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Author Topic: track  (Read 757 times)
dlstrain

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« on: February 23, 2017, 03:58:06 PM »

why cant you get a reading with avolt meter between rails with dcc to check voltage on track
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Flare

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« Reply #1 on: February 23, 2017, 04:17:40 PM »

In case you don't know, DCC uses alternating current, not direct current.

You should set your meter to expect between 10 and 16 volts, won't matter which probe goes on which rail.
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Hunt
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MBB


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« Reply #2 on: February 23, 2017, 06:26:11 PM »

While not an accurate measurement a multimeter, even a cheap one,  set on AC volts can be used for comparing the relative voltage difference between two points on DCC powered track. This is usually good enough and useable.



The technical stuff
The commonly found multimeter is designed and calibrated to measure an AC sine waveform in the 50-60 Hertz range. DCC is not an AC sine waveform but an alternating DC (yes DC) waveform containing digital information and is a higher frequency.   DCC is bipolar pulse-width modulation (PWM) DC (direct current)  waveform.



Image borrowed from Mark Gurries DCC website

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dlstrain

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« Reply #3 on: February 26, 2017, 10:40:06 AM »

thank you I have a 2-6-0 loco echo valley express dcc set that i add to the 4x8 layout it is 12' feet long it ran ok before glue down of track it now will run on curves but don't want to run on straight a ways I have cleaned the track and wheels on the coal tender where it picks up its power and still doesn't want to run right it runs on dc better than on dcc I tightened all jointers in the track to any suggestions thanks
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Len

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« Reply #4 on: February 26, 2017, 12:52:40 PM »

Depending on the multimeter, they can read AC sine waves up to a frequency anywhere between 1kHz and 100kHz. Some analog VOM's can handle up to 2mHz. Which is why they read square wave voltage, such as a DCC signal low. Since a square wave, whether PWM or not, is composed of the odd harmonics of the primary frequency, anything above the frequency range of the VOM is ignored. Also, since most VOM's give a pseudo-RMS reading, it will be lower than the peak amplitude of the square wave signal.

Len
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« Reply #5 on: February 26, 2017, 02:21:01 PM »

thank you I have a 2-6-0 loco echo valley express dcc set that i add to the 4x8 layout it is 12' feet long it ran ok before glue down of track it now will run on curves but don't want to run on straight a ways I have cleaned the track and wheels on the coal tender where it picks up its power and still doesn't want to run right it runs on dc better than on dcc I tightened all jointers in the track to any suggestions thanks

If all else is as it should be --- add feeders to the track where the locomotive does not run right. Suggest adding feeders using a temporary method in case there are other issues to be found and corrected.
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