Building an LCR Meter

RE: Building an LCR Meter

pexeso — Mon, 03 Feb 2020 16:19:06 GMT

Dear Shabaz,

I made a simple piece of equipment with LM358 according to the internet schematic and I tried the visual analyzer but it's always stuck in calibration.I tried with disconnected and connected measuring cables,

I changed the frequency, normal resistances etc.but it didn't helped mi.I send you a picture of the whole thing and ask for your advice on what I can do.[View:/resized-image/__size/1600x900/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-7e670425-3ba1-4180-abe9-29f7b205587f/contentimage_5F00_205175.png:1600:900]

RE: Building an LCR Meter

reyntjensm — Mon, 30 Dec 2019 17:46:03 GMT

Dear Shabaz,

I got i somewhat working..

I was wondering what is the function of the 10K pull down resistor R7 at the input?

I guess this will only add to the measurement and hence be incorrect?

Or is there any other function for this resistor?

I hope to hear from you soon again.

RE: Building an LCR Meter

reyntjensm — Wed, 18 Dec 2019 16:16:02 GMT

Dear Shabaz,

So i made a pcb for this project and assembled everything.

Al tough when i try to use the visual analyzer software, i'm unable to do anything.

When i try to calibrate or use the ZRLC meter i got a warning: undefined external error, error starting device, try to use another device or change the settings.

I do see some lights flashing on my scarlett 2I2 interface.

Any idea on how to fix this issue?

Thank you for the support!

RE: Building an LCR Meter

reyntjensm — Thu, 21 Nov 2019 16:55:14 GMT

Hello,

Great project! But i don't understand how it works?

It seems like you are taking the signal from the sleeve in the 6.35mm connector?

Sleeve is always ground right?

So how can this work?

RE: Building an LCR Meter

shabaz — Wed, 24 Jul 2019 14:31:33 GMT

I've run some tests with this project and VA64, and compared them with an (I think) in-cal LCR meter, EUCOL U2832.

These tests were done at 1kHz.

Capacitor SpecificationThis projectCommercial LCR meterRatingPart CodeESR (ohm)Cap (uF)ESR (ohm)cap (uF)A22uF 50VEEUFM1H2200.48220.760.46220.59B22uF 35V8700556730020.12822.3180.10122.146C100uF 10VA758EK107M1AAAE0160.07999.60.04898.1D10uF 16V8601603720012.6799.0612.738.95E1uF 50VMCRR50105Z5UM00501.270.9172.20.941F0.1uF 50VA104K15X7RF5UAA19.40.088534.00.093

All were done with the 10 ohm known resistance setting, except F which was done with the 100 ohm setting.

Capacitor B and C are aluminium polymer.

Capacitor A and D are aluminium electrolytic.

Capacitor E and F are ceramic.

The measurements are pretty good in general. But it's clear there is a significant discrepancy in a couple of the measurements. For the last capacitor (F), I checked in another commercial meter (not in cal), and it reported 28.3 ohm 0.0913uF, i.e. very close agreement with the in-cal meter, so that's fairly conclusive that this project hardware or software has some error in it. I still need to think about it.. I thought maybe the lengths were not equal (since this is a prototype on two PCBs) but I deliberately extended the wires of the source wires, and there was no difference in the measurement, so the software is correctly nulling out the phase discrepancy during calibration.

Also for the same capacitor F I tried using the 1000 ohm setting, and again the result barely changed. So it's unlikely to be resistor accuracy (I used 0.1% thin film 0805 sized resistors).

Once I have the cables ready for the PicoScope, I'll try that too, on these same capacitors.

RE: Building an LCR Meter

fmilburn — Wed, 24 Jul 2019 00:35:32 GMT

Hi Shabaz,

As usual, a wonderfully clear and complete write-up with all the necessary links. Your build is really clean, especially since you built it out of spare PCBs. The author of the Visual Analyzer software obviously put a lot of time and effort into that as well as the documentation on how to use it as LCR meter. It is nice that it works so well with the Scarlett 2i2 USB sound card. I think before I go to much further with my own LCR design I need to finish up some of my uncompleted projects :-) as well as investigate various approaches. Now that I have the Keysight it should be easier... Good stuff!

RE: Building an LCR Meter

noorpuri — Tue, 23 Jul 2019 22:45:37 GMT

A nice effort . It is also better to include Impedance related algorithm should be also included.

RE: Building an LCR Meter

jw0752 — Tue, 23 Jul 2019 22:33:17 GMT

Hi Shabaz,

Another awesome Shabaz Project. Thanks for all you contribute to making this forum the best.

John

RE: Building an LCR Meter

shabaz — Tue, 23 Jul 2019 21:04:15 GMT

I suppose I should write up the other experiments! I tried using the visual analyser to measure PSU noise.. using another variant of the microphone amplifier circuit. I'm really milking that PCB layout : )

this is the Tenma 72-2705 PSU that Rod discovered ( Clearance - 30v 3A TENMA PSU ), which is fairly clean for a bench supply:

[View:https://players.brightcove.net/1362235890001/NkxiVJdjx_default/index.html?videoId=6063244521001:740:466]

Next I tried an ancient Thurlby PL154.. lots of 50Hz mains and harmonics. It was perhaps much better new.

[View:/resized-image/__size/620x230/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-7e670425-3ba1-4180-abe9-29f7b205587f/6332.contentimage_5F00_205168.png:620:230]

Finally a homemade PSU (Building a Linear Power Supply Module ):

[View:https://players.brightcove.net/1362235890001/NkxiVJdjx_default/index.html?videoId=6063245898001:740:466]

However, the cabling picked up some mains hum, they were not shielded all the way, and the PSU and the amplifier were not in a metal enclosure. For the homemade PSU, if I power it off, I still see similar output:

[View:/resized-image/__size/620x228/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-7e670425-3ba1-4180-abe9-29f7b205587f/4278.contentimage_5F00_205170.png:620:228]

For all of these tests, the conditions were similar, i.e. all were set to the same voltage (14V), with no load.

RE: Building an LCR Meter

three-phase — Tue, 23 Jul 2019 20:59:33 GMT

This looks quite interesting to me. I have been measuring the coils I have been winding with a Picoscope and an impedance viewer written by one of the members of eevblog.

eevblog LCR Impedance viewer

Would be interesting to build and compare results at some point.

Kind regards.

RE: Building an LCR Meter

DAB — Tue, 23 Jul 2019 17:56:59 GMT

Interesting project.

DAB

RE: Building an LCR Meter

ralphjy — Tue, 23 Jul 2019 15:00:13 GMT

The Visual Analyser app is a very clever use of a sound card. Wish I could have had something like that when I was learning electronics. Of course, PCs didn’t exist back then [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-7e670425-3ba1-4180-abe9-29f7b205587f/contentimage_5F00_938.png:16:16].

Very nice project.

Ralph

RE: Building an LCR Meter

genebren — Tue, 23 Jul 2019 14:33:02 GMT

shabaz,

Nice project! I like how you were able to re-use PCBs from a prior project to do this test. Very encouraging results.

Thanks for sharing,

Gene