Tuesday, December 31, 2013

Seed Studio DSO Quad

I can't believe it's been a whole year since I posted here.  Actually,  it looks like I started something back in March but never finished.

OK, well anyway, Santa brought me a SeedStudio DSO Quad, a pretty cool little thing.  Surprisingly little is posted online about it, so I thought I would comment.

The DSO is a small box about the size of a cell phone.  However, it is in a milled aluminum case, so it is  considerably heavier than your typical cell phone.

It is quite a cute little device.  It has two analog and two digital channels.  One of the digital channels can display the sum or difference of the analog channels, the OR or AND of the digital channels, or a previously recorded channel, or of course simply be the second digital channel. 

The time scale ranges from 1 second to 0.1 microsecond per division.  The analog channels from 50 mV to 10 Volts per division.

In addition to being a storage scope, the unit can provide sine, square, triangle or sawtooth waveforms from 10 Hz to 8 MHz with duty cycles from 10 to 90 percent.

The memory for traces is 4096 samples, of which 360 are displayed at a time and may be scrolled through.  There are menu selections allowing for fewer samples to be stored.

The unit can also display frequency, duty cycle, high and low voltage, etc.  There are cursors for both time and voltage.

One of the really slick features is the ability to store screen captures and even CSV files on an internal USB drive which can then be picked off on your PC.

The device ships with 2 pretty nice Mueller probes and 2 "digital probes", with annoyingly short leads.

Before going into the details, let me mention some of the deltas.

Even though one would think that with 72 MS/s the unit would work well into the megahertz range, in fact things seem to fall apart around a MHz.  In fact, when fed fast waveforms the unit seems to lock up frequently.

The unit I received was version 2.7.0 of the firmware.  The little manual that came with the unit was for 2.6.0.  There were apparently very significant changes.  First, the user interface was dramatically changed between the versions making most of the manual useless.  There were apparently some significant hardware changes as well.  The manual mentioned a series of capacitors inside the unit for calibration, but on 2.7.0 the calibration is performed from a menu.  (Tedious, but relatively obvious.)

I was able to find a user written manual online referencing 2.7.0, but it was poorly written and incomplete, so although I have already found this little scope incredibly useful, there are still surprises every now and then.

Supposedly it is open source and the firmware can be upgraded, but I have yet to discover those details.

OK, so on to some of the grody details.

The left side of the unit has three jacks, one for each of the two analog channels and one for the waveform output.  I haven't tried the waveform output so I have no idea whether it does what it claims.

On the right side are jacks for the two digital channels, a mini USB (not micro like a cell phone), and an on/off switch.  The internal battery is recharged through the mini USB and seems to last reasonably well.  I haven't tried to see what it takes to drain.

The top is where all the action is. There are four buttons, and two "navigators".  The navigators are switches than can be pushed left and right or down.

The left button is fairly obvious.  It allows you to hold/restart the display. The next button brings up a menu that allows you to save data or screen captures, adjust the backlight and beep volume and access the calibration screen.

The next button brings up a popup showing you a number of measurements like high/low voltage, RMS voltage, frequency, etc.  Holding down that button brings up a different popup that allows you to select the measurements that will appear on the measurement popup.  It also allows you to select what measurement will be shown at the bottom of the screen.

The right button moves between the top and right menus.

The left navigator changes the value of the currently selected menu choice.  The right navigator selects what menu choice you will change.  For example, should you move the right navigator until the cyan block toward the left is blinking, moving the left navigator right or left will choose between AC or DC coupling channel A, or turning it off entirely.  Pressing the left navigator on the top menu moves to the second row where, in this case, you can select the number of volts per division.

For chanel C you may only select DC coupling or off; there is no volts/per division selection for digital channels.

For channel D, you my choose between off, Channel D, A+B, A-B, C&D, C|D, or a recording of one of the four channels.

Trigger choices are AUTO, NORM, SINGL or NONE.  The right three blocks on the top menu choose the shape of the output waveform, its frequency and duty cycle.

Beneath those right three blocks is a waveform display showing what part of memory is being displayed.  There is a 'T' displayed at the point of the trigger, which may be shortly after the beginning of memory or in the middle of the memory.

The right side menu allows you to select the trigger source, threshold and pulse shape, scroll through memory, select where the trigger will be, and allow you to move voltage and time cursors, the differences between which are displayed on the bottom of the screen.  You may also select the number of samples and may move the individual traces up and down.

I noticed a curious thing just today;  the unit is cheaper direct from Seed Studio than either from Sparkfun or Amazon.  However, I think Seed ships from Asia, so shipping might be high, and I get the impression the wait is considerable, as well.

So all in all, quite a nice little scope.  It has some issues, but really not too bad for the price.