Impedance analyser - audio up to a few MHz

[AndyC_772]

Hi

My trusty HP 4395A recently decided to start misbehaving, and although I'm sure it's a simple fix (display problem), it's getting on for 25 years old now and I shouldn't really be relying on vintage gear that could fail more seriously at any minute.

My main use is measuring the impedance of ultrasonic transducers, in the range from a few kHz up to single digit MHz.

Can anyone please suggest an instrument which might be suitable? Most of the impedance analysers I've found seem to retail for £10k+ and/or struggle to operate at the low frequencies I need.

Thanks in advance:)

[mawyatt]

The Hioki IM3536 LCR meter might be considered, we selected this for its range of 4Hz to 8MHz. It's not cheap tho, ~$4.6K.

Another option might be using a modern DSO that has Bode capability, like shown here:

https://www.eevblog.com/forum/testgear/admittance-measurements-with-dso-awg-with-bode-function/msg4491952/#msg4491952

Best,

[bdunham7]

I don't know whether this would be adequate for your tasks, but it does operate in the range you need.  I have one but have not used it extensively yet.  If you would like me to run some specific test or measurement to see what the results look like, just ask.  I have the original Analog Discovery, not the 2, but the results should be similar.

https://digilent.com/reference/add-ons/impedance-analyzer/start

https://digilent.com/reference/test-and-measurement/guides/waveforms-impedance-analyzer

https://digilent.com/reference/test-and-measurement/analog-discovery-2/start

[zrq]

Assuming you already have good fixtures and calibration standards (and probably some coding skill), the ADMX2001B module may worth considering.

[AndyC_772]

Thanks for the suggestions everyone, I really appreciate it.

It does seem like there's a gap in the market here, but then again, I guess there just isn't the volume to drive competition and bring prices down. Clearly it's physically possible to make a suitable device with fairly simple hardware.

In the absence of an affordable direct replacement for the 4395A, I suspect we'd look at buying the Hioki. If it needs some additional software to run a full impedance sweep and plot the results, that sounds like a good project for a student on work experience.

[ace1903]

I tried combination of Digilent's impedance-analyzer + AD1 and resolution is quite poor since it has only 3 load resistances choice(regular piezo speaker in 22-60KHz range).
In frequency rage that I needed, looks like sweep is discontinued and it triggered some resonances that messed measurements(don't have another scope to verify this).
ADMX2001 looks perfect but it lack schematics and interface is bit strange.
Does anyone knows if schematics and some firmware source is included in the box with ADMX2001?

[Slh]

N4L have a range https://www.newtons4th.com/products/impedance-analyzers/impedance-analysis-interface/. The interface takes a bit of getting used to but they do work well. N4L are also very responsive on the phone if you have issues.

I think it's less that 10k but not sure

[Kean]

What about the Omicron Lab Bode 100?
https://www.omicron-lab.com/products/vector-network-analysis/bode-100

PC controlled VNA with FRA & Impedance Analysis.  1Hz to 50MHz, and a good range of accessories to cover many use cases.
Base price is about €5k.

[mawyatt]

Thanks for the suggestions everyone, I really appreciate it.

It does seem like there's a gap in the market here, but then again, I guess there just isn't the volume to drive competition and bring prices down. Clearly it's physically possible to make a suitable device with fairly simple hardware.

In the absence of an affordable direct replacement for the 4395A, I suspect we'd look at buying the Hioki. If it needs some additional software to run a full impedance sweep and plot the results, that sounds like a good project for a student on work experience.

We wrote some code in Python for the Tonghui TH2832 and Hioki IM3536 LCR meters for sweeping various parameters.

Mind, we are not good at SW, so don't expect polished routines, just functional.

https://www.eevblog.com/forum/testgear/lcr-meter-plot-software

Someone could clean these up with proper UI and graphics, we had grad students do this back when an adjunct, but none around now we are retired (semi-retired)

Be sure and check out the various fixtures we've developed/modified for these LCR meters, including the DC Bias Adapter which has proven quite useful!!

https://www.eevblog.com/forum/projects/bias-network-for-lcr-meter/

https://www.eevblog.com/forum/testgear/smd-test-fixture-modifications/msg3999139/#msg3999139

Best,   

[DaJMasta]

What about the Omicron Lab Bode 100?
https://www.omicron-lab.com/products/vector-network-analysis/bode-100

PC controlled VNA with FRA & Impedance Analysis.  1Hz to 50MHz, and a good range of accessories to cover many use cases.
Base price is about €5k.

In the same vein, there are units by AP Instruments and others.  If you're considering used equipment (not sure if they're available new), Chroma makes an LCR Meter line with MHz frequency ranges and built in plotting - I've got a 11050-5M which has a couple of annoying "features" (doesn't remember settings over a power cycle, for example) that performs well.  Hioki is one of the standards, but you would need one of their newer line to get the GUI and built in plotting - older units could certainly do the job with a host PC and a little display software.

[David Hess]

What about the Omicron Lab Bode 100?
https://www.omicron-lab.com/products/vector-network-analysis/bode-100

PC controlled VNA with FRA & Impedance Analysis.  1Hz to 50MHz, and a good range of accessories to cover many use cases.
Base price is about €5k.

Might as well also mention Cleverscope which supports impedance analysis from DC to significantly above 1 MHz.