Measuring loco current draw with DCC

[Blind Bruce]

I have a couple of locos that I suspect are drawing too much current, either binding or wearing out. I have a Fluke 77 DMM but the frequency response on current only goes to 1kHz. Can I put this meter in series with one lead of my Zephyr and read a reasonably accurate current?

[richg1998]

I have a couple of locos that I suspect are drawing too much current, either binding or wearing out. I have a Fluke 77 DMM but the frequency response on current only goes to 1kHz. Can I put this meter in series with one lead of my Zephyr and read a reasonably accurate current?

 

For all I have read, those readings can be iffy. I did a little reading on the Zephyr and the box is powered by 15 volts AC from  a power transformer so you can put your meter in series with either 15 volt 60 Hz AC lead and set the meter to read AC Amps. Use the 20 amp  scale to start out. I think the transformer is good for 3 amps. With nothing on the track, read the current. That is what the Zephyr is using to power itself. Then put a loco on the track and take another reading. Subtract the lower number from the higher number to get an idea of what the loco is drawing. Make sure all the lights are on.

Rich 

[locoi1sa]

  Once again NCE has a feature over Digitrax. The power cab has a built in amp meter that displays instead of the fast clock. 

  Could it be a pickup problem like dirty track and wheels? Maybe some loco maintanance is in order. You said a couple of locos. What make? What model? Steam or diesel? I had a Bachman 2-8-0 that ran tops before it sat on a display shelf. Then I decided to put sound in it and it ran jerky and binding. It turned out to be the drive belt took a set and lost its flexability. Some hot water and some WD40 got it flexing again and she runs just like before the long display stint. If these are Proto 2 axle diesel trucks check for a cracked axle gear.

  Just poking at some other things to check.

      Pete
 

[Vail and Southwestern RR]

Or get a widget made to measure DCC current: 

http://www.tonystrains.com/products/tteexclusive_measure.htm

 

[richg1998]

I built my own and built one for the club I belong to. Compares very well to a commercial one I borrowed. Yes I know, not everyone likes to do SMT soldering but I do well for 68. Just average out the shakes.

 

http://home.cogeco.ca/~rpaisley4/DCCAmmeter.html

Rich 

[Tilden]

 I concur with the rampmeter idea.  I wired one into my track circuit and get a constant readout of power usage.  It allows me to tell at a glance if an engine is "running hot".  It also allows you to see the difference in demand when pulling grades.  Well worth the money.

 Tilden

[CSX Robert]

I have a couple of locos that I suspect are drawing too much current, either binding or wearing out. I have a Fluke 77 DMM but the frequency response on current only goes to 1kHz. Can I put this meter in series with one lead of my Zephyr and read a reasonably accurate current?

There is a simple trick for using an ammeter to measure DCC current. Cut one lead of the output of the command station. Connect the cut lead to the two AC terminals of a bridge rectifier and connect the leads of the ammeter to the '+' and '-' terminals of the bridge rectifier. One thing to note, this will drop the DCC output voltage approximately 1.5 volts.

[loathar]

Couldn't you just check them the old fashioned way with a DC power pack and your meter? Shouldn't that work OK as long as they're not sound locos?