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The incredible shrinking DSO

Martin Rowe & Kenneth Wyatt- May 8, 2012

A version of this article appeared in the Test Digest section of the June 2012 issue of Test & Measurement World. See the PDF.

I recently purchased a small digitizing oscilloscope, the "DSO Quad," from Seeed Studio (see links below). While this instrument may merit considersation as a toy, or at best, a conversation piece, some of the specs are certainly worthy of the $199 price. I'm impressed that that the entire product, plus rechargeable LiPo (lithium polymer) battery, fits into such a small package.

The DSO Quad oscilloscope is just about the size of a standard business card and only about 13 mm thick. Click on image to enlarge

The unit is slightly larger than a standard business card and it comes with two Mueller 10:1, 100-MHz probes with tiny MCX RF coax connectors. The DSO Quad has two analog channels and two digital channels. The sampling rate is 72 Msamples/s. I measured a bandwidth of about 3 MHz. The vertical scale is adjustable from 20 mV/div to 10 V/div (8-bit resolution) and the horizontal sensitivity is 0.1 µs/div to 1s/div. Input coupling is AC or DC and triggering is Auto, Normal, and Single. There are several trigger modes: rising/falling edge, pulse width, and level.

The DSO Quad uses an ARM cortex M3 (32 bit) processor and integrated FPGA with high speed ADC. There's an internal 2 Mbyte USB-connectable RAM for waveform storage and instrument setups. The 3-in. color display includes channel information/setup along the top and it displays automatic measurements (V_MIN, V_MAX, V_PP, V_DC and V_RMS and V_BATT) along the right side. The unit can also perform channel math functions: A+B, A-B, etc. All these instrument configurations are controlled by toggle switches and a row of buttons along the unit's top edge.

In addition to being a DSO, the DSO Quad is also a signal source. It has two built-in signal generators, an 8 MHz variable-duty-cycle square-wave generator and a 20-kHz function generator (sine, triangle, and sawtooth). These signals come out through a separate connector.

The DSO Quad's firmware is open source and an active group of beta testers and other hobbyists develop additional functionality and make bug fixes. You can download periodic firmware updates from the user group page and load them through the unit's mini-USB connector.

The DSO Quad is available through www.seeedstudio.com/depot/ (under "Hacking and Measurement").
You may access the user forum at www.seeedstudio.com/forum/viewforum.php?f=22.
A YouTube video demonstrates the basic operation.