Re: fluorocarbon for a tektronix p6015 hv probe .....
Herr Zapp, Mon Nov 15 2010, 08:07AM

Patrick -

("fluorocarbon", "Tektronix")

You're looking for Freon 114, also known as refrigerant R114, Halon 242, or dichlorotetrafluroethane.

Unfortunately for owners of Tek P6015 HV probes, this refrigerant was banned as a potential ozone-depleting CFC.

Dichlorotetrafluroethane has a boiling point of around 40 deg F, and a vapor pressure of only around 30 PSI (that's why the housing of the P6015 could be made of plastic).

Without the CFC dielectric fill, the probe is only rated for 13kV.

I've heard of others trying to use silicone oils, etc as a dielectric instead of the impossible-to-get R114, but never saw any real data on results.

Herr Zapp

Re: fluorocarbon for a tektronix p6015 hv probe .....
Steve Conner, Mon Nov 15 2010, 10:03AM

Try to get hold of Terry Fritz, he had a few P6015s and about 10 cans of the Freon stuff last time I looked.

If you refill the probe with oil, then the box needs readjusted. This is NOT a trivial job, there are about a dozen trimmers in it, and there's no guarantee that their range will be enough to cover the increased capacitance of oil.

Tek's own newer version of the P6015 is filled with silicone oil, as far as I know.

Do you have access to SF6 at college? 30psi of SF6 would probably work great... It's seemingly even worse of a greenhouse gas than Freon, but it's not actually banned yet. Then again, you might have the opposite problem if SF6 turns out to have a lower dielectric constant than Freon vapour.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Adam Munich, Mon Nov 15 2010, 11:50AM

?

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Mon Nov 15 2010, 03:26PM

is the old probe only filled with vapour instead of liquid insulant, hence the 30psi/sf6 remark?

Re: fluorocarbon for a tektronix p6015 hv probe .....
Steve Conner, Mon Nov 15 2010, 04:00PM

Ah no, my bad, it's the liquid. See this thread on Pupman.


Terry says mineral oil is "close enough", the box has enough range to calibrate it.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Mon Nov 15 2010, 09:41PM


does anyone know what is inside the p6015? a schematic would be nice, i have only seen a simple mechanical diagram which shows a single 100M resistor and a dielectric cone.

i presume R134a for my car wont work....?

Re: fluorocarbon for a tektronix p6015 hv probe .....
Herr Zapp, Mon Nov 15 2010, 10:11PM

Patrick -

Inside the probe housing is only a single long resistor.

The probe housing is supposed to be filled with Freon 114 vapor, but the only way to know that it's at the correct internal pressure is to have a small amount of refrigerant liquid visible inside the probe. The vapor pressure of Freon 114 is about 30 psi (or 2 atm). As long as there's still free liquid Freon present in the housing, you know that you have the correct internal pressure

If I remember, the original liquid fill volume was around 2-3 tablespoons, enough to reach the bottom end of the resistor when the probe was oriented vertically, point down. The original Tek can of Freon held enough for multiple refills, but over a period of years the Freon would slowly leak out of the can valve.

The vapor pressure of R134A at "room temperature" is quite a bit higher than R114, so filling a probe with R134A might yield a grenade-type structural failure of the housing. NOT RECOMMENDED!!

Attached is an old scan of the original Tek manual that provides the "refilling" instructions.

Tek also offered a nearly identical probe (P6013) that didn't require any Freon dielectric, but I think it was only rated for 12KV.

Herr Zapp
]tektronix_p6015_hv_probe_manual.pdf[/file]

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Tue Nov 16 2010, 03:25AM

ok probe explosions are bad.

and the freon is just vapor insulant? yes? @30psi

and a single resistor with compensation is not what i really want anyway.

dielectric gas:


breakdown per identity/atm....
Air @1 atm (14.7psi) ~ 1-3kv/mm
R114 @ 2 atm (28psi) = 6.44kV/mm
R134A/R12 @ 6.1 atm (90psi) = 17kV/mm !

as Herr Zapp warns I believe 90psi would burst the P6015 with possible lethality.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Steve Conner, Tue Nov 16 2010, 10:49AM

I think the "dielectric cone" is supposed to provide distributed capacitance to compensate the resistor's stray capacitances. It's not perfect, but knowing Tek it'll be cleverer than it looks.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Wed Nov 17 2010, 12:36AM

I have not been able to find a conact for Terry Fritz yet, does he have his own website now that someone else does the pupman site?

Re: fluorocarbon for a tektronix p6015 hv probe .....
Sulaiman, Wed Nov 17 2010, 01:13PM

For my P6015 I have tried a couple of dielectrics,
I am currently using Butane (lighter refil gas) .... YES , I know it could be flammable BUT
I put a lot in (1cm liquid) and let it boil off to about 5mm,
the cylinder by that point should have very little oxygen left,
then I seal it. .....so far so good, and it's cheap & easily obtainable.

Without dielectric I flashed it over at about 20 kV, with butane I haven't flashed it over yet.

If anyone has a really good alternative I too would like to know.

Re: fluorocarbon for a tektronix p6015 hv probe .....
teravolt, Wed Nov 17 2010, 08:14PM

I have 3 probes with the same problems I think they will hold off 13k with out freon and 20k with. I have also herd of silicon oil working to 20kv but I am not shure of the dialectric constant of freon and silicon oil if they are the same no adjustment may be nesisary.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Wed Nov 17 2010, 08:40PM

i think the risk of explosion is remote, the risk of flash fire no greater then the HV itself.

hmmm butane, i will look that up. im looking in the Merck chemical index and CRC handbook it looks like butane does have low pressure, with dielectric strength greater then air, but good numbers are hard to quote, need to do more searching.

EDIT: butane vapor pressure = 2.4 atm. (17% higher pressure then the tek specified dielectic)

since Sulaiman hasnt lost any fingers, or gained pressure burst flak in his gut, Butane may be a acceptable solution. I find it hard to think up anything better. TY to Sulaiman.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Herr Zapp, Thu Nov 18 2010, 01:21AM

Sulaiman -

You mentioned that youi experienced a "flashover" in your P6015 probe at around 20KV when used without any Freon fill.

By flashover, do you mean a surface flashover across the 100M resistor?

Here is a link to an old Tek paper on oscilloscope probe design, including a schematic of the compensator box used with the P6015 probe. I wasn't aware that the cable from probe to compensator box used a special resistance wire inner conductor.

Herr Zapp

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Thu Nov 18 2010, 06:58AM

i saw this too before, but if i have to goto the trouble of finding a qualified person to recieve it, and pay 49.95$ then i want something better then a pre 1970 rusted out s**t can thats probaly leaky/empty. wisconsin is bannig even R134A! without certification.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Proud Mary, Thu Nov 18 2010, 09:42AM

Does the dielectric constant of the insulating medium not matter?

Re: fluorocarbon for a tektronix p6015 hv probe .....
Steve Conner, Thu Nov 18 2010, 01:38PM

Proud Mary: As long as the dielectric constant is not too different to the original Freon, the adjusters in the compensating box can be twiddled to get the probe's square wave response good again.

Butane has a dielectric constant of 1.73-something according to Wikipedia.

I told Sulaiman's idea to the other guys here in the lab and they all cracked up laughing. But the more I think about it, the more it seems brilliant in a warped way. Maybe butane vapour can become the poor man's SF6, and we'll see a butane insulated QCWDRSSTC spewing flames from every point of the compass.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Thu Nov 18 2010, 03:09PM

i cant remember if freon-12 is flammable or not, ill look this up after class.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Adam Munich, Thu Nov 18 2010, 08:30PM

It is not.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Bored Chemist, Thu Nov 18 2010, 08:53PM

Re: fluorocarbon for a tektronix p6015 hv probe .....
Martin King, Thu Nov 18 2010, 09:35PM


I'd go with brilliant, as long as the probe body can handle the pressure and there are no significant leaks then it's no worse than a butane filled lighter or soldering iron. Even if there was a small amount of air still in there it wouldn't be an issue, the LEL and UEL of butane is between (approx) 2% and 8.5% of gas in air so you'd need a lot of air and very little gas inside the probe for there to be a problem.

Martin.

Re: fluorocarbon for a tektronix p6015 hv probe .....
teravolt, Thu Nov 18 2010, 10:54PM

butane might be a resonable substute but I don't think you can have any air mixed with it it would have to be in a liquid form or you run the posibility of detonation and I wouldn't recomend opening all my lighters and poring butain all over. there must be a better insulator that is safe. maby minreral oil.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Thu Nov 18 2010, 11:40PM

yes, upon further review, my conclusion is the same

Re: fluorocarbon for a tektronix p6015 hv probe .....
Herr Zapp, Fri Nov 19 2010, 12:11AM

Still, one part of my brain just says "Butane??!! You'll look like a moron if things somehow go wrong".

It looks like many of the chlorofluorocarbon refrigerants have (or had) dielectric constants around 2.0.

Both mineral and silicone oils also have DCs or around 2.0.

Here's a pretty comprehensive list of DCs, excepting refrigerants:
M

Herr Zapp

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Fri Nov 19 2010, 02:43AM

yes for the CFC's around 1.8~1.9,
for silicone i get many sources qouting 2.2-2.9,
for mineral oil i get sources saying ~2.1
for butane it seems 1.7-1.8 is credable.

if i recall terry fritz and/or others have said that when mineral fluid is used that the comp box had adustments near END OF TRAVEL! so , therefore i would not want to go much above DC=2.1 (mineral oil)

however, remember for human purposes mineral oils mole whieght and properties are somewhat constrained, with electrical/machine mineral oil is a broad class of oils which have wide variance. for this reason i would like to know if others have used mineral from the supermarket/pharmacy. i presume Vitamin E, perfume, other additives would be unwanted for hv use.

on an unrelated note at STP cocaine's DC is 3.1 @ 1Mhz

Re: fluorocarbon for a tektronix p6015 hv probe .....
klugesmith, Mon Nov 22 2010, 01:42AM

All this talk about dielectric constants -- it looks like people are quoting the values for -liquids-.
No worries about running out of compensation range when the chamber is filled with vapor
at 3 atmospheres -- e_r probably never exceeds 1.1.
(The part which exceeds unity can be scaled by the vapor/liquid density ratio.)

[edit] Not sure about 6015's, but ordinary scope probe compensation must be adjusted every time you move the probe to a different oscilloscope with different input capacitance. What do we use as a clean square-wave compensation source for a 1000:1 probe?

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Mon Nov 22 2010, 06:12AM

yes.

for vapors dielectric breakdown is the great concern, DC is secondary at best.
for liquids DC is the concern since breakdown is almost always sufficient of liquid insulants.

anything more then 2.5 atm may cause explosive/bursting the p6015 case.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Wed Nov 24 2010, 06:18AM

I have just contacted Terry Fritz, via a hot-streamer mirror site.
will post if he returns my email.

Re: fluorocarbon for a tektronix p6015 hv probe .....
testtest, Sat Nov 27 2010, 09:50PM


I have the schematic and ower's manual if you have not found the info on the net yet. Could post a scan if needed.
I also heard that there were two types of dividing resistors used in these probes and that a different dielectric could possible dissolve the protective coating on the early resistor.
Best bet was oil but I could not get the hf trimming in range. Now I do not dare cleaning it since it still works well at the lower voltage.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Adam Munich, Sat Nov 27 2010, 09:57PM

I think the butane is a good idea. Today, just to see what would happen I put the wires from a BBQ igniter into a jar and filled it with butane. I powered up the igniter and guess what I saw? Sparks. Just sparks, no explosions or flames.

There was an article on hackaday a while back where someone recharged his air conditioner with propane. It worked well, and nothing went kaboom.

Re: fluorocarbon for a tektronix p6015 hv probe .....
testtest, Sat Nov 27 2010, 11:01PM

someone recharged his air conditioner with propane. It worked well, and nothing went kaboom.

----------------------------------------- ---------------------------------------
It would work but if there is a leak isnt propane heavier than air? I remember in Toronto when a propane tank was stored on a balcony in a highrise appartment building. Took the whole balconey out and broke windows in the building across the street. Just because it works does not mean its safe. Look at your car with the fuel pump electric motor in the tank and cooled by the fuel. No oxygen is fine but can you garantee it at all times...?? "Feel lucky punk" No offense ment by the way, just a film reference...
Cheers

Re: fluorocarbon for a tektronix p6015 hv probe .....
Adam Munich, Sat Nov 27 2010, 11:06PM

Well then spend a few hundred more dollars on a tank of sulfur hexafluoride. It's patrick's choice after all.

Re: fluorocarbon for a tektronix p6015 hv probe .....
testtest, Sat Nov 27 2010, 11:50PM

I wonder if a car aircon $25 can in a recharge kit would do the job after all?

Re: fluorocarbon for a tektronix p6015 hv probe .....
Adam Munich, Sun Nov 28 2010, 12:00AM

Actually I just remembered that canned air is tetrafluoroethane, or R-134a. You could possibly substitute that, and for 5 bux a can it's worth a shot.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Sun Nov 28 2010, 02:24AM

remember r134a has a way higher vapour pressure, 90 psi instead of 28 psi ! it might burst !

Re: fluorocarbon for a tektronix p6015 hv probe .....
Adam Munich, Sun Nov 28 2010, 02:31AM

Hmm, butane it is then?

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Sun Nov 28 2010, 02:47AM

yeah i think so, also i cant contact Terry Fritz, i just get an "e-mail wont go through warning."

Re: fluorocarbon for a tektronix p6015 hv probe .....
Sulaiman, Sun Nov 28 2010, 10:53AM

P6015 pdf
]tektronix_p6015_3-90_small.pdf[/file]

The flashover appeared to occur on the inside surface of the plastic
from the central probe to the outside metal sleeve/shield, with no dielectric whilst 'scoping eht flyback pulses. No track marks left!
High dv/dt goes where it pleases!

Many moons now and the butane does not look to have escaped.
Opened and checked - the rubber seal is not damaged/corroded.


VERY IMPORTANT - I am using butane at home for my hobby use.
I am not recomending it for others and certainly not in a 'legal liabilities' situation. I certainly could not do this at my workplace..

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Sun Nov 28 2010, 05:59PM

yep!


yeah i did not think otherwise!



and SF6 is difficult to use, plus $$$ so i dont know where and how i would get it.

Re: fluorocarbon for a tektronix p6015 hv probe .....
hvguy, Mon Nov 29 2010, 09:13AM

I have two p6015s I filled with mineral oil and re-compensated about 5 years ago. I routinely use them up to ~3MHz (sine and square waveforms) with no problems. I'm currently using one to monitor pulse cap switching at 16kv and have no flash over issues. If you have a dry probe give mineral oil a shot, you can always drain it if you're not happy with the results....

Re: fluorocarbon for a tektronix p6015 hv probe .....
testtest, Wed Dec 01 2010, 04:37AM


I was unable to compensate mine when I tried using dielectric oil a few years ago. Unfortunately I dont remember what kind but it was meant for high voltage use. Perhaps too high a dielectric constant?

The mineral oil you used is the (non perfumed, I hope) that you can get in a pharmacy?

Re: fluorocarbon for a tektronix p6015 hv probe .....
teravolt, Thu Dec 02 2010, 04:25AM

Hi Patrick, I happen to talk to a pulse power engineer at work and if you have any diala oil that would work and you would have to readjust the probe. the dialectric constant is about 2

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Thu Dec 02 2010, 04:33AM

thanks TeraVolt, i dont use the real oil, i usually just snag food oil, but thanks anyway, i bought HV resistors which will be here in 2 days, ill make my own probe, or i will buy the p0615A soon.

Re: fluorocarbon for a tektronix p6015 hv probe .....
Sulaiman, Thu Dec 02 2010, 08:00PM

If you can find a p6015(a) cheaply go fo it,
you would spend many many hours to get similar stability, accuracy, bandwidth, low capacitance and shielding - oh, and insulation too ;)

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Fri Dec 03 2010, 02:32AM

ok well ill compare them and see... ive been told that the NorthStar probes are even better, and they have fewer adjustments nthen the tektronics, but ill snag a p6015 if i can.

Re: fluorocarbon for a tektronix p6015 hv probe .....
teravolt, Sat Dec 04 2010, 04:59AM

hi Patrick those NorthStar probes are expensive but nice. maby you are aproching this wrong what kind mesurement are you trying to make. do you want a scope tool

Re: fluorocarbon for a tektronix p6015 hv probe .....
Patrick, Sat Dec 04 2010, 09:49AM

yeah ive got qoutes from $1840 to $2400 for the pvm series ones.

and i need a o-scope probe w/oscope... i need to see 2 and 4 channels of 4 different signal and HV traces, so i can see arrival time and phase type relations @ sine waves and square waves at about 3000Hz - 40kHz, @20-40kV for my DeSeversky lifters graduate project.

Re: fluorocarbon for a tektronix p6015 hv probe .....
hvguy, Mon Dec 06 2010, 05:11AM

richnormand,

Yes, garden variety drug store mineral oil, no perfumes or colors. I recall being very near the end of the range on one of the pots...