# Ammeters



## Patrick1544 (Apr 27, 2013)

Starting to buy my electrical components and I have a question. How do I know if an analog ammeter has a shunt resistor built in, or if I need to install a shunt resistor. How would I know which value to use.

Looking at these meters:

http://www.led-switch.com/Panel Meters.htm


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## gunrunnerjohn (Nov 10, 2010)

They should specify if you need a shunt. I suspect those already have it internally.


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## Patrick1544 (Apr 27, 2013)

I'm hoping they do. I emailed them but no reply. I think that they don't know, themselves. The price is right, though.


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## tr1 (Mar 9, 2013)

*Algebraic equations*

"am meters," for future reference, are really called "amp" meters. "Amp" refers to amperage or current. It's probably good to look up "ohm's law". "Ohms law" is a mathematical algebraic equation hat is used to figure out or(determine) a missing variable. That being current(I),
resistance(R) And voltage(v).
If my memory serves me correctly. 
You can Google this also Good luck,tr1


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## carinofranco (Aug 1, 2012)

tr1 said:


> "am meters," for future reference, are really called "amp" meters. "Amp" refers to amperage or current. It's probably good to look up "ohm's law". "Ohms law" is a mathematical algebraic equation hat is used to figure out or(determine) a missing variable. That being current(I),
> resistance(R) And voltage(v).
> If my memory serves me correctly.
> You can Google this also Good luck,tr1


yup, but it is too hard for me to say "amp meter"


Sent from my iPad using Tapatalk HD


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## Bwells (Mar 30, 2014)

Ammeter
From Wikipedia, the free encyclopedia
"Amperemeter" redirects here. For the unit of measurement, see Ampere-meter.






An ammeter is a measuring instrument used to measure the electric current in a circuit. Electric currents are measured in amperes (A), hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters.


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## tr1 (Mar 9, 2013)

*ohms law*

I stand corrected,
thank you.
tr1


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## Bwells (Mar 30, 2014)

Patrick: which one were you thinking of, the 0-5? How about a digital one, way more precise, no interpolation required between "maybe 3.5 or 3.7"
http://www.amazon.com/beesclover-Di...+ammeter&pebp=1422672806663&peasin=B00C7MJ5LE

Edit: I just looked again and it says it needs an external shunt but I have no idea what that is. I guess off to goggle I go!


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## Patrick1544 (Apr 27, 2013)

Was thinking of 0-10 Amps for the meter.


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## rkenney (Aug 10, 2013)

Bwells said:


> How about a digital one, way more precise, no interpolation required between "maybe 3.5 or 3.7"


Accuracy and resolution are two different things. A digital meter can have a high degree of resolution and still be 'out to lunch' for the actual measurement.

Analog gauges have that way cool 'retro' look and can also be highly accurate.

Great precision is not required for model trains.:smokin:


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