Meters ?

[#94]

I have a MRC Control Master 20 and would like amp and volt meters to hook up. Where should I look for these? How can these be best used to diagnose troubles ?

Thank you,
Allen

[Yampa Bob]

Hi Allen,

Please refer to my thread just below yours: 

http://www.bachmanntrains.com/home-usa/board/index.php/topic,6984.0.html

"Bachmann loco current tests":

http://www.bachmanntrains.com/home-usa/board/index.php/topic,6229.0.html

Suggest bookmarking the threads for future reference.

The best reference for wiring and testing is "Easy Model Railroad Wiring" Second Edition by Andy Sperandeo, Kalmbach #12207, ISBN 978-0-89024-349-7.  At about $18, it is a must have.  Chapter 12, "In case of trouble", has lots of information about using analog and digital meters.

Andy's approach is: "I'm not especially interested in electronics, I just like to run trains".  No boring theory, lots of great pictures and clear diagrams.

If you have specific questions after digesting all of this, feel free to ask. 

Bob

[#94]

Thank you very much Mr. Bob, you are very helpfull. Now where might I find gauges to hardwire to the Control Master 20? I spent some time searching and found nothing, not even at Radio Shack. Strange that MRC does not list these as an option/ add on. The more I learn about electronics the more fun (less confusing) it all is.

Thanks,
Allen

[Tom McDonald]

Allen,

Micromark sells flush mounted ammeters and voltmeters.
Here is the link/

http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=82146

Tom

[Yampa Bob]

I just found the link for the meters I use. Ask for "Lee" in sales.  At half price, grab a couple of them.

http://www.multimeterwarehouse.com/dt830bf.htm

[renniks]

     Bob,

      These are no good for Allens permanent connection needs.

           Note: When you measure current, Do Not keep the meter over 15 seconds in the circuit.

     Eric UK

[JerryB]

I just found the link for the meters I use. Ask for "Lee" in sales.  At half price, grab a couple of them.

http://www.multimeterwarehouse.com/dt830bf.htm

Bob, All:

Using a handheld DVM as a permanently installed meter will just result in a lot of problems. First of all, it requires that the meter be turned on and off, and the range selected in order to use it. Leave it on and you will have to replace the battery in the near future. Handheld DVMs require that you re-connect them (using the current terminals) and reset the range for current measurements. That requires that you interrupt the operating circuit. Accidently leaving them in current mode while trying to measure voltage will usually blow an internal fuse and / or destroy the current measuring circuitry.

The link you provided is to a very cheap DVM. Note the caution to only use it in current mode for 15 seconds! Not a very satisfactory solution, even for a cheap handheld. These meters would be considered throwaways, and probably not worth even the very low price. IMHO, this meter is junk. As usual, your mileage may vary.

I believe Allen is looking for panel meters to permanently install. The Micromark ones are good, espeically for H0 trains. If those aren't satisfactory, Googling "dc panel meter" produces something around 385,000 hits. About 1/3 of those hits will lead directly to an absolutely astounding array of analog and digital meters suitable for every variety of model RR application.

Happy RRing,

Jerry

[Yampa Bob]

I posted the link for the benefit of anyone wanting an inexpensive option to troubleshoot or monitor their trains. Whether or not Allen considers them appropriate for his application is his decision.

I have 2 of the meters mounted on an easel with switches, much easier than building a cabinet or console, cutting holes, etc. One meter is set on the 20 volt range, the other set for the 10 amp range but with an inline fuse for extra protection.

[#94]

Thank you all. There is plenty to interpret here and all of it should be helpfull.

Thank you,
Allen

[Jim Banner]

Personally, I don't see the problem of using these low cost Digital Multi-Meters (DMMs) in permanent installations.  They may be a little bit like using a sledge hammer to swat flies but in the end, the flies are just as dead.  And if you can buy sledge hammers cheaper than fly swatters ...

The only problem with permanent installation might be supplying batteries but there are all kinds of 9 volt battery eliminators available.  Just don't out cheap yourself by trying to use one battery eliminator to power more than one DMM.  If you were to use one as an ammeter and the other as a voltmeter, there would be two common connections, one through the power supply being monitored and the other through the power supply keeping them working.  This would probably blow the chips out of at least one of the DMMs.  With separate battery eliminators, there is no power supply common as the DMMs are isolated from each other by the transformers in the eliminators.

Biggest advantage of using a couple of DVMs is their resistance to voltage overload.  If you are worried about the 15 second maximum on the 10 amp scale, you can avoid overheating the pass resistor by using an external 0.1 ohm, 10 watt resistor with the DMM, set for the 1 or 2 volt scale, connected across it.  Fresh out of 0.1 ohm resistors?  Use about a 5'-4" length of #12 copper wire wound into an open coil to form a 0.01 ohm resistor and set the DMM for its 100 or 200 millivolt range.  Use a felt pen to permanently insert a decimal point at the proper location.  Remembering that a reading of 100 millivolts indicates 10.0 amps makes this easy.

Jerry, you seemed to be concerned about the quality/life expectancy of these cheap Digital Multi-Meters.  Some years ago, I had the use of a precision dc voltage calibrator, traceable to N.I.S.T.   I checked the dc voltage scale on several of these el cheapo DMMs and found they consistently outperformed their specified accuracies.  At the time, I also calibrated a much more expensive DMM which I use as my personal standard.  My tests have shown that my own cheap DMMs are still within specs some 15 years on.  This after being dropped, overloaded, left in hot vehicles, left out in the freezing cold, and generally used, misused, and abused.  Why we could buy such good DMMs for such low prices was a mystery until I thought about calculators.  My first scientific calculator was an HP45 and cost about $500 CAD.  My latest is a brand X and cost about $5.  They do about the same thing (although I do miss the Reverse Polish Notation of the HP.)  So maybe it isn't surprising that DMM performance that once cost about $1000 is now available for about $10.  This leaves me wondering if my "much more expensive DMM which I use as my personal standard" is really any better than the el cheapos, except maybe for having one extra digit.