Fullscreen HTML5Med Res (??MB)HTML4

Tektronix MDO3054 “Six-in-One” Mixed Domain Oscilloscope Just what you’ve always wanted... a four-channel digital storage oscilloscope, logic analyser, protocol analyser, spectrum analyser and arbitrary waveform generator with digital voltmeter and frequency counter in a single package! Y ou may recall our review of the Tektronix MDO4104-3 Mixed Domain Oscilloscope in the November 2011 issue. It was (and still is) a very clever device, capable of ‘freezing time’ like a DSO but operating in both the time and frequency domains, ie, alongside the waveforms from the four analog and sixteen digital channels it could also display a time-correlated RF spectral analysis. We were very impressed with this capability but the price of the MDO4000-series scopes puts them out of reach for many. The just-released MDO3000-series also combines a scope and spectrum analyser (plus some other functions) in a more affordable package. This unit is part of the recent trend to try to integrate as many extra functions into a scope as possible. We’ve seen mixed signal scopes with waveform generators and DVMs before but by adding the spectrum analyser in as well, the MDO3000 is the current “king of the mountain”. Common features The overall instrument is fairly compact given its screen size and the number of knobs and buttons – it measures 417 x 204 x 148mm (not including carrying handle) and weighs 88  Silicon Chip 4.2kg. It’s somewhat wider than the most compact scopes but that’s due to the large 23cm (9”) display which has excellent colour and contrast and a reasonably good viewing angle too. While the big handle makes it taller, it certainly makes it very easy to carry, too. Overall, it does not seem unwieldy. There are soft buttons on both the bottom and right edges of the screen, which simplifies the operation of the menu system somewhat, along with the two general purpose knobs (rather than one as is typical). As you can see from the photograph, there are plenty of specific-function knobs and buttons too. While it does take up more physical space, we prefer having separate vertical controls for each channel as it makes operation simpler. Overall, the control layout on this scope is above average and we quickly got used to the location of most buttons as they are positioned logically. When both multi-purpose knobs (“a” and “b”) are active, on-screen icons show which one does what and you quickly get used to looking for those icons. The zoom/pan knob is pretty easy to operate too, with the pan function being spring-loaded and the zoom ‘jog wheel’ within it. The spring-loaded pan wheel gives a scroll speed is proportional to how much force you’re applying and allows for quick panning. You will notice that there are some extra buttons on the right side compared to a regular scope and these are the numeric keypad and mode buttons for the spectrum analyser, which means its controls are mostly separate to the rest of the unit. The spectrum analyser shares some knobs and the soft buttons with the scope but we think they could have used more of them; for example, the pan and zoom controls do nothing in RF mode whereas they could have been used to adjust the span. While the numeric keypad is primarily used for the spectrum analyser, you can use it for entering numbers in other situations such as when setting the signal frequency and amplitude for the arbitrary waveform generator. This is certainly quicker and more accurate than twiddling knobs. You can also plug in a USB keyboard instead to make it even easier (and that also simplifies typing labels and file names). Capabilities The spectrum analyser section operates similarly to stand-alone spectrum analysers that we have used and its performance is good, on par with a decent stand-alone unit. Essentially, it’s a separate instrument that shares the siliconchip.com.au Review by Nicholas Vinen The large screen and generous number of ‘soft buttons’, plus the well-organised control layout make driving this unit quite straightforward. d i s p l a y, c on t ro l s and power supply with the rest of the device. It does take up a lot less space than having two separate devices and there is also the advantage of only having to learn one control interface. The spectrum analyser input is an N-connector. If you’re at all serious about using the spectrum analyser you will need to pay for the 3GHz bandwidth option; otherwise, it is limited to the same bandwidth as the scope inputs, ie, 100MHz-1GHz. But even 1GHz may not be enough as many users these days will be looking at WiFi, Bluetooth, Zigbee etc, all above 2GHz. By the way, all software-controlled options are enabled for the first 30 days of operation. That includes the 3GHz spectrum analyser bandwidth. It also includes the logic analyser sesiliconchip.com.au rial bus decoders. After that time, you will need to pay for the options if you want to continue using them. The spectrum analyser is FFTbased and has all the features you would expect such as a very wide capture bandwidth of 3GHz which means you can look at the whole spectrum in a single display (see Fig.1). We’ve set the resolution bandwidth to be much finer than the default for this span (at 30kHz rather than 3MHz) as this lowers the noise floor and improves peak discrimination at the expense of display update rate. Fig.1 also demonstrates the automatic markers and averaging features. The unit can also make some basic measurements on the RF signal: channel power, adjacent channel power ratio and occupied bandwidth. Note though that unlike its bigger MDO4000-series cousin, the scope and spectrum analyser functions are essentially separate and can only be used one at a time. So if you want to be able to see the scope inputs and spectrum analysis on the same screen or be able to freeze the instrument and then do spectral analyses at different points in time, you will have to spring for the higher end unit. Accessories As you would expect, the scope is supplied with two or four passive probes that have equal or greater bandwidth than the scope itself. The probes supplied with our demo unit were 500MHz 10:1 types, although they didn’t actually indicate the division ratio on the probes anywhere we could see (which is somewhat unusual). These are high-quality probes and the hand-held portion is quite small; we like that, standard probes seem pretty bulky in comparison with modern circuitry and can really get in the way when you are trying to measure several parameters at once on a small, tightly-packed PCB. The cables are May 2014  89 Fig.1: we connected a 2m length of wire to the RF input and ran a spectral analysis over the full span of 10kHz to 3GHz. Automatic cursors are enabled, giving peak details at the top of the screen. The low resolution bandwidth gives a relatively low noise floor but does slow down screen updates with such a large span. very flexible which also helps when probing cramped PCBs. Interestingly, while the probe inputs are BNC sockets, the probes are actually held in place by a spring-loaded clip integrated into the boxy section. This has a button which you hold down to release the probe and it can then be pulled free. Once you get used to it, this makes connecting and disconnecting probes quite convenient. If you purchase a mixed-signal scope (ie, a model with the logic analyser enabled) then logic probes are also supplied. The analyser has 16 channels which is good; some scopes only have eight and while that is plenty in most circumstances, if you need to monitor two SPI buses plus a few digital I/Os, it won’t be enough. All versions are supplied with an IEC mains cord and accessory pouch which can be used to hold the probes and so on. They also come with a small manual and a CD with the rest of the documentation. The quality of the documentation is above-average and it includes clear explanations of what the various options and modes do. Other functions As DSOs go this one actually has a lot of features, both in terms of hard- ware and software. Hardware-wise, it comes standard with 10Mpoints memory per channel which is great. It supports active probes and can autodetect compatible probes when they are connected. It also has Ethernet and VGA interfaces by default. What about HDMI, you might ask? VGA is rapidly becoming obsolete. This seems to be an industry-wide issue; presumably scopes with HDMI outputs will appear soon but for the moment, if you want to connect an external monitor or projector to a scope, you’re stuck with VGA. The DVM feature is free after completing a registration form. This gives more accurate voltage measurement for low-frequency signals; the reading has four digits rather than the three you get in measurement mode but for AC (RMS) measurements, it is only good for signals up to about 10kHz. It also incorporates a 100/150MHz frequency counter (depending on scope bandwidth). While this is handy to have, it doesn’t have the same precision as a good multimeter and lacks the other features such as current measurement, capacitance, resistance etc. One day those functions will probably be integrated too but for now you’ll still need a multimeter or two. The arbitrary function generator option is quite handy and can produce a variety of signals up to 50MHz. It operates at 250 megasamples per second and can generate arbitrary waveforms with up to 128k points. The output is at the back which is a little inconvenient but you can leave a BNC cable attached semi-permanently. There is only one channel. For mixed-signal models, the logic analyser input is conveniently located at the front, near the other probe connections and has a relatively small ribbon that splits out into two logic heads. It’s supplied with the usual IC clips. Software features Fig.2: the ‘temperature’ display in FastAcq mode which is used to enable maximum waveform update rate. This is used to detect runt pulses, check outliers, determine jitter and so on. The colour indicates ‘hit density’ with the hotter (more red) colours indicating more commonly sampled values for that point in the waveform. 90  Silicon Chip We won’t describe all the usual DSO features which of course are present, such as cursors, waveform measurements, statistics, averaging mode, high-resolution acquisition, zoom and pan, waveform mathematics (“math”), reference waveforms and so on. It has all the modes you’d expect and more. “Math” mode includes an FFT function – we guess this is still useful since the spectrum analyser has a separate input. siliconchip.com.au One interesting feature of this scope is that it can display statistical histograms of time or voltage data. For example, it can plot a graph showing the distribution of jitter in a pulse train. You can also take measurements from the histogram such as mean, standard deviation, 1st, 2nd, 3rd, Sigma values (percent of values within 1, 2 or 3 standard deviations) and so on. Like the MDO4000-series, the MDO3000-series has a particularly powerful ‘math’ mode where you can not only do basic calculations such as adding or multiplying two traces, you can actually enter a mathematical formula based on the time domain values of one or more traces to produce a new trace which is then displayed on the screen. This can include functions such as integration and differentiation and is a very powerful feature – but you will probably need to plug in a USB keyboard so that entering formulas is not too time consuming. The “Wave Inspector” zoom/pan control group also includes buttons to search for and mark events in the recorded waveform, using similar logic to that which is used for triggering the scope; in fact there is an option to use the trigger settings to mark events. You can then skip between these markers and you can place manual markers which can be handy if you are moving around a lot in a long record and want to remember your place. The triggering system is quite powerful and includes sequential triggers (ie, edge on one channel then another), triggering after multiple edges, depending on pulse-width, on runt pulses, a logic combination, on setup/hold timing violation, depending on rise/fall time, on video frames (including HD) and on logic bus packet contents, assuming you have that bus decoder option installed. There are a couple of very nice aspects to the measurement system on this scope. One, for measurements which involve analysing data over a time period such as RMS, you can select that time period, eg, over a single cycle, over all the cycles displayed on the screen or all the cycles recorded in memory. You can also have it use the area between the cursors to do the calculation. You also have the option to turn on ‘indicators’ for a given measurement and if selected, this displays a set of ausiliconchip.com.au Fig.3: here we have turned on a lot of different features, with the digital voltmeter/ frequency counter at top, zoom window below, then the graticule, status display, two measurements plus the menus. Obviously you would not normally turn these features all on at once as it leaves little room for the traces! tomatic cursors which show how the measurement has been calculated. For example, if enabled with a frequency measurement, two dotted cursors appear which show the two points in the waveform used to determine the signal period. We especially like the fact that you can select which measurement to display the indicators for and that you can turn it off if you don’t need it, to de-clutter the display. While all the features mentioned above come standard, there are some that come at extra cost (but as explained above, with a free 30-day trial). This includes limit and mask testing (MDO3LMT option) and power analysis (MDO3PWR option) including power quality, switching loss and harmonics. The logic analyser is also an optional extra and on top of that, there are various serial bus decoder modules you can purchase, including audio, CAN/LIN, RS-232/422/485 and I2C/ SPI. There is also an option for USB 2.0 triggering and analysis for low-speed and full-speed devices (ie, up to 12Mbit). With this option and a scope with 1GHz bandwidth, you can also ...Continued on page 102 Fig.4: luckily it only take a few button presses to de-clutter the display; this shows the maximum amount of screen space available for the graticule, with just the static display at bottom (which can be turned off but just leaves an empty space). The large screen space comes in handy for viewing multiple waveforms in details. May 2014  91 Review: Tektronix MDO3054 Scope . . . continued from p91 decode and view hi-speed USB packets (but you can’t trigger on a content match). Performance Boot-up time is around 20 seconds which is par for the course with a scope having this many features. The next thing we looked at was analog noise performance which is good. It’s quoted as <150μV +6% of one division for bandwidths up to 200MHz or + 8% of one division up to 1GHz. In practice, the display is quite clean, especially in ‘High Resolution’ mode. While the interface is easy to use, its responsiveness leaves a little to be desired. It can feel sluggish at times but is pretty tardy in spectrum analysis mode with a high ratio of span to resolution bandwidth. Of course, you would expect the display update rate to be very slow as this involves a lot of calculations but we don’t see why it has to stop responding to button presses during this process. And while the waveform acquisition rate is far from poor, it isn’t the best we’ve seen either. To get the full specified rate of 280,000 acquisitions per second you need to use “FastAcq” mode which changes the way waveforms are displayed (see Fig.2). Otherwise, the limit is 50,000 acquisitions per second. We like that you can display statistics for each measurement (min/max/ average/etc, see Fig.3) but unfortunately when you turn statistics off, you don’t get that screen space back. I then remade the loop with the exact wire recommended in the article. This was worse as I was no longer able to create an event of any sort with bars or golf clubs. Any help would be appreciated. (M. M., via email). • It certainly does sound as if the loop is the problem. But it’s not easy to zero in on the exact nature of the problem itself. If your multimeter shows that the loop conductors themselves are cor102  Silicon Chip The rear panel carries the connectors for the arbitrary waveform generator output, a trigger output, Ethernet, VGA and two USB ports. One USB port is for connection to a PC while the other is for a printer. The measurements are displayed in a vertical list rather than horizontally so with several on-screen, that uses up quite a bit of valuable real estate, despite the large display. As a result of this and the large number of features in general, it’s quite easy to clutter it up with so much information that you can barely see the traces (again, see Fig.3). But at least you can press “Menu off” a few times and turn off the zoom and some other functions and get the screen real estate back (Fig.4). Conclusion Tektronix have managed to combine a mixed-signal oscilloscope, spectrum analyser and arbitrary waveform generator in one package without really compromising any of those functions. All of these features work well rectly wired as a continuous loop, with no segments reversed in polarity and no open joints, this would leave the outside screening braid. If this has been accidentally connected to ground at both ends (rather than only at one end), it would act as a shorted turn rather than a Faraday shield and would then prevent the loop from working. Try disconnecting the loop shield connection at the righthand end terminal and then use your multimeter although it is a bit of a stretch to call it six instruments in one, as the protocol analyser functions are a pretty standard feature of the logic analyser and the DVM only provides a small increase in utility over the existing scope measurements. Overall though, as you can gather from the above, they haven’t skimped on features. While we would like the interface to be a bit more responsive, that doesn’t really get in the way of its ability to view signals which is what this instrument is all about. If you want a stand-alone scope with a proper spectrum analyser, Tektronix is currently the only game in town. For pricing, for more information or to order one of these units, contact TekMark Australia on 1300 811 355, e-mail enquiries<at>tekmarkgroup.com SC or visit www.tekmark.com.au to see if there is still a connection between the two. If there is, this will show that there is still a connection, eg, at the other end of the loop cable. Monitor for LiPo batteries I am the proud owner of a new LiPo 100Ah battery. I intended to use two of these in my new caravan as house batteries, charged by solar, an AC battery siliconchip.com.au