Search found 1005 matches

by Rich Feldman
Sun Dec 09, 2018 8:37 pm
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: Neon sign transformer power: a new look
Replies: 12
Views: 2878

Re: Neon sign transformer power: a new look

Last night I measured NST primary current. It's a key design requirement for high-voltage isolating transformers to go upstream of the NST's. Same setup as before, except with a true-RMS ammeter in series with primary. Primary voltage was set to nominal and many different resistive loads were measur...
by Rich Feldman
Tue Nov 27, 2018 8:12 am
Forum: Advanced Technical Discussion Area
Topic: Harbor Freight freebie meters
Replies: 12
Views: 986

Re: Harbor Freight freebie meters

Respectfully beg to differ, sir, on one small detail. >> Accurate current measurement is solely dependent on the resistance of the wire leads to the meter. Accurate voltage measurement has nothing to due with the leads at all but the input impedance of the internals of the meter, itself. How can lea...
by Rich Feldman
Fri Nov 23, 2018 8:39 pm
Forum: New User Chat Area
Topic: Negative Polarity Power Source?
Replies: 11
Views: 1199

Re: Negative Polarity Power Source?

Hey Bern, it's good to see you helping out at fusor.net.
Done any work lately with your own fusor?
by Rich Feldman
Tue Nov 20, 2018 6:30 pm
Forum: Advanced Technical Discussion Area
Topic: Harbor Freight freebie meters
Replies: 12
Views: 986

Re: Harbor Freight freebie meters

Yup, 1 megohm input impedance is typical for those cheap meters. Many of that class are also distinguished by having an hFE measuring range, and associated 8-terminal transistor socket. Their input impedance is even worse in AC volts mode, as I found out a couple months ago, and presented in Neon Si...
by Rich Feldman
Mon Nov 19, 2018 8:17 pm
Forum: Announcements and Site Administration Topics
Topic: Finished PhD, now a postdoc at MIT
Replies: 8
Views: 785

Re: Finished PhD, now a postdoc at MIT

Congratulations, Andrew.
Not only a PhD, but you have a job! In your field!
Good luck.
-Rich
by Rich Feldman
Sun Nov 18, 2018 10:22 pm
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: Neon sign transformer power: a new look
Replies: 12
Views: 2878

Re: Neon sign transformer power: a new look

So far so good. With nominal primary voltage, I got: 425 watts into a matched resistor. 222 watts with 10 R's in series (14.4 kV x 15.5 mA). Still thinking of using 2 of these NST's in series for fusion someday. 159 watts into a string of 25 Christmas lights, last year converted from parallel to ser...
by Rich Feldman
Sun Nov 18, 2018 4:21 am
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: Neon sign transformer power: a new look
Replies: 12
Views: 2878

Re: Neon sign transformer power: a new look

The Altoids-box mA meter has been assembled, calibrated, and put into service. Tonight I measured the first of my 15060 NST's, with primary voltages of 60, 120, and 140, and loads of short, luminous tube, 1R, 2R, 4R, 8R, and open circuit. Next time out, will crank it up to 277 (the nominal primary v...
by Rich Feldman
Tue Nov 13, 2018 6:57 pm
Forum: New User Chat Area
Topic: Crystal synthesis inside a vacuum?
Replies: 3
Views: 319

Re: Crystal synthesis inside a vacuum?

At the opposite extreme, tons of synthetic quartz crystals are grown at pressures up to 1500 bar (21,000 psi), from alkaline aqueous solutions at temperatures around 380 °C, mimicking the natural geological method. qtz4.jpg That's barely above critical temperature, but almost 7 times critical pressu...
by Rich Feldman
Thu Nov 01, 2018 1:57 am
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: BCS detectors for neutrons
Replies: 0
Views: 227

BCS detectors for neutrons

Some online reading, inspired by Kai's project, turned up reports of Boron Coated Straws. Anybody here seen or heard of them? The developers hope to profit in the homeland security market, among others, in this era of limited helium-3 supplies. bcs1.JPG Very briefly, we have: [*]Extra narrow proport...
by Rich Feldman
Mon Oct 29, 2018 5:51 am
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Neutron Detector and Moderator Test
Replies: 9
Views: 1149

Re: Neutron Detector and Moderator Test

Nice work. Thanks for sharing. Is the black mark on the edge of your work surface (was going to say, your counter) a reference for putting detector in the same place each time? For people new to neutron physics, how about demonstrating some other geometries? Instead of surrounding the detector with ...