RoadTest: Rohde & Schwarz Oscilloscope Kit RTM3K-COM4
Author: Gough Lui
Creation date:
Evaluation Type: Test Equipment
Did you receive all parts the manufacturer stated would be included in the package?: True
What other parts do you consider comparable to this product?: Rohde & Schwarz RTA4004, RTE1104, RTO2014, Tektronix MDO3104, MDO4104C, Keysight Technologies DSOX3104T, MSOX4104A, Teledyne LeCroy WaveSurfer 3104z, 510, 10/10M, 104MXs-B, HDO4104A, HDO6104A, Rigol DS6104
What were the biggest problems encountered?: Numerous small software bugs which have been reported to Rohde & Schwarz for rectification in a future firmware update. This includes problems with saving waveform data for "Vis. Channels" or saving bus table data for serial decoding which involves more than one data bus which cause the oscilloscope to lock up. It was also discovered that the oscilloscope can be locked up remotely via the network interface upon receiving certain packets. Cursor recalculation for X&Y cursors on FFT displays did not seem to work correctly for levels. False start-bit detection for UART in case of a short transient glitch. Persistence does not affect digital channels. Other minor issues, typographical and grammatical errors also reported.
Detailed Review:
Rohde & Schwarz RTM3004 RoadTest
by Gough Lui
June - July 2018
When it comes to electronics, the multimeter is probably the first instrument everyone buys. The oscilloscope is probably the second. An oscilloscope is a vital part of an electronics workbench, enabling insights into time-varying signals. As the bandwidth of these signals and nature of these signals change, so do the oscilloscopes. As most electronics design in the present time include some elements of digital circuitry and even radio-frequency (RF) circuitry, oscilloscopes have evolved to provide serial decoding, digital logic channels and spectrum analysis capability for proper mixed-domain operation.
Thanks to element14 and Rohde & Schwarz, it is a great honour to be one of the three lucky people from the community to receive a fully-specced-out RTM3004 for RoadTest review. It’s no ordinary RoadTest and as a result, I’ve tried to give it the attention it deserves by producing this mega review. I hope you can agree that I did the unit justice.
Owing to the versatility of the RTM3004 and the amount of content generated during the RTM3004 RoadTest, this RoadTest review post is a “slimmed down” summary of the most important findings. Links to in-depth posts focusing on each of the major aspects is provided at the end of each section and I strongly encourage readers to take the time to visit these posts and find out more. These posts go into some of the test aspects, potential caveats, bugs found and can make for interesting reading even if you’re not in the market for a new oscilloscope right now.
As always, thanks for taking the time to read my review – I hope you find it useful, interesting and entertaining. If you found any of these documents deserving, I’d appreciate it if you would like, rate, leave a comment, bookmark and/or share it with a friend.
Please note that the information in the review is believed to be correct at the time of publication – but due to the nature of continuous improvement, it is likely that some problems noted may be rectified by the time you read this. I will do my best to note such developments in the updates which appear at the end of the article.
While the RoadTest is mainly concerned with the Rohde & Schwarz RTM3004 oscilloscope, it would be remiss of me to only focus on that particular unit, seeing as test equipment purchases are often a “big ticket” item where it may pay to shop around, especially as needs and applications vary.
As a result, I spent some time looking around the major suppliers (including Rohde & Schwarz, Tektronix, Keysight, Teledyne LeCroy and Rigol) to see what was on offer. The criteria that needed to be met was a four-channel unit with 1Ghz bandwidth (upgradeable or base) as a minimum.
It seems Rohde & Schwarz’s RTM3004 is rather competitively placed in the market, being the lowest priced 1Ghz offering in Rohde & Schwarz’s catalog. Being offered at a price similar to the lower-end 1Ghz bandwidth options from Tektronix and Keysight Technologies, it offers noticeably improved vertical resolution, input sensitivity, memory depth, channel-to-channel isolation and screen resolution. As a result, the RTM3004 is a sound choice if only by comparison.
The biggest threat, however, is probably the Teledyne LeCroy WaveSufer 510, which retails at a slightly lower price and offers a higher sample rate, waveform update rate, the ability to do 18/36 channel digital acquisitions at up to 250/500Mhz, a comprehensive suite of protocol decode options and a larger screen of equal resolution. Where the RTM3004 strikes back is with better vertical resolution of 10-bits, higher vertical sensitivity, more memory, better channel-to-channel isolation and the ability to be upgraded for arbitrary waveform generation/pattern generation. Even then, it’s practically a draw depending on what your needs are.
The RTM3004’s greatest weakness is probably its limited waveform update rate and lack of segmentation by default and a limited library of protocol decoding options. The former can be ameliorated by the RTM-K15 option which provides an industry-leading 400Mpts memory, segmentation and an improved 700,000 waveforms per second update rate. The latter, however, may entail upgrading to a whole new oscilloscope depending on which protocol you’re interested in.
As a result, it makes sense to choose wisely when deciding on an instrument purchase, thinking about your current needs as well as upgradeability to meet future needs, all within the budget you have available. While paper specs are nice to look at, they don’t tell the whole story – for example, boot times, ease of use, interface design, actual-application performance, limitations, probes available and their performance, etc. As a result, it pays to look at how the instrument performs as a system as well.
For the full comparison matrix, see this post: R&S RTM3004 RoadTest in Depth – Chapter 1: Market Survey.
In all, the RTM3004 main unit came very well packaged against damage using copious amounts of egg crate foam, which was not in vain as this particular unit endured a long shipping process which entailed dents and tears in the cardboard and yet comfortably survived. The main unit made a very strong impression with its large 10.1” glossy touch-screen dominating its front panel real-estate. A complement of traditional buttons and knobs covers the most important features, separated by function. The bottom edge is flanked by an array of ports, representing the impressive abilities of the RTM3004 especially with optional features unlocked. The unit feels well built for the most part, with only a slight creak in the plastic near the digital logic ports. The large honeycomb vents and fan should mean low noise and good airflow.
The unboxing process was pleasurable, as packing lists are included to check for completeness and thoughtful inclusions such as the accessory case are bundled in. Each of the probes are separately packed in a complete kit and many of these kits contain more components than might actually be needed at any one time. The quality of the included passive 500Mhz probes was quite impressive, feeling precise, slim and comfortable to hold with quite flexible coax and a fine sprung tip. They were also well matched with the inputs, making manual compensation adjustment unnecessary. The digital logic pods were also very solidly built, with their connection ribbons being relatively thick and hefty. The break-out leads, however, were a little thin but were still very much serviceable. The included clips are, however, extremely useful for accessing the “legs” on DIP and broader-pitched SMD chips owing to their fine shape and are a very welcome inclusion.
For its capabilities, it impressed me with its relatively compact size and low weight. Compared to my entry-level Rigol DS1102E, it offers so much more without consuming more bench real-estate in real terms. Set-up was a breeze, aided by a modern touch-enabled interface, resulting in no hassles with firmware upgrades, probe compensation adjustment, taking screenshots or running a self-alignment.
For more juicy photos, see this post: R&S RTM3004 RoadTest in Depth – Chapter 2: Unboxing.
While on-paper specifications are easy to compare, they only tell part of the story. While a device might be excellent on-paper, it could be difficult to use or have a number of important limitations. In this section, I look at the usability aspects of the RTM3004 – just how enjoyable is it to use on a daily basis? Are there any annoyances which get in the way of getting things done?
I’m glad to report that, on the whole, using the RTM3004 was an intuitive and highly satisfying experience. The documentation available was clear, well-written and fully illustrated, reducing the learning curve and effectively introducing newcomers to the Rohde & Schwarz touch interface.
The RTM3004 is fast to start, taking less than 10 seconds and has an intuitive and responsive touch-screen interface that is as simple to use as most mobile applications. The 10.1” screen is large, sharp, clear and glossy. The rhomb menu, quick toolbar, short menu and dedicated front panel buttons provide a number of ways to accomplish actions. Having the knobs available preserves the “analog” interface and eases the transition from non-touch instruments, although the knob acceleration makes it feel less “precise” in my opinion. The RTM3004 is versatile enough that you can directly key-in most values using an on-screen keyboard. The panel is also smart, using colour-coded LEDs with adjustable brightness to provide feedback about channel status. External USB input devices are supported, so whether you like to touch the screen, twiddle knobs, push buttons or use a keyboard and mouse, the RTM3004 has you covered. The unit is also whisper-quiet, with its fan barely noticeable in ordinary use.
The RTM3004 offers eight measurement slots and a wide array of automatic measurements. Cursors are available for manual measurements. Statistics mode is supported to provide mean and standard deviation values across acquisitions. Automeasure is available on a single channel, allowing for automatic measurements and labelling of parameters. Five math channels are available with two oprands each and a wide array of mathematics function. This was very much as expected from an oscilloscope of this class.
During these tests, I (informally) measured the channel input noise at an average RMS value of 108.11µV which is quite unexpectedly low and explains why I find the traces from the RTM3004 to be “quiet” compared to some other oscilloscopes I have used before. Because of this, sometimes I’m not aware that I’m actually measuring a small signal at the end of a 10:1 probe, so the signal reaching the oscilloscope is miniscule.
It is possible to save screenshots, instrument settings, displayed waveform data, buffered waveform data, history waveform data, reference waveform data and power analysis reports. The oscilloscope features some internal storage but can also access USB Mass Storage devices formatted in FAT/FAT32. A OneTouch feature is also provided so multiple types of data can be saved at a single keypress into a single .ZIP file for easier data management. Filenames are limited to eight characters, which is unfortunate.
The only major detraction was an issue in exporting Visible Channels in the waveform save dialog which resulted in the oscilloscope locking up, where individual export of each channel worked just fine. The amount of time spent debugging the problem as a little irritating, but the issue has been reported and is expected to be rectified in the next firmware update.
The RTM3004 has included within its base offering a digital voltmeter, trigger counter, FFT display and mask test capabilities which is an additional sweetener and makes the instrument useful for automated testing applications and basic RF tasks even without the Spectrum Analysis option.
The RTM-B15 History and Segmented Memory option proved to be extremely useful and highly recommended, as it upgrades the 40Mpts memory into a segmented memory of 400Mpts per channel. This allows you to capture anywhere from 5 to 34,952 segments for replay and analysis later, with fast segmentation ensuring a minimum blind time to ensure infrequent events are captured. With an industry-leading amount of memory, there is also less need to compromise on sample rate or record length.
For the full discussion, see this post: R&S RTM3004 RoadTest in Depth – Chapter 3: Usability Aspects.
Serial interfaces of a number of types are in common use in embedded systems and having the ability to analyse and troubleshoot these communications in the digital domain is one part of a mixed-domain solution. The RTM3004 has the following protocol decode options for triggering and decoding available as options at the time of writing:
As each of these protocols are offered as a separate option, you can buy only the decoders which are useful at the present moment and upgrade later as your needs increase. The most useful are probably I2C, SPI, UART and possibly audio for embedded applications. Those working in automotive development would probably be interested in CAN and LIN. Those working in aeronautical or aerospace development would be interested in MIL-STD-1553 and ARINC 429.
I was able to evaluate the protocol decoding for SPI, UART and I2C as these are common interfaces which can easily be encountered in simple microcontroller-based embedded systems. Setup and decoding was straightforward, with the ability to display the decoded data in bus table and on-trace comb style display. Triggering worked positively, as did warnings of data aliasing at low sample rates and deep memory history mode for recording infrequent bursts of data on the bus. Custom data rates for UART of 250kbit/s and 2Mbit/s were tested without difficulty although the actual rate did vary slightly from the set rate. It was determined that the between-sample dead time is practically zero when operating in the fast segmented memory mode. Mixed protocol decoding was also demonstrated, with some limitations due to certain protocols requiring the use of two of the four available decoder slots to cover RXD and TXD or MOSI and MISO. Issues found include long data lines in the bus table for SPI being “cut off”, glitches causing false detection of a start bit with UART decodes and with saving the bus table for protocols with multiple data lines –issues which have been reported.
While the RTM3004 does have the ability to generate demonstration signals for the other types of buses through the pattern generator or arbitrary waveform generator, I did not use them as I felt this would be somewhat unrealistic. However, given that the features offered by most protocol decoding options are fairly similar, I feel that this is not a major omission.
Depending on your application, obtaining the appropriate protocol decoder options would be recommended. However, it is worth keeping in mind that the RTM3004 offers a more limited protocol decode option set compared to some of its competitors, so if it is necessary to decode protocols not in the options list, it may be worthwhile looking at alternatives.
To see it being used, see this post: R&S RTM3004 RoadTest in Depth – Chapter 4: Protocol Analysis.
Another difference between an ordinary oscilloscope and a mixed domain oscilloscope comes down to the presence of digital input channels. In the case of the RTM3004, the RTM-B1 Mixed Signal option provides 16 digital channels to turn the RTM3004 into a mixed domain oscilloscope.
Having the RTM-B1 Mixed Signal option is highly recommended if you intend to do mixed-signal work that requires the parallel monitoring of multi-bit digital buses. The hardware offers impressive specifications including the ability to monitor signals up to 400Mhz running between 0.5 to 40V peak-to-peak with a threshold that can be set ±8V in 25mV steps and adjustable hysteresis. It offers 40Mpts on every channel when running with all 16-channels enabled or 80Mpts when running with 8-channels enabled. The digital channels can work together with the analog channels to bring up to 20 simultaneous channels and protocol decoding on the digital channels is also possible. The use of a relatively long coax ribbon with external pods that can easily be detached allows for more versatile positioning of the oscilloscope and device under test which can be quite helpful especially if working on larger equipment.
During testing, I found the digital channels to work well and I was not able to push them to their absolute limits owing to the difficulty in generating and conveying a 400Mhz signal to the unit. Testing was performed on a counter at 200Mhz and an LFSR at 100Mhz which was easily successful demonstrating the memory and search capabilities. The probe was also capable of identifying timing jitters and glitches due to deficiencies in my FPGA design owing to the quick-and-dirty design methods employed. The only issue appeared to be that persistence does not seem to affect the digital channel displays, which has been reported to Rohde & Schwarz.
To see more of the spaghetti that ensued, see this post: R&S RTM3004 RoadTest in Depth – Chapter 5: Digital Probe Channels.
With modern electronics operating at ever-lower voltages and power efficiency being a prime concern amongst portable electronics, analysis of switching power converters is a common application for high-end oscilloscopes. While the RTM3004 can be used ordinarily to analyse such signals, this is made much easier with the RTM-K31 Power Analysis option which provides applications pre-configured for measurement tasks such as evaluating power quality, harmonics, inrush current, power consumption, slew rate, modulation, dynamic-on resistance, efficiency, switching loss, safe-operating area, turn on/off time, ripple, spectrum and transient response.
Use of the power analysis feature is safest and best performed with the use of specialised active probes to provide the isolation necessary to protect the oscilloscope inputs and the user. Unfortunately, as I don’t have access to any of these active probes and deskew fixtures and am not currently designing a switching mode converter, I could not fully assess the features offered by all of the power analysis option applications.
However, in testing separated extra-low-voltage circuits using the passive probes and resistive shunt, it seems that the tools do simplify the amount of work necessary to consistently analyse power quality and load characteristics. The reporting options also provide additional value to those who are routinely performing power analysis with their oscilloscope, making it a potentially worthwhile option for those users.
For details on the attempted experiments, see this post: R&S RTM3004 RoadTest in Depth – Chapter 6: Power Analysis.
The RTM3004 can be more than just an oscilloscope. With the addition of the RTM-B6 Waveform Generator and 4-bit Pattern Generator option, it’s possible to generate regular functions, modulated functions, bit patterns and arbitrary waveforms for testing devices from the oscilloscope itself.
The option provides a basic 4-bit pattern generator with a number of inbuilt random-data serial protocol options, counter and arbitrary pattern capability up to 8192 points with a rate up to 20Mhz and output voltage between 1.5V to 3.3V. While this can be useful for demonstration purposes, its output being connected to four lugs on the front panel makes it inconvenient for other uses.
The function generator is capable of generating Sine (0.1-25Mhz), Pulse, Rectangle (0.1-10Mhz), Ramp, Triangle, Sinc and Exponential (0.1 to 1Mhz). with noise (0-100%) and AM/FM/ASK/FSK modulation ability with variable modulation depth/shift frequency and a fixed modulation input frequency.
The arbitrary waveform generator is capable of providing up to 10Msample/s rates for up to 32,000 memory points and output voltages either 20mV to 10V peak-to-peak for High-Z and 10mV to 5V peak-to-peak for 50 ohm.
In all cases, the parameters for these features are not class-leading when compared to dedicated standalone instruments. However, despite this, the option does provide enough performance for many tasks. Its main advantage is the fact it is already integrated into the RTM3004, making it easier to set-up and control remotely, while taking no extra bench space or power points. If the specifications meet your needs, the RTM-B6 Waveform Generator and 4-bit Pattern Generator option could be well worth having.
For a peek at what can be done, see this post: R&S RTM3004 RoadTest in Depth – Chapter 7: Arbitrary Waveform, Function and Pattern Generator.
While the previous sections all looked at using the oscilloscope interactively, many users expect to use test equipment via remote control or as part of an integrated testing solution. Fortunately, the Rohde & Schwarz RTM3004 offers a USB device port and an Ethernet port for PC or LAN connectivity.
When it comes to remote operation, the RTM3004 was extremely impressive, offering a wide array of flexible choices when it comes to interfacing, communicating and controlling the unit. The LAN interface impressed with a browser-based interface that catered for changes in configuration, SCPI command execution, file upload/download, had basic password protection and a high-performance remote front panel and screen capture facilities. The faithfulness of the remote front panel in responding to browser-based touch, drag, keyboard input, virtual knob and button made it a pleasure to use and an excellent choice if you need to duplicate the display (e.g. for educational purposes to project into an auditorium). This worked reliably even from a smartphone over Wi-Fi.
Where LAN is not suitable, three USB modes are provided. USB MTP allows for driverless file-based operations, allowing for download and upload of files but also accessing “live data” which is generated on request. This is at the expense of SCPI command support. USB VCP presents a CDC-based COM port, simplifying application development, allowing raw SCPI commands and responses to be transferred over a virtual COM port. Finally, USB TMC presents a familiar IVI interface for use with VISA libraries.
The instrument is provided with IVI.COM, LabView and VxIPnP drivers. Further to this, it is provided with the RSCommander software which provides similar functionality but also adds the ability to automate operations using a Python-based PyVISA script facility. The R&S RTx Report Creator also allows for the creation of PDF reports from recorded report data from the RTM-K31 Power Analysis option.
The only minor issue appears to be the LAN interface locking up the unit when an unusual packet sequence is received which was reported to Rohde & Schwarz for rectification in a firmware update.
To see it in action, see this post: R&S RTM3004 RoadTest in Depth – Chapter 8: PC/LAN Connectivity and Software.
The Rohde & Schwarz RTM3004 is a well-positioned oscilloscope that provides better value than most of the contemporaries. It offers a higher vertical resolution of 10-bits, larger memory depth of 40Mpts by default (can be upgraded to 400Mpts with segmentation with RTM-B15 option), >50dB channel-to-channel isolation, RTM-B1 option offering 16-channel digital probe ability with 400Mhz maximum frequency, RTM-B6 option for onboard pattern, function and arbitrary waveform generation and a large 10.1” 1280x800 capacitive touch-screen providing higher resolution.
The unit arrived well-packed and occupies a compact footprint. In use, the unit was quiet, fast to boot and capable. The interface is responsive and intuitive to use, with a number of options for interfacing in case you prefer touch, buttons, knobs, keyboard/mouse or remote access. Onboard measurement and math channel functions are extensive and data save features provide the ability to export screenshots, channel data, display data, history data, settings, reference waveforms and power analysis reports. The documentation is also an easy read being clear and comprehensive featuring a large number of device screenshots.
The RTM3004 can be turned into a fully mixed-domain oscilloscope through the addition of options, including RTM-B1 for 16 digital channels capable of up to 400Mhz input frequency and 0.5 to 40V peak-to-peak swing with configurable threshold ±8V in 25mV steps and hysteresis. Protocol decoding is available through options RTM-K1 for I2C and SPI, RTM-K2 for UART/RS-232/RS-422/RS-485, RTM-K3 for CAN and LIN, RTM-K5 for Audio (I2S, JK, RJ and TDM), RTM-K6 for MIL-STD-1553 and RTM-K7 for ARINC 429. The power analysis option (RTM-K31) adds additional value for those who perform power analysis regularly and works best if used with specialised high voltage differential active probes and active current probes with a deskew fixture. The onboard pattern, function and arbitrary waveform generator can be enabled through the RTM-B6 option. While the specifications of these devices aren’t particularly class-leading compared to standalone bench-top units, the inclusion and integration into the RTM3004 is an asset for remote control and automated testing scenarios and helps to reduce benchtop clutter. Despite the limitations in specifications, I still found it adequate for many applications.
One major strength was the remote-control abilities of the RTM3004, with the remote front panel being extremely responsive and easy to use, requiring just a web browser. The variety of connectivity options through LAN and USB should cater for almost all conceivable scenarios. RSCommander and R&S RTx Report Creator add further value by providing further functionality.
The RTM3004 proved to be an extremely versatile instrument. The only areas where I could fault it were to do with its relatively limited serial decoding option set compared with some competitors and a number of bugs and feature limitations found during the review. The latter have been reported for possible rectification in a future firmware, although many of them can be worked-around in some way. Owing to the nature of the unit being a US-supplied unit, RTM-K18 Spectrum Analysis option was not available for review during the RoadTest period.
Thanks to Rohde & Schwarz and element14 for selecting me as the RoadTester and supplying the unit for review. Special thanks to rscasny for running the RoadTest program and rich@rohdescopesusa for handling my feedback e-mails.
Thanks again for taking the time to read my review – if you found any of these documents deserving, I’d appreciate it if you would like, rate, leave a comment, bookmark and/or share it with a friend.
If you’re interested in how some of the test signals were generated, see this post: R&S RTM3004 RoadTest in Depth – Appendix: Making the Test Set-Up.
In case you’re wondering what I’ve been up to, feel free to visit my personal blog at http://goughlui.com.
This section is reserved for any updates to the review.
* 23-07-2018 - Slight fixes to formatting as some images were oversized.
* 17-02-2019 - New Firmware Released with K36 Bode Plot Analysis option.
* 15-05-2020 - New Firmware Released with K37 Spectrum Analysis option, taking over from K18.
Top Comments
Very nice roadtest review of this fine instrument, I really enjoyed your witting style and the insights that you sprinkled through the review.
Well done!
Gene
Well done Dr Gough.
I thought your review would be comprehensive and was wondering how long the page would be, but the approach you've taken is great.
I'm not in the market for such a beast, but clearly…
Thanks for the comment - you do bring up a very interesting point.
I find that, very often, during a review of a piece of test equipment that the test equipment itself ends up teaching me something. Sometimes…