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Electronic Scales and balances


#1

G’day; I’d just like to interpose a little word (2c worth) about
the accuracy of electronic scales. Now my wife and I have been
used to weighing to 0.0001grams ever since we left school, and both
of us agree (for a change!) that the modern ‘accurate’ scales are
nothing like as accurate and reliable as the old fashioned
laboratory balances and scales. It is our finding that one must
never trust the last figure. For instance just before we retired
all the four decimal point ‘swing’ balances in the University
Chemistry Department where we worked were replaced by the modern
electronic type. The fourth figure was rubbish. And so it went
for the 3, 2, and 1 places on other less accurate balances. So
what should have been 10.53grams on a 200gram balance/scale would
be only 10 .5 grams, plus-or-minus-a-bit! So my point is that
when you are weighing precious gems or metals, be wary of that last
decimal. Incidentally, most of today’s balances/scales are really
spring balances with electronics that measure a gap, though a few
are based on electronic strain gauges. Do check 'em with a real
weighing machine based on gravity and with accurate weights. Oh
yes, my wife and I were senior technicians, not ‘real’ academics!

Cheers,
/
/ /
/ /
/ /___| \ @John_Burgess2
(______ )
At sunny Nelson NZ


#2

Dear John and wife… I too have gone back to the weight and
balance scale as my gold seems to come out BETTER when weighed on
the balance scale then on the electronic one… don’t know why but
gave it up as I hated the difference in my gold… I also like that
little number at the end… My husband goes nuts when he only gets
the one number also… Makes a difference… any way fun to hear
your thoughts… calgang


#3

Hi Calgang:

I, too, measure my gold by a balance scale. I do this at school in
NYC. Where did you buy your balance scale. I now need one at my
home studio. All the scales I’ve seen in the catalogs seem to come
with Carats or Gram weights. I need Pennyweights (Dwts.) and Grains
(24 to a dwt.). Any help is much appreciated. Thanks.

Linda
@Red1Eagle


#4
    I too have gone back to the weight and balance scale as my
gold seems to come out BETTER when weighed on the balance scale
then on the electronic one.. don't know why but gave it up as I
hated the difference in my gold...

G’day’ ‘Calgang’; I can tell you how to calibrate your electronic
scales, to give you a more dependable accuracy but you’d need a
small fluid measure. You see, one millilitre (ml) of water at 20C
weighs one gram, so if you weighed a small container, then poured
into it from a good measuring cylinder - say - exactly 10 mls of
water, your scales should of course weigh the original weight plus
10 grams. This would not be completely accurate, as some of the
water would be left in the measure. Perhaps a better way would be
to weigh the measure then add water very carefully until the level
reads 10mls plus measure weight. Better still would be to use a
10ml pipette. You’d fill the pipette and then empty it to wet the
inner surface: refill the pipette, lower the water level carefully
to the mark, then allow it to empty into the weighing-vessel and
note the weight. You’d do this several times then take the mean.
However. I don’t know how practical this exercise might be for you,
but you might be able to borrow a 10 or 25 ml pipette from your
local school science dept? You will know, I expect, that 1 carat
equals 200 milligrams (mg) or 0.2grams. (near enough)

You might be a little interested to know that when I retired from
the University I was able to buy one of the despised 'swing’
balances and a set of weights in perfect order which they were
disposing of in favour of the “better” electronic ones. It weighs
up to 200grams to an accuracy of +/- 0.0001g - I paid NZ$10 for it!
So, because I am able to do my own scientific instrument
glassblowing (I did a course for a Science Technician’s exam 50
years ago) I made myself a set of Pyrex glass pipettes and
calibrated them by weighing water on the balance; filling the
pipette to a guessed value, reweighing the remaining water, marking
the level on the pipette on a sticky label, then repeating this
business until I got three marks in the same place for the given
volume. I even used a home-made thermostat bath to give me
distilled water at exactly 20C - and even made my own distilled
water!! So I finished up with pipettes known in the trade as
Certificated A Grade Instruments. Which are very expensive indeed.
Because it is a bit of a hassle to use my accurate balance for
odd things not needing great accuracy, I made a spring balance
weighing up to ten grams accurate to 0.05g. The weighing pans are
made from circles of kitchen foil, pressed (by one’s hand) around a
little wooden former - which I turned up on a home-made lathe.
(I’ve got a really good wood lathe now) The weighing pans are
made in a few seconds, and can be thrown away to avoid
contamination.

  I also like that little number at the end... My husband goes
nuts when he only gets the one number also.. 

On many modern electronic scales the last number flashes, or
oscillates between two or more values - which tells one at once
that the last figure cannot be relied upon. I don’t know of any
such scales which are accurate to better than 2% at any value.

Anyway, hope this rambling anecdote might be of some interest to
you. And by the way, Orchid seems to be having problems doesn’t
it? Cheers now,

   /\
 / /

/ /
/ /___| \ @John_Burgess2
(______ )
At sunny Nelson NZ in a lovely late autumn: summer won’t go!


#5

G’day John Burgess-

Top of the mornin’ to you, John and the rest of our southerly
friends- How about this for an easy calibrater for a scale. The US
nickle, 5 cent piece weighs 1 gram exactly, or 5 ct.s whichever you
perfer, and likely as not, you’ve got one on your person.(at least
we of the USofA). I personally use an el cheapo scale for most not
percise things or the old triple beam, and a good diamond scale for
anything else requiring precision. But John, please don’t start the
rumor that these scales are not accurate, you’ll have people
tossing and turning all through the night:^) A lot of money can be
riding on those points of a gram! The scales that we weigh stones
with are very accurate indeed, but only to .01’s (hundreds of a
gram), not .001’s(thousands of a gram) as you describe for
chemistry. I think that it has a lot to do with the operator, don’t
you? The a/c alone can make these scales fluctuate, they are so
sensitive, and hence the glass enclosures. They still don’t get
closer than hundreds. If it’s close enough for the diamond dealers,
it’s close enough for me! Best Regards- Rick


#6

simpler method of checking scale (at least in USA) get some new
money from the bank. One bill any denomination = 1 gram.

I would like to know about other countries

This is how racetracks, casinos etc. count money quick


#7

Hello Ricky and List,

Just happened to have a second-hand US nickel (5 cents piece) on
me and flipped it on the scale (without any prior polishment).
Result: 4.89 gram.

Ricky, you have any diamonds for sale ? I’m looking for a gram or
two :wink:

Best wishes

Jan J. Hansen
Copenhagen, Denmark


#8

Jesus Christ Jan, you’re absolutely right. I haven’t been getting
enough sleep lately. It’s the dollar bill that is one gram and the
nickle is 5 as you said. I’m dyslexic from time to time also-
Regards- Ricky Low