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fluorocarbon for a tektronix p6015 hv probe .....

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Patrick

Mon Nov 15 2010, 07:42AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

If I can snag an old p6015 hv probe, but it would be the one that came with the can of dielectric fluid... my question is where can i get this kind of fluid? Techtronix doesnt seem to offer it anywhere anymore...

Is there a way to fill the probe with common oil like peanut or silicone, and just re-calibrate that little box? Is this a common problem?

I cant afford the 600-1000$ for the new ones, being a college student.

Herr Zapp

Mon Nov 15 2010, 08:07AM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

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

Steve Conner

Mon Nov 15 2010, 10:03AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

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.

Adam Munich

Mon Nov 15 2010, 11:50AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Patrick

Mon Nov 15 2010, 03:26PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

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

Steve Conner

Mon Nov 15 2010, 04:00PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

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.

Patrick

Mon Nov 15 2010, 09:41PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Herr Zapp wrote ...

Patrick -

("fluorocarbon", "Tektronix")

sorry, the peppermint schnapps impaired my ability to spell.

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....?

Herr Zapp

Mon Nov 15 2010, 10:11PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

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]

Patrick

Tue Nov 16 2010, 03:25AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

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.

Steve Conner

Tue Nov 16 2010, 10:49AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

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.

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