Update - Audio Vector Network Analyzer

[Bob Larkin]

I want to report that the Teensy 3.6 plus the Audio Adaptor board has worked out well for the Audio impedance measuring project. It is not done, but it is measuring impedances with good accuracy in the 10 to 10,000 Hz range. A summary of where this is at, including software source, is at
http://www.proaxis.com/~boblark/AudioVNAWeb/AudioVNA_RSL.html

I was able to work with just "stock" audio objects, which speaks well for the library. Thanks, Paul.

Cheers, Bob Larkin

 

[Bob Larkin]

A major update. First the previous link to the Audio Vector Network Analyzer is out-of-date. A new Web page with lots of details is at
http://www.janbob.com/electron/AVNA1/AVNA1.htm
This is a redo of the project reported above including information on hardware construction as well as .INO software.

QEX magazine, published by the Amateur Radio organization, ARRL, has a 12 page article in the May/June 2018 issue. Info on acquiring a copy of the magazine is on the referenced Web page.

This has worked out to be a high quality measurement device for both impedance (R-L-C components) and transmission (input/output devices) measurements from 10 to 40,000 Hz. It uses the Teensy 3.6, the Audio Adaptor and the 320x240 Touchscreen display. The software takes advantage of the great Teensy Audio Library as well as flexible data types such as complex arithmetic. The Teensy made it easy to have both touch screen control as well as full control from the host PC.

Here is a picture of the AVNA in a retro wooden box measuring capacitors.

I hope this is a useful tool for experimenters!

Bob Larkin

 

[Bob Larkin]

The Vector Network Analyzer covering 10 Hz to 40 KHz has been seeing improvements. Probably the most exciting is the 3-D printed case designed by Mike Runyan.


The project uses the Teensy 3.6, the Teensy Audio Adapter, and the PJRC 320x240 touch screen. The PCB is available from OSH Park and full building information is available at the web page http://www.janbob.com/electron/AVNA1/AVNA1.htm

Oh also, it accurately measures stuff! Details are on the web page.

Bob

 

[LachAus]

Very cool. Would definitely be worthy of being posted in the 'Blog-Project-Submission' part of the forum.
It would be nice if there was something like a Github page - especially with the different versions/updates. I found the way it's laid out in the webpage a bit messy to follow but at least all the latest stuff seems to be there

 

[Bob Larkin]

News Note: The Teensy-based Audio Vector Network Analyzer has been built by a fair number and it continues to serve that original job of measuring components and circuits. But, it has grown!

It now uses the same hardware to generate 4 Waveforms that can be added to Gaussian White Noise, all with calibrated levels. It has a calibrated FFT spectrum analyzer. And it has a Vector Voltmeter that can measure amplitude and phase down into the microvolts. The range is still 10 Hz to 40 kHz. Here is a shst of the Vector Voltmeter and Spectrum analyzer.

Teensy files are now at GitHub https://github.com/boblark/AudioTestInstrument
The description of the hardware is still the same location http://www.janbob.com/electron/AVNA1/AVNA1.htm.
Also Evans W. has created a 39 page, detailed pdf User's Manual with lots of information, including details for doing things through the USB-Serial control. Seehttp://www.janbob.com/electron/AVNA1/AVNA-UsersManual.pdf

It is still a DIY construction project, but of moderate complexity. Go Teensy!

 

[MarkT]

Looks great - I'm very tempted to build one - I don't really need one, but I'm still very tempted!
One thought is that by replacing the opamps with something like the AD8656(*) you'd have enough drive
level to avoid the need for the transistor buffer and reduce the THD sufficiently to be able to offer a
usable THD meter functionality too...

(*) 0.0007% THD at 1kHz, +/-220mA drive capability, much lower noise than the LMC660 too (which
isn't exactly spec'd for audio is it?)