29 Oct 2015
Oscilloscopes: from elite equipment to consumer device
Reimer Grootjans of LabNation looks at the way in which some oscilloscopes are becoming consumer devices and within the reach of the maker community.
It’s hard to recall a hi-tech product which is as mandatory in a multitude of technical areas as an oscilloscope.
While they used to be reserved for highly trained personnel, recently they’ve been finding their way to a much broader audience.
But at the same time, it’s hard to recall a hi-tech product which has evolved so little over the past half century. This article zooms in on the remarkable adventure the oscilloscope has undertaken starting from hi-tech device to becoming a consumer device.
Maker space is booming
Where computer enthusiasts typically were confined to local gatherings, things have evolved dramatically over the past years. The advent of high volume and very low-cost computers like Arduino and Raspberry Pi has significantly lowered the barrier for anyone interested in joining the DIY community in their aspirations to become a maker.
Whether you’ve created LED decoration for your Christmas tree or a new full-blown 3D printer, it has never been easier to show off your projects on different forums and invite people to work on your code through GitHub. On various crowdfunding platforms, a sprawl of extension boards to the Arduino and Raspberry Pi are being presented, allowing for a limitless number of ideas being converted into prototypes.
Figure 1: Low-cost development boards lower the barrier between software and electronics
While these makers typically have a background in software, what they’re essentially doing is bridging the gap towards electronics. With all tools needed to develop and debug software being entirely free, the tools to debug electronic circuits come at a much higher cost, even though they are equally essential.
This allows for perfectly verified software driving the electronics, but you’ll need a tool to figure out why a LED is not behaving according to your code, or why a sensor is not responding to the presumed calls from your Arduino. A simple multimeter to measure a fixed voltage can already shed some light into the darkness. But for most cases, you will want to see how this voltage evolves over time, and for this you need an oscilloscope.
A large portion of the maker community might even be unaware of their need for an oscilloscope. As one of my fellow makerspace frequenters put it: “you need a scope to debug your circuit the same way you need a breakpoint to debug your code”. And he couldn’t be more correct: where a breakpoint allows you to stop the time and check all parameter values in your program, a scope allows to stop the time and check the behaviour of your voltages during a certain timespan. Having multiple channels, a scope can help you in finding not only what is going wrong, but also what is causing your signals to do so.
Smaller makes cheaper
Typically there are 2 obstacles standing between a maker and an oscilloscope. One of them is cost. While it is true that the word oscilloscope itself sounds expensive, oscilloscope manufacturers have made an effort the past 5 years to design products geared specifically towards this emerging market of makers in need of an oscilloscope. In the end, they managed to present devices perfectly capable of debugging any maker project, at a cost of around $200.
This was achieved by keeping only the electronics and assembling them inside a USB box. Using the display of a PC and its input devices, there was no more need to put these bulky parts on the oscilloscope itself. This resulted in a much smaller, and consequently, cheaper device.
The other barrier is the interface typical to an oscilloscope. The multitude of knobs and buttons can be discouraging to people not yet familiar with electronic measurement devices. As can be seen in Figure 2, the interface which originates from the 60s has almost not evolved at all over the past half century and is becoming a real barrier towards mass adoption.
Figure 2: The interface of an oscilloscope has not evolved in a half century
Even more so, some manufacturers of modern USB scopes use dated man machine interfaces on the PC. This requires the user to rotate knobs by mouse and select grid settings through drop-down menus - this can decrease the user experience compared to the traditional interface.
Figure 3: Various interfaces of PC-based oscilloscopes
Some new devices are breaking with this traditional interface, e.g. by using touch functionality present on many modern laptops and tablets. This enables the user to make the required control settings in a much more intuitive way. While this interface might require some getting used to for experienced engineers, its intuitive approach makes it more appealing to the maker community and the new tablet-raised generation of engineers.
Scoping on the go
But the realm of oscilloscopes is expanding even further. The completed transition from analogue to digital scopes has resulted in the introduction of many portable oscilloscopes, either USB-based as described earlier or stand-alone handhelds (see Figure 4). This allows circuits and devices to be analyzed and repaired far outside the reach of a lab, ideal for field technicians and service engineers.
Figure 4: Tablet-based oscilloscopes now entering the mobile market
With their software running on tablets and smartphones, any engineer carrying a smart device can connect to their oscilloscope on the spot, leveraging the processing performance and high-resolution displays of their smartphone or tablet.
Things to watch out for
In case you find yourself wondering whether an oscilloscope is the right thing for you, make sure you run through the list below. It describes the main specifications of an oscilloscope, and gives an indication of how much you’ll need of everything.
Input: make sure the voltages you intend to look at are within the min and max boundaries specified. Keep in mind that a min of -20V and max of 20V don’t imply you can visualize a 40V signal, so if you want to visualize signals of a large amplitude make you sure look for the peak-to-peak specification. Also, make sure the scope supports AC coupling, which is needed in case you want to look at small spikes on top of larger signals. The impedance should be at least 1MOhm with low capacitance (<20pF), as otherwise you will change the signal you’re looking at by putting the probe tip on the signal!
Sample rate: defines how many times per second the voltage is converted into a value, so how many datapoints your graph will consist of. As a rule of thumb, make sure your samplerate is at least 10x faster than the signal you want to look at. So if you want to look at a 10MHz wave, you need at least 100MS per second.
Bandwidth: This defines how close the signal on the display is compared to the real signal. In the theoretic case where your signal would transition infinitely fast from 0V to 5V, the trace on your scope will still show some rise time which can take many samples. As a rule of thumb, make sure the bandwidth of the scope is at least 3x the frequency of the signal you want to measure, 5x is preferred.
Triggering capabilities: triggering allows you to position an event/transition of a signal on a fixed position on your display. Make sure your scope allows setting this trigger position freely in both directions. If only the date after the trigger can be displayed you will never know what happened before the trigger, which is typically the most interesting part. Be wary of 48MHz USB oscilloscopes, as this indicates the data is simply captured and sent straight over the USB bus, indicating no buffering possibilities for the trigger are present.
Logic analyzer: Some oscilloscopes also combine a digital/logical analyzer, which can be a great tool for any maker as this offers the ability to visualize the behavior of various digital signals simultaneously. Keep in mind these analyzers can only tell you whether the signal is high or low, not voltages.
On-board memory: Some oscilloscopes offer built-in RAM, which can be great as it allows you to freeze an event on the display, and afterwards zoom in into very fine detail to figure out exactly what happened when.
This new breed of oscilloscopes has a huge amount to offer and will appeal to the maker community and many others. Reduced cost while maintaining the functionality needed for many of the more basic measurements enables these scopes to carve out a new niche in the marketplace that many will take up.
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About the author
Riemer earned a M.Sc. Eng in Electronical Engineering at the Vrije Universiteit Brussel in 2005. After going for a PhD on real-time 3D cameras, he co-founded a company designing 3D cameras now distributed by several major California-based companies. As such, he had the rare opportunity to lead a hardware patent from prototype to mass-production, while at the same time experiencing a start-up grow to 100+ employees. Throughout 2013 he designed and validated the first prototypes of the SmartScope, which KickStarted LabNation in February 2014 by 1459 backers, with more than 2000 devices produced and shipped out before the end of the same year. Riemer currently acts as CTO for LabNation and as consultant for a start-up designing smart glasses, where he shares his knowledge on how to transform a concept into a product on the shelf. Next to hardware, Riemer has a passion for writing C# and graphical applications. He authored 3 books on XNA with positive reviews. He received the Microsoft MVP award in 2007, 2008, 2009 and 2010.
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