# How to scale a micro ammeter?

I need to measure the current of a Tesla coils secondary output and have found that it is under 1mA and above 50uA so how can I scale a 50uA DC micro ammeter or a DC milliammeter (can't remember its range) to the appropriate range?

rickharris5 years ago

This should answer your question - you will need to shunt some of the current round the ammeter mechanism.
5 years ago
Ya know, "This" , is very good to have around as a refrence so I copied it.

iceng5 years ago
You can always use a resistor and Steve's favorite tool a scope
even a mili-voltmetre.... and math.

Alos, a pick axe and rope can help you scale the difficult domains :-)

A
steveastrouk5 years ago
The meter SHOULD specify its resistance. With that, you can work out the shunting resistance you need.

I = Imeter x Gmeter + Ishunt x Gshunt

I is the total current flowing.
Imeter is the current in the meter.
Gmeter = 1/Rmeter
Ishunt= current to flow in shunt = I-Imeter
Gshunt= 1/Rshunt.
Rearrange for Gshunt.

Steve