How Oscilloscope Works

An oscilloscope is a device for displaying varying voltage signals graphically, usually in the form of a calibrated diagram of multiple signals. After the waveform is displayed, its properties such as amplitude, frequency and so on can be analyzed. It uses the time-domain method of displaying changes in electrical signals that have passed through it. They are commonly known by different names, including CRO and DSO, which have evolved from measuring voltage changes over time based on events.

An oscilloscope is an essential lab instrument. This instrument is used for measuring voltage, current, frequency, and power. In this blog post we will discuss how oscilloscopes work and what they are used for today.

What is an oscilloscope?

How Oscilloscope Works

In school you probably made charts, and you probably saw them in the newspaper as well. These graphs often illustrate how the value of a quantity over time varies, such as a heart rate, the price of stock, or a nation’s exchange rate. Y-axis represents the quantity plotted vertically, and x-axis represents the period plotted horizontally. If you didn’t have an oscilloscope, you may find that charts like this take a long time to plot. You can feed oscilloscope signals from probes attached to electronic circuits, scientific instruments, or medical monitors to draw charts automatically.

What can we use oscilloscopes for?

It is possible to use an oscilloscope for observing signals in all sorts of ways. In electronics courses, oscilloscopes will be used to monitor the changes in circuit signals over time. They can also be used to troubleshoot TVs, radios, and much more. Coaxial cables are used to connect the probes of a typical oscilloscope to electric currents, but this does not mean oscilloscopes can only measure electricity. You can use an oscilloscope to measure almost anything when you attach a transducer (that converts one type of energy into another). Among the various types of transducers that can be used to study sound signals with an oscilloscope are microphones (which convert sound energy to an electrical signal), thermocouples (which measure temperature changes), or piezoelectric transducers (which generate electricity when squeezed).

What makes oscilloscopes so useful is their ability to visualize and comprehend invisible signals. Ultrasound is above human hearing threshold, so by definition, it cannot be heard by humans. However, if you use an oscilloscope, you can see it easily and study it. The oscilloscope, on the other hand, offers the possibility of seeing and studying sounds in a way that may not otherwise be possible for those with hearing impairments.

How an oscilloscope works

Despite their innumerable similarities, oscilloscopes are almost exactly the same as traditional televisions. Often, oscilloscopes are referred to as cathode-ray oscilloscopes. The back of a TV screen is coated with phosphors that make electron beams scan across it back and forth. The phosphors illuminate when the beam strikes the screen. Electron beams sweep across the screen in less than a blink of an eye and build up the picture you see. Afterwards, it’s the same thing all over again. Once more. Once more. so, Instead of seeing a still picture, you see a moving one.  Oscilloscopes work in much the same way except that the electron beams draw graphs rather than pictures. What you are really seeing when you look at a line on an oscilloscope screen is the wobble of an electron beam!

One thing to keep in mind is that, what appears on your on-screen chart depends on the signals transfer into the x and y connections. Traditional oscilloscopes are analog devices because they correspond one to one with these two things. Alternatively, we could say that the trace on the screen is an analogy of your object of study.

Types of oscilloscopes

CRT and LCD

Cathode-ray tubes (CRT) were used to create oscilloscopes, as we already learned. Its bulk, weight, power usage, unreliability, and cost make it an unattractive investment. The CRT television has been increasingly replaced by LCD technology, which is more convenient. So, CRT oscilloscopes are almost all being replaced with flat-panel LCD screens. As opposed to older oscilloscopes, LCD oscilloscopes draw traces through digital electronics instead of moving electron beams — effectively mimicking what happens when using the older technology. It is generally cheaper and more compact to use LCD oscilloscopes.

The traditional oscilloscope makes use of entirely analog technology. You can feed them signals, and they will display them on the screen in accordance with what you input. The LCD oscilloscope is usually a digital oscilloscope. Analog signals are converted into digital form by analog-to-digital converters, then the numbers are plotted on the screen.

Plugin (USB) oscilloscopes

Computers, tablets, and smartphones already come with CRT or LCD displays, so buying the best usb oscilloscope is no longer necessary for occasional hobby uses. Many companies sell affordable oscilloscopes for mobile devices that plug into USB ports or have equivalent leads. You can use a PC or mobile device as an oscilloscope if you have one of these programs. It’s great to have that option!

How Oscilloscope Works

Analog oscilloscope

Let’s take a look at how analog oscilloscopes work. Here is a block diagram that shows the process easily. Let’s have a look at the diagram and read the full description to know how analog oscilloscope works:

how oscilloscope works

Analog oscilloscope block diagram

Probe:

Your circuit under test is connected to this piece. Oscilloscope measures the difference between two points (voltage) with probes that typically have two tips each.

Amplifier/Attenuator:

It is often necessary to amplify (increase in amplitude) or attenuate (decrease in amplitude) an electrical signal before it can be sensibly displayed to the user or without damaging the oscilloscope’s inner circuitry.

Trigger System:

Triggers determine when the oscilloscope begins displaying waveforms based on a user-defined condition (such as a voltage threshold). It can be extremely useful when finding intermittent pulses in a circuit or when synchronizing the display to regular patterns like sine waves so that the pattern remains steady on screen.

Sweep Generator:

Sweep generators create sawtooth voltage patterns in order to control the horizontal plates in CRTs. With this technique, the beam of light moves from one side of the CRT to the other. The  sweep generator can be set to produce a certain frequency and triggering.

Horizontal Amplifier:

The horizontal amplifier, which can control the horizontal plates in the CRT, is much like what was found after the probe. It enhances the sawtooth wave from the sweep generator to control the amplitude of the horizontal plates.

CRT:

A phosphor-coated screen is illuminated by an electron gun that continuously fires electrons onto it. The beam is deflected by two sets of plates. Using the probe voltage, the vertical plating is controlled directly, and using the sweep generator, the horizontal plating is controlled. A solid line is shown on the screen when the beam rapidly deflects. As the probe voltage varies over time, this line on the display shows it.

Digital Oscilloscope

In the 1980s, Nicolet manufactured the digital oscilloscope (DSO) by utilizing a relatively slow  analog-to-digital converter (ADC). Digital oscilloscopes have become faster, smaller, and more popular as digital technology has advanced.

Digital Signal Processors are essentially sophisticated computers fitted with high-end analog to digital converters. Although there are many similar functions and features to those found on older analog oscilloscopes, there are also some that are new.

Let’s have a look at the diagram and read the full description to know how Digital Oscilloscope works:

how oscilloscope works

Digital Storage Oscilloscope Block Diagram

Probe:

In order to test your circuit you need an oscilloscope that can measure the voltage between two points. The tips of most probes are attached to different nodes on your circuit.

Amplifier/Attenuator:

In oscilloscopes, electrical signals are amplified or attenuated by circuits. This will allow for an effective display and will prevent damage to internal components.

Trigger Select:

Most oscilloscopes can display waveforms triggered by either an internal or external signal (from another source).

Control Logic:

An opportunity for a user to adjust signal capture and display logic. Analog oscilloscopes have horizontal controls that are analogous to the controls on the control panel, but they offer more options.

ADC:

A sampling rate is determined by the control logic of the analog-to-digital converter. Binary numbers are created from these samples and then stored in memory.

Memory:

In memory, sampled signals are represented by digital data. Using this information, a graph representing a close approximation of the original electric signal can be generated.

Time Base:

The horizontal axis on the display is controlled by the time base as set by the control logic. The  user can adjust the time base based on a single trigger point to capture sporadic signals or to hold periodic signals, such as sine waves, steady on the display during a period.

Display:

An oscilloscope displays waveforms on a screen by combining memories with time bases and displaying waveforms from memory. Waveform in which voltage and time are represented as Y-axis and X-axis, respectively, often represents the sampled signal. In older DSOs, CRT displays are used as displays, but most modern DSOs use LCDs.

The Evolution of Oscilloscopes

The oscilloscope has evolved into a smarter, more powerful piece of test equipment since their invention. PC-based oscilloscopes are highly portable and analyze and display waveforms with the processing power of a computer. A digital phosphor oscilloscope (DPO) can display a signal’s frequency-of-occurrence in a manner that mimics an analog oscilloscope.

Logic analyzers specialize in displaying digital signals, which are made possible by oscilloscopes. The mixed signals oscilloscope (MSO) is the result of combining these two powerful instruments. Analog signals can be displayed on MSOs just like oscilloscopes, while digital signals can be analyzed like logic analyzers.

FAQ

What is the working principle of oscilloscope?

Voltage can be measured with an oscilloscope. During this process, a small current is drawn in order to measure the voltage drop across a resistor. Using an electric field, the voltage drop amplifies and deflects the electron beam either in the X (horizontal) or Y (vertical) axis.

What is the purpose of an oscilloscope?

With an oscilloscope (or scope), voltage signals are tested and represented as waveforms. Graphs are used to show the change in signals.

What are the major components of oscilloscope?

Oscilloscopes have three main parts – the horizontal system, the vertical system, and the trigger system. The oscilloscope is able to reconstruct signals accurately based on the contribution each system makes. Oscilloscopes have three distinct front panels branded  Vertical, Horizontal, and Trigger.

Is an oscilloscope necessary?

It is true that oscilloscopes are primarily used for measuring electrical waveforms. Furthermore, it also has a pretty high degree of accuracy for measuring mostly constant voltage levels. Moreover, it can detect small fluctuations in battery power, which is not possible with most multimeters.

Why are oscilloscopes so expensive?

The oscilloscope is a precision instrument. To ensure they meet standards, they must undergo strict quality control. As a result, costs continue to rise. In addition, higher bandwidth means higher costs.

Conclusion

It only took a few decades for the oscilloscope to evolve from its early days as an analog instrument that could do very little more than display voltage and frequency, into a sophisticated device with PC-based capabilities. These modern devices can process waveforms at speeds of up to 300MHz, which is much higher than any analog scope ever created.

There are even digital phosphor oscilloscopes (DPOs) on the market today that mimic the appearance of their predecessors but have all of this power behind them. If you want to learn more about how these instruments work or what types exist, let us know!

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