Electrical measurement equipment is an expensive category for many educational institutions. While a single lab workspace is simple and relatively inexpensive to set up with a full set of tools, problems arise when a course calls for a large number of identical workbenches. For many schools, the cost alone will present a major issue, but for even more, the space required for such a setup is simply too large, providing major logistical obstacles.
Digilent attempted to solve most of these issues with their Analog Discovery Studio – a portable prototyping platform based on their popular Analog Discovery 2 USB oscilloscope. In fact, the measurement capabilities of both devices are identical. Where the Analog Discovery Studio shines, though, is in the academia-oriented additions to the Analog Discovery 2 make the Studio a superior device in terms of convenience.
We’d like to take some time here and thank Digilent for sending in a review unit of the Analog Discovery Studio free of charge. On the other hand, this is not a sponsored review and all of the opinions here are our own.
At $599 ($649 for a kit that also includes oscilloscope probes and BNC hook-up cables for the waveform generator), the Studio is competitively priced, providing a wide variety of instruments for much less than their traditional benchtop or rackmount counterparts. The main instruments is offers are a dual-channel oscilloscope, a dual-channel waveform generator, as well as a 16-channel logic analyser. There’s also a pair of variable power supplies along with three fixed ones, as well as instruments that share some of the the inputs/circuitry of others, like the network and impedance analysers which combine the oscilloscope and waveform generator instruments or the voltmeter which uses the oscilloscope inputs.The system is simple to connect and get started with, utilising a USB cable for computer communication, and a supplied barrel-jack power adapter for powering the instruments. The two cables are all the system needs, reducing workspace clutter by a considerable amount compared to a more traditional setup.
One of the major new features is the removable breadboard (Digilent calls it the “Breadboard Canvas”), which offers handy power supply connections when docked to the system. The breadboard canvas also offers three LEDs, two push-buttons and two slider switches. These are not replaceable, and honestly, we find them a bit gimmicky, but we do see some appeal of having the most basic components right there on the board, helping beginners jumpstart their first circuits.
Now, moving onto the instruments themselves, we’re starting with the oscilloscope. The instrument offers two interfaces, MTE cables and BNC probes. The MTE inputs are differential, so the negative lead can be connected to a non-ground net. The BNC inputs are grounded, albeit offering a much higher bandwidth (30MHz, compared to the 9MHz when using MTE cables). Both methods require the circuit tested to share a common ground with the Studio. This all adds up to a very capable oscilloscope, backed up by user-friendly and powerful software. Our main complaint in this field is the fact that virtually no other key instrument except the waveform generator and the logic analyser can be used at the same time as the oscilloscope. We would have liked to see the option to “split” the two oscilloscope channels between instruments, because when using, for example, the spectrum analyser, channel two often sits around being unused. Another, although smaller, gripe that we have is the relatively low sampling rate of only a 100 Ms/s. While, in theory, this should be just enough for even a 50 MHz scope (let alone the nominal 9 MHz bandwidth), it should be kept in mind that interpolation is going to play a key factor in proper signal display, and that high-speed non-sinusoidal will not be displayed correctly. For the price, we can understand the sampling rate limitation, but we would like to see Digilent implement a 200 Ms/s, or even a 500 Ms/s oscilloscope in future revisions of the system.
Going on to the waveform generator, it’s a simple 8 MHz generator with two channels, which should be plenty for most use cases. The built in waveforms include sine, square, triangle, ramp, noise and pulse waves. It’s more than enough for most practical applications, and some advanced features such as AM and FM modulation make it a versatile tool.
The power supplies are also reasonably specced, including three fixed-voltage supplies (at 3.3 V, 5 V and ±12 V) and two variable supplies (one positive and one negative) that go from 1 V to 5 V (-1 V to -5 V, respectively). All supplies are current limited at 700 mA, which is more than enough for most projects.
The logic analyser is on par with most of those found in mixed signal oscilloscopes, and the powerful protocol analysis tools are rarely seen elsewhere, especially at this price point. The decoding, due to being processed by PC hardware is extremely accurate and happens in real-time, an issue most oscilloscopes without dedicated decoding hardware. Another instrument that should be mentioned alongside the logic analyser is the pattern generator, allowing for complex digital patterns to be produced on all 16 digital I/O channels. This is done at the same 100 Ms/s rate that the oscilloscope, logic analyser, and the waveform generator operate at. We find this a very useful addition, as many beginner labs don’t have a way of easily getting synchronised digital signals without the use of an MCU, which many students may find intimidating.
The digital I/O tool is also tied in the same instrument set, providing GPIO with on-screen visualisation. This is very useful, as it reduces the amount of components and the breadboard clutter in projects requiring many indicator LEDs or using 7-segment displays without drivers. They can also serve as input, allowing the project to be controlled from digital buttons displayed in WaveForms.
The voltmeter function is somewhat of a hit-and-miss for us. While it provides useful readouts for voltage, it’s not a true multimeter replacement as it doesn’t offer any current capabilities, and also prevents every other tool using the analog inputs from being used. Essentially a glorified “measurements” menu from the oscilloscope, we don’t find much use in it, but it might be handy to have because it does offer true-RMS measurement. (Although, we strongly believe that a separate DMM is a required addition to this package, and any decent multimeter should and will also have true-RMS capabilities, further lowering the usefulness of the voltmeter tool.)Finally, the spectrum, network and impedance analysers are what truly set the Studio apart from almost all other USB instruments. Using its inputs and outputs, it can perform real, sine-sweep frequency response graphing of various useful parameters. These are quite impressive for the cost, beating all software-based analysers nowadays featured in modern oscilloscopes.
In our own testing we found a few interesting facts about this system. Using the oscilloscope, we’ve realised that the actual usable bandwidth limit is at around 15 MHz, even with BNC cables. The relatively low sample rate really kicks in around that point and the loss of detail in displayed waveforms is shockingly obvious. A 25 MHz square is hard to distinguish from a 25 MHz sine (which in turn looks like a 25 MHz triangle wave), but, this isn’t really the purpose of the Analog Discovery Studio. Where it truly shines is up to the 5 MHz mark, where all signals are very clean and precise, and comparable to the performance of a low-end standalone desktop scope.
We’ve also noticed two curious ports on the board that we haven’t seen referenced elsewhere – a USB A port to the side, and a headphone jack right next to it. The headphone jack seems to be connected to the analog output channels and seems to be used for audio visualisation of generated waveforms. This is a nifty feature, but we aren’t exactly sure what it’s for – chiptunes? Additionally, the USB A port can power additional boards, like microcontroller development kits, but can also be used to transfer data to them, something we found very useful. This allowed for just one port to be used on the computer to power and program an entire project featuring two Arduinos and the logic analyser. This is important when using the system with modern laptops, which feature only a handful of ports.
What are our final thoughts on the Analog Discovery Studio? It’s a powerful tool that offers so much in such a little space. The Analog Discovery 2, which the Studio is based on is already a community favourite, providing many hobbyists and students with tools they wouldn’t have access to normally. The breadboard provided is very high-quality, and the entire build of the device feels sturdy and well-made. The port selection has been thought about and provides some excellent features that make prototyping that much easier. While no instrument on-board is truly exceptional at its own task, they are more than capable of their intended use – academic training and lab work, and especially in the field of audio circuits and low-speed 8-bit and 16-bit microcontroller circuits, a device like this provides aspiring students and tinkerers with all the right tools at a very affordable price. It also allows schools to provide an almost fully-featured solution for lab workstations, giving each student access to a powerful set of tools, instead of forcing multiple people to share one spot.
For this very reason, the prospect of this board immensely excites us, and we see such systems playing a major role in education in the future. While the Analog Discovery Studio is built upon a great, reliable foundation, we can’t feel but a little let down with the lacklustre specifications of some of the features. Still, the Studio is way more than the sum of its parts, and as a whole it offers an innovative, low-cost, minuscule electronics lab suitable for even the more demanding projects a student can do. As such, we can wholeheartedly recommend schools consider this as an alternative to traditional desktop lab equipment, taking a step towards modern, powerful measurement instruments.