What can an oscilloscope do that a multimeter can’t?

There are plenty of things that an oscilloscope can do that a multimeter can’t. There are also lots of things that a multimeter can do that an oscilloscope can’t.

A multimeter can measure voltages much more accurately than an oscilloscope can. It can also measure current and resistance. An oscilloscope can’t measure either of those. A multimeter is also a lot cheaper than an oscilloscope so what’s all this fuss about oscilloscopes?

It’s not that an oscilloscope is better or worse than a multimeter. It’s the fact that it’s completely different in its uses. Like a bicycle and a car.

Oscilloscopes were developed years ago when technology wasn’t what it was today. We used to have TVs that were huge glass tubes, cathode ray tubes to be exact. Cathode ray tubes were also the items that were used in oscilloscopes. A cathode ray tube works by producing a stream of very fast-moving electrons that collide with the inside of the glass tube. This produces a glow on the phosphorous screen.

It makes a dot. This dot can be pulled across the screen also very quickly so it looks like a line.

Wow, a line on a screen. Stay with me on this, a voltage pulls the dot across the screen to make a line. So what happens if you use another voltage to move the line up or down? Well, this is in essence what an oscilloscope does that a multimeter can’t.

TVs don’t use cathode ray tubes any more and neither do oscilloscopes. They use small digital screens that simulate the actions of an old cathode ray tube but the microprocessors and software that simulate this action also make it able to do other useful things like store screen images and measure frequency accurately.

Uses of an oscilloscope

If you have a circuit that is supposed to be oscillating or producing a square wave, you can connect your multimeter up to the circuit and check that the supply voltage is the correct value and polarity but your multimeter can’t tell you if the circuit is producing a square wave or not.

An oscilloscope will though. Setting the oscilloscope up properly will enable you to not only see that the circuit is oscillating but you will be able to see the shape of the waveform that the circuit is producing. If it was supposed to be a square wave you will be able to see how square it actually is. You can also see how quick the voltage rises and falls and read the frequency of the waveform.

This is the beauty of the oscilloscope. It enables you to see inside the circuit. In the way a stethoscope enables a doctor to hear what’s going on inside your body, an oscilloscope enables you to see what’s happening inside an electronic circuit.

You have to set up an oscilloscope. It has a sort of amplifier on its input that you set. So that, say 100 volts will move the line up or down 5 centimetres or turn up it up so a millivolt will do the same. You also set the same with the speed the dot forms a line, so you can see frequencies of a few hertz up to 100 million hertz.

Using an oscilloscope you can see how smooth the power coming out of a power supply is. You can track down hums from power supplies in circuits. You can see inside a signal going through an amplifier to see if or where it’s clipping.

Finding faults with an oscilloscope

Recently I’ve used an oscilloscope to track down a faulty electrolytic capacitor. This component was causing the left monitor speaker to buzz.

I Found an optoisolator that was slightly out of specification and stopping musical information digital interface (MIDI) signals from operating a synthesizer.

I used an oscilloscope to adjust a couple of preset resistors to properly produce a saw tooth wave on a synthesizer voltage-controlled oscillator (VCO).

Final thoughts on what can an oscilloscope do that a multimeter can’t?

Put at its most basic an oscilloscope really only shows a voltage. It’s the speed and how it shows the voltage and the way it shows it on a screen that makes it so useful. A multimeter shows a voltage more accurately than an oscilloscope but often it’s not the accuracy that you’re trying to see.

If you want to more information about how oscilloscopes work then check out my article “How does an oscilloscope work?” for some more detail.

I also have an article “how to use an oscilloscope” for some help and tips to get you started.

Hopefully, you can now see what can an oscilloscope do that a multimeter can’t.

If you looking to get an oscilloscope then check out my article “Is an oscilloscope worth buying” to help you make up your mind if it is something you need.

If you’ve made up your mind to buy an oscilloscope, then be sure to check out my article “How do I buy an oscilloscope” for some help to avoid making a costly mistake.