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work.
.hat
Why?
Relax. You don't know what you are talking about, and it's painfully obvious. Don't go to the trouble of reminding us about this - it wastes bandwidth and makes you look silly.
-- Bill Sloman, Sydney
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You seem to have stopped paying attention in your chemistry class at about the same point that John Larkin did. Your "water" resistors are filled with salty water.
-- Bill Sloman, Sydney
work.
That depends on all of the materials used. Consider that that transmitter was built in 1952, and designed for a 50 year life when it didn't have any modern materials available. Also consider that some stations waited till the alarm shut their transmitter down, which could take many years. They were more worried about electrolysis than actual conductivity, because any gas bubbles would cause cavitation in the system. Each output tube required 20 GPM flow, so any impurities were soon in the flow. Back then equipment wasn't designed to cost, and no one tried to see if they could push components past their specifications. The only real flaw in that transmitter design was an uncased mica coupling capacitor that would fail from silver migration over time. Some of these were on mountain tops and could only be reached by a helicopter or bulldozer most of the year.
I didn't see any time limit stated, or the actual application.
in
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Hey that's cool. Would someone sell me a saltwater resistor? (Price ~$1 each) It'd be nice to show that it has the same noise as a metal resistor.
George H.
on in
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Top posting? Too many insulating beers? With salt water resistors I'd always be a bit worried about the processes going on at the electrodes.Warburg impedances can be disconcerting.
-- Bill Sloman, Sydney
n
This isn't trace element analysis. The 0.1uM concentration of hydrogen and hydroxyl ions you get in pure water at room temperature would be embarrassingly high for a trace element ion.
n a
gh
Water is rarely stagnant - convection is pretty much inevitable, and because water is less viscous than pretty much every oil, it convects faster, and it's higher heat capacity shifts more heat per unit volume. It's also got a relatively high thermal conductivity at 0.591 W/m/K which is about a factor of four higher than paraffin oil - 0.15
- and more than twice that of paraffin wax - 0.25.
A good - heavily loaded - potting compound should do better than stagnant water, but only if it actually does fill the volume involved. You've got to evacuate the volume you want to fill and de-air the potting compound before you let it into the - evacuated - volume. Water does have a conveniently low viscosity.
Farnell does silicone potting compounds with a thermal conductivity of
0.9 W/m/K which isn't all that much better than waterThere's an epoxy which does appreciablyt better at 1.25 W/m/k, but it's not cheap.
-- Bill Sloman, Sydney
Pure water at 25C has a resistivity of 18.2 megohm-centimetre, and ordinary DI water faucets for washing things in fabs runs about 1 Mohm-cm. Your gizmo was probably reading ohm-meters.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
work.
Could be. I haven't seen one of those meters in 23+ years, and never in operation. the transmitter had benn powered down for three years when I was hired to move it & rebuild it. They ran out of money before it was fired up again.
Have you seen what that does to paint? God only knows what it does to FR4 and component encapsulants longterm.
--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)
"Having the promise of intoxication, without actually delivering" (Garrison Keillor)
--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)
dot 5 is paint safe, it's a different formulation, mostly silicone.
-- ?? 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
I'm working on cooling the heat sinks on an electric car project.
We are considering DOT5 brake fluid, but I also talked to
3M. They have a line called "Novec" and we may use their 7500. It's not cheap but is available in small quantities..Call them up and see what they recommend for your project.
3M Engineered Fluids is the name you want.-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
What i did (before test of PCB) is use 0.020 Getek, did a "pour" around each part for a heatsink, and a rectangle on the back as added heatsink. Each PCB has 168 zeners, a test at 1.4mA (about 25W) yields about
150mW/zener which has a max rating of 225mw "On FR - 5 board using recommended solder pad layout"; the PDF showing _only_ pads for the SOT-23. At a max 1mA use, i have a lot of elbowroom if i had used their "layout"; so i am guessing at least a factor of two for "still" air.I thought of water, but it is too easily contaminated with ions to make it practical except for use in a controlled lab-type environment.
This project is for hobby use; re-build Victoreen Corotron(TM) HV regulators used in some TVs,so cost is a definite factor.
It is a bitch to get electrical specs for any oil, and in some cases hard to get the boiling point as well (flash point seems easy). The FR3 seems to be better than the "plain" mineral oils electrically, boiling point and thermal. But there is an indication of many mineral oils,and then the possibility of using silicone oil.
Sigh, choices....with so little data to help.
How about the burp?
I take it that Shell Diala AX is an insulating oil? This is typical; zero electrical info; those ASTMs not in the MSDS because they do not care about anything not related to "safety". Yes, it does seem that it is an oil for use like i need, but zero info makes it useless. Fortunately, there is a _different_ data sheet pointing to unavailable D877 and D1816. At least,the numbers are larger than what the stress is going to be..
Oh, it is WORSE than that..the six inches is the vertical spacing; there will only be about 0.11 (max?) spacing from the edge of a centered PCB and the inside of the cylinder. Crude representation (not to scale): +----------+ | | cylinder wall | | | +------+ | | | | | | | | | | | | | PCBs inside | | | | | | | | | | | | | +------+ | | | | | +----------+
Well, i _is_ silicone oil; no electrical specs tho.. And i see that it has an additive - the coloring, which could mess it up..
I have always considered the so-called high thermal conductivity epoxies to be excellent thermal insulators; just slightly less than the "standard" ones. And i have yet to see electrical and thermal specs (together) for any of them..
OOPS! Thanks!!!
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