Homemade milligram/microgram scale

[Rhodium]

https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/scale.html

[Country_Fuck]

Well, son of a bitch, will ya look at that! Thanks Rhodium. For those who like to be really frugal those cheese boards are available around Christmas time in gift packs that are full of cheese, summer sausage and marmalade.
Son of a bitch, will ya look at that!

[catastrophe]

Hey Rhodium, this must be some of that 'important' information you've got on that second drive, huh?  

[Rhodium]

Yup, something like that. But it all needs the proper editing before I put it on my page, as the perfectionist I am.

[stormwind]

Well, that is definitely the best homemade balance design this swim has ever seen - and old old electrical meters are a dime a dozen in pawnshops too. take it apart and no one knows what the damn thing is. swim loves it!
"I'd take seed from Columbia and Mexico... an I'd just plant it up the holler down Copper head Road"

[obituary]

Rhodium the credit may not be yours for the idea, but that is a hell of a awesome writeup there.  frugal indeed!

[Bozakium]

Excellent,excellent,now that's the kind of science I like! Keep up the good work Rhod!
       Bz138

[meme]

"Although he may be an austere professional to his clients, I know him to be quite the free spirit who spends time in the business world only so he can make enough money to indulge his true passion - amateur science"

Man, that's great, and so is this write up.  I posted this at the Lycaeum a few days ago.  After reading countless reports of people trying to eye 2ct7 (whatever), this is most surely needeed.  Lives should be saved.
Today is opposites day.  Everything I say, I mean the opposite.

[Ghost_Of_BT]

Just out of curiousity, have any of you made this thing yet? It looks awsome.

[naturalblonde]

GREAT STUFF! This is one of the best postings I've seen.

Anyone have any idea how to get uGram calibration weights??

The source mentioned in the paper doesn't seem to be selling calibration weights anymore.

I was thinking about cutting squares of paper, aluminum foil, PTFE, or whatever, and begging someone in an analytical lab to weigh my little squares of paper/plastic.

Other ideas how to calibrate? (preferably OTC without involving a university or analytical lab)

uber-Blonde

[Ghost_Of_BT]

Using a good balence, weigh a small weight that the balence can acurately measure, cut the weight into a buch of pieces, use the average weight of the pieces. So say you have a 20mg piece of paper. Cut the paper up into 20 pieces. Take readings on your new scale  of each of those pieces. The average weight is exactly 1mg.

[Ghost_Of_BT]

Yesterday I made a very nice and easy to make balance that can take acurate measurements down to a few milligrams. Not as good as Rhodium's, but still good. Take a smooth block of wood and using a saw, cut a half-inch deep line across it. Mount a rectangular razor blade on the block using epoxy (sharp end facing upward and parallel with the surface of the block). make a small circular dish from aluminum foil and attach it to one end of a thin strip of aluminum sheet metal (two feet should be good enough to measure mg) using epoxy. You lay this strip across the razor and slowly slid it forward and backwards until you line the razor up as close as you can to the center of weight. You calibrate it by making lines across the top surface of the strip directly above the mounted razor and number these lines with a sharp marker (this is obviously a pain in the ass, so it is best to use this scale to to hit just a few values your aiming for).

[scarmani]

A good additional resource for anyone seriously interested in making this scale is this follow-up article:

http://www.sciam.com/2000/1000issue/1000amsci.html

It describes adding microprocessor control and some other enhancements (still inexpensive) which simplify measurement, increase sensitivity(!), allow weights to be continuously monitored and help with temperature fluctuations.
Those innocent eyes slit my soul up like a razor.

[darkxst]

SWIG was contemplating makin one of there little gadgets.. but DAMN those ol' analog galvanometers r hard to find these days.    guess it time to trek around some more porn shops,
the world is falling over..... watch out!!

[darkxst]

Other ideas how to calibrate? (preferably OTC without involving a university or analytical lab)

hows about coins? ordinary old OTC change. in SWIGs neck of the forest, the information on the weights and contents of all the coins is readily available. jus need 2 dig up some newer ones!!.. but then again they not really easy to cut up ay..

the world is falling over..... beeware!!

[darkxst]

A good additional resource for anyone seriously interested in making this scale is this follow-up article:

http://www.sciam.com/2000/1000issue/1000amsci.html

 

geez that is a nice ref.some interesting ideas in there;
 using pulse width modulation to increase sensitivity..
 and a current mirror to increase stability and keep the current(in the coil) constant regardless of the temp of coil

SWIG might whip 2gether something with a PIC microprocessor.
as soon as a decent galvanometer can b loc8d.

the world is falling over.....   beeware!!

[Rhodium]

Buy high-quality silver wire from a goldsmith, it comes in exceptional purity (meaning that the density is right at the 107.9 g/mol spot), and the wire is also always of a certain known diameter. As you know the density and the diameter (and hence the "bottom area") of the thread, it is easy to calculate how long bits of it you should cut to achieve 1, 2, 5, 10 and 25mg weights for your calibration.

[yellium]

Oxidation of the wire isn't a problem?

(Otherwise, great idea)

[Rhodium]

When the wire is brand new from the goldsmith, it won't be oxidized, and you should of course never touch it with your bare hands or store it in open air.

The biggest problem with silver is the formation of black silver sulfide on the surface, but it should not increase the weight noticeably, at least not compared to the weight difference caused by greasy fingers if they would be handled with bare hands. Use a forceps.

[darkxst]

or maybe as a substiture for silver wire, abee could try Nichrome wire. 
-------------------------------------------
Nicrome80:    %80 nickel + %20 chromium.
               size 28B&S (0.315mm)
                resistance 13.77ohm/m
-------------------------------------------
it is cheap as, and easily available...
just need to work out its density, and maybe dble check the
diameter, with a micrometer...



the world is falling over.....   beeware!!