Block Diagram of Digital Storge Oscilloscope DSO

Summary

This video explains the block diagram and operation of a Digital Storage Oscilloscope (DSO). It covers the process of digitizing an analog signal, storing it in memory, and then converting it back to an analog form for display on a CRT screen. The video explores key components like the A/D converter, memory, and time-based circuitry, detailing their functions in signal processing. It also discusses advanced features such as analog and digital stores, addressing issues like aliasing and resolution loss. Additionally, it explains the reconstruction of waveforms using interpolation techniques for accurate display.

Takeaways

• 😀 A Digital Storage Oscilloscope (DSO) converts and stores analog signals in digital form for display and analysis.
• 😀 The block diagram of a basic DSO includes components such as input signal, amplifier, digitizer (A/D converter), memory, and CRT display.
• 😀 The DSO converts an analog signal to digital, processes it, and then converts it back to analog for display on the screen.
• 😀 The vertical and horizontal inputs to the CRT display correspond to the y-axis (signal) and x-axis (time), respectively.
• 😀 The time base circuit, controlled by a clock and the input signal, generates a ramp signal that is used for the horizontal input of the CRT.
• 😀 A more complex DSO includes an attenuator, amplifier, sample and hold circuit, A/D converter, digital store, and a microprocessor for control.
• 😀 The sampling theorem states that the sampling rate should be at least twice the frequency of the highest signal to avoid aliasing.
• 😀 Aliasing occurs when the sampling rate is insufficient, causing distortion in the signal when converted from analog to digital.
• 😀 To mitigate aliasing effects, analog and digital stores are added to the DSO, allowing for high-speed sampling without sacrificing resolution.
• 😀 The waveform reconstruction can be done using linear interpolation (joining dots with a straight line) or sinusoidal interpolation (joining dots with a sine wave).

Q & A

What is a Digital Storage Oscilloscope (DSO)?

A Digital Storage Oscilloscope (DSO) is an instrument that captures, stores, and displays electrical waveforms in digital form. It converts analog signals into digital signals, processes them, and then converts them back into analog form for display.

How does the DSO digitize an analog signal?

The DSO digitizes an analog signal using an Analog-to-Digital Converter (A/D), which converts the input analog waveform into a digital signal. A sample-and-hold circuit is used to sample the signal periodically before conversion.

What is the purpose of the sample-and-hold circuit in a DSO?

The sample-and-hold circuit ensures that the analog signal is accurately captured at specific intervals by holding the signal steady during the digitization process.

What components are involved in the block diagram of a DSO?

The block diagram of a DSO includes an amplifier, Analog-to-Digital Converter (A/D), digital memory, microprocessor (control logic), Digital-to-Analog Converter (D/A), time-based circuit, and a Cathode Ray Tube (CRT) for display.

What are the different modes of operation in a DSO?

The three modes of operation in a DSO are: Roll Mode (displays fast-varying signals), Store Mode (stores waveforms in memory for later analysis), and Hold/Save Mode (holds part of the signal for inspection).

What is aliasing in the context of a DSO?

Aliasing occurs when the sampling rate is insufficient, resulting in an inaccurate representation of the signal. This can happen when the sampling rate is less than twice the highest frequency of the input signal.

How does the DSO prevent aliasing?

To prevent aliasing, the DSO uses an analog store and a digital store. This allows the signal to be sampled at a slower rate without affecting the resolution of the A/D converter.

What is the function of the microprocessor in a DSO?

The microprocessor in a DSO controls the entire process, including triggering the sample-and-hold circuit, managing the A/D converter, generating time-based signals, and handling memory operations.

How does the DSO reconstruct the waveform for display on the CRT?

The DSO reconstructs the waveform by connecting the sampled data points (digital form) using either linear interpolation (straight lines) or sinusoidal interpolation (sine waves) to form a smooth analog signal for display on the CRT.

What is the role of the time-based circuit in a DSO?

The time-based circuit generates the time-based signals required for plotting the waveform on the CRT. It ensures that the horizontal axis represents time, while the vertical axis represents the input signal's amplitude.