How to Measure Current in a Circuit

Electrical current is the amount of electron flow through a circuit over a given period of time. It is measured in amperes, which is defined as the current required to produce a force of 2 x 10^-7 newtons under ideal circumstances between a pair of conductors about 3 feet apart. The following steps will show how to measure current in a circuit.

Difficulty: Moderately Challenging

Instructions

1. Turn the power off on the circuit you are trying to measure. This is essential because an ammeter must be part of the circuit for which it is measuring current.

2. Identify the point in the circuit you wish to measure current through and disconnect the circuit at that point, keeping the two ends from contacting any other part of the circuit.

3. Connect one probe of the ammeter with each end of the open circuit to ensure the entire current will be measured.

4. Check the polarity on your ammeter's connections. If the needle on a manual ammeter moves to the left or the display on a digital ammeter is negative, reverse the ammeter's connections.

5. Continue to adjust the selector switch for the ammeter downward until you get the maximum response from the meter that does not go out of range. Check this range setting and the meter reading to get the correct amperage. For example, if you are using the 0.1 to 1 range on the ammeter and the reading is 6, then the current is 0.6 amperes.

Resources

• More about building electronic circuits at Geofex