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If you've ever seen a graph that shows the ups and downs of an electric current over time, you might wonder how it was made. Well, the answer is an oscilloscope. This cool piece of equipment is the only way to record the data needed to create this kind of graph. Not only that, but it can also help us analyze all kinds of waves, like sound waves, too! We just need to make sure we convert the signals into a format that the oscilloscope can understand. So, next time you see one of those cool graphs, you'll know exactly how it was made - with an oscilloscope!

Definition of oscilloscope

To get started with understanding oscilloscopes, we first need to know what they are and how they work. put, an oscilloscope is a tool that helps us measure how an electronic signal changes over time. It does this by taking a signal from a power source or circuit component and showing it on a screen. This screen can measure both voltages and times using a waveform. So, if you want to see how a signal changes over time, an oscilloscope is the tool you need!

Types of oscilloscopes

There are two main types of the oscilloscope; a digital oscilloscope or digital storage oscilloscope (DSO) and a cathode-ray oscilloscope (CRO). They both have the same function but carry it out in different ways.

Cathode Ray Oscilloscope (CRO)

The cathode ray oscilloscope makes use of a cathode ray tube which fires electrons onto the screen of the oscilloscope. The screen is coated with phosphorus that is excited when electrons are incident upon it and releases energy in the form of light which we observe as a bright dot on the screen. If a signal is passed through the CRO (AC voltage, for example), then the electron beam from the cathode moves relative to imposed electric and magnetic fields. An electric field is a region in space where a charged particle will feel a force, and a magnetic field is a region in space where a moving charge or permanent magnet feels a force. The electrons are then deflected by the electric and magnetic fields in a region between two deflecting plates. The moving electrons strike the screen at different points and hence a pattern representing the voltage will be created (it would be sinusoidal in the case of AC). Any adjustments to the input voltage or frequency will change the strength of the applied fields, creating a different waveform on the screen. The waveform can be used to make direct measurements of voltage (), frequency (), period () and other electrical quantities. The figure below is an example of a cathode ray oscilloscope.

An image of a typical cathode ray oscilloscope (CRO) with a signal represented on the phosphor-coated screen on the left. On the right-hand side is the controls that allow adjustment of the scale of the image, Pxhere.

Digital Storage Oscilloscope (DSO)

Compared to the cathode ray oscilloscope, the digital storage oscilloscope is the more modern type of oscilloscope. It takes an analogue signal as input and uses sophisticated signal-processing software to convert it into a digital signal. This digital signal can be stored in memory and converted into a digital image that can be viewed on an LCD screen, without the need for deflecting plates, electric fields, or magnetic fields. The DSO can also be connected to a printer to obtain a print-out of any signal stored in memory, or the image could even be stored on a USB drive. Like the CRO, the waveform in the DSO can be used to make measurements of voltage, frequency, period, and other electrical quantities. The image below shows a typical DSO.

An image of a modern digital storage oscilloscope with a signal displayed on an LCD screen.

These oscilloscopes are slowly replacing the typical CROs due to their ability to store and transfer data


Uses of the oscilloscope

Testing Circuits

While the oscilloscope is often used in schools to demonstrate the sinusoidal behavior of alternating currents, it has a more practical use in testing electric circuits. An oscilloscope can be used to determine the location of a fault or to test the currents in and out of different points in a circuit. This is done by using the oscilloscope to measure the peak voltage, period, frequency, and other electric quantities of an AC power source. Alternating current (AC) is produced when an electric current (electrons) oscillates back and forth in a circuit, but the energy still flows in one direction. The illustration below shows what the display on an oscilloscope looks like. The divisions on the screen serve as equal intervals on a graph, allowing the voltage to be measured. The line shown on the screen represents a typical sinusoidal/alternating voltage, and the divisions on the screen can be used to measure that voltage at different times.

Electrocardiograms (ECGs)

Aside from electric circuits, oscilloscopes can also be used to measure the tiny electric currents produced by our bodies. In hospitals, electrodes of an electrocardiogram (ECG) are connected to patients to monitor the frequency of their heartbeats. Each heartbeat produces a small but measurable current that can be detected by a digital oscilloscope. The waveform is created by measuring the tiny voltages across the heart during each heartbeat, and the doctor can read a real-time graph of voltage vs. time. The separation between the voltage peaks is a measurement of the frequency of heartbeats. ECGs can also be used as a tool to predict possible future problems with the heart. Unlike sinusoidal graphs, ECGs do not produce a regular pattern due to the relaxation time in between beats and the complex signal of each heartbeat, as depicted in the figure below.

Sound Waves

Sound waves are created by vibrating air molecules and do not require an electric current to form. However, sound wave properties can be measured using an oscilloscope. An audio signal can be converted via a transducer to an electrical signal (a series of voltages) that the oscilloscope can decode and represent on the screen. A transducer is an electrical component that can convert energy from one form to another.

Both CROs and digital oscilloscopes can be used to decode and represent sound waves. The oscilloscope can measure the amplitude, frequency, and period of a sound wave. The figure below shows a setup consisting of a sound-wave generator that creates sound waves transmitted via a speaker and detected by an oscilloscope, which gives a visual representation of the sound waves.

A setup that includes a sound-wave generator creating sound waves emitted by a speaker and represented on-screen by an oscilloscope
A setup that includes a sound-wave generator creating sound waves emitted by a speaker and represented on-screen by an oscilloscope

Oscilloscope example and graph

The peak voltage of the AC signal can be calculated by first determining the peak-to-peak voltage. This is done by measuring the number of divisions from the highest to the lowest point on the oscilloscope graph and multiplying this by the volts-per-division setting. In this example, there are four divisions between the highest and lowest points on the oscilloscope graph, and the volts-per-division setting is 5V. Therefore, the peak-to-peak voltage is 4 x 5V = 20V. The peak voltage is then half this value, which is 10V.

Oscilloscope - Key takeaways

An oscilloscope is a useful device that measures the variation of an electronic signal with time, displaying the signal on a screen as a waveform. This waveform can help measure the voltage, frequency, and period of the signal, making it a valuable tool for analyzing electronic signals.

There are two main types of oscilloscopes: the digital storage oscilloscope (DSO) and the cathode-ray oscilloscope (CRO). The CRO uses a cathode ray tube to display the waveform on the screen, while the DSO converts an analogue signal into a digital one, allowing it to store an image of the waveform.

Oscilloscopes are commonly used to test for currents in a circuit or to locate faults, making them valuable tools for engineers and technicians. They are also used to measure heartbeat frequency in electrocardiograms (ECGs) and to measure sound wave properties using a transducer. The amplitude, period, and frequency of a sound wave can be determined with the help of an oscilloscope.

When using an oscilloscope, it is important to note that the screens do not have axes, so the voltage sensitivity (volts-per-division) must be read. To calculate the peak voltage of a signal, the number of divisions from the lowest to the highest point of the graph can be multiplied by the voltage sensitivity to get the peak-to-peak voltage. The peak-to-peak voltage divided by two is the peak voltage of the signal.


What is an oscilloscope? 

An oscilloscope is a device used to measure the variation of an electronic signal with time.

What does an oscilloscope show? 

Oscilloscopes take a time-varying input signal from a power source or circuit component and display the signal on a screen that can measure voltages and times.

What does an oscilloscope measure? 

The oscilloscope waveform can be used to make direct measurements of the voltage, frequency and period of an input signal.

What is an example of oscilloscope? 

Cathode ray oscilloscopes (CRO) and digital storage oscilloscopes (DSO) are two examples of oscilloscopes.

What are the types of oscilloscope? 

Cathode ray oscilloscopes (CRO) and digital storage oscilloscopes (DSO) are two types of oscilloscopes.

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