Digital oscilloscopes use an analog-to-digital (A / D) converter to convert the measured voltage into digital information.
It captures the signal in the form of successive sample points and stores these sample points until enough points have been collected to describe a signal. Subsequently, these dots are reassembled to display the signal on the screen.
Digital oscilloscopes can be divided into the following groups:
- Digital Storage Oscilloscopes (DSOs)
- Digital Phosphor Oscilloscopes (DPOs)
- Mixed Signal Oscilloscopes (MSOs)
The digital storage oscilloscope
DSOs consist of data processing subsystems that are used to collect and display data from the entire signal. A DSO uses a serial processing architecture to capture and display the signals (Figure 1).A digital storage oscilloscope, such as the TDS2024, can capture repetitive signals and single-shot events. Because the signal information is in digital form, it can be analyzed, printed or archived directly from the oscilloscope or external computer. DSOs offer the option of permanent signal storage and advanced signal processing.
A serial processing architecture
The input stage of a DSO is the vertical amplifier. Over this, the amplitude of the signal can be adjusted. Next, the analog-to-digital converter (A / D converter) samples the signal at discrete times and converts the voltage of the signal at those points into digital values. This process is called digitizing a signal. The number of signal points used to record a signal is called the record length.
The sampling clock of the system determines how often the A / D converter scans. This rate is called the sampling rate and is expressed in samples per second. The signal path of the DSO includes a microprocessor which passes the measured signal to the screen. This microprocessor processes the signal, coordinates screen activities, manages the front panel controls, and performs other tasks.
Depending on the scope of the oscilloscope, further processing can be used to improve the signal presentation. Most modern digital oscilloscopes offer a choice of automatic, parametric measurement functions that simplify the measurement process.
DSOs are ideal for low repetition applications or single-shot, high-speed, and multi-channel design applications.
The Digital Phosphor Oscilloscope (DPO) is a new kind of oscilloscope architecture. This architecture provides the DPO with unique capture and display capabilities for accurately displaying a signal. A DPO works on the principle of a parallel processing architecture and records, analyzes and displays the signals under investigation (Figure 2).
DPOs provide high signal acquisition rates, resulting in the improved signal presentation. This technology increases the likelihood that transient events are occurring in digital systems, such as run-time pulses, glitches, and flank errors, will be detected and provides advanced analysis capabilities.
The parallel processing architecture
Like the DSO, the first stage of the DPO is the vertical amplifier followed by the A / D converter. However, the subsequent stages of the DPO differ significantly from those of the DSO. Digital storage oscilloscopes process captured signals serially. In this process, the speed of the microprocessor is the critical performance factor because it limits the signal acquisition rate.
Avoid the bottleneck in data processing
In contrast, the DPO rasterizes the digitized data into a digital phosphorus database. Every 1/30 second, a snapshot of the signal image stored in the database is output directly to the display system. This direct rasterization of the signal data and the direct copy from the database into the display memory eliminate the data processing bottleneck that occurs with other architectures.
The result is an improved real-time update of the display. Signal details, seasonal events and dynamic signal characteristics are captured in real time. The microprocessor of the DPO works in parallel with the display management, measurement automation, and meter control so that the oscilloscope’s acquisition speed is not affected. A DPO represents the signal in three dimensions: time, amplitude and amplitude distribution as a function of time. All this happens in real time.
Combines analog and digital oscilloscope techniques
The Digital Phosphor Oscilloscope (DPO) combines the advantages of analog and digital oscilloscope technology. They can display both high and low frequencies, repetitive signals as well as transients and signal variations in real time.
A DPO is ideal for tasks that require the best all-around design and troubleshooting equipment for a wide range of applications. Some DPOs can capture millions of signals in seconds, increasing the likelihood that intermittent and infrequent events will be detected and dynamic signal behavior detected.
The mixed signal oscilloscope
The Mixed Signal Oscilloscope (MSO) combines the functions of a DPO with the basic functions of a 16-channel logic analyzer, including parallel / serial bus protocol decoding and triggering. The digital channels of an MSO indicate a digital signal as either logic high or logic low.
With powerful digital triggering, high-resolution acquisition and analysis tools, the MSO is ideal for fast troubleshooting in digital circuits. The cause of many problems in digital circuits can be more quickly determined by analyzing both the analog and the digital representation of the signal (Figure 3). Therefore, an MSO is ideal for troubleshooting digital circuits. You can read the oscilloscope buying guide before buying an oscilloscope.