Rohde & Schwarz Oscilloscope Kit RTM3K-COM4 - Review

Table of contents

RoadTest: Rohde & Schwarz Oscilloscope Kit RTM3K-COM4

Author: snidhi

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?: The other oscilloscopes in this price range are from Rigol, Siglent, Keysight Technologies, Tektronix, Hantek and OWON.

What were the biggest problems encountered?: To access the online content for the R&S oscilloscopes you have to make a login which is verified by the R&S customer care and only then the login is valid.

Detailed Review:

This is a detailed review of the Rohde & Schwarz Oscilloscope Kit RTM3K-COM4Rohde & Schwarz Oscilloscope Kit RTM3K-COM4

 

Motivation for the Road-Test

 

I have worked with many diverse oscilloscopes in my job profile as an electronics engineer. All thanks to the research institute where I am located. A few of them to name are LeCroy WaveRunner 610Zi, Tektronix MSO/DPO70000 series and Keysight Serie 3000T and ofcourse Rigol (personal). I have also laid my hands on Rohde & Schwarz power supply and R&S signal generator but not yet on one of their scopes. Therefore, this road test is interesting opportunity for me to evaluate the Rohde & Schwarz oscilloscope which is available at a good price point.

 

I bought my first personal oscilloscope Rigol MSO 4034 with 500 MHz Bandwidth three years ago in 2015 when I started tinkering with electronics at home beside my day job. To buy this oscilloscope I spent almost one year investigating different scope options and their pricing (well... who doesn't like a good deal) and saving money for last 5 years. I spent most of the time analyzing the real BW of scopes, what are the upgrade options as many scopes are locked only in software and not in hardware, what drives the pricing and the state of art electronics used in oscilloscopes, the quality of probes and their impedances, noise floor levels in the oscilloscope hardware etc. In the end I pushed my budget from 3000 Euros to 7000 Euros and got my first oscilloscope because this is an investment for a life time. I think investing in good measurement instruments is paramount specially legacy devices such as multimeter, oscilloscope and a good soldering station.

 

In this road-test; I put all my investigations to use so other future buyers can deeply analyze what they are paying for and what they get is a trade off which is balanced very finely by the oscilloscope industry. 

 

There is a famous joke in my lab that one could buy a car for the same price as a scope but the oscilloscope is worth it. And I don't own a car.

 

Table of Contents

 

Introduction

I want to thank Rohde & Schwarz Oscilloscope Kit RTM3K-COM4 and element14 for selecting me for this Roadtest.

 

The current revolution in oscilloscope pricing can be attributed to how cheap the ADCs have become. R&S RTM3004 is a high performance scope placed at the border of the economical range. Such devices are necessary for analog and even digital engineers. They can solve many issues which cannot be debugged in software only mode.

 

Oscilloscopes are the Ferrari of the electronics debugging world.

 

To begin with one can argue, as to why do we need an oscilloscope? Many engineers today are happy working with a multimeter and "printfs". But adding an oscilloscope to the workbench can open a whole new world of signal measurements which cannot be done with a simple instruments. A good scope is handy when measuring fast and clocking signals, ripple and noise measurements in power devices, debugging bus communication (I2C, CAN, RS232), signal FFTs and list is infinite. They are a valuable debugging tool to measure outputs at the analog end and on pcb-side. I encountered many problems where it made me realize that the origin of the issues may not always be software and tweaking around with a probe on the hardware can give valuable insight.

 

As quoted by Wikipedia

Oscilloscopes are used to observe the change of an electrical signal over time, such that voltage and time describe a shape which is continuously graphed against a calibrated scale. The observed waveform can be analyzed for such properties as amplitude, frequency, rise time, time interval, distortion and others. Modern digital instruments may calculate and display these properties directly. Originally, calculation of these values required manually measuring the waveform against the scales built into the screen of the instrument. Other signals (such as sound or vibration) can be converted to voltages and displayed.

 

Interesting Historical Facts About Oscilloscopes

 

Karl Ferdinand Braun was a German inventor, physicist and Nobel laureate who invented the first cathode ray tube oscilloscope in 1897. Braun was born in Fulda, Germany, and educated at the University of Marburg and received a Ph.D. from the University of Berlin in 1872.

 

Reference: Oscilloscope Fundamentals Rhode und Schwarz Document

 

He applied an oscillating signal to horizontal deflector plates and a test signal to a vertical deflector in a phosphor-coated CRT. The plates produced transient plots of electrical waveforms on the small phosphor screen. This invention evolved (Figure 2) into a measurement instrument and was gradually improved over the next 50 years. The advancement by engineer Howard Vollum in 1947 that made the oscilloscope a highly-useful instrument, allowed a trigger to control the sweep function for the first time. Reference

 

The era of digital oscilloscopes began in the 1980s with the rise in fast ADC and memory recording integrated circuits. And combined with the advancement in the waveform display screens the Oscilloscopes have taken over the world.

Reference: Growth Time-line of the Oscilloscopes

Unboxing and Setup

 

The Rohde & Schwarz Oscilloscope Kit RTM3K-COM4Rohde & Schwarz Oscilloscope Kit RTM3K-COM4 was delivered in a big box well secured with cushions as packing material. Rohde & Schwarz being a German company I was a bit surprised that the scope came from the U.S. And after minor issues with the import authorities at the German border and them asking the same question to me (that why I imported a German brand product from the U.S. (yeahh logic..)) and help from the Rohde & Schwarz guys the device landed on my doorstep.  R&S and element14 did pay the import taxes so I did not have to pay any extra money to the authorities . The packaging is very important when such sensitive electronics has be delivered half way across the globe and R&S did a good job.

 

{gallery} Unboxing RTM3004 RTM3K-COM4

Fig 1: The Delivery

Fig 2: The Opening Ceremony

Fig 3: The Opening Ceremony

Fig 4: The Unboxing

Fig 5: The Unboxing

Fig 6: The Unboxing

Fig 7: The RTM3004 RTM3K-COM4

Fig 8: The RTM3004 RTM3K-COM4

Fig 9: Power Cables

Fig 10: The Probe Set Delivered

Fig 11: The Probe Set

Fig 12: The Digital Probe Set

Fig 13: The RTM3004 RTM3K-COM4 First On

 

Fig: Unboxing video and Description of RTM 3004 oscilloscope

 

License and Updates in R&S RTM 3004

After a quick software update from R&S I was ready to go

Fig: Updated Software

 

A list of license available with the oscilloscope. As mentioned already the Spectrum Analyzer license will be available in September and was not given together with the device.

Fig: List of licenses available with in the pack

First Impressions of R&S RTM 3004

 

The first operation of the RTM3004 RTM3K-COM4 was quite different. If you are used to using oscilloscopes from Keysight or Tektronix (like me) then there can be a small kick in the start. I had felt the same kick when I had started working with LeCroy. I needed sometime (like half a day) to figure the control panels out and it was smooth sailing after that. Rohde & Schwarz have their own unique philosophy and identity for their each line of devices. This oscilloscope has no operating system but uses the an App button to access all its features.

 

In my experience with the Rohde & Schwarz devices and instruments upholds its quality and robustness over pricing. I have used R&S 25 years old devices in my lab still functional as good and with minimum repairs from the time they were bought.

 

The RTM3004 from Rohde & Schwarz is a mixed signal oscilloscope which includes logic and protocol analysis together with analog waveform visualization. Signal integrity measurements are key for hardware engineers and signal content analysis for bus protocols can be helpful to software engineers while troubleshooting. This oscilloscope has four analog channels and 16 digital channels where both analog and digital signals can be acquired synchronously and correlated in time.   

 

List of features in RTM3004 RTM3K-COM4

 

  • Oscilloscope with sampling rate upto 5Gsamples/sec
  • Logic Analyzer with 16 digital channels
  • Protocol and bus analyzer I2C, SPI
  • Waveform and Pattern Generator
  • 3-digit Voltmeter DVM and 6 digit frequency counter on each channel
  • FFT functionality where signals can be analyzed upto 128k points.
  • Mask Test Mode to analyze whether a specific signal lies within defined tolerance limits or not.
  • History and segmented memory mode to scroll through past acquisitions and analyze the data using the oscilloscope tools, e.g. protocol decode and logic channels.
  • Power measurements for switch mode power supplies and harmonic current measurements.
  • Spectrum Analyzer with RTM K-18 (unavailable yet)

 

The RTM3004 has quite some legacy to uphold and is a perfect answer if one is looking for an oscilloscope in 1 GHz Bandwidth range with high sampling rate and many other classical features integrated in one device.

Fig: A quick guide for RTM3004 RTM3K-COM4

 

Comparison of the RTM3004 with other oscilloscopes

 

A quick feature contrast of RTM3004 with other available with RT Series R&S oscilloscopes

Fig: Comparison Chart

 

A quick comparison of the oscilloscope with its competitors reveals that RTM Series does fairly well although it is priced lower cheaper for its range.

Fig: Specifications Comparison

 

A more detailed look into the competition with other featured oscilloscopes with respect to R&S RTM 3004. The other oscilloscopes lie in the similar price range and specifications range as the RTM 3000. I have marked the most important parameters in red for comparison. 

Fig: Tektronix vs R&S RTM 3000

 

Fig: KeySight vs R&S RTM

 

Fig: LeCroy vs R&S RTM

 

A quick comparison of the Rigol MSO 4034 and RTM3004 RTM3K-COM4

 

Fig: Built Comparison between Rigol MSO4034 and RTM3004

 

 

Comparing the different oscilloscopes by weightWeight Comparison

RTM3004 RTM3K-COM4

with 1GHz BW

 

3.4 Kg

Rigol MSO 4034 with

500 MHz BW

 

4.3 Kg

 

Front and Back Panel Description

 

A quick look at the front panel of the oscilloscope and its features. One key feature here is that there is only one control for all the 4 channels as compared to traditional oscilloscopes where each channel has a separate control button. The channel selection is well color-coded but can get confusing at times. The removal of other 3 channel controls was done to increase the screen size it seems.

 

Fig: Front Panel Description

 

Fig: 16 Logic Analyzer digital channels on the side panel

 

A detailed look to the side panels and ports of the oscilloscope

 

{gallery} Complete look of R&S RTM3004

Fig 1. Back Panel

Fig 2. USB and LAN Support

Fig 3. Extra Power Control with Lock Control

Fig 4. Fan on the side

Fig 5.

 

A few negative points that I did not like about the design of the oscilloscope

There are 2 legs at the front of the oscilloscope which are not very sturdy and seem to be made of cheap plastic. They also don't have a rubber padding as well. It happened few times that the scope became unstable at the table. It was quite annoying.

 

There is no handle to carry the oscilloscope but only a gap like thing which is support to act as a carrying support. This increases the risk of dropping the equipment on the floor. It is not a good design and a handle is more sturdy and secure. Not a fan of this either as I was moving the scope many times between my lab and home. Bring back the handle!

 

Functional Building Blocks of an Oscilloscope

 

Here we are going to look into the basic block diagram of an oscilloscope and fit it to the RTM3004 and what this scope offers in terms of internal ADC, vertical system, horizontal system acquisition and processing.

 

Specifications Overview of the RTM3004

 

A detailed list of the specifications of the oscilloscope is given here and have been verified in this road-test. A quick look at its competitions gives an idea of the pricing vs quality where RTM3004 is a winner.

 

Fig: Specifications Overview

 

Functional Description diagram

Fig: Simple oscilloscope Block Diagram

 

  • The Vertical System takes the input signal and conditions the signal via attenuator then through the amplifier and into the ADC.

 

Fig: Vertical Specs of RTM3004

 

  • The Analog to Digital Converter ADC samples the signal at discrete points in time and converts the signal voltage at these points into digital sample points. RTM 3004 has a 10 bit ADC. The sampling rate of the internal ADC is typically 5 times higher than the oscilloscope BW.

Fig: ADC Sampling how it works

 

To avoid any aliasing the Nyquist rule should be followed and the sampling rate should be at-least 2x higher than the signal frequency.

 

  • Wfm Update Rate: The high update rate of 64,000 waveforms/sec reduces the blind-times in the scope so it does not miss the critical signal faults in the display. It means how fast a scope can trigger process the captured data and display it on the screen.
  • Horizontal System: The horizontal system's sample clock determines how often the ADC takes a sample. The rate at which this clock "ticks" is the sample rate (Unit: samples/sec). Then the sample points are stored in memory as waveform points and they make up one waveform record.

Fig: Horizontal system working Diagram

 

  • The relationship between sampling rate acquisition time and record length is quite complex

Fig: How record length is determined

Fig: RTM 3004 Horizontal System specs Ref

Fig: RTM 3004 Acquisition System specs Ref

 

Record length = Sample Rate  x Time Scale x Number of Divisions (10)

 

Sampling RateTime Scale X Number of Div (10)

Record Length

5 GS/s (ch1)100 ns/div5K samples
2.5 GS/s (ch1 and ch2)100 ns/div2500 samples
5 GS/s (ch1)100 us/div5M samples
2.5 GS/s (ch1 and ch2)100 us/div2500 Ksamples

 

Hence one can see here that the record length is dependent on the timescale and the sampling rate. The higher the sampling rate the better the output and indeed higher the price!!

 

The advantages of higher sampling rates are

  1. Higher signal fidelity
  2. Better chances of capturing glitches
  3. Higher resolution between sample points
  4. The higher the sampling rate; the effective BW of the scope is higher.

 

Importance of Oscilloscope memory depth

 

A deep memory allows for capturing longer time periods while maintaining high resolution (fast sampling rate). The zoom in capability into the signal is also increased. The memory depth determines the maximum possible record length for one acquisition.

 

Fig: RTM 3004 Memory depth vs record length

 

To put it in a simple manner; using the maximum record length of 40Msamples/sec at 5GS/sec (full sampling rate) with the above formula the oscilloscope will capture a signal 8 millisecond in length.

 

A combination of long record length with fast waveform capture rate allows to search for transients in the signal such as jitter and glitches. RTM 3004 offers much higher memory depths as compared to its competitors and this sets it above the others.

 

Fig: Comparing memory depths  with other oscilloscopes

Fig: Memory Segmentation Specification for the RTM 3004

 

Types of memory and Storage in R&S RTM 3000

 

Here is a short description of the different memory types and their sizes with functionality in the oscilloscope. The 512 Mbyte Flash memory on main board stores the device ID, the instrument firmware, the factory calibration/alignment data and the current alignment data. It also stores all the instrument settings, user data and current state of the oscilloscope.

 

Hence the user data or the settings are not deleted after power-off. So one can turn off the power and come back later are resume measurements from where you left.

Fig: Types of memory

 

This oscilloscope has also a Secure Erase Feature which allows the user to clean the internal flash memory using their specific Sanitization Procedure for any security reasons. This is a specific Instrument Declassification procedure to allow the safety of user data for high secure environment. After declassification self alignment must be done.

 

Passive Probes Description

The RTM 3004 came with four 500 MHz passive probes RT-ZP10 with the probe rise time of 700 ps and input capacitance of 9.5 pF.

Fig: 500MHz BW passive probe

 

Fig: The Probe RT-ZP10 Kit

 

Each probe must be adjusted for low frequency LF compensation and for high frequency HF compensation. When the probe is connected to the input LF compensation must be done to match the probe cable capacitance to the input scope capacitance. A poorly compensated probe can show distorted waveforms.

Fig: LF Probe Compensation

 

HF Compensation Compensation is not a must but should be done if faster signals are being measured close to the 700 ps rise time range.

 

External Measurement Device Setup used

 

Here is a list of devices that were used for measurements and experiments during this road-test. A brief idea of these devices and their functionality have been presented.

 

Evaluating R&S RTM 3K Oscilloscope Bandwidth and Rise time

 

Bandwidth is the most important specification when it comes to selecting the right oscilloscope for analog or digital measurements.

 

Calculating the Oscilloscope Bandwidth of R&S RTM 3004

The oscilloscopes have either a Gaussian response GR(=< 1GHz) or maximally-flat frequency response MFFR(>1 GHz). The Gaussian response exhibits a slow roll-off at approx 1/3rd the -3dB frequency. And the maximal flat frequency response shows a flatter in-band response with sharp roll- off near the -3bB frequency. A scope with Gaussian response (GR) has a faster rise time than the one with Maximally-flat frequency response (MFFR) for the same bandwidth specification but the MFFR can measure more accurately as they donot attenuate the in-band signals. The GR attenuates the out-of-band signals and hence eliminates the high frequency components in the signal which cause aliasing.

 

Fig: Gaussian Frequency Response

 

Fig: Maximally-flat frequency Response (MFFR)

Further calculations and details are in the blog here

 

FFT functionality Tests with the R&S Signal Generator

 

The lowest frequency when the input signal is attenuated by 3dB defines the scope bandwidth and this has been tested here with the signal generator. At -3dB the signal attenuation leads to approx -30% amplitude error which can also been seen in the results. This concludes that one cannot accurately measure signals at the edge of the scope BW (1 GHz). I measured this in the following experimental setup. The tests can be found in the blog here

 

Evaluating the Rise time of the R&S RTM 3004

 

The scope bandwidth defines the rise time of the signals it can measure. Although one must understand that the scope's rise time is not the fastest edge that it can accurately measure but the fastest edge it will try to reproduce if the input signal has a thematically infinitely fast signal with rise time = 0ps. This has been tested in this blog here by inputting a pulse edge which is 16 times faster than the theoretical rise time of the RTM-3004 oscilloscope. The experimental setup can be found here

 

Noise Measurements Using R&S RTM3K Oscilloscope

Internal noise of an oscilloscope can be a limiting factor when smaller and highly sensitive signals are to be measured.  A scope with low noise or high dynamic range to look into small signals or find small changes in large signals. For each measurement the oscilloscope should be configured precisely by setting its vertical sensitivity (volts/division) and horizontal time base. This can be achieved quickly if one is aware of the noise floor of the scope. There are circuits where the system circuit noise is designed to be low. If such circuits are measured using a scope of higher internal noise the results will be distorted as there is an addition to the signal noise level from the measuring device (oscilloscope). Then one realizes that this particular scope is not a valid device for this particular measurement and one needs to chose another oscilloscope.

 

Detailed list of contents in the Noise Measurements Blog

Setup for NULL Noise Measurements

Please read further here

Measuring the oscilloscope noise floor

Please read further here

RTM- 3004 Oscilloscope Noise as a function of Sensitivity

Please read more here

Noise Comparison with Keysight Tektronix and LeCroy 1GHz Bandwidth MSOs

Please read more here

Standard Noise Generator Noisecom NC6110

Further detailed tests with the R&S RTM 3004 have been presented in the blog here Noise Measurements

 

Top Digital Protocol Evaluation

 

In this part of the blog; experiments were designed to test the different protocols and bus decoding functions offered by the RTM3004 oscilloscope. Please read the following blogs for detailed results

 

Experiments with Logic Analyzer

A quick look at the bus types which can be visualized and decoded in the RTM3004

 

Fig: Digital Protocol Evaluation

Further experiments have been done in the blog here

 

Evaluating Waveform and Pattern Generator

Here, I have done some basic measurements of the waveform generator and its capabilities. They are not in much detail but a basic overview of this feature offered by R&S RTM 3004 oscilloscope. Please read further here.

 

Power measurements  and testing Voltmeter DVM

In this blog; I have re-done the measurements with the development board TPSM84A21 Power Module DC/DC Converter and measured the ripple and power efficiency parameters with RTM 3004 oscilloscope.

 

Power measurements in the RTM 3004

The results can be found here.

Setup of the TPSM84A21 Power Module

The results can be found here.

 

Measurements with the TPSM84A21 Power Module

The results can be found here.

 

Spectrum analysis of the Output voltage

The results can be found here.

 

Transient Analysis of the Output voltage

The results can be found here.

 

Measuring with Digital Voltmeter in RTM 3004

The measurement setup and results can be found here.

 

Software Control of the Oscilloscope

Rhode & Schwarz allows full control and setting up the oscilloscope in real time via a browser window. Once the scope is setup in your work/home network it can be easily controlled and data can be saved online. It also allows access to live screen and Front Panel. More details on this is in the blog here.

 

References for Road-test Rhode & Schwarz RTM 3004 Oscilloscope

Using these references all the tests done in the Road-test can be reproduced and tested independently

 

Summary

In short the R&S RTM3004 truly stands-by all its specifications and is an 8 instruments in one device without compromising in the integrity of the a good oscilloscope (analog-wise). As I saw in many tests it performs better than as mentioned in the data-sheet. And with a number of software options to chose from elevates the R&S RTM 3004 instrument from a simple oscilloscope to a complete Measurement System. Added features of logic analyzer, spectrum analyzer fulfill the needs of an analog and digital engineer. The RTM 3004 is very well placed in the medium price range with good specifications.

          

Conclusion

In conclusion, this was quite a learning road-test for me and a challenging one to achieve. I have managed to fulfill all the promises in made in the road-test application for the RTM 3004. All the measurements and results have been published here so the methods can be used to reproduce the tests by the community.

 

Note: This road-test has officially ended

Anonymous
  • Looks like you have thought of some ideas to solve this problem. Please share with me as well when anything concrete works out for you and I will also adapt it to my device. In the mean time I am still in thinking mode with this problem.

     

    As of now, I have fixed the scope location just to be safe and covered it with a dedicated micro fiber cloth.

  • Hi!

     

    I feel the same, there is no grip strength when holding it there. For me it was minor though, since I believe I can customise it to suit my needs (I will probably put a strip of rubber in there). The enclosure on the FPC1500 looks very tough, single moulding for the entire rear shell, and seems of quite thick plastic. As I understand (and from some brief experience building a simple one) VNAs can be particularly sensitive to chassis and PCB flex, so it is good that it is all rock-solid from the outside before we even get to the inner metal chassis!

    But even with a better handle, I hope to treat it with kid gloves, and try not to impact any side of it while transporting, because of the risk of throwing things out of cal (maybe I'm being too cautious).

    If there is a front panel cover I may purchase one though, to protect the display and connectors.

  • Thank you .

     

    ah really.. I didnt know that. R&S old devices do not have that. I was kind of surprised who came up with the idea to remove the handle. Something features should be left as they are. I often felt that I will lose the grip on that big hole like thing while moving the scope. Clearly it is not a good solution if you want to move often with the scope and be on the road with it.

     

  • Nice review : )

    Very nice that stuff that is relegated to the rear side of other 'scopes, like the waveform generator output, are on the correct side with this 'scope. And very cool that there is a pattern generator! All these features look very useful.

     

    The R&S FPC1500 is of similar physical construction, although in that case the tilting feet will likely never be used, because the physical connections of RF cables are much easier when perfectly horizontal. The handle I agree on.. I'm thinking of sticking some rubber on the inside of the grip area!

  • Thanks John,

     

    Indeed I agree. My idea was to explain the WHY behind the oscilloscope and why they do what they do.

     

    And the art of analog in these amazing devices

     

    Cheers

  • Hi Sneha,

    I enjoyed your first chapter. It is always good to have some background information and comparisons.

    John

  • Thank you Rich for your efforts as well.

    You have been a great support to the developers and fast in solving the issues.

     

    My review will be on-line soon as well.

    Cheers

    SNidhi

  • Great start to the review and thank you for all your time and efforts!

     

    I'll pass your feedback on the front feet and lack of a handle.

     

    -Rich@RohdeScopes

  • Thanks everyone for your support

    I have done some awesome noise measurements which I am working on to share with everyone.

     

    Cheers

  • Very nice write up with history.

    waiting for rest of the article.