Impedance Analyzer Build and Experiments

[Fraser]

TL;DR


Just found my Analogue Devices AD5934 development board. Pictures attached.

Just in case they are of any interest to readers.

I bought it to build a low frequency impedance analyzer but it never happened  I do not see me needing one now either.

If anyone has a need for this brand new unit, make me an offer on it 

Fraser
UK

[Fraser]

AD5934 data sheet.

It has a lower frequency range of 1kHz to 100kHz excitation frequency so I was going to use it on speaker networks and transducers.

Fraser

[timofonic]

What's the advantage over the Component Tester? I'm "confuccio"

[jaxbird]

Just a quick thanks to everyone expressing interest in this project.

I have a number of PM's I haven't responded to yet, sorry, it's been another busy week at work. I'll respond this weekend.

Hope everyone will have a nice weekend.

Cheers
Jake

[jaxbird]

Count me in for a kit.

Already have an Analog Discovery--this seems like an excellent addition to its functionality.

Question about calibration--do we need to come up with precision L,C values in order to do that?
I do have a good bench meter and frequency counter.

Thanks,
Randy

Hi Randy,

Short answer: nope, not needed. Just do the Open and Shorted calibration.

Long answer: Simple Open/Close calibration will work just fine. I have been working on a Open/Close/Reference in case it makes sense for anyone (you'd need some reference resistor with very low inductance/capacitance), but my experience is that the simpel Shorted/Open calibration is most accurate.

Cheers,
Jake

Edit: just saw Carrington already answered the same So I guess double confirmation.

[jaxbird]

What's the advantage over the Component Tester? I'm "confuccio"

Not 100% sure what the Component Tester is, but I assume you are referring to the excellent cheap Atmel based component testers doing resistors, diodes, transistors, capacitors, inductors etc. This is an impedance analyzer, as in it will tell you the impedance of any DUT at any frequency (well within 1Hz to 10MHz+) this means you can plot e.g. the ESR and dissipation factor for a capacitor at any frequency within range whereas a normal LCR meter (or the component tester) is locked into a specific frequency or in large steps usually maxing out at 100kHz. Viewing a plot for a component's parameters vs. frequency is a good way to get a better understanding of how this component will perform in a specific circuit.

Or you could use it to measure the impedance of a loudspeaker, or find the resonance frequency of a piezo, or even test the impedance of your blood.

[jaxbird]

Just found this thread. I believe I had an original AD impedance analyzer evaluation board that uses this chip.

I shall have to dig it out 

Thanks for a very interesting thread 

Fraser

Hello Fraser,

I originally tried to make some kind of analyzer using the Analog Devices impedance IC, but at some point I switched to the full blown Analog Discovery unit as I found I needed better performance than what I could ever achieve with the Analog IC alone, that was kinda where things got serious

Current project is 100% based on the Analog Discovery and it's dual 100Msps adc and dac.

Cheers,
Jake

[Fraser]

Ah I see.

Many thanks for bringing me up to speed 

Fraser

[jaxbird]

+1 for Kit 

I'm in for a kit as well.

Count me in for a kit

+1 for a kit.

I'm in for a kit.

Thanks, I'll add you to the count.

I have a pick and place machine/line and could possibly assemble a small-med batch if it is helpful.
Sent from my horrible mobile....

Thanks for the offer, I think for now the volume is much too low to consider any manufacturing, it will probably remain that way, it's a bit of a niche project, I expect it will be below 50 boards in total. But if things change, like e.g. Dave or Digilent/National Instruments promotes the project and hundreds of boards are needed I'll make sure to ask you if you are still interested.

Cheers,
Jake

[Neganur]

Fun project, I'd take one.

[rx8pilot]

ably remain that way, it's a bit of a niche project, I expect it will be below 50 boards in total. But if things change, like e.g. Dave or Digilent/National Instruments promotes the project and hundreds of boards are needed I'll make sure to ask you if you are still interested.

Just for clarification, I was only intending to help the forum members as a favor. I do not have an assembly business, but rather a business that is capable of assembly. The goal was to push/support this project if needed. If you get a deal with distribution - I would be the worst possible option for assembly. 

[jaxbird]

Fun project, I'd take one.

Thanks, I promise hours of joy and maybe some frustration Impedance measurement is serious business actually it's very educational to spend time measuring everything you can get your hand on and observing all the parameters, like how many uH does this wire have per mm or if I twist those wires how much capacitance etc.

[jaxbird]

ably remain that way, it's a bit of a niche project, I expect it will be below 50 boards in total. But if things change, like e.g. Dave or Digilent/National Instruments promotes the project and hundreds of boards are needed I'll make sure to ask you if you are still interested.

Just for clarification, I was only intending to help the forum members as a favor. I do not have an assembly business, but rather a business that is capable of assembly. The goal was to push/support this project if needed. If you get a deal with distribution - I would be the worst possible option for assembly. 

Understand, I'd be happy to send you a batch for assembly for anyone who'd rather not do the assembly themselves, but it's really not hard to manually assemble, just SO8/16 parts and 0805 components, only some protection diodes are SOT23 and might be a bit challenging for those wielding a 100W solder gun from Frys.

The great thing about a project like this is that anyone who'd find this even remotely interesting and fully understand how to use it, is likely to be an expert at SMD soldering already

[jaxbird]

I'm still working on improving the instrument, it will be an ongoing effort, don't expect perfect performance at all impedances right out of the box, but it will be improving as I get better at understanding calibration and compensation.

Anyway, this week I've done some work on the open/short/reference calibration method, originally I never used this method because my implementation provided worse results than the simple open/close calibration. However, spending some time understanding the complexities involved, I have come up with a better implementation that provides superior results to the simle open/close calibration. Important is that the reference resistor must have as little inductance and capacitance as possible, I have been using 0805 resistors for my experiments with good results, these are tiny, but near idea for this purpose.

This is the general idea for this kind of calibration:



Edit: keep in mind these are all complex values.

[ruairi]

Excellent stuff.  Do you think this will allow the use of longer test leads with acceptable accuracy?  I am considering building the whole thing into a dedicated instrument of sorts with a tablet.

Cheers,
Ruairi

[jaxbird]

Excellent stuff.  Do you think this will allow the use of longer test leads with acceptable accuracy?  I am considering building the whole thing into a dedicated instrument of sorts with a tablet.

Cheers,
Ruairi

Thanks, unfortunately longer test leads will never work well with this solution, only so much signal to work with and added inductance will have a significant effect at higher frequencies/lower impedances.

I have tested configurations like these nice shielded leads: (but results were not as good as short leads)



I have consulted experts as evident in this picture:

[jaxbird]

Quick update I've ordered enough for about 25 kits, that should cover everyone, I'll post here when I have received all the parts, I think Paypal is probably the best payment even they have fairly high fees per transaction, but they also have a lot of buyer protection.

Anyway, make sure you understand what I will supply is a kit, you have to solder it together, if you are not familiar with surface mount components, don't order this kit. Also if you do not own an Analog Discovery unit (1 or 2) you should not buy this kit.

Also you are only paying for the hardware kit, the software, it is free for any non commercial use in the current version.

[Floyo]

I might be a bit late to the party, but if another kit is available I wouldn't mind receiving one.
There are lots of useful things I could use it for. Soldering should not pose any problems

[aardvarkexpress]

Hi jaxbird,

I just found this thread.  It looks like an awesome project!  I'd love to be able to play around with this sort of instrument.

Do you have enough parts for another kit?

Cheers,

Tom

[Rerouter]

Any idea what a ballpark price would be if you bundled it with a discovery, everywhere i am looking they are about $500 vs the $100 mentioned earlier,

[Efig]

Hi jaxbird,

Excellent stuff. I am interested in playing with it. This will add great value to discovery.

Do you have more kits left available?

[ruairi]

Any idea what a ballpark price would be if you bundled it with a discovery, everywhere i am looking they are about $500 vs the $100 mentioned earlier,

I can't see how it would be feasible for Jaxbird to by and resell Analog Discoverys with his kit.  It would require a huge investment, not to mention tax/duty issues for international sale.

Digilent list the Analog Discovery for $259 USD on their own store.  The founder of Digilent did a fascinating interview recently on The Amp Hour and gave a discount code too, check out the interview, it may still be valid.

[steverino]

Any idea what a ballpark price would be if you bundled it with a discovery, everywhere i am looking they are about $500 vs the $100 mentioned earlier,

I can't see how it would be feasible for Jaxbird to by and resell Analog Discoverys with his kit.  It would require a huge investment, not to mention tax/duty issues for international sale.

Digilent list the Analog Discovery for $259 USD on their own store.  The founder of Digilent did a fascinating interview recently on The Amp Hour and gave a discount code too, check out the interview, it may still be valid.

Digilent had a discount code of AMPHOUR recently, but not sure if it's still valid.  It's worth a try if you're purchasing a Discovery.

[Rerouter]

Sorry if I didn't make it clear but yes in such a case I would pay him before he ordered the thing, I thought he was still a student so the discount would apply for him.

[jaxbird]

Sorry if I didn't make it clear but yes in such a case I would pay him before he ordered the thing, I thought he was still a student so the discount would apply for him.

Nah, sorry, I can't offer any specials on the Analog Discovery units. I don't think I'd ever qualify for the student discount, by age 17 I was laying down natural gas pipelines instead of studying, university never really was an option for me, but I've caught up later in life through reading and general interest.

I believe I got mine for around $200 from Microchip direct, but I don't think that deal is available anymore, another option is, since it's an instrument required for many electronic engineering courses, to try find one on ebay etc. surely there must be a lot of students who needs money more than their Analog Discovery. My solution is designed to work with both version 1 and 2.