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Keysight S-Series oscilloscopes vs the RTO2000 – Part 2

Blog Post created by melissakeysight Employee on Dec 7, 2016

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 

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