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Shdwdrgn, I have one of those also, and I think I may wire it in permanently just for looks. I don't use it so it's just in the junk box for now. Might as well put it to use. The Mustool does have an I2c Arduino bus decode function also, but its the display that's makes it the easiest to read meter. I would not buy the Mustool for its Oscilloscope function only.
 

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Yeah I hope nobody would by a multimeter for its oscilloscope functions, they would be sadly disappointed! :)
 

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Well, if you never used a real 'scope you would never know the difference! Every once and a while I would wander down to the lab at work and use the 'scopes their, kinda spoils you.
 

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Dcc is a square wave form so it’s set up like a can bus in a car. Think of it as a series of 1s and 0s 1 is on 0 is off. Ac is a sine wave that goes from positive to negative in an alternating current. It’s easier to send a digital signal through an ac circuit than it is for dc. So the decoder will pick up the digital signal through the ac sine wave. If dc was used in dcc instead of ac it would create an excessive amount of “background noise” for the decoders to pick up on and possibly confuse the decoder. I have that issue with mine every once in a while if I have a metal wheel car derail and get a short in the track it will cause a random locomotive to go full blast in one of the two directions until it is stopped, loses connection, or derails. My digitrax db150 puts out around 15vac my bachmann ex command puts out around 13vac. I hope this isn’t confusing you but may help you understand your system a little better
 

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not sure why DC would be more noisy than AC. possibly because some other method (e.g. AC carrier) would be need instead of simply modulating polarity.

the decoder needs to rectify the track voltage, reducing it by 2 diode drops (~1.4V) and the there's yet another smaller drop through the transistors of an h-bridge. so motor voltage is ~2V less than track voltage.
 
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