# Adding Meters to [DCC] V-AC "Digital Operations"..



## ED-RRR

There are several "Threads" / "Posts" regarding this subject in this "Forum"..
--> Connecting meters to [DCC] digital operations..
I have decided to combine all of my "Found Research" into (x1) new thread.. 

*Special Notes:*
There are also many confusing/conflicting information regarding Digitrax V-AC "Track" power supply..
This is due to that replaced Digitrax documents have "Not" been deleted or updated.. 

*Sorry:*
I had to copy and paste my information --> "Together".. To be able to post this information..

*Welcome Hecklers:*
Is any of my information --> *"Incorrect" ??*
All of my information is backed up with (100%) proof information..

*Question:*
Why are all [DCC] operating systems using *V-AC* "Track Power" when everything else requires* V-DC ??*
The very first [DCC] system was "Dynatrol" introduced in 1978..
My very first [DCC] system was with *"Dynatrol"* using *V-DC *"Track Power".. 
This corporation owns the "Patent" on Digital model railway control systems using *V-DC* "Track Power".. 

=========================

*Digitrax: (Track Power)..*
Setting Scale = "Maximum" Track Voltage Setting..
N = *12 volts AC*
HO = *15 volts AC*
O/G = *20 volts AC*

Mark Gurries: (Registered NMRA & DCC Advisor)..
https://sites.google.com/site/markgurries/
*NMRA - [DCC] V-AC Standards..*
[N] Scale (Track Voltage) = *12.V-AC*
[HO] Scale (Track Voltage) = *14.V-AC*
[O] Scale (Track Voltage) = *18.V-AC*









*Digitrax: (Track Power)..*
KB322: DCS100 - Track Voltage Adjustment
http://www.digitrax.com/tsd/KB322/dcs100-track-voltage-adjustment/
The target voltages for the different Scale Settings are:
N - *12 volts*
H.O. - *15 volts*
O/G - *20 volts*
Why is Digitrax recommending the *"Target"* values at *"Maximum" *track voltage ??
While NMRA - [DCC] V-AC Standards are not *"All"* the *"Same"..*

*Digitrax: (Track Voltage)..*
KB909: Track Voltage Measurement on DCC Layouts with Direct Home Wiring
http://www.digitrax.com/tsd/KB909/track-voltage-measurement-on-dcc-layouts-with-dire/
Track Voltages should be "Approximately" (depending on trim pot adjustments you have made):

==============

*Special Notes:*
When using a Command Station and Booster/Boosters the layout block sections should have the "Same" V-AC track power supply..
Using a "Different" main power supply to the Command Station and each Booster/Boosters could have a "Different" voltage input..
This will affect the actual "Track" V-AC supply..
When using "Different" V-AC transformers, main power supply to the Command Station and each Booster/Boosters will have a "Different" voltage input..
......


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## ED-RRR

*Different Types Of Meters..*

*Special Notes:*
All [DCC] systems operate using "Digital" V-AC to power the track..
To "Accurately" measure V-AC "Digital Operations" requires "RMS Meters".. 
A true-rms device (rms = root mean square) can measure:
- Voltage (V-AC)..
- Current (V-AC).. 

*Warning:*
- A "Standard" digital hand "Mutimeter" can "Not" be used..
- A "LED Digital" display meter can "Not" be used..









*Special Notes: (#1)*
Analog meters and the custom made RRampMeter by DCC Specialties, can be used..

*Special Notes: (#2)*
"Analog" meters Volts (AC) & Amps (AC) a 2.5% accuracy.. (Not Very Expensive $'s)..
"Digital" meters Volts & Amps from RRampMeter by DCC Specialties with a 2.0% accuracy.. (Very Costly $'s)..
For example 14.V-AC at 2.5% accuracy = (+/-) 0.35 V-AC
That is a 0.7 V-AC difference.. (High - Low V-AC Measurements)..









*Special Notes: (#3)*
Ebay sells RMS Volt Amp Meter for US $8.00.. (Very Cheap)..
Can be used to measure AC/DC voltmeter, ohmmeter, diode..
Ebay Search: RMS Volt Amp Meter 
Model # A830L
AC Voltage: 200mV/2/20/200/500V ±(0.5%+5).. 
AC Current: No Posting









*Help Wanted:*
I am "Not" an Electrical Engineer..

*Question:*
This meter measures AC Voltage: 200mV/2/20/200/500V ±(0.5%+5).. 
What tolerance does this actually mean ±(0.5%) --> (±5) ?? 
- Thanks -
......


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## ED-RRR

*Meters: [DCC] V-AC "Track" Wire Connections..*

*Technical Information:*
*Voltage* is measured in a *"Parallel"* meter connection..
*Amps* is measured in a *"Series"* meter connection..

*Special Notes:*
When it comes to *"Voltage"* --> *"No"* special wiring connections are required..
When it comes to* "Amperage"* --> "*Special"* wiring connections are required..








......


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## gunrunnerjohn

I'll point something out and risk the typical wrath when posting some facts to your threads.

The *A830L Handheld Digital Multimeter* that you recommend is not a true-RMS meter, so it's no more suitable for DCC than any other generic cheap digital multimeter. I'm not sure why you picked this particular model.



ED-RRR said:


> *Question:*
> This meter measures AC Voltage: 200mV/2/20/200/500V ±(0.5%+5)..
> What tolerance does this actually mean ±(0.5%) --> (±5) ??
> - Thanks -
> ......


The 0.5%+5 specification means the measurement is made to .5% and then +/- five display counts.

If you're measuring 1.000 volts on a 3 1/2 digit digital meter, the resulting tolerance for the measurement with this meter ends up being 1%.


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## Mark R.

Command Control goes back considerably further than 1978 ....

http://www.dccwiki.com/DCC_History

It wasn't until 1992 that any kind of "standard" DCC was created, based on the Lenz protocol created for Marklin.

Mark.


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## Mark R.

Standard meters CAN be used to accurately measure DCC voltage (both peak and average) and current with a minimum of external components - and cost should only be a couple dollars. Scroll about 2/3 down the page ....

Measuring DCC Track Voltage and Current (Amperage)

Mark.


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## Mark R.

As for the differences of DC and AC systems ....

A "signal" can be transmitted only via AC voltage or radio frequency. On DC systems, this signal is (was) transposed over the DC voltage. A high frequency AC voltage can be super-imposed over a DC voltage with appropriate filters in both the command station and the receiver in the engine.

Early sound systems used this kind of technology to send sound through the DC rails using a high frequency signal that did not affect the DC control voltage.

Mark.


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## fcwilt

I am probably going to regret this.

*Why are all [DCC] operating systems using V-AC "Track Power" when everything else requires V-DC ??
*

The following glosses over any number of things but I want to keep it as simple as possible.

To start with V-AC is not a term that I would use in discussing DCC. 

A DCC command station places a voltage on each rail that switches quickly from 0 to some max voltage. At any point in time the voltage on the rails are "opposite" one another. When one rail is at 0 volts the other rail is at max volts and vice versa.

As a result the average DC voltage is zero which is a good thing in that a DC loco, if placed on the rails, will just sit and buzz rather then take off down the track.

To convey information the timing of the switching of the voltage is varied.

There are many sources of detailed information and I'm not going to duplicate all that information here.


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## wvgca

gunrunnerjohn said:


> The *A830L Handheld Digital Multimeter* that you recommend is not a true-RMS meter, so it's no more suitable for DCC than any other generic cheap digital multimeter. I'm not sure why you picked this particular model.


In my opinion, a cheap meter is perfectly fine, with some qualifications though ..
an 'el cheap' meter, when reading a standard sine wave AC voltage will give the peak voltage , not a true rms reading, but the conversion factor has been around for a long time, multiply by 0.707, I just use 0.7, close enough in most cases .. to give the effective heating value of sine wave AC ...

If you have a meter already, and want to check it, plug it into a normal wall outlet, if it reads 115-120v [depending on area], it will give a 'close enough' to rms voltage reading, if it shows around 170v, it's just reading the 'peak' voltage, and needs the correction factor applied ..this is, of course, for a relatively clean sine wave, the less non-sinusoidal the wave is, the less accurate it will be ..

Now DCC is a different matter, it's not sine wave AC, it's square wave, and depends on how the meter interprets this ..a good quality 'true rms' AC meter will have no problem as they can detect the difference between sine, square, sawtooth, etc ... A cheap meter that reads peak value AC may, in most cases, give a correct reading, as the DCC waveform is square wave, and needs no correction ..peak value is the same as true rms on a square wave, once rectified, In normal usage, even while the DCC waveform is changing frequency, it will not affect peak values, but in some systems that can 'skew' the on time of each half to drive DC locos, the readings will be 'off' while in this mode of operation

this is just for voltage readings, the site / page that Mark R referenced has some decent low cost circuits to derive DCC current ..

My opinion, for what it's worth .... enjoy


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## gunrunnerjohn

Exactly, my comment was directed at the selection of this particular cheap meter after the previous statement that cheap meters were inappropriate. 

I just connect my 'scope if I really need to see the exact waveform and peak voltage.


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## fcwilt

In addition to my Textronix scope I have one of these imports:

http://www.mcmelectronics.com/product/TENMA-72-8470-/72-8470

It's nice to have a small, battery powered unit that is both a multi-meter and a scope when working on the layout.


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## gunrunnerjohn

Spendy little sucker!


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## fcwilt

gunrunnerjohn said:


> Spendy little sucker!


How much do you suppose folks spend on locos?

I've got several locos that are more than that unit.

A couple of quality sound equipped locos may well be more.

I hate to think I much I have tied up in this hobby if I totaled it ALL up.

Compared to that $600 doesn't loom so large.

And it really does come in handy.


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## wvgca

I have a couple of older scopes, a B&K, and ??, but while they are useful to see exact waveforms, in general they are clumsy to move around, unless you buy a relatively expensive handheld one ..
ED-RRR's idea is a good one, even if an Ebay 8 buck multimeter may have questionable accuracy, it's a lot better than nothing, checking for shorts, power reductions, and bad track joints, just a very handy tool that all trains hobbiest's should have available


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## gunrunnerjohn

I have a dual-trace storage 'scope, it's plenty for the task. It's certainly portable enough, it's got a handle and only weighs a few pounds. I paid around $350 for it, and it's a 100mhz model. I have an old Hitachi dual-trace analog model that's my backup if the digital one ever craps out, but it hasn't been turned on in several years.


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## ED-RRR

*T-RMS Meters..*



gunrunnerjohn said:


> The A830L Handheld Digital Multimeter that you recommend is not a true-RMS meter, so it's no more suitable for DCC than any other generic cheap digital multimeter.
> I'm not sure why you picked this particular model.


As I stated I am *"Not"* an electrical engineer and that is why asked for *"Help".. *

Digital LCD Multimeter Auto Range True RMS Volt AMP Meter Capacitance Temp
Model #A830L

After closer examination "No" where on the meter or package does it state T-RMS..
This is Ebay "Fraud"..

There are T-RMS meters (T-RMS Indicated On Meter) that are "Not" cheap ($'s) even on Ebay..
......


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## ED-RRR

*V-DCC..*



fcwilt said:


> To start with V-AC is not a term that I would use in discussing DCC.
> A DCC command station places a voltage on each rail that switches quickly from 0 to some max voltage.
> At any point in time the voltage on the rails are "opposite" one another.
> When one rail is at 0 volts the other rail is at max volts and vice versa.


*[fcwilt]:*
What you are stating is true and correct for *[DCC]* that an "Electrical Engineer " can understand..

*Mark Gurries:* (Electrical Engineer) & (DCC Clinic)..
NMRA Track Voltages..
NMRA STANDARDS S-9 Electrical..
The RMS value of NMRA digital signal, measured at the track, shall not exceed by more than 2 volts(#8) the voltage specified
in standard S-9 for the applicable scale. 

N scale = 10VDC + 2V => 12V DCC.
HO & O = 12VDC + 2V => 14V DCC. 
Large Scale = 16VDC + 2V => 18V DCC.

As you can see Mark Gurries uses the term *V-DCC* using the RMS value of NMRA digital signals.. 
Digitrax [DCC] documents state "Volts"..

I use the term *V-AC "Track Power"* because this "Thread" is in regards of using "Meters" for *[DCC]..*
This is to simplify things for the vast majority of *[DCC]* users..
A vast "Majority" of *[DCC]* users do "Not" even know "What" we are talking about regarding T-RMS "Meters"..
......


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## ED-RRR

*Alternatives To Measure Track Voltage..*

*[Mark R.]:* Posting #7
To convert *[DCC] *to V-DC, to be measured by a "Standard" DC voltmeter, and simply refer to it as volts..
Requires a "Special" made circuit board..

*[wvgca]:* Posting #9
a good quality 'true rms' AC meter will have no problem as they can detect the difference between sine, square, sawtooth, etc ... 
A cheap meter that reads peak value AC *may,* in most cases, give a correct reading,

*[gunrunnerjohn]:*
*[fcwilt]:*
*[wvgca]:*
Connecting *"Scopes"* to see the exact waveform and peak voltage..

This could be a prime *"Example" *why I get *"Mad"* in this "Forum"..
Sorry to interrupt the "Posts" between the "Electrical Engineers"..

*Questions:*
- Are you "Not" going from "Meters" to *"Scopes"*, changing the subject matter ??
- Are you "Not" posting discussions way too "Advanced" for (99.9%) of *[DCC]* users ??
......


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## fcwilt

*As you can see Mark Gurries uses the term V-DCC using the RMS value of NMRA digital signals.. 
*

What is the point in making up a new term when Vrms and Vpeak are already in use and well understood.


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## fcwilt

ED-RRR said:


> give a correct reading,
> 
> *[gunrunnerjohn]:*
> *[fcwilt]:*
> *[wvgca]:*
> Connecting *"Scopes"* to see the exact waveform and peak voltage..
> 
> This could be a prime *"Example" *why I get *"Mad"* in this "Forum"..
> Sorry to interrupt the "Posts" between the "Electrical Engineers"..
> 
> *Questions:*
> - Are you "Not" going from "Meters" to *"Scopes"*, changing the subject matter ??
> - Are you "Not" posting discussions way too "Advanced" for (99.9%) of *[DCC]* users ??
> ......



Looks like we should clear our posts with ED-RRR first just to be sure we haven't broken some unspoken rule.


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## ED-RRR

*Off Subject Example..*



fcwilt said:


> What is the point in making up a *new term* when Vrms and Vpeak are already in use and well understood.


*[fcwilt]:*
I will talk very *"Slowly" *so you can "*Fully"* understand me !!
As I previously have "Stated"..
This *"Thread" *is using the term *V-AC,* because we are installing *V-AC* *Meters* to measure *[DCC]* "Track Voltage..

*[gunrunnerjohn]*: 
And you wonder why I get "Mad" at times..
......


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## fcwilt

ED-RRR:

Where do you get off mocking people? 

I cannot say what should be said so I will put it this way - your arrogance is totally unjustified.


Using a AC meter to measure something does not make what is being measured AC.

The correct terms are Vrms or Vpeak and that is a simple fact that all your snide remarks cannot alter.


You talk about all the wonderful knowledge you have to impart and yet you post stuff like that.


Here is something you should memorize and take to heart:

*
He who knows and knows he knows, he is wise—follow him!
He who knows and knows not he knows, he is asleep—wake him;
He who knows not and knows he knows not, he is simple—teach him;
He who knows not and knows not he knows not, he is a fool—shun him;
*


My apologies to the other members here for going off-topic.


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## gregc

i have to ask why someone wants to measure track voltage and what do they need for that purpose?

I'll suggest 

they want to see if there is any track voltage
- a lamp 

they want to see if there is a loss of track voltage between their command station and some point on the track
- an AC meter

they want to compare voltage from similar or comparable systems
- an AC meter

they want to see if their system meets spec (NMRA S-9.1)
- a (calibrated) scope
- a (calibrated) true-rms meter
- a (calibrated) DC meter with DC-bridge of known voltage drop

the lab equipment on my bench at Qualcomm is calibrated at least one a year (and I don't do standards testing). The irony is that the EE's understand the above and know what it close enough. It's the non-EEs that think they need more accurate measurements or more expensive equipment.

I believe in most cases, an inexpensive multi-meter is more than adequate. Knowing how to use it and what is being measured would be helpful.

It would be a shame for someone to unnecessarily buy an expensive piece of test equipment.


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## ED-RRR

*Kiss --> Keep It Simple Stupid.. (Meter System)..*

It is starting to get very "Confusing" how to measure "Actual" V-AC "Track" power supply in this "Thread".. 
"Actual" track "Voltage" and "Amps" requires *T-RMS meters..*

Why "Not" just use *"Analog"* Volt/AC and Amp/AC "Meters" !!
Also much cheaper ($'s) and much "Easier" to use..

*Warning:*
The "Meters" must be *V-AC..*

















......


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## time warp

While putting meters on the panel isn't a bad idea, it looks to me like that setup would really just be for reference. Even panel meters on a DC system really don't tell you much.
The handheld meter, as already stated, would actually be the best thing to have on hand. In the event of a trackwork continuity issue the panel Meters won't get you anywhere. The multi meter or o- scope will.
ED-RRR, I think the consensus here is that there isnt really a need for them.
Also I would suggest that you look in to getting a scope, they are wonderful tools and tell you infinitely more than a regular meter can. Just my opinion though.


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## ED-RRR

*Meters.. Why ??*



time warp said:


> While putting meters on the panel isn't a bad idea, it looks to me like that setup would really just be for reference.
> Even panel meters on a DC system really don't tell you much..
> 
> In the event of a track work continuity issue the panel Meters won't get you anywhere.


*WesternCumberland:*
https://sites.google.com/site/westerncumberland/home
Mark Gurries (Electrical Engineer - DCC Clinic) is one of two or more electrical engineers that help build David Parks layout..

I count (x10) Digitrax units and (x10) DCC Specialties *"RRampMeters"..*









Some of you are probably scratching your head, *"Why" ??*

It is very *"Important"* that all the individual [DCC] "Blocks" have the "Same" *V-DCC* power supply..
This is to insure smooth locomotive transitions from "Block" to "Block"..
Will also *"Indicate"* if there are any *V-DCC* drop age in a "Block" that may/will cause locomotive problems..
......


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## time warp

Yes, the ammeters, but it looks like the voltmeters are going to read very close to 0 volts normally, unless there's some kind of problem. You will then have to resort to portable test equipment anyway. So that why I said they would be OK as a reference.


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## ED-RRR

*Meters.. Why ??*



time warp said:


> Yes, the ammeters, but it looks like the voltmeters are going to read *very close to 0 volts normally,* unless there's some kind of problem.


*When using [DCC],*
There is "Always" a "Constant" *V-DCC* power supply to the "Track"..

*[time warp]: *Question
Why would there be (very close to 0 volts normally) 
when the "Track" is *"Always" *powered with *V-DCC* ??

Measuring the *V-DCC* from each individual Digitrax unit,
"Constantly" supplying "Track Power"..
......


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## time warp

Refer to post #8, that's why I would favor the scope, it will let you see the square wave.


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## wvgca

ED-RRR said:


> It is very *"Important"* that all the individual [DCC] "Blocks" have the "Same" *V-DCC* power supply..
> ......


That makes sense , however in the image in that post, the voltages aren't the same .. a very large discrepancy ..
I read [from left to right] 
11.9, 11.5, 12.1, 13.8, 13,4, 14.0
and most are below what is supposed to be 'recommended' DCC track voltage ..
any idea of why? mostly just curious ..


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## johnfl68

ED-RRR said:


> Some of you are probably scratching your head, *"Why" ??*


Most people on here aren't running with around 2000 feet of track and using a Command Station plus 12 Boosters with 100+ amps of available track power either.

On a layout that large, it makes sense to have meters on everything, but the typical home user with a Command Station and possibly 1 Booster if that doesn't really need to do all that.

Again, a simple basic meter, with or without True RMS, and the knowledge of how to properly use it will go a lot further for the typical user than spending all the time, effort, and money for panel meters that may only show you a small part of the whole picture. 

Learn to use the tools you have, before spending money on the tools that you don't really need. Then you will have more money to buy the trains and other things that you want, and more time to spend running them.


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## time warp

wvgca said:


> That makes sense , however in the image in that post, the voltages aren't the same .. a very large discrepancy ..
> I read [from left to right]
> 11.9, 11.5, 12.1, 13.8, 13,4, 14.0
> and most are below what is supposed to be 'recommended' DCC track voltage ..
> any idea of why? mostly just curious ..


It looks to me like the voltmeters being attached to the track would be more of a Telltale than an actual voltage indication. Am I thinking right?


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## ED-RRR

*Meters.. Why ??*



time warp said:


> Refer to post #8, that's why I would favor the *scope,* it will let you see the square wave.


*[time warp]:* Question
Are "You" now confirming that a T-RMS meter will *"Always" *measure the "Constant" *V-DCC * power supply to the "Track" ??
That you had posted "Incorrect" *V-DCC* "Information" !!

Again, this "Thread" is "Only" discussing *"Meters"..*
Not expensive ($'s) *"Scopes"* requiring to be an *"Electrical Engineer"* to operate !!

*[time warp]:* Question
Why would Mark Gurries (Electrical Engineer - DCC Clinic) 
install "Expensive" ($'s) *"Scopes"* to each Digitrax unit,
when he is "Only" concerned about the Track *V-DCC *?? *(Volts)..*

*[gunrunnerjohn]:*
Why I get "Mad" from other individuals posting in my "Thread"..
As I had "Previously" stated..
This "Thread" is "Not" about *"Scopes"*, but *"Meters"..*
......


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## time warp

No, Ed. I'm just saying that a scope would allow you to see the square wave.
I like using them, they give you a lot of info that you can't see with a meter..
If you put all of the comments on this thread together, it all makes perfect sense.
Actually it's good you brought up this meter discussion. I've enjoyed the lessons.
Relax man, were all on your side.


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## fcwilt

*Not expensive ($'s) "Scopes" requiring to be an "Electrical Engineer" to operate !!*

1. Most any person who is capable of functioning successfully in today's world of smart-phones, tablets, computers, GPS navigation systems is capable of using a scope. You don't need to be a EE.

2. While everyone has a different take on what is expensive I don't consider $600 over the top given the wonderful versatility of the scope. My SAT TV bill is appx $2600 annually. My extended family phone bill is in excess of $6000 annually. Compared to those, which the family considers "essential" services, $600 seems like a real bargain.

YMMV.


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## gregc

ED-RRR said:


> It is very *"Important"* that all the individual [DCC] "Blocks" have the "Same" *V-DCC* power supply..
> This is to insure smooth locomotive transitions from "Block" to "Block"..


not sure how important this is

some block detection circuits use DC bridges that will drop 1+V. There could be variations between circuits.

decoders with BEMF don't depend on track voltage, but adjust the PWM duty-cycle to maintain speed.


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## Cycleops

johnfl68 said:


> Most people on here aren't running with around 2000 feet of track and using a Command Station plus 12 Boosters with 100+ amps of available track power either.
> 
> Learn to use the tools you have, before spending money on the tools that you don't really need. Then you will have more money to buy the trains and other things that you want, and more time to spend running them.


I think that sums up things perfectly. Seems some people get obsessed with electronic gadgetry just for the sake of it.


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## time warp

ED-RRR said:


> *[time warp]:* Question
> Are "You" now confirming that a T-RMS meter will *"Always" *measure the "Constant" *V-DCC * power supply to the "Track" ??
> That you had posted "Incorrect" *V-DCC* "Information" !!
> 
> Again, this "Thread" is "Only" discussing *"Meters"..*
> Not expensive ($'s) *"Scopes"* requiring to be an *"Electrical Engineer"* to operate !!
> 
> *[time warp]:* Question
> Why would Mark Gurries (Electrical Engineer - DCC Clinic)
> install "Expensive" ($'s) *"Scopes"* to each Digitrax unit,
> when he is "Only" concerned about the Track *V-DCC *?? *(Volts)..*
> 
> *[gunrunnerjohn]:*
> Why I get "Mad" from other individuals posting in my "Thread"..
> As I had "Previously" stated..
> This "Thread" is "Not" about *"Scopes"*, but *"Meters"..*
> ......


Ed, can you post a picture of how you have the meters set up on your own system? How do they work out for you?


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## wvgca

decided to find out for myself about using low cost AC meters to measure DCC track voltage ...

dug up four ordinary AC meters , within the 20V maximum display ...and the scope alongside for rudimentary result verification ..

meter 1, cheap chinese, 7V indicated, appears to read 'average' AC voltage
meter 2, cheap US made, 17V indicated, appears to read 'peak' plus spike value
meter 3, decent US made, 12V indicated, appears to read roughly .707 RMS value
meter 4, Simpson, reads 15V, closest so far, ... 

No indication on ANY of the AC meters to show whether they read, average, peak, or some type of RMS by adjusting scale plate ..

too much of a 'crap shoot' to get an accurate AC meter, without resorting to having a "true rms' meter ...

So: Plan2
simple bridge rectifier , and a cheap DC meter ... and it works as expected to ... low cost, readily available ...

Drawback is minor, you lose 1.4V through the bridge ...actual DCC track voltage is 1.4 higher
Advantage: you can see exactly what voltage is available to the DCC decoder logic [after being rectified on the decoder itself] ..

the meter I used is for auto application 13V in the middle, and just a 4V swing to either side ... perfect 
edit" another bonus is being able to use cheap digital display as well, for voltage


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## Lemonhawk

The scope is the only thing that's accurate since the signal is PWM. Meters, as wvgca has shown, are all over the place. So the meters only saving grace is that it could indicate a problem if they deviate from there normal reading - what ever normal is. I like the idea of using a DC voltmeter and a bridge, since that's the decoder input. I agree with wvgca.


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## time warp

Wvgca- thanks for clearing that up, I was having trouble making sense of some of this.
ED-RRR- glad you brought this up. You should stop getting upset with others for starting discussions about your posted material. I found this to be a good learning experience.
So it's proven, any given standard meter will give you a RELATIVE reading, OK for reference but not necessarily accurate. That can be useful if you are aware of what your" normal" reference voltage readings are.
I was mistaken in that I thought a voltmeter would show "0" volts, or close to in reference to the rails.
If you were to have " block" meters. They would have to agree in order to be of any value then. 
Thanks again, ED. Next time please invite commentary. Everybody, including you, wins that way!


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## gunrunnerjohn

wvgca said:


> Drawback is minor, you lose 1.4V through the bridge ...actual DCC track voltage is 1.4 higher


A Schottky bridge will cut that voltage drop to less than half if you want to improve the accuracy.  At low currents, the drop across many Schottky diodes can be in the .20 to .25 volt range. This would give you a 0.4 to 0.5 total voltage drop.


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## ED-RRR

*[DCC] Track Power Definitions..*

*(#1)*
There is the definition *V-AC (RMS)* track measurement.. 
*- OR - *
*(#2)*
There is the definition *V-DCC* track measurement.. 

Both have the *"Same" *meaning..








......


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## wvgca

gunrunnerjohn said:


> A Schottky bridge will cut that voltage drop to less than half if you want to improve the accuracy.


Yes, very true, I do have those, even a recent bagful purchase from ebay right next to me [5817-1A-20V], but for the test I decided to use a normal silicon diode bridge ... for two reasons, 1st, the availablity / cost would probably mean the average user / tester would have silicon diodes handy. and 2nd, I don't know what the decoder manufactures use on 'most' decoders, I am assuming standard silicon, just for the cost / supply benefit?
I only looked a ONE decoder, a Digitrax DH163 as it was the only spare one that I had that wasn't shrink wrapped, and it had silicon diodes for track current rectification


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## gunrunnerjohn

I guess I don't see how what diode the decoder manufacturer used makes any difference. I thought we were just trying to make accurate measurements, I was just aiming at that target.


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## ED-RRR

*Scope -OR- V-DCC Meter..*



Lemonhawk said:


> The scope is the only thing that's accurate since the signal is PWM.


Yes you are (100%) correct for *V-DCC*



Lemonhawk said:


> I like the idea of using a DC voltmeter and a bridge, since that's the decoder input.
> I agree with *[wvgca].*


(#1)
*[wvgca]* *"Stold"* this idea from* [Mark R.]* --> Posting #6..__..
http://www.wiringfordcc.com/track.htm
Measuring *[DCC]* "Track Voltage" using a *V-DC* "Meter".. (Allan Gartner's DCC Web Site)..

(#2)
*[wvgca]*
Are you kidding me ??__
Using a cheap farm tractor V-DC "Battery" meter.. 









*- But -*

It would "Also" be nice to know what *"Amperage"* (Current) that is being used !!
--> This will require "*Special" wiring..* (Series)..
......


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## time warp

ED-RRR said:


> *(#1)*
> There is the definition *V-AC (RMS)* track measurement..
> *- OR - *
> *(#2)*
> There is the definition *V-DCC* track measurement..
> 
> Both have the *"Same" *meaning..
> 
> View attachment 191834
> 
> ......


RMS is the basis for the standard.


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## wvgca

gunrunnerjohn said:


> I guess I don't see how what diode the decoder manufacturer used makes any difference. I thought we were just trying to make accurate measurements, I was just aiming at that target.


To get the 'closest' to actual DCC track voltage simple, Yes , the schottky diodes would give a closer and more accurate end result, and using the DC bridge would allow the use of those cheap DC digital voltmeters, nicer looking display, and probably a lower cost than a decent DC analog meter .. I do have some spare ones from when I bought some on Ebay that were advertised as AC digital meters, but weren't


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## wvgca

ED-RRR said:


> (#2)
> *[wvgca]*
> Are you kidding me ??__
> Using a cheap farm tractor V-DC "Battery" meter..
> 
> View attachment 191842
> 
> 
> ......


Yep, a cheap analog meter, probably from Wally World or Peavey Mart ...
and Yes, it's a spare if one of my tractors needs one ,
and that's a *'fact'*


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## time warp

Here we go!


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## ED-RRR

*My T-RMS Meters..*



time warp said:


> Ed, can you post a picture of how you have the meters set up on your own system?
> How do they work out for you?


I have my own small private [HO] scale layout 13' feet long and 7' feet deep.. (Industrial Town)..









I am presently totally re-wiring my *[DCC]* wiring system for 
CTI - Model Railroad Computer Control
http://www.cti-electronics.com/
So all of my "Track Signals" actually function "Correctly" .. (Infrared Tunnel Sensors)..









Since I have a small private [HO] scale layout, no more than (x5) *[DCC] *locomotives will be operating at the "Same" time..
So I only have (x1) Digitrax DCS100 "Controller"..

I have/use the *DCC Specialties RRampMeter (Ver. #1)* that is custom mounted into my "Front" control panel.. 
Purchased from Tony's Train Xchange.. (US $60.00)..
https://tonystrains.com/product/dcc-rrampmeter-i/

Though it looks to be costly ($'s), it is a T-RMS for *[DCC] **"Voltage"* and *"Current".. *(x2 Meters Total & x2 LED Indicators)..
The Digitrax "LocoNet Panel" has a small "Track Status" LED..
I like that there is a "Larger" *[DCC]* "Green" LED that indicates that the "Track Status"..









Connecting the RRampMeter is *"Very"* easy and does "Not" require any "Special" wiring..









*Again:*
This (x1) simple unit *"RRampMeter" * will measure your *[DCC]* "Track *V-DCC *and *Amps..*
......


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## johnfl68

ED-RRR said:


> *
> There is the definition V-DCC track measurement..*


*

Where is this NMRA document that you say uses "V-DCC"?








*


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## gregc

here's a link to the NMRA S-9.1 standard.

see line 55 where it says "The RMS value of NMRA digital signal, "


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## johnfl68

gregc said:


> here's a link to the NMRA S-9.1 standard.
> 
> see line 55 where it says "The RMS value of NMRA digital signal, "


Yes, I see RMS, I understand RMS - but not this made up "V-DCC" word that ED-RRR keeps trying to use.


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## gregc

yes. 

the spec uses conventional textbook terminology that every engineer understands.


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## fcwilt

johnfl68 said:


> Yes, I see RMS, I understand RMS - but not this made up "V-DCC" word that ED-RRR keeps trying to use.


When I google V-DCC I get info about "voltage-dependent calcium channels".


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## time warp

ED-RRR said:


> I have my own small private [HO] scale layout 13' feet long and 7' feet deep.. (Industrial Town)..
> 
> View attachment 191850
> 
> 
> I am presently totally re-wiring my *[DCC]* wiring system for
> CTI - Model Railroad Computer Control
> http://www.cti-electronics.com/
> So all of my "Track Signals" actually function "Correctly" .. (Infrared Tunnel Sensors)..
> 
> View attachment 191858
> 
> 
> Since I have a small private [HO] scale layout, no more than (x5) *[DCC] *locomotives will be operating at the "Same" time..
> So I only have (x1) Digitrax DCS100 "Controller"..
> 
> I have/use the *DCC Specialties RRampMeter (Ver. #1)* that is custom mounted into my "Front" control panel..
> Purchased from Tony's Train Xchange.. (US $60.00)..
> https://tonystrains.com/product/dcc-rrampmeter-i/
> 
> Though it looks to be costly ($'s), it is a T-RMS for *[DCC] **"Voltage"* and *"Current".. *(x2 Meters Total & x2 LED Indicators)..
> The Digitrax "LocoNet Panel" has a small "Track Status" LED..
> I like that there is a "Larger" *[DCC]* "Green" LED that indicates that the "Track Status"..
> 
> View attachment 191866
> 
> 
> Connecting the RRampMeter is *"Very"* easy and does "Not" require any "Special" wiring..
> 
> View attachment 191874
> 
> 
> *Again:*
> This (x1) simple unit *"RRampMeter" * will measure your *[DCC]* "Track *V-DCC *and *Amps..*
> ......


Nice stuff! So I'm guessing the purpose of you starting this thread was to propose a less costly way to achieve similar results?
I believe we all would have enjoyed seeing what you had achieved personally. Wvgca- merely applied the suggestions you made, to use low cost meters , to the subject at hand.(the meter enclosure is of no importance).
The meter system you are using is incorporating the needed circuitry to achieve the desired result. These criteria can not be met using a simple wired in meter.
I think your motivation is admirable, and again, through this discussion we've all learned some things.


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## fcwilt

Just a bit of info in relation to CTI that was mentioned.

The CTI products are far from state of the art. I was going to use them until someone put me onto RR-CirKits gear.

These are state of the art, much more sophisticated in design, easy to install, configure with JMRI DecoderPro, are LocoNet compatible and the support is top notch.

The product line includes devices to handle every aspect of layout control:
- TowerMan for controlling turnout motors
- SignalMan for controlling signals
- WatchMan for occupancy sensing
- TowerMan for general input/output needs

RR-CirKits also makes a good number of "I/O modules" which provide for handling specific types of loads (example: relays) or specific types on inputs (example: optically isolated).

If you have need for anything like that I strongly suggest you investigate RR-CirKits before going with CTI.

Be warned the RR-CirKits web site is rather primitive.

Frederick


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## /6 matt

Since when do you need to be an electrical enginer to read and operate an oscilloscope? I learned that in high school automotive class. I was lucky to be in one of the few classes in 2011 that still had an oscilloscope but the point still stands.


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## ncrc5315

This has been an interesting thread, and go me to wondering as to how various meters, would compare to an oscilloscope. I tested a few of my meters, against my Fluke Scope Meter. In the attached photos, you can see the model number of the meter, and what it read.


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## gunrunnerjohn

All in all, pretty consistent readings I would say.


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## redman88

ncrc5315 said:


> This has been an interesting thread, and go me to wondering as to how various meters, would compare to an oscilloscope. I tested a few of my meters, against my Fluke Scope Meter. In the attached photos, you can see the model number of the meter, and what it read.
> 
> 
> 
> View attachment 194314
> 
> 
> 
> 
> View attachment 194322
> 
> 
> 
> 
> View attachment 194330
> 
> 
> 
> 
> View attachment 194338
> 
> 
> 
> 
> View attachment 194346



Any way you could get ahold of a cheap digital meter from harbor freight? That would be another good comparison.


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## fcwilt

The (obvious ?) advantage of a scope is that you can see what sort of waveform is on the rails and if it is good, so-so or bad.

On my layout I had some bad overshoot on the leading edges of the waveform. 

Enough that it confused a RRampMeter into reading out in AC mode rather than DCC mode.

It also caused problems with some mobile decoders.

The scope showed the problem clearly and also showed that the snubbers I then installed were doing a decent job of cleaning up the waveform.

Frederick


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## time warp

fcwilt said:


> The (obvious ?) advantage of a scope is that you can see what sort of waveform is on the rails and if it is good, so-so or bad.
> 
> On my layout I had some bad overshoot on the leading edges of the waveform.
> 
> Enough that it confused a RRampMeter into reading out in AC mode rather than DCC mode.
> 
> It also caused problems with some mobile decoders.
> 
> The scope showed the problem clearly and also showed that the snubbers I then installed were doing a decent job of cleaning up the waveform.
> 
> Frederick


Looks to me like the waveform display would be far more useful than the voltage meter reading.


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## ncrc5315

redman88 said:


> Any way you could get ahold of a cheap digital meter from harbor freight? That would be another good comparison.


I will see what I can do.


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## wvgca

fcwilt said:


> The (obvious ?) advantage of a scope is that you can see what sort of waveform is on the rails and if it is good, so-so or bad.
> 
> On my layout I had some bad overshoot on the leading edges of the waveform.
> 
> The scope showed the problem clearly and also showed that the snubbers I then installed were doing a decent job of cleaning up the waveform.
> 
> Frederick


On my layout I get about a 1.5V very narrow spike on ends of the long bus rails, appx 20 feet .. but so far no noticeable errors from the decoders .. this is in an 'unloaded' state, with no loco's on that bus line ... it drops to less than 0.5V with a decoder equipped loco within the far third of the bus line ..
unfortunately I did not run the bus lines in a twisted pair configuration, all are parallel and spaced around two inches apart .. no R/C snubbers on the ends as of yet ..


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