[ASK] Standard Capacitor ....

[HighVoltage]

Thanks, that makes sense.

First test passed, showing 10.004 nF at 1kHz on my PM6306

[BravoV]

Congratz on the score  , really envy you. 

[SeanB]

Mica sheet does vary from mine to mine, and from actual mined area in that mine as well, due to contaminants in the material. There is a little town here around 800km away from me called Mica, which I was very familiar with, mostly through passing through it in a cutting near the mine, which has a lovely cut through the mineral formation that gives it it's name. The best capacitors are made from selected cuts from the mines, and command a premium, as they are very pure. Cheaper sheets are made from other product, and I have a sheet of that that is used to cut new waveguide covers for microwave ovens from, or you can use it to make formers to hold resistance wire to make heaters or high power resistors.

[GregDunn]

OK, while people are viewing this thread... I need an accurate 10nF capacitor to use as a sanity check for meter calibration (it's specifically the value called for in the manual).  The best I can find on commercial sites is 0.5% accuracy.  Does anyone have a recommendation for where I could find a more accurate one for a somewhat reasonable price?  Trying to hunt down more accurate caps on evilBay returns a lot of useless hits...

[HighVoltage]

A quick search on ebay reveals:

GENERAL RADIO 0.01 uf TYPE 505-L STANDARD CAPACITOR
US $ 19.99
I am not sure how good they are.

[GregDunn]

That looks pretty good, actually - apparently I was using the wrong search criteria,  I may buy a couple of those caps.

[The Electrician]

OK, while people are viewing this thread... I need an accurate 10nF capacitor to use as a sanity check for meter calibration (it's specifically the value called for in the manual).  The best I can find on commercial sites is 0.5% accuracy.  Does anyone have a recommendation for where I could find a more accurate one for a somewhat reasonable price?  Trying to hunt down more accurate caps on evilBay returns a lot of useless hits...

Would a capacitor somewhat larger than 10 nF, but accurately known do the job?  For example, would an accurately known 11.2nF capacitor serve your need?

[GregDunn]

It probably would be OK.  I assume they picked .01µF just to have a standard value for the calibration setting - it may have worked out .09, .11 or something else and they decided the linearity curve would be close enough with that as the set point.

This is not a NIST calibration by any means.     Someone pointed me to a .01 GenRad standard cap (without cert) for a reasonable $20, so that's the neighborhood I'm living in right now.   

[Henrik_V]

Here are some 1nF 1404 standard cap cans (not genuine GR) I dumpster dived..
They are all prone to wisker, thats why 
See second pic
A future project will be a rework. Polish and gold plate the plates (and standoffs) , remove the tin wisker plant ground , refill with dry N.
Decapsulation was done with a torch, first tried 20 min with a hot air gun .... 
If it doesn't work out the first time I still have some more .. 

[doktor pyta]

was it from IET Labs ?
now I see. Quadtech.

[Conrad Hoffman]

Wow, wish I had a dumpster like that! I thought the plates were supposed to be invar, which shouldn't have a whisker issue. Or is that just the big reference caps and the ones in their bridges?

[Henrik_V]

HI Conrad,  you are right, the plates are INVAR and don't show wisker.
The the housing (can) and the mounting base are tin plated and are prone to wisker. We had short cuts to the feedthrough and we found wisker parts flying around in the can.. 
I regulary check my caps isolation resistances.. and I had wiskers (one plate some kOhm to housing) even with genuine GR 1404s ,  applied a 400V pulse to burn the free.. got luck the value didn't change (recal rigth after) 

The INVAR plates look horrible ... OK, due to my rough torch desoldering they migth get smoked a little    but surface and edges of the genuine GR part look better.
however we want to give it a try and polish (and gold plate) them ..
Two units are open .. I bet after remouting , N refill , and tempering (this time without a torch ) it will cost me one unit for our Cap-lab people 
And I need a way to get rid of the tin plating.....

[HighVoltage]

  applied a 400V pulse to burn the free.. got luck the value didn't change (recal rigth after) 

Wow, that is some kind of brute force on a metrology device.
What a great dumpster you have.

Very interesting with the whiskers.
Do all original GR 1404s have whisker issues or did they fix that may be at a later state by using different methods with the can?

[Henrik_V]

  applied a 400V pulse to burn the free.. got luck the value didn't change (recal rigth after) 

Wow, that is some kind of brute force on a metrology device.
What a great dumpster you have.

Very interesting with the whiskers.
Do all original GR 1404s have whisker issues or did they fix that may be at a later state by using different methods with the can?

All ? I don't know. They all (AFAIK) have the tin plated cans .. maybe small variances in the solder composition matter ??
A lot of information on whisker is collected here: https://nepp.nasa.gov/whisker/

I wasn't shure what will happen with my GR 1404 .. Its rated for higher voltage  ... what could I loose?  It performes fine since that 'burn out'    ~6 years ago.

[branadic]

The INVAR plates look horrible ... OK, due to my rough torch desoldering they migth get smoked a little    but surface and edges of the genuine GR part look better.
however we want to give it a try and polish (and gold plate) them ..
Two units are open .. I bet after remouting , N refill , and tempering (this time without a torch ) it will cost me one unit for our Cap-lab people 
And I need a way to get rid of the tin plating.....

That's gonna be a long journey. First you need to strip the tin, then you need to galvanically add nickel and gold. Maybe you can give PVD a try, but I'm not sure how good that works with the aspect ratios of the can. But why a gold finish? Wouldn't nickel be good enough?

-branadic-

[Henrik_V]

The INVAR plates look horrible ... OK, due to my rough torch desoldering they migth get smoked a little    but surface and edges of the genuine GR part look better.
however we want to give it a try and polish (and gold plate) them ..
Two units are open .. I bet after remouting , N refill , and tempering (this time without a torch ) it will cost me one unit for our Cap-lab people 
And I need a way to get rid of the tin plating.....

That's gonna be a long journey. First you need to strip the tin, then you need to galvanically add nickel and gold. Maybe you can give PVD a try, but I'm not sure how good that works with the aspect ratios of the can. But why a gold finish? Wouldn't nickel be good enough?

-branadic-

The INVAR plates to be polished and plated are not tin plated   Our galvanisation lab will know how to treat them and what bounding layers migth be needed.

Removing the tin from the can and mounting block?  Cover the feedthroughs and cap mounting holes and try sandblasting  ?? 
One nasa paper reports a coating with ?? ... let's  see   maybe end of next year

[gamalot]

I got this from Japan.

[Conrad Hoffman]

FWIW, invar is miserable to plate and I wouldn't do it. It's known for poor adhesion even with various intermediate layers. Plating can be  prone to bubbles and that would change the capacitance. I'd polish and leave it at that. Not sure if it can be electropolished, but that might worth a look.

[seebeck]

The GR1404 is a better standard than general capacitor standards . GR was bought by the IET Lab (https://www.ietlabs.com/) in 2000 and to continue to produce and market LCR standards. I shared the A2LA certificated report for IETLab company as attached file.
BTW, the ESI（also an old brand company for standard resistor such as SR104 ）,it was bought by the IET Lab in 2006. The other part as meter axies for ESI was bought by TEGAM . TEGAM is a very well-know company for the microwave standard area such as power sensor calibration products , it associated ESI、Keithley、Tektronix、Weinschel...
The best physical capacitor standard is AH10/11 from Andeen-Hagerling around the world!

[iisak]

before I got the metrology-/voltnut-/ppm-virus, I used this kind of capacitors (see att. pic. 1)
I have them since early to mid 80s and they are still very stable and usefull for hobbiest references (but by no means Standard capacitors)
If I would search for replacements I would look for Glass Capacitors and good NPO (like this blue ones in pic. 2)

Same here, although mine are mostly silver micas.

Bought few of this NPO recently, going to use it as reference cap, with tempco of 30ppm and virtually doesn't age as Kemet claimed. 

What made me interested at this cap is apart from its a NPO, it has relatively big capacitance (100nF) compared to most silver micas I have.

Have these KEMET GoldMax capacitors been stable? Have you measured them over these years?

I would be interested to have a set of stable capacitors from 10 pF to 10 nF. I understood that MICA or some good ceramic would be good. Some 10 ppm/year would be nice. I wonder would that be realistic.

I have found these, for example:

Cornell Dubilier  10 pF MICA (see Digikey part 338-1068-ND)
KEMET GoldMax 10 pF caramic COG (see Digikey part C315C100GAG5TA-ND)

[cdev]

A standard to me most of all demands stability. Meaning physical stability, so a standard capacitor wouldnt necessarily handle thousands of volts, but it would be built like a rock in a way so it would not be prone to change due to any external factor, like air pressure or humidity. So it might be sealed? I dont know. I'm not an expert on this at all.

The music from the video is nice and suggests precision well, mentally.

Is there anything worth seeing in Boonton, NJ?

I know they made innovative RF measurement equipment, a long time ago.