Answer: A digital storage oscilloscope, also known as a DSO, is an electronic device that is capable of storing a digital copy of the measured waveform. Using analog-to-digital converters to digitize and sample measured voltages, a digital storage oscilloscope stores the results in its memory, which it process further using digital signal processing techniques.

DSO converts analog input voltages into digital data. Two factors determine the maximum frequency that the digital storage oscilloscope can measure. One is the sampling rate of the oscilloscope, which is usually measured in millions or billions of samples per second, and the other is the nature of the analog-to-digital converter and the signal amplifier on each input. Upon capturing a signal, the scope stores as many samples as possible in its memory to represent the waveform.

The block diagram is shown below :

Figure shows the block diagram of DSO as consists of : 

• Data acquisition
• Storage
• Data display.

1. Data acquisition is earned out with the help of both analog to digital and digital to analog converters, which is used for digitizing, storing and displaying analog waveforms. Overall operation is controlled by control circuit which is usually consists of microprocessor.
2. Data acquisition portion of the system consist of a Sample-and-Hold (S/H) circuit and an analog to digital converter (ADC) which continuously samples and digitizes the input signal at a rate determined by the sample clock and transmit the digitized data to memory for storage. The control circuit determines whether the successive data points are stored in successive memory location or not, which is done by continuously updating the memories.
3. When the memory is full, the next data point from the ADC is stored in the first memory location writing over the old data.
4. The data acquisition and the storage process is continues till the control circuit receive a trigger signal from either the input waveform or an external trigger source.
5. When the triggering occurs, the system stops and enters into the display mode of operation in which all or some part of the memory data is repetitively displayed on the cathode ray tube.
6. In display operation, two DACs are used which gives horizontal and vertical deflection voltage for the CRT Data from the memory gives the vertical deflection of the electron beam, while the time base counter gives the horizontal deflection in the form of staircase sweep signal.
7. The screen display consist of discrete dots representing the various data points but the number of dot is very large as 1000 or more that they tend to blend together and appear to be a smooth continuous waveform. The display operation ends when the operator presses a front-panel button and commands the digital storage oscilloscope to begin a new data acquisition cycle.

The DSO has three modes of operation : 

• Roll mode : In this mode , the input signal continuously displayed on the screen. This mode is used to observe fast varying signals.
• Store mode : This is also called as refresh mode . In this mode , the input signal is digitised and stored in the memory until memory is full. When memory is full write cycle stops and in order to store the next signal , memory is refreshed.
• Hold mode : This is automatic refresh mode. If changes in the input voltage re-triggers the DSO then the memory is overwritten with a new recording unless the user puts the system into HOLD mode, Hold mode allows the user to analyse the signal trace for as long he/she requires.

Application : DSO are used in a wide variety of different industries and applications. Here are some of the more common applications and uses for oscilloscopes today:

• Power analysis - DSO can be used to measure and analyze the operating characteristics of power conversion devices, circuits, and line-power harmonics. Differential amplifier probes are needed to this, and special software is also offered to make analysis of the data easier.
• Serial data analysis - Digital data signals are moving to ever-increasing serial data formats. DSO are used to analyze and characterize such data formats as USB, SCSI, Ethernet, Serial ATA, Fibre Channel, FireWire, Rapid I/O, InfiniBand, Bluetooth and CAN Bus .
• Jitter analysis. - Today, high-bandwidth circuits have extremely fast clocks and signals. DSO are used to characterize and debug signal jitter as well as timing for clocks, clock-to-data and datastream analysis.
• Data storage device testing. - DSO are used to test CD/DVD and disk drive designs by measuring disk performance, media noise and optical recording characteristics.
• Time-domain reflectometry. - Time Domain Reflectometry (TDR) is a way to measure impedance values and variations along transmission cables, cables connectors or microstrips on a circuit board.