This index is dedicated to programs that are not part of the scopes themselves, but help to make the scope experience better. For example a MyInfiniium script or a User Defined Function and example would be ideal for this forum index. This allows for us all to share our ideas and scripts.
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Oscilloscopes are the most common tools for designing and testing electronic devices and components. Both digital storage (DSO) and mixed signal (MSO) oscilloscopes are powerful instruments used to display and measure electrical signals over time, and can help determine which components of a system are behaving correctly and which are malfunctioning. They can also help you determine whether or not a newly designed component behaves the way you intended.
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Oscilloscopes are powerful tools that are useful for designing and testing electronic devices. They are vital in determining which components of a system are behaving correctly and which are malfunctioning. They can also help you determine whether or not a newly designed component behaves the way you intended.
Oscilloscopes are far more powerful than multimeters because they allow you to see what the electronic signals actually look like. Oscilloscopes are used in a wide range of fields, from the automotive industry to university research laboratories, to the aerospace-defense industry. Companies rely on oscilloscopes to help them uncover defects and produce fully-functional products.
The single most important characteristic of an oscilloscope, bandwidth provides an indication of range in the frequency domain.
Measured in Hertz, bandwidth dictates the range of signals, in terms of frequency, that you are able to accurately display and test.
Without sufficient bandwidth, your oscilloscope will not display an accurate representation of the actual signal. For example, the amplitude of the signal may be incorrect, edges may not be clean, and waveform details may be lost.
The sample rate of an oscilloscope is the number of samples the oscilloscope can acquire per second. Your oscilloscope should have a sample rate that is at least 2.5 times greater than its bandwidth. However, the ideal sample rate should be 3 times the bandwidth or greater.
A digital oscilloscope uses an A/D (analog-to-digital) converter to digitize an input waveform. The digitized data is then stored in the oscilloscope’s high-speed memory. Memory depth is exactly how many samples or points and, therefore, what length of time can be stored.
Memory depth plays an important role in the sampling rate of an oscilloscope. Ideally, the sampling rate would remain constant no matter the settings on the oscilloscope. However, this would require a huge amount of memory at a large time/division setting. Instead, the sampling rate decreases as you increase the range of time. The more memory depth an oscilloscope has, the more time you can spend capturing waveforms at full sampling speed.
Waveform update rates can be extremely important — sometimes as important as traditional banner specifications including bandwidth and memory depth.
All oscilloscopes have an inherent characteristic called “dead-time”. This is the time between each repetitive acquisition of the scope, when it is processing the previously acquired waveform. Unfortunately, oscilloscope dead-times can sometimes be much longer than acquisition times. During the oscilloscope’s dead-time, any signal activity occurring will be missed, which can make capturing random and infrequent events with a scope a gamble.
Debugging Infrequent Events Using the 4000 X-Series Oscilloscopes
Oscilloscope acquisition modes dictate how the sample points acquired by the scope from the analog-to-digital converter (ADC) are combined and displayed as waveform points. The following acquisition modes are the most common:
Normal or Sample Acquisition Mode
This is the most basic acquisition mode where one waveform point is created from one sample point during each waveform interval. It is the most common and yields the best display for most waveforms.
Averaging Acquisition Mode
The averaging mode lets you average multiple acquisitions together to reduce noise and increase vertical resolution. Averaging requires a stable trigger and repetitive waveform. A higher number of averages reduces noise more and increases vertical resolution.
Roll Mode is a triggerless acquisition mode in which acquisition data is displayed in a rolling fashion starting at the right side of the display and continuing to the left (while the acquisition is running). Roll mode is useful when making manual adjustments to low-frequency waveforms, finding disturbances in low-frequency waveforms, or monitoring the power-up cycle of a power supply voltage.Because roll mode is a triggerless acquisition mode, there is no trigger reference and all trigger features are disabled. New data will continue rolling across the screen while the acquisition is running. The horizontal reference point is set to the right and is the current moment in time. Waveform data points are scrolled to the left of the horizontal reference point at the current sampling rate.
Peak Detect Mode
All DSOs and MSOs have a fixed amount of acquisition memory. This is the number of samples that the oscilloscope can digitize for each acquisition cycle. If the scope’s timebase is set to a relatively fast time/div setting, such as 20 ns/div, then the scope will always have a sufficient amount of memory to capture a waveform at that setting using the scope’s maximum specified sample rate. For example, if a scope’s maximum specified sample rate is 4 GSa/s (250 ps between samples), and if the scope’s timebase is set to 20 ns/div, then an acquisition memory depth of 800 points is all that is required to capture and display a complete waveform. At 20 ns/div, a complete waveform across the scope’s screen would consist of 200 ns of time (20 ns/div x 10 horizontal divisions). The required memory depth to fill this time while still sampling at 4 GSa/s is then just 800 points (200 ns/250 ps = 800).
If you set the scope’s timebase to a much slower time/div setting in order to capture slower waveforms and longer time, then the scope may need to automatically reduce its sampling rate in order to fill the required waveform time. All DSOs and MSOs do this. For example, let’s assume that you want to capture a relatively slow signal and need to set the scope’s timebase to 10 ms/div (100 ms across screen). If the scope’s maximum memory depth is 2 M points, then the scope will need to reduce its sample rate to 20 MSa/s (100 ms/2 M = 50 ns sample period).
Although in most cases this is not a problem, because capturing slower waveforms doesn’t require fast sample rates, what if the input signal consisted of a combination of low-speed and high-speed characteristics? For example, what if the input signal that you want to capture is a 30 Hz sine wave with very narrow glitches riding on it? Capturing the 30 Hz sine wave doesn’t require a fast sample rate, but capturing the narrow glitches may require a very fast sample rate.
When the Peak Detect acquisition mode has been selected, rather than sampling waveforms at a reduced rate, the scope intelligently decimates acquired data at a higher sample rate. For example, let’s assume that the scope needs to run at a sample rate that is 1/100th of its maximum sample rate. This would be equivalent to running the scope at its maximum sample rate, but only storing every 1/100th point, which is “unintelligent” decimation. In the Peak Detect mode, the scope would analyze a group of 200 consecutive samples in real-time (sampled at a high rate), and then store just the maximum and minimum digitized values for this group of 200 points, which is just 2 points. This would be a decimation factor of 100. So you may ask, why not always use the Peak Detect mode? There are some tradeoffs when using this mode of acquisition. First of all, the scope’s absolute maximum sample rate is reduced. Secondly, stored points will NOT be evenly spaced. And this is an important criterion of the Nyquist Sampling theorem. So for this particular measurement application, using the Peak Detect mode is a good choice. But for other measurement applications, Peak Detect may not be the appropriate acquisition mode.
High Resolution Acquisition Mode
High Resolution mode averages sequential sample points within the sample acquisition. It results in a reduction of random noise, produces a smoother trace on screen, and effectively increases the vertical resolution. It does not require a repetitive waveform like averaging does.
Segmented memory allows the acquisition memory to be divided into a set of equal-length sub-records, which are equal in total collective length to the full memory depth of the oscilloscope. Segmented memory is useful for applications that have multiple bursts of data that are separated by dead time, as it maximizes the oscilloscope’s memory depth by only capturing a sub-record after a triggered event.Before segmented memory was available, the best way to acquire and store data from consecutive trigger events on-the-fly was to store the acquired data from each trigger to the oscilloscope’s hard drive. The time it took to save each waveform to the hard drive greatly constrained the overall throughput.With segmented memory, the oscilloscope uses the actual high-speed acquisition memory to store each waveform instead of the hard drive. This greatly improves throughput and minimizes between-cycle dead time.
Use for waveforms with frequency components less than 1⁄4 the sampling rate.
Capture waveforms that occur infrequently, such as glitches.
Use for single-shot waveform events.
Peak Detect Acquisition Mode:
Quickly find waveform anomalies > 50 ps wide that occur between samples at slow sweep speeds.
See if a waveform is aliased.
Use for single-shot waveform events.
For periodic waveforms, normal Averaging can be used to reduce the noise over several triggers.
High-Resolution Acquisition Mode:
Reduce noise and improve signal-to-noise ratio on non-periodic (single-shot) waveforms. For periodic waveforms, normal Averaging can be used to reduce the noise over several triggers.
Improve the resolution of your signal. As the high-resolution interval increases, the number of effective bits also increases (up to a certain point).
Segmented Sampling Mode (Normal, Peak Detect, or High-Resolution Acquisition Modes):
View waveform events that are far apart in time, but have high-frequency content.
Roll Mode Sampling Mode:
Use when making manual adjustments to low-frequency waveforms.
Find disturbances in low-frequency waveforms.
Monitor the power-up cycle of a power supply voltage.
See segmented memory in action
Basic Oscilloscope Controls
Many oscilloscopes on the market today have various ways to control the scope, including using the front panel, touch screen, or soft keys. Some of the basic controls seen on most oscilloscopes include:
Horizontal Controls: An oscilloscope’s horizontal controls typically are grouped in a front- panel section marked Horizontal. These controls enable you to make adjustments to the horizontal scale of the display. There will be a control that designates the time per division on the x-axis. Again, decreasing the time per division enables you to zoom in on a narrower range of time. There will also be a control for the horizontal delay (offset). This control enables you to scan through a range of time.
Vertical Controls: Vertical controls on an oscilloscope typically are grouped in a section marked Vertical. These controls allow you to adjust the vertical aspects of the display. For example, there will be a control that designates the number of volts per division (scale) on the y-axis of the display grid. You can zoom in on a waveform by decreasing the volts per division or you can zoom out by increasing this quantity. There also is a control for the vertical offset of the waveform. This control simply translates the entire waveform up or down on the display.
Trigger Controls: Triggering on your signal helps provide a stable, usable display and allows you to synchronize the scope’s acquisition on the part of the waveform you are interested in viewing. The trigger controls let you pick your vertical trigger level (for example, the voltage at which you want your oscilloscope to trigger) and choose between various triggering capabilities.
Here is an example of the vertical and horizontal control sections on the front panel of a Keysight InfiniiVision 2000X Series oscilloscope.
Once you have acquired a signal and displayed it on the oscilloscope, the next step is usually to perform measurements on the waveform. Oscilloscopes now have a tremendous amount of built-in measurement capabilities that enable you to quickly analyze your waveform. Some examples of these basic measurements include:
Rise time: Rise time is the time at the upper threshold minus the time at the lower threshold of the edge you are measuring. Fall time is similar in that it is the time at the lower threshold minus the time at the upper threshold of the edge you are measuring.
Pulse Width: Pulse Width is the time from the mid-threshold of the first rising edge to the mid-threshold of the next falling edge.
Amplitude and Other Voltage Measurements: This is a measure of the amplitude of the waveform display. You can also usually measure the peak-to-peak voltage, max voltage, min voltage, and average voltage.
Period / Frequency: Period is defined as the time between the mid-threshold crossings of two consecutive, like-polarity edges. Frequency is defined as 1/Period.
There are many other measurements available on an oscilloscope, but this gives you an idea of some of the fundamental measurements.
Make Great Oscilloscope Measurements
There are many mathematical operations you can perform on your waveforms. Some examples include:
Fourier transform: This math function allows you to see the frequencies that compose your signal.
Absolute value: This math function shows the absolute value (in terms of voltage) of your waveform.
Integration: This math function computes the integral of your waveform.
Addition or subtraction: These math functions enable you to add or subtract multiple waveforms and display the resulting signal.
Again, this is a small subset of the possible measurements and mathematical functions available on an oscilloscope.
Triggering enables you to do two things on your oscilloscope:
Locate events in your waveform
Obtain a stable display
Once you set the trigger conditions, the oscilloscope looks at your acquisitions to see when these conditions are met. When they are met, the oscilloscope displays the trigger event and begins looking for the next trigger event (unless you are in the Single acquisition mode, in which case it stops). This allows you to set the trigger conditions to find specific portions of your waveform.
There are several different types of triggering but the one that is used most often is edge triggering. Edge triggering identifies a trigger condition by looking for the slope (rising or falling) and voltage level (trigger level) on the source you select. Any input channel, auxiliary input trigger, or line input can be used as the trigger source.
The following figure shows the trigger circuit diagram.
Your waveform enters the positive input to the trigger comparator where it is compared to the trigger level voltage on the other input. The trigger comparator has a rising edge and a falling edge output. When a rising edge of your waveform crosses the trigger level, the rising edge comparator output goes high and the falling edge output goes low. When a falling edge of your waveform crosses the trigger level, the rising edge output goes low and the falling edge output goes high. The oscilloscope uses the output you have selected as the trigger output.
Zone triggering is also very useful and found on some oscilloscopes. This trigger lets you draw a box on the scope’s display and set certain trigger conditions such as “must intersect”, “not intersect”, etc. This can make triggering on complex signals easy when typically you would have to setup an advanced trigger condition.
Learn about new oscilloscope features that simplify isolating signal anomalies in these application notes
See how easy the Zone Touch triggering feature can make isolating an infrequent glitch
Sometimes a basic edge trigger is not enough to isolate/capture your signal. In these instances, oscilloscopes have advanced triggers you can use. Some examples of advanced triggers include:
Pulse Width Trigger
The oscilloscope identifies a pulse width trigger by looking for a pulse that is either wider or narrower than other pulses in your waveform. You specify the pulse width and pulse polarity (positive or negative) that the oscilloscope uses to determine a pulse width trigger. For a positive polarity pulse, the oscilloscope triggers when the falling edge of a pulse crosses the trigger level. For a negative polarity pulse, the oscilloscope triggers when the rising edge of a pulse crosses the trigger level.
Use Runt triggering to find a positive or negative pulse that has a smaller amplitude than the rest of the pulses. A low and high threshold are established with this trigger. The oscilloscope then looks for pulses that fall between these two thresholds and triggers when one is found.
Edge Then Edge Trigger
The Edge then Edge trigger mode triggers when the Nth edge occurs after an arming edge and a delay period.
The Pattern trigger identifies a trigger condition by looking for a specified pattern. A pattern is a logical combination of the channels. Each channel can have a value of 1 (High), 0 (Low) or X (Don’t Care). A value is considered a High when your waveform’s voltage level is greater than its trigger level and a Low when the voltage level is less than its trigger level. If a channel is set to Don’t Care then it is not used as part of the pattern criteria.
Video triggering can be used to capture the complicated waveforms of most standard analog video signals. The trigger circuitry detects the vertical and horizontal interval of the waveform and produces triggers based on the video trigger settings you have selected.
In addition to the standard and advanced trigger modes found in oscilloscopes, there are also special triggers to assist in the decode of specific buses. For example, common trigger and decodes include:
I2C / SPI
MIL-STD-1553 / ARINC 429
UART / RS232
And many more…
As an example of this capability found in many scopes, learn how to debug automotive designs faster with CAN-dbc Symbolic Trigger and Decode
And here are some videos that show this capability as well:
Advanced Oscilloscope Triggering and Signal Isolation
Probes are used to connect the oscilloscope to your device under test (DUT). A variety of factors, including probe type, probe loading and bandwidth can impact how accurately you are able to display and analyze your signal.
What's that you were asking about oscilloscope probes? - Recorded webcast
The most common type of scope probe today is the passive voltage probe. Passive probes contain only passive components and do not require a power supply for their operation. They are useful for probing signals with bandwidths less than 600 MHz. Passive probes usually produce relatively high capacitive loading and low resistive loading.
Passive probes can be divided into two main types: high-impedance-input probes and low- impedance resistor-divider probes. The high-impedance-input passive probe with a 10:1 division ratio is probably the most commonly used probe today.
Compared to active probes, passive probes are more rugged and less expensive. They offer a wide dynamic range (>300 V for a typical 10:1 probe) and high input resistance to match a scope’s input impedance. However, high-impedance-input probes impose heavier capacitive loading and have lower bandwidths than active probes or low-impedance (z0) resistor-divider passive probes.
Active probes require a power supply for active devices within the probe itself. Active probes contain a small, active amplifier built into the probe body near the probe tip. This arrangement makes it possible to keep the probe input capacitance very low, usually less than 2 pF. This low capacitance results in high input impedance on high frequencies. It has the best overall combination of resistive and capacitive loading. With such low loading, active probes can be used on high-impedance circuits that would be seriously loaded by passive probes. Active probes are the least intrusive of all the probes.
If your scope has more than 500 MHz of bandwidth, you are probably using an active probe—or should be. Despite its high price, the active probe is the tool of choice when you need high bandwidth performance. Active probes typically cost more than passive probes and feature limited input voltage but, because of their significantly lower capacitive loading, they give you more accurate insight into fast signals.
A “differential” probe is an active probe that has two inputs, one positive and one negative, as well as a separate ground lead; it drives a single-terminated 50-Ω cable to transmit its output to one oscilloscope channel. The output signal is proportional to the difference between the voltages appearing at the two inputs. A differential probe is used to look at signals that are referenced to each other instead of earth ground and to look at small signals in the presence of large DC offsets or other common mode signals such as power line noise.
Typically you would choose a single-ended active probe for measuring single-ended signals (a voltage referenced to ground) and differential active probes for measuring differential signals (a plus voltage versus a minus voltage). However, one thing to keep in mind is that the effective ground plane between the signal connections in differential probes is more ideal than most of the ground connections in single-ended probes. This ground plane effectively connects the probe tip ground to the device-under-test (DUT) ground with very low impedance. Therefore differential probes can make even better measurements on single-ended signals than single-ended probes can.
Current probes sense the current flowing through a conductor and convert it to a voltage that can be viewed and measured on an oscilloscope. Many current probes use a hybrid technology that includes a Hall-effect sensor, which senses the DC current, and a current transformer, which senses the AC current. Using split core construction, the current probe easily clips on and off of a conductor, making it unnecessary to make an electrical connection to the circuit.
The term “signal integrity” surfaces regularly in electronic test. Signal integrity is the primary measure of signal quality, and signal integrity’s importance increases with bandwidth, the need to view small signals, or the need to see small changes on larger signals. Why does oscilloscope signal integrity matter? Signal integrity impacts all scope measurements. The amount of impact signal integrity can make on signal shape and measurement values might surprise you. Oscilloscopes themselves are subject to the signal integrity challenges of distortion, noise, and loss. Scopes with superior signal integrity attributes provide a better representation of signals under test, while scopes with poor signal integrity attributes show a poorer representation of signals under test. This difference impacts engineers’ ability to gain insight, understand, debug, and characterize designs. Results from oscilloscopes with poor signal integrity can increase risk in development cycles times, production quality, and components chosen. To minimize this risk, it is a good idea to evaluate and choose an oscilloscope that has high signal integrity attributes.
Power integrity (PI) is a broad term used in the electronics industry that refers to the analysis of how effectively power is converted and delivered from the source to the load within a system.
The power is delivered through a power distribution network (PDN) that consists of passive components and interconnects from the source to the load including packaging up to the semiconductor. It typically includes measurements from DC to multi-gigahertz.
Switch Mode Power Supply Measurements and Analysis - Recorded Webcast
Frequency Domain/Spectrum Analysis
Many of today’s digital oscilloscopes include a Fast Fourier Transform (FFT) for frequency domain analysis. This feature is especially valuable for oscilloscope users who have limited or no access to a spectrum analyzer yet occasionally need frequency domain analysis capability. An integrated oscilloscope FFT provides a cost effective, space saving alternative to a dedicated spectrum analyzer.
The oscilloscope Fast Fourier Transform (FFT) function and a variety of other math functions can prove valuable when bringing digital and RF designs to market. For example, the FFT function in an oscilloscope can quickly highlight the frequency content of signals coupled onto power supply rails. This, in turn, can help pinpoint the source of such noise signals. That’s important because such signals can translate into noise in other parts of the design, cutting signal margins, and potentially preventing the design from moving beyond the prototype stage until the problem is fixed. An FFT spectral view can also be helpful when looking at RF signals to verify if the proper pulse characteristics or modulation is happening. Time-gated FFTs even further evaluate spectral components of a signal, such as what frequency is present at certain points along RF pulses. Math functions such as a “Measurement Trend” on frequency measurements can quickly verify whether a classic modulation scheme is happening properly, like a linear frequency modulation chirp across RF pulses in a pulse train.
Watch a video on making basic FFT measurements on an oscilloscope
Mixed Signal Analysis
In standard digital oscilloscopes, the input signal is analog and the digital-to-analog converter digitizes it. However, as digital electronic technology expanded, it became increasingly necessary to monitor analog and digital signals simultaneously. As a result, oscilloscope vendors began producing mixed signal oscilloscopes that can trigger on and display both analog and digital signals. Typically there are a small number of analog channels (2 or 4) and a larger number of digital channels. Mixed signal oscilloscopes have the advantage of being able to trigger on a combination of analog and digital signals and display them all, correlated on the same time base.
Jitter is any frequency or phase related spurious variation of a waveform from its ideal. Jitter appears on a waveform edge before or after the trigger point as wide smeared edge. In other words, if you were to plot an eye diagram, the jitter is a measurement of the variance in time locations of the crossing points (see screen shot below).
Jitter has various causes; here are several potential ones:
Vertical noise in the oscilloscope
As data rates continue to increase in today’s state-of-the-art high-speed digital designs, timing budgets are decreasing. Ensuring that serial data signals are valid and stable when receivers sample the data often requires an understanding of the effects of the various components of jitter that may contribute to decreased valid data windows. The primary measurement tool used today by hardware design engineers to capture and view waveform jitter is an oscilloscope. Many of today’s higher performance oscilloscopes also provide optional jitter analysis measurement capabilities that can not only be used to view jitter in different display formats, but they can also quantize the various components of jitter.
Watch a video to learn more about making jitter measurements
Oscilloscopes are great tools for the testing, decoding, and analysis of serial buses. Most oscilloscopes offer a wide range of serial bus analysis packages that usually includes the ability to trigger on the bus as well as decode it. Examples would include CAN, LIN, I2C, SPI, and many more.