True RMS Meter vs RRampmeter

[wleron]

I currently have a true rms multimeter, but was wondering if the correct amps and volts would be indicated by the meter or should i purchase a rrampmeter from Tony's Train Exchange to get accurate readings on my dcc layout. I currently have the NCE PowerCab starter setup installed.

Thanks in advance for any help.

 

 

[gregc]

I would doubt there would be any difference for current.   That would be nice to know for selecting a decoder.

But the "correct" voltage is a bit ambiguos.   Wouldn't you only be interested in any drop between the unloaded track voltage and the voltage during operation?

[wleron]

Hi gregc

I am rather new to dcc and troubleshooting electronic circuits in general. I just wanted to know if my multimeter would be ok to measure dcc volts and amps and would give a meaningfull result.

In your experience would you buy the rrampmeter or just use the true rms multimeter?

I am learning a lot just by reading the posts on dcc but am still not confortable with my knowledge of how to troubleshoot existing or potential electrical problems.

Thanks again for your help and knowledge.

Ron

 

[gmpullman]

Hi, and 

I bought the version II RRampmeter with the test leads and housing ($85)

Although it performs well, I find that I really don't use it all that much. One thing it is handy for is to check track voltage by using an automotive lamp as a ballast load. You can find weaknesses in your feeder wiring this way.

I seldom use it as a current meter since I have four power districts and unless you want to semi-permanantly install them, it is a bit of a pain to place the meter in-line with the load.

So as far as getting accurate readings, sure, it will do the job but once you have that "accurate" information, then what?

So, in my opinion anyway, it is a neat toy but the novelty wears off pretty quickly and your money may be better spent elsewhere.

Just my 2¢

Regards, Ed

[peahrens]

Like Ed, I bought the Rrampmeter and have not really needed it, at least not yet.  Others have reported on its usefulness in certain situations.  Seems a matter of having it on hand so it's available if needed or wait and see if you need one, then have to wait.  

[wleron]

Thanks to all for the info.

I think i will just use my multimeter with a #912 bulb rated at 1 amp as a load and attach it across my test leads to check for any voltage drops. I will have to find a socket to fit the 912 bulb and attach some clips to the wire ends.

Ron

 

[richg1998]

It is a nice device.

I use the Harbor Freight multimeter with my NCE Power Cab and it measure 13.6 vac. Confirmed when I looked with my Scope.

Big help locating defective feeders.

Made my own DCC amp meter with two three terminal devices, IC's,  and a few passive components for about $12.00 and use the HF meter on the 20 ma DC scale. Agrees with the current reading on the Power Cab.

Made one for the club layout also that uses the five amp Power Pro. Indicates 4.97 amps when the booster trips. I use a high wattage rheostat as a variable load.

Rich

[rrinker]

 Here's the deal - the RMS voltage of a square wave is the same as the peak voltage. SO a simpel peak readingmeter should give the proper response. A basic RMS meter may be calibrated to expect a sine wave on the AC inputs, and so will read high when used with a square wave. A True RMS meter (True RMS is I believe a trademark of Fluke, but other brands off the same feature) will recognize multiple wave types on the AC input and read accordingly.

 Current is a different story. There are many meters that really can't measure AC current at all.

                  --Randy

 

[DigitalGriffin]

RMS meters divide by the Root Mean Square (Average Voltage / .707) to figure out AC voltage.  

AC voltage is sinusodal, and not square wave shaped like DCC.  So the mathematics to figure out voltage isn't the same.

A CHEAP voltage meter is to put a full bridge rectifier across the and buy a DC voltage meter with an trim pot that you can raise 1.4Volts (To compensate for the rectifier voltage loss)

This has a 1 Volt adjustment I believe.

http://www.amazon.com/3-2-30V-0-56inch-Digital-Voltmeter-Two-wire/dp/B00L8HK2H0/ref=sr_1_10?ie=UTF8&qid=1464115865&sr=8-10&keywords=voltmeter

If you use low loss (forward bias) diodes for the bridge the above meter should work fine.

[rrinker]

For a sine wave, yes. For a square wave, formula is here:

http://masteringelectronicsdesign.com/how-to-derive-the-rms-value-of-pulse-and-square-waveforms/

For a bipolar square wave, which is what DCC is, Vrms = Vpeak once you do all the math. A GOOD RMS meter can figure out the wave form and give the correct answer. A basic RMS meter assumes sine wave and gives the wrong answer for DCC.

                               --Randy

 

[richhotrain]

gmpullman

Hi, and 

I bought the version II RRampmeter with the test leads and housing ($85)

Although it performs well, I find that I really don't use it all that much. One thing it is handy for is to check track voltage by using an automotive lamp as a ballast load. You can find weaknesses in your feeder wiring this way.

I seldom use it as a current meter since I have four power districts and unless you want to semi-permanantly install them, it is a bit of a pain to place the meter in-line with the load.

So as far as getting accurate readings, sure, it will do the job but once you have that "accurate" information, then what?

So, in my opinion anyway, it is a neat toy but the novelty wears off pretty quickly and your money may be better spent elsewhere.

Just my 2¢

Regards, Ed

 

Ed, I respectfully disagree. It is not a toy.  I own two RRampMeters, one for each of my two boosters.  In line, as I use them, they provide constant voltage and current (amp) readings.  They immediately detect and report problems. Can you operate a DCC layout without them? Sure. Can you spot and resolve problems more easily with them? Absolutely.

Rich