|SeeedStudio DSO Quad: An Early Preview|
It is with great excitement that I bring to you what is possibly the very first review of the new DSO Quad by Seeed Studio. This week I received from SeeedStudio and engineering sample of the product and I have had now a few days to play with the scope. It’s still early days for the product and SeeedStudio have a short bug list till to resolve before the product will be on general sale, but today I can give you a taster of what will I think be another exciting product for the electronics hobbyist and field engineers.
So here are my impressions…
For those that have not seen my review on the DSO Nano, a little introduction to the SeeedStudio portable oscilloscopes… The original Nano was announced at the tail end of 2009 and introduced a small light and most importantly very affordable Digital Storage Oscilloscope to the market. Its affordability and size made it an instant success though it was not without it’s limitations. A relatively slow sample rate and it being a single channel device was the penalty to pay for its low cost and size. It has since had a revision to V2 and several excellent improvements via firmware updates but essentially its specifications have changed little in this time.
Enter the DSO Quad. I have been following the development of this product for some time… SeeedStudio have relied heavily on the input of the Nano owning community to help them develop this product. Through their Wish pages and forums, they have collected ideas for the product, some that made the cut and others that didn’t. Open source hardware has many advantages, developing products in the public eye allows you to gain feedback from potential customers throughout your product development.
One design feature that did not make it the final product was the wearable case design that I reported on in my blog section a while back. I thought that this was a novel idea, but hey ho. Thinking it through I am not sure anyway that i would have worn the scope when using it anyway.
So lets see what SeeedStudio has come up with in the DSO quad. Lets begin with some specifications:
The SeeedStudio DSO Quad introduces some considerable improvements over the Nano they released earlier. The obvious difference is the Quads four channels compared to the Nano’s single. Look more closely though and another big difference is on the available bandwidth to the analogue channels A and B. The Nano boasted a fairly measly 1mhz Max but the quad is using faster silicon inside this gives it up to 36MSa/S This offers a decent sample rate for the price, though I have to say that I have been getting by quite happily with the lower sample rate of the Nano for some time. I suppose it depends on the use you are putting a scope to in the end.
Lets have a look at the DSO Quad then and see what we get. The design of the unit is compact. The LCD screen which looks like its 400 x 240 pixels and 2.5 by 1.5in size takes centre stage of the device. Arranged around the outside edges of the Quad are the controls and the input/outputs.
Unlike it’s predecessor the DSO Quad has a slide on/off battery compartment cover, though with a USB charged LiPo battery I am hopeful that I wont need to replace it. I did notice that under the battery there are six trim pots, I assume that they are used to calibrate the device, I left well alone!
It is worth mentioning that although the Nano (Ver. 1 or 2) and the Quad are similar sizes, the Quad is a heavier device. This gives it the impression of being a more solid product. Build quality on my sample is more than good enough for the price point that SeeedStudio are aiming for. They claim to have improved on the mould quality since my sample was manufactured to improve further panel fit.
Input wise SeeedStudio have opted for compact push fit coaxial connectors for attaching your probes to the Oscilloscope. I have not seen these connectors before. I was supplied a reasonably sturdy 1x probe and a set of somewhat less sturdy clip style probes as well. SeeedStudio also supplied a sample of the connector they have used. Great for me as I have a set of probes going spare that I will convert for use with the Quad. It will be interesting to see that SeeedStudio supplies with the eventual production model. Hopefully something a little sturdier for the test clips, though the more substantial probe is fine (limited as 1x). Now when SeeedStudio release this oscilloscope on general sale there is a question to be asked. Will they supply four probes or just two? Because of the rarer connectors I think that they will need to have a good supply of probes to at least offer as a cost option. Not sure that everyone will be interested in the low sample rate logic only channels C and D.
Thoughtfully SeeedStudio have again supplied a signal generator. It outputs through another one of those push in coaxial connector on the side of the DSO Quad There is provision in the current firmware to create square, triangle, saw and sine waves from the signal generator in a variety of frequencies. In this early sample though only the square wave functions correctly. This is on the bug list and should be resolved before general production.
The SeeedStudio DSO Quad is capable of pausing the waveform and storing it. In the previous Nano,storage came in the form of a micro SD card slot in the side of the device. This was an additional purchase to the customer. The card option offered some flexibility in that you could remove it to read via a card reader. With the Quad SeeedStudio has been more generous in one sense. My sample came with a 2MB of memory internally fitted. That means no additional card to purchase, but some may mourn the ability to pull the card to read data direct. Instead all waveforms can be read by plugging in the DSO Quad to a PC via its USB connector. To be honest its not something that I would consider an issue. 2MB seems more than enough storage space for my purposes even using the Quads ability to store to .BMP format (as well as DAT and CSV).
So how does it drive?
This is the million dollar question isn’t it. You can see my video review at the bottom of this article .
First thing to take into consideration is that I did not have the benefit of a user manual (they have not written one yet!). But if you do decide to purchase the SeeedStudio DSO Quad, I would encourage you to have a good read up on the instructions. With the single channel scopes, usage was a one handed simple affair that anyone who had a rough understanding of how to use an oscilloscope could master in a minute. The cost of all the extra features this scope has comes in the complexity of the menus. On the top of the DSO Quad Oscilloscope there are four buttons, play/pause, S (select), M (Memory) F (File) and two left/right flicky switches for negotiating menus and changing options. It took me a while to work out how the menus were operated. once I got to grips with it it got easier though. I am also using of course an early version of the firmware.
As with the Nano, SeeedStudio wants the firmware to be open to experiment. No surprise that BenF, a talented programmer who dramatically improved the Nano firmware has also been supplied with one of the engineering samples. Expect to see some improvement in this field as the device matures. As it stands, the firmware is 95% functional even in this early sample.
The screen on the DSO quad is reasonably easy to read, it’s certainly bright and vivid enough though it is small. Viewing angles are reasonable though perhaps not as diverse as you will find on a modern smartphone say. I haven’t found this holds me back any when using it. I do have a SeeedStudio stand that I purchased recently for my Nanos. For the paltry sum that SeeedStudio charge for this I would recommend buying one alongside your DSO Quad. (It also holds my HTC HD2 rather well!) Being able to angle your quad when it is say on a bench will avoid frustration.
The channels are arranged across the top of the display and information is colour coded per channel throughout the user interface. You navigate between channels, trigger options, signal output and other functions with the right-hand-most flicky switch. The S button then takes you in to sub options and the other flicky lets you cycle through the possible values. It feels like a little refinement could be done (remember I am testing an early firmware version, it will undoubtedly be better again in production)
Down the right hand side of the user interface is a set of measurements such as Voltage measurements (Peak to Peak, RMS, Max, Min, Vdc, Vbt etc). The DSO Quad is capable of giving a lot of measurements, so much so that not all can be displayed at the same time for all channels. instead you can choose twelve measurements of your choice at a time.
My only slight concern with the user interface is there is a lot going on and its a small display. It would be nice to have the option to simplify the display and when required display less items. If your Quad is at the back of a workbench you are going to need better eyesight than I am blessed with to read those figures. The waveform however is pretty clear at most times and options are there to alter time and measurement scales.
The SeeedStudio DSO Quad is like it’s predecessor an exciting product. Pricing has not been finalised for the Quad, but those happy to purchase a Beta test unit (available on pre-order at the time of writing) are paying $159 so expect the final price to be in that price bracket. Like the Nano then the Quad is going to offer a lot of bang for your buck. Oscilloscopes (especially digital ones) are generally pricey items that hobbyists buy second hand if at all. The Nano put a basic digital device on the bench of many people who could not afford or justify the cost of a “Scope”. Obviously it costs a bit more, (probably double) but look at how much more you get in the Quad. More Channels, lots more samples per second, more signals generated.
Even with the rough edge or two that you expect to see on an engineering sample I am bowled over at the quality that SeeedStudio are delivering with the DSO Quad at the price point they are aiming for. I would say that this oscilloscope is going to be one of those rare bargains that will leave smiles on the faces of hobbyists and professional users!
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