Peter Cochrane's Blog: Lab on a laptop

Written at the Dayton, Ohio airport and dispatched to silicon.com via free wi-fi

For much of my life I have been involved in solving complex problems using a combination of hypothesis, experiment and analysis. And I have seen the power of computing increase within the test equipment used in experiments to the point where the days and months of work, required when I was a young engineer, have now been collapsed to minutes in the modern world.

This really came home to me in the last few days when working remotely with a young student studying sound engineering. Late one night I received a request for help along with static pictures of time waveforms and spectrum. After a few moments it became clear that I needed to expand the scales and change the area of focus. I called the student using VoIP, and after a short discussion he decided to send me a sound file. Listening to the file, a single note on a guitar D string, I suggested that there was indeed some harmonic distortion.

I outlined why I needed to expand the scales when he suggested that I download an application package. Here was a soft oscilloscope and spectrum analyser for free! It took seconds to download, a minute to load and a few minutes to become familiar with the detailed operation. Once it was set up, in went the sound file and out came pictures that I could now adjust. From the time waveform I could see evidence of at least two harmonics and, with a lot of expansion, the presence of 50Hz power hum from the pick up feed/amplifier.

Expanding the spectral diagram, and producing a sonograph, it was clear the D string was producing second and third harmonics, whilst higher components were insignificant. Most interesting of all was a spurious signal plus harmonics that we quickly resolved to be the A string. So plucking the D string set up a sympathetic vibration of the A string. Job done! We had it all; it was now clear what was happening.

Start to finish the whole process took 30 minutes including some detailed discussion on the physics of guitar strings, neck and body structures. The student was happy, and I was amazed. Just 10 years ago the task would have involved $10k worth of test equipment in a lab.

Discussing this with some engineering colleagues later, the thorny issue of true understanding came up. Did the student really get it? Would he not have understood more in a lab with the real thing? Broadly the discussion was about understanding test equipment, and the hands-on experience of manually adjusting time bases and scan rates etc.

I am not at all negative about the modern solution, quite the reverse, because I can remember just how few people could really drive an oscilloscope and spectrum analyser. Worse, even fewer really understood the relationship between the time and frequency domains.

What I had just done with a student in half an hour was a near miracle to me. I can only imagine the potential for accelerated learning, experience and productive work in future. But best of all, I now have my own lab on my laptop!