What is Digital Storage Oscilloscope : Working & Its Applications

In 1897, Karl Ferdinand Brawn invented an oscilloscope. We know about the cathode ray oscilloscope which is used for the display and analysis of different types of waveforms of electronic signals in the electronics and electrical circuits. The DSO is also one type of oscilloscope, used to display the waveform, but the difference between CRO and DSO is that in DSO, the digital signal is converted into analog and that analog signal will be displayed on the screen of the digital storage oscilloscope. In the conventional CRO, there is no procedure for the storage of the waveform but in DSO,  there is a digital memory that is going to store the digital copy of the waveform. A brief explanation about DSO is explained below.

What is Digital Storage Oscilloscope?

Definition: The digital storage oscilloscope is an instrument which gives the storage of a digital waveform or the digital copy of the waveform. It allows us to store the signal or the waveform in the digital format, and in the digital memory also it allows us to do the digital signal processing techniques over that signal. The maximum frequency measured on the digital signal oscilloscope depends upon two things they are: sampling rate of the scope and the nature of the converter. The traces in DSO are bright, highly defined, and displayed within seconds.

Block Diagram of Digital Storage Oscilloscope

The block diagram of the digital storage oscilloscope consists of an amplifier, digitizer, memory, analyzer circuitry. Waveform reconstruction, vertical plates, horizontal plates, cathode ray tube (CRT), horizontal amplifier, time base circuitry, trigger, and clock. The block diagram of the digital storage oscilloscope is shown in the below figure.

As seen in the above figure, at first digital storage oscilloscope digitizes the analog input signal, then the analog input signal is amplified by amplifier if it has any weak signal. After amplification, the signal is digitized by the digitizer and that digitized signal stores in memory. The analyzer circuit process the digital signal after that the waveform is reconstructed (again the digital signal is converted into an analog form) and then that signal is applied to vertical plates of the cathode ray tube (CRT).

The cathode ray tube has two inputs they are vertical input and horizontal input. The vertical input signal is the ‘Y’ axis and the horizontal input signal is the ‘X’ axis. The time base circuit is triggered by the trigger and clock input signal, so it is going to generate the time base signal which is a ramp signal. Then the ramp signal is amplified by the horizontal amplifier, and this horizontal amplifier will provide input to the horizontal plate. On the CRT screen, we will get the waveform of the input signal versus time.

The digitizing occurs by taking a sample of the input waveform at periodic intervals. At the periodic time interval means, when half of the time cycle is completed then we are taking the samples of the signal. The process of digitizing or sampling should follow the sampling theorem. The sampling theorem says that the rate at which the samples are taken should be greater than twice the highest frequency present in the input signal. When the analog signal is not properly converted into digital then there occurs an aliasing effect.

When the analog signal is properly converted into digital then the resolution of the A/D converter will be decreased. When the input signals stored in analog store registers can be read out at a much slower rate by the A/D converter, then the digital output of the A/D converter stored in the digital store, and it allows operation up to 100 mega samples per second. This is the working principle of a digital storage oscilloscope.

DSO Operation Modes

The digital storage oscilloscope works in three modes of operations they are roll mode, store mode, and hold or save mode.

Roll Mode: In roll mode, very fast varying signals are displayed on the display screen.

Store Mode: In the store mode the signals stores in memory.

Hold or Save Mode: In hold or save mode, some part of the signal will hold for some time and then they will be stored in memory.

These are the three modes of digital storage oscilloscope operation.

Waveform Reconstruction

There are two types of waveform reconstructions they are linear interpolation and sinusoidal interpolation.

Linear Interpolation: In linear interpolation, the dots are joined by a straight line.

Sinusoidal Interpolation: In sinusoidal interpolation, the dots are joined by a sine wave.

Difference Between Digital Storage Oscilloscope and Conventional Storage Oscilloscope

The difference between DSO and the conventional storage oscilloscope or analog storage oscilloscope (ASO) is shown in the below table.

Digital Storage Oscilloscope Products

The different type of digital storage oscilloscope products is shown in below table

Applications

The applications of the DSO are

• It checks faulty components in circuits
• Used in the medical field
• Used to measure capacitor, inductance, time interval between signals, frequency and time period
• Used to observe transistors and diodes V-I characteristics
• Used to analyze TV waveforms
• Used in video and audio recording equipment’s
• Used in designing
• Used in the research field
• For comparison purpose, it displays 3D figure or multiple waveforms
• It is widely used an oscilloscope

Advantages

The advantages of the DSO are

• Portable
• Have the highest bandwidth
• The user interface is simple
• Speed is high

Disadvantages

The disadvantages of the DSO are

• Complex
• High cost

Why to choose Digital Storage Oscilloscope(DSO)  in place of CRO ?

Choosing between a digital oscilloscope and a cathode-ray oscilloscope (CRO) depends on the specific needs and requirements. Both have their advantages and disadvantages. Here are some reasons why one might consider going for a digital oscilloscope over a CRO:

• Advanced functionality: Digital oscilloscopes generally offer more advanced features compared to traditional CROs. These include signal analysis, mathematical operations, automatic measurements, storage capabilities, and more. Digital oscilloscopes often have built-in FFT (Fast Fourier Transform) for spectrum analysis, which is not typically found in CROs.
• Storage and memory: Digital oscilloscopes can store waveforms and data for later analysis. This is particularly useful for capturing intermittent or rare events that might be missed on a CRO. Some digital oscilloscopes also come with PC connectivity, allowing you to transfer and analyze data on a computer.
• Screen and waveform clarity: Digital oscilloscopes usually have better display resolutions and clarity compared to CROs. This makes it easier to read waveforms and make precise measurements.
• Ease of use: Digital oscilloscopes often have intuitive user interfaces with touchscreens and menu-driven controls, making them easier to operate, especially for those less familiar with analog controls found on CROs.
• Multiple channels: Many digital oscilloscopes come with multiple channels (2, 4, or even more), allowing you to observe and compare multiple signals simultaneously. CROs usually have limited channel options.
• Signal analysis and processing: Digital oscilloscopes can perform various signal processing tasks, such as filtering, averaging, and mathematical operations, making it easier to analyze complex waveforms.
• Portability: Digital oscilloscopes are generally more compact and lightweight than traditional CROs, making them more suitable for fieldwork or on-the-go applications.

However, it’s essential to note that there are still instances where a CRO might be preferred:

• Budget constraints: CROs are often less expensive than digital oscilloscopes, which can be a significant factor for those on a tight budget.
• Analog signal fidelity: If you are primarily dealing with analog signals and don’t require advanced digital features, a CRO might be sufficient for your needs.

Real-time response: In some specialized applications, the real-time response of an analog CRO might be advantageous over the processing delays that can occur in digital oscilloscopes.

FAQS

1). What is the difference between CRO and DSO?

The Cathode Ray Tube (CRO) is an analog oscilloscope whereas DSO is a digital oscilloscope.

2). What is the difference between digital and analog oscilloscope?

The waveforms in an analog device are shown in original form whereas in digital oscilloscope the original waveforms are converted into digital numbers by sampling.

3). What is an oscilloscope used to measure?

An oscilloscope is an instrument which is used to analyze and display the electronic signal waveforms.

4). Is an oscilloscope an analog?

There are two types of oscilloscopes they are analog oscilloscope and digital oscilloscope.

5). Can an oscilloscope measure sound?

Yes, an oscilloscope can measure sound by converting that sound into voltage.

In this article what is digital storage oscilloscope (DSO), a block diagram of DSO, advantages, disadvantages, applications, DSO products, operation modes of DSO, and wave reconstruction of DSO are discussed. Here is a question for you what are the features of a digital storage oscilloscope?