DIY USB impedance/capacitor/inductor measurement tool

[AlessandroAU]

I wanted to expand my toolset and be able to take impedance measurements. Of course there is the commercial option http://www.parts-express.com/dayton-aud ... m--390-806, but after shipping to AUS I'd be looking at $150 or so. I did some reading and come across this nifty program. http://www.speakerworkshop.com it seemed very easy to use with only a few external components needed http://www.claudionegro.com (find the "cables" page). So I built the test jig and took some measurements and it seemed to work ok, at least for a while. Eventually I started getting weird results, I chalked it down to my laptop's internal soundcard not being up to the task.

I decided to build a dedicated USB solution. I did more research and found the Behringer: U-CONTROL UCA202 a very decent and inexpensive ($30) USB sound interface. I preformed the mods listed here http://nwavguy.blogspot.com.au/2011/03/ ... endac.html to improve the low end response. This was probably the hardest part as it involved some SMD soldering. Then I added some switches and resistors to make calibration easier and put the whole thing in a box. I used some precision 0.1% resistors from vishay. Depending on components used the total cost could be below $50, not bad for a device that will take impedance plots, measure resistors, capacitors, inductors and estimate T/S parameters!

I've attached some pics and an impedance plot measurement of my table tuba. Can someone tell me if this is what the plot should look like?

Edit: Spelling

[J_Dunavin]

Very cool!

[LelandCrooks]

Looks about right. Nice.

[Bill Fitzmaurice]

I've attached some pics and an impedance plot measurement of my table tuba. Can someone tell me if this is what the plot should look like?

+1.

[sine143]

whats your table tuba loaded with?

[AlessandroAU]

whats your table tuba loaded with?

I've got it loaded with a DCS205-4