How A Multimeter Works

video transcript:

Hi I’m Lee from Ransom Spares. I’m going to be talking about how you can use a multimeter to test and diagnose faults with components inside your electrical appliances. Repairing common faults on domestic appliances is usually well within the capabilities of most DIYers and by using a common sense approach and a process of elimination we can often very quickly narrow down the problem to just a few components. Once we have an idea of where the problem lies we can often go further and test the component with a multimeter to prove if it has indeed failed or not. Whilst multimeters vary in depending on brand the fundamental settings are exactly the same. The first thing to note is that testing on electrical domestic appliances should only ever be done when the appliance is disconnected from the mains. We should never carry out tests with a multimeter on live appliances. There is absolutely no requirement to do this. For that reason we are only interested in one setting on the multimeter which is the resistance setting.

On our multimeter the resistance settings are these green settings here. With the multimeter turned on I will use the 2000 ohm setting as this has an audible alarm when a continuous circuit is made.

So, how do we use the meter to see if a component is faulty or not? To demonstrate I’m going to use this electric cable and plug. We know that each one of these wires is connected to one of the metal bars on the plug and should be a continuous circuit. If one of the wires in the cable was broken then the power lead wouldn’t work. We can use our multimeter to confirm that the circuit in the cable is working and that electricity can flow through as follows:

By touching one lead on the earth wire and the other lead on the earth bar of the plug we can see and hear that we have a continuous circuit. Now we can do the same with the neutral and the live.

In this instance we have proven that there is a continuous circuit for electricity to flow. If the cable was damaged or faulty then the circuit would be broken, there would be no reading on the meter, and therefore the cable wouldn’t work. So that’s how we can use a multimeter to test for faults on electrical components. Check out our DIY repair videos on how to test specific components with a multimeter.  Thanks for watching.

By Lee Gilbert