Note that if you change the dielectric in the probe, especially to a liquid, you may no longer be able to compensate it properly.
The higher dielectric constant will increase the stray capacitances. Best, -John ================ > On 9/22/11 10:34 AM, NeonJohn wrote: >> >> >> On 09/21/2011 04:57 AM, David C. Partridge wrote: >>> Howsabout HFC-236fa - very similar properties to R114 but not banned. >> >>>> Tektronix used a Freon in their 40 KV High Voltage probes. The Vapor >>>> pressure of some of those compounds is low at 70F, but they do have to >>>> be sealed. >> >> I use several of the Tek probes in my work (and of course am too cheap >> to buy the newer solid dielectric ones). When my freon ran out, I >> searched around for a replacement fluid and found ordinary butane >> straight from the Ronsonol can to be equal to or maybe even better than >> the original freon. >> > > Yes.. most hydrocarbons make a fine dielectric (viz. transformer oil). > To a certain extent, density is key, which is why the halogenated ones > are nice (F or C are more massive than H). The other thing is that > those halogens are electronegative which tends to suppress breakdown > (why SF6 is great.. not only is it really dense, but it's also non > flammable AND it's got fluorine in it) > > The halogenated ones are preferred in some cases because you can get > other vapor pressures and/or they don't burn. > > There is, of course, a whole class of nice dielectric fluids based on > halogenating double ring structures: PCBs. They're really inert, great > dielectric strength, immiscible with contaminants (no dissolved water, > which ruins dielectric properties). The problem is that there's an > unavoidable carcinogenic contaminant (dioxin-like PCBs and PCDFs). And, > because they ARE so resistant to breakdown, they persist forever, and, > unfortunately, are fat soluble and taken up by wildlife. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
