Conversion of Galvanometer to Ammeter

AI Thread Summary
To measure high currents, a galvanometer is connected in parallel with a shunt resistor, allowing most current to bypass the galvanometer while a small portion is measured. This method allows for the calculation of the total current based on the known ratio of current through the galvanometer and shunt. Typically, ammeters are essentially galvanometers with shunts, which can be adjusted for different measurement ranges. The discussion highlights that while the range of an ammeter can be increased by using different shunts, decreasing the range of a specific ammeter is generally not possible. Overall, the use of shunts provides flexibility in measuring various current levels without needing specialized ammeters for each range.
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This is kind of a stupid question but...to measure high currents, a galvanometer is connected parallel to a shunt resistance so that most of the current passes through the shunt resistance but only a small amount of current passes through the galvanometer. But wouldn't this defeat the purpose of measuring a large current? Since only a small current is being measured. :|
 
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Think of it as measuring a known portion of the current. Anyway, you can easily figure out what the large current is from the measurement. When measuring the current in a power line, it is very inconvenient and costly to flow the entire current (at a high voltage) through your meter.

Pretty much all Ammeters are actually galvanometers with a shunt. Or galvanometers connected to coils to measure the magnetic field caused by the current.
 
How would you figure out the larger current? Won't the values of the two be different?

Sorry, I'm a little confused here
 
Say you have a galvanometer with a resistance of 1 ohm. You make your shunt 1 ohm as well. Then half of the current goes each way. Your meter measures half the current, so you multiply it by 2 to get the whole current. Usually the shunt resistance is made smaller so only a tenth, hundredth or thousandth of the current goes through the meter.
 
Oh, I get it now. Thanks!
 
Most welcome! I forgot to mention convenience. When you need a meter to measure current, you don't need to order one specifically for the range required. Any meter will work with the correct shunt. A meter with multiple current ranges just switches in different shunts. Very handy!
 
can the range of an ammeter be decreased ?
@Delphi51 in the above comment you said that we don't need ammeter of a particular range . i comprehend that as by connecting a shunt the range can be increased . but for a given purticular ammeter is there any way that the range might be decreased ... i referred a book which says that the range can never be decreased but one of my mentors says that the range can be increased . HELP
 
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