For measuring large current a low meter range is used with a shunt, which is a have a wire connected across the meter terminals to carry most of the current.this shunt allowed only a small part of the current to actually flow through the meter coil. usually, 0-1 milliampere meter to use properly sized shunt across the terminals to achieve the desired range.  

You have seen that you have can change the range of ammeters by the use of shunts. the range will vary according to the resistive values of the shunts. ammeters was remade with a number of internal shunts, and a switching arrangement that is used to parallel different shunts across the meter movement to measure different currents. thus a single meter movement can be used a multi-range ammeter.   

A scale for each range is painted on the meter face. the diagram shows multi-range ammeters with a 0-10,0-20,0-100,0-1000 ampere range. 

Note:- the three scales on the meter face. 

When a multi-range ammeter is used to measure unknown current, the highest range is always used first, then next the highest meter range is used, so on until the needle is about mid-scale.in this way you can be assured that the current is not excessive the meter range, and you will never have the unfortunate experience of burning out a meter movement, or of wrapping the needle around the stoppage.

Some multimeters are used external shunt and do away with a normal shunt, and the switching arrangements. changing for such a meter involves shunting it will be an appropriate shunt. the diagram of ammeters is calibrated to read 30-ampere full range by shunting it with the 30- ampere shunt.

review of meter movement:-

It is very possible that you never need to repair a meter but, in order to properly used and care for meters, you need to know how a meter work. suppose you review what you have studied. 

Meter coil:-

consists

Meter movement:-

 A current measuring instrument consisting of a moving coil suspended between the horseshoe's magnet. current in the coil caused the coil to turn. 

Basic ammeter movement:-

0-1 ma. milliammeter movement with the shunt wire across the meter terminals to increase the meter scale range.

Multi-range ammeter:-

A single meter movement is used for measuring different current ranges. each ring required a different shunt. the shunts may be inside the meter movement and controlled by a switching arrangement they may be external, in which case they are connected in parallel with the meter binding posts.