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Oscilloscopes Blog

14 Posts authored by: melissakeysight Employee

Power Quality Determines the Performance of Your Device

Your product’s functional reliability is directly proportional to the quality of the DC power inside your product. Intuitively this makes sense: Stable DC supplies should not cause issues. Unstable DC supplies can cause unreliable performance.

 

In today’s products, IC density is increasing to provide more features faster. This means there are a larger number of smaller components packed onto each board, which makes your product more susceptible to the effects of poor power. To minimize the trouble power can cause, your design must convert and deliver DC power from the converters to the gates on the IC as effectively as possible. In other words, you want your design to have high power integrity, testing and verifying the integrity is crucial.

 

Tests Required to Validate Power Integrity

Evaluation usually consists of these four steps:

1. Analyze the output of your DC/DC converters without the rest of the circuit turned on.

  • This is to test the supply’s stability, looking for drift and PARD (Periodic and Random Disturbances).

2. Turn on your system and stress the supply under various operating conditions.

  • For example, test static and dynamic load to check the response and high frequency switching while keeping an eye out for transients and noise.

3. If your system has different power saving modes, you’ll evaluate your programmable power rails.

  • You want to ensure your supplies are reaching their intended level with the appropriate latency.

4. Lastly, run some (or all) of these tests again in a temperature chamber or accelerated life tester.

  • It is important to check operation in extreme environmental conditions and how your device will perform over time.

 

The Challenges of Making Power Integrity Measurements

For all the tests described above, you have a specific tolerance band. If the AC signals riding on your DC signal deviates too much, you have poor power integrity and your design is flawed. 

 

There are two major challenges to measuring your power integrity: noise and offset.

 

Noise

Noise from your oscilloscope, probe, and the connection to the DUT, are mixed in to your signal when you measure it. The result is that you don’t see an exact version of your signal on the oscilloscope screen. In light of this, make sure you are using a high-quality measurement system.

 

That means:

  • Choose an oscilloscope with low noise.
  • Choose a probe with low noise and 1:1 attenuation.
  • Connect to your DUT using as short of a lead as possible, with minimal to no probe-tip accessories.

 

Following these guidelines ensures you won’t mistake measurement system noise for power rail noise.

 

Offset

Viewing your AC swing can be difficult when your DC signal is large. To see the full signal on screen, you have to zoom out really far, but then you aren’t looking closely at the AC details. So, what do you do? Use a probe with support for power rail voltages. This is a probe with enough offset to be able to center the signal on screen without blocking DC so you can zoom in on the details of your waveform. What about a DC block, you ask?

 

Probe offset is better than using a DC block because:

1. Blocking capacitors not only block DC, they also block or filter low frequency AC.

 

  • This inhibits the ability to see drift, droop, sag, and other changes to the DC value of the power rail. These attributes are often critical to observe when your FPGAs and microprocessors turn on and off.

5V on a USB device measured with a DC block

Figure 1. 5V on a USB device measured with a DC block.

 

  • Probe offset passes all the AC content to the oscilloscope unfiltered.

5V on a USB device measured with probe offset

Figure 2. 5V on a USB device measured with probe offset.

 

  • In Figure 1, you can see the DC block shows what looks like a stable DC supply. In reality, the supply has some issues that become visible using the power rail probe in Figure 2. The issues can’t be seen with the DC block because it filters out the low frequency drift in the supply.

 

2. When using a DC block, the capacitor can discharge into your oscilloscope and blow out its front end. This is because the power rail you are measuring may exceed the input voltage of the oscilloscope, and the capacitor is being charged with that voltage. You may think you are protecting the oscilloscope from the voltage of your device, but if the capacitor discharges, all that energy will be sent into the front-end of your oscilloscope. This could be a costly repair.

 

3. DC blocks can make documentation of results tedious.

 

  • A DC block blocks all DC information from arriving to your oscilloscope. As a result, the oscilloscope will show the waveform centered at zero volts. Therefore, you need to use a DMM (digital multimeter) to see what the nominal value of the supply is and then manually type this information into any saved data or screen shots. Using a probe with offset means the oscilloscope knows the DC offset and can display things correctly, which makes record keeping easier. The DC offset is considered in any automated measurements or applications.

 

Additional Challenges – Loading and Bandwidth

 

Probe loading can cause your power supply to behave differently than it does without the probe connected or cause measurement errors like sag. So, you’ll also want to use a probe with very low loading.

 

You also want to choose a probe with high bandwidth. As I mentioned in the introduction, devices are now trying to do more at faster speeds. These increased speeds can introduce crosstalk on boards with small dimensions and lanes close together. And with the risk of crosstalk occurring, you’ll need to see transients, which requires high bandwidth. Having more bandwidth is also helpful for viewing high frequency supply noise, which can cause electromagnetic interference.

 

The Right Probe for Power Rail Measurements

Here is a summary of the tips provided above for overcoming power integrity measurement challenges:

 

Use a probe with:

1. Low noise

2. Support for popular rail voltages

3. Low loading

4. High bandwidth

 

If you need a specific product suggestion, use the Keysight N7020A or N7024A (New!) power rail probes.  They both meet the criteria suggested above and summarized below.

 

1. Low noise

  • The N7020A adds only 10% of the oscilloscope noise.
  • The N7024A adds only 30% of the oscilloscope noise.

2. Support for popular rail voltages

  • The N7020A has an offset range of ±24V.
  • The N7024A has an offset range of ±15.25V.

3. Low loading

  • The N7020A has an offset range of ±24V.
  • The N7024A has an offset range of ±15.25V.

4. High bandwidth

  • The N7020A has 2 GHz of bandwidth.
  • The N7024A has 6 GHz of bandwidth.

 

Power rail probe

 

Both probes work with Keysight Infiniium oscilloscopes, which have amazing signal integrity, low noise, and plenty of bandwidth. Additionally, they are compatible with special probing tips that help probe common surface mount capacitors packages.

 

Attribute

N7020A

N7024A

Probe bandwidth (-3dB)

2 GHz

6 GHz

Attenuation ratio

1.1:1

1.3:1

Offset range

± 24V

±15.25V

Input impedance at DC

50kΩ +/-2%

50kΩ +/-2%

Probe noise

0.1 * scope noise

0.3 * scope noise

Active signal range

± 850mV about offset voltage

± 600mV about offset voltage

Probe type

Single-ended

Single-ended

Included accessories

(orderable separately)

N7021A - Coaxial pigtail probe head (qty 3): 8”

N7022A - Main cable: 48”

N7023A – 350 MHz browser: 45”

Compatible, not included

N7032A 4 GHz browser for 0603 and 0805 packages (inch code)

N7033A 5 GHz browser for 0201 and 0402 packages (inch code)

1250-4403 Rotating SMA adapter

Output impedance

50Ω

50Ω

Extended temperature range

N7021A main cable, N7022A pigtail probe head: -40° to + 85° C

If your sample rate is not fast enough, you won’t be able to see your signal accurately on the oscilloscope screen. Sample rate is the number of samples an oscilloscope can acquire per second. This determines the resolution of your waveform. Read on to learn why.

 

The Basics

A sample is a single value at a point in time. You could think of a sample like one piece in a puzzle. The more pieces you assemble over time, the more apparent and complete the picture becomes. 

 

Oscilloscope sample rate: Puzzle

 

But unlike a puzzle, reconstructing a waveform on an oscilloscope is not solely dependent on the number of samples that are strung together. The speed at which you sample matters too. A puzzle is a static picture. Therefore, it doesn’t matter how long it takes you to assemble a puzzle – the result will still be a complete picture in the end. However, electric waveforms change with time. So, to get a complete picture of the waveform, we need to sample fast enough to capture it. That is why we talk about the specification in terms of a rate. We need a fast sample rate to properly display our device’s signals on our test equipment.

 

We know from Harry Nyquist that we need to take equally spaced samples of a signal at at least twice the rate of the signal’s highest frequency component to represent that signal without errors. 

 

Fsampling 2Fsignal

 

This definition is given as a minimum requirement for proper sampling. You want your oscilloscope to provide more than just a minimum requirement.

 

Oscilloscope Sampling

There are two key oscilloscope specs that determine if your signal will be displayed properly on screen: bandwidth and sample rate. In my previous blog “What is Bandwidth and How Much Do You Need,” we discussed the importance of bandwidth. From that blog you’ll know that without enough bandwidth, you’ll have an attenuated and distorted signal. But, it’s also important to know that without enough sample rate, you will be without all the waveform information that is necessary to display the frequency of your signal, exact rise and fall times, the height and shape of your signal, and any glitch or anomaly that may be occurring.

 

When you probe your device and connect it to an oscilloscope, you are sending an analog signal into the oscilloscope. Then, the scope samples and digitizes the signal, saves it in memory, and displays it on screen. 

 

Oscilloscope sample rate: Simplified block diagram of signal flow from a DUT through an oscilloscope.

Figure 1. Simplified block diagram of signal flow from a DUT through an oscilloscope.

 

The default sampling setting on your Keysight oscilloscope is automatic in real-time sampling mode. Automatic sampling will select the sample rate for you. The scope will choose the highest sampling rate possible, using as much memory as necessary to fill the display with your waveform information. In real-time sampling mode, all the samples of the waveform are taken from one trigger event and are evenly spaced in time. (If you aren’t familiar with the term trigger, that is basically the event that time-correlates your device’s waveform within the oscilloscope, allowing the waveform to be steadily displayed on screen.) The scope may also apply interpolation to fill in gaps between samples. 

 

If you don’t want the oscilloscope to select the sample rate for you, most oscilloscopes allow you to set the sample rate yourself. If you set the sample rate yourself, remember: two times the frequency is the absolute minimum rate you should use. When it comes to oscilloscopes, I recommend choosing a sample rate faster than this. Usually choosing a sample rate that is 3 to 5 times the bandwidth of the oscilloscope will give you a high-enough sampling rate to capture the details of your signal, including its frequency of oscillation and the rise times of your waveforms. You need a sample rate that will provide enough detail to see any unexpected glitches or anomalies.

 

The more samples you have in each period, the more signal detail you'll capture.

 

One last thing to double check is the sample rate of the oscilloscope when all channels are turned on. Typically, when multiple channels are in use, the sample rate is split up among the channels. If you are using more than one channel, you’ll want to make sure the sampling rate is still sufficient.

 

The Specs You Need to Know

While bandwidth is the number one oscilloscope specification, sample rate is a close second. The oscilloscope sample rate determines the amount of waveform information captured and displayed on screen. You need a sample rate that will accurately show all aspects of your signal including its standard shape, accurate rise times, and glitches. You could be missing vital design flaws without being able to view a glitch, or you could waste hours trying to determine why your signal looks differently than you expected just because your scope was under sampling. 

 

To learn about the other need-to-know oscilloscope specs to set you up for successful measurements, check out the Basic Oscilloscope Fundamentals application note.

If you are using an oscilloscope, make sure you are using the right bandwidth! Choosing the wrong amount could adversely affect your measurement results. Let’s look at what oscilloscope bandwidth is and why you need just the right amount. 

 

What is Bandwidth?

 

Bandwidth is often regarded as the single most important characteristic of an oscilloscope. Measured in Hertz, the bandwidth of your oscilloscope is the range of frequencies that your oscilloscope can accurately measure. Without enough bandwidth, the amplitude of your signal will be incorrect and details of your waveform might be lost. With too much bandwidth, you will capture excessive noise, providing you with an inaccurate measurement. Here’s why: 

 

You can think of an oscilloscope like a low pass filter, meaning it will only pass frequencies from 0 Hz up to a specified frequency. An oscilloscope’s bandwidth is specified as the 3 dB down point of the filter. What the heck is a 3 dB down point? Read on. 

 

Download the "6 Essentials for Getting the Most Out of Your Oscilloscope" eBook.

 

Low pass filters allow signals to pass through them at full amplitude until the signal frequency approaches the high end of the frequencies that the filter can pass. Then a filter attenuates signals passing through them until the signal’s amplitude is dampened to nothing. When the signal is attenuated by three decibels (3 dB), that is the cutoff point for an oscilloscope’s bandwidth specification. If you aren’t familiar with decibels, the 3 dB down point is when the amplitude of a sine wave is 70.7% of its actual height. Look at the diagram below to visualize the frequency response of a low pass filter, depicted in blue.

 

Oscilloscope bandwidth: Frequency response of a low pass filter, depicting the 3 db down point and cutoff frequency.

Figure 1. Frequency response of a low pass filter, depicting the 3 dB down point and cutoff frequency.

 

So, if you have an oscilloscope that has a bandwidth of 200 MHz, you know that the cutoff frequency of that oscilloscope’s filter is 200 MHz. Why does this matter for your measurements? 

 

Too Little Bandwidth

 

You can see from Figure 1 that if you are measuring a signal that has a higher frequency than the cutoff frequency, you’ll either see an attenuated and distorted version of your signal or not much of a signal at all. Even measuring a signal as fast as the bandwidth of the scope is not a good idea. Measuring a 200 MHz signal on a 200 MHz oscilloscope will not provide you with the best representation of your signal, as the filter has already begun to roll off and distort your input.

 

Measuring with too little bandwidth will provide distorted results

 

Here is the rule of thumb for choosing the right bandwidth:

  • Digital signal measurements: five times higher bandwidth than the fastest digital clock rate in your system
  • Analog signal measurements: three times higher bandwidth than the maximum signal frequency on an oscilloscope with a flat frequency response

 

For more detail on these rules, read Evaluating Oscilloscope Bandwidths for Your Application.

 

So why not just use an oscilloscope with the highest bandwidth possible?

 

Too Much Bandwidth

 

Oscilloscopes can capture environmental noise. Oscilloscopes also add noise to your signal from filtering, processing, and digitizing (though a high-quality oscilloscope will do all of this properly and add less noise than a poorly-designed scope). And noise occurs at all frequencies. So if you have a 200 MHz oscilloscope, that scope is only going to show noise up to 200 MHz. But, if you have a 33 GHz oscilloscope, it will add noise to your measurement through its entire measurement range up to 33 GHz, regardless of the frequency of your signal. 

 

Increasing bandwidth increases noise

 

If you want to measure a 50 MHz signal, a 200 MHz oscilloscope will give you plenty of bandwidth to clearly display your signal without attenuation and filter distortion but not so much that it adds high frequency noise content to your measurement.

 

Insider tip: If all you have access to is a high bandwidth oscilloscope, but you are measuring low frequencies, turn on hardware filters in the oscilloscope to eliminate that high frequency noise and get a cleaner measurement.

 

The other reason why you probably don’t want to buy the highest bandwidth oscilloscope out there is price. The higher the bandwidth, the higher the price. If you are worried the bandwidth you need today will not be enough for future measurements, look for an oscilloscope that lets you upgrade the bandwidth with a software license. That way you can buy the bandwidth you need now and upgrade later without having to purchase a new oscilloscope or send it in to the factory for a hardware update. (Most Keysight oscilloscopes can be bandwidth upgraded with a software license for this very reason.)

 

Demonstration

 

Don’t be afraid to be the Goldilocks of bandwidth. Did she settle for the porridge that was too hot or too cold? No. She went for the one that was just right. And lucky for us, we won’t be eaten by bears if we set our bandwidth to just the right amount. Here is an example of how even a simple sine wave can be falsely represented on an oscilloscope without the right bandwidth.

 

In this demonstration, I am measuring a sine wave oscillating with a frequency of 80 MHz and a peak-peak voltage of about 2 volts.

 

Oscilloscope bandwidth: Measuring a sine wave oscillating with a frequency of 80 MHz and a peak-peak voltage of about 2 volts

 

I am using an 8 GHz oscilloscope. This is an excessive amount of bandwidth for an 80 MHz signal. The rule of thumb for analog signals is to use about 3 times the frequency of the signal. While this measurement doesn’t look horrible, let’s see how much better it can get when I apply the rule of thumb.

 

With only 240 MHz of bandwidth, look at how much cleaner my measurement is.

 

Oscilloscope bandwidth: Clean measurement with only 240 MHz of bandwidth

 

If I just want a quick check on the basics like voltage and frequency, the difference might not be crucial. But if I’m proving the quality of my design or attempting to pass strict performance or compliance specs, I would want the best (and cleanest) representation of my signal.

 

Now, I’ll decrease the bandwidth even further. As I mentioned earlier, you shouldn’t measure a signal at the bandwidth of the oscilloscope. The signal will be passing right through the 3 dB down point of the filter.

 

Oscilloscope bandwidth: Bandwidth decreased further

 

Here I’m measuring my 80 MHz signal with 80 MHz of bandwidth. You can see that the voltage is decreased from 1.92 V to 1.36 V. This is 70.8% of the voltage we should be seeing. The signal is attenuated by the filter. 

 

To demonstrate the effects of the filter above the cutoff frequency, here is my measurement of the same signal with only 75 MHz of bandwidth. The signal is attenuated even further to 161 mV. The period of my measured signal is displayed as 12.74 ns. This would imply that the frequency of my signal is only 78 MHz, which we know to be false.

 

Oscilloscope bandwidth: Measure the same signal with only 75 MHz of bandwidth

 

And here I’ve measured the same signal again with only 70 MHz of bandwidth. It barely looks like there is a signal at all.

 

Oscilloscope bandwidth: Measured same signal with only 70 MHz of bandwidth

 

You can see how dramatically the signal is attenuated when you try to measure a signal with frequency beyond the bandwidth of the oscilloscope.

 

Summary

 

Bandwidth is the most important characteristic of an oscilloscope

 

While there are many important features of an oscilloscope that you’ll need to evaluate before choosing one for your measurements, clearly bandwidth is the number one spec that you must check before any other. If you don’t have enough bandwidth you’ll see distorted or attenuated signals, giving you inaccurate measurements. If you have too much bandwidth, your measurements will be noisier than necessary. You have to choose a bandwidth that can support a clean and accurate representation of your test signals.

 

Now that you understand why bandwidth is the most important characteristic of an oscilloscope, check out Basic Oscilloscope Fundamentals to learn the other important oscilloscope characteristics and how to use an oscilloscope.

 

Picture the heart rate monitor that you always see next to hospital beds on “House” or “Grey’s Anatomy.” You hold your breath as you wait for the next beep and jump of the line on the screen, and you dread the flat line as the TV show reaches its apex.


Well, when my family asks me what I do for a living, this is how I describe an oscilloscope. But instead of displaying the signal of a human heart, oscilloscopes show the heartbeat of electronic devices. They give us all kinds of insights into whether or not an electronic device is operating correctly, allowing us to check its vitals.

 

Download the "6 Essentials for Getting the Most Out of Your Oscilloscope" eBook.


The vitals of our devices could be voltage or current. And just like we don’t want our hearts to beat too fast or too slow, we want those voltages to oscillate at the right pace or frequency. We all know heart murmurs are bad. Well, we don’t want any glitches in our electrical signals either, and an oscilloscope can help us find them. Having insights like this into your electronic devices allows you to validate it is operating as expected. And if it’s not, oscilloscopes help you diagnose the problem and correct it. If you are an electrical engineer, chances are you could use an oscilloscope ─ whether you’re a test engineer or student or work in manufacturing, repair, research, or development.

1000 X Series Oscilloscopes1000 X-Series oscilloscopes making a variety of measurements.

 

Oscilloscope Basics

The basic operation of an oscilloscope displays voltage versus time, with voltage on the vertical axis and time on the horizontal axis. This allows you to double check that your device’s signal is as you expect, both in magnitude and frequency. And because oscilloscopes provide a visual representation of the signal, you can view any anomalies or distortion that might be occurring. But before you start testing, there are some things for you to consider.

 

Oscilloscope displayOscilloscopes display voltage on the vertical axis and time on the horizontal axis.

 

Oscilloscopes come in many flavors. You want to select an oscilloscope with the right bandwidth, signal integrity, sample rate, and channel inputs. You also want to make sure it is compatible with any applications and probes you may need. Here is a list of some of the features you should check when deciding what oscilloscope to use:

 

  • Bandwidth – The range of frequencies the oscilloscope can measure accurately. Oscilloscope bandwidths typically range from 50 MHz to 100 GHz.
  • Sample Rate – The number of samples the oscilloscope can acquire per second. The greater the samples per second, the more clearly and accurately the waveform is displayed.
  • Signal Integrity – The oscilloscope’s ability to represent the waveform accurately. This is a topic I’m particularly passionate about and you’ll find me writing about this a lot. You wouldn’t want a heart rate monitor that displays incorrect information. It would do no good to declare a patient dead whose heart is still beating. The same is true for your device under test. You wouldn’t want to declare your device is malfunctioning and spend weeks trying to find the root cause when there isn’t actually a problem.
  • Channels – The input to the oscilloscope. They can be analog or digital. There are typically 2 to 4 analog channels per oscilloscope.
  • Probe Compatibility – A probe is the tool used connect the oscilloscope to your device under test. There are a large variety of passive and active probes, each made for specific use cases. You want an oscilloscope that is compatible with the type of probe you need for your specific tests.
  • Applications – Signal analysis, protocol decode, and compliance test software can greatly reduce the time it takes to identify and capture errors in your designs. Analysis software can help you find and evaluate jitter, perform Fourier transforms, create eye diagrams, and even identify and quantify crosstalk. Protocol decoding software can identify digital packets of information, trigger on different packet conditions, and identify protocol errors. Not all oscilloscopes are compatible with every application.

 

What are Oscilloscopes Used for?

Now that you’re armed with the lingo, you’re ready to get going. The most basic testing only requires an oscilloscope with 50 to 200 MHz of bandwidth, a passive probe, and sufficient sample rate, signal integrity, and channel inputs.


Armed with these basics, you can spot-check your printed circuit boards (PCBs) to find faulty parts, noisy power lines, shorts, and I/Os (inputs and outputs) that are not working; dive into different trigger modes to search for runts, glitches, and timing errors; and capture signals and data to prove the quality of your designs. Some basic oscilloscopes even provide Bode or frequency and phase response analysis. And this is just the start.

 

Frequency response analysis on InfiniiVision oscilloscopeFrequency response analysis performed on an InfiniiVision oscilloscope.

 

Oscilloscopes are versatile and widely used instruments. Automotive technicians use oscilloscopes to diagnose electrical problems in cars. University labs use oscilloscopes to teach students about electronics. Research groups all over the world have oscilloscopes at their disposal. Cell phone manufacturers use oscilloscopes to test the integrity of their signals. The military and aviation industries use oscilloscopes to test radar communication systems. R&D engineers use oscilloscopes to test and design new technologies. Oscilloscopes are also used for compliance testing such as USB and CAN protocols where the output must meet certain standards.

 

Get Started

Now that you know what an oscilloscope is and some of the crucial oscilloscope specs, it’s time to get testing. So throw on your scrubs (or maybe an ESD strap instead) and get started!


To learn more about how to operate an oscilloscope and understand measurement fundamentals, you can read the Basic Oscilloscope Fundamentals application note.

 

Have you ever set up your oscilloscope without a proper trigger? If so, you probably experienced something a little bit like this:

 

In this case, I had an edge trigger and the level was set above my waveform.  The oscilloscope could not find any waveform data at that threshold and therefore, didn’t know what waveform data to display on screen.

When you have a trigger set up, the oscilloscope is looking at the acquisition data to see when your trigger conditions are met. If they are met, the oscilloscope will display the waveform data centered around the trigger event, thus stabilizing your display.  

Triggering

The easiest way to set up a quick trigger and stabilize your display is to hit Auto Scale.  That will take care of your vertical and horizontal scaling, and sets up the most common trigger type (Edge) at an appropriate level. This gets you straight to basic troubleshooting.

 

Below is a trigger diagram showing the conditions for Edge trigger:

Trigger Diagram

Figure 1- edge trigger diagram

 

But triggering isn’t just used to obtain a stable display. It can also help you find events in your waveform. And there are many different triggers to help you find many kinds of events – even the tricky, hard to find events like glitches, runts, patterns, and sequences.  Keysight’s Infiniium oscilloscopes provide both hardware and software triggers.  Hardware triggers are quick and address the most common use cases. They are looking for events happening in real-time acquisition data.  Software triggers are used when the event you want to trigger on is just too complex for hardware alone.  To perform a software trigger, first the oscilloscope triggers in hardware to acquire the waveform data.  Then analysis and event searching happens in software before the waveform is displayed for that trigger. Perhaps a more accurate name for software triggering is event identification software. 

 

Below, you’ll find a quick reference guide for all the hardware and software triggers available on Keysight’s Infiniium oscilloscopes.  This will help you understand what triggers are available and determine what triggers you want to use when.

Hardware Triggers:

Trigger Type

What it Does / When to Use

Edge

looks for slope and voltage level of the selected source - mostly used for general purpose viewing and trouble shooting

Glitch

looks for a pulse that is narrower than other pulses in your source - used to capture infrequent glitches

Pulse Width

looks for a pulse that is either wider or narrower than other pulses in your source based on the pulse width and polarity you set - used to capture pulses that are too short or too long in time

Pattern/State

looks for a user specified pattern - used when you want to find a specific pattern across analog and/or digital channels

Runt

looks for a pulse that is smaller in amplitude than other pulses with low and high thresholds - to find pulses that are too low in voltage

Setup and Hold

looks for violations of setup time, hold time, or both setup and hold time based on a reference clock waveform

Edge Transition

looks for edges that do not rise or fall across two voltage thresholds in the amount of time you specify - used to find violations in rise/fall time

Edge Then Edge

looks for the two events you specify delayed by the number of events or time you set

Timeout

looks for a pulse that is lasting too long either at a high or low level - to find potential timeout errors

Window

looks for an event of the waveform exiting, entering, or remaining outside a voltage range as specified to use when you want to view a waveform either within or without certain thresholds

Protocol

looks for certain packets or patterns in protocol-based data. (Hardware protocol is only available on some Keysight oscilloscopes, the S-Series being one of them, with others performing protocol trigger in software).

Sequence

any two of the above performed in sequence used when you want to capture the signal based on two trigger events

 

Software Triggers (Available with InfiniiScan N5414B):

Trigger Type

What it Does / When to Use

Measurement

After hardware triggering and the waveform data is acquired, the specified measurement is performed, and then if the measurement condition is met, the InfiniiScan trigger condition is set to true and the waveform is displayed on screen

Zone Qualifying

create up to 8 zones and combine them with logic expressions to set triggering conditions

Generic Serial

capture packets of customized protocols or generic patterns

Non-monotonic Edge

capture small glitches or edges that may be hidden by hysteresis

Runt

capture runts that they may be hidden by hysteresis

 

I’m hoping as you advance past Auto Scale and try out a couple of these triggers, you’ll be a wiz and won’t even need this lookup table!

 

So how do you set up these different triggers? Easy.  Here are the two simple steps:

  1. Choose the Trigger Menu, then select Setup
  2. Choose the trigger you want from the list on the left and set your desired conditions

Now you’re rockin’ and rollin’! You’re ready to find all sorts of different anomalies that could exist in your waveforms and find the root causes of your malfunctioning DUT faster.  

 

If you have any interesting test conditions in which you used one of these triggers, we’d love to hear about it in the comments. Happy Triggering!

The latest Infiniium software release (for Infiniium oscilloscopes and Infiniium Offline on your PC) includes a handful of new and improved tools to help you make more efficient measurements and documentation.

These updates include:

  • MIPI SPMI Protocol Decode
  • Generic Raw Decode for PAM-4 and NRZ
  • Symbolic Decode added to ARINC 429 and MIL-STD-1553 protocol decode 
  • Segmented Memory improvements
  • Measurement Reports
  • S-Parameter Viewer
  • Windows 10 Support

 

MIPI SPMI Protocol Trigger and Decode – N8845A

If you’re designing mobile devices, our new SPMI (System Power Management Interface) protocol decode license might interest you. SPMI is used to communicate from power controllers to one or multiple power management chips with up to 4 masters and 16 slaves on one bus. SPMI allows you to reduce the number of pins on your power controllers, reducing the size of your mobile designs. With Keysight’s SPMI protocol decode option you can decode and debug these designs. Like I always say when it comes to protocol decode software, have the oscilloscope decode for you so you can get right to the fun part - analyzing and debugging.

Figure 1 - MIPI SPMI protocol decode

 

Generic Raw Decode

You may have a proprietary bus or customized protocol that others may not have defined a specific protocol decode for. This means you don’t have the option of buying a convenient protocol decode license that will trigger and decode your serial bus, group bits, label packet types, and flag errors for you. However, you can still get the binary data extracted from your analog waveform. With Generic Raw, you can decode your NRZ and PAM-4 signals so you can process and analyze the data yourself. This software extracts the raw bit data from the analog signal based on the clock recovery and thresholds that you set. Generic Raw has one mode for NRZ* signals and another for PAM-4** signals.

Figure 2 - Generic Raw PAM-4 decode

 

Symbolic Decode – N8842A

If you’re working with ARINC 429 and MIL-STD-1553 protocols, this update is for you. How many of us sit with our protocol binders in our lap to translate the Hex values to meaningful English? It’s time to toss that binder in a desk drawer. Load your .xml file into the oscilloscope to view your protocol decode in ASCII instead of Hex. Look at the examples below to see the two versions side by side.

ARINC 429 protocol decode:

Figure 3 - ARINC 429 decode in Hex

 

ARINC 429 protocol decode with symbolic decode:

 

 Figure 4 - ARINC 429 decode in ASCII

 

 

Segmented Memory Updates

Segmented memory is a great way to make the most of your oscilloscope’s memory, especially if you have specific events of interest separated by long amounts of time that you don’t really care about. An example of this is a serial bus. You’ll be looking at a waveform with packets of data separated by dead time. You can acquire waveform data just around the trigger conditions you set – for example, a specific packet type or an error. Then you can view this same packet type as it changes over time, comparing the packets captured in each acquisition. Now segmented memory has been improved to make your life even easier with the following:

  • Auto Play - automatically play through all the segments after acquisition is completed
  • Time between segment playback is reduced to zero – optimized performance saving you time
  • Persistent data is preserved – you can view all your segments laid on top of each other to see how your signal changes between packets in one view
  • Measurement Log – track the changes in measurements over the number of acquisitions you specify

 

 

Measurement Reports

 

Have you ever had to compile measurement reports to keep records of exact test conditions, equipment settings, and measurement results? Now, the oscilloscope can do it all for you in a couple clicks. No more copying and pasting screenshots, pulling together separate setup files and recording the software versions, and organizing them into your favorite text editor. The 6.0 Infiniium software now provides a way to generate hassle free reports that include all of the information you’d want to record and keep in your archives for proof of your test results.

 

Measurement reports provide, in a single file, measurement results and screenshots, plus all the information about your oscilloscope setup including:

 

  • Oscilloscope configuration with model number and software version
  • Calibration status of the frame and individual channels
  • Acquisition settings
  • Horizontal settings
  • Bandwidth limits and filter type
  • Vertical and channel settings
  • Trigger setup

 

You can save your report as PDF or as MHTML (*.mht) format files. MHTML is a webpage archive format that includes images and html all in one file so you don’t have to save images and text based content separately.

 

S-Parameter Viewer

If you are using InfiniiSim to apply transfer functions to your waveform – useful when you want to model the effects of a probe or RC circuit on your design – there is now an option to view the s-parameters. Being able to view the s-parameters before applying it to your waveform can be a nice sanity check before you end up spending hours trying to understand why your circuit behaves so unexpectedly because you accidentally uploaded the wrong file (it’s happened to the best of us).

 

Figure 5 - S-Parameter Viewer

 

Windows 10

Infiniium software now supports Windows 10. If you are running Windows 10 on your PC, Infiniium Offline is now compatible! For a free trial of the Infiniium software, click here.

_____________________________________________________________________________________________________________________

*Standard with SDA option

**Requires PAM-4 Compliance App and SDA option

If you are working on embedded designs such as automotive controllers, sensors, actuators, avionics, weapons systems, transmitting uncompressed audio and video data, or other chip-to-chip communications, you are probably using protocols and need a way to decode serial buses.

Protocol decode is the process of translating an electrical signal from a serial bus into meaningful bit sequences as defined by the standards of the protocol being analyzed. As we use serial buses in our designs to communicate from one device to another, we often need to debug our designs and verify we are sending the messages, or bit packets, that we intend to send.

One way to do this is to manually decode the signal. To do this, first you must capture the signal on an oscilloscope. Next, break apart the signal into one bit time slices and count the stream of ones and zeroes. Then group the sequence of bits and decode by the specifications of the protocol you are using. An example of this process is shown in the image below. This example is of a CAN bus.

Figure 1 - Decoding a CAN bus by hand

While this exercise might make an interesting learning experience for engineering students, this is a tedious and obsolete way to decode. Now days, you can decode your serial buses using a protocol analyzer or protocol decode software on your oscilloscope. This oscilloscope software will count the bits and compartmentalize the data into meaningful packets based on the definitions of the protocol you are using. With many oscilloscopes, you can even view the protocol decode results in a lister window.

 

Keysight InfiniiVision and Infiniium oscilloscopes display the original waveform, a time aligned decode trace for the data captured on screen, and a lister which is a text based table. The lister displays all the data packets, the time at which they occurred, the type of packet, and other relevant packet information specific to the protocol in use. Additionally, the lister will include the error type if an error was detected. Below is an example of CAN protocol decode performed on an InfiniiVision oscilloscope:

Figure 2 - CAN Protocol Decode performed by InfiniiVision oscilloscope

To find errors by hand you’d have to cross reference the packets you decoded with the packets you were trying to send at that point in the sequence and check if you have errors. Plus, you would be limited to the part of the waveform you could view on screen. As you can imagine, this is tedious. However, protocol decode software can find errors for you. Plus, with Keysight oscilloscopes, you can even trigger on errors or a specified packet type so you can easily find and analyze the events that interest you.

If you are looking for an entry level, affordable oscilloscope, the Keysight InfiniiVision 1000X-Series oscilloscopes have the ability to perform protocol hardware trigger and decode of I2C, SPI, UART/RS-232, CAN, and LIN buses.

1000 X-Series Oscilloscope

Figure 3 - Keysight 1000X-Series oscilloscope

If you are looking for an oscilloscope with higher bandwidth and additional capabilities, the Infiniium oscilloscopes offer several more protocol decode options including 8B/10B, ARINC 429, MIL-STD-1553, CAN, CAN-FD, LIN, FlexRay, DVI, HDMI, I2C, SPI, RS-232/UART, JTAG, several MIPI protocols, PCI Express, SATA/SAS, SVID, USB2.0, USB 3.0, USB 3.1, USB PD, and eSPI.

This variety of protocol decode addresses several industries. For example, the automotive industry often use CAN (Controller Area Network), CAN-FD (Controller Area Network – Flexible Data-rate), LIN (Local Interconnect Network), and FlexRay. These are the main buses used for automotive controllers, sensors, and actuators used throughout our vehicles. Designers in this space will want to be able to debug the physical layer of their designs. And because it is so important to have reliable systems in our automobiles, it is important to have reliable decode software.

Other buses that are important to have properly tested and reliable designs are ARINC 429 and MIL-STD-1553. These are often used in military equipment such as avionics, weapons systems, or ground vehicles.

As USB (Universal Serial Bus) has become so popular and continues to advance quickly, it is important to have the ability to decode both legacy USB protocols such as USB 2.0 and the newer USB protocols such as USB 3.1, and USB Power Delivery.   USB is everywhere now with its use in smartphones, computer peripheral devices, cameras, power chargers for hand held devices, and drones.

High definition televisions and displays usually use HDMI (High Definition Multimedia Interface) protocol for transmitting uncompressed audio and video data. DVI (Digital Visual Interface) is also used to transmit digital video.

Buses used for Short distances with integrated circuits include I2C and SPI.

Serial buses are used everywhere. With the ability to set up the decode in less than 30 seconds, set up specialized triggers and search on specific packet types or errors, and expand the amount of useful data captured with segmented memory, oscilloscopes make decoding serial buses much more efficient than decoding by hand. Protocol decode software on oscilloscopes help you quickly move from decoding to analysis and debugging.

If you didn’t get everything you wanted for Valentine’s Day, check out the latest Infiniium oscilloscope firmware (version 5.75) – it may have what you wished for. Its updates include a front panel macro recorder, the ability to load and save .mat files, multiple undo/redo capabilities, and more!

The front panel macro recorder allows you to record all of your actions with the keyboard, mouse, and touchscreen so that you only have to go through your set ups once – you can save and playback the macro record or load it to be executed as a set of SCPI commands. It retains up to 500 commands.

Macro Recorder

If you use MATLAB, you’ll enjoy the ease of saving waveform data as a .mat file and the ability to open a waveform .mat file as a memory waveform. Remember, Infiniium allows you to open and view up to 8 waveforms at once.

waveform files

Perhaps my favorite addition to the software is the new Undo and Redo capability. If you’ve ever accidentally clicked on a setting that you didn’t like or wish you could go back one step, two steps, five steps, etc. you can now do that with Undo/Redo. You can either step back through your changes one at a time or use the drop down menus to undo or redo multiple steps at once. Too bad we don’t have an Undo/Redo for any Valentine’s Day dates-gone-wrong (unless you’re spending the evening with your oscilloscope – then Keysight has your back)!

Scope controls

If you are testing PAM-4, check out the latest updates to our PAM-4 Compliance Application N8836A. Free trial here. We have added new Continuous Time Linear Equalizer for eye height, width, and symmetry mask width, new J4 jitter support, and PRBS13Q test pattern.

In addition we have added more bit error rates for jitter analysis (J2, J4, J5, and J9) and more hardware serial trigger data rates:

  • 2.4882 Gb/s
  • 3.7125 Gb/s
  • 4.455 Gb/s
  • 4.640 Gb/s
  • 5.5688 Gb/s
  • 5.94 Gb/s
  • 7.425 Gb/s
  • 9.95328 Gb/s
  • 12.440 Gb/s

If any of these look like the Valentine’s wish you were hoping for, update to latest software to your Infiniium oscilloscope & PC, or try the software for free.

Download Infiniium software version 5.75

Previously, I wrote about the hardware comparison between the Keysight S-Series oscilloscopes and the Rohde & Schwarz RTO2000 oscilloscopes. In that review, we saw that the S-Series offered better hardware with much higher ENOB and lower noise, you can read the full article here.  Excellent hardware is nice, but you are probably also looking at other features when you are trying to find the right scope for you.  So let’s take a look at some of the other aspects of these two oscilloscopes that we found in our comparison.

 

Let’s start with the basics.

 

The RTO2000 goes up to 4 GHz bandwidth while the S-Series goes all the way up to 8 GHz bandwidth.  In terms of list price, they are very similar.

Keysight   S-Series

US List Price

R&S RTO2000

US Price (4-channel models)

500 MHz

$17,709

600 MHz

$17,455

1 GHz

$21,251

1 GHz

$21,110

2 GHz

$25,805

2 GHz

$25,480

2.5 GHz

$28,335

3 GHz

$28,555

4 GHz

$37,442

4 GHz

$36,955

6 GHz

$53,634

--

8 GHz

$68,813

--

 

Additionally, the S-Series is easy to upgrade.  Keysight offers bandwidth upgrades, memory upgrades, and MSO upgrades in software which means there is little to no downtime with your S-Series oscilloscope.  The RTO2000 requires upgrades in hardware for each of these (bandwidth, memory, and MSO), which means you’d have to send your scope in, wait for the hardware to be installed, and wait for it to be shipped back to you. 

 

Standard memory is also similar between oscilloscopes.  S-Series and RTO2000 both have 100 Mpts with 2 channels and 50 Mpts with four channel operation. However, the RTO2000 does offer one additional step which gives you 200 Mpts with 1 channel operation.

 

Both oscilloscopes have the same memory upgrades up to 800 Mpts.  But again, the RTO2000 offers one additional upgrade that provides 1 Gpts with 4 channels and 2 Gpts with 2 channels.  But keep in mind that these are hardware upgrades for the RTO2000 and software upgrades for the S-series.

 

Maximum sample rate on the S-Series is 10 GSa/s with 4 channels and 20 GSa/s on 2 channels on all bandwidth models.  To get this same maximum sample rate with an RTO2000 you have to purchase the 4 GHz model.  All other RTO2000 bandwidth models (from 600 MHz – 3 GHz) only have 10 GSa/s on each channel. 

 

Now that we’ve seen how the basic specifications compare, let’s take a look at the GUI.  We have heard a lot of customer feedback about the oscilloscope display. We know you want the entire display available to view your waveform so you can get a large, detailed view of your signal.  That’s why all of our menus, results tabs, and drag-and-drop measurements can be minimized.  You can use the S-Series’ full 15 inch display to view your waveform.  In comparison, the RTO2000’s display is 38.3% smaller than the S-Series’ display.  Additionally, they have a side menu that cannot be minimized, so the available area you can use to view your waveform is even smaller.

Figure 1 - these screenshots are to scale

 

There are also many instances where it takes several more clicks on the RTO2000 than the S-Series to make basic measurements.  An example of this is a voltage peak-peak measurement. On the S-Series, you don’t have to go into any special drop downs or pop-up menus to get this measurement. Just drag and drop from the vertical measurements options always available on the edge of the screen.  Measurements like Vpp, Vmax, Vmin, Amplitude, Vrms, and a variety of time measurements are only one click away on the S-Series.  As to overall GUI experience, I suggest you try out both oscilloscopes to find out what suits you better. I felt that the GUI on the RTO2000 was difficult and confusing; however, as a Keysight employee using the Infiniium GUI every day, I may be biased. Ultimately, GUI preference is up to the user, so try them out.  Download a free trial of the Keysight Infiniium GUI.

 

The S-Series also has the largest range of oscilloscope applications and probes to help you measure and analyze your signals. These include 16 compliance tests available on S-Series that are not available with the RTO2000. 

Protocol Decode options available on both the S-Series and the RTO2000:

  • 8B/10B
  • I2C
  • SPI
  • MIPI CSI-3 (M-PHY)
  • USB 2.0
  • CAN
  • LIN
  • FlexRay
  • I2S
  • MIL-STD-1553
  • ARINC 429
  • 10/100 Ethernet
  • UART/RS-232
  • MIPI RFFE
  • CAN-FD

 

But it doesn’t stop here for the S-Series.  There are an additional 15 protocol decode capabilities that are only available on the S-Series:

  • DVI
  • HDMI
  • JTAG
  • MIPI UniPro
  • MIPI DigRF v4
  • MIPI LLI
  • PCIe Gen1 and 2
  • SATA/SAS
  • SVID
  • USB 3.0
  • USB 3.0 SuperSpeed Inter-Chip (SSIC)
  • USB 3.1
  • USB-PD
  • Universal Flash Storage (UFS)
  • eSPI and Quad eSPI

 

There are only 4 protocol decodes available on RTO2000 that are not available with S-Series.  They are:

  • SENT
  • Manchester
  • MDIO
  • SpaceWire

 

Additionally, there are 16 compliance tests that are available with S-Series that are not available with RTO2000. You can see the side-by-side comparison in the table below.

Table 1 - Compliance App Comparison

 

Another important factor in in your oscilloscope purchasing decision is probing. You know that your measurements are only as strong as the weakest part of your measurement setup, and that includes probes.  So having the right probes is key for making the best measurements. With that in mind, let’s look at the probing options for each oscilloscope. There are about 100 Keysight probes compatible with the S-Series. The RTO2000 lists about 18 compatible probes.

 

This difference highlights some major gaps in the RTO2000 probe portfolio:

  • No low noise, low attenuation probe for measuring small signals such as power supply noise
  • Lack of specialty probes such as extreme temperature probes, high sensitivity current probe, and power rail probe
  • Only one compatible high voltage differential probe (100MHz, 1kV), which limits their ability to make power measurements
    • Keysight offers 6 high voltage differential probes in various bandwidth and input voltage range
  • No high bandwidth, 50 Ohm terminated, zero impedance passive probe

 

This means that you can’t make sensitive power integrity measurements that usually need mV of sensitivity and you don’t have the ability to measure supply drift, periodic and random disturbances (PARD), high frequency transients and noise, or perform electrical product validation at extended temperatures.  All of this can be accomplished using the Keysight N7020A power rail probe with the S-Series oscilloscope.

 

It also means you can’t make high-sensitivity, low-level current measurements. Depending on the sensitivity of your current measurements, the noise of the RTO2000 may be too high to view it on the oscilloscope even if they did offer a probe.  You can however make high-sensitivity, low level current measurements on the S-Series oscilloscope.  With the Keysight N2820A probe you can measure down to 50 uA and up to 5A. 

 

In summary, the S-Series offers a much wider solution base with the number of available applications and probes.

 

Up to this point, I haven’t said a lot that puts the RTO2000 in a good light.  So what does the RTO2000 do better than the S-Series?

 

For one, they do their digital down converting in hardware, which means their FFT has a faster update rate.  This allowed them to implement a pretty feature called spectrogram.

Figure 2 - RTO2000's Spectrogram

 

It plots frequency vs time vs power.  I can’t deny that is a feature that might be appealing to RF focused engineers, although the S-Series does offer a nice FFT solution with a number of FFT measurements like channel power, power spectral density, occupied bandwidth. Plus you can set detector types like in a spectrum analyzer, run a mask test on the FFT, and mark a specified number of peaks on screen.

 

Figure 3 - S-Series' FFT measurements

 

The RTO2000 also has 1,000,000 waveforms/second update rate.  However, you only get this update rate under very specific conditions. The oscilloscope must be set to certain settings, and you can’t have much going on besides viewing the waveform.  As soon as you add a measurement or turn on special triggering, that speedy update rate starts to plummet.  For example, in this first screenshot, you can see we have the RTO2000 operating at 1,000,000 waveforms/second, which allows us to observe an infrequent glitch.

 

Figure 4 - Signal with Infrequent Glitch viewed on RTO2000

 

With glitches like this, it is useful to turn on zone triggering in the area of the glitch so that you can capture and observe the glitch.  But when we turned on zone triggering, the waveform update rate plummets.  It drops to 360 scans/second.  In the screenshot below we have applied a zone trigger and you can see that we waited for over a minute to capture the glitch and the scope still hadn’t triggered on it yet.  So the frustration with the RTO2000 is that you might be able to see the glitch, but you might not be able to trigger on it.

 

Figure 5 - Zone Trigger Looking for Infrequent Glitch using RTO2000

 

The spectrogram and the waveform update rate were the two major features of the RTO2000 that stood out in our analysis as an advantage over the S-Series oscilloscopes. 

Our key take-aways after evaluating the S-Series and the RTO2000 side by side are as follows:

  • S-Series has excellent signal integrity, thanks to:
    • Leading edge, low noise front end design
    • System ENOB up to 8.1
    • 10 bit ADC
  • S-Series offers a wide range of measurement capabilities
    • ~100 available probes
    • ~70 protocol decode, compliance, and analysis software applications
  • S-Series is an oscilloscope will meet your measurement needs for years to come
    • You can start with a 500 MHz scope and upgrade bandwidth and capabilities as needed, all through software

 

In conclusion, the Keysight S-Series provides more reliable, accurate measurements thanks to its superior hardware design, and offers a greater number of test solutions thanks to the number of available applications and probes.

 

 

Specifications pulled from “R&S RTO Digital Oscilloscope Specifications” data sheet version 04.00, June 2016.

Measurements and analysis were made on an S804A with firmware version 5.70 and an RTO2044 with firmware version 3.30.1.1

RTO list prices found at www.testequity.com 

In today’s world, it is hard to buy a really bad oscilloscope. But how do you choose the very best oscilloscope, especially when messaging and datasheet specs look so similar between different vendors? I’m here to give you an insider view on the differences between the Keysight S-Series oscilloscopes and the Rohde & Schwarz RTO2000 oscilloscopes. 

 

The Keysight S-Series are digital oscilloscopes with models from 500 MHz to 8 GHz bandwidth. The Rohde & Schwarz RTO2000s are digital oscilloscopes with models from 600 MHz to 4 GHz bandwidth. Both oscilloscopes claim to provide incredible signal integrity.  

 

S-Series oscilloscope materials position this scope as “the new standard for superior measurements” and offering “the industry’s best signal integrity” referencing its incredible 10-bit ADC.  Meanwhile, the RTO2000 materials talk about “excellent signal fidelity” with “up to 16-bit resolution.”  So the question becomes, which of these oscilloscopes truly offers the best signal integrity?

 

First, let’s look at what the Keysight S-Series oscilloscopes offer.

 

The S-Series oscilloscopes contain an incredible amount of innovation, including hardware, software, and the GUI. For hardware innovation, Keysight designed their very own 10-bit ADC to ensure the oscilloscope could offer 10 bits at up to 8 GHz of bandwidth. This custom-designed ADC gives the S-Series oscilloscopes a system ENOB (effective number of bits) of up to 8.1 bits. Additionally, Keysight designed correction filters to run constantly within the FPGA so that magnitude and phase are continuously and properly corrected. This ensures peak-to-peak voltages and rise-times of the measured signal are accurate and consistently displayed.  Plus, the front end was designed for ultra-low noise so that all the benefits of these internal custom components are realized in the measurements.  These oscilloscopes are designed from start to finish to measure and display the signal on your test board, not any unnecessary noise introduced by the measurement system. 

 

This oscilloscope was a revolutionary introduction to the oscilloscope world bringing to market cutting edge, exclusive technology to make cleaner measurements than ever before.

 

Now, I can’t say what went into designing the Rohde & Schwarz RTO2000, but what I can do is make measurements and observe the performance of the final product. So let’s look at how the S-Series and RTO2000 performance compare.

 

For starters, the RTO2000 only has an 8-bit ADCThe S-Series’ 10-bit ADC offers 4X more resolution.  While R&S provides an ENOB specification for their ADC (>7 bits), they don’t publish their system ENOB.  So we should ask, “Why don’t they publish the system ENOB? Isn’t that what really matters when it comes to my measurements?”

 

Your measurements are only as good as the weakest link of your measurement system. So does it matter what the ADC ENOB is if the rest of the oscilloscope design reduces the effective number of bits of the system, as it inevitably will?  In the S-Series oscilloscopes the ADC has 8.7 ENOB, but the important specification is that the S-Series system ENOB is up to 8.1.  

 

To be completely transparent, here is the system ENOB for each model of the S-Series:

Keysight S-Series oscilloscopes ENOB plots

 

The ENOB on the 4 GHz RTO2000 sits right below 6 bits for the entire frequency sweep from 0 – 4 GHz.  The S-Series stays right around 7 ENOB for the frequency sweep from 0 – 4 GHz.   The S-Series has at least one more effective bit across the entire bandwidth of the oscilloscopes. This means that the S-Series has ½ the noise & distortion of the RTO2000.

 

“But what about the 16 bits that were advertised on the RTO2000?” you may ask. This is available with the RTO2000 16-bit high definition mode, option RTO-K17.  First, I suggest you get a quote for how much this option will cost in addition to the cost of the oscilloscope.  It may be upwards of $3,000 USD since the same option on their lower performance RTE digital oscilloscopes (200 MHz to 2 GHz), is priced at $3,175 USD. 

 

And here is what the RTO high definition option provides compared to the free S-Series high resolution mode:

 

Bandwidth

RTO2000 High Def Mode

S-Series High Res Mode

10 kHz – 50 MHz

16 bit

13 bit

100 MHz

14 bit

13 bit

200 MHz

13 bit

13 bit

300 MHz

12 bit

13 bit

500 MHz

12 bit

12 bit

1 GHz

10 bit

11 bit

 

 

You can see that this expensive upgrade only provides more bits than the S-Series from 10 kHz – 100 MHz. And in the plot above, you can see that it only gives you lower noise on the RTO than the S-Series in the same limited bandwidth. In all comparable high resolution modes of operation, the S-Series has lower noise. So, is it worth it to pay extra for the RTO high definition option?

 

Now let’s look at how the noise of the oscilloscopes compare, without the high resolution options turned on.  Below is a graph that shows the noise of both oscilloscopes as the vertical scale (volts on screen) is changed.

 

 

Keysight S-series clearly has much lower noise at all settings than the R&S RTO2000, meaning the signal you measure with the S-Series is much more similar to the signal on your DUT than what the RTO2000 would display.

 

Looking at the test results, my conclusion is the following: the Keysight S-Series has higher ENOB and are much lower noise oscilloscopes than the RTO2000 scopes.  The RTO2000’s signal integrity message does not hold up under testing. If you’re looking for a low noise scope with superior signal integrity, the S-Series oscilloscope is the best scope for you.

 

Coming soon will be Part 2 of the S-Series vs RTO2000 which will look at more features of the oscilloscopes, including other key specs, the GUI, probes, and applications. 

 

 

Specifications pulled from “R&S RTO Digital Oscilloscope Specifications” data sheet version 04.00, June 2016.

Measurements were made on an S804A with firmware version 5.70 and an RTO2044 with firmware version 3.30.1.1

R&S messaging pulled from R&S RTO2000 product page,  Nov. 3, 2016: https://www.rohde-schwarz.com/us/product/rto-productstartpage_63493-10790.html

As both an electrical engineer and a Halloween enthusiast, I decided to make my Halloween dreams (or nightmares) into reality with my first animated prop. I set out to make a skeleton lady that rocks back and forth as the centerpiece of our haunted house.


To build the animated skeleton, I started with:
- an old dress
- a skeleton head 
- a remote control car toy

 

First we took apart the remote control car and hooked it up to an L293D motor control IC (H-bridge circuit) and we made our first prototype with styrofoam rods.


We used a micro-controller to send control signals to the IC. The H-bridge was used to control the direction of the DC motor to enable both forward and reverse movement.

Using a microcontroller and a DC motor

After a successful dry run, we added the dress and realized we had a big mechanical problem. With the weight of the dress on top of the long rod, the torque was too much for our little remote control car motor. It could move forward, but the motor could not return to it’s starting position.


Next we tried a little servo motor. For a moment it looked like it would work, but after struggling against gravity one too many times, the gears were sheared.


The third time must be the charm, because next we tried a motor with a little more "umph" and found success! With a working prototype it was time to construct the final structure.

 

Base for the animated prop

We used balsa wood and another foam rod to keep the frame light-weight but sturdy and secured it to a heavy base for stability. We topped it with our skeleton head and some purple hair.


We dressed the frame in its vintage gown, and found we had torque issues again. In order to lighten the design, we had to remove several layers out of the dress and the hair. Then, to give the motor just a little help against gravity, we tied a string from a support behind the frame to the arm attached to the motor. This took some weight off the motor when the frame was in full extension. That way the motor wasn’t strained to operate in reverse. Ta da!!! A successful rocking skeleton lady!

 

We probed the signal going into the motor to get a better understanding of what was going on electronically.


We used the servo library in the Arduino programming language to program our IC. We adjusted the angles and time of the movement, time between movements, and repetition of movement. The signal sent to the motor is digital, 0V or 5V so we suspected that we would observe a pulse width modulated signal on the oscilloscope. Servo motors, in a nutshell, consist of gears attached to a DC motor with a control circuit which manipulates potentiometers to change the motor’s movement. The resistance of the potentiometers is adjusted to send the customized movements to the motor.


Here is what we found:


A pulse width modulated signal!


Here we have the motor hooked up to the frame and are probing the signal to the motor simultaneously so we can see how the pulses coordinate with the movement. The smaller pulses are the rock forward and the large pulses correspond to the rock back – which makes sense as it probably takes a lot more power to go against gravity then with it.

All that was left was a few finishing touches and this prop is ready for Halloween and its debut in the haunted house. 

 

Happy Halloween!!

Remember back on September 1st of this year when we posted about the new 5.60 Infiniium features? Or on September 14th when we talked about how the S-Series scopes keep getting better?  Good news: the S-Series, as well as the other Infiniium oscilloscopes, have been updated again to give you even more measurement solutions with the new Infiniium 5.70 software release.  This software release includes FFT enhancements, analysis diagrams, and new protocol and decodes to make using Infiniium oscilloscopes even easier!

 

FFT enhancements

 

You can quickly and accurately calculate transmitter power and bandwidth with these new FFT measurements:

  • Channel power- automatically calculates integrated power over a specified bandwidth
  • Power spectral density - measures normalized channel power over a specified bandwidth to quantify normalized power/noise density
  • Occupied bandwidth - calculates where 99% of the transmitted power resides in a given bandwidth to verify proper transmitter bandwidth requirements

 

We also added spectrum analyzer capabilities to the Infiniium oscilloscopes. You can specify the detector type and number of peaks that are displayed on screen.  Just choose from Sample, Positive, Negative, Normal, or Average detector type to customize the data displayed, like on a spectrum analyzer.

 

And if you are measuring out-of-bound signals, you can create a mask test for your FFT and view a list of violations that occur.  This table will tell you the number of failed waveforms, at what frequencies the violations happened, the peak amplitude, and the delta between the limit of the mask and the amplitude of the violation to give you more insight into when and how your signal is going out of the limits you specify.

 

Analysis Diagrams

 

Analysis diagrams are great if you have a complicated test setup with multiple functions running on the oscilloscope.  Analysis diagrams can help you understand the signal displayed on your screen by showing you the signal path, the functions being applied and in what order they are applied.  

 

Protocol and Decode Additions

 

The Keysight 5.70 Infiniium oscilloscope software release also provides a protocol decode and triggering bundle called AERO. This includes MIL-STD 1553 and ARINC 429, which are used in both commercial and military applications.

 

Traditionally, debugging serial buses has meant manually counting bits – which is not only tedious but prone to errors.  But Infiniium oscilloscopes with the AERO bundle you can set up your protocol decode and start debugging in under 30 seconds, so you can validate your designs quickly and easily.

 

Infiniium on Your Oscillocope and PC

As you can see, the Keysight Infiniium team is constantly updating our software to bring you new measurements, functions, analysis capabilities, protocol decode options, and more.  Another great feature of the Infiniium software is that you can get all the same capabilities and features with an identical GUI on your PC with Infiniium Offline.  You can try it for free here.

Infiniium Oscilloscopes 5.60 Software Release

The latest Keysight Infiniium oscilloscope software release, version 5.60, offers new capabilities and enhancements that make measuring and analyzing your designs easier and more comprehensive than ever before.  With additions like a new crosstalk app, bit error rate measurements for PAM-4 signals, enhancements to MultiScope, and eye contour software, you will get even more insight to your designs.  Check out what’s new with the Infiniium 5.60 release:

Crosstalk Analysis Application (N8833A/B)

Keysight Crosstalk Analysis Application (N8833A/B)

Figure 1 – Keysight Crosstalk Analysis

The Keysight Crosstalk analysis application is the industry’s first and only application to measure and analyze crosstalk.  It allows you to probe up to four signals on your board at once – this means one victim (the signal of interest) and three aggressors (signals that could be causing crosstalk on the victim).  The application can be used to analyze both NEXT (near end crosstalk) and FEXT (far end crosstalk).  With the crosstalk app, you can measure the amount of crosstalk appearing on the victim and even remove the crosstalk from measurement.  This can help you decide whether or not it is worth redesigning your board to remove the crosstalk.

New Bit Error Rate (BER) Measurements for the PAM-4 Measurement Application (N8836A)

Cumulative BER measurement setup

Figure 2 – Cumulative BER measurement setup

The addition of BER measurements to the PAM-4 measurement application software can help you quickly identify and analyze design flaws in your digital systems.   With this functionality you can measure the BER across multiple acquisitions, similar to the standard statistical BER measurement you would get from a BERT.  This is helpful for determining if your design passes a required specification.

5.6_fig3

Figure 3 – Per Acquisition BER measurement setup

In addition to this cumulative BER measurement, the oscilloscope can also measure BER per acquisition. In this mode you can look at how many errors happen in a single acquisition.  If you also have InfiniiScan and EZJIT on your oscilloscope, you can even graphically display where the errors are happening in the signal. This is helpful for understanding the errors at a more detailed level than a cumulative measurement.

measuring BER per acquisition

For example, let’s say the cumulative measurement indicates the BER is 10e-5 and that passes your design specification. But when looking at the per acquisition measurement, you find that all the errors are happening in quick succession. This could be bad news.  With four different levels in a limited amplitude range, it is likely that a bit may be lost here and there, and forward error correction (FEC) algorithms can correct standalone, faulty bits.  But when you see several errors all together – what we call burst errors – your FEC may no longer be able to handle this.  So the design has passed the general specification, but is still faulty.  Without this type of analysis tool, it would be much harder to debug such a situation.

Keysight N8834A MultiScope Enhancements

Keysight MultiScope

Figure 4 – MultiScope

The MultiScope application gives you visibility of up to 40 channels simultaneously.  You can connect 2, 5, or 10 scopes together.  This is especially helpful for power system designers, or anyone with a need to look at more than four analog channels at once.

Using MultiScope with the Infiniium 5.60 update, you can see all of your signals on and work directly from the leader oscilloscope. This release also extends the triggering capabilities available in MultiScope to the oscilloscope’s full range of triggering capabilities when triggering from the leader scope.

Eye Contour Software added to EZJIT Complete (N8823A)

Keysight eye contour software

Figure 5 – Eye Contours

Reduce your test time by using the Keysight eye contour software on any digital signal.  Originally designed for DDR4, Keysight is the only company whose eye contour algorithm has been approved by JEDEC.  This software extrapolates noise and jitter trends from the measured signal to predict how they eye will close over time, eliminating the need to run the eye test for days or weeks to find out.

Customizable Mask Editor

quickly set up a custom mask test

Figure 6 – Custom Mask Editor

Looking for a glitch? With the new custom mask editor, it is quick and easy to set up a custom mask test.  The editor provides fifteen points to drag and drop on the screen, allowing you to design the mask test you want in seconds.

Save Time with the Easy Analysis Gallery

Keysight analysis gallery shows all the available measurements

Figure 7 – Analysis Gallery

 Not sure where to find the measurement you’re looking for?  Check the analysis gallery.  It is a one-stop-shop of analysis options and measurements, represented graphically so you can easily find and run the test you’re looking for.  Your testing time is valuable, don’t spend it searching through menus to find a measurement.

And More…

There are a number of additional enhancements with the Infiniium 5.60 upgrade, including:

– CAN-FD protocol and decode is now included in the automotive bundle option (N8803C). This bundle includes protocol decoding for CAN, LIN, FlexRay and CAN-FD.

Use the quick setup option to set up your jitter or eye diagram analysis in just two clicks

Figure 8 – Quick Jitter and Quick Eye Diagram menu

– Quick jitter and Quick eye diagram options.  Instead of going through lengthy set up menus, you can do the quick setup option and set up your jitter or eye diagram analysis in just two clicks.

The Infiniium oscilloscopes now have more capabilities than ever. Armed with 5.60 you are equipped to test and impress like never before.  Whether you’re looking for digital memory analysis, designing power systems, or work in the automotive industry, we have test solutions for you.

Check out the Infiniium software, version 5.60 update!

As electrical engineers there are certain rules that we live and die by each day.  Probably, the most common of these is Ohm’s law.   No matter what we are doing it always seems to come back to V = I*R, doesn’t it? That silly little equation we learned way back in our youth, maybe in Engineering 101 or our first Physics class, lays the foundation for everything in our field.  But what about the other equations and rules that we worship and obey like a zombie survival guide during the apocalypse?  Likely, names like Nyquist and Kirchhoff come to mind. And as we delve further into our specific fields, the more specific and sometimes diversified these rules become – after all, there are many different zombies out there and each needs its respective weapon.   Sometimes, that weapon is an oscilloscope.

So what rules or guidelines are you thinking about when you are planning to purchase a scope?  Probably, you’ve thought again of things like Nyquist in terms of sample rate.  You’re thinking about memory depth and waveform update rate.  And the noobs, less likely to survive a zombie attack, might be thinking, “Give me the highest possible bandwidth!”  But you, seasoned veteran of the apocalypse, obviously know that more bandwidth is not necessarily better.

A good rule of thumb for selecting the bandwidth of your dreamy new oscilloscope is to choose a bandwidth that is 3 times the fastest frequency content in the signal you are looking to analyze.  This rule of thumb is for analog signals.  If you are on the digital side, then your rule of thumb is 5 times the clock rate of your digital signals. There is a great blog post below (What is oscilloscope system bandwidth and how do I find the bandwidth of the scope + probe) and app note (Evaluating Oscilloscope Bandwidths for Your Application) that go into more details on this if you want to get into the nitty gritty of the nerdy and work out some equations.

But in general, the 3x for analog and 5x for digital BW rule of thumb guarantees that you will have enough bandwidth to properly observe your waveform without taking in too much high frequency content, which will show itself as noise on your desired measurement. Noise is Gaussian, so a higher bandwidth scope sees higher frequency noise.

But what if, you have been bitten by the Maximum Bandwidth Zombie?  You came down with the fever and couldn’t turn your mind away from that crazy high bandwidth scope, even though most of your applications are really only operating around 2 MHz or so.  Or maybe you simply purchased a scope for a higher bandwidth application than what you need in this very moment.  Perhaps, in most cases you are after Runner zombies so you purchase a high bandwidth scope, but occasionally you have to deal with the standard Walkers.  Don’t worry, your oscilloscope is a many facetted weapon.  This is probably a situation in which you will want to apply bandwidth limiting.

So you turn on bandwidth limiting and suddenly you’ve gone from having a noisy signal and may be experiencing ghosting (a situation in which you’re seeing an additional waveform capture on the screen) to having a nice clean waveform capture.

Here’s an example.  Below is a screenshot from a Keysight MSO-X 3104T.  This scope has a bandwidth of 1 GHz.  On channel 1, I’ve input a 1 MHz sine wave and, for demonstration purposes, mixed it with noise from an 80 MHz function generator.   Because I’m using a 1 GHz scope, I’m observing my desired 1 MHz sine wave distorted with the noise from the function generator and any noise in the environment that the scope or probe configuration might be picking up. You’ll also observe the extra, faint signal on screen. This is the ghosting effect I referred to earlier.  This is happening because the scope is sometimes triggering on what appears to be the falling edge of the desired signal but actually a rising edge in the noise.  This is not pretty measurement, am I right?

Figure 1 – 1 MHz signal with noise

 

Now, I select the Channel 1 menu and I turn on BW Limit.  Bandwidth limiting can be applied to each channel separately.  The Bandwidth Limit feature on this scope reduces the maximum bandwidth to 20 MHz.

With the bandwidth limit turned on, the high frequency noise content has been filtered out, and the desired crisp waveform is what remains. See figure 2.  One zombie down.

Figure 2 – 1 MHz signal with noise + BW Limit turned ON

Make sure to check out the bandwidth limiting capabilities of your oscilloscope. Keysight has a wide range of options depending on the scope you are using.  For example, the InfiniiVision 6000 X-Series oscilloscope lets you select a 200 MHz BW Limit in addition to the 20 MHz BW Limit option shown above on the 3000T X-Series.  The Infiniium scopes offer even more possibilities.  For example, the MSO-S804A is an 8 GHz scope and allows you to emulate a 6 GHz, 4GHz, 2.5 GHz, 2 GHz, 1 GHz, and even a 500 MHz scope.

As I said before, Keysight is here to help you slay all forms of zombies.