Greetings!

Please take a moment to introduce yourself in this forum and tell us about your interest. You must use your full real name. We do not allow the used of "handles" and pseudonyms on this site.
User avatar
Samuel Berman
Posts: 5
Joined: Tue Nov 14, 2017 5:55 am
Real name: Samuel Berman
Location: San Jose, California

Greetings!

Post by Samuel Berman » Tue Nov 14, 2017 6:14 am

Hello everyone! I am a 15 year old high school student. I am interested in Chemistry, Engineering, etc, but only recently decided to tackle building a Fusor. This project will probably be a long term thing for me and it will take me a while to get all the materials. I did some searching online and decided to join this forum because it looks like the best place to be for this sort of stuff. Anyway, so far I have a vacuum pump (cheap 1 stage, so may need a different one), a glass jar, and a gasket (neoprene, so probably not suitable either :(). I have a decent amount of experience with this stuff as I have been tinkering in my garage for years. Wish me luck!
"I just wanted an accessory!"

User avatar
Dennis P Brown
Posts: 1288
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: Greetings!

Post by Dennis P Brown » Tue Nov 14, 2017 10:15 am

Hello, and welcome. Both a single stage pump and a 'glass jar' are only useful for a plasma demo; a fusor requires a steel chamber or steel vacuum connector like a four-way cross ( 2.75 inch or larger.) The other requirements are in the FAQ's so, you can research those items. Good luck in scrounging for items! Maybe request that group and post your results, from time to time. Hint: Keep a close eye on ebay or attend a 'ham radio gear' or similar electronics flea market for a two stage pump that is being offered for little money - ditto for a cheap micron range gauge/display combo.

User avatar
Samuel Berman
Posts: 5
Joined: Tue Nov 14, 2017 5:55 am
Real name: Samuel Berman
Location: San Jose, California

Re: Greetings!

Post by Samuel Berman » Tue Nov 14, 2017 2:45 pm

Thanks! I forgot to mention, I have a thermocouple gauge on the way that I got from eBay for $30. Hopefully it works.
"I just wanted an accessory!"

Niels Geerits
Posts: 53
Joined: Tue Jun 13, 2017 10:25 pm
Real name: Niels Geerits

Re: Greetings!

Post by Niels Geerits » Wed Nov 15, 2017 2:39 pm

Welcome Samuel, depending on your TC and pump you may or may not measure something. Some TCs will work in the 5 Torr (such as the DV-4), others only start giving you a useful reading below the 100 micron range. I don't know if a single stage pump can get down below 100 microns. In addition some TCs require DC Input, while others take AC. Both require an amplifier at the output and the AC TCs also require a filter (this is the kind I have. Will post about it soon). Just some things to consider before you hook up your gauge to the pump.

User avatar
Samuel Berman
Posts: 5
Joined: Tue Nov 14, 2017 5:55 am
Real name: Samuel Berman
Location: San Jose, California

Re: Greetings!

Post by Samuel Berman » Wed Nov 15, 2017 3:18 pm

Well, the pump is rated for 5 microns but I doubt it will get near that since it's a $40 pump. I bought the gauge with the controller so I don't have to worry about that. The gauge on the controller goes to 1000 microns, so does that mean it will measure at that pressure?
"I just wanted an accessory!"

User avatar
Rich Feldman
Posts: 871
Joined: Mon Dec 21, 2009 11:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: Greetings!

Post by Rich Feldman » Wed Nov 15, 2017 3:40 pm

Welcome, Samuel. Give it a go with what you got! If your path is typical, you will soon learn about leak detection and abatement. You're ahead of most noobs, in ability to measure vacuum before you light things up electrically.

Can we see some pictures? I bet your gauge mark for 1000 microns is near the high-pressure end of the scale. Is there an "atmospheric pressure" mark a little bit higher than that, where the pointer goes when powered up with no vacuum, or rests with no power?

You'll have a wide-range pressure gauge to complement your TC sensor, as soon as you can look at plasma configurations inside the jar.
Your NST, HV feedthrough, and internal electrode don't need to be fancy, or even DC to begin with.

Re. Niels's comment about vacuum sensors, RIchard Hull often mentions types where the heated thermocouple directly drives an analog meter movement. Nothing super-sensitive about the meter -- it just has a coil wound for low voltage instead of low current. (Gas safety valves for pilot lights are held open by a solenoid using voltage from a single TC junction -- tens of mV.)
Last edited by Rich Feldman on Wed Nov 15, 2017 3:44 pm, edited 1 time in total.
Richard Feldman

User avatar
Dennis P Brown
Posts: 1288
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: Greetings!

Post by Dennis P Brown » Wed Nov 15, 2017 3:41 pm

This is the greetings section, so, best to move your questions to Chat section here after.

As to reading a 1000 microns accurately - well, depends but not really all that important. However, that range will tell you a lot about your $40 pump.

The key for any fusor gauge is the range from 3 to 20 microns since that is where most fusors operate. Likely your single stage pump will fail to get even to 100 microns. But, testing is your first step.

Niels Geerits
Posts: 53
Joined: Tue Jun 13, 2017 10:25 pm
Real name: Niels Geerits

Re: Greetings!

Post by Niels Geerits » Wed Nov 15, 2017 4:17 pm

Great that simplifies things! Didn't expect it would come with a controller at such a low price. The fact that your meter starts at 1000 Microns is good, probably goes down to something like 10 microns? If you hook it up to your pump correctly, you will probably get some reading, which will tell you if your pump is any good.

User avatar
Samuel Berman
Posts: 5
Joined: Tue Nov 14, 2017 5:55 am
Real name: Samuel Berman
Location: San Jose, California

Re: Greetings!

Post by Samuel Berman » Wed Nov 15, 2017 5:45 pm

Thanks for the info. Should I move this to the new user chat, or some other section?
"I just wanted an accessory!"

User avatar
Dennis P Brown
Posts: 1288
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: Greetings!

Post by Dennis P Brown » Thu Nov 16, 2017 12:08 am

The chat area is better unless you have a non-elementary question; then use the correct section.

Post Reply