RoadTest: Tektronix MDO3054 Oscilloscope
Author: qmiteam
Creation date:
Evaluation Type: Independent Products
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?: I already own several comparable products (ie Tek DPO3000, MSO4000), so side by side comparisons are easy. Some other products I have considered (and had even had Tek come in to demo) are the MDO4000, and Agilent for a dedicated Spectrum Analyzer
What were the biggest problems encountered?: Minor firmware bugs (described below). The "demo" features of the scope require the demo board (not included with eval kit).
Detailed Review:
NOTE: I have gotten a ton of requests for info on this product, so I will start posting this review, and as I dig deeper into the product and have time to write up more, I will keep updating it. I am also in the process of making a few videos to show off some features of this scope as well. THIS REVIEW IS A WORK IN PROGRESS, I WILL BE UPDATING THIS REGULARLY, CHECK BACK FOR MORE!! (Last Update 12/10-2014 - Added some videos on 3rd party current probes and using the AFG for probe Deskewing)
Disclaimer/Full disclosure: Although I work full time managing an engineering department, and deal with test equipment all day long, *ALL* of the statements and opinions expressed here are mine personally and do not represent the views or opinions of any company I have worked for or currently work for. I do not work for nor have any affiliation with Tektronix or any manufacturers of the test equipment used for or in this review. Other than the product used in this review, I have not received any monetary or other compensation for my time or the review of this product.
Preface: First and foremost I would like to say a great big ***THANK YOU*** to both Tektronix and Element14 for selecting me to review this product. As a full time engineering manager, it is part of my job to make sure the products we turn out every day are world class and industry leading as the people that design and maintain them, and when it comes to tools and test equipment I will tolerate nothing but the absolute best available. It can be difficult to define the “best” of anything, as there are so many metrics, but for me in test equipment, one of the most important things aside from raw performance is user experience, something just operates very transparently/seamlessly with diagnostic workflow (I want to spend my time designing products, not debugging test equipment), and that is one thing that Tektronix has down to a science. Also being a piece of lab test/measurement equipment, it must be dependable and something I should never have to second guess its results (ie a 4 channel 200Mhz STM32 based oscilloscope dongle using internal ADC that hooks up to your smartphone is not a dependable piece of test equipment to me). I am very glad I am reviewing this product because the MDO scopes are specifically is a product that I have been skeptical of since its release. One thing I have learned over the years is that most manufacturers are very good at one thing, and when they try to branch into other areas, the products usually fall short. Example, Fluke makes undisputedly the world’s best digital multimeters, but when they wanted a piece of the oscilloscope market, the “scopemeter” they introduced is one of the worst oscilloscopes when compared side by side against a real oscilloscope manufacturer’s (Tektronix) handheld THS700 and missed the mark. This product (the MDO3000) is very interesting because typically the RF/Spectrum analyzer market (especially in USA) is owned by Agilent, and it will be very interesting to see how this product competes on a performance and more importantly usability level.
About me: My name is Brian Scarpati and I have been using Tektronix scopes since they had tubes in them, I started with some of their early mainframe scopes and later moved to high performance analog (Tek485) and eventually digital scopes, AFG’s and other gear. I have been working in the electronics industry for 20 years now, and currently run an electrical engineering department manufacturing equipment for medical industry. As most of you, electronics for me started (and still continues) as a hobby as well as a profession. My personal scope I used (prior to now) on my workbench at home is a DPO3034.
Summary: From what I can tell this product was target squarely against the Agilent DSOX3000. The Agilent DSOx3k on paper looks better than the old DPO3000 (as Agilent scopes often do look better on paper, and have horsepower and specs on their side). However, in the real world, in this mid-range general purpose scope price bracket, Tek scopes usually beat Agilent for me every time in terms of usability. Aside from the MDO3000 outspecing most of the Agilent (ie Tek 50Mhz AFG vs HP’s 20Mhz), at the time of this writing, Tektronix is holding “The Future of Scopes” promotion where they are including a MDO3SA option for FREE!! with purchase of any MDO3000. A free FULL BANDWIDTH 3Ghz spectrum analyzer is a mighty big carrot to put in front of any engineer (hobbyist or professional).
Unlike, some reviews, that will make you read tons and tons of data to get to the bottom line, I know your time is as valuable as mine, so I am going to start with the conclusion. If you are interested in the details that led me to this, feel free to read more.....
Conclusion: Looking at the big picture, if you look at what this scope was designed for, a general purpose, mid-range oscilloscope/instrument, it looks like Tektronix squarely hit a home run with this one.
As far as the scope goes, I’ll start by saying I did have an Agilent infiniivision unit on loan for about a month to play with about 2 years ago, and while it had plenty of horsepower, its most lacking component was the user interface. It had a very “unfinished” feel to it and felt clumsy to operate next to the Tektronix, the answer I got from the Agilent rep repeatedly was (there is a firmware update coming….). This is one place the Tek really shines. It is analogous to an “mp3 player” vs and “iPod”, they both perform the same function, and in some cases the “mp3 player” has better sound quality and bigger screens and more bits in the DAC. But when I need to navigate through 40GB of music to find what I am looking for, I’ll take the “iPod” any day!
As far as the spectrum analyzer goes, this is a true spectrum analyzer analog front end, and although there are plenty of firmware tweaks and features that can make this product better, it is definitely not a toy or gimmick, and is a solid product worthy of the Tektronix name and a very useful addition to the scope. Sure there are 20 year old used spectrum analyzers out there that have more capability and better specs, but I would hazard a guess that the 95th percentile of the people using this scope don’t have that tight of requirements on the instrument (if you do, be prepared for the price to increase about 10dB). The capability of this instrument is more than enough to get the job done. For many engineers, if it were not for this instrument, most would make do without the spectrum analyzer (ie scope FFT), or end up buying a low cost analyzer made by a lesser brand that would not live up to the specs of this unit. Since our primary application for the SA is EMI/EMC, I would say that although the device is not capable of true certified compliance measurements (Agilent’s CISPR certified receiver/analyzer is about $70k + antennas/cables, chamber/mast/turntable, etc make this very expensive to do yourself), that really wasn’t the intention. Using the MDO3000 for troubleshooting and fixing known emission issues, this device is excellent. This device also has great potential for Radiated Emissions and Conducted Emissions pre-compliance testing (a subset of a full compliance test that has slightly higher uncertainty of measurements but provides a high confidence factor before going for a compliance test).
As far as the AFG goes, I am used to using the AFG3000, and this unit is pretty close to the standalone instrument in terms of functionality. Probably the greatest feature of the Tek analyzers is ARBExpress, it is a free download application that will spare you the pain of using Mathcad just to quickly generate a waveform. The selling point of ARBexpress is ease of use, basically if you can draw it, the AFG will generate it.
If you are a hobbyist, student, or even a professional on the fence about buying a scope, now is definitely the time to buy, especially with "The Future of Scopes" event going on through end of summer 2014. This really is an awesome deal (free 3Ghz Spectrum Analyzer AND serial decode appmod!) that Tektronix is offering to slingshot this MDO technology into the marketplace. If you are a previous DPO or MSO3000 user, this scope is definitely a big upgrade. This is not like going from a MSO4000 to a MSO4000B where you might get a slightly larger record length and TPP probes, there are a LOT of changes with this iteration. About the only similarity it has to the old DPO/MSO3000 is the price. Other than that, a LOT has changed, see below....
Price: Tektronix pretty much invented this market that never existed before, so there is really no direct competition other than themselves (the only real competitor is the MDO4000 series). The only real way to do any kind of price comparison against competitive companies is to take separate pieces of equipment (ie price of an MDO3000 against Brand X digital scope + Brand Y AFG + Brand Z Spectrum Analyzer), in which case the MDO wins every time. This product’s entry level package is $3,350 (MDO3012) which is well within the reach of even most hobbyists and students, and given the upgrade paths available for this scope, it will be around for a long time.
Now on with the details......
The “Unboxing”: I know there are a lot of people out there that will make a YouTube unboxing video for a package of frosted flakes. I’ll take the high road and save you 10 minutes of your life and spare you watching me unpack a box. For those that really care, it’s a cardboard box, double corregated, engineered EPP foam packing blocks. What really matters is it arrived undamaged despite the UPS gorillas’ best efforts.
Since we received a ton of options with this evaluation unit, and it was requested that we write a single review for everything, it’s going to be a very long review. Now would be a good time to grab a snack.
What’s Included and what’s not: The evaluation unit arrived with the scope itself (MDO4054), a generic black computer IEC power cord, 4 Passive 500Mhz TekVPI Probes (TPP0500), a certificate of calibration, a CD with electronic manuals, a genuine Amphenol N to BNC RF adapter. Additional with the evaluation unit we received several options/application modules (MDO3SA,MDO3AFG,MDO3PWR,MDO3EMBD, MDO3MSO) and a Mixed Signal 16channel logic probe with the unit. Additionally there is a promo for a free MDO3DVM when you register the unit. We will independently review each of these applications later. One thing that was not included is the blue plastic protective cover that protects all the knobs and front of unit when transported or sent out for calibration, this was included on some previous scopes we purchased, luckily the DPO/MSO 3000 cover fits the MDO3000 perfectly as Tektronix did not alter the physical size or form factor of the scope from a DPO3000. If you are familiar with the DPO3000, everything will be immediately familiar with the MDO3000, its a very seamless transition. There are a lot of changes, but none of them will slow down your workflow.
Side by side with a DPO/MSO3000 (same exact form factor)
Front panel controls of MDO scope vs DPO/MSO 4channel (lots of additional controls including full keypad without cluttering it too much)
Back panel comparison of the DPO/MSO3000. The only thing I was sad to see go is the 12V probe power, as I used it to power my P5200 High Voltage differential probes for 3phase power measurements and IGBT Vgs voltages. But I am probably in the 0.1% of people that actually used it. At some point I'll have to replace them with the new age TekVPI probes, until them I'll use a wall wart to power them. Those with sharp eyes will notice that there are electronics located dangerously close to the Kensington lock port on the new MDO, so be careful with 3rd party locks should you need to use it. Given the choice I would definitely prefer the AFG over a 12V power supply 
.
Where it’s made: Most of Tektronix manufacturing for these series of scopes is currently in China. When I first found out about this I was kind of sad, and a little concerned as I have never second guessed the quality of products out of Beaverton, OR for the 20 years I have been using them. I would say every iteration is a give and take, every year, the performance and features go up dramatically, but the overall quality of materials used to build the equipment goes down a little to keep selling prices attractive. Case in point, my Analog Tektronix 485 350Mhz oscilloscope was built in 1972 in Beaverton, and is still running today over 40 years later!!! Although Tek built those scopes to last forever, and yes it does still work, it is long obsolete. Even if today’s stuff was built half as good, and lasts half as long, for me, it is more than enough as the half life of most electronics today (including test equipment) is a lot less than what it used to be. Over the past 7 years I have been using Tektronix products made in China every day, I can confidently say the quality is very good and products do stand up to daily use.
Upgradability: This is one place that Tektronix has come a long way with in recent years. Back in the days of old, the scope you bought with whatever OPT codes it was ordered with was what you had until the day it was traded in. Tek changed a lot of this with their original “AppMod” system starting in their TDS scopes which allowed purchase of many software features as needed after a scope was purchased. However these earlier appmods (up until the DPO4000B series) were limited to easy to add software unlocks (ie Serial protocol decoding). More advanced feature upgrades such as converting a DPO scope to MSO, or converting a 100Mhz base model to 500Mhz previously required hardware upgrades (board swap) and were usually priced to be cost prohibitive/unattractive vs buying a new scope. That has all changed with the latest generation of scopes with previously unheard of upgradability. The concept of bandwidth upgradability started with the DPO/MSO4000B, and this scope has pretty much everything can be upgraded via two methods. The first method is by using an AppMod Module and transfer the license from the module to the oscilloscope. There are two classes of upgrade modules, one is referred to as an “OPTION” and the other as an “APPLICATION”. Options are installed to the box permanently and unlock various hardware features (ie 16ch Logic analyzer, AFG enable, 3Ghz Spectrum Analyzer, etc) while APPLICATIONS can be uninstalled and transferred to other scopes (ie Serial protocol decoding, power analysis, etc). The second method of upgrading is by using a unlock code that can be purchased online and typed into the scope to enable the feature. The difference is the code is keyed to the serial number of the scope, so it will only work on one scope, whereas application modules are portable and can be shared across multiple scopes.
Since the introduction of the MDO series, Tektronix has also introduced a new means of upgrading that does not involve obtaining physical hardware (appmod modules), and licenses can be purchased online and unlock codes issued to enable the functionality. The advantage of this is that you can enable options and applications on very short notice (online purchase, no waiting for shipping). The disadvantage is that the purchased option/unlock code is keyed to the oscilloscope serial number and is not portable between multiple instruments. Tektronix is offering a promotion for a "free DVM Option" when you register the oscilloscope, so I figured this would be a good opportunity to demonstrate the functionality.
This is the initial powerup splash screen before unit is registered encouraging you to register for "free dvm" option
As soon as you register the product online at myTek.com, you are immediately presented with an unlock code for the DVM
On the config page, under about, it shows installed OPTIONS, as shown DVM is not enabled
To install option first select "Manage Modules & Options", then install option, you will be prompted for an unlock code as shown on right
Once a valid unlock code is entered, you will be instructed to power cycle the instrument, and that's all there is to it, the option is installed. Options will remain installed no matter what memory wipe functions are performed (ie secure wipe, firmware upgrades, etc).
One important note is that the AppMod modules have changed with this scope even though they appear similar. The DPO/MSO3000 Application modules are *NOT* compatible with this scope, so if you are upgrading from a DPO3000/MSO3000, you will need to replace the application modules. i.e. a DPO3EMBD is functionally identical to a MDO3EMBD, but the modules are not interchangeable between the DPO/MSO AND MDO scopes. If you have any questions about this, feel free to email me.
This is what Happens if you try to use your DPO/MSO 3000 purchased appmods in an MDO3000
DVM Option – Free with Registration - The MDO3000 DVM option does not add significant value to the scope my opinion, if it wasn't free, I probably would have complained more. Although tek marketing dept will disagree with me, other than a larger font size, it doesn’t appear to do anything that the “Add measurement” function does not. This is probably because I am spoiled and have used a REAL integrated DMM in a Tektronix oscilloscope. It's old enough, that most people don't remember it. It was in the old THS700 series. It was a true dmm that had banana jack FLOATING ISOLATED inputs, and did ohms, diode check, audible continuity, ACV, DCV, datalogging, etc. It was a really cool feature that was lost after this series. The THS700 was Tek's last attempt at a "integrated scope" that had functions other than an oscilloscope before introduction of the MDO series. The main problem with the MDO3000's DMM is that since its input is an analog scope channel, it has all the same limitations of the oscilloscope probe with regard to common mode voltage input, grounding, etc. In addition it ties of a valuable analog channel for a basic function (may be an issue on a 2Ch scope). It cannot replace a DVM, unless you put a P5200 high voltage differential probe on the input, and even then it only does voltage. No resistance or other measurements are supported. An integrated true DMM with isolated differential inputs considering Tek's relationship with Fluke/Danaher now, this feature should be easier and better than ever. If this was a true hardware DMM (ie AC Current/DC Current, True RMS AC Voltage to 1000V CATIII, DC Voltage to 1000V CATIII, Ohms - minimum 10MEG, continunity, etc), it would add real value to this instrument as it would be nice to not need to replace DVM batteries all the time or spare the valuable real estate on the workbench for a bench mount DMM. I really wish they invested just a little more hardware in this feature as it would be a really nice addition to have a dedicated set of floating banana jacks and not tie up an analog channel for DMM, and would be one of those things that aside from some specialty handheld instruments, that no one else in the mid-range oscilloscope marketplace currently offers.
Above is what the "DVM option" does on the MDO3000. It gives you a large box docked to the top of the screen with a large font that shows the AC or DC voltage on one of the channels. Tek claims to have dedicated hardware making these measurements (aside from scope ADC), but it doesn't really do anything you couldn't do with the "add measurement" functions. Due to limitations of the probes with respect to common mode voltages and earth grounding of the scope (don't try measuring 120Vac in your mains with it without a differential HV probe), at the end of the day it really can't replace a portable DMM.
User Interface – This is probably where Tektronix really stands apart from the rest by a wide margin. If I could use one word to describe this unit I would say “Polished.” So often I come across products that I would describe as “wow, that’s really cool, but it needs a little more work.” The scope side of this unit gets better with every iteration, there are some cool new features (ie FastACQ, backlit keys) not on previous generation units. The screen is noticeably higher resolution. The overall look and feel has changed from the blue/white color scheme to a black dark color scheme.
After extensively polling the audience, it seems that everyone is mostly curious about and interested in the spectrum analyzer. So I will spend a lot of time in this review talking about the spectrum analyzer section and go into some oscilloscope features later.
Spectrum Analyzer –
Available Bandwidth: The standard spectrum analyzer bandwidth starts at 9khz and ends at whatever your oscilloscopes bandwidth is (ie a MDO3012 gets a 100Mhz spectrum analyzer standard and a MDO3102 gets a 1Ghz analyzer). However there is an interesting exception to the rule. If you want a full featured spectrum analyzer with 3Ghz bandwidth, and on a 100Mhz scope, it is possible by adding the MDO3SA Option upgrade. This does not have to be purchased with scope and can be unlocked at any time. During the current Future of Scopes sales event, Tektronix is including this with purchase of ANY MDO3000 (even the entry level 100Mhz version) for FREE!! This upgrade is normally priced at $2500!
True MDO Functionality: Since Tektronix invented this market, there are no quite “official” rules as to what can be called an MDO. When the MDO4000 first hit the market, Tektronix explained “mixed domain” as being able to view both the time domain (oscilloscope) and frequency domain (spectrum analyzer) side by side for a given signal, or “time correlated measurements between RF and analog/digitial channels.” The MDO3000 does *NOT* have this capability, I would prefer to think of the MDO3000 as a “Multiple Domain Oscilloscope” as opposed to a “Mixed domain oscilloscope.” (wow, what a great marketing phrase!). The MDO3000 has the capability to act as an oscilloscope or a spectrum analyzer, but not both at the same time, you must switch back and forth using the “RF” button on the front panel of the instrument.
This is an example of Mixed domain functionality as Tek originally introduced it, the MDO3000 *CANNOT* do this, only the MDO4000 has this capability
Spectrum Analyzer Probes:
The MDO3000 includes a female N receptacle on the front panel for RF input, its in the same place as previous scopes had the EXT Trigger input. It also includes a high quality Amphenol N to BNC adapter to make connections. Other than that no probes are included. Since the applications for a spectrum analyzer are highly varied, there really is no "standard" probe. The oscilloscope probes are unsuitable as they do not cover the bandwidth of input for the spectrum analyzer, hence the need for a dedicated RF input. For most of my applications, the main reason I want a spectrum analyzer is EMI/EMC compliance measurements and troubleshooting, and I will stick to that for the purposes of this review. For conducted emissions, great care must be taken not to damage the RF front end input as the threshold of damage on an MDO3000 is 1/10 that of many spectrum analyzers (most people who work with high frequency oscilloscopes and spectrum analyzers regularly are accustomed to dealing with and careful using Low impedance inputs, but the typically midrange oscilloscope audience is not). Most spectrum analyzers (including the MDO4000) have a maximum input power of 1W, the MDO3000 max power in is 100mW, if unsure of input signal strength, use an attenuator to avoid damaging the RF input especially for direct coupled measurements. For any type of radiated emissions measurement, you will need some type of antenna. If doing pre-compliance measurements (you are trying to get a pretty good idea the total radiated emissions of your product and at what frequencies you need to worry about), the two most common types are a dual antenna (biconical for low frequencies <200mhz, and log periodic for higher frequencies), or a high quality broadband (BiconiLog) single antenna for all measurements typically measured in an open area 10m from a device under test. For up close and personal EMI troubleshooting work and probing around a device or PCB, or to pick up any kind of radiated RF energy (ie a car alarm keyfob) you will want a near (close) field antenna that is tuned near the frequency you are trying to measure. A near field RF can be as simple as a loop of bare copper wire on the end of a BNC cable (and these do work very well for relative measurements), or as fancy as a calibrated near field probe. Tektronix currently recommends and distributes a close field antennna manufactured by BeeHive electronics. Personally my favorite is the HP/Agilent/Cokeva 11940C near field probes with a good preamplifier (more on the importance of that later).
Beehive Electronics Near Field Probes (Left) HP/Agilent/Cokeva Near Field Probes (right)
Using the Spectrum Analyzer for EMI/EMC Radiated Emissions Troubleshooting (a practical approach):
This is a true story and real world application for the MDO3000, not some salesman's demo PCB, or manufacturer cleverly designed demo board to show off their test equipment operating under ideal circumstances at exactly the frequency and amplitude they want.
Sooner or later, it happens to the best of us. We design a product and lay out a PCB using "proper design practices", passes all in house verification and validation testing, product is essentially ready to ship, and when it goes out to a EMI testing lab, the dreaded fail result comes back. Now at the 11th hour, the problem must be located and fixed, and FAST! Since this problem was located at the calibration lab, half the work has already been done been done. If we were doing a full precompliance test, we would have to make calibrated measurements and determine which frequencies needed further investigation. In this case the calibration lab determined the frequency that was the problem. This product was excessively radiating above the limits at 360.018Mhz. This was confirmed by me on an Agilent 8591EM Quasi Peak EMC analyzer. Attached is a screen shot showing the peak tuned in at 360.018Mhz measuring 33.22dBuV. After cable loss and antenna factor corrections we were marginally over the limit.
Agilent 8591EM QUASI-Peak measurement of Radiated Emissions
The most important piece of test equipment for doing this is a spectrum analyzer and a set of near field RF probes. The first step in this case is to set the center frequency to 360Mhz and a fairly narrow span (ie 5Mhz), and then probe around the product looking for the highest amplitude to localize the source of the problem (ie Enclosure leakage, cable radiating, enclosure radiating = Very bad). In the case above, it was a cable radiating a AC coupled signal due to a PCB layout issue. In the end this was mitigated by added some RF chokes (and cost) to the affected cables/product. Then once we achieved compliance certifcation with the RF chokes, we took the PCB out of the product and hooked it up on the bench to locate the exact component and means the signal was getting coupled for design improvement to eliminate the chokes in the future. For the purposes of this review, since the board contains intellectual property and I cannot show the actual electronics, I put it in a fiberglass bag that will allow the signals to pass through. I wanted to illustrate the importance of input sensitivity and DANL (noise floor) and the need for a preamp with the MDO3000 when making RF measurements with the spectrum analyzer with sources that are not intentionally radiating (usually relatively small signal levels vs noise floor). The DANL and noise floor is better on the MDO4000, but this can be easily overcome with the use of a broadband preamp. For the first setup example, I will take this exact PCB that marginally failed EMI compliance, and connect a near field probe directly to the MDO3000 to measure the radiated emissions. See the setup pictures and screen captures below.
Near Field probe connected directly to MDO3000 RF input, the device under test is inside the gray fiberglass bag.
Below is the measured waveform (click to enlarge):
This is the waveform captured from the Device under test with a RF Close field probe connected directly to the RF input of the MDO3000 (click to enlarge). If you look very carefully, you can see the peaks, but it is very hard to discern improvements and make accurate measurements since they are nearly lost in the noise floor.
The way to fix these measurement issues is to improve the signal to noise ratio which will effectively lower the noise floor of the instrument (MDO3000 in this case). This is done by adding a broadband preamplifier to the RF input of the MDO3000. Tektronix manufacturers one for the MDO4000 which is supposedly compatible with the MDO3000 as well specifically for this purpose. The part number of theirs is a TPA-N-PRE, sells for around $2700 and offers 12dB of gain. For this review, since the demo MDO unit did not include a tektronix preamp, I used a HP/Agilent 8447F OPT H64 broadband preamplifier that I have which provides approx 25dB of gain (these come up really inexpensively on eBay all the time, and work very well). See below for the setup (click to enlarge):
This is how a preamp is connected to effectively lower the noise floor of the MDO3000 by improving signal to noise ratio, the near field probe is connected to the input of the preamplifier, and the output of the preamp is connected to the MDO3000 RF Input.
Nothing else has changed in the device under test (no design/circuit changes) other than the addition of the pre-amplifier. Below is the MDO3000 waveform with the preamp connected (click to enlarge):
MDO3000 spectrum analyzer capture with 25db broadband preamp connected
Above you can clearly see the peak that caused the failure of the radiated emissions compliance test. Once we have this peak maximized through positioning of the near field antenna relative to the circuit, it is very easy to see effects of making circuit changes and improvement yield. The important thing to know about EMI troubleshooting and repair vs precompliance testing is that when working in dB, is that near field change is approximately equal to far field changes. So, if you know that you are failing compliance by 3dBuV, if you can make a improvement in the near field of >3dBuV, you can have a fairly high degree of confidence that the device will pass a compliance test. For EMI troubleshooing/repair, it is NOT necessary to know antenna factors, cable factors, etc since you are making relative measurements, not calibrated absolute measurements (as you would in a precompliance test). From here, we were able to easily identify which corrective changes to the circuit would yield the highest benefit to EMI radiated emissions using the MDO3000.
I could write an entire appnote dedicated to the subject, but for the purposes of EMI/EMC troubleshooting, with the addition of a preamp the MDO3000 is a very capable instrument. For full pre-compliance testing the MDO4000 has a few extra beneficial features.
AFG Functionality, Current Probes, and Deskewing (real world practical applications of an MDO3000):
One useful feature of the AFG is that it can be used as a deskew pulse generator. Tektronix sells a device specially for this (TEK-DPG), but most engineers have never even heard of probe deskewing, let alone would purchase a specialized piece of equipment to do it. In a nutshell it is used when the phase difference between probes/channels on an oscilloscope matters, and it is especially important when using different type of probes (ie current probes, active probes, and passive probes all displayed side by side on the same oscilloscope). I made two videos on demonstrating two concepts on an MDO3000. The first video shows how a really cheap (or 3rd party) current probe can be used on an MDO3000 to easily (not having a calculator by your side trying to figure out the current to voltage conversion constantly) to directly measure an display current on an oscilloscope. We all know that the fancy tektronix TekVPI probes auto configure the scope via 1-wire bus to directly display current and auto deskew, but it is not as well known you can do the same thing with a calibrated, or even a cheap homemade current probe. The first video shows how to configure a older tektronix (non-TekVPI or non-Tekprobe) or 3rd party current probe to display current on the MDO3000. The second video illustrates the concept of Probe deskewing and how it can be performed using the internal AFG in the MDO3000 as a deskew pulse generator.
LOTS MORE TO COME!!! While waiting for more of this review, how about reading some of the questions I have gotten below, maybe email me a few of your own.
I have gotten a ton of questions about this unit, if you have any you would like answered, email them to me, and I'll do my best to answer them.
Top Questions I have gotten from coworkers/colleagues about this unit:
Answer: This is fundamentally impossible on the current architecture because of the design of the Spectrum analyzer. Unlike conventional spectrum analyzers that “sweep” the entire spectrum and the tracking generator operates in parallel, the MDO series use a hardware implemented I-Q capture and real time FFT on the results to produce the frequency domain waveform.
Answer: This is also fundamentally impossible based on the current MDO architecture due to shared hardware. The MDO3000 functionality essentially aggregates all 4 high speed analog ADC’s used on the oscilloscope which are 2.5GS/s each into a single 10GS/s RF capture channel to capture frequency domain when in RF Mode, during this time the ADC’s are “busy” and cannot capture waveforms. The MDO4000 has 8 hi speed ADC’s to do both at the same time (4 are used for the RF capture, and the other 4 are used for time domain/oscilloscope measurements). This is the one of the biggest differences between the MDO3000 and MDO4000 in hardware.
Answer: The biggest difference is target audience. The MDO4000 is targeted at people who would buy an oscilloscope and a dedicated spectrum analyzer, the MDO3000 is targeted at engineers who would not typically be able to justify the expense and bench real estate for a dedicated spectrum analyzer, and usually end up using the FFT on their scope. On the MDO3000, The analog/RF input stage is a step down from the MDO4000 in terms of phase noise and Displayed Average Noise Level (approx. 10db/Hz worse than an MDO4000 for phase noise with 100khz offset), but is plenty good enough for its intended audience (people who would not otherwise buy a dedicated spectrum analyzer). One be very careful note is the MAX input power (threshold at which you will damage the RF input attenuator first stage). The MDO4000 (like most standalone spectrum analyzers has a 1W (30dBm) max input, while the MDO3000 has a 0.1W (20dBm) max input. If you are unsure about what you have coming in, you must use an RF attenuator on the input of the MDO3000. Most MDO3000 target audience users are not used to working with a low impedance input on an oscilloscope, and care needs to be taken to protect the RF input. People that use high speed oscilloscopes >1.5Ghz are used to LowZ inputs already. Also the MDO3000 displays either time domain (oscilloscope) or frequency domain (spectrum analyzer) measurements, but not both at the same time, so time/frequency correlated measurements are not possible on an MDO3000 (this is a hardware limitation, not fixable with firmware). Another difference is the lack of real time PC interface for the spectrum analyzer, the MDO4000 has a LiveLink stream output for use with SignalVu (this can be used for enhanced high bandwidth capture), while the MDO3000 does not have this capability.
Answer: As far as probes, see my section I wrote in this review on probes, the unit includes passive probes for the oscilloscope that support the full bandwidth on the OSCILLOSCOPE side. For the spectrum analyzer/RF side, the only thing included in a BNC to N adapter, it does not include any probes as the applications vary widely and there is no “standard” type probe for a spectrum analyzer. For me, on the RF input side, my preferred probe is an antenna with 50ohm coax cable (my favorite tool are near/close field antennas which are small and handheld like an oscilloscope probe and pick up RF signals and are very directional, they can be as simple as a BNC cable with a loop of bare copper wire on the end or as fancy as my HP/Cokeva 11940A, currently Beehive electronics is making inexpensive RF probes in the $95 range that Tektronix is recommending).. As far as advantages/practicality goes, it ultimately depends on your application. I made a YouTube video showing how this can be used for EMI/EMC troubleshooting radiated emissions in a design which is a very handy tool if you are designing products that may be sold commercially and must meet regulatory requirements. You can find a link in this review under section for Spectrum Analyzer. The Capture bandwidth and resolution is the main tradeoff that must be balanced to not “miss” important data in your capture. Like an oscilloscope, the spectrum analyzer has a fixed number of points it can display on the screen at any given time. The capture bandwidth is the maximum frequency range you can sweep across the display at any given time (referred to in spectrum analyzer world as SPAN in the case of the mdo3000 its 3Ghz), then there is Resolution Bandwidth (RBW). The RBW can be set to anything you want, and that is how far apart each sample will be taken across the SPAN. If you set your RBW to 1Mhz for a 3Ghz span, and you have 3 peaks that are 50khz apart, they will appear on the display as a single peak. You will be able to resolve more detail with a smaller RBW, but a capture will take much longer. Once RBW is set low enough, the limiting factor of how much data you can resolve is limited to the number of data points on the display (that 10million record length number ONLY applies to the oscilloscope, the spectrum analyzer is around 1000 points). If you need very high capture resolution, this limitation can be overcome on an MDO3000 by slicing the spectrum into smaller regions (SPANs) and capturing them individually (ie capture 1000pts between 1-10Mhz, then another 1000pts between 10-20Mhz, etc, etc.
Suggestion Box - These are mostly targeted at Tektronix for firmware improvements/tweaks to make this awesome piece of test gear even BETTER!!!:
I hope you enjoyed this review. I wanted to take some time to really get to know the product before posting this, so I did take the time I was allotted before posting this to learn everything I could about these scopes. Since this is my first review, any feedback is appreciated. As I said previously, this review is in Blog format, and will be updated as time permits, so if you feel I missed anything, please let me know, and I'll add it.
