Measuring with a Multimeter

 

The multimeter, or multitester, is an electronic measuring instrument that can be used to measure or test electrical/electronic components and circuits. It is mainly used to find out voltage, current and resistance values.

Connecting Up

The meter's red and black test probes will need to be connected to your circuit or components as shown below. When measuring voltages and currents, the red (+) probe should be placed at the tip of the arrows, as shown in the circuit diagrams below right.

 


To Measure Voltage:

To measure the voltage (or potential difference) across the lamp shown on the right:

Place the meter's black (negative) probe towards the negative (-) side of the power supply (bottom of the arrow).

Place the meter's red (positive) probe on the other side of the lamp towards the positive (+) side of the power supply (tip of the arrow).

The meter is now connected in parallel with the lamp.

No voltage reading will be seen on the meter display screen until the circuit switch has been closed. Current will then flow through the lamp and a potential difference created across it. See where the mutimeter selector switch needs to be positioned.


To Measure Current:

To measure the current flowing through the resistor shown on the right:

Place the meter's black (negative) probe towards the positive (+) side of the power source (bottom of the arrow).

Place the red (positive) probe towards the resistor (tip of the arrow).

The multimeter is now in series with the resistor.

The current measured in the connecting wire is the same as the current flowing through the resistor. See where the mutimeter selector switch needs to be positioned.


To Measure Resistance:

Before you can measure the resistance value of a resistor in a circuit, you will usually have to remove it and test it in isolation. When measuring the value of resistors, it does not matter which way the (+) and (-) meter probes are connected. See where the mutimeter selector switch needs to be positioned.