I will be installing both a 0-20 volt voltmeter and a 5 amp ammeter.
My question is if there is a short, will it destroy my ammeter?
Is so, is there anything I can install to also protect the ammeter and I guess the everything else from further damage.
I did install a 5 amp resettable electronic circuit breaker.
I have a postwar zw running strictly conventional. Mostly post war and some modern. No tmcc or such.
Since I run conventional, the applied voltages is typically 6-14 volts max.

Thanks

Lou

Original Post
The circuit breaker is from Pepboys and is, I am guessing, automotive in nature.
I think I still have the packaging. I will check later.

The reason for the low current range since I run conventional and have just one engine running at a time. Your are correct, it could be too low of a range.

Lou

If you're running where you are sure you aren't going to exceed 5 amps, I'd just use something like a 6A fast blow fuse, that will protect the train and the ammeter.
You need to consider Dale's question. You should always install an ammeter that has "headroom", that is, the scale of the meter should exceed the maximum amount of short-circuit current that might occur. If the trains draw more than 5 amps, a 5-amp meter is insufficient.

Arthur P. Bloom TCA 86-23906 "I love the smell of smoke pellets in the morning!"

I will definitely reconsider my choice in the ammeter amperage range and the circuit breaker type.

At higher voltages, the circuit breaker does response much quicker if a short is detected. However, at lower voltages, it is very slow to trip. I may consider the fast blow fuses.

Lou

quote:
Originally posted by ldejesus:
I will definitely reconsider my choice in the ammeter amperage range and the circuit breaker type.

At higher voltages, the circuit breaker does response much quicker if a short is detected. However, at lower voltages, it is very slow to trip. I may consider the fast blow fuses.


I Think I'd have the Ammeter in the 0-30 range also and I didn't see any post about it but your measuring A/C Amps. not D/C.

I'm not really certain the automotive circuit breakers will open up like you want them to.Your best bet there is a fuse block with Fast blow fuses.

If you use digital meters and not analog(Has a dial and a pointer) you can probably find them in a range that would be high enough you'd never have to worry about "Peaking" and they look kinda cool when you have the digital volt and ammeters in an inclosure right there at your transformer.

David
I would think that a 0-15 amp ammeter would be the best range.
For one thing if you are running only one train at say 3 amps, that won't hardly get the needle off teh zero peg using a 30 amp meter.
If you were to run 2 or 3 trains pulling a total of say 6-8 amps, your 15 amp meter will be comfortably mid-scale.
If you use a 10 amp fast blow fuse you should be fine for protection.
Depending on what gauge wires you run, how long they are etc, you will lose considerable voltage in your wiring and trackage. This will help to keep the peak surge current your ammeter sees to a minimum in the event of a short.

Rod

We are never too old to learn something stupid....

Thanks for your suggestions. Yes. the first ammeter purchase was DC. Silly me, the packaging did not say ac or dc , just to find it was dc..

If I was running multiple train with command control, yes, I would have opted for a higher amperage. Another reason for my initial low amerage and I agree to what you ae saying, 30 amp range would have hardly moved the needle and what fun it that.

Lou

Sorry about that Lou,
Went back and looked at my MRC 270 Dual and it has the Volt and Ammeters with the pointers(Analog) The Ammeters go from 0-10 Amps. My bad

You'll most likely have to get ammeters from an electronics supply the auto parts stores aren't going to have what you need.

David
I can't imagine a 5A meter being damaged if you have a 6A fast blowing fuse. Dale's experience must be much different than mine, I don't believe this risks any damage to the meter.
I received the ammeters last night. Just a quick test shows I am about 2 amps. Yea, it works, for now.
While I am within range, now I understand maybe not so if there is in fact a short. Hopefully, I wont damage it. Next time, I will try something larger, think headroom.
Next stop, looking to into some fast blow fuses or circuit breakers that are not the thermal type.

Thanks everyone for your suggestions.

Voltmeters should arrive today..

Lou

quote:
Originally posted by ldejesus:
I received the ammeters last night. Just a quick test shows I am about 2 amps. Yea, it works, for now.
While I am within range, now I understand maybe not so if there is in fact a short. Hopefully, I wont damage it. Next time, I will try something larger, think headroom.
Next stop, looking to into some fast blow fuses or circuit breakers that are not the thermal type.

Thanks everyone for your suggestions.

Voltmeters should arrive today..


I like to size a meter to show mid scale at my operating voltage or current.

Chuck TCA LCCA ARRL BMWMOA

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