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