Types of Oscilloscopes
Several types of oscilloscopes are available, both analog and digital, for a range of prices. Since digital oscilloscopes can miss some transient signals, analog oscilloscopes are still prized for transient troubleshooting applications. However, high-end digital phosphor oscilloscopes can provide similar capabilities.
Analog Oscilloscopes
An analog oscilloscope displays the signal picked up by a probe and traces it on the screen. Storage capabilities allow the waveform to display for extended periods of time rather than decay immediately. Where analog oscilloscopes come into their own is in dealing with analog signals and transient effects. In analog oscilloscopes, phosphors on a CRT monitor glow for a period of time before going dark, allowing high-speed signals to build up a more intense glow. This process allows transients to stand out as well. Analog oscilloscopes offer a better dynamic range than digital oscilloscopes. These don’t suffer from aliasing problems, which can cause false readings. Analog oscilloscopes are generally more affordable than digital oscilloscopes and are a great option for beginners and hobbyists. Analog oscilloscopes that can also handle low-speed digital signals are especially ideal for audio and analog video work.
Digital Oscilloscopes
Digital oscilloscopes are available in many types. Two key factors determine the performance of a digital oscilloscope: sampling rate and bandwidth. An oscilloscope’s sampling rate limits its ability to capture transient, one-time events. The bandwidth of an oscilloscope limits the frequency of repetitive signals that can be displayed.
Digital Storage Oscilloscopes
Most digital oscilloscopes are digital storage oscilloscopes. Digital storage oscilloscopes can capture transient events and store those events for analysis, archival, printing, or other processing. These have permanent storage for recording signals and can be offloaded to other media for storage and analysis. Digital storage oscilloscopes are the workhorses of real-world digital design where four or more signals are analyzed simultaneously. However, unlike an analog oscilloscope, digital storage oscilloscopes cannot display the level of intensity of a real-time signal. Single-shot events can be captured through the use of triggers, which can be set manually or automatically depending on the device.
Digital Phosphor Oscilloscopes
Digital phosphor oscilloscopes allow for faster signal capture and analysis than standard digital storage oscilloscopes. Digital phosphor oscilloscopes use a parallel processing ADC solution that delivers higher sampling rates, enabling a signal visualization performance level that has the appearance of real-time. Digital phosphor oscilloscopes are similar to analog oscilloscopes in displaying the intensity of a signal. These oscilloscopes duplicate the effect of phosphorus by storing a database of the values of the repeating waveforms and increasing the intensity on the display where the waveforms overlap. Like an analog oscilloscope, a digital phosphor scope can reveal transients by displaying the intensity level. However, it can miss transients that happen outside of the data capture window and its update rate. Digital phosphor oscilloscopes combine the features of digital storage oscilloscopes and analog oscilloscope technology. These qualities are great for general purpose design, digital timing, advanced analysis, communication testing, and troubleshooting.
Mixed Domain Oscilloscopes
A mixed domain oscilloscope combines the functionality of a digital oscilloscope, an RF spectrum analyzer, and a logic analyzer into one device. When designing or working with systems that include digital signals, digital logic, and radiofrequency communication, mixed domain oscilloscopes are an essential tool. The main benefit of a mixed domain oscilloscope is seeing signals from each domain time-correlated to each other, which helps with troubleshooting, debugging, and design testing.
Mixed Signal Oscilloscopes
Engineers often use digital oscilloscopes and logic analyzers together, which is why the mixed signal oscilloscope was developed. These devices combine the capabilities of a digital storage oscilloscope (or a digital phosphor oscilloscope) with a multi-channel logic analyzer. The digital triggering capability of the mixed signal oscilloscope aids the analysis of analog events that can trigger digital logic transitions. Typically, mixed signal oscilloscopes have two or four analog input channels and around 16 digital input channels.
Digital Sampling Oscilloscopes
Digital sampling oscilloscopes have a slightly different input technique that trades a higher bandwidth for a lower dynamic range. The input is not attenuated or amplified, so the oscilloscope must handle the full range of the input signal, which is generally limited to about 1-volt peak-to-peak. Digital sampling oscilloscopes only work on repetitive signals and will not help capture transients beyond the normal sampling rate. On the other hand, digital sampling oscilloscopes can capture signals that are an order of magnitude faster than other types of oscilloscopes with bandwidths exceeding 80 GHz.
Handheld Oscilloscopes
Small handheld oscilloscopes are available for field and test applications where bulkier oscilloscopes are unwieldy or power outlets are unavailable. These typically contain two inputs and have limited sampling rates and bandwidth.
Computer-Based Oscilloscopes
Computer-based oscilloscopes are small, external devices that connect to a computer through USB. These types of oscilloscopes have seen significant improvements in sampling rates and bandwidth over the years. Some computer-based oscilloscopes have the same capabilities as low-end digital storage oscilloscopes for only a few hundred dollars. These are a great option for hobbyists looking for an oscilloscope.
