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Mastech MS5308 LCR meter with ESR measurement - on discount at the moment
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PA4TIM:
I have done a lot of VNA  meaurements on capacitors. But also using RF-IV like you do ( but I can do phase too) i can sweep from 1KHz to 1500 MHz. Also have several bridges including the famous GR1620.

It is long told the ESR is at it lowest point at SRF, but like your plot of a new cap hows, it is not.
Indeed the ESR can never be higher as Z and is equal to Z at resonance, but that does not have to be the lowest value.

About decreasing frequency and increasing ESR, your plots show what I mean, it is not lineair, it falls off quick from allmost DC to about 20 Khz and then it goes more slow.


Calibrated good fixture

Calibrated but bad fixture for the same cap

BUT, do you use a real calibrated fixture for these sweeps ?
And has your calibrationkit known parameters ?
I use a calibration that involves open, short, load and a series of knoen capacitors so allmost all strayes are compensated for. The VNA then uses 12 term error correction. I use special low Z fixtures for ESR and high Z fixtures for things like measuring fF ( and customtraces to transform S21 into R + jX.

What instrument you use, the plots look very good, similar to what I get ( how the Rs and Z behaves)

Problem with real good ( mica, MKP ect) caps is to find the SRF because, deembeded and clibrated right it can be several hundred MHz. Then calculate ESL from that and make a corrected jX sweep. If calibration goes wrong you are only looking at the SRF of the setup.
The Electrician:

--- Quote from: PA4TIM on January 11, 2013, 01:43:14 am ---I have done a lot of VNA  meaurements on capacitors. But also using RF-IV like you do ( but I can do phase too) i can sweep from 1KHz to 1500 MHz. Also have several bridges including the famous GR1620.
--- End quote ---

I started another thread in what seems to be a more appropriate forum:

https://www.eevblog.com/forum/projects/capacitor-measurements-on-an-impedance-analyzer/

The analyzer I used to produce the plots can do phase, and every other parameter you can imagine.  See the first attached image for a screen shot of the available parameters.  I mainly want to show the behavior of electrolytics and there doesn't seem to be much point in attempting to measure parameters into the GHz range.  It's really hard to fixture electrolytics to a GHz VNA.


--- Quote from: PA4TIM on January 11, 2013, 01:43:14 am ---It is long told the ESR is at it lowest point at SRF, but like your plot of a new cap hows, it is not.
Indeed the ESR can never be higher as Z and is equal to Z at resonance, but that does not have to be the lowest value.

About decreasing frequency and increasing ESR, your plots show what I mean, it is not lineair, it falls off quick from allmost DC to about 20 Khz and then it goes more slow.
--- End quote ---

Your VNA plots are using a linear frequency axis.  This is typical of VNAs, although some can be set to display on a logarithmic frequency axis.  Most plots of ESR and impedance that can be found on manufacturer's web sites have a logarithmic frequency axis.  I find that it's difficult to draw conclusions about how fast ESR is falling off at low frequencies when the frequency axis is linear.  The second and third attached images show a sweep of an electrolytic with both a log sweep and a linear sweep.  You can see that it's difficult to see in much detail what's happening at the lowest frequencies.  Can you change your plots to have a logarithmic frequency axis?


--- Quote from: PA4TIM on January 11, 2013, 01:43:14 am ---BUT, do you use a real calibrated fixture for these sweeps ?
And has your calibrationkit known parameters ?
I use a calibration that involves open, short, load and a series of knoen capacitors so allmost all strayes are compensated for. The VNA then uses 12 term error correction. I use special low Z fixtures for ESR and high Z fixtures for things like measuring fF ( and customtraces to transform S21 into R + jX.

--- End quote ---

In the other thread I give a link to the impedance analyzer I'm using.  These relatively low frequency analyzers (5 MHz highest frequency, compared to several GHz typically for a VNA) only need to calibrate with an open and a short.  The fixture is connected to the front panel's 4 terminals and the short and open are applied to the fixture's measuring points; it is this style of fixture: http://www.home.agilent.com/en/pd-1000000479%3Aepsg%3Apro-pn-16047E/test-fixture-40-hz-to-110-mhz?nid=-34051.536880747.00&cc=US&lc=eng

The open is just the absence of anything in the fixture, and the short is a small shorting bar that comes with the fixture.




--- Quote from: PA4TIM on January 11, 2013, 01:43:14 am ---What instrument you use, the plots look very good, similar to what I get ( how the Rs and Z behaves)

Problem with real good ( mica, MKP ect) caps is to find the SRF because, deembeded and clibrated right it can be several hundred MHz. Then calculate ESL from that and make a corrected jX sweep. If calibration goes wrong you are only looking at the SRF of the setup.

--- End quote ---

As I said, I'm mainly concerned with electrolytics, and even for the non-electrolytics that I may show, the frequency range I'm using is reasonably similar to what can be measured by the low-cost ESR and LCR meters that are often discussed on the forum.
PA4TIM:
My VNAs are able to make plots from 1KHz but using some special settings it can go down to  10 Hz. Several of my bridges do 10Hz to 100 KHz too. On VNA does 100 KHz to 110 MHz, the RF-IV does 1 KHz to 100 MHz. My home made ESR meter does 10 to 100 KHz.

If I use a vna for electrolitics i most times sweep 1 KHz to 100 KHz, or 1 to 1000 KHz or whatever I want.
I also use a special fixture that sets 50 Ohm in series with the DUT for measuring ESR ( but not using a RF-IV testhead)

It can do log, lineair , custom, smith, polar and radar plots. But that does not matter, optical it looks different but its all the same. It is al based on the waveparameters and then converted to scattering parameters and thnigs like Rs, phase, Xc and all the other things you like ( from RL to group delay)

The magnitude at frequency X does not change wen changing the axis, only the position on the X-ax. If you want to look at the non-linear decrease of ESR vs Frequency it makes only sense to use a linear sweep.

But i have not invented this and It is not really worh the discussion, you have the gear to test it yourself, and you can read it in every good book about capacitors ( or general radio experimeters, app notes from lcr\bridge\vna\Impedance meter manufacturers, literature from cap manufactures or books like analog SEEcrets)

This is not to offend you, just a few little minor points. I Think your comments in discusions about cas are very good. And it is nice to know I'm not the only one mad enough to do a lot of capacitor resource.
mrubbert:
MS5308 died directly when connected power adapter, total dead and wont fire up with battery either. Brand new 30min test.

Did ofcourse check the chines poweradaptor DC 12v fore Ac-rippel and more. It have that 100kHz nosie shown in youtube review.

Just wonder if it happend to other owners ?
jwrtiger:
Sorry to hear about the failure to your LCR Tester.  I am still playing around with that power supply for fun and I have pretty much created a schematic diagram of the circuit.  The output after the transformer is just a half-wave rectified, capacitor filtered circuit.  It is still working when I connect it to my LCR Tester but of course the error is still there in the resistance modes.  I tried an $8.00 (USD) linear power supply from Jameco  and initially it seems to work... need to check it out completely.  I still plan to make my own supply in the next few weeks.
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