Help!!! The book that came with the multi meter does not have much in it. How do I use it? What settings do I use to check track voltage? What setting do I use to check amp draw for decoder usage? How many volts does the bachmann dcc put out without the 5 amp booster, how many amps does it put out? I will need a base reading I guess right?
Thanks for your help.
mike
Well…
With a DCC system a multimeter is useful, but doesn’t always give you the answer you expect.
To check track voltage on a DCC layout, select the AC setting, and probe across the rails. The number won’t be “right” because the meter is calibrated expecting AC to be a sine wave, but you should at least get a reading, if there is power to the rails, of something between 10 and 15 Volts. So it can tell you that there is voltage there.
You need to be realy careful trying to measure current, a lot of meters on measure fairly small currents, and you will blow a fuse if you try to measure more. Or if you put the probes across the voltage source, and create a short through the meter, for that matter. To measure current the meter needs to be in series with the circuit, which means you have to break the circuit, and insert the meter.
Tony’s Trains sells a product called a RRampMeter, which is a much better tool for taking DCC measurements.
A DCC system with a 5A booster can put out up to 5A. The amount of current (Amps) is dependent on how much is being drawn, not on the supply, up to that limit. In other words, with no locos on the rails, the draw will be zero, each operating loco could add a quarter of an amp, or so, often quite a bit less.
The most useful function of the multimeter is the Ohmeter function, which you can use to check for shorts, and continuity. With the booster disconnected, you can make sure everthing that is supposed to be connected is, and everything that isn’t supposed to be connected isn’t.
Don’t panic. The answers is on the Internet.
We can lead you by the hand but looking at the links below will tell you a lot more. Some of the links are for model railroad users. Store the links in your Favorites folder for yourself and to send to others when you see the same question. Get yourself some double clip leads. They will be a great help. Radio Shack use to sell double clip leads.
Rich
Thanks for the links. I poked around for a while but still have not come up with a reason to what I saw today. I tested an engine after the decoder was in. The engine was stopped with wheels spinning and I got readings from .2 to 3.2 and it bounced all around. Also I tested the rails from the bachman unit and got 17 volts on the rails. Does this sound right?
The Ammeter function is for testing a motor’s current draw BEFORE a decoder is installed so you will know if the decoder you have can handle the load.
Seventeen volts sounds too high – I always get a measure of 14 to 14.5 volts AC from an NCE Power Pro DCC system. That is the NMRA Standard for DCC track voltage, but what you measure depends to a large degree on the accuracy of your meter.
Seventeen volts is a wee bit high, but still acceptable in HO. It may be that the meter is reading high, in any case. I have run my layout on 19 volts by mistake, and have no troubles to show for it.
-Crandell
Thanks Guys I will take the decoder off the motor and try the reading again.
Is there a problem you are trying to solve?
If it ain’t broke, don’t fix it!
Yea there is a slight problem. See the other post I have on Ihc decoder issue from a couple days ago.
I see. I’d be pretty surprised if that motor is drawing too much current. Turning off the BEMF function can’t hurt. I think I’d look really carefully for either a loose connection, or possibly something binding when you put the decoder in place. I’d look carefully at how the wires are routed, and make sure nothing is possibly interfering. If it isn’t too difficult, I’d be tempted to take the motor out, and hook it to the decoder, clip the decoder to the rails, and see how it performs without all the mechanical extras.
Ok so here is todays update.
First off I put the train casis and tender on the tracks and turned the power on (decoder in) Nothing happended. After 10minutes of turning the motor by hand and sliding the train down the tracks i finally got it to run. But after 2 reverses in direction it quit again.
Next I unsoldered the motor lead wires from the decoder off the motor. Next I hooked up the power to the motor and off it went. Switched directions continously for 10 minutes with no problems. I crawled the engine with no problem and it was smooth as can be. This is how it ran before I attempted the decoder install. There is no binding no, scraping no undue noise except the dcc squeal.
Next with the power hooked up I tried to test the amp draw on the motor. The engine was stationary and the wheels were spinning but I got 0 for a reading. I used the volts(left side of the meter on 20) and I also used amp on the right side of the meter and got 0 as well. I put the red lead on the track rail and the black lead on the opposite track lead. What did I do wrong?
mike
To measure amps the meter has to be in series with the motor. Connect one motor lead to the power source. Connect the other motor lead to one of the meter leads, connect the other meter lead to the other side of the power source. Make sure the meter is set ot the amps range, and if it’s like most low cost meters, the one lead should be in the ground hole and the other lead in the one marked for amps (not milliamps, you’ll overload the meter instantly). My $2.99 Harbor Freight specials have that hole marked at 10A, it can read up to 10 amps (not that I’d really want to put that much current through the cheap probes).
–Randy
Ahh haa now I see the error of my ways. Thanks Randy I will try that tomorrow morning.
What brand of loco did you put the decoder in? Did you make sure the motor was totally isolated from track voltage?
Some older engines have the motor directly on the chassis with one leg common to the track. If this is the case then you’ll have problems. The motor must be totally isolated.
Good Luck