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. The majority of the units compared also offered mixed-signal oscilloscope (MSO) features either as an option or included in their base configuration. A few key criteria were compared in a table, colour-coded to “group” attributes into different levels of performance.

 

Disclaimer: Such a comparison cannot take into account all possible specifications and only considers “on-paper” specifications as claimed by the manufacturer. Furthermore, the comparison only focuses on a limited number of key parameters and is provided in good faith. No warranties are provided on this data, as errors and omissions could be present. I cannot be held liable for any damages howsoever caused. Users are encouraged to do their own research prior to purchasing - at this level, it’s likely that prospective purchasers may have a particular application in mind and it may be advisable to contact a Field Applications Engineer to discuss their requirements.

 

Comparing the Contenders

The full table is provided as a PDF attachment to this post. For viewing convenience, it has also been “sliced” into more digestible pieces for review.

 

We begin by comparing Rohde & Schwarz’s offerings in this class, which include the RTM3004 (the RoadTest device), RTA4004, RTE1104 and RTO2014 in ascending order of price.

Table comparing oscilloscope specifications

The RTM3004 represents Rohde & Schwarz’s lowest-priced offering in the 1Ghz 4-channel category, but despite this, it seems to offer quite a competitive specification nearly matching the more-expensive RTA4004. The key stand-out features include 10-bit resolution on input channels, input sensitivity of 0.5mV/div, >50dB of channel-to-channel isolation, a 1280x800 10.1” capacitive touch screen and optional 16 digital channels supporting up to 400Mhz which distinguish the RTM3004 (and most other R&S oscilloscopes more generally speaking) from the competition.

 

The maximum sample rate is quite acceptable at 5GSa/s, as is the DC gain accuracy of 1.5 to 3%. It’s also nice to see the inbuilt applications of a digital voltmeter, trigger counter, mask testing and annotation.

 

The default memory depth of 40Mpts in non-segmented mode and a waveform update rate of 64,000 per second are a little lacking by comparison. This can be vastly improved through the RTM-K15 option which pushes the memory up to 400Mpts with fast segmentation and a waveform update rate up to 700,000 per second, although at additional cost. Various serial protocol decode options are available, although notably fewer than with the RTE1104 or RTO2014. Further to this, spectrum analyser, arbitrary waveform generator and power analysis options are also available.

 

By comparison, the RTA4004 mainly offers a better DC Gain Accuracy specification and a larger memory with segmentation by default but doesn’t otherwise differ significantly from the RTM3004. The RTE1104 and RTO2014 are 8-bit by default but can offer higher 16-bit resolution with an optional add-on, although their memory depth is somewhat limited by default. Where they excel is in the number of protocol decode options, especially with the RTO2014 which also has automated compliance test options available. The RTO2014 also has even deeper memory options, a larger 12.1” screen and better channel-to-channel isolation. That being said, the RTO2014 is noticeably more expensive and the RTE1104 has an inferior screen when it comes to resolution.

 

In all, it seems the RTM3004 is a good value-for-money option within the Rohde & Schwarz line-up. Let’s see how this compares with the competition.

 

Table comparing oscilloscope specifications

 

The first step is to compare it with the offerings from Tektronix and Keysight Technologies, two very recognisable names in the test equipment space.

 

The first thing to realise is that the RTM3004 trounces the others almost across the board - when it comes to ADC resolution, the RTM3004 offers 10 bits versus the 8 bits of the competition, which should mean four-times more vertical resolution. It also has the finer vertical scale of 0.5mV to make use of it. The 40Mpts default memory of the RTM3004 also well surpasses the competition – Keysight offering just 4Mpts and Tektronix offering 10Mpts and 20Mpts. The channel-to-channel isolation of anywhere from about >30dB for Tektronix to >40dB for Keysight is also an area where the RTM3004 is noticeably ahead, which should mean cleaner signals when dealing with multi-channel acquisitions. Even the screens of the competition don’t match the RTM3004 for clarity, offering anywhere between 800x480 to 1024x768 pixels, compared to the 1280x800 offered by the RTM3004. In fact, on this point, the differences are so vast that I’ve even made a separate comparison towards the end about screens.

 

Keysight’s instruments do offer segmenting by default and a higher waveform update rate of 1,000,000 waveforms/second which isn’t matched by the RTM3004 even with the added-cost RTM-K15 option. But between a choice of 400Mpts versus 4Mpts, I’d rather take the deeper memory even if that meant reducing the update rate to 700,000 waveforms/second. Tektronix’s MDO4104C with MDO4MSO claims to have a digital frequency up to 500Mhz, which is a little more than the 400Mhz offered by the RTM3004.

 

The RTM3004 falls behind when it comes to offering decode support for FlexRay, Manchester, NRZ, SENT, USB PD and USB 2.0. The options list for the Keysight products also seem to offer some more versatility, e.g. offline analysis and NFC testing.

 

As a result, I can conclude that the RTM3004 compares very favourably – the price seems quite competitive with the lower-end options from the two while absolutely trouncing them in the majority of important specifications on paper. When compared with the more expensive options from the other two, the RTM3004 still looks rather competitive, even though the RTM3004’s options list is a little shorter.

 

Table comparing oscilloscope specifications

 

Moving over to another rather major competitor, this time we compare the RTM3004 with Teledyne LeCroy’s offerings – there are a lot of them. Generally speaking, the Teledyne LeCroy WaveSurfer offerings are all 8-bit with either 1mV or 2mV per division input sensitivity, offering either 10Mpts to 32Mpts of memory – on these parameters, the RTM3004 easily excels.

 

While LeCroy’s lowest-cost WaveSufer 3104z may appeal on price, its specifications seem rather compromised with just 4GSa/s interleaved for 1Ghz bandwidth which is a little low for comfort, a DC gain accuracy of 2.5%, a digital probe with just 125Mhz capability and a screen with 1024x600 resolution. When it comes to options, it is pretty sparse.

 

This leaves the WaveSurfer 510 and 10/10M as lower cost contenders. From what I’ve been able to ascertain, the 10/10M is nearly being phased out as the 510 offers better specs with the same price. The WaveSurfer 510 is actually quite interesting as it offers 10GSa/s sampling rate, a waveform update rate of 1,000,000 waveforms/second, 18-or-36 digital channels (depending on option) with a maximum frequency of 250/500Mhz (depending on channels) and extensive protocol decoding options available. The screen offers the same resolution at a larger 12.1” size. The DC gain accuracy of 1% may be a little optimistic, as it is a “typical” value. In these areas, the WaveSufer 510 is preferable to the RTM3004.

By comparison, the 104MXs-B doesn’t appear competitive, as it has some of the limitations of the older WaveSufer 10/10M and a higher list price to boot.

 

As a result, I’d have to say that the WaveSufer 510 comes the closest to challenging the RTM3004. It has a slightly lower RRP with a healthier list of options, especially when it comes to serial decoding, and offers a higher sample rate, higher waveform update rate, more optional digital channels with higher frequency and larger screen with equal resolution. However, the RTM3004 offers 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. As a result, it’s a bit of a draw – depending on whether you have a preference for analog or digital.

 

Table comparing oscilloscope specifications

 

LeCroy also offer their HDO series, which offer higher vertical resolution of 12-bits, 10GSa/s sample rates and segmented memory with upgrades. The HDO4104A and HDO6104A both offer more flexibility with protocol decodes, better DC gain accuracy and have a larger screen with equal resolution. However, even with their memory upgrades available for the HDO, the RTM3004 offers a more total memory after being upgraded. The RTM3004 offers better channel-to-channel isolation across the full bandwidth and has a higher working digital probe frequency. Keeping in mind that the HDO series is significantly more expensive than the RTM3004, Rohde & Schwarz’s offering is still very attractive.

 

Last, but not least, I look at Rigol’s offering. Unfortunately, Rigol has no MSO offering, thus their “best effort” oscilloscope is being compared – the DS6104. In practically all points except price, sample rate, (default) memory and waveform update rate, it is notably inferior to the RTM3004. If you’re after an MSO, then that’s too bad.

 

Screens: The Window into the Scope

While performing the comparison, I noted that there was a significant discrepancy in both size and resolution of the screens of the candidate units. Seeing as the screen is primary form of interface for someone using the unit interactively, having a good screen is of great importance. As a result, I compiled a table of sizes and resolutions and computed the total number of pixels, screen area and pixels-per-inch (PPI) density of the screen to better understand the relative sizes of screen and their sharpness.

 

For added fun, I threw in the screen specifications for my “entry-level” Rigol DS1102E two-channel 100Mhz oscilloscope that I’ve been using from time to time for a laugh. Note that the values for this screen (5.7” 320x240) are not included in the comparison in the commentary below.

Table comparing oscilloscope screen specifications

 

By looking at the comparison, it’s clear that the 1280x800 resolution is the highest amongst the competitors, offering the highest resolution images. Some of the competitors with 800x480 screens offer just 37.5% of the pixels! With a screen size of 10.1” on the RTM3004, it’s not the largest screen of the set, but it offers the sharpest display at ~150ppi which is equivalent to a number of tablet displays. For reference, an average computer monitor has about 94-108ppi. The screen size of 10.1” offers around 30.5% more area than the smallest of the crop (8.5”).

 

While a 12.1” 1280x800 screen may have been better, offering more area to use the controls and an equal resolution, considering the positioning of the RTM3004 and its competitors, a 10.1” screen is still very much better than expected.

 

Conclusion

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, etc. As a result, it pays to look at how the instrument performs as a system as well.