How to measure current using Ammeter


Current is the measure of the rate of flow of electric charges across the conductor. It is measured in the unit of Ampere. This current is most commonly measured by ammeter.

Ammeter
Ammeter measure the electric current in the circuit. The name is derived from the SI unit of electric current, ampere. To measure electric current in a circuit, ammeter must be connected in series because in series connection, ammeter experiences the same amount of current that flows in the circuit. Ammeter is designed to work with small fraction of volt. So voltage drop must be minimal.

Symbol of Ammeter
The capital A represents the ammeter in the circuit.


How to use an ammeter
Before we start measuring current, we will first set the ammeter range. Keeping the range to highest will prevent the ammeter to blow up its internal fuse. Then set the current type i.e. DC or AC.


Now connect the terminals of ammeter in series of the resistance or load. By this arrangement, ammeter experiences the same amount of current that flows in the circuit. For example let us assume the simple circuit; a bulb is connected to the battery. Positive terminal of battery is connected to positive terminal of lamp and negative terminal of battery is connected to negative terminal of lamp.

Now disconnect any one terminal of the bulb and connect the ammeter in such a way that one probe of ammeter is connected to battery and another probe is connected to bulb.

You can now observe readings in ammeter and that is amount of current flowing in your circuit.

Now once you have noted readings from ammeter disconnect the ammeter and connect the wires as in simple circuit back.

CAUTION:
Do not connect your ammeter’s probes directly to battery to check the current of that battery. This will create a short circuit in the ammeter and sometimes this activity can blow your ammeter’s internal fuse. So please do not perform this activity.

If you want to check current of the battery. Add a resistance across battery and connect an ammeter in series. The readings will be correct and accurate, no need to worry.

Ammeter shunt
When high value of current is passed through ammeter, this damages the internal circuit of ammeter. For this a resistance is connected in parallel to ammeter. So, large amount of current will pass through that resistor. And of course this shunt resistance does not affect the working of ammeter.

So, this is how you should use ammeter with all the precautions and measures. Ammeter has made calculations of current in electrical devices very easy and now with ammeter we can measure small currents in ยตA to large currents in kA.



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