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Oscilloscopes Blog

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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.

Professor BodeWhen I was an electrical engineering student back in the 1970’s at the University of South Florida — go bulls! — two of my favorite classes were Control Systems and Analog Circuit Fundamentals. One reason I loved these classes so much was because we got to create Bode plots. I know, that sounds weird. I really enjoyed finding the theoretical poles and zeros and drawing Bode plots on my green engineering graph paper by hand (pencil, paper, and a ruler). Thank you Professor Bode; you are my hero! But when it came time to go into the lab to verify the frequency response of something like a passive or active filter design that we were assigned to build and test, there were no frequency response analyzers (sometimes called network analyzers) to be found.

 

In those days network analyzers were highly specialized and expensive multi-box systems from test and measurement vendors, including Hewlett-Packard (Keysight’s predecessor). Without

access to one of these expensive instruments in my EE lab, the testing process consisted of taking multiple VIN, VOUT, and Δt measurements on an oscilloscope while changing the input sine wave frequency on a function generator. After making 15 or 20 measurements, I would have enough measured data points to convert to gain (20LogVOUT/VIN) and phase shift (Δt/T x 360) using my trusty slide rule. I would then plot the results back onto that green engineering graph paper alongside the theoretical plots for comparison.

 

The days of plotting theoretical results by hand are over. Most engineering students today use MATLAB® to do that. And certainly the days of taking multiple VIN and VOUT measurements in the lab using an oscilloscope and a function generator set at discreet frequencies must be over, right? After all, the test and measurement industry now offers a broad range of frequency response analyzers (FRA) and vector network analyzers (VNA) that create gain and phase plots automagically. But those days aren’t over! Most undergraduate EE teaching labs are not equipped with frequency response analyzers. Almost all EE students today use the same tedious method of testing a circuit’s frequency response that I used back in ancient times. Why is that?

 

FRAs and VNAs are still considered by many to be a specialized instrument — especially in the university environment. In addition, the price of these instruments start at around US $5,000 and go up from there. This may not sound like much for someone in the high tech industry that depends on this type of instrument to get to their testing done quickly, but almost all universities have to operate on a tight budget. A typical student lab bench (consisting of an entry-level 2-channel oscilloscope, function generator, digital voltmeter (DVM), and power supply) can be purchased for about US $2,000 today. To equip an entire student teaching lab with an FRA at an additional US $5,000 per test station would blow most EE lab budgets out of the water.


 1000 X-Series Oscilloscope

But now the process of making multiple VIN and VOUT oscilloscope measurements to create Bode gain and phase plots are about to be over for many EE students – at least for students at universities that equip their labs with a new Keysight oscilloscope. Keysight just introduced a family of low-cost oscilloscopes with an optional built-in function generator (Figure 2). And the best part is that automatic frequency response analysis (Bode gain and phase plots) can be performed on these student oscilloscopes at no additional charge on models that come equipped with the built-in WaveGen function generator and frequency response analysis (EDUX1002G and DSOX1102G). All of this functionality (oscilloscope, function generator, and frequency response analysis) can be had for just over US $600. Let’s take a look at a measurement example of characterizing a passive bandpass filter using this new oscilloscope.

Passive RLC bandpass filter

Figure 3 shows the schematic of a simple RLC circuit that we will test. At lower frequencies, the 1-µF capacitor dominates the impedance (XC = 1/2πfC) of this circuit and blocks most of VIN from getting to VOUT. At higher frequencies, the 10-µH inductor (XL = 2πfL) blocks most of the input from getting to the output. But in the mid-band frequencies, the 50-Ω load resistor dominates such that most of VIN reaches VOUT (~0 dB). By definition, this is a bandpass filter. We will now test it with Keysight’s new oscilloscope with the built-in function generator and frequency response analysis capability.

 

We begin by connecting the output of the generator to VIN and also probe VIN and VOUT with channel 1 and channel 2 of the oscilloscope, respectively. Figure 4 shows the frequency response analysis setup menu, which displays a block diagram to assist us in making proper connections. This is also where we can define which of the oscilloscope’s input channels is probing VIN, which channel is probing VOUT, the minimum test frequency, maximum test frequency, and test amplitude. For this test, we will use all the default settings. When we select Run Analysis, the oscilloscope executes the one-time  test, sometimes called a "sweep."

Figure 5 shows the test results. The blue trace represents gain (in dB) with scale factors shown on the left side of the display, while the orange trace represents phase (in degrees) with scale factors shown on the right side of the display. A pair of markers is also available to measure gain and phase at any frequency. The oscilloscope even optimizes magnitude and phase scaling factors automatically. But you also have the ability to establish your own scale factors manually after completion of the test. This is probably the easiest-to-use frequency response analyzer on the market today. At least that’s my opinion. And it has to be the least-expensive FRA because it comes standard (US $0) with the purchase of an EDUX1002G or DSOX1102G oscilloscope, which is only US $200 more than the baseline 1000 X-Series model (US $449). But performance is not sacrificed. Using a proprietary measurement algorithm, this instrument can achieve up to 80 dB of dynamic range based on a 0 dBm (224 mVrms) input.

 

Using this new Keysight oscilloscope capability has sure saved me a lot of time in my job. And I bet it will save EE students a lot of time as well so they can complete their lab assignments on time!

 

 

MATLAB is a registered trademark of MathWork, Inc.

The second the probe is connected to your device your signal begins a grand journey to the center of the scope. It has to pass through five phases in order to complete its journey to the center, then back up to the surface. First the signal has to find its way to the front of the scope through the probe. Then, once it enters the scope, it has to go through an attenuator, DC offset, and amplifier before it can reach the center. At the center, the signal goes through an analog to digital converter. In order to make its way back to the surface of the scope, it must venture to find the display DSP. Along the way, it finds evidence that signals have been here before. The timebase and acquisition blocks show that previous samples of signals have been collected. Once the signal passes through these two blocks, it will finally be displayed on the surface of the scope. Let’s learn a little bit more about everything your signal encounters along this journey.

Oscilloscope Signal

 

Your signal’s journey begins with traveling from your device through a series of resistive and capacitive components inside the probe. The attenuation specification of your probe will determine what resistive components are inside. Most standard passive voltage probes that come with DSO scopes have a 10:1 attenuation ratio. This type of probe would have a 9 MΩ probe tip resistor in series with the scope’s 1 MΩ input impedance. This would make the resistance at the probe tip 10 MΩ, which means that when your signal travels through the probe and reaches the scope’s input, it will be 1/10th of the voltage level that it was when it entered the probe at the tip from your device. This means that the dynamic range of the scope measurement system has been extended because you can now measure signals with 10x higher amplitude as compared to signals you could measure using a 1:1 probe. Also, this 10:1 passive probe ensures a high input impedance at the probe tip which will eliminate any loading on your device. Loading will change the way your device behaves, and we don’t want that.

Analog Input Signal Conditioning

 

Next the signal enters the scope to begin the first phase of processing, analog input signal conditioning. There are three stages to this conditioning process which are all done in order to scale the waveform correctly to be within the dynamic range of the analog-to-digital converter (ADC) and the amplifier. The processing done in these stages is dependent on what the V/div and offset settings are, which ultimately depends on whether you are measuring a low level or high level signal. First, the signal is scaled in the attenuator block, which is a network of resistor dividers. If you have a high level input signal, then the signal will be attenuated, or reduced. If you are inputting a low-level signal, then the signal will be passed through to the next step without any attenuation. You may often be inputting a signal that has a DC offset, but we want to be able to display that signal in the center of the screen at 0 V. In order to make that happen, there is an internal DC offset of the opposite polarity that is added to the signal to shift the scale. This way it will display on the center of the screen. Lastly, the signal travels into the variable gain amplifier. This type of amplifier will either increase or decrease the gain of your signal dependent on what your V/div setting. So, this again depends on whether you are looking at a low or high level signal. If you are working with a low level signal, you are likely at a low V/div setting which would tell the amplifier the gain should be increased so that we are utilizing the full range of the ADC. If you are working with a high level signal, then the signal would have been attenuated back in the first stage of this process, and the amplifier may then further attenuate the signal in this stage by decreasing the gain, again to scale the signal within the dynamic range of the ADC.

Analog to Digital Conversion and Trigger Blocks

 

Now that the signal is conditioned to be within the dynamic range of the ADC, it can enter the center of the scope and the analog to digital conversion can begin. The ADC block is the core component of all DSOs. This is where the analog input signal gets converted into a series of digital words. Most of today’s DSOs utilize 8-bit ADCs which will provide 256 unique digital output levels/codes. These digital binary codes are stored in the scope’s acquisition memory, which will be discussed later. In order to obtain the highest resolution and accurate measurements, the scope will try to use the full dynamic range of the ADC. While the signal is being converted in the ADC, the scope is also processing the trigger conditions needed to establish a unique point in time on the input signal upon which to establish a synchronized acquisition. Depending on what you set the trigger acquisition settings to on the scope, the trigger comparator block will output a non-inverted waveform with a duty cycle that is dependent on what you set the trigger level to. Then, depending on what you set the trigger type to (rising edge, falling edge, etc.) the trigger logic block will either invert the waveform before allowing it to pass through, or it will allow the non-inverted waveform to be passed through to the next step. This trigger signal is then used in the timebase block in the next step as the unique synchronization point in time.

Timebase and Acquisition Memory Blocks

 

              The timebase block controls when ADC sampling is started and stopped relative to the trigger event that was just determined in the previous step. In addition, the timebase block controls the ADCs sample rate based on the scope’s available acquisition memory depth and the timebase setting. When the Run key is pressed, the timebase block enables continuous storing of the digitized data into the scope’s “circular” acquisition memory at the appropriate sample rate. While the timebase block increments addressing of the circular acquisition memory buffer after each sample, it also counts the number of samples taken up to a certain number which is dependent on the memory depth of the scope along with the trigger position. Once the timebase block determines that the minimum required number of samples of your signal have been collected, the timebase block enables triggering and begins to look for the first qualifying point of the output trigger comparator. Once the trigger event is detected, the timebase block then begins collecting the required number of samples. Once all of the samples have been stored, the timebase block disables the sampling and the process is pushed on to the next step.

 Display DSP Block

             

              Your signal has now reached the final stage in its journey. Once the acquisition of all of the samples has been completed, the data in the acquisition memory is “backed out” in a last-in-first-out sequence. The signal is reconstructed from the samples and the data is put into the scope’s pixel display memory and it is ultimately displayed on the screen. Once all of the data has been “backed out” of the acquisition memory, the DSP block signals the timebase block that it can begin another acquisition. This is a technique that is unique to Keysight’s custom ASIC technology. Traditionally, most other DSO oscilloscopes would not include this DSP block, but would instead use the scope’s CPU system. That method greatly decreases the efficiency of the scope and slows down the waveform update rate, so you would lose accuracy in your measurements and miss important glitches. Using the DSP block allows Keysight scopes to always operate at high efficiency and display a waveform that is more true to what is actually coming out of your device.

 DSP block waveform oscilloscope

              You can see the signal goes through quite the lengthy journey before it is displayed on the scope’s screen, but this all happens in the blink of an eye. To learn more about the fundamentals of oscilloscopes, download Keysight’s application note, Evaluating Oscilloscope Fundamentals. 

The second the probe is connected to your device your signal begins a grand journey to the center of the scope. It has to pass through five phases in order to complete its journey to the center, then back up to the surface. First the signal has to find its way to the front of the oscilloscope through the probe. Then, once it enters the scope, it has to go through an attenuator, DC offset, and amplifier before it can reach the center. At the center, the signal goes through an analog to digital converter. In order to make its way back to the surface of the scope, it must venture to find the display DSP. Along the way, it finds evidence that signals have been here before. The timebase and acquisition blocks show that previous samples of signals have been collected. Once the signal passes through these two blocks, it will finally be displayed on the surface of the oscilloscope. Let’s learn a little bit more about everything your signal encounters along this journey to understand how an oscilloscope works.

Oscilloscope Signal

 

Your signal’s journey begins with traveling from your device through a series of resistive and capacitive components inside the oscilloscope probe. The attenuation specification of your probe will determine what resistive components are inside. Most standard passive voltage probes that come with digital storage oscilloscopes (DSOs) have a 10:1 attenuation ratio. This type of probe would have a 9 MΩ probe tip resistor in series with the scope’s 1 MΩ input impedance. This would make the resistance at the probe tip 10 MΩ, which means that when your signal travels through the probe and reaches the scope’s input, it will be 1/10th of the voltage level that it was when it entered the probe at the tip from your device. This means that the dynamic range of the oscilloscope measurement system has been extended because you can now measure signals with 10x higher amplitude as compared to signals you could measure using a 1:1 probe. Also, this 10:1 passive probe ensures a high input impedance at the probe tip which will eliminate any loading on your device. Loading will change the way your device behaves, and we don’t want that.

Analog Input Signal Conditioning

 

Next the signal enters the oscilloscope to begin the first phase of processing, analog input signal conditioning. There are three stages to this conditioning process which are all done in order to scale the waveform correctly to be within the dynamic range of the analog-to-digital converter (ADC) and the amplifier. The processing done in these stages is dependent on what the V/div and offset settings are, which ultimately depends on whether you are measuring a low level or high level signal. First, the signal is scaled in the attenuator block, which is a network of resistor dividers. If you have a high level input signal, then the signal will be attenuated, or reduced. If you are inputting a low-level signal, then the signal will be passed through to the next step without any attenuation. You may often be inputting a signal that has a DC offset, but you want to be able to display that signal in the center of the screen at 0 V. In order to make that happen, there is an internal DC offset of the opposite polarity that is added to the signal to shift the scale. This way it will display on the center of the screen. Lastly, the signal travels into the variable gain amplifier. This type of amplifier will either increase or decrease the gain of your signal dependent on what your V/div setting. So, this again depends on whether you are looking at a low or high level signal. If you are working with a low level signal, you are likely at a low V/div setting which would tell the amplifier the gain should be increased so that you are utilizing the full range of the ADC. If you are working with a high level signal, then the signal would have been attenuated back in the first stage of this process, and the amplifier may then further attenuate the signal in this stage by decreasing the gain, again to scale the signal within the dynamic range of the ADC.

Analog to Digital Conversion and Trigger Blocks

 

Now that the signal is conditioned to be within the dynamic range of the ADC, it can enter the center of the scope and the analog to digital conversion can begin. The ADC block is the core component of all DSOs. This is where the analog input signal gets converted into a series of digital words. Most of today’s DSOs utilize 8-bit ADCs which will provide 256 unique digital output levels/codes. These digital binary codes are stored in the oscilloscope’s acquisition memory, which will be discussed later. In order to obtain the highest resolution and accurate measurements, the scope will try to use the full dynamic range of the ADC. While the signal is being converted in the ADC, the scope is also processing the trigger conditions needed to establish a unique point in time on the input signal upon which to establish a synchronized acquisition. Depending on what you set the trigger acquisition settings to on the oscilloscope, the trigger comparator block will output a non-inverted waveform with a duty cycle that is dependent on what you set the trigger level to. Then, depending on what you set the trigger type to (rising edge, falling edge, etc.) the trigger logic block will either invert the waveform before allowing it to pass through, or it will allow the non-inverted waveform to be passed through to the next step. This trigger signal is then used in the timebase block in the next step as the unique synchronization point in time.

Timebase and Acquisition Memory Blocks

 

              The timebase block controls when ADC sampling is started and stopped relative to the trigger event that was just determined in the previous step. In addition, the timebase block controls the ADCs sample rate based on the scope’s available acquisition memory depth and the timebase setting. When the Run key is pressed, the timebase block enables continuous storing of the digitized data into the scope’s “circular” acquisition memory at the appropriate sample rate. While the timebase block increments addressing of the circular acquisition memory buffer after each sample, it also counts the number of samples taken up to a certain number which is dependent on the memory depth of the oscilloscope along with the trigger position. Once the timebase block determines that the minimum required number of samples of your signal have been collected, the timebase block enables triggering and begins to look for the first qualifying point of the output trigger comparator. Once the trigger event is detected, the timebase block then begins collecting the required number of samples. Once all of the samples have been stored, the timebase block disables the sampling and the process is pushed on to the next step.

 Display DSP Block

             

              Your signal has now reached the final stage in its journey. Once the acquisition of all of the samples has been completed, the data in the acquisition memory is “backed out” in a last-in-first-out sequence. The signal is reconstructed from the samples and the data is put into the oscilloscope’s pixel display memory and it is ultimately displayed on the screen. Once all of the data has been “backed out” of the acquisition memory, the DSP block signals the timebase block that it can begin another acquisition. This is a technique that is unique to Keysight’s custom ASIC technology. Traditionally, most other digital storage oscilloscopes would not include this DSP block, but would instead use the scope’s CPU system. That method greatly decreases the efficiency of the scope and slows down the waveform update rate, so you would lose accuracy in your measurements and miss important glitches. Using the DSP block allows Keysight oscilloscopes to always operate at high efficiency and display a waveform that is more true to what is actually coming out of your device.

 DSP block waveform oscilloscope

              You can see the signal goes through quite the lengthy journey before it is displayed on the scope’s screen, but this all happens in the blink of an eye. To learn more about the how an oscilloscope works, download Keysight’s application note, Evaluating Oscilloscope Fundamentals. 

When you are testing a crystal oscillator circuit with an oscilloscope probe, the oscillator may stop oscillating or the waveform may be severely distorted. Why?

 

Every probe functions as an external circuit connected to the device under test. Each probe has its own input resistance, capacitance and inductance, imposing additional load to the DUT. Connecting a probe to the oscillator circuit (or any electronic circuit) adds extra load to a signal or may distort the waveform displayed on the oscilloscope thanks to the loading effect. Therefore, probing an oscillator circuit requires special care, as the oscillator circuit is highly sensitive to capacitance. 

Connecting a probe to the oscillator circuit

Figure 1  Connecting a probe to the oscillator circuit adds extra loads to a signal

 

There are two main factors to consider in choosing a probe for oscillator testing. The first is that the oscilloscope probe is adding capacitance to the existing load capacitors (C1 and C2 in fig 2). The load capacitance is a parameter for determining the frequency of the oscillation circuit. It is important to note that the change in the value of the load capacitance may result in changes in the output frequency of the oscillator or at worst case, it may stop the oscillation. The second factor is that the probe is introducing resistive loading to the oscillator circuit. Both factors can be significant enough to keep the oscillator from working. At DC or low frequency ranges, probe loading is mostly caused by the resistance of the probe, and as the frequency goes up, capacitive component of the probe becomes the dominant factor in the loading effect.

A circuit diagram of a typical oscillator circuit

Figure 2 A circuit diagram of a typical oscillator circuit

 

A solution is to use a probe with high input resistance and low input capacitance in order to cause the lowest possible loading effect. In general, a passive probe with 100:1 attenuation ratio such as Keysight N2876A passive probe (with 2.6 pF of input capacitance) reduces capacitive loading significantly on the circuit, compared to a conventional 10:1 passive probe with ~10 pF of capacitive loading. Loading can be further reduced by switching the oscilloscope input coupling from DC to AC, as DC coupling mode on an oscilloscope presents additional loading to the oscillator and may cause it to stop.

 

Or, better yet, using an active probe with low input loading such as Keysight’s N2795A 1 GHz active probe or N2796A 2 GHz single-ended active probe may deliver better results. This active probe provides 1 Mohm input at DC and low frequencies for low resistance in parallel with <1 pF input capacitance loading to the circuits. Another good probe for oscillator circuit measurement is a Keysight InfiniiMax 1130A Series or N2750A Series InfiniiMode probe that presents even lower loading to the circuit.

Input impedance equivalent model of Keysight N2795A/96A single-ended active probe

Figure 3 Input impedance equivalent model of N2795A/96A single-ended active probe

 

Also, it’s important to note how to connect the probe to the DUT. If your probe connection has obviously longer input lead wires or a connector at the tip, you should suspect frequency response variation and degradation. In general, the longer the input wires or leads of a probe tip, the more it may decrease the bandwidth, increase the loading, cause non-flat frequency response and result in more variation in response. If at all possible, keep the input leads of the probe tip as small as possible, and keep the loop area of connection as small as possible.

Keep the input leads and loop area of connection small for more accurate results

Figure 4 Keep the input leads and the loop area of the connection as small as possible for more accurate results.

If your probe connection has longer input lead wires or a connector, look for frequency response variation and degradation

Figure 5 If your probe connection has obviously longer input lead wires or a connector at the tip, you should look for frequency response variation and degradation.

Today is the day! Today is the day!!

Why is today so important? I’m glad you asked.

Well, for starters, it’s the first day of Scope Month! If you liked last year’s Scope Month, you’re going to love the 2017 version. During the entire month of March, we’re giving away 125 oscilloscopes – that’s more than 3x what we gave away last year. Make sure you enter every day for even more chances to win. Bookmark www.scopemonth.com for easy access to all of the information you need. And, check out the drawings on YouTube each day to see if you’re one of the winners. Don’t want to leave it to chance? Check out the Test to Impress Contest and tell us why you should get a new oscilloscope.

But why else is today so important?

InfiniiVision 1000 X-Series

One of the main Scope Month giveaways is the new InfiniiVision 1000 X-Series, and we just introduced it today! The 1000 X-Series has 50 to 100 MHz bandwidths and a starting price of $449 (USD). This oscilloscope family lets you capture more of your signal and see more signal detail than similarly-priced scopes with its up to 2 GSa/s sampling rate and 50,000 waveforms per second update rate. They feature up to 6-in-1 instrument functionality to give you even more value for your money, and they have 2 analog channels (and the external trigger can be used as a 3rd digital channel). Segmented memory capability maximizes the memory depth while helping the scope test faster. Basically, if you want the best cheap oscilloscope available, you should be looking into the 1000 X-Series.

The 1000 X-Series is ideal for new (or intermediate) oscilloscope users. The front-panel is industry-standard, so you know it’s going to be similar to other oscilloscopes you’ve used (or will use in the future). And getting up to speed on oscilloscope functionality is easy with its built-in help features. So if you’re stuck or want more explanation about a measurement, you can press down and hold any button to access help screens and short setup tips.

 1000 X-Series Oscilloscope built-in1000 X-Series Oscilloscope training signals

   Built-in help comes in 13 different languages                                       11 training signals are built into the scopes

Educators also like the 1000 X-Series because in addition to giving students easy access to help information, an Educators Resource Kit is included at no additional cost. Other vendors usually charge more for their Educators Resource Kit, but Keysight’s 1000 X-Series oscilloscopes come standard with 11 build-in training signals, a comprehensive oscilloscope lab guide, and an oscilloscope fundamentals slide show for professors and lab assistants. Another big draw for educators is the Bode plot capability made possible with the frequency response analyzer in the EDUX1002G and DSOX1102G models.

The 1000 X-Series’ 6-in-1 instrument integration means you’re getting even more out of your oscilloscope investment. In addition to being an oscilloscope, it is also a:

  • Frequency response analyzer (EDUX1002G and DSOX1102G models only)
  • WaveGen function generator (EDUX1002G and DSOX1102G models only)
  • Serial protocol analyzer (with additional software)
  • Digital voltmeter (free with registration)
  • Frequency counter

 

To learn more about the 6-in-1 capability, check out pages 8 and 9 of the 1000 X-Series data sheet.

The 1000 X-Series has professional-quality measurement and software analysis capability. These oscilloscopes have 24 typical oscilloscope measurements to help you quickly analyze signals and determine signal parameters. The gated FFT function gives you additional signal analysis, letting you correlate time and frequency domain on a single screen. Mask limit testing is also available to help you easily detect signal errors. The 1000 X-Series supports analysis and decode of popular embedded and automotive serial bus applications, including I2C, UART/RS232, SPI, CAN and LIN.

1000 X-Series Oscilloscope measurment1000 X-Series Oscilloscope measurment

As you can see, while the 1000 X-Series oscilloscopes are low-cost, Keysight managed to pack a lot of capability into them. Years of Keysight-custom technology and expertise was leveraged to look for ways to aggressively reduce costs while not sacrificing on quality. (But more about that in a later blog post!)

Here are the raw specs, but make sure to check out the 1000 X-Series web page for more information or click here to get a 1000 X-Series quote.

 Models

EDUX1002A

EDUX1002G

DSOX1102A

DSOX1102G

Bandwidth

50 MHz

70/100 MHz

Price

$449 (USD)

$649 (USD)

$649 (USD)

$849 (USD)

Bandwidth upgrade

-

100 MHz opt (DSOX1B7T102)

Display

7 inch WVGA non-touch

Waveform update

50,000 wfms/sec

Vertical sensitivity

500 uV/div ~ 10 V/div

DVM

Free with the customer registration

Channels

2 channel

Probes

1:1, 10:1 switchable 70 MHz

(N2142A)

1:1, 10:1 switchable 200 MHz

(N2140A)

Sampling rate

1 GSa/s

2 GSa/s

Memory

100 kpts standard

1 Mpts standard

Segment memory

-

Standard

Mask/limit test

-

Standard

WaveGen (20 MHz)

-

Yes, standard

-

Yes, standard

Bode plot

-

Yes, standard

-

Yes, standard

Serial decodes

I²C, UART (opt. EDUX1EMBD)

I²C, SPI, UART (opt. DSOX1EMBD) CAN, LIN (opt. DSOX1AUTO)

Warranty

3 year standard (5 year option)

It’s Scope Month, and you know what that means, oscilloscope giveaways! But this year we’re giving you even more chances to win.

 

How?

This year Scope Month includes a scavenger hunt. We have hidden your favorite oscilloscope guru Daniel Bogdanoff all over the world (don’t worry, they’re just life-size cardboard cutouts). Your job? Find Daniel. If you (the scopes community) find Daniel, we will add more scopes to the daily drawings during Scope Month! And the faster that you find him, the more free oscilloscopes it means for you!

 

What do I do?

Watch the Keysight Oscilloscopes Facebook and YouTube channels, because we will release a clue on the whereabouts of Daniel each Monday during Scope Month. Once you have the clue, start searching. If you get stuck, come back to the comments section of this blog post where you can collaborate with the rest of the world and maybe together you can find Daniel sooner. When you find the Daniel cutout, post a picture of it along with the hashtag #GoFindDaniel to the Keysight Oscilloscopes Facebook page or mention @Keysight_Daniel on Twitter so that we know to add more oscilloscopes to the drawing.

 

How many oscilloscopes?

If you find the Daniel cutout by 11:59 pm US Mountain Time (6:59 am UTC time) on Tuesday, we will add FIVE MORE SCOPES to the prize pool for that week. If he is found before midnight on Wednesday, we will give away four more scopes, before midnight on Thursday means three more, midnight on Friday is two more, and if Daniel is found by 11:59 pm on Saturday evening, we will add one extra scope to the prize pool. So work together! The sooner you find the cutout, the more free oscilloscopes we will give away! And you don’t even have to wait long for your reward! The drawings for these additional oscilloscopes will be done on or before the following Monday!

 

Don’t forget to enter the oscilloscope giveaway every day during Scope Month for your chance to win a new Keysight 1000 X-Series oscilloscope.

 

Check out the rest of the Keysight oscilloscope family

 

Terms and Conditions

 

GoFindDaniel CLUE #2: 68747470733a2f2f7777772e796f75747562652e636f6d2f77617463683f763d3645703650425379366945

 

What is the best oscilloscope for your application? The following areas will help you make an accurate and informed decision. Today’s complex electronics industries require a broad spectrum of test equipment, with oscilloscopes being one of the most fundamental tools used by engineers and technicians. Oscilloscopes provide design and manufacturing engineers with critical insights to signal properties suggesting additional design work needed, targeting manufacturing issues, or performing compliance and protocol testing per international standards.

Oscilloscopes fall into two groups, real-time oscilloscopes and sampling oscilloscopes (also called equivalent-time oscilloscopes) and it is important to understand the difference between the two types. Real-time oscilloscopes digitize a signal in real-time. Imagine a repetitive AC signal - the real-time oscilloscope acts like a camera, taking a series of frames of the signal during each cycle. The amount of frames the real-time oscilloscope captures depends upon the bandwidth, memory depth, and other attributes that we will soon discuss. A sampling oscilloscope, on the other hand, takes only one shot of the signal per cycle. By repeating this one shot, but at slightly different time frames, the sampling oscilloscope can reconstruct the signal with a high degree of accuracy.

The following topics can help you better evaluate which kind of oscilloscope will best suit your needs.

Trigger

Sampling oscilloscopes are designed to capture, display, and analyze repetitive signals. If your oscilloscope solution needs to capture a single random event within your waveform, a real-time oscilloscope should be selected. Whether you are looking at intermittent signals during product design or manufacturing, real-time oscilloscopes allow you to trigger on a specific event such as a rising voltage threshold, a set up and hold violation, or a pattern trigger. The real-time oscilloscope will capture and store continuous sample points around these triggers and update the display with the captured data.

 

Bandwidth

The frequency of your signal under test and the harmonics within it will determine the bandwidth of the oscilloscope that will fit your needs. Sampling and real-time oscilloscopes cover a wide bandwidth range and there is a lot of overlap. A sampling oscilloscope can acquire any signal up to the analog bandwidth of the oscilloscope regardless of the sample rate. But a real-time oscilloscope must gather a significant number of samples after the initial trigger to accurately display a waveform. A typical rule of thumb for a real-time oscilloscope bandwidth is 2.5 times your signal frequency to reproduce your signal with the best fidelity. So you can get by with an effectively lower bandwidth scope using a sampling scope as long as you have the trigger mentioned in the previous section.

 

Memory Depth

Oscilloscope memory depth is an important specification for only real-time oscilloscopes. A real-time oscilloscope captures an entire waveform on each trigger event. To do this the real-time oscilloscope captures a large number of data points in one continuous record. For a real-time oscilloscope, the memory is directly tied to the sample rate. The more memory you have, the more samples (sample rate) you can capture for each waveform.  The higher the sample rate, the higher the effective bandwidth of the oscilloscope.  There is a simple calculation to determine the sample rate given a specified time base setting and a specific amount of memory (assuming 10 divisions across screen): Memory depth / ((time per division setting) * 10 divisions) = sample rate (up to the max sample rate of the ADCs). This memory depth concept does not apply to sampling oscilloscopes because only one instantaneous measurement of waveform amplitude is taken at the sampling instant.

 

Analog to Digital Converter Bits

Sampling oscilloscopes can have as high as a 14-bit analog-to-digital converter (ADC). Consequently, they have a very large dynamic range, which enables viewing signals ranging from a few millivolts to a full volt without the need for attenuation. This allows sampling oscilloscopes to maintain very low noise levels at all volts per division settings. A real-time oscilloscope is limited in its dynamic range to 8 - 10 bits depending upon the model, but typically will show an effective bit number of around 6 – 8 bits respectively. Because of a real-time oscilloscope’s lower signal-to-noise ratio, it is designed with attenuators to correctly display signals at specific volts per division settings.

 

Frequency Response

Frequency response is another key consideration in your selection criteria. Sampling oscilloscopes do not use digital signal processing (DSP) correction, so the frequency response rolls off slowly and looks more Gaussian in shape. Real-time oscilloscopes can implement DSP to correct their frequency response. For instance, Keysight’s S-Series oscilloscope has a very flat frequency response across its bandwidth, which means its gain will not vary by more than 1 dB across the entire band.

 

Clock Recovery

The clock recovery component of an oscilloscope measurement is used for building real-time eyes, mask testing, and jitter separation. A recovered clock is a reference clock within the oscilloscope and used for measurement comparisons. Keysight’s Sampling oscilloscopes provide an accurate software-based clock recovery system. In many applications, real-time oscilloscopes have a software clock recovery and selectable hardware clock recovery frequencies. Please note that the advantage of a software clock recovery is that it is not prone to the hardware errors, and will land its edges where they need to be regardless of the data rate.

 

Applications

Sampling oscilloscopes, like real-time oscilloscopes, offer eye diagrams, histograms, and jitter measurements. With high bandwidths, modularity, and lower pricing, they typically fit manufacturing environments better than real-time oscilloscopes.

 

Many of Keysight’s sampling oscilloscopes have modular systems consisting of a mainframe and various electrical, optical and TDR modules. This allows the end user to customize measurement hardware to fit their solution. Sampling oscilloscope electrical and TDR channels can be integrated into a module to reduce cost or remote heads can be used to improve accuracy. Optical channels are always integrated creating a well-controlled 4th-order Bessel-Thomson frequency roll-off.

 

When making jitter measurements clock recovery systems play a large role. Understanding the clock recovery algorithm and the jitter transfer function used will help you determine your final oscilloscope selection. The sampling oscilloscope has a slightly lower jitter and a higher dynamic range making it ideal for characterization in a controlled environment assuming that your signal is repeatable. However, real-time oscilloscopes are great if you need to trigger on difficult to find events. Real-time oscilloscope users can choose from a long list of compliance, protocol triggering and decode, and analysis applications including jitter.

 

Form Factor

Your solution may require an oscilloscope solution with a specific size or configuration (form factor) to fit your needs. Keysight has both sampling and real-time scope solutions in a variety of form factors, from standard desk top and rack mountable frames to faceless (no screen) module solutions in a variety of AXI or PXI configurations. See the links below for sampling and real-time options.

 

http://fieldcom.cos.keysight.com/portal/Coll.php?cId=-32528

http://fieldcom.cos.keysight.com/portal/Coll.php?cId=-32546

 

Summary

On the surface there is a lot of overlap between sampling and real-time oscilloscopes but the differences in capabilities and performance that we have discussed can help you make an informed decision to tailor a selection to your specific application.

 

If you require measurements of a repetitive waveform with lower jitter and a higher dynamic range, a sampling oscilloscope is a good choice. In addition, sampling oscilloscopes have an advantage of a lower initial cost and modular upgrades, making them well suited for electrical and optical manufacturing test applications. Real-time oscilloscopes come in a variety of bandwidths, include the ability to capture single-shot events as well as repetitive signals.

 

Both Keysight sampling and real-time oscilloscopes are available in frequencies from 1 GHz to 50 GHz and beyond with a variety of modular and frame options to fit your specific requirements.

 keysight oscilloscopes samplingscope

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

KeysightOscilloscopes

Scope Month 2017

Posted by KeysightOscilloscopes Employee Feb 15, 2017

It’s almost that time again, we’re only a few weeks away from Scope Month 2017! If you missed out last year, or are just getting ready for this year, here’s what you need to know.

 

Just like you, we love oscilloscopes. So Keysight created an entire month to celebrate oscilloscopes and the great engineers who use them, that’s you! March 1, 2017 kicks off Scope Month, which will run through March 31, 2017, and will offer new measurement tips, oscilloscope resources, a new Keysight oscilloscope, and of course oscilloscope giveaways!

Everyone’s favorite part of Scope Month is the oscilloscope giveaways, and this year won’t disappoint. For Keysight Scope Month 125 oscilloscope giveawaysScope Month 2017, Keysight is giving away more than 125 oscilloscopes! We will be drawing new winners each weekday during Scope Month and posting these drawings on our YouTube Channel along with a helpful measurement tip for you. You will be able to enter the drawing once per day during Scope Month, and all entries will be eligible for the entire drawing period. And the best part is that you can get an extra chance to win: if you enter now, you get an early entry into the sweepstakes (only one per person during the early-entry period).

 

Enter now

 

Any questions? Check out the FAQs on this page. Did we miss anything? Ask your questions in the comment section below and we’ll get back to you.

 

 

Keysight Test to Impress contestNot quite ready to leave a new oscilloscope up to chance? You can also participate in the Test to Impress video contest. Just create and submit a video explaining why you need a new Keysight oscilloscope and how you would use it, and you could win one! Eligible entries will be reviewed by a panel of recognized industry voices who will choose 1 Grand Prize winner to win a 6-GHz 6000 X-Series oscilloscope and 2 “Runner up” winners to receive brand new Keysight 350-MHz 3000T X-Series oscilloscopes. Entries will be accepted March 1-31st, 2017 at www.scopemonth.com. Be sure to stay tuned after Scope Month, because we’ll announce the winners April 14th, 2017.

 

 

Keysight new oscilloscope

But wait, there’s more… this year the start of Scope Month also means a big SURPRISE. We can’t give it away just yet, but we can tell you there’s a brand new oscilloscope coming to the Keysight family and Scope Month will give you the first chance to see it and even get your hands on one for free (and you’ll definitely want to get your hands on one)!

 

Add the live Scope Month kickoff to your calendar to make sure you’re the first to see it!

 

 

While you wait for Scope Month to begin, we have quite a few great resources to help you with your measurement challenges:

  • Oscilloscope Learning CenterQuickly access video tutorials, application notes, white papers, and industry experts. Whether it’s your first time in front of a scope or you’ve been using one for decades, the oscilloscope learning center can help you stay ahead of next technology.
  • Oscilloscope blog – follow us to see a new post each week around topics from new releases to helpful tips to industry news
  • EEs Talk Tech – Join Mike and Daniel for an insider’s perspective on some of the latest technology trends and what they mean for you
  • Keysight 2 Minute Guru – Check out this series of 2-minute videos for tips on making better measurements
  • Digital Design and Test webcast series – Need a little more detail on some of the more complex measurements? Check out our free webcast series and join technology experts for more info on a range of topics

 

Check them out today!

The New Design and Test Challenges

If you plan on leveraging the work you previously did in your PCIe 3.0 design, you are mistaken. A doubling of the speed from 8 gigatransfers/second to 16 gigatransfers/second has a tremendous impact on both the design and validation of your high speed interconnect technology.

 

What are the Key Drivers for PCIe 4.0?

Big Data Needs Throughput. Big data is a term for data sets that are so large or complex that traditional data processing applications are inadequate to deal with them. Challenges include analysis, capture, data curation, search, sharing, storage, transfer, visualization, querying, and updating.

Networking Connectivity Applications.   Streaming movies, streaming sporting events, on-demand TV and the multitude of personal videos uploaded and downloaded is growing exponentially. Simply put, PCIe 3.0 cannot keep up with the latest Ethernet specs without increasing the number of lanes that are required. An increase in the number of lanes means increased cost in terms of power, circuit board layout and required components.  

Storage Technology. PCIe 3.0 has been pushed to its limits for SSD (Solid State) storage devices.   Greater interconnect speeds are required to take advantage of latest storage technologies.

 

Challenges

Channel Attenuation – Higher frequency means greater channel loss. PCIe 3.0 circuit traces can be made to run up to 16-20 inches if design care is taken. PCIe 4.0, on the other hand, is expected to have a maximum trace length of 10-12 inches. It’s simply impossible to use low-cost FR-4, pass through two connectors, and retain enough signal integrity at these speeds; no matter how robust the transmit and receive equalization schemes at the source and endpoint devices are.

So how do you mitigate the effects of greater channel attenuation?    

The answer is retimer(s). A retimer is actually an extension component or, thought of another way, a smart repeater operating at the physical layer to fine tune the signal. So to achieve 20 inches you can place the retimer at 10 inches from both the transmitter and receiver to ensure the required channel length. The link initialization protocol still negotiates the amount of transmitter de-emphasis (to optimize the receiver equalization), but now this negotiation is done to and from the retimer instead of the transmitter.   Therefore, the Retimer, from a link equalization standpoint, behaves exactly like any endpoint or root complex device. It has an upstream and downstream side so when you boot up it starts the initialization. This essentially doubles the essentially doubling the channel length, but at an added cost.  

Signal Integrity – If you are driving a signal into the channel transmit lane (Tx) and it encounters a change in the impedance profile, it will generate a reflection and, if the return loss of the SERDES is sufficiently high, (meaning poor) it bounces back down the channel. If I have high return loss, then the reflected signal may significantly impact the integrity of the transmitted signal.

So whatever design you use for PCIe 3.0 will not work for 4.0. It is not simply a matter of doubling the data rate, because you now have to meet a more stringent return loss characteristic.   So, you actually have to change the design at the silicon level to effectively give you more return loss at the higher frequencies.

Receiver Calibration – The key challenge is the ever shrinking eye height specification. PCIe 4.0 specifies a minimum eye height of 15 mV after equalization with a maximum bit error rate 1 X 10-12.   You are totally dependent upon your receiver’s ability to maximize the eye height. You now have to calibrate to an even finer grain of detail.

 

How do you effectively validate and test?

Keysight is the first to market with full support of both PCIe 4.0 TX Tests under the 0.7 version of the specification and includes the extensive reference clock phase jitter tests required under this specification.

The N5393F compliance test software for transmitter testing of PCI Express 4.0 devices allows for BASE spec testing of new PCI Express silicon under the 0.7 version of the PCIe 4.0 specification. The N5393F product supports transmitter testing of speeds up to 16 GBits/s while also supporting intermediate speeds of 2.5G, 5G, and 8GBit/s. In addition, legacy PCI Express 1.1, 2.X, and 3.X transmitter tests are also supported. This software will run on real time oscilloscopes having 12 GHz (or greater bandwidth) including the Z-Series, V-Series, X-Series, Q-Series, and 90000A platforms.

The N5393F also includes reference clock tests defined in the PCIe 4.0 specification, covering phase jitter requirements. Since the vast majority of PCI Express implementations utilize a common reference clock architecture, it is critical to ensure that a candidate reference clock device meets the many different permutations of phase jitter required for each of the 4 data rates. For PCIe 4.0, this represents over 144 different tests that have to be performed on the reference clock.

The N5393F also adds support for transmitter testing over the new U.2 (or SFF-8639) connector. As PCI Express expands its application base to support Solid State Storage Drives (or SSDs), the U.2 connector has been chosen as the main interface used in computer server platforms.

 Keysight PCIe Compliance Application

Easily select any PCIe transmit compliance application.

PCIe Compliance Application Menu

All testing is automated and produces a hyperlinked HTML report file that makes it easy to identify and study any failed or marginal clock jitter parameters.

Learn more about all of Keysight's PCI Express (PCIe) design and test solutions

Alright, this tool may not actually be helpful in your search for dinosaurs if someone really were to figure out how to bring them back, but this makes a great example to help explain the concept of oscilloscope segmented memory.

So, let’s begin our journey to the greatest theme park of all time – we’ll call it “Dinosaur Island” for lack of a better name... Naturally you’re going to want as much footage as possible of your favorite dino so you can always remember this grand adventure (assuming it has a better outcome than in the movie). Let’s say you’re a huge T-rex enthusiast, so you want to capture them (and only them) running around the park each day. To do this, you can set up a video camera in a tree and retrieve the footage at the end of the day.

 

But when looking at the footage from the first day, not only do you see your beloved T-rex, but you also see all of the velociraptors, triceratops, diloposaurus, and whatever other Jurassic creatures were running through the park that day. Your camera only has so much memory, and it filled up half way through the day. So you’ve wasted the majority of the memory on these other dinos you don’t even care about. You only have two days left in the park and you really want more T-rex footage. What do you do now?

 

What if you could set up a sensor condition (or trigger condition) that tells the camera to only record when there is T-rex running by? Now, when you collect your camera at the end of the trip, the memory will only consist of T-rex footage! Not only do you save memory and use it more efficiently, but you also save yourself loads of time by not having to sift through all the footage you don’t care about.

 

Sadly, your amazing trip has come to an end and it is time for you to return to the real world as an engineer. However, you did learn some new skills that can be applied to making oscilloscope measurements. The concept of capturing T-rex footage using a sensor condition directly correlates to using segmented memory on an oscilloscope. Let’s say you have a signal that has infrequent pulses – like an RF burst (image below). There are about 4ms of dead time (miscellaneous dinosaurs) between each RF pulse while the pulses themselves (your T-rex) are about 700ns. If you were to acquire this signal as-is, including all dead time, you would use 0.0175% of that memory capturing the actual pulse (T-rex) and 99.98% of it on that dead time (misc. dinosaurs)! THAT’S INSANE! Almost all of your memory is being used on something that you don’t even want to see.

 

To solve this problem, you could always just buy an oscilloscope with significantly more memory, but that gets very expensive very quickly. A much cheaper solution would be to utilize the segmented memory tool, which is already integrated into Keysight oscilloscopes. This application comes standard on the 4000 and 6000 X-Series and all Infiniium oscilloscopes, and can be activated via software license on the 2000 and 3000T X-Series. With this application, you can set a specific trigger condition and tell the oscilloscope to only capture the waveform when that condition is met. So, once you set the trigger and segment parameters, your scope will only capture the pulses in the signal and ignore the dead time (image below). This means that 100% of your memory is being used to capture the pulses and 0% capturing dead time. It allows you to capture a long time span while still digitizing at a high sample rate. This way, you aren’t losing any signal detail for those pulses and you’ll be able to make even more accurate measurements.

 

Keysight Segmented Memory diagram

 

As I previously mentioned, this method will also save you a lot of time. Once all of the segments are acquired, you can easily scroll through a list of these segments and select which one you want to view (shown below). This list includes a time-tag of each of the segments which will give you insight into the frequency of each of the pulses. You can also view real-time and date information along the bottom of the screen, so you can see precisely when the pulse occurred. When using segmented memory for serial applications, the oscilloscope will automatically provide protocol decode for each of the captured packets.

 

 

Segmented memory can be especially helpful for many different applications, such as measuring an RF burst, decoding serial buses, finding glitches in repetitive signals, seeing the timing of single-shot events, the list goes on. This method gives you deeper insight in your design and helps you debug faster.

 

Want more detail? Check out these resources to understand how the segmented memory application works and how to set it up.

Segmented Memory Application Note

Using Segmented Memory for Serial Bus Applications

Let’s be honest, oscilloscopes aren’t exactly something you can just pick up and use without some sort of help or prior experience. Typically, it takes a bit of time and practice to understand how to use one correctly and make accurate measurements. We don’t want you wasting time trying to figure out how to use your oscilloscope – you should be able to spend your valuable time testing so you can get your designs to market faster. This means you need the right material that can quickly teach you how to use your scope. The Keysight Oscilloscopes team is constantly working to provide you with the materials you need, and expert help so you can spend more time characterizing your designs. We have a lot of resources for you, some of which you may not even know exist.

 

The Educators Training Kit

 

When I was learning how to use an oscilloscope as a young engineer, the resource I found to be most helpful is the Educator’s Training Kit. Don’t let the name fool you - this is not something that only applies to professors and students. It’s helpful for anyone who wants to learn how to use an oscilloscope. The Training Kit includes fifteen hands-on labs that walk you through how to use various features and applications. The labs range from basic concepts, such as triggering and probe compensation, to more advanced measurements such as capturing infrequent events, gated measurements, and using acquisition modes like peak detect. If you complete all of these labs and you still want more, you can also check out the Advanced Training Guide for your oscilloscope model. This guide starts out by reviewing basics, but also covers more advanced labs, including triggering on logic patterns and decoding serial buses. Most of these labs can be completed using the 11 built-in training signals that come with the Educator’s Training Kit, but some guides also include one or two labs that require you to build a very basic RLC circuit as your device under test (DUT). The kit also includes a slide-set on scope fundamentals so you can make sure you really understand the basics before diving into the hands-on labs. The Educators Training Kit is now a FREE option for all Keysight InfiniiVision oscilloscopes so you can learn more about how to properly use an oscilloscope without having to find extra money in the budget.

 

Built-in Help

 

Throw away that user’s manual! Well, maybe not - it could still come in handy. But seriously, everyone hates having to dig through a user’s manual just to figure out something like what one of the trigger options should be used for. There are so many different options and measurement types on an oscilloscope, including some you probably didn’t even know were there. For example, did you know you can get help in seconds right on the screen of your oscilloscope? If you don’t know what something is, just hold down the front panel key or menu button associated with it for a few seconds, and a built-in HELP screen will appear. These HELP screens provide quick information and set-up tips. Bye-bye, user’s manual.

 

Scope Tips from Experts

 

We’re here to help you. That means not only do we provide you with the most accurate test equipment on the market, but we are also available to help you use it. We are regularly posting new videos, blog posts, webcasts, and application notes to help you characterize your designs more easily.  

 

Our Oscilloscope YouTube channel has quick how-to videos, like the Keysight 2-Minute Guru series, along with detailed demonstrations, like Johnnie Hancock’s demo on NFC Testing. The Digital Design and Test Webcast Series is another free resource that offers live, one-hour presentations by some of our experts on various measurement techniques. If you don’t have time to watch the live stream during the workday, you can always watch (or re-watch) it on-demand at a time that works for you. Some of these recordings can also be found on our YouTube channel.

 

When the experts here aren’t working on new videos for you, they are spending their time writing up new blog posts and application notes. These blog posts are another quick way to learn about a topic, while application notes dive deep into the specifics of a certain measurement applications. The Oscilloscope Learning Center offers help on various topics such as scope basics, probing, and applications, and provides links to related videos and application notes for your convenience.


 

I know what you’re probably thinking right now, “Wow, those sound like great resources, but that’s a lot of websites to constantly be checking for new content.” To make your life easier, you can just like our Facebook page. Every time we post new content on all of those free resources I discussed, we usually post a link on our Facebook page as well. The Keysight Oscilloscope Facebook page is the perfect central place to stay up-to-date on all of the new content available.

 

BenchVue

 

BenchVue is a free software tool that can quickly and easily connect your Keysight instruments to your PC in seconds. You can use it to control your instruments remotely and analyze data from various tests. Not only is it a great extension of your oscilloscope’s functionality, but it also has a helpful education feature, the Library tab. The Library tab allows you to type in any Keysight product number and it will return any documentation it can find on that product such as a data sheet, application notes, video demos, user guides, etc.  This eliminates all of that time you would spend searching the web to find these documents and puts them in one convenient location for you.

 

I hope all of these resources prove to be helpful when learning how to use your oscilloscope. We will continue working hard to give you new content to help you in your testing. If you have any specific questions or content requests, just let us know in the comment section below.

KennyJ

"Hey, I Need a Current Probe"

Posted by KennyJ Employee Jan 18, 2017

When I hear someone say this and I ask “why,” the answer is nearly always “I need to measure how much power this thing is using”.  Based on this experience I have come to consider current probe use as synonymous with power measurements. Usually someone is trying to figure out how much power they are using or determine if the supply they have designed or are using is working properly and efficiently. It seems that sooner or later nearly everyone needs to make a current measurement so I thought I would share some of my experience with current probes and making current measurements (I’ve designed some current probes and have some current probe patents). My goal is to help you understand your options, what they are useful for, and what their limitations or drawbacks are.

 

Of course, one of the most common methods for measuring current is to use a digital multimeter. For this article we’re going to skip the DMM because you probably want to see a waveform of how the current changes over time since you are using an oscilloscope.

 

Let’s start with a review of the types of current probes. There are two classes of measurement capabilities—AC only and AC/DC—and primarily two different measurement methods—magnetic field sensing and Ohm’s law. The most general purpose measurement is the AC/DC measurement so we’ll focus on that. When it comes to magnetic field sensing there is a wide range of options—Hall Effect sensors, transformers, Rogowski coils, giant magnetoresistance (GMR), tunnel magnetoresistance (TMR), and many more cool and exotic-sounding approaches, but the most common is to use a Hall Effect sensor teamed with an AC transformer.  For the Ohm’s law approach you throw down a resistor and measure the voltage drop across it. Some people balk at the idea of inserting a resistor in series because of the voltage drop it induces. This is called the burden voltage. These same people that balk at using a current sense resistor tend to not think twice about using a DMM. What these individuals are overlooking is that a DMM inserts a sense resistor in series, usually about 1-5 Ω’s, and measures the voltage drop across the resistor. There is also the contact resistance of the connection points and the resistance of the test leads. In my experience, the DMM series resistance is about 100X greater than the resistance typically used by the Ohm’s law approach.

 

I like to think about the two types of probes this way. If you are going to measure large current (5—100’s A) or fast current (like a switch mode power supply) then you want to use a magnetic field probe. If you need to measure small current or current in sub circuits or current in a physically small product then you want to use the Ohm’s law approach.

 

The most ubiquitous current probe and the one you have probably used or seen is the split-core AC/DC current probe (one example is shown here). These probes use a split ferrite core—a core that has two separable pieces. Usually one part of the core slides back-and-forth or opens like scissors to allow you to clamp it around the wire in your circuit carrying the current you want to measure. The core has a series of windings around it that are connected to the internals of the current probe for measuring the current. Most probes have a negative feedback loop inside that is used to generate an opposing magnetic flux in the core to keep the core from saturating. Sandwiched inside the non-moving portion of the core is the Hall Effect sensor. The Hall Effect sensor is necessary to measure the DC portion of the signal since a transformer only works for AC. In its simplest form a Hall Effect sensor is a conducting (or semiconducting) plate with a bias current flowing along it with voltage measurement points placed perpendicular to the current path. As a magnetic field hits the plate, perpendicular to its center, the electrons flowing across the plate from the bias current tend to shift towards one side or the other, depending on the direction of the magnetic field, and create a voltage potential across the plate. The probe measures this voltage which is proportional to the strength of the magnetic field which of course is proportional to the current flowing throw the conductor being measured.

 

There are a couple of things to be aware of when using this type of probe. First, remember back to when you were studying magnetism and current flowing through a conductor and they would always say “assume an infinitely long, straight conductor”. Well, that’s important to keep in mind. It turns out that changing the shape and position of the wire passing through the probe can change the measurement a little and this creates a repeatability problem with this type of probe. It’s usually not a big deal if you are measuring amperes of current but if you are measuring milli-amperes then it can affect the measurement.  Another issue is the air gap between the two halves of the core. If you change that gap just the slightest amount, by adding side pressure or letting the probe hang on the wire you are measuring you will have repeatability issues when measuring smaller current. There is also the issue of mechanical stress on the Hall Effect element.  Thermally or physically induced stress on the Hall Effect element can change its resistance or induce a piezo electric effect which will cause measurement inaccuracies. It’s always best to let the current probe warm up for 20 minutes or so before use to minimize thermal stresses. Finally there is the issue of residual magnetism. Most probes have a zero/degauss function to address this. The proper procedure then for getting the best results from you clamp-on current probe is to let it warm up, clamp it onto the unenergized wire that you want to measure, zero and degauss the probe and then energize your circuit.

 

The Ohm’s law approach for measuring current is very popular for measuring current in sub-circuits or in targets that can’t tolerate the big long wires for the clamp-on probes (either due to size or because the long wire adds inductance and acts like an antenna picking up external noise). Traditionally folks use a pair of single-ended probes or a differential probe to measure the voltage across the current sense resistor. I am aware of one dedicated Ohm’s Law style current probe, the Keysight N2820A. This probe is a differential probe with two outputs. Each output has different gain for measuring different current ranges. The user can connect one output to the oscilloscope and choose normal or high sensitivity and the probe automatically switches which output goes to the scope. If you have a signal with a large dynamic range, like something that has a sleep state, then you hook both outputs to the oscilloscope and can view both the zoomed-in (high sensitivity) and zoomed-out (normal sensitivity) simultaneously. In this mode the probe has a dynamic range of 20,000:1. This allows simultaneous measurement of very small sleep currents and large current spikes associated with the active state. To use the probe you simply select the current sense resistor value appropriate for the current you want to measure.  The probe will work with anything from 001Ω--1MΩ. You tell the oscilloscope the value of the resistor being used and the scope automatically scales and displays the results in amperes. As an example, using a .050Ω resistor the probe can measure from 100uA to 24A—assuming the resistor is rated to handle the power of the large current.

Screen shot of the N2820A showing zoomed-in data (green) and zoomed-out data (yellow) simultaneously. This is from an IoT weather station.

 

The drawback of the Ohm’s Law approach is that you need to either design in sense resistors or cut the trace and solder them in place. You’ll also need access to some current sense resistors. I usually just get mine from one of the many online component distributors. They stock a wide range of values and power ratings for various current ranges. One great thing to note about using these application specific current sense resistors is that they have very small thermal parts per million resistance variation—the resistance changes very little as the resistor heats up.

 

If you want to dig a little deeper into what is out there just hit our website. You’ll see the full range of current probes we offer. They are of the two main types I described above, magnetic field sensing split-core AC/DC current probes and Ohms law current probes. The web pages show the important specs like maximum and minimum current, bandwidth, price and so on. You’ll also find some application notes, data sheets and videos. If you are making power measurement such as testing a power supply or measuring low power, like a battery powered device, then you should visit the Keysight oscilloscope power page.