Justblairs Audio and Electronic's Pages

For those starting out in electronics as a hobby there are some tools that are required for the job.  To begin with, a soldering iron, some screw drivers, perhaps tweezers and of course a multi-meter are probably what you would consider essential. 

After a while though, you are going to be looking for more.  Amongst the other goodies out there to help you on your way are oscilloscopes.  In the past, advice on forums has always tended more towards purchasing a second hand scope.  These tend to be had for around £100 on places like E-bay and most certainly will be a few years old if available at this sort of price.  Well that is changing and I was excited yesterday to get my hands on a “Scope” that may just re-write the forum advice.  Meet the Nano DSO from Seed Studio…

When I saw the Nano on sale I jumped at the opportunity to own a MP3 sized digital storage scope.  Up to now I have been using an old Farnell 20Mhz scope that has seen frankly more glorious times.  It’s not that it doesn’t work, but that for the home user the analogue scopes take up a lot of space.  The CRT tubes in them weigh a lot as well! 

The Seeed Studio DSO Nano I ordered was one of their “beta test” models.  Seeed Studio released 30 oscilloscopes for sale at the lower price of $69.  The eventual price for this digital oscilloscope will be a paltry $89.  Even at the higher price you can buy a brand new one for the sort of money that would buy you a 20 year old analogue oscilloscope on E-bay! 

Here are the specs according to Seeed Studio:

Specifications

Ok looking at the specifications we can see one or two limitations.  The most obvious being the sample rate of the device.  1Mhz is ok, but does not compete with analogue scopes that are readily available up to 100Mhz via E-bay.  But lets think this through, what are you most likely to be needing an oscilloscope for?

For the hobbyist, an oscilloscope is most likely to be used for testing equipment to see how well it works.  At 1Mhz high frequency noise is not going to be measureable, but most electronic signals will be easily visible on an oscilloscope of this resolution.  If like me you are interested in Audio devices, the range of audible frequencies lies between 20hz to 20khz.  This digital oscilloscope is certainly going to be of use for this.

Other limitations of the oscilloscope are that it is a single channel device.  Oscilloscopes generally are available with at least two channels allowing you to compare signals before and after amplification or processing (A handy thing to be able to do).  However the Seeed Studio DSO Nano is a digital storage scope.  It is possible in a limited fashion to compare a live signal to a previously stored trace.

Lets look next to what you get for your money.

Package Contents

The DSO Nano arrived from China in a non-descript brown cardboard box from China.  I for one prefer to see mail order goods arrive without all the costly packaging glitz that you see on store shelves, its costly, unnecessary and destined for landfill. 

Contained in the package were

1 x DSO Nano

2 x Black Anodised back plate

1 x pre-cut double sided tape (to attach the back plate)

1 x 3.7v Battery

1 x Set of probes.

Seeed Studio supply the DSO Nano part assembled.  The battery was not fitted to the device presumably to preserve it during storage.  Considering the intended recipients of such a device, it is not unreasonable to assume fitting it should be within the skill levels of the owner.

Looking at the build quality of the device I was reasonably impressed.  Seeed Studio have taken a creative step in their design here.  The casework for the DSO Nano was obviously originally designed to house an MP3 Player.  To obtain their ultra low price point for the digital oscilloscope they have utilised an existing piece of casework avoiding the expensive tooling fees that a new product normally requires.

The casework that Seeed Studio have selected is attractively styled.  Build quality is reasonable in my sample, though one or two things are not perfect. 

Firstly the on off switch for the DSO Nano is a sliding micro-switch.  As designed the case work clearly should have included a small plastic switch cover to finish the design.  On the sample I received switching the oscilloscope on and off is not possible without the aid of something sharp.  The sliding switch is recessed in a narrow slot.  I suspect this is by omission rather than design.  Bear in mind my sample is one of the early betas.

The other slight gripe I have with the build quality is that the internals of the DSO Nano are not entirely securely fitted.  Shaking the casework I can hear and feel movement inside.  A little foam judiciously placed in the device would presumably eliminate this to give a more solid feel to the product.  This is not a major issue and certainly does not interfere with the usage of the oscilloscope.

On one side of the casework is found a mini USB socket, micro SD card slot and mini-jack. 

The mini-jack is used to attach the supplied probes.  The specifications for the device boast that it can use either 1x probes or 10x probes.  What is supplied with the DSO Nano is a set of 1x probes.  Construction of these probes is pretty cheap to be honest.  I suspect that these will prove to be quite fragile.  The probes use retracting tweezers to attach to your test point in the circuit.  This is pretty practical for attaching to the leg of a through hole component but is more limited when it comes to testing surface mount designs. 

I would think that you are going to want to adapt some more durable probes for use with the Nano.  I would imagine that this will be easy enough as a stereo plug is a cheap and easy to find item.  I may even attempt to make a mini-jack to BNC adaptor to allow me to use my existing probes.

The back plate for the  DSO Nano is a very stylishly finished piece of black anodised aluminium.  Sporting a screen printed Seeed studio emblem and product information this finishes the design off beautifully.  The fit of the back plate was snug.

Setup

First thing to do to get up and running with your DSO Nano is to fit the battery.  The battery incidentally is a rechargeable device which uses the 5v voltage from your computers USB port to supply its juice.  The DSO Nano can also run from the USB power if you forget to charge it and need it in a hurry.

A fine tipped soldering iron is a useful tool to have when soldering the battery to the clearly marked solder pads of the DSO Nano.  Seeed Studio had thoughtfully left a couple of globs of solder on the pads to make life easy here. It took me just a couple of seconds to solder it in.  A couple of strips of double sided tape hold the re-chargeable battery in place.

Helpfully the battery had a full charge in it when it arrived meaning that I could test the digital oscilloscope prior to fitting the back plate.  Seeed Studio supplied a second back plate, I am not sure if this is because they anticipate people ruining one during setup or that the back plate will need replacement later for cosmetic reasons.

All up and running and the unit could be switched on.  When powered up a quick splash screen tells you the model number, firmware version etc then you are launched into a the live oscilloscope display…

I found out more by accident that their is a test signal available to try out the scope.  The signal I originally believed to be of a very low amplitude, but if you touch the positive terminal of the probe to the metal string holder, a much greater test signal is available.  Most likely because this is a beta test device, documentation is currently a little limited for the device.  I did not find mention of this test signal in the documentation.

Using the DSO Nano

Controls

I would guess that it took me in total around two hours in total to become totally at ease with all of the functions of the Digital storage oscilloscope, although in less than an hour of playing (Manuals are for wimps!) to master the main controls.  The display is very clear and easy to read. Although no adjustment is available for brightness or contrast, this is not a problem, the levels are near perfect, even in bright sunshine. 

Functions of the DSO Nano are accessed via buttons arranged along three sides of the screen.  Across the top are our sync mode, vertical scale, time base and a Y-Position adjust.  Last on this is access to the measurement features of the Oscilloscope. 

Along the right hand side of the screen is some trigger adjustments, a setting for probe scale (though only one type if probe is supplied) load, save and marker adjustments.  Along the bottom of the screen Trigger levels an voltage measurements can be controlled.

Most navigation is done using a 4 axis keypad on the front of the DSO Nano.  If you have used an analogue scope with it’s vast array of dials, knobs and switches trust me this device is simplicity itself to use in comparison.  One tiny gripe I have with the controls is this.  On the 4 way keypad, you use the left and right keys to move between the functions on the top or bottom menus the top and bottom (marked + and –) keys adjust each attribute.  However when you reach the end of the toolbar, the navigation between functions changes to the top and bottom keys (marked + and –) with the left and right keys adjusting the attributes.  I personally did not find this immediately intuitive to use though I grew used to it eventually.  Perhaps when device moves from Beta Seeed Studio will revisit this in the firmware if enough of the testers mention it.

Features

To test the Seeed Studio DSO Nano I used the soundcard of my EeePC901 as a signal generator.  I used the “Frequency Generator 2007” application from PAS-Products to produce some test signals for me. 

At start-up you have two traces on the screen a green one and a purple one.  The purple one is in fact an example waveform supplied on the DSO Nano.  Later on when you start saving your own wave forms they can be superimposed onto the display and will display in purple. The green waveform is your live reading.

The sync mode is set to auto by default, but the following modes are available:

• AUTO – Automatic synchronous sweeping mode, displays waveform even not triggered.
• NORM – Normal synchronous sweeping mode, displays whenever trigged.
• SING- Single sweeping mode, display when triggered, then stopped with latest triggered waveform.
• NONE – Random sampling mode
• SCAN – Scan mode, to check long period low frequency signal.

For most purposes AUTO is both sufficient and convenient to use.  I had to then set the Vt (Trigger Level) to get my wave form to become stable on the screen.  As you adjust Vt, a yellow marker line on the screen denotes the trigger voltage.  This makes it easy to set your trigger point, when the yellow marker intersects your waveform, you are in the right place.  Compared to an analogue scope this is amazingly simple to adjust.  On my analogue scope I would be twisting the trigger adjust dial like a safe breaker at this point!

Once the image is still, adjustment of the Vertical Scale, Timebase and Y position lets you zoom in on the part of the waveform of interest.  In my example to the right, you can see the rising edge of a square wave in close-up.  The controls make this very easy to get to. 

When it comes to ease of use, getting your waveform to display is infinitely more easy than tuning an analogue scope.  If you are new to using oscilloscopes (I don’t consider myself to be particularly adept) then the Seeed Studio DSO Nano definitely wins my vote over a second hand analogue device that you will pick up at a similar budget.

Measurement

Now I won’t pretend that a well calibrated analogue scope cannot give you incredibly accurate measurements.  Probably better in many areas than the DSO Nano will manage, but for basic measurements, this Digital “Scope” automates things well.  The Calculation mode will automatically tell you:

• FREQN – Signal frequency
• CYCLE – Signal period
• DUTY – Duty time
• Vpp – AC signal peak-peak value
• Vram – AC signal effective value
• Vavg – AC signal average value
• DC.V – DC signal average value.

I tried these out using the Frequency Generator application and the Nano was accurate to within at least 1 unit on signal frequency and more often than not gave the exact measurement.  I tested on a sine wave and a square wave with equally accurate results.

Further to what can be automatically calculated for you, Time markers and voltage markers can also be hand adjusted to give you a reading a particular points of a wave form.  The M button toggles their display on or off when you finish your measurements.

Bear in mind that if you buy a second hand oscilloscope you are unlikely to get one which has been recently calibrated without paying a premium.  The accuracy of the digital scope may surpass your average e-bay analogue example.

Saving Waveforms

Rather cleverly, the DSO Nano can also store waveforms for additional comparison.  It does so on a Micro SD card.  I personally chose a Transcend 2GB Micro SD card (Model no: TS2GUSD) to partner with my Oscilloscope.  Setting up your DSO Nano to use a SD card takes a little patience.  The Oscilloscope itself is unable to create a save file, only modify it.  So to get up an running you must do the following (on Windows systems)

1. Insert the card in your Nano.
2. Connect your DSO Nano via USB to your machine (you will need a mini USB cable, not supplied though I have picked up loads of these with cameras, phones etc)
3. Once the Nano is recognised (its seen as a card reader), try and visit via windows explorer, it may ask for a format, I quick formatted with default FAT32
4. Next you will have to change your folder view properties so that "known file types are unhidden" This is to allow you to create .DAT files
5. Now create a txt file, rename it to for example FILE002.DAT (seems to be case sensitive)
6. Do the same for as many files as you need i.e. FILE003.DAT, FILE004.DAT and so on…
7. Now when saving you can save the waveform to the card (well at least I can, looking at the forums some are having problems with this.

This allows you to quickly save a waveform for later comparison.  I was slightly disappointed as I thought that with a USB connection to my PC that I may have been able to display the waveforms on my PC.

Hopefully this is a feature that will become available at a later date.  I would really like to be able to produce graphics from the oscilloscope to share on www.justblair.co.uk or on forums.  Attempting to read the saved DAT file on the PC reveals nothing so far.  For the moment I will have to continue photographing the screen. 

Update!!  Just a couple of days after writing this review Seeed Studios released an early version of their PC software that allows you to convert the .DAT files on the DSO nano to bitmap images.  It still has to be converted to English as I write this, but it is functional! 

As it is going to be open source, volunteers have already made themselves avaiable for a MAC version of the same software.  Screenshot to the right…

Further Development

As I hope I have made clear, the Seeed Studio DSO Nano that I have tested is a “Beta Test” model.  As such when the full price device becomes available for order expect some changes to have been made based on the feedback of the beta testers. 

Happily the device is firmware upgradeable so as improvements are made, users can take advantage of them.  Features may be added or adjusted.

I for one would like to see the control system made more consistent and some method of reading the waveform data on a PC.  Perhaps even in Excel? 

Feel free to add product features you would like to see in the comments below!

Conclusion

If you are a hobbyist and were considering buying an oscilloscope to further your range, think very seriously before investing your money on a twenty year old scope.  The DSO Nano is shaping up to be a real contender for your cash.  Its pocket sized, well featured and very much easier to use than an analogue scope. 

Price wise Seeed Studio have pitched this device just right in my opinion.  Bear in mind that you will have to buy a Micro SD card if you wish to store and compare waveforms (and you will want to, remember it’s a single input device)

Build quality is sufficient, even quite stylish on the device.  The screen is very easy to read.  The quality of the probes means I don’t see them lasting.  I think that you would want to invest in some better quality probes and adapt them to mini jack use somehow. 

I would thoroughly recommend holding onto your cash until the Seeed Studio DSO Nano becomes available for order.  For most the 1 Mhz sample rate will be more than enough.  Ease of Use and compact design make this an ideal tool for the hobbyist!

Feast your eyes on the following video for some footage of the device in use.

DSO Nano Video from fanxiang on Vimeo.

Further news and details of the DSO Nano can be found here at www.seeedstudio.com