Measuring small capacitance with KS34465A & TH2830

[The Electrician]

down to sub mili ohms internal resistance on some of the caps i use right now.

Are these MLCC large value caps?  Who is the manufacturer?  Can you give a link to a spec sheet?

[nctnico]

That's not how the inside of ours looks, it has separate wires from each BNC to the plunger, no shorting bar!! Suspect the wires terminate at the plunger metal shaft and form a somewhat Kelvin type connection. There's also a ground wire across each BNC which has the solder lug terminal and goes to the center shield.

This looks much better than the HP 16334A fixture The Electrician showed. The closer you get the Kelvin connection to the DUT, the better.

Below the recommended connection to a DUT from the manual for the HP4274 LCR meter:


I have made a set of Kelvin clips using this schematic and it allows accurate readings over the entire frequency range (not with the HP4274 though; got rid of it a long time ago).

[mawyatt]

You can see that the HP fixture has the internal paint masked off where the BNC connectors are bolted to the sheet metal.  There is also some paint masked off where the wires penetrate the sheet metal, and where the little brackets at the end are riveted on.

The 3rd party fixture we have didn't do the masking and the entire case and lid were powder coat painted after all the machining. So we had to selectively remove the paint in areas where ground contact was required.

Evidently the TH fixture that oz2cpu has is properly prepared regarding grounding, which isn't surprising since Tonghui seems to be a 1st class equipment supplier, certainly so with the 3 Tonghui devices we have.

Best,

[The Electrician]

There was some question earlier in this thread as to the frequency capability of the SMD fixture.  I found a manual for the HP 16034E version: https://www.keysight.com/us/en/assets/9018-01396/user-manuals/9018-01396.pdf?success=true

The spec says max 40 MHz, but on page 9, figure 1-5 shows the error vs. frequency; 25% error at 40 MHz!!

I suspect the low-cost eBay version without the shorting bars can't do as well.

[oz2cpu]

news : i just opened my TH26008A smd fixture
it is not with paint on any alu surfaces inside anymore,
this means all parts have good connection, and this also explain the good shielding on my unit,

>Are these MLCC large value caps?  Who is the manufacturer?  Can you give a link to a spec sheet?

AVX 22201C106KAT2A

10uF 100V 2220 size
XC is 170mOhm at 100kHz
ESR is 0.9mOhm (yes, this meter can measure both XC and ESR)
SRF is 1.4MHz
attached is my DC voltage tests also.
and also my component test pcb for SRF using SA, this way i can test from kHz to GHz

[oz2cpu]

PICTURES of the latest version TH28008A fixture internal parts

[nctnico]

and also my component test pcb for SRF using SA, this way i can test from kHz to GHz

That looks very interesting. Can you share more about the design? I noticed you included an attenuator at the in & outputs; I guess to get a better impedance match.

[oz2cpu]

> Can you share more about the design? I noticed you included an attenuator at the in & outputs; I guess to get a better impedance match.

sure can, if you send me your email, i send you the gerber zip, so you can order this design,
here is a youtube link to a detailed explainer about this :

https://youtu.be/y79nOd8GLWI

i keep one with 0R on the centre, and then use that to calibrate the analyzer tracking generator, for a flat line,
now swap to the tester one, where an inductor or capacitor is mounted,
you can also use this to trim filter designs for best performance, see how different caps in parallel behave (parallel resonance)
the two 5dB attenuators each side of the DUT, is to keep the NA / SA-TG tester in good match,
and to feed the test area with a resistive load from both sides,
else you create resonance problems with the cable length, different cables would then create different results,
this methode is much better :-)
this PCB is flat to over 3GHz. i also design RF stuff, so i need to see how my parts perform.

[mawyatt]

There was some question earlier in this thread as to the frequency capability of the SMD fixture.  I found a manual for the HP 16034E version: https://www.keysight.com/us/en/assets/9018-01396/user-manuals/9018-01396.pdf?success=true

The spec says max 40 MHz, but on page 9, figure 1-5 shows the error vs. frequency; 25% error at 40 MHz!!

I suspect the low-cost eBay version without the shorting bars can't do as well.

Frankly wouldn't consider a 25% error specification a measurement at all, more like a "wing it" attempt

The fixtures by Tonghui (TH26008B) are specified to 120MHz, although not sure I would put much faith in a measurement at 40MHz much less 120MHz with these either. Of course the eBay clones have no specifications, but the construction is similar to the TH26008B, so infer as you wish.

If you look at the construction of these fixtures, experience dictates that achieving accurate and repeatable measurements at frequencies like 40 or 120MHz is questionable, specs or not we wouldn't rely on these fixtures at these frequencies which are better served with a VNA or Impedance Analyzer with proper fixtures, connectors and cables to support higher frequency component measurements.

Anyway, our LCR meter (TH2830) only supports 100KHz , so that's where we are interested in accurate and repeatable measurements with this LCR meter at this time, and these fixtures serve this frequency range well. 

Best,

[oz2cpu]

NEW REPAIRED VIDEO HERE :
https://youtu.be/y79nOd8GLWI
I am so sorry the first one contained a few missing pictures, i used a bad video editor,
now it is repaired, and a new video is uploaded,
with this design you can measure impedance of parts, caps, inductors, filter performance,
up to what ever frequency your spectrum / network analyzer can handle
EDIT : this call for a new seperate thread :
https://www.eevblog.com/forum/projects/component-tester-board-for-sa-na-impedance-caps-inductors-filters/

[mawyatt]

Those are nice test PCBs.

Where did you get those, or did you design yourself?

Best,

[oz2cpu]

yes my design, all you have to do email me, as ask for the gerber set,
bom is included, then order at jlc,
my email is my username at gmail dot com
NEW thread for this.. please jump here, so we dont jam up the KS34465 / TH2830 thread
all files are now shared for free, just goto thread and pick it up..
https://www.eevblog.com/forum/projects/component-tester-board-for-sa-na-impedance-caps-inductors-filters/