Actually it was Tom / H0



It's all about definitions and what is the common terminology. Quoting from Wikipedia, as Dale did on his blog, you get this:

"Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC)"

So how do you define "periodically"? To me it means "at regular intervals of time", not like MM/MFX/DCC.

And how would you describe "changes its magnitude continuously" ??

Wikipedia also says:

"The usual waveform of alternating current in most electric power circuits is a sine wave, whose positive half-period corresponds with positive direction of the current and vice versa. In certain applications different waveforms are used, such as triangular waves or square waves. These currents typically alternate at higher frequencies than those used in power transmission."

But a square wave doesn't "change its magnitude continuously" as the sine wave and the triangular wave, so IMHO, even Wikipedia contradicts itself.

I fully agree that in a digital system the current is alternating, it can be between 0 and a positive value, or between a positive value and a negative value, and a lot of other possibilities, if it's not strictly a binary digital signal.

A morse signal sent by a battery driven flashlight is also a digital signal, the current to the light bulb alternates between 0 and "something", but I don't think anybody would call it AC, even if the message "eeeeeeeeeeeeeeeeeeeeee" was sent, in which the alternation of the current is also periodically / at regular intervals of time

I don't mind people calling a digital signal "a form of alternating current", "digitial AC", "square wave AC" or whatever; I'm only opposing the use of only "AC" as a term to describe the digital signals we're using, since all over the world, "AC" is used for something else, IMHO

Per.

P.S: Next interesting topic could be about WHY the digital signals for MM/MFX/DCC was designed using both
positive and negative currents instead of just one of the two; I think I know the answer

Audio signals follow the first definition given by Wikepedia:

"Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC)"

Thus, I would also call it AC. Edit: But if I had to describe it, I would probably call it modulated AC.

For a random AC square wave, at how low a frequency would you stop calling it AC and start calling it DC?



I'm talking about the current going to the light bulb, not the brightness of the light seen by the receiver of the message



Neither LED's or sound were installed in the trains when MM and DCC was developed, a small capacitor could keep the decoder alive

I'm sure it's a matter of transmitting as much power as possible, without raising current or voltage to a dangerous level

They could easily have designed a system having only positive ( or negative ) signals and zero; but that would not be smart, since you wouldn't get power transmitted while you were sending zeros ( If zeros were designed as 0V; but you know what I mean )

By using both the positive and the negative side, they kept the peak voltage at the same level as in the analog systems, without raising the current

Per.

Well, whoever wrote the DCCWiki says DCC isn't AC in this blog

https://dccwiki.com/DCC_Power#

Firstly

"There are many myths surrounding the DCC signal. Most of those myths are the result of applying analog ideas to a digital concept. (Which I've realised might be part of my problem)

"This is not an AC signal, as the rail will have positive voltage on it, or none, at any point in time. What is happening is the current is changing direction as it moves from one rail to another. Measuring this with an oscilloscope will display a peak-to-peak signal, which many will claim supports their assertion that the signal is an AC waveform. Since there is no reference point, the trace only indicates which connection was more positive than the other at a point in time. "

And from the blog you posted

https://dccwiki.com/DCC_...(Power)#Some_DCC_Details

"There are a number of erroneous myths circulating about Digital Command Control that refuse to fade away. Most are the result of applying analog concepts to a digital technology.. "

" DCC is Alternating Current
DCC is a form of Alternating Current
DCC has Polarity.

Correct Answer: None of the Above. The DCC signal on the track is a binary signal, where it is either ON or OFF. One rail is always the inverse state of the other. "

"The DCC signal is not an Alternating Current sine wave, nor is it a special form of AC. The DCC signal switches quickly between states, and varies the time period the rail is High or Low to convey information to trains on the track. Contrary to popular belief, there is no negative voltage present on the rails.
There are many who claim there are both positive and negative voltages, citing the Peak-to-Peak amplitudes as seen in the 'scope trace. This is often a case of erroneous information being repeated so often that it's accepted as a fact. See DCC Power for more details which explain how this is not possible. It is not an analog waveform, where frequency, phase, polarity, or amplitude have meaning."

That all seems to conflict with what Dale Schultz says in his new blog

"there is no other logical conclusion other than the fact that DCC is a type of alternating current. "

Who to believe?

There's also a blog on measuring track voltage, although I have a feeling the volt meter method may not be appropriate in a Marklin environment given there's no separate booster ground reference point to use on a Marklin booster. - https://dccwiki.com/Measuring_Track_Voltage

If you can't use a True RMS volt meter to properly measure the track voltage, how do the track voltage measuring devices work, such as the Rrampmeter and Bachmann / Proses devices?

https://www.hobbysmith.c...ii-amp-volt-meter-detail

https://www.conrad.com/p...ter-2-rail-track-1233499

The suggestion to use the AC+DC setting on my Fluke to measure the CS3 output came from forum member bph - https://www.marklin-user...t47702-CS3-Track-voltage

In that thread he references a Fluke article about True RMS

https://www.fluke.com/en...ctrical/what-is-true-rms

In that article Fluke advise that a good True RMS meter can correctly measure a square wave signal.

Both the Fluke 289 bph has and my Fluke 287 (essentially the same meter but the 289 has some additional features) have 100 kHz AC bandwidth.

As a result of the suggestion to use AC+DC mode I copped derision from another forum member, which led me to suggest the particular forum member might be inhabiting an alternate universe. I probably should not have done that but was somewhat frustrated by all the conflicting opinions being fired around. As I said, I'm not an expert by any means so rely on folks more knowledgeable than me. When they can't agree.....

Then there is the method of rectifying the signal and measuring the DC voltage from that, a method I had seen referenced before on the net (though I can't recall where).

In all of these discussions all I was wanting to know was how to properly measure the CS3 track output. I've discovered that the definitive answer to that question is that there is no definitive answer.

Not at all Hopobcn, welcome to the forum and thanks for your post showing the scope traces.

The traces are interesting but I'm also interested in the Hankek scope you have as I've been considering this particular scope to purchase for myself. Aside from the obvious MRR uses, I have a couple of open reel recorders that I'd like to replace all the capacitors in and re-calibrate after completion for which I would need a scope. These particular scopes seem to be ideal for hobbyists.

The only thing that drives me nuts about this scope is that they only give you one probe despite it being a dual channel scope!