probes are reversed.]
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
What did you have the meter selector set at? It might be possible to get different readings if you had it set to DC. AC Volts will give you some indication of available DCC voltage across the rails but it would be best if you could apply a bit of a load at the same time.
I use a RR Amp meter and clip an 1156 automotive lamp to the test leads which puts a load on the rails. Open circuit voltage may not pinpoint a weak connection feeding the rails.
Good Luck, Ed
A mulitmeter has 3 or 4 ports where you can connect the probes.
Randy could give a better explanation, but if the probes are in the proper port, ppolarity should not create different readings.
Henry
COB Potomac & Northern
Shenandoah Valley
Just checked my NCE system and read about the same voltage both ways.
And if you are touching the rails you are reading voltage, not current.
For starters, I'm no whiz when it comes to electronics. I know just enough to get by. I have a DCC layout. I had a section of track that I suspected might not be getting enough juice so I got out my analog Multi-Meter and began testing the section I suspected had a problem as well as the sections on either side of the rail joiners for that section. I seemed to be getting a strong current everywhere, then suddenly there seemed to be a significant drop. I went back to check the sections I had just tested and they too showed a weak current. Then I discovered something curious. The strength of the signal changed significantly when I switched the red and black prongs on the Multi-Meter. When I touched the red prong to the inside rail and the black to the one closest to the aisle, I got a very strong signal. When I reversed them, the signal dropped to about a quarter of what it had been. I never knew that it mattered which prong touched which track but apparently it does. I had always touched red to the inside track and black to the outside track because those are the colors of my bus wires. I switched them inadvertently during testing and saw a sharp drop off in the signal. Can somebody explain why it would matter?