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Accurately measuring 1000pF and 100pF capacitors, to calibrate 4276A?

 

I've recently been tweaking my 4276A LCZ meter, and I am now at the point of needing 100pF and 1000pF capacitor standards.
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All the rest of the things are easy, I can measure resistors etc to sufficient digits, but the capacitors I'm less sure about.
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Does anyone have a good suggestion on how to measure capacitors accurately, assuming I have a full complement of test gear, but no reliable direct capacitance measurement gear beyond my 34461A multimeter in capacitance mode or my Der EE DE-5000 LCR meter? (I also have a 4263B LCR meter, but it is unknown regarding calibration and adjustment, and will have to remain so until I find a copy of the adjustment software, or reverse engineer it myself...)
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The 4276A calls for 100pF and 1000pF for adjustment procedures, and 1pF, 10pF, 100pF and 1000pF for performance verification, all calibrated to 0.01% accuracy at 1kHz and within 0.1% of their nominal values.
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I have made a bunch of 4-wire kelvin BNC adapter PCB's that attach directly to the instrument's BNC connectors, which work excellently for the open, short, and resistance values, so I can easily use them for the capacitors too.
Maybe polystyrene or mica are a reasonable choice?
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Any tips and help would be greatly appreciated.
Thanks!
Jared
 

Capacitance standards from General Radio are readily available at places like eBay.
Barry - N4BUQ

I've recently been tweaking my 4276A LCZ meter, and I am now at the point of needing 100pF and 1000pF capacitor standards.
?
All the rest of the things are easy, I can measure resistors etc to sufficient digits, but the capacitors I'm less sure about.
?
?
Does anyone have a good suggestion on how to measure capacitors accurately, assuming I have a full complement of test gear, but no reliable direct capacitance measurement gear beyond my 34461A multimeter in capacitance mode or my Der EE DE-5000 LCR meter? (I also have a 4263B LCR meter, but it is unknown regarding calibration and adjustment, and will have to remain so until I find a copy of the adjustment software, or reverse engineer it myself...)
?
The 4276A calls for 100pF and 1000pF for adjustment procedures, and 1pF, 10pF, 100pF and 1000pF for performance verification, all calibrated to 0.01% accuracy at 1kHz and within 0.1% of their nominal values.
?
I have made a bunch of 4-wire kelvin BNC adapter PCB's that attach directly to the instrument's BNC connectors, which work excellently for the open, short, and resistance values, so I can easily use them for the capacitors too.
Maybe polystyrene or mica are a reasonable choice?
?
?
Any tips and help would be greatly appreciated.
Thanks!
Jared
 

On 2/23/25 07:19, Jared Cabot via groups.io wrote:
Maybe polystyrene or mica are a reasonable choice?
Yes GR used polystyrene for cap standards. Can you borrow some GR gear to use as a reference to put a good
value number on some stable caps to use in your lab?

If not I have an extra GR 722D that includes 100 pF and 1000 pF in its range you can buy.

But, you're in Nippon, right?
 

On 2/23/25 07:30, n4buq wrote:
Capacitance standards from General Radio are readily available at places like eBay.
Yes, besides the variable 722D, there are fixed caps also. Those can weigh just 8 oz and 4 inches long so more shippable to Nippon.
 

Yep, I'm in Japan, so shipping is a consideration.. I don't have access to any standards here, besides what might pop up on Yahoo Auctions or the like.
 

A General Radio 1422D dual range variable would meet the specification. Needs the calbration chart though. The earlier 722D would be OK if calibrated and used at same temperature.
Not many units neet this specification. A pair of IET SCAs would do but they are not cheap. chaeapest would be to make up something as close as can with PC caps and get it measured. That's the difficult part. Most labs can't measure 100pF to 0.01%.
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Robert.
 

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If you need accurate measurements, I do have an Andeen-Hagerling 2500E which can measure C @1kHz to better than 5ppm and 8 digits resolution even at 10pF.? I rarely get it calibrated but its still the best on the market.
If you decide on what you're going to use as a standard, I'd be glad to measure it for you if you send your standard to me.
Richard

From: [email protected] <[email protected]> on behalf of Robert G8RPI via groups.io <robert8rpi@...>
Sent: Monday, February 24, 2025 2:28 AM
To: [email protected] <[email protected]>
Subject: Re: [HP-Agilent-Keysight-equipment] Accurately measuring 1000pF and 100pF capacitors, to calibrate 4276A?
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A General Radio 1422D dual range variable would meet the specification. Needs the calbration chart though. The earlier 722D would be OK if calibrated and used at same temperature.
Not many units neet this specification. A pair of IET SCAs would do but they are not cheap. chaeapest would be to make up something as close as can with PC caps and get it measured. That's the difficult part. Most labs can't measure 100pF to 0.01%.
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Robert.
 

I use a Boonton 76-3A precision decade capacitor for my calibration checks. I originally picked it up for calibration of an old Boonton 72BD meter (0.001 to 2000 pF capacitance range) but it now also serves as a good calibration check on a few HP units that I have. It has capacitance selection from 1 to 1221 pF in 1-2-3-5 x1, x10 & x100 ranges. Accuracy is 0.1% ±0.001 pF. The connections are made through special BNC(M) connectors without outer bayonet shell. But the unit can occasionally can be found in used condition with the Boonton output connector adapter to normal BNC(F) interface or you can make your own.

They sometimes come up pretty inexpensive on ePay amidst the real price gougers.

Greg
 

Both your 4276a and 4263b can measure ESR. So you may take the Henry Parsons Hall way, which he did at general radio with the digibridges:
First he calibrates the measurement-frequency deviation.
Secound he uses calibrated resistors and no capacitors for calibration.
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For your case: Check the oscillator frequency for drift.
Then take your calibration resistors and measure them with your 34461a. Now measure and tweak your 100pF and 1000pF calibation capacitors until your calibrations resistors measure the same values on the 4276a as on the 34461a.
Build from relative new (post year 2000) high voltage foil or Y2 capacitors - they have very low D, but D is never nagative.
Check with your 4263b and DER-EE 5000 - both with short and open calibration.
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By the way: my 4274a/4275a did not drift out of spec in the mid ranges, for me f > 1 MHz ranges are hard to check . Maybe the 4276a behaves the same, if you didn't tweek it. My 4263b drifted less then 1%, but more then the 4274a, if i remember correct. But all are not in the class of the genrad 1689 which has the most simple design and calibration procedure and like the 4274a no special parts.
(the 4274a/4275a are a repair nightmare compared to the digibridges, but have the better user interface).
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Well, I just picked up an Arco SS-32 Precision Standard Capacitor Set for the equivalent of about $75 all up, so that's a start. It has some missing values and a number of doubled up values too (maybe it is a set built up from values laying around rather than a 'complete set'), but the price was good anyway. Once I get it in my hands, I can see how each standard is constructed, and once I get my gear calibrated, I can complete the set with my own DIY capacitors.
It seems to have become the Electrocube ss-32 at some point, so at least parts are still available... Stated at 0.1 - 0.5%, so sort-of getting close to what I need, closer than I was yesterday anyway...
https://www.electrocube.com/pages/ds-pfc-precision-film-capacitors-and-standards-data-sheets
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My set doesn't have a 1000pF cap, but it does have a 100pF cap, so I'm now halfway there sort of, just need to get these caps all measured and such.
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@Richard Parrish, where abouts are you located?
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Thanks all for the info so far! Greatly appreciated. :)
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Jared
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